— 3 Paleontographica MCZ LIBRARY A ME! tcana »» HARVARD UNIVERSITY NUMBER 57 JUNE 28, 1991 Revised taxonomic procedures and paleoecological applications for some North American Mississippian Fenestellidae and Polyporidae (Bryozoa) by Edward McKinley Snyder 1989 Winner of the Osgood Prize PALEONTOLOGICAL RESEARCH INSTITUTION Officers PIMP IDES NR E M o Soriano end HARRY A. LEFFINGWELL A 027 a o i S NA EM E UM CDM ME J. THOMAS DuTRO, JR. A ee ne ale CARET ORE Sa rare ce eee HENRY W. THEISEN O eiue Du Uu MU E pe VE Dn T JAMES C. SHOWACRE ATANT TIREASURERO.——— vs as ®t nd ROGER J. HOWLEY Ibrcinsano dc ae c EDU ee es e CU Oe PETER R. HOOVER ESCALERA ee HENRY W. THEISEN Trustees BRUCE M. BELL (to 6/30/93) EDWARD B. PICOU, JR. (to 6/30/92) CARLTON E. BRETT (to 6/30/92) JAMES C. SHOWACRE (to 6/30/93) J. THOMAS DuTRO, JR. (to 6/30/93) JAMES E. SORAUF (to 6/30/91) HARRY A. LEFFINGWELL (to 6/30/93) JOHN STEINMETZ (to 6/30/91) ROBERT M. LINSLEY (to 6/30/92) HENRY W. THEISEN (to 6/30/92) CATHRYN NEWTON (to 6/30/91) RAYMOND VAN HOUTTE (to 6/30/91) SAMUEL T. PEES (to 6/30/92) WILLIAM P. S. VENTRESS (to 6/30/93) A. D. WARREN, JR. (to 6/30/91) BULLETINS OF AMERICAN PALEONTOLOGY and PALAEONTOGRAPHICA AMERICANA PETRO ee ee aie EDITOR Reviewers for this issue A. HOROWITZ F. K. McKINNEY A list of titles in both series, and available numbers and volumes may be had on request. Volumes 1-23 of Bulletins of American Paleontology have been reprinted by Kraus Reprint Corporation, Route 100, Millwood, New York 10546 USA. Volume 1 of Palaeontographica Americana has been reprinted by Johnson Reprint Corporation, 111 Fifth Ave., New York, NY 10003 USA. Subscriptions to Bulletins of American Paleontology may be started at any time, by volume or year. Current price is US $45.00 per volume. Numbers of Palaeontographica Americana are priced individually, and are invoiced separately on request. for additional information, write or call: Paleontological Research Institution 1259 Trumansburg Road Ithaca, NY 14850 USA (607) 273-6623 Table 7.— Definition of zoecial and zoarial characters used in species descriptions. The numbers preceding characters are used as abbreviations for those characters in Tables 10-46. They are defined in numerical order in Table 8a. E = in external view; I = in internal view; use of the symbol > between these abbreviations indicates greater importance of the view abbreviated to the left. A. Zoarial character Lb EI: 283 29 34. 35: 43. branch width (WB).— Measured perpendicular to direction of branch growth (in plane of frond); measurements are not made near dissepiments or branch bifurcations; exhibits high coefficients of variation in most species due to secondary or lamellar thickening ofithe. branch: (see Text hes: 4A GA OB OAN 7 ered cee she REP mr I Me Ne Ae Oh ee aoa Be Eorl . distance between branch centers (DBC).— Measured between areas of branch bifurcation; has a high coefficient of variation among species (sce: Texteip- 6A). 2 ee RE er PME EA Eorl . dissepiment width (WD).—Measured parallel to direction of branch growth, in middle of dissepiment; has a high coefficient of variation due to:secondary skeletal thickening, (see Rexhes: 4A 6E TB) I ann a a a a E >I . length of fenestrule opening (LF).— Measured parallel to direction of colony growth between dissepiment edges; used by Elias and Condra (1957) as one of the primary diagnostic characters of Fenestella, but coefficients of variation calculated herein raise questions as to its significance; decreasing fenestrule length is associated with secondary dissepiment thickening, and ontogenetic change in fenestrule length is a colony response to environmental pressures (see Text-figs. 4A, 6C, 7B) ...............0. 20 cece eee eee Eorl . width of fenestrule opening (WF).— Measured perpendicular to growth axis between branch edges at maximum diameter of openings; moderately to highly variable due to correlation of decrease in fenestrule width with secondary branch thickening (see Text-fig. 4A) EorI . number of aperture openings per fenestrule length (AF).— Measured along one side of branch between dissepiment centers, counting complete apertures or those with greater than half of opening present in the interval between dissepiments; constant within most species, although some species have between two and four apertures per fenestrule, thus decreasing the usefulness of this character (see Text-hg. 4A) Co Ere A LM DERIT NP EORR E> 1 . diameter of nodes along obverse branch surface (DN).— Maximum node diameter; these features are highly symmetrical (see Text- fig AA) EET N ET EN RR ren NEN E>I . diameter of nodes on dissepiments (DND).— Measured on obverse dissepiment surface (see Text-fig. 4A) .................. E>I . distance between node centers along obverse branch surface (SNB).—Included in the original meshwork formula of Ulrich (1890) [see p. 18]; high coefficients of variation for this character limit its usefulness (see Text-fig. 4A) .......................... Eorl . width of keel (WK).— Measured perpendicular to direction of branch growth in plane of frond (see Text-fig. 4A) ............ Eorl . diameter of stylets on obverse surface (DSO).— Measured at maximum stylet diameter (see Text-fig. 4A) ................... EorI . spacing of stylets along obverse branch surface (SSO).— Highly variable for most species; moderately constant for a few (see Text- fig dA yn ae meii poe ce UL AE PTS HS o Lr eld Me dis EN RER ER HON Uri rey and O Eorl . diameter of macrostylets on reverse branch surface (RSL). — Measured at maximum macrostylet diameter; highly variable (see Text- BE: AB) a eet geet ay e SaaS ER o cae ere DUELO EE mine nee da y REM Eorl . diameter of microstylets on reverse branch surface (RSS).— Measured at maximum microstylet diameter (see Text-fig. 4B) ...E > I . spacing of macrostylets along reverse branch surface (SSL).— Measured between macrostylet centers; has an extremely high coefficient of Variation (See -Fexitg dB)" rey fox de tts ee es oe Ca ccc LAME E Far NRO gee E or I . Spacing of microstylets along reverse branch surface (SSS).— Measured between microstylet centers; both microstylet diameter and mierestylet:spacing have high coeficients of varaton (Sce Textne AB) m TE E>I . reticulate meshwork spacing parallel to direction of branch growth (LRM).— Measured between mesh centers; closely correlated to spacing and number of apertures along obverse surface; used in Hemitrypa (see Text-fig. SA, SB) ......................... Eorl . reticulate meshwork spacing perpendicular to direction of branch growth (WRM).— Measured between mesh centers; closely correlated to spacing and number of apertures along obverse surface; used in Hemitrypa (see Text-fig. SA, SB) ...................0.. Eorl spacing of whorls along central axis (WSC).—Measured between sites of maximum whorl expansion; corresponds to “number of volutions in 2 cm” of Ulrich (1890), but provides a more accurate determination of variability of the central axis of Archimedes; apparently strongly influenced by environment; used only in Archimedes (see Text-fig. 5C) ........00 000 cece eee ee EorI maximum diameter of central axis (DCA).— Measured perpendicular to direction of axis emplacement at maximum whorl diameter; used: only in. Archimedes (sce Texte Ci sn eL Sura t RENE END UR RN ESSET EN EI angle between distal end of axis and axial whorl (ACA).— An acute angle; high coefficient of variation probably reflects environmental mituence; used:only tm Archimedes: (see Tert ien IO ve punc TM Cc IE thickness of front-wall (obverse-wall) laminated layer (FW T). — Measured as thickness of laminated skeletal material between exterior side of obverse granular skeletal layer and outer edge of laminated skeleton on obverse exterior zoarial surface; shows pronounced increase with: ontogeny (seeslext-hgs-6BJ0DAI@ Pr vr. un ons p PER I thickness of reverse-wall laminated layer (RWT).— Measured as thickness of laminated skeletal material between exterior side of reverse granular skeletal layer and outer edge of laminated skeleton on reverse exterior zoarial surface; increases with ontogeny, producing. high coefiicients: of vanation (see Toxt ies OB OD IA IOTI A T I thickness of branch (YB). — Measured across branch in obverse-reverse direction; pronounced increase with ontogeny (see Text-figs. CASTA) ia a I NG LE le OE E EN UR ORE OCC ERO HERE EE CUM Tc I Table 7.— Continued. B. Zooecial features T: 8. No w — 33: 36. Syr 38. 392 40. 41. — 42. aperture length (AL).— Inside diameter of apertural opening, measured parallel to direction of branch growth; measured on exterior surface where possible, due to problems in defining aperture orientation in shallow tangential sections (see Text-figs. 4A, 6C, 7B) mu P E N A C E N E A EA A Rec E EE E ee NI eT Rd E >I aperture width (AW).—Inside diameter of apertural opening, measured perpendicular to direction of branch growth; apertures inclined into fenestrules are measured in their apertural planes; measured on exterior surface where possible, due to problems in defining aperture orientation in shallow tangential sections (see Text-figs: 4A; 66) occ o e E> 1 . distance between aperture centers along branch (ADB).— Measured between closest apertures parallel to direction of branch growth (see Text-hp..4A) our tonem e N segs SORT pee OR E M HU n IE E>I . distance between aperture centers across branch (A AB).— Measured between closest apertures across branch; direction of measurement is frequently diagonal to branch length and width; often has means similar to ABB (see below) and low coefficients of variation, probably reflecting symmetrical areal coverage of lophophore feeding zones (see Text-fig. 4A) ....................00.-005. E>I . distance between aperture centers between branches (ABB).— Measured between closest apertures between branches, across fenestrule opening or dissepiment; often has means similar to AAB (see above) and low coefficients of variation, probably reflecting symmetrical areal coverage of lophophoredeeaing zones (Secretari ae M PEE E>I . width of peristome (WP).—Measured at distal end of aperture; increases with colony ontogeny and can thicken to cap apertures on proximalend;otsthezzoarium (soe Ten nE <4 AN hc c Oise eR Stee o e MM TERES EorI . number of stylets surrounding aperture (SA).—Stylet number is very constant within a species, suggesting (where they are present, as they do not occur in all species) a possible function as tentacle guides for the polypide (see Text-fig. 4A) ................ EorI . diameter of stylets surrounding aperture (SAD).— Measured as maximum diameter of apertural stylets (see Text-figs. 4A, 6C) .... . ovicell length (OL). — Inside diameter of enlarged polymorph exterior opening, measured parallel to direction of branch growth (see Wextsfig- 4A) 3-5 teo e lv RUN EAE RAD vp c CER M rd E > I . ovicell width (OW).— Inside diameter of enlarged polymorph exterior opening, measured perpendicular to direction of branch growth; ovicells occur fairly rarely in most fenestrates, being most commonly found in Hemitrypa and polyporids (see Text-fig. 4A) .E > I . maximum width of ovicell in mid tangential view (WOT).— Used only where enlarged polymorph chamber alters inner dimension ot chamberwidth. Re TN A eee he eT eve Rar prt Me RO UE EE I . thickness of reverse-wall granular layer (TRW).—Measured across granular layer in longitudinal or transverse sectional view; granular skeletal material forms a complete lining of chambers in most fenestrates; has low coefficients of variation; much higher coefficients of variation are found in laminated skeletal characters; due to position of granular skeleton surrounding the zooecial chamber, granular skeletal material is.considered:to: be zooecial (see Textos OB 7A, 7O) rn ce mee eet ese E I thickness of chamber lateral-wall granular layer (TLW).— Measured in longitudinal view (see Text-figs. 6D, 7C) ............... I autozooecial chamber length (CL). — Maximum inside dimension of chamber measured subparallel to branch growth axis and parallel to long axis of chamber; measured in longitudinal view; may be taken between lateral chamber walls (Text-fig. 6) or between obverse and reverse chamber walls (Text-fig. 7); represents the maximum chamber length regardless of orientation of the measurement, although orientation must be included in the descriptive analysis; has great taxonomic and biologic significance (see Text-figs. 6D, MO LUE NT E yc RE Se En p ORES SPE E MM A E m ME E E. I autozooecial chamber depth (CD).—Inside diameter of chamber in longitudinal view, measured perpendicular to chamber length; measured only:invlongitudinalaviews(See exis OD 7, ©) eee c cr LU E EM I maximum chamber width (MAW).—Measured across the branch; measured in a median tangential section taken parallel to the zoarial obverse.surface (sce Text AES OCA IBI BU ee A er Lm A E ER I minimum chamber width (MIW)— Measured across the branch; measured in a median tangential section taken parallel to the zoarial obverse surface; used for chambers that are polygonal or ovate-truncate in this view, but excludes those that are triangular, square, orrectangular/(seeFextsfigs* GC 7B) eee ee o ore ML e E MM ER En vestibule depth (VD). — Measured perpendicular to plane of zoarial surface from outer edge of apertural opening to where vestibule opens into main chamber; measured in longitudinal section; the most variable of all chamber characters, due to increase in vestibule length as the obverse laminated skeletal material thickens (see Text-fips- 6D, 7O) <= cce ee Te tUe I chamber reverse-wall budding-angle (RA).— Measured at base of chamber, where lateral and reverse walls merge; measurement made from distal end of colony, in longitudinal view; represents angle of autozooecial chamber lateral-wall emplacement relative to direction of branch growth (typically an acute angle); has an extremely low coefficient of variation (see Text-figs. 6D, 7C) ..... I chamber lateral-wall budding-angle (LA). — Measured in transverse view, this is the angle between a line perpendicular to the plane of the obverse surface and a line from the center of the aperture, through the middle of the chamber toward the reverse wall and intersecting with the line perpendicular with the obverse suface (see Textes DATA) O a ET I Table 8a.— Outlines of species diagnoses and descriptions, and definitions of measurements and terminology (in italics) employed therein. Definitions are either absolute or relative; in relative definitions, arrows [>] separate terms that indicate points in continua. Comparators of size may be further subdivided by the use of the terms “lower-end,” “mid,” and “upper-end,” to indicate the bottom, middle, and top of the range, respectively. Abbreviations of measurements are explained in Table 8b. CV = coefficient of variation. Outline of the Diagnosis - - Zoarial characters A. relative robustness (delicate [fragile, zoaria frequently broken and small] — intermediate [moderate number of large zoaria present, resist breakage better than delicate forms] — robust [zoaria typically large, highly resistant to breakage]) B. mesh spacing (close [WF < WB] > intermediate [WF = WB] > open [WF > WB]) C. mesh uniformity (regular or irregular) D. secondary zoarial features (e.g., reticulate meshwork and central axis) . Branch characters . robustness (delicate [fragile, frequently crushed, thin width and depth] — intermediate [moderate preservation, width and depth inter- mediate] > robust [wide, thick, typically well-preserved]) . width (narrow [«0.30 mm] > intermediate [0.30-0.39 mm] > wide [750.39 mm]) . branch thickness (thin [<0.30 mm] ^ medium [0.30-0.39 mm] > thick [70.39 mm]) . proximodistal trace (e.g., straight, sinuous, broadly curved) . Shape in transverse cross-section (e.g., elliptical, ovate, circular, semicircular, rhombic, polygonal) . spacing (close [DBC < 2.0 x WB] > intermediate [DBC 2.0-2.5 x WB] > wide [DBC > 2.5 x WB]) 3. Dissepiments A. width (thin [<0.5 x WB] > intermediate [0.5-1.0 x WB] ^ wide [51.0 x WB]) B. length (short [WF « WB] > intermediate [WF = WB] > long [WF > WBJ]) C. placement (regular or irregular intervals) 4. Fenestrule A. size (small [length «0.4 mm; width «0.24 mm] > intermediate [length 0.4-0.9 mm; width 0.24—0.34 mm] > large [length >0.9 mm; width 70.34 mm]) B. shape (e.g., elliptical, ovate, rectangular, square, circular) C. uniformity of shape (regular or variable) . Autozooecial apertures A. relative size (small [length «0.09 mm; width «0.07 mm] > intermediate [length 0.09-0.15 mm; width 0.07-0.12 mm] > large [length 70.15 mm; width 70.12 mm]) B. shape (e.g., circular, ovate [includes direction of elongation], elliptical [includes direction of elongation]) C. peristomal characters (width, degree of development, and completeness) D. position of apertural stylets E. number of apertures per fenestrule length 6. Branch surface ornamentation and features; placement and positioning along obverse and reverse branch surfaces A. keel width (narrow [<0.05 mm] > intermediate [0.05-0.15 mm] > wide [70.15 mm]) B. nodes (small [«0.7 mm] > intermediate [0.07-0.12 mm] > large [70.12 mm]) 7. Autozooecial chambers A. relative size (small [length «0.20 mm; depth «0.10 mm; maximum width «0.10 mm; minimum width «0.07 mm] > intermediate [length 0.20-0.48 mm; depth 0.10-0.20 mm; maximum width 0.10-0.15 mm; minimum width 0.07-0.12 mm] > large [length 70.48 mm; depth 70.20 mm; maximum width 70.15 mm; minimum width >0.12 mm]) B. emplacement (monoserial, biserial, or in rows at and proximal to sites of branch bifurcation) C. chamber outline 1. near reverse wall (triangular, rectangular, square, ovate, elliptical, circular, parallelogram-shaped, or diamond-shaped) 2. at mid chamber (triangular, rectangular, square, ovate, elliptical, circular, parallelogram-shaped, or diamond-shaped) 3. near obverse surface (triangular, rectangular, square, ovate, elliptical, circular, parallelogram-shaped, diamond-shaped, or bilobate) . orientation of elongation location of aperture relative to chamber relative size of vestibules (if present) . degree of development of superior and/or inferior hemisepta (if present) . mean lateral-wall budding-angle (constant [CV < 10] or variable [CV > 10]) mean reverse-wall budding-angle (constant [CV < 10] or variable [CV > 10]) heterozooecia (if present, type and location on branch) N > "mugotm u Serommy The Paleontological Research Institution acknowledges with special thanks the contributions of the following individuals and institutions PATRONS ($1000 or more at the discretion of the contributor) JAMES E. ALLEN (1967) ROBERT C. HOERLE (1974-1977) AMERICAN OIL COMPANY (1976) RICHARD I. JOHNSON (1967, 1986) ATLANTIC RICHFIELD COMPANY (1978) J. M. MCDONALD FOUNDATION (1972, 1978) CHRISTINA L. BALK (1970, 1982, 1983) MoniL OIL CORPORATION (1977 TO DATE) Hans M. Bo zi (1984) SAMUEL T. PEEs (1981) RUTH G. Browne (1986) RICHARD E. Petit (1983) MR. & Mrs. KENNETH E. CASTER (1967) ROBERT A. PoHowsky (1982) CHEVRON OIL COMPANY (1978, 1982) TEXACO, INC. (1978, 1982, 1987) ExxoN COMPANY (1977 TO DATE) UNION OIL OF CALIFORNIA (1982 TO DATE) Lois S. FOGELSANGER (1966) UNITED STATES STEEL FOUNDATION (1976) GULF OIL CORPORATION (1978) CHARLES G. VENTRESS (1983 TO DATE) MERRILL W. Haas (1975) CHRISTINE C. WAKELEY (1976-1984) (continued overleaf) R. TUCKER ABBOTT JAMES E. ALLEN ELIZABETH A. BALCELLS-BALDWIN CHRISTINA L. BALK Bruce M. BELL ROBERT A. BLACK RICHARD S. BOARDMAN Hans BOLLI DAVID JOHN BOTTJER RUTH G. BROWNE J. DAvip BUKRY SyBIL B. BURGER LYLE D. CAMPBELL JoHN L. CARTER ANNELIESE S. 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CONTENTS Page y Abstract sec crs vindice er ee en ee TEE IR : Acknowledgments Sire ii apres ed ulii Na BEI MNT ADLER 5 Od ICON er ee CERE LLL i Mississippian Stratigraphy and Structural Geology of the Upper Mississippi Valley .................00 0.0 cece e Taxonomy of Meshwork Fenestrate Bryozoa 16 Goneri Taxonomie Divisions Ome BIYOZON ra a e UA REEL LLL LLL LLL LLL Summary and Critique of Previous Approaches to the Taxonomy of Meshwork Fenestelloidea ............s 0000 eee eens = Historical Review and Approach to Taxonomic Divisions within the Form Genus Fenestella Lonsdale ..................2-55- E Biological Significance of Zooecial Chamber Shape ..............-- IDEE ETE ELE LLLLLLLLLLLLLZL E Taxonomic Criteria for the Discrimination of Fenestellid and Polyporid Species... Systematic Paleontology "e 36 Taxonomic alt cid HANE ns RR ind di sea” pace etic AA oon i dte m Abore viaton oE Repository Institutions e ac or e TERI ERU UA tatio oe een t ecient et rad Systematics "E 40 Family a ee er RL ER A NA UAR ot MU QE, pa GenissRectifenestellaaMonoz OV aL ose d. AAA AR A AAA din : iret otia blu UON SPAREN ARN SHORE oc nite Ee p A roms N adessent Ad ista eaa ces vue 47 EI a Sse EL dae cg Oe aie eID aE ED PRE oe 49 Genus Laxifenestella Morozova, 1974 e pee na a ors A ONE NE init tin 50 a egent e RA cb told soit doit Pract tni = le bee er ee nd o coi E = Laxifenestella serratula (Ulrich, 1890) er cisco DN a a 58 a ah ee ee adi doas = DONO agen iyi o ee ee ee 2 Eu DUO Nina sittar NRI BSN tao ap es he cant eee ee A 65 a A N rene aia ta ps DES DESI KO due en a HABD ee eoque ci eese risen eadein gs 68 Exfenestella exigua (Ulrich, 1890) n E ee A ae 72 E rors sr ay TR een 2 IN hee Sic Cela ae a HIIS e eese iere ster oris S, id Qa IRAE Vil 79 Ree DM rela ea E SLIDE, Midis tata SR AE SE VINE SENSUM fa h M a sie pre nitur QUALI Us WA AT Lob S AME he ia Banastella biseriata (Ulrich, 1890) e o TOL EE ESL oo a M va f is Banastella FOR RRS ETE STALE TI A Pak VENEER QUA" NA AL We NN 88 RE HU Uo Dec rne pete tie ke RE a RR o OA ANE Be SA n Cubifenestella rudis (Ulrich, 1890) GeO on T i ASSE GE CBE RO IRR + E NDA A sn D OR UON ET A Mte RER A A ea SEELE ti UC SOT ea Ser 97 A cd a Mo eerie ns LUNG M 99 Apertostella Joramenmajor, A TE mid N READ CMMNÜE 101 A arire a NE aba a Tian ch ee ee sins era RE MAE 1 Hemitrytpa perstriata Ulrich, 1890 He er ess rath N sco quU EDUC VR 2i MEER AR VIE RERUM ARI: sense Front east taht irs tno ernennen MS eH EOM DUMP nn a Oe Yd cote sni oec V M CRAT re TU |< Sl nee ie tee OS al a css ce o ARATRI AM d YE A SEU rel certain o hrs abe San EEE MAL O02 BR 1i E Mage coder pee O Ee INR 124 A EN qe Archimedes owenanus (Hall, 1857b) FE renderers EUR hood sd M OU; Bor dieci ada Hom 130 PURO OD ESOL dA Ue CA ESO CA ee NS IS AS Rep are 133 BAL CHUMOR ESC EV Eh TAN eS Duet td nd Io a Ke Rin mpi UAE. cig iw alios Patty Poly gaudes Vae PESE. A un 136 ten nw A NE E RC RT DID uu cC MU UE 197 Ponesmaliasanectiludovici Prout, LSSI ae Hemp e 138 e O Ne 142 a erede EEE 144 A meum ES O Noir Tees eris itte 146 a o ia ER N DE 149 A A ae ER EN 151 Popon retora e uos 1890. O a US 154 Changing Distribution of Meshwork Fenestrate Species Throughout the Warsaw Study Area... 156 Trophic Structure in Suspension-Feeding Communities ESR COCLIIC EATS IG ue. ded e ogee moe qais pau nouos den a a Mut Anse t Dco S Rs 160 Niche Dilleremtiation: Among Living and Fossil Species rn. ra IUIS ero e eu dd TIRES Cu ee uie P SERIE ENT 160 Bryozoan Feeding Mechanism and Behavior u... .unu.a..uuenee nennen enden eee teneur eem nee nisi e co BREE STS t 161 Oc pete mue odd a N is Am 162 Morphological Features Governing Feeding Rates in Modern Bryozoan Species) erer enera „Ama en. and tert Ne 163 Warsaw Environmental and Paleoecological Setting... 163 Zoarial Emplacement and Feeding in Warsaw Meshwork Fenestrates ...ooooocorororo rene ttt 163 Parameters Used for Determining Niche Differentiation in Warsaw Fenestrates ......... 111s eee reece n 165 Possible Niche Differentiation in Warsaw Fenestrate Bryozoa ....... ooo 166 COINS: n E A a a ne TU ne 170 Appendices A. Descriptions of Warsaw Formation Sampled Outcrops and Local Ares sen keen eee ARTEN te Pinte D B. Columnar Sections for Localities Included in the Species Distribution Study .......... e c 6n 176 Pe HE us ratur A 229144 duse E te prius desee d dt ar o pun 186 Piu o e 9 c ERR RU AIA ATE RARE eue ice can E ROE roa Vade es es ee 192 Iud o A IR PEED DAF VE ARE T KADER CO IDCM two e A e 264 LIST OF ILLUSTRATIONS Text-figure Page l Warsaw Formation sample localities: 6604.5 ac cc nen. nern ee teas qne Rees en Pe HAE a nme ee AH LL ie 9 2. Typical stratigraphic sections for the northern and southern portions of the study ALEA tet ees 15 3. Comparison of interior sections of Banastella guensburgi and GDI EN ESTEE USTG re ne 21 4. Typical zoarial surficial features of meshwork fenestrates ti etra 5) 5. Characters measured in the reticulate meshwork of Hemitrypa and the central spire or axis of Archimedes eese. eese ere 36 6. Characters measured in the interior of Banastella guensburgi |... seen 37 7. Characters measured in the interior of Cubifenestella usitata... mme 38 8. Rectifenestella texax and Rectifenestella tenuissima illustrated ........ 06-00 e eee ttn 43 a ela COn e EE onen Grier a A ren ee Mn ee: 51 (sem, pcdibus pecorum 7 63 A er ester an nalen deer une anne nenne O tee a ead RT e 69 13. Banus] OUre IS OO eT NAA A O uen anu nc MA n TES 13. CUE COSTE a radis UNITE ME decere ts ae ree ame ese end ran Ute he cet cq c cce naera A 89 EA. APEC OL OSSQERURDUS DCC Ce nores koe o FOE ET 99 15. CODA PO SPHOTROU USA Iede s. cire coon namie Cyn a a LC 107 Le eI SEW OTE A DELL ae uc DOT PIDE UA 123 17. hewespuiu sont mioni A men nenn er ned na e REE me a O A 139 18. Polypora.varsoviensisalliettäted, cov cecil sv ae nennen ns ni St a rettenet rin A DOS. US 143 19. Measured sections used to determine species distribution ..........- 0. secs e metet 157 20. Changing species composition of localities in the Warsaw AA a a a cement tas 159 21. Modern stenolaemate showing zooid with tentacles extended .......... e tet 161 22. Modern stenolaemate showing zooid with tentacles retracted ....... sitet 161 23. Schematic illustration of the obverse zoarial surface of Cryptosula pallasiana ... iiie tn 165 24. Schematic illustration of the obverse surface of Banastella guensburgi |... ttn 166 25. Range of aperture spacing over obverse zoarial surface for Warsaw meshwork fenestrates ........ooooooocororrrrrracr rra 167 26. Relationship of mouth diameter to lophophore diameter for some Warsaw meshwork fenestrates ......... «o cee eee cece neues 168 27. Relationship between tentacle length and tentacle number for some Warsaw meshwork fenstrates ........ «o cere m mI 169 28. Relationship of maximum clearance rate and chamber volume for some Warsaw meshwork fenestrates ........ een 170 29. Relationship between inferred mouth diameter and calculated chamber volume for some Warsaw meshwork fenestrates ........ 171 30. Relationship between lophophore diameter and chamber volume for some Warsaw meshwork fenestrates ............. 005-5005 1/2 LIST OF TABLES Table Page . Summary of stratigraphic nomenclature used for the Middle Mississippian of Illinois... 11 . Descriptive criteria for differentiation of species of Fenestella used by Morozova CEO ee ee 20 . Characters used by Morozova (1974) for discrimination of 10 genera from the form genus Fenestella, here also applied to four Benera-ofother-authorsuilr, ar ee ee c else een ee «Es 24, 25 - Taxonomic criteria for generic divisions within the Warsaw fenestellids ...... 0.0.1... cee eee eee teeter 26,27 - Comparison of external taxonomic.characters in 11 genera of fenestellid and polyporid bryozoans ................-....45-. 28-31 - Comparison of internal taxonomic characters in 11 genera of fenestellid and POLY POMC IDEYOZ0dBS ol. scr s die se Ye 32:33 - Key to Warsaw genera of the Fenestellidae and Polyporidae —|........ e nn 34 . Definition of zooecial and zoarial characters used in species descriptions... foldout inside front cover . Outlines of species diagnoses and descriptions, and definitions of measurements and terminology employedstliereinyweoeee Dese a a qoaa. re ng Store Died foldouts inside front and back covers . Definitions and abbreviations of the 44 fenestellid and polyporid zooecial and zoarial characters meastredunstihissstudve 1991990 9x 500 OS ae de Islas mas nosis anny ceo olere foldout inside back cover "ulaxonoimiodistofi/Warsaw meshworksfenestratesspeeiesen. doas ete as duse es cies u ns « deu iunc nen 39 - Summary numerical analysis of Rectifenestella tenax (Ulrich, 1888)... 42 - Summary numerical analysis of Rectifenestella tenuissima (Cumings, 1906) ......sss e 46 - Summary numerical analysis of Rectifenestella multispinosa CTCL SIS On s veles ine Fe ae Bee 47 - Summary numerical analysis of Laxifenestella coniunctistyla, n. Sp... nennen rennen 52 - Summary numerical analysis of Laxifenestella maculasimilis, n. SD. .... e 54 - Summary numerical analysis of Laxifenestella serratula (uc O) Aare Er ee cee 57 - Summary numerical analysis of Laxifenestella fluctuata, n. Sp... 39 - Summary numerical analysis of Minilya sivonella, n. SP. ciis 62 - Summary numerical analysis of Minilya paratriserialis, n. SP. .... see 66 - Summary numerical analysis of Exfenestella exigua (Ulrich, EN ae cap een lerne ee ige 70 - Summary numerical analysis of Banastella guensburgi, n. Sp... 74 - Summary numerical analysis of Banastella cingulata (Ulrich, SOO Nae: A cur Semen, EL BR LESSE ER ! a7 - Summary numerical analysis of Banastella mediocreforma, n. Sp... nnn 80 - Summary numerical analysis of Banastella limitaris (Ulrich, E e Sco ML open o 82 - Summary numerical analysis of Banastella biseriata (Ulrich, 1890) ... cis nennen nennen 84 - Summary numerical analysis of Banastella delicata, n. SD. see 86 - Summary numerical analysis of Cubifenestella rudis (Ulrich, 1890) .........2-cemeeeeeeeeneeeneeneeneennenenenne nennen 90 - Summary numerical analysis of Cubifenestella usitata, n. SP. «ciiin 93 - Summary numerical analysis of Cubifenestella globodensata, n. Sp... ee 95 - Summary numerical analysis of Apertostella foramenmajor, n. Sp. «ciis eene 98 - Summary numerical analysis of Apertostella crassata, n. SD. «ciii eee 102 - Summary numerical analysis of Apertostella venusta, n. SP. ciiin 104 - Summary numerical analysis of Hemitrypa perstriata Ulrich, 1890 ....ssssse s 109 - Summary numerical analysis of Hemitrypa hemitrypa (Prout, 1859) «0... 61s even ene eee Tii - Summary numerical analysis of Hemitrypa aprilae, n. SP. isse 114 - Summary numerical analysis of Hemitrypa aspera Ulrich, 1890 ....s isses nn 117 - Summary numerical analysis of Hemitrypa vermifera (Ulrich, 1890) 0... 1... esis veer n 120 - Summary numerical analysis of Archimedes negligens Ulrich, 1890 ............ ce renee n 125 - Summary numerical analysis of Archimedes owenanus (Hall, CAN A a A eee 127 - Summary numerical analysis of Archimedes wortheni (Hall, SN ee N ee 131 - Summary numerical analysis of Archimedes valmeyeri, n. SP. «eee 134 : Summary numerical analysis of Fenestralia sanctiludovici Prout, ES ee M MU EUER oy arene en Tt ee 140 - Summary numerical analysis of Polypora gracilis Prout, 1860 .......:.... re enn 144 - Summary numerical analysis of Polypora varsoviensis Prout, 18582 .. esse 147 - Summary numerical analysis of Polypora spininodata Ulrich, 1890... .. 111.1 seen eee nnn 149 - Summary numerical analysis of Polypora simulatrix Ulrich, 1890... 0.0... 5 sss eee ence eset ne 152 E Summary numerical analysis of Polypora retrorsa Ulrich, O we NPE ae ee 154 - Occurrence of meshwork fenestrate species throughout the Warsaw study area... sisse 156 - Abundance of species of Warsaw Formation meshwork fenestrate byozoanssateachilocaltve Se ITUR Ce o aa 158 - Fenestrate characters used in niche differentiation ........ 60sec e tte 164 - Calculated tentacle lengths, clearance rates, and chamber volumes for species with determinable tentacle numbers ........... ITI The manuscript on which this monograph is based was awarded the Osgood Prize by the Paleon- tological Research Institution on November 7, 1989. The prize, a $500 cash award to the author(s) of an outstanding manuscript accepted for publication by the institution, is named in honor of the late Dr. R. G. Osgood. It is supported by an endowment initiated by his colleagues and enlarged by benefactors of the Paleontological Research Institution. Information on selection criteria is available from the institution. REVISED TAXONOMIC PROCEDURES AND PALEOECOLOGICAL APPLICATIONS FOR SOME NORTH AMERICAN MISSISSIPPIAN FENESTELLIDAE AND POLYPORIDAE (BRYOZOA) by EDWARD MCKINLEY SNYDER Division of Science and Mathematics Shepherd College Shepherdstown, WV 25443 ABSTRACT Fenestellid and polyporid Bryozoa of the lower Middle Mississippian Warsaw Formation of the Mississippi River outcrop belt are represented by nine genera of Fenestellidae (three of which are new: Banastella, Cubifenestella, and Apertostella) and two genera of Polyporidae. Twenty-two previously described species and fifteen new species are recognized. New species are: Laxifenestella coniunctistyla, Laxifenestella maculasimilis, Laxifenestella fluctuata, Minilya sivonella, Minilya paratriserialis, Banastella guensburgi, Banastella mediocreforma, Banastella delicata, Cubifenestella usitata, Cubifenestella globodensata, Aper- tostella foramenmajor, Apertostella crassata, Apertostella venusta, Hemitrypa aprilae, and Archimedes valmeyeri. Exterior and interior analyses of bryozoan zoaria are employed in the classification of meshwork fenestrate Bryozoa, separating Zoarial and zooecial features and emphasizing three-dimensional form, chamber size, and accessory features. The format presented in this study is designed to be employed as a thorough outline for classification. Change of meshwork fenestrate species composition within the Warsaw from north to south within the study area could have been caused by environment or evolution; however, a significant change in faunal composition is evident. Employing modern cheilostomes as analogues, possible niche differentiation of meshwork fenestrates is established for the Warsaw. Chamber volume, lophophore diameter, mouth diameter, interpreted maximum zooid clearance rate, tentacle number, and tentacle length are criteria used to infer fenestrate niche partitioning. These criteria, in conjunction with food particle size and efficiency of the feeding organ (lophophore), appear to be dominant factors governing niche partitioning within the meshwork fenestrates. ACKNOWLEDGMENTS This work is the culmination of more than 10 years Ofresearch into fenestrate Bryozoa, one result of which Was completion of my Ph. D. degree at the University of Illinois. There have been numerous individuals, from armers directing me to the most fossiliferous spots in the creek bed to fellow researchers offering constructive Comments regarding my research, who have contrib- uted to the content of this work. To all of these people Lowe a sincere debt of gratitude. I would, however, like to recognize several individ- uals whose assistance was instrumental in the evolu- tion of this work. First and foremost I would like to thank Daniel B. Blake for initially introducing me to the Spectacular fossils of the Warsaw Formation, for his helpful suggestions and wealth of ideas, and most of all for his patience and direction during my com- Pletion of this lengthy study. George deVries Klein, alph L. Langenheim, Philip Sandberg, and Daryl Sweeney, all of the University of Illinois, read the Manuscript, offered helpful suggestions, and served as Members of my dissertation committee. Ken McKin- Dey-of Appalachian State University, and Alan Ho- TOwitz of Indiana University reviewed the revised Manuscript that was submitted for publication to the aleontological Research Institution. Their extremely thorough and insightful reviews significantly improved the manuscript and their efforts are greatly appreciated. Sincere thanks are due to Peter Hoover, for his pa- tience, support, and thoughtful editorial recommen- dations, which have significantly improved the form and content of this work. Assistance in the field was provided by Thomas Guensburg, Paul Sivon, Dan Blake, and numerous un- dergraduate students who contributed fossil Bryozoa for my use; the help and companionship while under- taking the extensive field work involved in the study is greatly appreciated. A special thanks is due to Steve Hageman of the University of Illinois for his encouragement and as- sistance. His quantitative analysis (Hageman, 1987) of the morphometric data presented in this paper pro- vided an important test of the taxonomic approach developed herein. Richard S. Boardman and Alan H. Cheetham of the United States National Museum of Natural History (USNM), Washington, DC; Alan Horowitz, of Indiana University, Bloomington, IN; Lois Kent and Dennis R. Kolata, ofthe Illinois State Geological Survey (ISGS), Champaign, IL, arranged for the loan of specimens by their respective institutions. The publication cost of a document of this size is a significant financial burden. In a very real sense, pub- lication of this study has been made possible by the financial support of numerous institutions and indi- viduals. Howard Carper and Donald Henry of Shep- herd College, Shepherdstown, WV, provided both moral and, directly or indirectly, financial support; their efforts on my behalf are greatly appreciated. The Shep- herd College Foundation and Shepherd College Fac- ulty Minigrant Fund have both provided significant financial support; such assistance is not only appreci- ated, but is critical in a work of this size. I was fortunate to have the manuscript recognized by the Osgood Prize Committee and the Trustees of the Paleontological Re- search Institution (PRI), who awarded the 1989 Os- good Prize to this work. The $500 prize award was applied to the publication costs; further, the PRI con- tributed an additional $2,000 from the Osgood Fund toward publication costs. The remaining funds nec- essary were earned through revenues gained from teaching course overloads, elder hostels, and children’s colleges, and through geologic consulting, archaeolog- ical site surveys, and other means as available; this makes the above financial assistance doubly appreci- ated. I would also like to thank all those who have pa- tiently tolerated my preoccupation with fenestrate Bryozoa, and especially I would like to thank my wife Cathy for her assistance and patience during this en- deavor. INTRODUCTION General statement of investigation.—The primary goals of this study are twofold: (1) modernization of taxonomy of fenestrate Bryozoa; and (2) paleoecologic analyses based on the new taxonomy, resulting in func- tional morphologic interpretations for the fenestrates. The Warsaw Formation (upper Osagean of U. S. Geological Survey terminology, or middle Valmeyeran of Illinois Geological Survey terminology) of the upper Mississippi Valley was selected for study because of its abundant, taxonomically diverse, well-preserved bryozoan fauna. Further, the Carboniferous represents the peak of fenestrate diversification at both the species and genus levels. The Warsaw is geographically wide- spread, flat-lying, and locally moderately well-exposed, and is part of the Mississippian stratotype. Litholog- ically, the Warsaw is composed of sequences of alter- nating argillaecous shale, calcareous shale, and bio- calcarenite, some of which have been dolomitized and contain quartz and calcite geodes. This study was re- stricted to outcrops. Fenestrate species concepts to date have been vague, even among species thought to be common. Varying emphasis on exterior or interior analyses, and primary reliance on two-dimensional tangential sections have led to a proliferation of unrecognizable species. Estab- lishment herein of an outlined systematic approach to species delimitation clarifies taxon recognition, pro- PALAEONTOGRAPHICA AMERICANA, NUMBER 57 vides a comprehensive basis for generic groupings, and yields a taxonomic basis that can be applied to other faunas. Although fenestrate bryozoans are a major compo- nent of the Warsaw fauna, the most recent taxonomic study of this unit is that of Ulrich (1890). Advances in fenestellid taxonomy (Termier and Termier, 1971; Morozova, 1974; McKinney, 1980) make Warsaw bryozoans appropriate subjects for taxonomic revi- sion. Specific and generic taxonomic assignments are based on recent conceptual advances including application of three-dimensional autozooecial chamber and zoar- ial reconstructions, study of populations, and employ- ment of statistical analyses. Whether studies are bio- stratigraphic, paleoecologic, taphonomic, or evolutionary, their strengths and/or weaknesses are largely dependent on taxonomy. Conclusions of any nature using species defined on haphazard systematics or weak taxonomic concepts can be more misleading than useful. Use of taxonomic data in conjunction with strati- graphic and sedimentologic data provides the basis for functional morphologic and paleoecologic interpreta- tions of trophic structuring, niche differentiation, and faunal succession. Location and extent of field area.—The Warsaw shale outcrop belt includes the Illinois and Mississippi River valleys extending from Nauvoo, Illinois in the north to Valmeyer, Illinois in the south, and as far northeast as Beardstown, Illinois along the Illinois River. The area also extends into eastern Iowa and Missouri (Text- fig. 1). Dimensions of the major part of the area are approximately 220 mi (352 km) in a north-south di- rection and from approximately 40 mi (64 km) to 85 mi (136 km) in the east-west direction. The one studied outcrop in Howard County, Missouri lies 120 mi (195 km) west of the main outcrop belt. In total, outcrops at 49 localities were examined and are described in Appendix A. Twenty-three localities were examined in detail and used for biostratigraphic and paleoenviron- mental determinations. Stratigraphic columns and range charts for these 23 sections are presented in Ap- pendix B. Other localities were used as data checks. Because of low resistance to weathering, Warsaw outcrops are relatively poor. Throughout the area, to- pography is of low relief, and strata are overlain by Pleistocene till, thick soil profiles, and dense vegeta- tion. Roadcuts and quarries usually provide the best- preserved material, as weathering and presence of li- chen and mosses commonly obscure rock surfaces in stream valleys and along river cuts. Field and laboratory methods.— Approximately six months were spent in measuring, describing, and sam- pling 49 stratigraphic sections during the summers of MISSISSIPPIAN BRYOZOANS: SNYDER | dp wes sen vile | j | | T—a—-p-- Bene GONE me ee | pue | a bisi NORTH es E n | ! \ 4 ae, Amit pe’ TS RR UE I ie q i f e: | | O | j 9o - | KEOKUK 80, po js Ora. Dy > 11 Ey a vb N et 1L-— 900 | | | eeu. zi as i ES ane SEEN Tasse Tobe? E veu | | WB. = ul SoBe ‚ILLINOIS pS WW T 1 MISSOURI ; "s E e [ i ^ ^ EE | ee M ^ 26 9 | c Nurs 27 = à 7 Lose e een pa 94s adash danone FO doge 240 36 | | = 4,995 Spee etisalat mend a ne on | degno or p ST LOUISt --- os dn | Missouri River teil: | | | hg tad perii | | | Z c | n Er | * woa : | Eis | Dr een | reri i I Index Map er Eier 3 / | ó 40 20 30 40 50 miles =- Boi -—4— 6 10 20 S040 C0 ao kilometers ee @ sample localiti scu p alities Text-figure 1.— Warsaw Formation sample localities. 10 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 1977 through 1980. McKee and Weir’s (1953) classi- fication was used for recording bedding thickness; car- bonate classification is after Carozzi (1972). Lithologic samples totalling over 4,500 Ibs (approx. 2,000 kg) and consisting of both fossiliferous and unfossiliferous slabs were collected and returned to the laboratory. Ap- proximately 200 thin-sections, supplemented by nu- merous acetate peels, were made from samples rep- resentative of the different facies present in the Warsaw. Polished slabs were prepared for the study of sedi- mentary features and textural analysis. Stratigraphic columns and lithologic descriptions were prepared for 23 of these measured sections; these were also analyzed for species distribution. The remaining localities pro- vided stratigraphic control and are described briefly in the locality register (Appendix A). Both exterior and interior analyses of fenestrate bry- ozoans are necessary, requiring extensive preparation. Shale samples and limestone surfaces were sieved and washed, respectively, to expose external zoarial sur- faces. Zoaria were soaked in hot water and then placed in an ultrasonic bath for one to five minutes, depending on robustness of colonies, to remove surface debris. Internal bryozoan analyses are based solely on acetate peels. Peel preparation follows the procedures of Boardman and Utgaard (1964) and Nye, Dean, and Hinds (1972). Acetate peels are superior to thin-sec- tions for description of skeletal structures because: (1) skeletal microstructure is shown in greater detail, as peels possess minimum relief, approaching a two-di- mensional surface, whereas thin-sections are three di- mensional slabs whose thickness frequently obscures many details; (2) many peels may be made of each zoarium, showing different orientations necessary for three-dimensional reconstruction; (3) serial peels can be taken at short intervals permitting three-dimen- sional reconstruction; (4) multiple peels of any surface can be made, providing duplicates for distribution to other workers; (5) plug surfaces from which peels are made can be studied with the Scanning Electron Mi- croscope (SEM); (6) plug surfaces can more readily be reground to ‘obtain the correct orientation, whereas thin-sections typically allow only one attempt at ori- entation; and (7) peel preparation is much more rapid. Subsequent to exterior analysis, specimens were em- bedded in epoxy (Epotuf® two-part resin and hardener with a mixture of 4.5 parts resin to 1 part harderer, by weight). Between 40 and 50 ml of propylene oxide were added to every 200 ml of mixed epoxy to thin the mixture for embedding. Specimens were placed in ep- oxy and vacuum-pumped to enhance epoxy penetra- tion. Once the specimens were cut, 250- and 600-grit papers were used for grinding; the use of paper-backed abrasives minimized grit adherence. A final buffing on well-worn 600-grit paper helped prepare the plug sur- face for polishing. Mirror-like polish was achieved with Buehler’s mi- crocloth and a slurry of 0.05 um tin oxide polishing compound mixed with liquid detergent (Palmolive®), on a variable-speed polishing wheel. Best etch was at- tained by gentle agitation of polished specimens in dilute (0.5% to 1.0% by volume) formic acid for four to six seconds. Formic acid yields greater contrast peels than do hydrochloric or acetic acids. Short etching times were used for orientations illustrating closely packed laminae, such as transverse and shallow tangential ori- entations; longer etching times were necessary for ori- entations containing more granular calcite and greater spacing between laminae, particularly in longitudinal and deeper tangential sections. Some surfaces used for peels were then washed with acetone and gold-plated for SEM study. High-contrast Kodak® D-19 developer was used for all film. Contact prints were made using AZO® 3 and 4 and 4x5 format negatives; 35 mm negatives were enlarged and printed on Kodabromide® 3 and 4. All steps of developing and printing were done in such a way as to enhance contrast in the final prints. MISSISSIPPIAN STRATIGRAPHY AND STRUCTURAL GEOLOGY OF THE UPPER MISSISSIPPI VALLEY Regional geologic setting. — During most of the Mis- sissippian, the Illinois Basin (Eastern Interior Basin) slowly subsided along a north-south trend. The Trans- continental Arch and Mississippi River Arch to the west, the Wisconsin Arch to the north, the Cincinnati Arch-Nashville Dome trend to the east, and the Ozark Dome in the southwest could have contributed to the large amount of detrital material accumulated in the basin (Potter and Pryor, 1961; Walker, 1962). All these areas either were slightly positive or exposed during the Valmeyeran (Walker, 1962), as indicated by ero- sion of materials from them. Clastic sediments came predominantly from the delta-distributary system of the Michigan River, feeding into the Illinois Basin from the northeast during middle to late Valmeyeran time (Atherton and Palmer, 1979). Little material was in- troduced, but much autochthonous carbonate was pro- vided by the indigenous fauna and flora. Bed thickness, cross-bedding, and the nature of facies distribution suggest a northwest-southeast shoreline trend (Ath- erton and Palmer, 1979). In the early Valmeyeran (Osagean), sediment yield from the northeast greatly decreased, leaving the Illi- nois Basin relatively starved (Atherton and Palmer, 1979). During this time the widespread Burlington Limestone, a clean crinoidal biocalcarenite, was de- posited. This unit represents a broad carbonate shelf throughout the Mississippian stratotype area (Atherton and Palmer, 1979). By middle Valmeyeran, the Borden Delta resulted in the resumption of supply of clastic MISSISSIPPIAN BRYOZOANS: SNYDER 11 Table 1. Summary of stratigraphic nomenclature used for the Middle Mississippian of Illinois. The leftmost column indicates the usage followed in this paper. S. Weller 1908 VanTuyl 1925 Ulrich 1904 Worthen 1866 Formations Moore 1933 J.M. Weller 1940 J.M. Weller 1948 Swann 1963 Laudon 1948 St. Genevieve Formation ee St. Louis Limestone | Salem Limestone FE. d Sonora Formation St. Genevieve Group Meremec Meremec Group Group St. Louis Group Meremec Group Warsaw Formation Keokuk Limestone Keokuk à Osage Group Group Osage Group Osage Group Burlington : Burlington Limestone Group Valmeyer Series Genevieve Stage Meremecian Group Meremec Group Meremec Group Meremec Group Unnamed Iowa Series t Valmeyer Series Osage Group Osage Group Osagean Group Osage Group Sediments from the northeast (Atherton and Palmer, 1 979), Fine-grained clastics brought in by the Michigan Iver System began accumulating on the carbonate shelf to the west, resulting in shale in the Keokuk Lime- Stone, which conformably overlies the Burlington Limestone, The carbonate shelf was covered finally by the clays and silts of the Warsaw Formation. Valmeyeran Series (Osage-Meramec Series).—The U. s. Geological Survey (U. S. G. S.) and Illinois State Cological Survey (I. S. G. S.) employ different ter- Minology for units lying between the Kinderhookian and Chesterian series. The U. S. G. S., the Missouri *ological Survey, and others use Osage Series to in- ude rocks from the top of the Chouteau Limestone and Hannibal Shale through either the Keokuk Lime- Stone (Ulrich, 1904; Van Tuyl, 1925; Weller et al., l 48; Harris and Parker, 1964) or through and in- cluding the Warsaw Shale (Branner, 1888; Weller, 1914; Core, 1933; Weller and Sutton, 1940; Laudon, 1948). he Meramec Series as so defined extends from the top of the Osage Series to the Renault Formation. The L : G. S. combines the two into the Valmeyeran Se- “es (Weller and Sutton, 1940) with its stratotype in €nnis Hollow at Valmeyer in Monroe County, Ili- POY Table 1 provides a summary of differences in Stratigraphic classification. The Osage—Meramec Series are combined by the I. S. G. S. because of the difficulty In Consistently delineating a boundary between the two Series (Pryor and Sable, 1974). The boundary is not marked by a physical break (Weller and Sutton, 1940; Wanless, 1957; Baxter, 1972) and disagreement exists On the ages of fauna in the Warsaw and its supposed cl lateral equivalent, the Harrodsburg Formation (Pryor and Sable, 1974). Continuous accumulation of sediment without ev- idence of a physical break in deposition could be a positive factor in recognizing a stratigraphic division between the Osage and Meramec Series at the Keokuk- Warsaw lithologic boundary, as the change in fauna used for biostratigraphic interpretation would be based on evolution, not on lack of depositional continuity. Complex facies and environmental factors resulting in interfingering of Keokuk-type material with the lower Warsaw lithologies, and Warsaw lithologies in the overlying Sonora and Salem lithologies provide no ev- idence of widespread lithologic unconformities in this stratigraphic interval, thus affirming continuity of de- position. Conclusions on the placement of this bound- ary based on lithostratigraphic and bryozoan biostrati- graphic interpretations are presented on p. 156. Middle Valmeyeran (Mississippian) formations.— Middle Valmeyeran lithostratigraphic units relevant to this investigation include the Keokuk Limestone, War- saw Shale, Sonora Formation, Ullin Limestone, Salem Limestone, and St. Louis Limestone (see Appendix B and Text-fig. 2). Keokuk Limestone: The Keokuk Limestone (Owen, 1852; Hall, 1857a; Van Tuyl, 1925) is 70 ft (21.3 m) of cherty biocalcarenitic limestone with shaly partings. The type section is along Soap Creek at Keokuk, Lee County, Iowa. The Keokuk ranges from 60 to 80 ft (18.3 to 24.4 m) thick throughout the study area, and conformably overlies the Burlington Formation. The lower 30 ft (9.1 m) of the Keokuk near the type section is differentiated as the Montrose Chert Member (Keyes, 1895; Collinson, 1964) by its abundant chert. The Keo- kuk above this member consists of crinoidal, bryozoan, and brachiopod-rich biocalcarenite locally interbed- ded with fine-grained limestone, argillaceous dolomite, and calcareous medium- to dark-gray shale. South of St. Louis, the upper Keokuk consists of a thick oolitic lithology, termed the Short Creek Oolite Member of the Keokuk. The Keokuk—Warsaw contact is grada- tional, with a gradual upward increase in number and thickness of shale beds. The boundaries of the Keokuk Formation coincide with those of the Gnathodus tex- anus-Taphrognathus conodont Zone of Collinson, Scott, and Rexroad (1962). The brachiopod species Spirifer logani Hall, 1858, Dictyoclostus crawfordsvil- lensis (Hall, 1858), Orthotetes keokuk (Weller, 1914), and Rotaia subtrigona (Meek and Worthen, 1860) are confined to the Keokuk (Weller and Sutton, 1940). The first occurrences of several bryozoan genera, including Worthenopora Ulrich, 1890, Cyclopora Prout, 1858a, Cycloporella Ulrich, 1890, and Proutella Ulrich, 1890 are in the Keokuk. The Keokuk is conformably over- lain by the Warsaw wherever the contact is exposed. Warsaw Formation: The Warsaw Formation was named by Hall (1857a) for an exposure of approxi- mately 50 ft (15.1 m) of shale lying between the Keokuk Limestone and the St. Louis Limestone in Geode Glen at Warsaw, Hancock County, Illinois. This section sub- sequently was designated the type section by Collinson (1964). Geode beds originally included in the upper Keokuk were reassigned to the basal Warsaw by Butts (1915) and Van Tuyl (1925). The areal extent of the Warsaw in southern Iowa, eastern Missouri, and west- ern Illinois was also presented by these authors. Due to the accessible outcrops and abundant fauna of the Warsaw, the unit was intensively studied by many early stratigraphers and paleontologists of the Mississippi Valley region, including Ulrich (1890), Weller (1914; 1926), Worthen (1870), Worthen, Shaw, and Meek (1873), and Gordon (1895). Much of their stratigraphic work and many of their faunal descriptions are accu- rate and complete. As defined, the Warsaw was considered equivalent to the Harrodsburg Limestone of Harrodsburg, Indi- ana (Butts, 1915). This led to abandonment of the name Harrodsburg because Warsaw had priority (Butts, 1915; Cumings, 1922). In Indiana, the base of the War- saw was placed at the top of the Holtsclaw Sandstone. Three members were included in the Warsaw of In- diana and Kentucky. These are, in ascending order, the Wildie Sandstone, the Somerset Shale, and the Gar- ret Mill Sandstone. Weller (1934) proposed restoration of the name Harrodsburg as it was originally used in Indiana and Kentucky, restricting the Warsaw For- mation to its earlier status: all beds between the Keo- PALAEONTOGRAPHICA AMERICANA, NUMBER 57 kuk and St. Louis limestones. Weller also suggested dividing the Warsaw into members in the type area, where such divisions seem applicable. In a faunal study of the Keokuk, Warsaw, and Salem formations, Laudon (1948) found that of the 30 in- vertebrate species recovered, the Keokuk and Warsaw had 27 incommon. The Warsaw and Salem were found to have very limited faunal similarity. In Laudon’s investigation, the Salem, which had been removed from the upper Warsaw by Weller (1908), was once again recognized as a member of the Warsaw. Collinson (1964) redesignated the type section, preferring Well- er’s arrangement to that of Laudon. It is the type sec- tion as described by Collinson that is generally used in modern studies (Atherton and Palmer, 1979). Parts of the Sonora Formation and Salem Lime- stone, once assumed to be younger than the Warsaw Formation, were found in this study to be equivalent in age, as indicated by bryozoan bioclasts. Several stratigraphic sections analyzed contain interbeds of both Sonora and Salem lithology within the middle and upper Warsaw, respectively. Sand Branch (loc. 15) con- tains upper Warsaw overlying the Salem, McKee Creek (loc. 21) contains upper Warsaw overlying the Salem, Versailles West (loc. 22) has interbeds of Salem (So- nora of Collinson, 1964) and Warsaw lithology, and Lacy Keosauqua (loc. 3) has beds of Warsaw lithology in the Sonora. Collinson, Scott, and Rexroad (1962) and Rexroad and Collinson (1965) studied conodonts of the Keo- kuk, Warsaw, Salem, and St. Louis formations. They assigned the Warsaw, Salem, and lower St. Louis for- mations to the Taphrognathus varians— Apatognathus Zone. This zone is equivalent to the lower half of the Taphrognathus varians-Cavusgnathus-Apatognathus Zone of Rhodes, Austin, and Druce (1969), and the entire Cavusgnathus unicornis-Apatognathus Zone. Wills (1971) found the Sonora assignable to the Taph- rognathus varians-Apatognathus Zone as defined by Collinson, Scott, and Rexroad (1962). Previous difh- culties in separating the Warsaw, Salem, Sonora, and St. Louis formations support these conclusions. The boundary between the Warsaw and Keokuk in the stratotype area has been a point of dispute among authors because of the variability in lithology and fau- nal content ofthe lower Warsaw. Some sections of the Warsaw consist of 25 to 45 ft (7.7 to 13.9 m) of un- fossiliferous to scarcely fossiliferous gray to brownish- gray, fine-grained, geodiferous dolostone, with in- creased amounts of argillaceous shale toward the top. Other sections, some located within a mile of the first, show a similar thickness of highly fossiliferous cherty biocalcarenite lenses interspersed in fossiliferous shale, with no sign of dolomitization or presence of geodes. The upper Warsaw is more uniform throughout the MISSISSIPPIAN BRYOZOANS: SNYDER 13 are ee ; a $ à | grece of from 20 to 32 ft (6.1 to 9.8 m) of enite. A general increase in clay particle size is observed pe y highly fossiliferous bluish-gray shale interbed- up section (Wills, 1971). The total thickness of the *d with fossiliferous silty and dolomitic biocalcar- Warsaw is as much as 300 ft (92.3 m), consisting mostly SGS- USGS FEET CEET SYS. |SERIESISERIES|FORMATION|LITHIC TYPE (METERS) FORMATION ILITHIC TYPE (METERS) | > | @ | LOUIS = t LOUIS s 33] " 2% | 1(91,4-152) LIMESTONE / ] d he LIMESTONE| | Loe Dd | œ [ lo | oo ] mm SEES oo oo a SALEM [ele e Lee | 0-40 bl oo Too Be Lm Igne e oo [oo fo M AE A SALEM j M E SOMETE a o | R er MA (305 152) S oum o oni V A | SONORA = 0-60 | S FORMATION[= E oo |oo | A M = 918,0) Sl omer e E L E TEENAAN S M e - I E Ga S E | em | U Å ——- I i y A W L ELLE [nage N "blade en Por WARSAW BE NR emm | A SAALE (222808) : N == I : E => 4 AN >= M een N $ (q an oin E H ap HD A EE Pp E o = A | KEOKUK == 24 TOO SEGA G LIMESTONE | = | (18.3-24.4] KEOKUK e | æ | 60-100 E LN LIMESTONELL_@ | e j8.3-305) A | = e | ee] e ae E N - uu ol æ | NORTHERN PORTION OF STUDY | SOUTHERN PORTION OF STUDY AREA AREA LEGEND Le ta £ CHERTY LIMESTONE ST] ARGILLACEOUS LIMESTONE EP ELE E SHALE WITH LIMESTONE LENSES 7 CHERTY DOLOSTONE e le Y TONE W a a UR ARGILLACEOUS SHALE le [9] O O SEO o Je] OOLITIC LIMESTONE HH] CALCAREOUS SANDSTONE o o pa f E arm GEODIFEROUS ARGILL ACEOUS BRECCIATED LIMESTONE -/-&-| LIMESTONE AND DOLOSTONE Text-figure 2. — Typical stratigraphic sections for the northern and southern portions of the study area. of siltstone in west-central Illinois, and thins to less than 100 ft (30.7 m) in the outcrop area, where it consists of mostly shale and argillaceous biocalcaren- ite, with a small silty component near the top of some sections. Lineback (1966), relying almost exclusively on drill cuttings and core and electric log data, analyzed War- saw and younger Mississippian strata from their west- ern edge into the Illinois Basin. Where the Keokuk and Burlington formations pinch out eastward, Lineback described the Warsaw as being separated from the Bor- den Siltstone by a vertical cutoff. The Bilyeu Member of the Borden Siltstone extends westward into the War- saw Formation, thereby becoming a member shared by both formations (Lineback, 1966). The Warsaw Formation was thus most probably deposited coevally with the upper part of the Borden Siltstone. The Warsaw is typically conformably overlain by the Sonora, Salem, Ullin, or St. Louis formations, al- though local unconformities between the Warsaw and overlying units are observed in some exposures. Sonora Formation: Keyes (1895) named the Sonora Formation for approximately 20 ft (6.1 m) of cross- bedded dolomite to dolomitic sandstone in the Sonora Quarry, 5 mi (7.5 km) north of Nauvoo, Illinois. The Sonora varies over a spectrum from arenaceous or ar- gillaceous dolomite through fine-grained dolomitic sandstone to greenish-gray sandy shale. Dolomitiza- tion tends to increase downward, and appears to be associated with grain size (Wills, 1971). Much of the Sonora is formed of dolomitized fenestellid debris. Conodonts (Collinson, Scott, and Rexroad, 1962) and the few megafossils (Wills, 1971) indicate equivalent age with the Warsaw and Salem; the Sonora grades laterally into these units (Collinson, 1964). The Sonora is overlain by both the St. Louis and Salem formations. Contact between the Sonora and Salem is conformable; between the Sonora and St. Louis, it is either conform- able or erosional, with the St. Louis in the latter case being highly brecciated. The unit crops out mainly in Adams and Hancock counties in Illinois and in the southeast corner of Iowa, and occurs in the subsurface of much of west-central Illinois. Weller (1908) designated the 8 ft (2.3 m) of cross-bedded limestone below the St. Louis Limestone as the Salem Limestone, and Van Tuyl (1925) assigned the name Belfast to arenaceous dolomite exposed south of Belfast, Iowa. Both of these units are equivalent to the Sonora Formation. Collinson (1964) resurrected the name Sonora Sandstone sensu Keyes, 1895. Ullin Limestone: Lineback (1966) proposed the name Ullin Limestone for a unit composed of up to 800 ft (246.1 m) of light-colored, fine- to coarse-grained bio- calcarenite. The type section was compiled from three exposures near Ullin, Pulaski County, Illinois. The Ul- PALAEONTOGRAPHICA AMERICANA, NUMBER 57 lin Limestone, sensu Lineback, is a combination of two previously named formations: the upper Harrodsburg Limestone (Hopkins and Siebenthal, 1897; Stockdale, 1939) and the lower Ramp Creek Limestone (Stock- dale, 1929). The units are lithologically distinct, the former composed ofa light-colored coarse-grained bio- calcarenite and the latter consisting of cherty, argilla- ceous biocalcarenite that contains glauconite in some horizons. Lineback combined these units because he could not differentiate them in about one-third of the Ullin area of occurrence (e.g., Hamilton County, and on the crest of the Borden Delta). Lineback considered the Ullin Limestone a deep-water deposit, filling around the slopes of the Borden Delta and the deep-water tongue of the Fort Payne Formation. The Ullin Lime- stone overlies the Fort Payne Formation (or the Cho- teau Formation where the Fort Payne does not occur), or the Borden, Springville, or Warsaw formations, and underlies the Salem Limestone (Lineback, 1966). In western Illinois, the Ullin laterally grades into the War- saw Formation. Salem Limestone: The Salem Limestone was named by Cumings (1901) for Salem, Washington County, Indiana, near which it is quarried extensively for build- ing stone. The names Spergen Hill or Spergen were also applied to this limestone in some later works. Hall (1864) includes the western Illinois bluffs and the In- diana localities in his work on the fauna of this unit. A maximum thickness for the Salem of over 500 ft (153.8 m) is attained in southeastern Illinois, with gen- eral thinning to the north. In the area of this investi- gation, the Salem ranges from 100 ft (30.7 m) in the south to a few feet thick in the north. At the Warsaw type section in Geode Glen, the Salem is about 5 ft (1.5 m) thick, and consists of cross-bedded brown, weathered biocalcarenite that laterally grades into cal- careous sandstone. Equivalent material in southeast- ern Iowa consists of cross-bedded to massive biocal- carenite, dolomite, and fine-grained sandstone. In southern Illinois, the Salem is more uniform, coarsely crystalline, and may have an oolitic, biocalcarenitic composition. The varied nature of Salem facies along the entire extent of its northern exposure may relate to the shallow Salem depositional environment in this area. The presence of evaporites (anhydrite and gyp- sum) and sandstone tends to support this conclusion. The more uniform lithology of the Salem of southern Illinois is probably associated with deep-water depo- sition. Baxter (1960) subdivided the Salem Limestone into four members. They include, from the basal to the uppermost, the Kidd Member, the Fults Member, the Chalfin Member, and the Rocher Member. Criteria on which these divisions are based are subtle, using bed thickness and slight differences in lithology. In the MISSISSIPPIAN BRYOZOANS: SNYDER 15 Northern outcrop, the Salem lies on either the Sonora Formation or the Warsaw Formation, whereas in the South the Salem overlies the Ullin Formation. Fairly abundant crinoids, bryozoans, and forminifera (par- ücularly species of E ndothyra Phillips, 1841) are pre- dominant faunal components in the Salem. The St. Louis Limestone lies on top of the Salem. St. Louis Limestone: The St. Louis Limestone was named by Engelmann (1847) for about 200 ft (61.2 m) of Predominantly micritic or lithographic, fine-grained, cherty calcilutite exposed at St. Louis, Missouri. Lith- Ologic variability is evident in the St. Louis, with rock types ranging from coarsely crystalline calcarenites to Cvaporites. The unit is exposed in the Mississippi and Illinois River valleys. Its maximum thickness is 500 ft (153.8 m) in southeastern Illinois, at the maximum depth of the Illinois Basin. In western Illinois, near eokuk and Quincy, the St. Louis lies on either the Warsaw or the Sonora. The St. Louis generally overlies the Salem in southern Illinois, and underlies the Ste. Genevieve Limestone. The contact between the St. Ouls and underlying units is typically conformable, although there is local evidence of an unconformity Where Collapse breccias are found. Structural setting. — The study area lies on the west- erm edge of the Illinois Basin. This basin possesses a NNw to SSE trend, and is egg-shaped in outline, hav- a Its more elongate end in Kentucky and Tennessee and its eastern edge in Indiana (Willman et al., 1975). in of the Illinois Basin appears to have gun in Cambrian time and continued throughout E of the Paleozoic (Willman et al., 1975). Seas ad- ee from the south and at times from the west, e Ndating the area intermittently until the late Penn- vanian. Outcrops are typically associated with sub- © Structures within the Illinois Basin. The northern half of the area, extending from Ben- a Iowa in the north to White Hall, Illinois in © south, is on the southern edge of the Mississippi Arch, a tectonically positive area separating the Illinois oo and the Forest City Basin. Strata dip gently east- litis: Say from the Mississippi Arch and into the the a Basin. A secondary structural feature, named angamon Arch (Whiting and Stevenson, 1965), Probably corresponds with upwarping in this area. Ovement began in the Late Silurian and lasted ee the Devonian and Early Mississippian, as 88ested by truncation of units at the edge of the angamon Arch and thinning of isopachs over this on Structure. Locations and trends of major struc- rural features are thoroughly illustrated and described in Treworgy (198 1). dies, Warsaw Dome or Anticline, described by Bell Ilii ), 1S located approximately 3 mi NE of Warsaw, Mois. Similar small anticlinal structures also occur to th in Brown, McDonough, Pike, and Greene counties. These structures include the Payson, Fishhook, Pitts- field, Drake-White Hall, Carrollton (a set of three: northern, middle, and southern), and Versailles anti- clines. The Warsaw, Versailles, Drake—White Hall, and Carrollton anticlines are all associated with outcrops of Warsaw strata. The southern half of the area, running from southern Calhoun County on the north to Valmeyer, Illinois in the south, shows much greater structural complexity. The Lincoln Fold extends through parts of Madison County, the southern edge of Jersey County, and across Calhoun County. This broad anticline trends north- westward, paralleling the Mississippi River, and ex- tends through Missouri almost to the Iowa border. Initiation of the fold is associated with regional tilting away from the Ozark Uplift, starting during the Or- dovician but not developing as a highly positive feature until the latest Devonian or Early Mississippian (Rub- ey, 1952). Final emergence occurred during or after the Late Pennsylvanian, contemporaneous with the Ap- palachian Revolution (McQueen, Hinchey, and Aid, 1941). The Cap au Gres Faulted Flexure occurs on the southern limb of this anticline. It is a narrow belt of strata that exhibits a southward dip, which locally ap- proaches vertical and which is intersected by numerous discontinuous vertical faults. This flexure trends east- southeast, extends through Lincoln County, Missouri and parts of Calhoun, Jersey, and Madison counties in Illinois, and apparently terminates between Grafton and Alton, Illinois. The Cap au Gres Faulted Flexure developed as the structural transition between the Lincoln Fold to the north and the Troy-Brussels Syncline to the south (Rubey, 1952). Beds dip gradually northward at low angles from the Ozark Dome in the extreme south of this flexure. North of the Lincoln Anticline and Cap au Gres Faulted Flexure, beds rise at shallow dips to- ward the Mississippi Arch, although in some areas this rise is interrupted by a series of minor folds (Rubey, 1952). Deformation of the flexure occurred during the Late Mississippian or Early Pennsylvanian, as evi- denced by the steep folding of the St. Louis Limestone (Valmeyeran) and the overlapping of this structure by the Spoon Formation (Desmoinesian). Associated with this flexure and the Lincoln Fold are numerous synclinal structures, some small but oth- ers attaining substantial size. These include (from north to south) the Hardin, Gilead, Kritesville, Otter Creek, Meepen, and Troy-Brussels synclines. The Nutwood, Deer Lick and Beltrees—Melville anticlines also occur in this area. Outcrops of the Warsaw are associated frequently with some of these structural features, including the Cap au Gres Faulted Flexure, the Otter Creek Syncline, the Beltrees-Melville Anticline, the Waterloo-Dupo Anticline, and the Valmeyer Anticline. Extension of the Cap au Gres Faulted Flexure into Missouri results in good exposures of Warsaw strata near Troy, Mis- souri. The Waterloo-Dupo Anticline and associated Co- lumbia Syncline, both located in Monroe and St. Clair counties, expose the Salem Limestone and upper War- saw Formation along the Mississippi River bluff. Cole (1961), using geologic and geophysical evidence, sug- gested this anticline is an extension of the Lincoln Fold. In his structural model, the Cap au Gres Faulted Flex- ure is a left-lateral fault that offset the Waterloo-Dupo Anticline from the Lincoln Fold by a distance of ap- proximately 30 mi (48 km). This contradicts Rubey’s work, in which it was concluded that the Cap au Gres Faulted Flexure is primarily a fold and only subordi- nately faulted. The west sides of both the Lincoln Fold and Waterloo-Dupo Anticline show their steepest flanks. This and their overall similar shapes tend to support Cole’s interpretation. Farther south, in Monroe County, the Valmeyer An- ticline and associated Monroe City Syncline expose most of the Valmeyeran Series in Dennis Hollow, near Valmeyer, Illinois and along the bluffs of the Missis- sippi River. TAXONOMY OF MESHWORK FENESTRATE BRYOZOA GENERAL TAXONOMIC DIVISIONS OF THE BRYOZOA This paper deals taxonomically with members of one suborder of the classic Order Cryptostomata Vine, 1884, the Fenestelloidea Astrova and Morozova, 1956. The other two suborders of cryptostomes, the Rhab- domesoidea Astrova and Morozova, 1956, and Ptil- odictyoidea Astrova and Morozova, 1956, are not cov- ered. McNair (1937) divided the cryptostomes into three morphologic groupings: fan-shaped and pinnate uni- laminate forms, dendroid forms, and bifoliate forms. He stressed these were neither taxonomic nor phylo- genetic groupings. Astrova and Morozova (1956) used these divisions to establish three suborders: the Fe- nestelloidea, Rhabdomesoidea, and Ptilodictyoidea. Elias and Condra (1957) removed the fenestrates com- pletely from the cryptostomes, making them a separate order. Their primary argument was an inferred ho- mology between the unlaminated granular calcite layer of the fenestrates (the “colonial plexus”) and the zone of budding in modern stenolaemates, the so-called “common bud” of Borg (1926). This amounts to a return to Vine’s (1884) original concept of Cryptosto- PALAEONTOGRAPHICA AMERICANA, NUMBER 57 mata and away from Ulrich’s (1890) concept. Elias and Condra also suggested that the fenestrates were ances- tors to the Cheilostomata Busk, 1852, using the loss of “colonial plexus” in cheilostomes as the event mark- ing the transition between the two groups. Waters (1891) concluded that if the fenestrates were ancestral to the cheilostomes, a missing link between Paleozoic and Cenozoic forms might be evident during Mesozoic, possibly in a family such as the Melicerititidae d’Or- bigny, 1852. Workers with Mesozoic bryozoan faunas (Levinsen, 1925; Marcus, 1924) attempted unsuccess- fully to recognize a connection between the fenestrates and cryptostomes and the Melicerititidae. Shishova (1968) accepted an ordinal ranking for the fenestrates, with taxonomic emphasis placed on zooecial shape, budding pattern, microstructure, and accessory fea- tures such as peristomes, lunaria, and ovicells. Shishova (1968) also elevated the rhabdomesoids from subordinal (Astrova and Morozova, 1956) to or- dinal rank. This left the bifoliates as the only major group in the Order Cryptostomata, a concept now high- ly altered from those of both Vine (1884) and Ulrich (1890). Numerous workers have taken exception to the or- dinal divisions of the classic cryptostomes. Tavener- Smith and Williams (1972), using microstructural skel- etal considerations, adhered to Astrova and Morozo- va’s subordinal placement. Cuffey (1973), using cluster analysis, found the three “orders” of cryptostomes grouped together, away from the Trepostomata Ulrich, 1882. Based on his work, Cuffey developed a strong argument for retention of the classic Cryptostomata. In a comprehensive study, Blake (1975) supported the subordinal ranking of the fenestrates, rhabdome- soids, and ptilodictyoids, basing his interpretations on the similarities in skeletal development, budding pat- terns, zooecial and zoarial shapes, and overall sym- metry between the suborders. His subordinal divisions are based on such characters as presence of ovicells in fenestellids, vesicles in bifoliates, and metapores in rhabdomesoids. The taxonomic placement of phylloporinids has been somewhat controversial, but strong morphologic sim- ilarites suggest apparent close phylogenetic relation- ships between the Phylloporinidae Dunaeva and Mo- rozova, 1974 and the fenestrates. Ulrich (1890) and Shulga-Nesterenko (1960) placed the phylloporinids with the Fenestelloidea because of their microstruc- ture, whereas Bassler (1953) placed them with trepo- stomes, due to their elongate zooecia. Characters phyl- loporinids share with the Fenestellidae, reported by Ulrich (1890), Shulga-Nesterenko (1960), and Ross (1964), were used as strong criteria justifying their tax- onomic placement in the Fenestellidae. Blake suggest- ed probable derivation of the fenestellids from the MISSISSIPPIAN BRYOZOANS: SNYDER 17 Phylloporinids, with differences between the two fam- ilies being a function of degree rather than of kind. Earlier, Dunaeva and Morozova (1974) removed the Phylloporinidae from the Fenestelloidea, citing as cri- teria the difference in zooecial shapes as well as the presence of “specific heterozooids" and the absence of Ovicells in the phylloporinids. In my view, historical considerations [Vine (1884) ànd Ulrich (1890)], phylogenetic affinities [Blake (1975), numerical analyses [Cuffey (1973)], and poly- thetic character considerations [Ulrich (1890), Shul- 8a-Nesterenko (1960), Ross (1964), and Morozova (1962)] endorse retention of the classic Cryptostomata with the three suborders of Fenestelloidea, Rhabdo- Mesoidea, and Ptylodictyoidea: I have done so here. Such an arrangement stresses shared characters or sim- llarities rather than dissimilarities. Microstructural and/ or ultrastructural analyses of both fenestrates and rhab- domesoids indicate great similarities between these Suborders [a view greatly contrasting with that of Con- dra and Elias (1944), but concurring with those of Tav- ener-Smith and Williams, 1972, and Blake, 1975]. King (1849) established the Family Fenestellidae for anlike and pinnate Paleozoic bryozoans, including in P family Fenestella [type: F. antiqua Lonsdale, 1839], olypora, and Ptylopora McCoy, 1844, and two new &nera, Synocladia and Phyllopora. Zittel (1880) erect- ed a ay family for the pinnate forms, the Acantho- cladiidae. Vine (1884) subdivided King’s family Fe- oe into three families: the Fenestellidae, Olyporidae, and Diploporidae. A similar division was jus by Waagen and Pichl (1885), who subdivided es family Fenestellidae into three subfamilies: Fenes- inae, Polyporinae, and Goniocladiinae. Ulrich (1890, 1893) placed the fenestellids, acanthocladids, and polyporids within the cryptostomes [following the sea of King (1849)], stressing a polythetic classifi- m "on scheme and pointing out apparent phylogenetic si he among taxa. His extensive work on War- ^ ee has proven invaluable in this study. Many ie taxonomic subdivisions and faunal interpreta- Rs show remarkable insight when one considers the miques and equipment available at the time. Sub- co Of the Fenestellidae into three groups was fol- h ed in the work of Cumings (1904, 1905), who fur- d er investigated the primary stages of colony evelopment in Fenestella Lonsdale, 1839, and Poly- = ra McCoy, 1844. From his studies, Cumings con- uded that these genera should be assigned to different amilies, Vine (1884) established two of the dendroid en of cryptostomes: the Rhabdomesontidae (cor- “ted to Rhabdomesidea by Bassler, 1953) and the fay nasmoporidae. A third dendroid cryptostome ses, the Arthrostylidae, was proposed by Ulrich Overall similarity in symmetry and morphologic characters between the fenestellids and rhabdomesoids indicates a much closer affinity between these two groups than between them, either singularly or jointly, and the Trepostomata, Cystoporata, or Cyclostomata. Zooecial chambers in these two suborders are relatively short, highly symmetrical, and fixed in size and shape throughout the zoarium. Short symmetrical zooecia result in slender branches and delicate sheets and fans characteristic of the cryptostomes, contrasting with the commonly much more massive forms of the Treposto- mata and Cystoporata. Budding loci for the Crypto- stomata are restricted to one- or two-dimensional sur- faces (very rarely three dimensions for a few species) for members of this order as opposed to the two- and predominantly three-dimensional surfaces character- istic of the other stenolaemates. Blake (1980) argued that the cryptostomes are an evolutionary clade whose establishment resulted from evolution of this restricted locus, which allowed colonies to grow out rapidly into the water column without needing to fill large amounts of lateral space, as is observed in the trepostomes and cystoporates. Many accessory features are common within the suborders of the cryptostomes. Some ac- cessory features are also shared with the other orders, possibly as a result of homeomorphy, as illustrated by Blake in the rhabdomesoids and dendroid trepostomes. Such features include stylets, which are contin- uous with the internal granular layer that extends through the outer lamellar skeleton, both perforate and complete terminal diaphragms, and frequent symmet- rically placed hemisepta within the zooecial chamber. The fenestrates and rhabdomesoids also lack the re- generative cycles evident and often common in the trepostomes and cystoporates. Therefore, based on similarities in morphology, phy- logeny, and use of historical considerations, the Order Cryptostomata is retained in this study, with Fenes- telloidea grouped as a suborder under that order. SUMMARY AND CRITIQUE OF PREVIOUS APPROACHES TO THE TAXONOMY OF MESHWORK FENESTELLOIDEA Fenestrate bryozoans have been studied extensively since the mid-nineteenth century (Hall, 1847, 1852, 1857b, 1883, 1885; King, 1849, 1850; Lonsdale, 1839; McCoy, 1844; d’Orbigny, 1848-1852; Owen, 1838, 1842; Phillips, 1836, 1841; Prout, 1858a, 1858b, 1859, 1866; Vine, 1880, 1884, 1886). These authors pre- sented illustrations and descriptions only of specimen exteriors; Ulrich (1888, 1890), Nicholson and Lydek- ker (1889) and Poéta (1894) were apparently the first to publish thin-sectioned fossil Bryozoa. Ulrich (1890), in the most comprehensive work of the above, illus- trated numerous views of fenestellids and other bry- 18 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 ozoans, providing detailed description of microstruc- ture. Ulrich (1882, 1888, 1890, 1893) made major con- tributions to descriptive and laboratory techniques, primarily concerning himself with the Silurian (as then conceived in North America) and Carboniferous bryo- zoan faunas of the Upper Mississippi Valley and sur- rounding areas. Ulrich emphasized the need for thin- sections as an important aspect of faunal analysis, and developed large collections. Many of Ulrich’s remain- ing thin-sections are housed today at the U. S. National Museum of Natural History (Smithsonian Institution) and the Illinois State Museum. He also prepared and sold thin-sections to universities; some of these are still in collections at various institutions. Ulrich mounted his sections on windowpane glass taken from wrecked buildings in Washington, DC (Boardman, oral commun., 1978). In numerous publications, Ulrich il- lustrated thin-sections and exteriors, albeit at relatively low magnifications. He also recognized two micro- structural skeletal components of the fenestrates: the granular skeletal layer, which he referred to as “original basal or germinal plate”, and the lamellar skeletal layer called “subsequently added layers of calcareous tissue” (Ulrich, 1890, p. 352). He developed a diagnosis ar- rangement for the fenestrates that stressed almost all features considered important today. These include zooecial shapes, presence of a vestibule, presence of a well-developed, abruptly arising exozone, and pres- ence of hemisepta; zoarial form and maximum zoarial length; branch character and nature of bifurcation; dis- sepiment character and width; fenestrule shape, in- cluding length and width; keel development; nodal de- velopment and spacing; aperture shape, positioning on branch surface, and relative size; number of apertures per fenestrule and spacing along branch; and reverse surface characters such as supports, dissepiment ap- pearance and presence of longitudinal rows and stylets from external analysis. Lack of consideration of intra- specific variation is the primary weakness of Ulrich’s work from a modern point of view. A convention adopted by Ulrich to describe char- acters in terms of varying lengths in the proximodistal direction of branch growth has been adopted by many subsequent workers. These include branch bifurcations in 1 cm, fenestrules in 1 cm, nodes in 2 mm, and apertures in 5 mm. Nekhoroshev (1926) and later Con- dra and Elias (1944) refer to these characters as mesh- work formula (really a listing, rather than an integrated formula), whereas Miller (1961a; 1961b) and Termier and Termier (1971) use the name micrometric formula. The formula applied by these authors dealt with colony exteriors, ignoring interior analyses entirely. Use of the meshwork formula has been a prime contributing fac- tor in the extreme proliferation of species of Fenestella Lonsdale, 1839, because new species are based pri- marily on small quantitative differences. Thousands of species (Morozova, 1974) have been recognized through use of the meshwork or micrometric formula. Condra and Elias (1944) and Elias and Condra (1957) worked with the predominantly Carboniferous genus Archimedes Hall, 1858 of the central United States and Fenestella from the Permian of West Texas. In their work on Archimedes, they dealt primarily with two topics: the central axes and means of species recogni- tion. Further, they subdivided Archimedes into new species based almost exclusively on axial characteris- tics, which are primarily environmentally influenced. The effect of environmental influence is herein dem- onstrated by large coefficients of variation for the axis within species (Tables 37—40). Elias and Condra seem- ingly ignored mesh and zooecial characteristics in their analyses. Their approach to Fenestella resembled closely that of Ulrich (1890), and although strongly endorsing the use of thin-sections in bryozoan analysis, Condra and Elias used relatively few sections in their work. Standard meshwork formula measurements were applied and ranges were given, but no statistical anal- ysis substantiates their data. The number of measure- ments made from different colonies was not provided, although they did indicate that single specimens were available for some species. Elias and Condra illustrated tangential and transverse (cross-sectional) interior views along with zoarial exteriors. No longitudinal sections were employed and, consequently, accurate three-di- mensional reconstruction of the autozooecial chamber is not possible. The meshwork formula, as used commonly and pre- sented by Termier and Termier (1971) in their work on the upper Paleozoic of Afghanistan, appears as: a/b/c/d/e where a = range of number of branches in 10 mm; b = range of number of fenestrules in 10 mm; c = range of number of zooecia across the branch (two in the fenestellids [sometimes omitted in the formula]); d = range of number of zooecia in 5 mm; and e = range of number of nodes in 5 mm. Such a system records ranges, without providing a comprehensive system in which accepted statistical techniques used in compar- ing numerical data can be applied. Tavener-Smith (1965, 1966, 1973), working with Visean fenestrates from Ireland, rejected the meshwork formula because of this lack of statistical credibility. Tavener-Smith restricted his work to colony exteriors because the fauna in his study area was primarily si- licified. He greatly improved methods for analysis of fenestrate species by expanding the list of characters used and differentiating zooecial from zoarial charac- MISSISSIPPIAN BRYOZOANS: SNYDER 19 ters. His criteria include, in outline form: A. Zooecial features l. inter-apertural distance 2. branch width 3. apertural diameter 4. zooecial chamber shape and size B. Zoarial features . fenestrule length - fenestrule width - number of apertures per fenestrule . internodal distance . dissepiment width Cn 4 UUN- : Tavener-Smith emphasized the written description, including features such as purported three-dimensional Shape of the zooecia, aperture distribution at branch bifurcations, angle of newly formed branch, fenestrule Shape, aperture position relative to branch and dissep- Iment Surfaces, apertural features such as peristome, Tanch and dissepiment cross-sections, and reverse- wall striae. Even though Tavener-Smith recognized Problems in species recognition due to secondary thickening of exterior lamellar skeleton and other mor- Phologic changes during ontogeny, he apparently used Only exteriors in his analyses. Although much of the fauna he analyzed was silicified, he did indicate the Presence of non-altered specimens in his material. Ta- Yener-Smith's major contribution was the introduction ot a rigorous statistical approach, which included the Tange of specimen mean values, sample mean, stan- dard deviation, and coefficient of variation for all char- acters except apertures per fenestrule — which are ex- ics in the range of specimen modes — and f den of specimen modes. Other authors (Cuf- bus 967; Bork and Perry, 1967; Horowitz, 1968; An- ‚ey and Perry, 1970, 1973) started employing more oo Statistical analyses in their taxonomic works Tyozoa shortly after Tavener-Smith. + Possible use of the internal skeleton and associated Ooecial and zoarial features through thin-section anal- ee recognized by the late 1800’s (e.g., Ulrich, er : 1893). Although aware of the significance of in- = al features for taxonomic interpretation, no sub- ae workers until Nekhoroshev and Nikiforova, m “BR half of the twentieth century, made extensive m. Of thin-sections for bryozoan taxomomy. Their M to express variation within a species in nu- se form was an important contribution. Their dealt with Upper Paleozoic bryozoans of the - S. R.; Carboniferous bryozoans from the Altai, Uzbass, Kazakhstan, and Turkestan; and Permian ui rona from Bashkiria and Armenia, as well as east- 194 uropean materials. Nekhoroshev (1928, 1932, 9, 1953, 1956), Nikiforova (1933, 1935, 1938), hulga-Nesterenko (1936, 1941, 1949, 1951, 1952, 1955), Trizna (1939, 1950, 1958), and Trizna and Kautsan (1951) developed bryozoan faunas into useful biostratigraphic tools in the U. S. S. R. and surround- ing countries. Although more comprehensive in format than ear- lier works, the Soviet taxonomic approach possesses inherent problems stemming from the method of study. In Soviet fenestrate taxonomic work, tangential views are stressed, along with rare transverse views. Longi- tudinal views are essentially absent in Soviet studies of fenestrates. Further, there are few descriptions of Obverse or reverse surface exterior details, which may be due to poor preservation of zoaria. Such a taxo- nomic approach, although more complete than typical studies in the West, allow little or no more accurate analysis than is possible from strictly exterior-oriented studies. A combination of both interior and exterior analyses is necessary to accurately determine taxonom- ic affinities and accurately delimit species. This con- clusion is dealt with extensively on p. 22. Morozova (1962, 1970a, 1970b, 1973, 1974) studied fenestrate bryozoans and provided suggestions for ge- neric subdivisions of Fenestella in numerous taxonom- ic works. Her work represents the current Soviet ap- proach to species within the fenestrates. The eight main criteria for differentiation of species of Fenestella used by Morozova (1970b) are outlined in Table 2 along with the principal measurements taken; these were not listed by Morozova, but were compiled by the writer from her text. Morozova's approach, although including a greater number of measurements of characters, closely resem- bles that of Ulrich (1888, 1890). It differs from his work in recognizing a need for a more statistical ap- proach and the use of zooecial shape in middle tan- gential section (referred to as median section by Mo- rozova). Zooecial shape plays an important part in Morozova's specific and generic assignments of taxa. However, reconstruction of the zooecial chamber and, more importantly, three-dimensional chamber shape based only on tangential sections, is incomplete and misleading. Although this orientation is essential in chamber reconstruction, additional views are neces- sary, not only to accurately determine chamber shape and orientation relative to branch, but also to recognize various accessory features, such as inferior and supe- rior hemisepta. Banastella guensburgi, n. sp. (Text-fig. 3A) and Cub- ifenestella usitata, n. sp. (Text-fig. 3B) provide just two of many possible examples of how misleading it is to attempt to characterize internal anatomy of fenestrates based on mid tangential sections alone. Using mid tangential sections, as relied upon by Morozova, ex- treme similarity in zooecial chamber shape (arrow a) and only slight difference in size is evident between the 20 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 Table 2.—Descriptive criteria for differentiation of species of Fenestella used by Morozova (1970b). D = descriptive; M = measured (in mm). 1. mesh (regular or irregular) 2. branch a. width (narrow or wide) and depth (thin or thick) b. width c. distinctive changes in width (before or after bifurcation, or due to emplacement of accessory zooecia) 3. fenestrule . shape (oval, round, or polygonal) . alterations in shape due to zooecial projection into opening . length . width eanncep number in a 10 mm distance along colony 4. dissepiment a. width (narrow or wide) b. width 5. zooecia a. shape (in median [tangential] section) b. shape before and after a bifurcation c. number in a 5 mm distance along branch 6. apertural characteristics . degree and kind of projection into fenestrule £e length accessory features (e.g., peristome, lunaria, stylets), and positioning of these features width cano 22200 Zus Zu ZXEXZOO UU y peristome width 7. heterozooecia or polymorphs a. presence or absence b. dimensions 8. other characteristics a. carinae, nodes, and tubercules b. diameter of nodes and tubercules c. number of nodes and tubercules in a 1 mm distance Zs0 Xu two species; the ratios between length (arrow b) and width (arrow c) also appear moderately similar, as does placement of the autozooecial chamber within the branch. Some indication of different apertural-opening orientation (arrow d) is observed in shallow tangential section, although this is best presented in transverse section (arrow e), with apertures in C. usitata opening more into the fenestrule opening than apertures in B. guensburgi, whose opening approaches parallel to the obverse branch surface. Relying solely on tangential sections, we have two apparently similar species with similar chamber outlines, particularly in mid tangen- tial view. Comparing longitudinal and to a lesser degree, trans- verse sections of these two species, a much different conclusion is reached. A tangential section approxi- mately follows the line marked by arrow f in longitu- dinal sections of both B. guensburgi and C. usitata. This length corresponds approximately to the mea- surement of chamber depth (arrow g) in C. usitata, which in turn equals approximately the chamber length (arrow h) in this species. In B. guensburgi, however, the line marked by arrow f, which corresponds to arrow b in the tangential section, does not represent either depth (arrow g) or length (arrow h) of the autozooecial chamber. The apparent length of the chamber as rep- resented by the line marked by arrow f represents ap- proximately 1.7 times the chamber depth (arrow g) and approximately one-half the chamber length (arrow h). Sole reliance on the tangential sections for mea- surements of chamber length and width can provide accurate information in some species, such as C. usi- tata, but provides no information about depth. In other species such as B. guensburgi, the tangential section provides only accurate chamber widths, but extremely misleading information concerning chamber lengths. The angle subtended by the chamber’s lateral and reverse walls (arrow i) is the character which causes the difference in applicability of tangential section in the two species illustrated. When the reverse-wall bud- ding-angle approaches 90°, the length seen in tangential section will equal or closely approximate that seen in longitudinal section, as in the species C. usitata. In B. guensburgi, the reverse-wall budding-angle is quite low, approximately 38°, and thus the tangential section is of little use in determining chamber length. Although these two species appear similar in tangential section, a combination of sectional views demonstrates that differences between B. guensburgi and C. usitata are sufficient to justify assignment to different genera. Among genera, there are similar problems with re- verse-wall budding-angle, and the type, placement, and MISSISSIPPIAN BRYOZOANS: SNYDER 2 degree of development of hemisepta. Until rigorous analyses using all necessary zoarial views are applied to the meshwork Fenestelloidea, it will not be possible to accurately identify species, and to compare species from different geographic areas. Due to the problems in classification summarized elow, species of Fenestella and members of most of the meshwork Fenestelloidea have been difficult to rec- ognize. This difficulty has led to the proliferation of Species names and the inability of workers to agree on Phylogenetic affinities within genera. These difficulties Seem to result from: (1) lack of work with populations; (2 dependence predominantly on either incomplete evaluation of interiors or exteriors rather than a thor- ough combination of the two; (3) insufficient statistical analyses of material (which are needed to determine true range of variation of characters); (4) adherence to the meshwork or micrometric formulas and similar approaches that deal with range and pattern instead of form (Similarity in mesh pattern may be extreme, even between members of different genera.); (5) two-dimen- sional treatment due to overdependence solely on tan- gential sections in analyses [Three-dimensional con- siderations and reconstructions, particularly of zooecial chambers, such as that of McKinney (1980) in his ge- neric description of Utropora Pocta, 1894, have not generally been used.]; (6) lack of consideration of as- togenetic thickening as a factor causing pronounced variation in exterior zoarial morphology within a single species. LONGITUDINAL A TRANSVERSE eet TANGENTIAL TRANSVERSE LONGITUDINAL B _ Text-figure 3.— In chamber profil Comparison of interior sections of Banastella guensburgi (A) and Cubifenestella usitata (B), illustrating significant similarities € in tangential view and dissimilarities in longitudinal view. 2 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 A single taxonomic methodology can and should be employed throughout the Suborder Fenestelloidea. Within a species, members of the suborder exhibit pro- nounced similarity of certain zooecial characters, par- ticularly with regard to chamber size, symmetry, and accessory features. Such common traits offer an ideal basis on which to develop a uniform taxonomic meth- odology. Because all zooids of a zoarium, excluding the ancestrula, were reproduced asexually and have a single genotype, phenotypic variations within a single zoarium can be assumed to be due to other than genetic factors (Gautier, 1970, 1972; Boardman and Chee- tham, 1969, 1983; Cook, 1977). The advantage of the use of colonial animals for studies in variation, both ontogenetic and astogenetic, has been recognized by many workers, and was discussed in detail by Board- man and Cheetham (1969). Secondary calcification or addition of lamellar cal- cite commonly occurs within the fenestrates, as ob- served by Tavener-Smith (1973), Gautier (1972) and herein. This calcification continued during colony as- togeny, causing walls to thicken progressively from dis- tal to proximal positions within a zoarium. Tavener- Smith (1973) concluded, solely from exterior obser- vations, that such thickenings could be ignored if one carefully considered quantitative attributes. From my work, I believe this is incorrect, as I have found such thickenings affect branch and dissepiment width and thus fenestrule size, keel width, nodal appearance, ex- terior ornamentation on both the obverse and reverse zoarial surfaces, apparent aperture opening size, and peristomal thickness. This observation reduces greatly the value of six of the nine criteria of Tavener-Smith (1973): branch width, apertural diameter, fenestrule length, fenestrule width, internodal distance, and dis- sepiment width. Secondary thickenings of lamellar skeleton, at times enough to cover completely both obverse and reverse surfaces and completely fill fe- nestrule openings, suggest a structural response that increases colony strength. HISTORICAL REVIEW AND APPROACH TO TAXONOMIC DIVISIONS WITHIN THE FORM GENUS FENESTELLA LONSDALE Fenestrate bryozoans, and in particular the genus Fenestella, have long been recognized as major com- ponents of many Middle and Upper Paleozoic marine rocks. Many of the traditional genera are readily rec- ognized because they are based on such exterior char- acters as fan- and funnel-shaped colonies; distinct ob- verse and reverse sides; straight to undular branches; dissepiments connecting branches, forming voids or fenestrules between branches; two rows of apertures across the branch; and frequent presence of a carina, keel, nodes, or other accessory features (Nickles and Bassler, 1900; Bassler, 1953; Nekhoroshev, 1960). Pri- mary reliance on exterior analyses and provincial knowledge of literature have led to a great proliferation of species of Fenestella [over 1,200 to date (Morozova, 1974)] and extremely wide geographic and geologic ranges (Ordovician-Triassic): such ranges and abun- dance suggest the genus is heterogeneous. In 1890, Ulrich, and later Nekhoroshev (1928), rec- ognized the probable polyphyletic nature of Fenestella. These conclusions were based on exterior and thin- section analyses of transverse and tangential views in the case of Ulrich, and predominantly on tangential thin-sections in the case of Nekhoroshev. Both workers observed highly varied internal arrangement and struc- ture for species which fit readily the then-current con- cept for the exterior of Fenestella. Neither Ulrich nor Nekhoroshev subdivided the genus, possibly to retain its usefulness for exterior recognition in the field. Despite Ulrich's emphasis on a combination of both exterior and thin-section analyses for all bryozoan gen- era, many subsequent workers have relied on either interior or exterior analysis alone for taxonomic as- signments. Species based only on exterior analysis (e.g., Utgaard and Perry, 1960; Miller, 1961a; Campbell, 1961; Tavener-Smith, 1973), and new genera separat- ed from Fenestella but based solely on exterior analysis (Fenestrellina d'Orbigny, 1849; Flabelliporina Simp- son, 1895a; Fenestrapora Frederiks, 1915; Cervella Chronic, 1949; Parafenestella Miller, 1961b; Levife- nestella Miller, 1961a, Dogaddanella Ganesan, 1972; Polyfenestella Bancroft, 19862) are difficult to recog- nize beyond the types. Taxonomy based solely on exterior characters (En- gel, 1975) is justifiable where, due to poor preservation, only exterior views are available; however, general ap- plications of such studies are limited. Soviet workers, including Nekhoroshev (1928, 1932, 1949, 1953, 1956), Shulga-Nesterenko (1941, 1949, 1951, 1952, 1955), Morozova (1962, 1970a, 1970b, 1973, 1974), and others have done extensive work with interior microscopic analyses of species of Fenestella. Their early recognition of the extreme importance of autozooecial shape in both species and genus deter- mination was a major contribution; however, their use of only cross-sectional (tangential) views of the cham- ber has resulted in much confusion of taxonomic as- signment in the literature. This problem is discussed in detail on p. 30 in the context of a revised generic classification scheme. Taxonomic decisions based al- most exclusively on interior analyses are nearly as se- riously in error as those based only on exteriors, for they too ignore a great deal of available information. Crockford (1944), working with Permian materials from Australia, separated the genus Minilya Crock- ford, 1944, from Fenestella. In her work, Crockford used triangular cross-sections of the autozooecial MISSISSIPPIAN BRYOZOANS: SNYDER 93 chambers and alternating biserial arrangements of ca- rinal nodes as criteria for separation. Wass (1966) re- jected Minilya after his discovery of monoserial and biserial nodes on the same branch in two species as- sumed to belong to this genus. Morozova overturned Wass’s conclusions, resurrecting Minilya based on her Observations that Wass’s analysis was “mistaken and connected with inadequate conditions of the material investigated by him.” (Morozova, 1974, pp. 176-177). Triangular chamber shape, two rows of alternating nodes on a broad low carina, square fenestrule shape, and thin straight dissepiments are Morozova’s main criteria for delimitation of this genus. Although Mo- TOzOva's retention of the genus Minilya appears correct based on analysis of Warsaw materials, a more thor- Ough justification both descriptively and numerically would be of great assistance to other workers. Elias and Condra (1957), in a study of species of Fenestella from the Pennsylvanian of the midcontinent and the Permian of West Texas, argued that the genus was of polyphyletic origin. They divided the species of Fenestella studied into three sections or groups and thirteen subgroups. Group divisions were based on the following criteria: length of fenestrules, apertures per fenestrule length, and node distribution. The three groups include: (1) species with long fenestrules, 3.5 to 5.0 autozooecial apertures per fenestrule, and a single Tow of nodes; (2) species with long and short fenestrules and a double row of nodes; (3) species with short fe- hestrules, 2.0 to 3.5 autozooecial apertures per fenes- trule, and a single row of nodes. The thirteen subgroups are divided on criteria ranging from chamber shape to number of zooecia per fenestrule, branch width, zoarial Shape, and carinal development. Besides applying a Primarily monothetic approach, the divisions of Elias and Condra (1957) are difficult to use because they employ few characters, and those used are not applied equally to all taxa (some involve interior chamber shape, others involve exterior features such as carina and even zoarial shape). Loculiporina Elias and Con- dra, 1957 is based on extremely poor material. Because there appear to be a relict superstructure and a mesh pattern similar to that of Hemitrypa Phillips, 1841, Loculiporina cannot be readily separated from Hem- itrypa on the basis of information provided by Elias and Condra. Their use of group and subgroup and nonadherence to accepted taxonomic hierarchy and divisions make their work extremely difficult to apply Or relate to earlier works. The genus Archaefenestella was proposed by Miller (1962), based on material from the Lower Silurian of England. His genus is distinguished by quadrangular Zooecial shape in tangential section and the presence : vesicular tabulae that intersect the zooecial cham- er. Termier and Termier (1971) recognized six new gen- era within the traditional Fenestella from the Late Pa- leozoic of Afghanistan. These genera include: Rhom- bofenestella, Aequifenestella, Alternifenestella, Spinofenestella, Rugofenestella, and Mirandifenestel- la. The Termiers based their genera primarily on the groups and subgroups of Elias and Condra (1957). Pri- mary emphasis on the micrometric formula and an inadequate descriptive section for their species deter- minations handicapped the Termiers’ conclusions. Type species were not designated for Aequifenestella or Rugofenestella, nor were diagnoses presented for any of the proposed genera. The short descriptions presented and the lack of throrough analysis make the Termiers’ work of limited value. Morozova (1974) acknowledged the heterogeneous nature of the traditional form genus Fenestella and subdivided it, retaining five established genera and es- tablishing nine new genera, respectively: Archaefenes- tella Miller, 1962, Mirifenestella Morozova, 1974, Laxifenestella Morozova, 1974, Exfenestella Moro- zova, 1974, Fabifenestella Morozova, 1974, Flexife- nestella Morozova, 1974, Rarifenestella Morozova, 1974, Rectifenestella Morozova, 1974, Spinofenestella Termier and Termier, 1971, Minilya Crockford, 1944, Alternifenestella Termier and Termier, 1971, Ignoti- fenestella Morozova, 1974, Cavernella Morozova, 1974, and Permofenestella Morozova, 1974, as well as retaining Fenestella Lonsdale, 1839. Believing “Fen- estella consists of a large number of natural groupings of species that are connected by common origin and developed independently in different stages of the Pa- leozoic", Morozova (1974, p. 169) interpreted all her genera as phylogenetically linked groupings of species, many of which closely follow the inferred phylogenetic branchings of Shulga-Nesterenko (1951). Extreme differences in internal structure in zoaria, with mesh of nearly identical shape and structure, were inter- preted by Morozova (1974, p. 169) as proof that “Fen- estella” form species “arose independently in many genera of the family Fenestellidea,” evidently as a re- sult of parallel evolution. Internal characteristics of the autozooecial chamber are stressed in her analyses, although she attempted to determine chamber shape from tangential section alone. Morozova’s new genera are each based on the presence of a distinctive polymorphic type, with different poly- morphs found in different genera. This often highly monothetic approach yields an apparent pattern of much parallel evolution. Examples of types of heter- ozooecia include the “‘parazooecia’’ used to delimit Mirifenestella, “cyclozooecia” delimiting Ignotifenes- tella, “caverns” delimiting Cavernella, and “micro- zooecia” delimiting Permofenestella (Morozova, 1974; pp. 170, 177, 178). Table 3.—Characters used by Morozova (1974) for discrimination of PALAEONTOGRAPHICA AMERICANA, NUMBER 57 10 genera from the form genus Fenestella, here also applied to four genera of other authors. — = character absent or lacking in description. Spinofenestella Alterni- Termier and Minilya fenestella Ignoti- Fenestella Archaefe ll Mirife ll Termier, 1971 Crockford, 1944 Termier and fenestella Lonsdale, 1839 Miller, 1962 Morozova, 1974 [Lower [Lower Termier, 1971 Morozova, 1974 [Lower Silurian- [Lower [Middle Devonian- Devonian- [Devonian- [Lower Car- Permian] Silurian] Devonian] Lower Permian] Lower Permian] Lower Permian] boniferous] 1. colony mesh type — mesh-like — firm mesh medium fine regular, mesh — coarse mesh mesh usually fine 2. branch width and wide thin (straight) very broad straight, thick, relatively broad straight, thin straight shape broad 3. dissepiment thin thin very broad comparatively thin thin thin width and shape slender 4. number of rows two rows regu- two rows qua- two rows regu- two rows trian- two rows trian- one row in two rows, pen- of zooecia in lar quadran- drangular lar quadran- gular, trian- gular, trian- deep cross- tagonal and deep cross-sec- gular gular gular-pentag- gular-pentag- section, tra- rounded pen- tion and zooecial onal before onal before peziform or tagonal shape in median bifurcation bifurcation triangular- cross-section trapeziform 5. presence or ab- single straight straight, narrow high, straight narrow and broad and low thin low sence of carina, narrow cari- high their size, shape, na and emplacement 6. presence or ab- monoserial — — monoserial row biserial row of monoserial row monoserial row sence of nodes, small nodes of nodes on alternating of nodes on of nodes on their relative size, or carina carina nodes on ca- carina carina location, and em- rina placement 7. presence or ab- — monoserial tu- — — — — — sence of tuber- bercules cles, and their size and location 8. presence or ab- present — — — — — — sence of inferior and/or superior hemisepta 9. presence or ab- — present, inter- — _ — — — sence of vesicular sect zooecial diaphragms cavities 10. presence or ab- — — parazooecia — — — “cyclozooecia” sence of hetero- on branch, zooecia and on inter- val between adjacent zooecia Table 3 summarizes the ten characters Morozova used for generic differentiation ofthe form genus Fen- estella and lists the genera recognized with their re- spective characters. Rather than providing discrete measurements or indicating presence or absence, Mo- rozova applied descriptive modifiers to her characters. As opposed to giving an indication of presence/absence or of measurements and, as illustrated in the Table, those modifiers are frequently applied inconsistently. These problems led to descriptive ambiguities throughout her work. No definite means of comparison are given for such relative terms as thin, wide, fine, and coarse. For example, in two genera (Mirifenestella and Flexifenestella), the mesh is described as “firm”; it is not clear how this term fits in a scale of fine, medium, and coarse. Three genera (Alternifenestella, Cavernella, and Permofenestella lack any modifiers whatsoever concerning mesh type. Confusion of mesh symmetry and relative geometric placement of branch- es and dissepiments with mesh sturdiness or firmness could be a problem arising from translation of the original work into English from Russian; deletion of descriptive comparisons presumably is not. Under branch width/shape, in some genera (e.g., Fenestella, Mirifenestella, Fabifenestella, Minilya, and Cavernella), only width is considered, whereas only shape is touched upon in others (e.g., Laxifenestella, Exfenestella, Rectifenestella, and Ignotifenestella). Similar problems can be observed in dissepiment width/ shape, carina size and shape, and hemisepta devel- opment (i.e., inferior or superior position). Criteria selected by Morozova for generic differen- tiation, other than those emphasizing heterozooecia, appear to have value for delimiting divisions within the traditional genus Fenestella. Lack of three-dimen- sional reconstruction of the autozooecial chamber se- verely limits the usefulness of any bryozoan taxonomic work, including Morozova’s. Further, chamber shape and related accessory features such as hemisepta and apertural stylets, as observed in the later section on | f f 1 I | MISSISSIPPIAN BRYOZOANS: SNYDER 25 Table 3.—Continued. Flexifenestella Rectifenestella Moni Laxifenestella are We 1974 Exfe ll. Fabifenestell Rarifenestella Morozova, 1974 1974 [Car- Permofenestella Morozova, 1974 [Lower Car- Morozova, 1974 Morozova, 1974 Morozova, 1974 [Upper boniferous— Morozova, 1974 [Devonian- boniferous- [Devonian- [Devonian- [Lower Silurian- Permian] [Permian] Permian] Lower Permian] Permian] Permian] Devonian] Permian] n — medium mesh firm mesh medium, fine firm, fine mesh medium mesh medium, fine mesh mesh moderately broad, straight straight or broad, undular straight or broad broad, straight straight road or weakly weakly bend- curves En i “in: curve moderately Pin Me: italy very short, re- straight straight very thin, straight broad ‘ broad duced : straight two rows, two rows, two rows, te- two rows, te- two rows, fabi- two rows, te- two TOWS, ver- two rows, pen- rounded pen- rounded pen- tragonal-pen- tragonal in form tragonal in miform tagonal, be- tagonal tagonal tagonal deep section, deep section, coming trian- tetragonal- fabiform near gular- pentagonal or surface pentagonal be- fabiform near fore bifurca- surface A tion low low slightly curved broad and low narrow and broad and low narrow and high present slender monoserial row monoserial row monoserial, large monoserial monoserial | two rows of al- single row of : monoserial row of nodes on of small small, fre- nodes on cari- nodes on cari- ternating : nodes on cari- of nodes on carina nodes on cari- quently on na na nodes on cari- na carina “caverns” on dorsal face of branches join With dissepi- ments na “microzooecia” in pairs, or singly be- tween ordi- nary zooecia carina on branches in two rows present on branches in two rows na Species, are highly constant within a species and have Significant application for generic level taxonomic comparisons. McKinney (1980), in his redescription of the De- Vonian fenestrate genus Utropora Pocta, 1894, clearly recognized and demonstrated the usefulness of three- dimensional chamber reconstructions when consid- ering generic descriptions and affinities. McKinney il- lustrated reconstructed general chamber form in lat- eral, frontal, and distal views. McKinney observed that if zooecial shape is to be clearly understood, shallow, medium, and deep tangential views cut parallel to the branch surface are all necessary, as are transverse and longitudinal sections. Fortunately, single sections can Provide more than one view; for example, an inclined tangential section over a large specimen provides shal- 9w, medium, and deep tangential views. In McKinney's work, comparison is made between the three-dimensionally reconstructed living chamber 9f Utropora nobilis (Barrande in Pocta, 1894) and the type species of Fenestella, Fenestella subantiqua d’Or- bigny, 1839. These reconstructions, along with detailed microstructural analysis showing relative position of granular and laminated skeletal material, offer great taxonomic potential. Unfortunately, although many of these ideas are well presented in the text of McKinney’s article, they are not directly applied in his amended diagnosis. Many characters presented by Morozova, as well as those of other earlier workers, are used in McKinney's diagnoses, and although three-dimension- al terminology is employed, the illustrations of cham- ber shape are not referred to therein. Such illustrations should be placed directly in the diagnosis to be of greatest value to subsequent workers. Positioning of the zooecial chamber relative to the branch orientation and other zooecia present, along with aperture posi- tioning along the branch, is included in McKinney’s analyses. These characters, neglected in the two-di- mensional approach of the Soviets, have proven of prime importance in delimiting subdivisions within the traditional genus Fenestella in this study. Bancroft (1986a) described the new fenestrate genus 26 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 Table 4.— Taxonomic criteria for generic divisions within the Warsaw fenestellids. See Table 7 for explanations of abbreviations. Character Groupings (External) I, III. IV. zoaria A. robustness (delicate [fragile, small colony fragments] ^ intermediate [moderately complete zoaria present] > robust [zoaria large, thick, resist abrasion]) . outward expansion (flat, obversely or reversely curved, undulating, cup-shaped, or spiralling from central axis) . mesh spacing (close [WF « WB] — intermediate [WF = WB] > open [WF > WB]) . mesh uniformity (regular! or irregular) . secondary features (e.g., central axis, reticulate meshwork) mogosgsy . branches A. width (narrow [<0.30 mm] > intermediate [0.30-0.39 mm] ^ wide [0.39 mm]) B. proximodistal trace (straight, sinuous, or broadly curved) C. surface profile on obverse surface (round, flat, or angular) D. keel (if present) 1. number across branch surface (single or multiple) 2. width (narrow [<0.05 mm] > intermediate [0.05-0.15 mm] > wide [70.15 mm]) 3. emplacement (straight or anastomosing) 4. astogenetic changes E. nodes (if present) 1. emplacement (monoserial or biserial) . size (small [40.07 mm] > intermediate [0.07-0.13 mm] > large [70.13 mm] . shape (circular, ovate, elliptical, or stellate) . location on branch 5. internode spacing (close [<0.24 mm] > intermediate [0.24-0.80 mm] > wide [>0.80 mm]) F. obverse stylets (if present) 1. size (small [<0.01 mm] > intermediate [0.01-0.02 mm] ^ /arge [70.02 mm]) 2. location on branch surface G. reverse microstylets (if present) 1. size (small [40.018 mm] > intermediate [0.018-0.026 mm] > large [70.026 mm]) 2. location on branch surface H. reverse macrostylets (if present) 1. size (small [40.05 mm] ^ intermediate [0.05-0.08 mm] > large [70.08 mm]) 2. location on branch surface L number of rows of autozooecia (two, two becoming three for a short distance proximal to branch bifurcations, or greater than two) J. heterozooecia (if present) 1. type (e.g., ovicells, parazooecia’, cyclozooecia?, caverns”, microzooecia?) dissepiments A. width (thin [<0.5 x WB] > intermediate [0.5 x WB - 1.0 x WB] > wide [>1.0 x WB]) B. length (short [WF < WB] > intermediate [WF = WB] ^ long [WF > WBJ]) C. placement (regular or variable) fenestrules A. size (small [length «0.4 mm; width «0.24 mm] > intermediate [length 0.4-0.9 mm; width 0.24-0.34 mm] ^ large [length 70.9 mm; width 70.34 mm]) B. shape (elliptical, ovate, rectangular, square, or circular) AUN . apertures A. relative size (small [length <0.09 mm; width «0.07 mm] > intermediate [length 0.09-0.15 mm; width 0.07-0.12 mm] > large [length >0.15 mm; width >0.12 mm]) . shape (circular, ovate, or elliptical) . orientation of opening relative to plane of obverse surface (parallel, inclined into fenestrule, or perpendicular) . peristomes (if present) (complete or incomplete) š . degree of development and emplacement of apertural stylets (if present) . terminal diaphragms (if present) 1. location on zoarium (e.g., proximal, middle, distal, throughout) "mgou ! Low coefficient of variation for length of fenestrule, width of fenestrule, and width of branch. ? fide Morozova (1974); not observed in Warsaw bryozoans. Polyfenestella from the Midland Valley of Scotland. type B zooecia occur on both the obverse and reverse Polyfenestella, derived from Synocladia(?) fenestelli- branch surfaces. formis Young, 1881, is primarily distinguished on the Exterior analyses only were employed in Bancroft’s basis of occurrence of two types of heterozooecia. Type work, with photographs of zoarial and zooecial features A zooecia occur irregularly between autozooecia and providing inadequate illustration. Bancroft recognizes MISSISSIPPIAN BRYOZOANS: SNYDER 27 Table 4.—Continued. Character Groupings (Internal) I. branches A. outline in cross-section (e.g., elliptical, ovate, circular, semicircular, rhombic, polygonal) B. branch depth (thickness of others) (shallow [<0.30 mm] ^ medium [0.30-0.39 mm] > thick [>0.39 mm]) U. autozooecial chambers A. size (small [length «0.20 mm; depth «0.10 mm; maximum width «0.10 mm; minimum width «0.07 mm] > intermediate [length 0.20-0.48 mm; depth 0.10-0.20 mm; maximum width 0.10-0.15 mm; minimum width 0.07-0.12 mm] > large [length 70.48 mm; depth >0.20 mm; maximum width >0.15 mm; minimum width >0.12 mm]) . emplacement (monoserial, biserial, or polyserial) . axial wall trace (e.g., straight, sinuous, zigzag) myuaw . outline . orientation of elongation (parallel to reverse wall, or parallel to proximal and distal lateral chamber walls) l. near reverse wall (triangular, rectangular, square, ovate, elliptical, circular, pentagonal, parallelogram-shaped, or diamond- shaped) 2. at mid chamber (triangular, rectangular, square, ovate, elliptical, circular, pentagonal, parallelogram-shaped, or diamond-shaped) 3. near obverse surface (triangular, rectangular, square, ovate, elliptical, circular, pentagonal, parallelogram-shaped, diamond- shaped, or bilobate) . vestibules (if present) FH 1. length (short [<0.06 mm] > intermediate [0.06-0.12 mm] > long [70.12 mm]) . lateral-wall budding-angle (mean and range) reverse-wall budding-angle (mean and range) microstructure 1. exterior lamellar skeleton a. thickness (thin, intermediate, or thick) b. secondary astogenetic thickening 2. interior granular skeleton a. thickness (thin, intermediate, or thick) b. secondary astogenetic thickening . three-dimensional form 27 EO Ze Sa . geologic range . degree of development and location of hemisepta (if present) (superior or inferior) outline (shown in Text-figure) in longitudinal, transverse, and tangential views . three- dimensional reconstruction (shown in Text-figure) in lateral, distal, and frontal views the need for zooecial chamber reconstruction, ultra- Structural analysis, and budding relationships as an essential part of a genus description; however, the in- terior analysis necessary to provide this information Was not done due to “lack of adequate material for sectioning” (Bancroft, 1986a, p. 106). Interior sections Must be provided in illustration and description of new genera, for without these little more is done than the establishment of more unrecognizable taxa. Bancroft (1986b), in a redescription of Hemitrypa hibernicia McCoy, 1844, employs interior sections and illustra- tions as well as measurements of autozooecial cham- bers, The thorough exterior and interior analyses in this work provide a much better model for bryozoan description, and a much more viable starting point for development of a format adequate for description of à new genus. . Based on analysis of Warsaw fenestellids, in con- Junction with other meshwork bryozoans, a list of cri- teria for generic division within the Suborder Fenes- telloidea has been established; these are listed in Table a along with modifiers and descriptors. Characters are adapted from the format used by McKinney (1980) for the genus Utropora, from Morozova's revision of the genus Fenestella, and from observations made on War- saw materials. Application of this format has proven successful in delimiting new genera within the form genus Fenestella, as well as confirming the validity of established genera, including Archimedes Hall, 1858, Hemitrypa Phillips, 1841, Polypora McCoy, 1844, Fe- nestralia Prout, 1858a, Rectifenestella Morozova, 1974, Laxifenestella Morozova, 1974, and Exfenestella Mo- rozova, 1974. The format adopted permits the addi- tion of new characters as discovered, and it provides the means for comprehensive comparison of morpho- types. Chamber form and orientation relative to the branch, as well as other chamber characters such as hemisepta and diaphragms, are highly consistent within these gen- era. In contrast, relative mesh size, branch and dis- sepiment dimensions and placement, chamber dimen- sions, and keel and node number and placement frequently show pronounced variation within any ge- nus. Recognition of Archimedes and Hemitrypa, as well as other fenestellid genera, can therefore be made from small zoarial fragments, based on similarities in overall chamber shape within members of their respective gen- era. 28 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 Table 5a.—Comparison of external taxonomic characters in 11 genera of fenestellid and polyporid bryozoans. Rectifenestella Minilya Exfenestella Morozova, 1974 Laxifenestella Crockford, 1944 Morozova, 1974 Banastella, (Late Silurian- Morozova, 1974 (Early Devonian- (Devonian- n. gen. Permian) (Devonian—Permian) Early Permian) Permian) (Mississippian) 1. Zoaria A. robustness delicate to interme- intermediate intermediate to ro- robust delicate to ex- i B. outward expansion from ancestrula C. mesh type (spacing) D. mesh uniformity E. secondary features Branches A. width B. C. surface profile on obverse surface , keel 1 proximodistal trace . presence/absence 2. number 3. width 4. astogenetic changes . nodes ae . presence/absence 2. emplacement 3. size 4. shape wn . location on branch 6. internode spacing . obverse stylets 1. presence/absence 2. size 3. location on branch surface . reverse microstylets 1. presence/absence 2. size . reverse macrostylets 1. presence/absence 2. "size 3. location on branch surface number of rows of autozooecia heterozooecia 1. presence/absence 2. type diate flat to slightly ob- versely curved close to intermedi- ate regular to irregular narrow straight to curved round to moderate- ly flat present single narrow to interme- diate width increasing, covering aper- tures present monoserial intermediate circular to ovate middle of keel close present small across obverse sur- face typically present small to intermedi- ate present in some species small to intermedi- ate atop striae two rows present in some species possible ovicells flat to obversely curved close to intermedi- ate extremely regular narrow to wide straight, sinuous, or curved round to flat present single narrow width increasing, covering aper- tures present monoserial intermediate to large circular to ovate middle of keel in single alternating row close to intermedi- ate present small to extremely small across obverse sur- face present small to large present in some species large typically at branch- dissepiment junc- tions two, rarely three rows proximal to branch bifurca- tion present in some species possible ovicells bust flat to slightly ob- versely curved intermediate regular to irregular narrow straight, sinuous, or curved rounded present single narrow width increasing, covering aper- tures present or absent monoserial intermediate ovate middle of keel close present extremely small to intermediate across obverse sur- face present extremely small to small present in some species large typically at branch- dissepiment junc- tions two rows none observed obversely curved intermediate extremely regular narrow straight, sinuous, or curved rounded present single intermediate width increasing, covering aper- tures present monoserial intermediate circular to ovate atop keel close present small across obverse sur- face present extremely small present large typically at branch- dissepiment junc- tions two rows none observed tremely robust flat, obversely or reversely curved, sinu- ous, or cupped close to open regular to irregu- lar intermediate to extremely wide straight, sinuous, or curved rounded to angu- lar present single or multiple narrow to wide width moderately to greatly in- creasing, cover- ing apertures present monoserial large to interme- diate stellate or ellipti- cal middle of keel intermediate to wide present or absent small to interme- diate across obverse surface, on keel edge present small to interme- diate absent two rows, three rows proximal to branch bifur- cation present possible ovicells Comparison with and adherence to already estab- lished genera is done wherever possible. Because most previous work, excluding that of McKinney (1980), has dealt with genera based on either solely exterior or two- dimensional interior interpretations, application of these works to a more modern three-dimensional ge- Table 5a. — Continued. MISSISSIPPIAN BRYOZOANS: SNYDER 29 Archimedes Polypora Cubifenestella, Hemitrypa Hall, 1858 Fenestralia McCoy, 1844 n. gen. Apertostella, n. gen. Phillips, 1841 (Mississippian— Prout, 1858a (Ordovician— (Mississippian) (Mississippian) (Silurian—Permian) Permian) (Mississippian) Permian) intermediate to robust delicate to robust delicate to robust delicate to robust robust robust flat to obversely or re- versely curved intermediate to open regular to irregular narrow to intermediate Straight, sinuous, or curved round or angular present Single Intermediate to wide Pronounced thickening Present monoserial large to intermediate Stellate, ovate, or circu- lar middle of keel intermediate Present Intermediate across obverse surface and in rows between nodes Present Small to intermediate Present in some species large typically at branch— dissepiment junc- tions two rows Done observed flat, undulating, or ob- versely curved close to intermediate regular intermediate to wide straight, sinuous, or curved flat, angular, concave, or obversely curved present single narrow to intermediate slightly thickening, covering apertures present monoserial intermediate to large ovate to circular middle of keel intermediate to wide present or absent large across obverse surface present small to large present in some species large typically at branch-dis- sepiment junctions two rows, three rows proximal to branch bifurcations none observed flat, undulating, or curved close to intermediate regular or irregular reticulate meshwork narrow to intermediate straight, sinuous, or curved rounded to angular present single intermediate pronounced, forms re- ticulate meshwork present monoserial intermediate stellate, ovate, or circu- lar middle of keel close to intermediate present small to intermediate across obverse surface present intermediate to large present in some species intermediate to large at branch-dissepiment junction or irregular- ly across surface two rows, three to four rows proximal to branch bifurcations present in some species possible ovicells cup-shaped to fan- shaped close regular tightly coiled axis narrow to intermediate straight on obverse, Sinuous on reverse surface flat to round present single narrow becoming covered by lamellar skeleton present monoserial small to intermediate circular, ovate, or stel- late middle of keel close to intermediate present small across obverse surface present small absent two rows, three rows proximal to branch bifurcations present in some species possible ovicells flat to obversely curved close to open irregular wide straight, sinuous, or curved rounded present single intermediate thick, covering aper- tures present monoserial large ovate or elliptical middle of keel intermediate present intermediate across obverse surface present small absent four rows, five to six rows at and proxi- mal to bifurcation present possible ovicells flat to cupped close to open regular or irregular wide straight, slightly sinu- ous, or curved round, angular, or flat absent present or absent monoserial intermediate to large stellate or ovate straight to anastomos- ing rows intermediate to wide present or absent intermediate to large in rows, or across ob- verse surface present or absent intermediate to large present or absent large atop striae or at branch-dissepiment junctions three to five rows, five to seven prox. to branch bifurcations present or absent possible ovicells Neric approach has proven difficult or impossible, par- ücularly in regard to the work done by Morozova, Whose material is accessible only if one can arrange and afford to travel to Moscow. Eleven meshwork fenestellid genera are recognized in the Warsaw: nine genera from the Family Fenestel- 30 Table 5a.—Continued. PALAEONTOGRAPHICA AMERICANA, NUMBER 57 Rectifenestella Minilya Exfenestella Morozova, 1974 Laxifenestella Crockford, 1944 Morozova, 1974 Banastella, (Late Silurian- Morozova, 1974 (Early Devonian- (Devonian- n. gen. Permian) (Devonian-Permian) Early Permian) Permian) (Mississippian) 3. Dissepiments A. width thin to intermediate intermediate thin to intermediate intermediate thin to wide B. length short to intermedi- short to intermedi- short to intermedi- intermediate short to long ate ate ate : C. placement regular regular to irregular regular to variable regular regular to variable 4. Fenestrules A. size small to intermedi- small to intermedi- intermediate intermediate intermediate to ate ate large B. shape rectangular, ellipti- ovate, elliptical, or rectangular, ellipti- elliptical, rectangu- elliptical, ovate, cal, square approximately cal, or ovate lar, or ovate rectangular, or rectangular square 5. Apertures A. relative size small to intermedi- small to intermedi- small to intermedi- small large ate ate ate B. shape circular to ovate circular to ovate circular circular to rarely circular to ovate ovate C. orientation of opening to plane parallel, to inclined parallel parallel, or inclined parallel, to inclined parallel, to in- of obverse surface into fenestrules into fenestrules into fenestrules clined into fe- nestrules D. peristomes 1. presence/absence present present present present present 2. completeness complete or incom- complete or incom- incomplete complete complete plete plete E. apertural stylets 1. presence/absence present absent present, of two sizes present present or absent 2. emplacement within the peristo- = small in peristomal extension of peri- extension of peri- mal gap gap, two large stomal edge stomal edge ones at adaxial- abaxial apertural edge F. terminal diaphragms 1. presence/absence present present present present present 2. location on zoarium proximal proximal proximal proximal and mid- proximal and dle throughout lidae, including Rectifenestella Morozova, 1974; Lax- ifenestella Morozova, 1974; Minilya Crockford, 1944; Exfenestella Morozova, 1974; Banastella, n. gen.; Cubifenestella, n. gen.; Apertostella, n. gen.; Hemitrypa Phillips, 1841; and Archimedes Hall, 1858; and two genera from the Family Polyporidae: Fenestralia Prout, 1858a; and Polypora McCoy, 1844. Tables 5a and 5b list these genera and their character descriptors. The genera are listed in order of character similarity, which is interpreted to represent phylogenetic positioning of genera relative to each other. In analysis and description at the genus level, a broad set of characters should be applied for taxonomic dif- ferentiation. Some generic characters may show little or no variation throughout the genera (as presence/ absence of obverse stylets) or may exhibit overlap of character size ranges (as frequently overlapping in fe- nestrule opening size or autozooecial chamber size), whereas others such as hemiseptum type and placement may be highly characteristic of a genus. To delete char- acters from a generic list because little variation is observed between genera is to invite misapplication of generic criteria, should variation in these characters occur in genera not considered within this faunal study. Deletion of viable characters solely because they do not allow ready taxonomic breaks based on variation between taxa is inviting establishment of a monothetic classification. Characters used in this study are those traditionally used in the literature, with the addition of increased emphasis on three-dimensional recon- struction of the chamber (Table 3). Numerical statis- tical approaches have not been applied in this study; however, it is hoped that by dealing with a broad, but significant generic character base, a truly polythetic classification scheme is developed. Table 6 presents a key that can be used for generic assignment. It must be emphasized that a key of this nature, although useful in direction, should not be con- sidered adequate or sufficient for generic determina- tion, but merely useful as a guide. Once a genus has been assigned, a thorough review of all generic char- acters within that genus should be undertaken to ac- curately determine generic assignment. A key of this nature, and the very nature of keys, causes a trend toward development of monothetic classification. Properly applied, however, a key is a strong and useful directional device. Zooecia frequently exhibit morphologic features that are characteristic of a single genus; zoaria frequently exhibit broadly overlapping morphologic features that may be found in different genera. For this reason, Ta- bles 5a and 5b are based almost solely on zooecial Table 5a.—Continued. MISSISSIPPIAN BRYOZOANS: SNYDER 31 Archimedes Polypora Cubifenestella, Hemitrypa Hall, 1858 Fenestralia McCoy, 1844 n. gen. Apertostella, n. gen. Phillips, 1841 (Mississippian- Prout, 1858a (Ordovician- (Mississippian) (Mississippian) (Silurian-Permian) Permian) (Mississippian) Permian) intermediate thin to intermediate intermediate intermediate intermediate thin to intermediate intermediate to long short to intermediate short to intermediate short intermediate short to long regular or variable regular regular to variable regular regular regular to irregular intermediate to large small to large small to intermediate intermediate intermediate to large intermediate to large elliptical, ovate, rectan- gular, or polygonal small to large Ovate slight to pronounced inclination into fe- nestrule Present or absent complete where present present extension of apertural edge fused Present Proximal throughout rectangular, elliptical, or ovate intermediate ovate parallel or slightly in- clined into fenestrule present complete present or absent on extension of peri- stomal edge present or absent proximal rectangular on obverse, square, or polygonal on reverse surface intermediate to large elliptical, ovate, or rarely circular parallel, or inclined slightly into fenes- trules present complete absent present proximal elliptical on obverse, elliptical, ovate, cir- cular, or square on reverse intermediate circular, ovate, or ellip- tical elliptical to ovate intermediate circular to ovate ovate, circular, rectan- gular, parallelogram- shaped, elliptical, or polygonal intermediate to large ovate, elliptical, or cir- cular parallel adaxially parallel, adaxially parallel, abaxially perpendic- abaxially perpendic- ular ular or inclined into fenestrule present present present incomplete complete complete or incom- plete present or absent absent present on extension of peri- — on edge of peristome stomal edge present present present proximal and near cen- throughout proximal, to through- ter of axis out characters, with zoarial characters used only where such Characters are highly diagnostic of a particular genus. Establishing a generic taxonomic approach to any group of organisms based on the faunal assemblage from only a single area or stratigraphic interval has Certain inherent risks, the dominant one being that the faunal assemblage analyzed is not characteristic of the froup as a whole. This is apparently not the case in the Warsaw, where the fauna is typical of equivalent Valmeyeran age materials and environmentally similar assemblages. Using a fenestrate fauna as rich and diverse as that of the Warsaw provides a starting point from which comparison with other similar faunas can develop, and an opportunity for establishing genera which have a thorough three-dimensional, statistically sound basis. BIOLOGICAL SIGNIFICANCE OF ZOOECIAL CHAMBER SHAPE A direct link between soft part morphology and 200ecial shape in fenestrates is strongly indicated by Xtreme consistency of zooecial chamber shapes and dimensions within conspecific populations. a Boardman and Cheetham (1969) and Gautier (1970), In work with Paleozoic trepostomes, suggested a floor for the living chamber could have been provided by solid or perforate diaphragms, although the length of the chamber between these diaphragms and the colony surface is commonly variable, even within a single colony. Silen and Harmelin (1974) observed wide vari- ability of peristome length of functioning zooids in modern cyclostomes, whereas Boardman (1975) ob- served high variability of soft part morphology in mod- ern bryozoan colonies. Blake (1980) suggested that the very long zooecia of trepostomes need not mean rel- atively very long polypides, emphasizing the construc- tional needs of the zoarium over differences in devel- opment in the polypide and related organs. Blake (1983) argued for a unified Cryptostomata based on the basic constancy in chamber size and shape in members of this order. My work with populations of numerous species of fenestrates and rhabdomesoids agrees with that of Blake, indicating that constancy of chamber shape and dimension in the cryptostomes relates directly to the polypide size and form, a relationship not observed in trepostome studies (see Tables 10-46, showing species dimensions and variability). Consistency of chamber dimensions (with resultant low coefficients of varia- tion) and shape, however, indicate greater need for constancy of size and form than would be needed sim- ply to satisfy structural constraints. Once formed, 32 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 Table 5b.—Comparison of internal taxonomic characters in 11 genera of fenestellid and polyporid bryozoans. Rectifenestella Morozova, 1974 (Late Silurian- Permian) Laxifenestella Morozova, 1974 (Devonian-Permian) Minilya Crockford, 1944 (Early Devonian- Early Permian) Exfenestella Morozova, 1974 (Devonian- Permian) Banastella, n. gen. (Mississippian) 1. Branches A. outline in cross-section B. branch depth (thickness of others) 2. Autozooecial chambers A. size B. emplacement C. axial wall trace D. orientation of elongation E. outline 1. near reverse wall 2. at mid chamber 3. near obverse surface F. vestibules 1. presence/absence 2. length G. hemisepta 1. superior a. presence or absence b. development and location 2. inferior a. presence or absence b. development and location H. lateral-wall budding-angle (mean and range) ul reverse-wall budding-angle (mean and range) J. microstructure 1. exterior lamellar skeleton a. thickness b. secondary astogenetic thickening 2. interior granular skeleton a. thickness b. secondary astogenetic thickening K. three-dimensional form ovate, elliptical, circular, or semicircular shallow to medi- um small to interme- diate biserial sinuous to zigzag parallel to reverse wall triangular to irreg- ularly pentago- nal triangular to irreg- ularly pentago- nal bilobate-elliptical present short to long present poor to interme- diate absent 23°-30° (means) 68°-71° (means) thin moderate to pro- nounced thin to intermedi- ate none moderately to highly cuneate circular to ovate shallow to thick intermediate biserial straight to sinuous parallel to reverse wall irregularly ovate or elliptical rectangular, paral- lelogram- shaped, irregu- larly pentago- nal, or elliptical bilobate-elliptical or bilobate- ovate present short to long present moderately to well-developed present well-developed on mid reverse, and proximal walls 20°-27° (means) 57°-77° (means) thin to thick moderate to pro- nounced intermediate to thick none box to rounded box with inden- tations circular to ovate thick intermediate monoserial zigzag parallel to reverse wall triangular triangular or ir- regularly pen- tagonal irregularly ellipti- cal present short to long present poorly to well-de- veloped absent 22°-25° (means) 74°-89° (means) thick pronounced thick slight cuneate circular to ovate medium intermediate biserial sinuous parallel to proxi- modistal cham- ber axis asymmetrical dia- mond-shaped asymmetrical par- allelogram- shaped or rect- angular bilobate-elliptical present intermediate present moderately well- developed present well-developed on proximal side 25° (mean) 71° (mean) thick moderate thin none rectangular box with indenta- tions circular, ovate, or elliptical shallow to thick typically large, less commonly inter- mediate biserial straight to slightly sinuous parallel to proxi- modistal lateral chamber wall triangular, irregu- larly pentagonal, to ovate irregularly rectan- gular, parallelo- gram-shaped, to irregularly pen- tagonal irregularly ovate to elliptical present short to long typically absent, present in one species short, on proximal vestibular edge absent 16°-22° (means) 22°-55° (means) thin to thick slight to pro- nounced thin to thick slight irregular to slightly irregular rectan- gle to parallelo- gram chambers exhibit minimal or no internal thickening by addition of lamellar or granular skeletal material. Highly symmetrical placement and often elaborate shapes of superior and inferior hemisepta in the fe- nestrates (shown in Pls. 6, 8-10, 12, 13, 16, 17) divide chambers in such ways as to suggest differential de- velopment of polypides among species. Uniform spac- ing of apertures along the branch, across the branch, and frequently between branches in many fenestrates and uniform closest packing of aperture centers in the rhabdomesoids reflect relatively symmetrical chamber positioning in both suborders. Symmetry of placement also indicates exploitation of a consistent area around the aperture opening for each lophophore and, there- fore, a constant size for this feeding organ. Constant number and regular placement of apertural stylets in Table 5b.—Continued. MISSISSIPPIAN BRYOZOANS: SNYDER 33 Cubifenestella, n. gen. (Mississippian) Apertostella, n. gen. (Mississippian) Hemitrypa Phillips, 1841 (Silurian—Permian) Archimedes Hall, 1858 (Mississippian— Permian) Fenestralia Prout, 1858a (Mississippian) Polypora McCoy, 1844 (Ordovician—Permian) ovate, elliptical, or cir- cular thick to medium intermediate monoserial or biserial Sinuous to zigzag depth and length of chamber approxi- mately equal triangular to ovate irregularly pentagonal to rectangular pentagonal, rectangu- lar, elliptical, square, or ovate Present Short to long absent absent 18°-37° (means) 648 1° (means) intermediate to thick Moderate to pro- nounced intermediate to thick moderate Tegular cubic to irregu- larly rectangular box polygonal, ovate, or el- liptical medium to thick intermediate biserial sinuous to zigzag parallel to reverse wall triangular, polygonal, or irregularly pentag- onal irregularly pentagonal, rectangular, to ellip- tical irregularly elliptical to ovate present short to intermediate absent absent 22°-25° (means) 67°-69° (means) intermediate to thick moderate to pro- nounced intermediate to thick none rectangular box circular, ovate, or ellip- tical medium to very thick intermediate biserial straight to sinuous parallel to reverse wall ovate, elliptical, irregu- larly pentagonal, to triangular irregularly pentagonal, rectangular, to paral- lelogram-shaped ovate to elliptical present short to long absent absent 17°-23° (means) 60°-77° (means) intermediate to thick moderate to pro- nounced intermediate to thick none irregularly rectangular to cubic box circular, ovate, or ellip- tical thin to thick small to intermediate biserial sinuous parallel to reverse wall irregularly pentagonal to triangular irregularly pentagonal irregularly elliptical to irregularly ovate present short to intermediate absent absent 20°-27° (means) 58°-70° (means) intermediate to thick moderate to pro- nounced intermediate to thick none slightly irregularly rect- angular box circular, ovate, or po- lygonal thick intermediate quadriserial straight adaxially, straight to sinuous abaxially parallel to proximodis- tal lateral chamber wall ovate irregularly pentagonal, rectangular, to paral- lelogram-shaped bilobate-ovate present intermediate present poor, on vestibular edge absent 17° adaxially, 51° abax- ially (means) 42° (mean) intermediate moderate intermediate none slightly irregular cylin- der elliptical, ovate, circu- lar, or polygonal thick intermediate to large triserial to quadriserial straight to sinuous parallel to proximodis- tal lateral chamber walls ovate, diamond-shaped, circular, to pentago- nal elliptical, rectangular, hexagonal, ovate, to circular ovate, circular, bilobate- ovate, to elliptical present intermediate to long absent absent 7°-12° adaxially, 25°- 47° abaxially (means) 18°-77° (means) intermediate to thick slight to pronounced intermediate to thick none polygonal or irregular cylinder Some fenestrates suggest a functional interpretation of these structures as possible tentacle guides, as does the Presence of such stylets as tentacle guides in modern Species. Jackson and Cheetham (1990, p. 579), in a work on Cheilostome Bryozoa, justify the significance of a sta- Ustically rigorous approach to bryozoan taxonomy. Employing breeding experiments and protein electro- phoresis, they observe that “‘skeletal characters of the kinds typically available in fossil material are indeed sufficient to discriminate biologic species of living chei- lostome Bryozoa.” With cheilostomes providing a good analogue for fenestrate Bryozoa, their work adds con- fidence to fossil studies of this nature. 34 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 Table 6.—Key to Warsaw genera of the Fenestellidae and Polyporidae. la. typically two rows of autozooecia across branch, except proximal to sites of branch bifurcation where two, three, or four rows are presen € Family Fenes Mida) Se.. oere er a an. ee NNI QUE e er der. ch AU men e eM go to 2 lb. typically ranging from three to five rows of autozooecia across branch except proximal to sites of branch bifurcation, where five to seven rows are present (Family Polyporidae) -... 2... ur... re er e RE e Ee et TE go to 11 da. autozooecial chambers small to lower-end. intermediate in size s. eesis cerere ad an ee nds ne go to 3 2b. autozooccial chamber size intermediate to large 2.2 Rn IET Ce Lt A ee TURNUM STA ES ER go to 4 3a. superior hemiseptum absent, chamber form an irregular rectangular box, well-developed central axis of lamellar skeleton from which mesh projects in dextral or sinistral corkscrew fashion e.s, cire o 0: cece eee mme nennen en en nen Archimedes 3b. superior hemiseptum poorly to intermediately developed at proximal vestibular edge, chamber form moderately to highly cuneate . t coi adi Loo Mus Leu A d pen ors sree en Sine, Re Rectifenestella 4a. reticulate meshwork develops atop obverse zoarial surface; each opening in mesh approximately covering one zooecial chamber ... "e o EN Sale Hemitrypa Ass Re MesIBYOrE dDseut:- ee nn A rs a c. c RUFEN NR go to 5 58. Sape nor Koce prina presompe V ee en RR ree hg DEE a eM ee re d ERN SEE tne eee e Spee tet go to 6 SD voe sur cup AOE ev M m UM Lr UM ote feo eee STOR go to 9 do Heise PULP PLCS ts. us pensio der Ent D du EA Meuse pL ale a eg ccce art go to 7 a abenteuer meer a go to 8 7a. inferior hemiseptum well-developed, positioned between middle reverse and lateral proximal wall, apertural stylets absent, chamber elongate parallel to reverse wall proximodistally ..........momoooororrrr ehe hehe eee eens Laxifenestella 7b. inferior hemiseptum well-developed, positioned at proximal side of distal lateral chamber wall, apertural stylets present, chamber elongate parallel to proximal and distal lateral chamber walls ........oooooooocororocorrrr n Exfenestella 8. two sizes of apertural stylets present; small ones filling peristomal gap, large ones positioned one each on adaxial and abaxial edges of aperture extending either slightly proximally or distally -emer i 0... cece eee eee nen Minilya 9a. reverse-wall budding-angle less than 55°, ranging to as low as 22°; apertures large; chamber elongate parallel to proximal and distal a NO Spe egal a ee ne Ra NEE EE ng UC a nT One| Banastella Ob: Teese wall Dücdmp-angle greater than 35° nm. en lee Ooo cae ped ene wen nate hy cce VI eed go to 10 10a. chamber depth and length approximately equal; chambers open at a slight to pronounced angle toward and into the fenestrule, and two rows of autozooecia across branch proximal to sites of bifurcation, but can have third row at site of bifurcation ... Cubifenestella 10b. chamber elongate parallel to reverse wall; chambers open parallel or approximately parallel to plane of obverse surface, and third row of autozooecia at and proximal to sites of branch bifurcation ..........oooooooocoooorrrrrcac nnn Apertostella lla. four rows of autozooecia across branch, two adaxial and two abaxial rows symmetrical across plane along midline of branch; adaxial chambers bud from reverse wall of branch, abaxial chambers bud from lateral wall of adaxial chambers, making this their reverse wall; poorly developed superior hemiseptum present; apertural stylets absent; keel present ..............- 0+. s eee eee eee Fenestralia 11b. three to five rows of autozooecia across branch, lacking distinct branch midline separation; adaxial and abaxial chambers all bud from reverse wall of branch; superior hemiseptum absent; apertural stylets present; keel absent ................. 0-0. sees eee Polypora TAXONOMIC CRITERIA FOR THE DISCRIMINATION OF FENESTELLID AND POLYPORID SPECIES Species definition within the fenestellids and poly- porids has long been difficult, with concepts commonly based more on dissimilarities than similarities. Yet generic descriptions must be based on sound, biolog- ically oriented species concepts. The preceding generic characters, criteria, and taxonomic approach were de- veloped subsequent to determination of the following species concepts. The taxonomic approach herein em- phasizes internal zooecial morphology and the statis- tical analysis of populations, including but de-empha- sizing zoarial features. The traditional meshwork formula characters comprise one small part of species characterization. Descriptive statistics including measures of central tendency (thus the typical development of a character) and measures of dispersion showing deviation from the typical are employed in this study; these measures include arithmetic mean, range, standard deviation, and coefficient of variation. The value of the latter depends on character variability; the greater the con- sistency of the character, the lower the value of the coefficient of variation and potentially the higher its diagnostic value (Anstey and Perry, 1970, 1973; Tav- ener-Smith, 1965; Cuffey, 1967; Bork and Perry, 1967). Higher coefficients of variation for characters reflect generally nongenetic factors, i.e., microhabitat and changes related to astogeny (Anstey and Perry, 1970). Previous studies stressing statistical comparisons (Tavener-Smith, 1965; Bork and Perry, 1967; Horo- witz, 1968) of the more consistent zooecial and zoarial characters range in coefficient of variation from 4.87 to 38.62, corresponding quite well to those observed in Warsaw species (see Tables 10-46). The charts are based on more than 10,000 measurements. Even a casual viewing verifies the consistently lower coeffi- cients of variation for zooecial characters than zoarial characters. The least variable characters are autozooe- cial chamber measurements of length, depth and width, and the reverse-wall budding-angle (e.g., numbers 36- 39 and 41); the most variable characters are those of zoarial pattern and ontogenetic skeletal accretion (e.g., numbers 2-5, 14, 15). The spread of values within each of these characters can be an order of magnitude or greater. Character lists and their associated morpho- MISSISSIPPIAN BRYOZOANS: SNYDER 35 logic statistics are arranged to facilitate use of biometric tests such as the t-test or chi-square goodness of fit. As considered earlier, zooecial characters presum- ably reflect polypide morphologies. Because zooecia are conservative within taxa but highly distinctive be- tween taxa, zooids presumably were as well (for greater detail, see pp. 31-33). Zoarial characters exhibit a much broader range of phenotypic variability than do zooe- cial characters. The more consistent the interspecific character’s expression (i.e., the lower the coefficient of variation), the potentially greater that character’s use in species differentiation. Taxon concepts were evolved in the following se- quence: (1) Shales and calcareous interbeds of the Warsaw were collected by horizon. Samples were washed and Sieved in the laboratory and bryozoans were picked. (2) Specimens were grouped based on exterior sim- llarities, thus grouping similar morphs. Obverse sur- faces were relied upon almost exclusively, as homeo- morphy between reverse surfaces of species in the fenestrates is pronounced. (3) Where material was available, 12 zoarial frag- ments from each group were photographed on both exterior surfaces and impregnated in epoxy. Where fossil fragments were incorporated in calcareous slabs, Photographs of the specimen with obverse surfaces ex- posed were taken and the specimen was subsequently impregnated in epoxy. (4) Oriented acetate peels were made of all frag- ments, providing tangential, transverse, and longitu- dinal interior views; serial peels were frequently taken to assist in determination of zooecial chamber shape. (5) Many specimens and orientations were photo- graphed at both low magnification (x 20 and x40) and high magnification (x 70), allowing more immediate comparison between zoarial fragments. (6) Specimens were then resorted based on both ex- terior and interior zoarial and zooecial appearance. Interior characters necessitated realignment of group- Ings as some taxa have very similar obverse and reverse €xteriors, but significantly different interiors. (7) Statistical analysis of both zoarial and zooecial exterior and interior characters was made; including arithmetic mean, standard deviation, coefficient of Variation, range of character variation (maximum and minimum), and number of measurements. Readjust- ment of tentative species groups was made following these statistical tests. i (8) Detailed descriptions were prepared based on all Information, with zooecial and zoarial features de- scribed three-dimensionally. _ Characters used for taxon determination are divided Into zoarial and zooecial groups; this allows ready com- Parison between characters concerned with colonial development, both ontogenetic and astogenetic, and those related to individual development, which are primarily ontogenetic in the fenestrates (McKinney, 1980). Quantitative features on which numerical anal- yses are based are listed and defined in the following section and are illustrated in Text-figures 4-7. Text- PEO anda © E d ; ns? sss REVERSE SURFACE UJ Text-figure 4. — Typical zoarial surficial features of meshwork fe- nestrates. Obverse (A) and reverse (B) surfaces are illustrated. Ab- breviations of characters are defined in Tables 7 and 8 (foldouts). 36 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 figure 4 provides typical measured zoarial and zooecial surface features of an idealized meshwork fenestrate. Text-figure 5 illustrates specialized skeletal features found in Hemitrypa Phillips, 1841, and Archimedes Hall, 1858, along with the measured dimensions of these features. Text-figures 6 and 7 provide interior measured features for two different meshwork fenes- trate species exhibiting the major characteristics found in all species. A list of measured characters with ap- propriate abbreviations and definitions for the mesh- work fenestrates can be found in Table 7; an outline of the format of Table 7, to help in interpretation of species descriptions and diagnoses, is shown in Table 8a. Maximum zoarial length and width are included in the written descriptions, but not dealt with statis- tically, as even the largest zoarial fragments collected do not represent complete colonies. Zoarial characters exhibit consistently higher coef- ficients of variation than do zooecial characters. The smallest variation within a species population is found in autozooecial chamber dimensions, including cham- ber length, width, depth, and aperture dimensions; as well as angles formed by the chamber’s emergence from the reverse wall and orientation relative to the branch center. Spacing of apertural centers down, across, and in some specimens between branches also exhibits rel- atively low coefficients of variation. Highest coeffi- cients of variation are observed in characters definitely associated with the zoarium such as length and width of fenestrule, width of dissepiment, spacing and size of nodes and stylets, branch width and thickness (depth), and keel and carinal development. Zooecial characters are thus emphasized, both empirically and descrip- tively. Characters used in statistical analysis are outlined in Table 8a. This analysis is broken down into those characters determined from exteriors and those from interiors, as this was found to be the most practical means of data gathering. Species data sheets follow this outline, as grouping characters separately eases anal- ysis. To add consistency, all characters for all species are treated in one sequence, as shown in Table 8b. Each character has a delimiter for range of size, shape, etc. within the character. Where possible and appropriate, measurements (employing arithmetic mean) and coef- ficients of variation are used. It is my hope that the Table will allow others to understand the criteria used herein. The outline can also provide a guide for further work, although it should be emphasized that range of size and shape is based solely on Warsaw Bryozoa analyzed. Table 9 provides a taxonomic list of Warsaw species analyzed in the order in which they are presented in the systematics section. SYSTEMATIC PALEONTOLOGY TAXONOMIC PHILOSOPHY Modern biological and paleontological concepts of species are significantly different, basically due to the nature of available data. Biologists can apply breeding experiments and/or protein electrophoresis to discrim- inate biologic species of living Bryozoa. Through ob- servation, it is possible for biologists to determine if they are dealing with members of the same biological species as well as to delimit, through analysis of in- dividuals, the boundaries of phenotypic expression of the genotype. In spite of the paucity of comparable data available to the paleontologist, it is imperative that fossils be classified in the most biologically correct fashion possible. BRANCH MIDLINE E te DISTAL WSC SINISTRAL C Text-figure 5.— Characters measured in the reticulate meshwork of Hemitrypa (A, B) and the central spire or axis of Archimedes (C). Abbreviations of measured characters are defined in Tables 7 and 8 (foldouts). DEXTRAL MISSISSIPPIAN BRYOZOANS: SNYDER 37 For paleontologists to emphasize features of biolog- ical significance in their classification schemes requires, in a real sense, working in reverse, compared to the way a biologist analyzes species. Biologists employ soft- part analysis as a major aspect of systematic descrip- tion, with skeletal components significant but in many respects occupying a supportive role. In Warsaw Bryo- Zoa, the phenotypic expression of the genotype is locked in the superbly preserved skeletal remains. The task of the paleontologist is to attempt to re- produce soft body structures through interpretation of the preserved skeletal remains. In the Warsaw fenes- trates, this can be accomplished in several ways. The first is to employ modern analogs, such as the chei- lostome Bryozoa, for comparison with the Paleozoic TRANSVERSE SECTION B fenestrates. Although it is not possible to reproduce the appearance of the polypide in the fenestrates, we can assume that the size and shape of the polypide is as consistent as it is in modern cheilostomes. Second, through careful measurement of zooecial chambers, it was found that chambers exhibit extremely consistent sizes and through reconstruction of chambers it was also determined that within species they have highly constant shapes. Thus, we now have not only deter- mined skeletal physical dimensions, but have, through interpretation of these measurements and comparison with modern species, been able to reconstruct inter- preted soft-part sizes and shapes. Through such a com- bination, we satisfy not only classic paleontological prerequisites, but also provide a more accurate bio- ow SHALLOW SHALL ny ES N DEEP FWT RWT TANGENTIAL SECTION C Text-figure 6.— Characters measured in the interior of Banastella guensburgi. Transverse (A, B), tangential (C), and longitudinal (D) section Views are shown. Abbreviations of measured characters are defined in Tables 7 and 8 (foldouts). D LONGITUDINAL SECTION 38 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 logical interpretation of fossil species. Biologically sig- nificant characteristics are emphasized in the taxonom- ic descriptions and diagnoses of fenestrate Bryozoa herein, as such characters assist in establishing a less artificially constructed classification. The species concepts applied herein are a significant 7 TRANSVERSE SECTION B TANGENTIAL SECTION Text-figure 7.—Characters measured in the interior of Cubifenes- tella usitata. Transverse (A), tangential (B), and longitudinal (C) views are shown. Abbreviations of measured characters are defined in Tables 7 and 8 (foldouts). departure from those of most previous workers, ex- cluding McKinney (1980). Whether such a departure is necessary is a question answered by the numerous problems encountered when attempting to classify a fenestrate species. I became interested in taxonomic difficulties in the fenestrates while analyzing bryozoan SHALLOW C LONGITUDINAL SECTION MISSISSIPPIAN BRYOZOANS: SNYDER 39 Table 9.—Taxonomic list of Warsaw meshwork fenestrate species. Numbers assigned to species are used in illustrations elsewhere in this paper. Order Cryptostomata Vine, 1884 Suborder Fenestelloidea Astrova and Morozova, 1956 Family Fenestellidae King, 1849 Genus Rectifenestella Morozova, 1974 1. Rectifenestella tenax (Ulrich, 1888) 2. Rectifenestella tenuissima (Cumings, 1906) 3. Rectifenestella multispinosa (Ulrich, 1890) Genus Laxifenestella Morozova, 1974 4. Laxifenestella coniunctistyla, n. sp. 5. Laxifenestella maculasimilis, n. sp. 6. Laxifenestella serratula (Ulrich, 1890) 7. Laxifenestella fluctuata, n. sp. Genus Minilya Crockford, 1944 8. Minilya sivonella, n. sp. 9. Minilya paratriserialis, n. sp. Genus Exfenestella Morozova, 1974 10. Exfenestella exigua (Ulrich, 1890) Genus Banastella, n. gen. 11. Banastella guensburgi, n. sp. 12. Banastella cingulata (Ulrich, 1890) 13. Banastella mediocreforma, n. sp. 14. Banastella limitaris (Ulrich, 1890) 15. Banastella biseriata (Ulrich, 1890) 16. Banastella delicata, n. sp. Genus Cubifenestella, n. gen. 17. Cubifenestella rudis (Ulrich, 1890) 18. Cubifenestella usitata, n. sp. 19. Cubifenestella globodensata, n. sp. Genus Apertostella, n. gen. 20. Apertostella foramenmajor, n. sp. 21. Apertostella crassata, n. sp. 22. Apertostella venusta, n. sp. Genus Hemitrypa Phillips, 1841 23. Hemitrypa perstriata Ulrich, 1890 24. Hemitrypa hemitrypa (Prout, 1859) 25. Hemitrypa aprilae, n. sp. 26. Hemitrypa aspera Ulrich, 1890 27. Hemitrypa vermifera (Ulrich, 1890) Genus Archimedes Hall, 1858 28. Archimedes negligens Ulrich, 1890 29. Archimedes owenanus (Hall, 1857b) 30. Archimedes wortheni (Hall, 1857b) 31. Archimedes valmeyeri, n. sp. Family Polyporidae Vine, 1884 Genus Fenestralia Prout, 1858a 32. Fenestralia sanctiludovici Prout, 1858a Genus Polypora McCoy, 1844 33. Polypora gracilis Prout, 1860 34. Polypora varsoviensis Prout, 1858a 35. Polypora spininodata Ulrich, 1890 36. Polypora simulatrix Ulrich, 1890 37. Polypora retrorsa Ulrich, 1890 fossils from the Guadalupian age Gerster Formation Of northeastern Nevada in 1972. Although challenging, the trepostomes, cystoporates, and other cryptostomes were recognizable from previous works or at least de- Scribable from materials and references that were avail- able. The fenestrates, on the other hand, were seem- ingly impossible to work with employing existing techniques. It was this difficulty, and my introduction to the superbly preserved Warsaw fenestrates by Dan Blake, that led me to undertake this project. Thorough specimen analysis is critical for accurate species assignment and taxonomic analysis. As indi- cated throughout the text, reliance on methods that measure and/or describe symmetry of the fossil, fre- quently ignoring characters that have taxonomic sig- nificance, has been a major problem in fenestrate tax- onomy. A priori determination of significant taxonomic characteristics, without benefit of complete and de- tailed comparison of those characters within and be- tween species has been a common failing of taxonomic works, and has been a major weakness in the Bryozoa. The great number of characters employed herein re- flects the numerous significant taxonomic character- istics present in the fenestrates. Numerical manipu- lation of the raw data generated by this study was undertaken by Hageman (1987) and Snyder and Kepler (1987) to determine which of the measured characters were significant and if the number of characters could be significantly reduced while still allowing accurate species determination. Based solely on numerical means, species assignments were well confirmed with as few as 15 characters, zooecial characters being the most significant. Although this reduced number of characters would allow recognition within a described fauna, both Hageman and I found that virtually all characters had significance at the species level. Further numerical work is in progress, and analysis to date strongly supports detailed character measurements and descriptions. New species and genera are based on readily distin- guishable zooecial chamber differences between spe- cies; differences in shape, size, apertural characteristics, accessory features such as hemisepta, and variation in chamber placement within the zoarium. Zoarial char- acters are employed, but to a much lesser degree than zooecial ones. A difficulty arises with comparison to previously established species and genera, as their de- scriptions frequently do not contain what appear to be the most significant taxonomic characters. This prob- lem is due, in part, to incomplete sections, inadequate descriptions, and use of two-dimensional rather than three-dimensional analyses in most previous works on fenestrates. For this reason, Warsaw fenestrates were separated into what appeared to be species groupings prior to comparison of the Warsaw fauna with species previously assigned by Ulrich and other workers. Many new species were the result of exterior homeomorphy between species that exhibited pronounced interior dissimilarities. Finally, once measurements and significant features have been determined, it is imperative to present such 40 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 information in a consistent format that allows accurate comparison within and between species. ABBREVIATIONS OF REPOSITORY INSTITUTIONS Specimens and lithologic samples collected for this study are all reposited in the collections of the De- partment of Geology, University of Illinois. Addresses and acronyms of this and other specimen repositories are listed below. It is unfortunate that, in spite of ex- tensive searching, so few of Ulrich’s original types could be located. The quality of specimen illustration and thin-section reproduction in his published works proved invaluable for species recognition. AMNH: American Museum of Natural History, New York, NY. ISGS (ISM): Illinois State Geological Survey, Urbana, IL. USNM: United States National Museum of Natural History, Smithsonian Institution, Washington, DC. UI X: University of Illinois, Urbana, IL. Materials from this study housed at the University of Illinois have type numbers (UI-X . . .) assigned to the fossil fragment. One number is assigned to each fragment. Many fragments were embedded in epoxy, and acetate peels were prepared to illustrate chamber and colony characteristics in different sectional views. An alphanumeric designator is given to each peel fol- lowing the appropriate UI X number. For example, in the explanation of Plate 1, figure 5 (p. 192), UI X-6799 is followed by the peel designator FF-69. This desig- nator indicates that the photograph was taken from peel 469, stored in box FF, and belongs to hypotype UI X-6799. This procedure protected peels by housing them in dust-proof peel [=thin-section] boxes while research continued, and the same storage procedure was followed when type assignments were made. Should readers desire access to specific peels, use of peel des- ignators in the above fashion will facilitate their rapid retrieval. The information enclosed in brackets in taxonomic synonymies indicates the stratigraphic and geographic locations of the specimen or specimens referred to by the indicated authors. In photographic plates, dashed lines are employed to add continuity to portions of the same colony that would otherwise appear disjunct. SYSTEMATICS Family FENESTELLIDAE King, 1849 Zoaria fan-shaped, constructed of branches that bi- furcate at regular to variable intervals. Branches con- nected at varying distances by dissepiments (transverse links lacking autozooecial chambers), which may or may not have apertures opening onto the dissepiment edge. Each individual (autozooecium) of the zoarium has single apertural opening; openings occur only on the front or obverse surface of the fan, the back or reverse surface being without apertural openings. Two rows of zooecia typically are present across each branch. Exterior obverse ornamentation can consist of longi- tudinal keels (referred to as carinae by some authors); nodes of various forms positioned along branch sur- faces and/or on dissepiments; stylets positioned down the branch, on dissepiments, and/or around apertures; peristomal structures; and heterozooecial features. Re- verse exterior surfaces commonly exhibit longitudinal striae, microstylets and macrostylets of varying sizes, zoarial supports, and show pronounced character changes with astogeny. Interior features include au- tozooecial chamber shape and orientation, presence of superior hemiseptum (adjacent to obverse interior wall) or inferior hemiseptum (adjacent to reverse interior or lateral chamber walls), vestibule and terminal dia- phragms. Interior characters are considered in detail under the species and genera. Range.—Ordovician to Triassic. Many genera are long-ranging and abundant. The Warsaw genera Rectifenestella Morozova, 1974, Laxifenestella Morozova, 1974, Minilya Crockford, 1944, Exfenestella Morozova, 1974, Banastella, n. gen., Cubifenestella, n. gen., Apertostella, n. gen., Hemitrypa Phillips, 1841, and Archimedes Hall, 1858 are included in this family. The genus Fenestella Lonsdale, 1839 should also be included, but needs redefinition from the type materials. As currently defined, Fenestella does not appear to be present in the Warsaw, but this genus does belong in the Fenestellidae. Genus RECTIFENESTELLA Morozova, 1974 Text-figure 8 Type species.— Fenestella medvedkensis Shulga-Nes- terenko, 1951. [Upper Carboniferous, Kasimovian Stage; Russian Platform]; Morozova, 1974. pp. 175- 176; pl. 4-1. Typical Warsaw species. — Fenestella tenax Ulrich, 1888, p. 71. [Waverly Group, Devonian, Ohio]. Diagnosis.—Zoarium robustness delicate to inter- mediate, mesh close to intermediate; characteristic tri- angular to pentagonal chamber outline in mid tangen- tial section, chamber size small to intermediate, aperture size small to intermediate, poorly developed superior hemiseptum present, chamber reverse-wall budding-angle approximately 70°. Three-dimensionally reconstructed chamber form moderately to highly cuneate. Description. —Zoarium robustness delicate to inter- MISSISSIPPIAN BRYOZOANS: SNYDER 41 mediate, expansion flat to slightly obversely curved with mesh spacing close to intermediate, mesh uni- formity regular to irregular. Branches narrow, straight to curved, surface profile rounded to moderately flat. Keel present, single, nar- row to intermediate width, straight to anastomosing; width increases and keel frequently covered by lamellar skeleton during astogeny. Nodes present, monoserially emplaced, intermediate in size, circular to ovate in shape, located atop middle of keel, closely spaced. Ob- verse stylets present, small, occurring across obverse branch surface. Reverse surface typically bearing mi- crostylets, small to intermediate in size, developed atop longitudinal striae. Autozooecia in two rows, third row at sites of branch bifurcation. Heterozooecia (ovicells?) present in some species. Dissepiment width thin to intermediate; short to intermediate in length and regularly emplaced. Fenestrule size small to intermediate, shape ranging from rectangular to elliptical to square. Aperture size small to intermediate, circular to ovate in shape, oriented parallel to plane of obverse surface or at a low angle toward fenestrule. Peristome present, complete or incomplete, open at proximal edge; ap- ertural stylets occurring in peristomal gap. Terminal diaphragms present, most commonly occurring toward Proximal end of zoarium. Branches ovate, elliptical, circular to semicircular in Cross-section; shallow to medium in depth. Autozooecial chambers small to intermediate in size, biserially emplaced, axial wall trace sinuous to zigzag. Maximum chamber length parallel to reverse wall in Proximodistal direction. Chamber outline in tangential View triangular to irregularly pentagonal near reverse wall and throughout mid chamber, bilobate elliptical near obverse surface (Text-fig. 10). Vestibule present, Short to long. Superior hemiseptum present, poorly to Intermediately developed at proximal vestibular edge; inferior hemiseptum absent. Lateral-wall budding-an- gle varying between 23° and 30° (means); reverse-wall budding-angle varying between 68° and 71° (means). Lamellar skeletal layer thin, exhibiting moderate to Pronounced astogenetic thickening; granular skeletal layer thin to intermediate, exhibiting no astogenetic thickening. Three-dimensionally reconstructed chamber form moderately to highly cuneate. Text-figure 8 illustrates zoarial outlines in longitu- dinal, tangential, and transverse orientations, and three- dimensional chamber reconstructions from distal, ab- axial branch edge, and obverse surface views. Remarks.— General chamber shape is quite similar to that of Minilya Crockford, 1944, as are development 9f superior hemisepta and general autozooecial cham- ber size. Rectifenestella is distinguished by typically having a less cuneate chamber shape, by lacking the large biserially arranged apertural stylets that are char- acteristic of Minilya, and by having a generally lower reverse-wall budding-angle. The generic concept is expanded from that of Mo- rozova through use of a three-dimensional approach; this genus is readily recognized among Warsaw fenes- tellids. The age of species (Late Silurian to Permian) assigned to this genus by Morozova easily encompasses the age of the Warsaw. Assignment of F. serratula Ulrich, 1890, and F. rudis Ulrich, 1890, to this genus is incorrect according to three-dimensional study of autozooecial chamber shape and placement of hemisepta. F. serratula, herein as- signed to Laxifenestella Morozova, 1974, has a box- like rather than cuneate chamber form in three-di- mensional view and well-developed superior and in- ferior hemisepta, whereas species of Rectifenestella lack inferior hemisepta. F. rudis, herein assigned to Cubi- fenestella, n. gen., has a box-like chamber form in three- dimensional view and lacks both superior and inferior hemisepta. R. multispinosa Ulrich, 1890, is correctly assigned to this genus, as suggested by Morozova. Problems with Morozova's assignment of species to this genus are due largely, if not solely, to the lack of adequate three-dimensional analysis. Her work, based almost exclusively on obverse surficial view, does not allow for recognition of chamber form and hemiseptal development, two of the characters most critical for generic assignment. Specific composition.— Over 100 species were rec- ognized by Morozova (1974); this number would be reduced by following emended diagnosis provided here. Three Warsaw species are included in this genus: R. tenax (Ulrich, 1888), R. tenuissima (Cumings, 1906), and R. multispinosa (Ulrich, 1890). Range.— Late Silurian to Permian (Morozova, 1974). Rectifenestella tenax (Ulrich, 1888) Plates 1, figures 1-12, Plate 2, figures 1-3; Table 10 Fenestella tenax Ulrich, 1888, p. 71; Ulrich, 1890, p. 546, pl. 51, figs. 2-23; Nekhoroshev, 1926, p. 1248, pl. 19, fig. 12; Condra and Elias, 1944, pp. 99-102, pl. 21, figs. 1-4; Elias and Condra, 1957, pp. 106-107, pl. 10, figs. 1, 2; Trizna, 1958, p. 132, pl. 38, figs. 1-4; Burckle, 1960, pp. 1084-1085, pl. 131, fig. 2. Fenestella tenax Ulrich (?). Cumings, 1906, p. 1279, pl. 30, fig. 1; pl. 21, figs. 1-1a. Fenestella submicroporata Shulga-Nesterenko, 1952, pp. 35-36, fig. 1» ply figs 2: Diagnosis.—Zoarium delicate, mesh close, pattern irregular; branches delicate, width narrow, thickness thin, straight to slightly curved in trace, transversely ovate, moderately closely spaced; branches joined at highly regular intervals by thin, short dissepiments. 42 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 Table 10.—Summary numerical analysis of Rectifenestella tenax (Ulrich, 1888). For explanation of abbreviations of characters (left column), see Table 8b (foldout inside back cover). number of mea- coeffi- sure- standard cient of observed ments mean deviation variation range 1. WB 24 0.2641 0.0498 18.86 0.190-0.350 2. DBC 24 0.4612 0.0533 16.56 0.380-0.548 3. WD 24 0.1268 0.0283 22.32 0.093-0.187 4. LF 24 0.3368 0.0504 14.96 0.228-0.413 5. WF 24 0.2143 0.0332 14.93 0.158-0.283 6. AF 24 DIS 0.51 20.43 2-3 7. AL 24 0.0644 0.0074 11.49 0.050-0.082 9. ADB 24 0.2307 0.0211 9.15 0.195—0.278 10. AAB 24 0.2821 0.0443 15.70 0.220-0.355 11. ABB 24 0.3014 0.0714 23.69 0.213-0.499 12. DN 24 0.0954 0.0180 18.87 0.065-0.143 14. SNB 24 0.2248 0.0360 16.01 0.167-0.293 15. WK 24 0.0781 0.0163 20.87 0.048-0.100 16. DSO 24 0.0081 0.0012 14.81 0.006-0.011 17. SSO 24 0.0419 0.0170 40.57 0.020-0.077 18. WP 24 0.0208 0.0075 36.06 0.011-0.038 19. SA 24 6.42 1.02 15.86 5-8 20. SAD 24 0.0306 0.0088 28.76 0.018-0.058 21. RSL 24 0.0609 0.0261 42.86 0.022-0.112 23. SSL 24 0.0919 0.0361 39.28 0.042-0.227 30. OL 15 0.1306 0.0240 18.38 0.090-0.178 31. OW LS 0.1213 0.0215 17.72 0.083-0.167 32. TRW 24 0.0071 0.0012 16.90 0.005-0.009 33. TLW 24 0.0076 0.0011 14.48 0.005-0.009 34. FWT 24 0.0295 0.0169 57.29 0.009-0.066 35. RWT 24 0.0535 0.0367 68:60 0.018-0.149 36. CE 24 0.1840 0.0041 2.23 0.179-0.195 37. CD 24 0.1003 0.0061 6.08 | 0.092-0.114 38. MAW 24 0.1037 0.0080 7.71 0.089-0.122 40. VD 24 0.0449 0.0168 37.42 0.027-0.076 41. RA 24 70.75 5.42 7.67 62-82 42. LA 24 30.63 4.74 15.49 19-39 43. TB 24 021701: 010900513482: 20459-02271 Fenestrules small; shape rectangular, elliptical to rarely square, moderately regular in shape. Autozooecial ap- ertures very small, shape circular, surrounded by well- developed incomplete peristome open only at proxi- mal-adaxial edge; two to three (most commonly two) apertures per fenestrule. Single intermediate-width keel along middle of obverse branch, atop which are po- sitioned intermediate-size, circular to ovate nodes. Au- tozooecial chamber size upper-end small, emplaced in two rows, except third row at sites of branch bifurca- tion; outline triangular to irregularly pentagonal near reverse wall and throughout most of chamber, becom- ing irregularly bilobate-elliptical near obverse surface. Chambers elongate proximodistally, parallel to reverse wall. Aperture at distal-abaxial end of chamber con- nected to chamber by short vestibule of variable length. Intermediately developed short superior hemiseptum present, inferior hemiseptum lacking. Lateral-wall budding-angle moderately variable (mean of 30°); re- verse-wall budding-angle highly constant (mean of 71°). Heterozooecia between nodes along middle of obverse branch surface. Table 10 presents statistical criteria used in delim- iting this species. Exterior description.—Zoarium delicate; expansion flat to slightly obversely curved, fan-shaped; mesh close; pronounced astogenetic thickening observed in both obverse and reverse zoarial lamellar skeleton; external zoarial pattern irregular, partially as a result of asto- genetic thickening. Probable mature widths 10 to 15 mm; lengths 20 to 30 mm. Branches delicate; narrow, moderately variable in width; most commonly straight, some very slightly curving toward lateral edge of zoarium. Branches mod- erately closely spaced, distance between adjacent branch centers regular. Obverse surface slightly granular in texture, becoming increasingly so with astogeny; sur- face rounded except for single intermediate-width, moderately well-developed keel; keel relatively con- tinuous, straight to slightly anastomosing, extending along branch midline and causing positive inflection on obverse surface. With astogeny, keel frequently cov- ered by lamellar skeleton. Single row of well-developed intermediate-size nodes, shape circular to ovate, elon- gate proximodistally; size and shape of nodes mod- erately regular; nodes project from middle of keel in straight line; one to three nodes per fenestrule length, two most common; closely and evenly spaced; node diameter increasing with astogeny. Small, regularly Text-figure 8.—Rectifenestella tenax and Rectifenestella tenuissi- ma illustrated. 1, diagrammatic longitudinal section of R. tenax showing chamber outline from deep section near middle of branch (bottom of figure) to shallow section near adaxial edge of branch (top of figure), x 70; 2, diagrammatic tangential section of R. tenax il- lustrating change in chamber outline from deep section near reverse- wall budding-site (bottom of figure) to shallow section near obverse surface (top of figure) [Note presence of superior hemiseptum at proximal vestibular edge (arrow).], x 70; 3, diagrammatic transverse sections across branch of R. tenax illustrating short superior hemi- septum (arrow) and orientation ofthe aperture to the obverse surface, x 70; 4, diagrammatic longitudinal section of R. tenuissima showing chamber outline from deep section (bottom of figure) to shallow (top of figure) [Note pronounced similarity in chamber outline between this species and R. tenax.], x 70; 5, diagrammatic tangential section of R. tenuissima from deep (bottom of figure) to shallow (top of figure sectional view [Superior hemiseptum (arrow) is more reduced in this species than in R. tenax.], x 70; 6, diagrammatic transverse section of R. tenuissima, x70; 7, reconstruction of typical Rectife- nestella chamber shape (three-dimensional) as viewed from abaxial edge of branch, showing slight inflection of superior hemiseptum into chamber (arrow), x140 [R. tenax is used as a representative rectifenestellid in this reconstruction.]; 8, reconstruction of typical Rectifenestella chamber shape (three-dimensional) as viewed from obverse surface; chamber reconstructed is from the right side of branch [Moderate displacement of apertures toward abaxial edge of chamber is exhibited.], x 140; 9, reconstruction of typical chamber shape (three-dimensional) as viewed from distal end of branch; chamber reconstructed is from the right side of branch, x140. MISSISSIPPIAN BRYOZOANS: SNYDER 43 sized and variably positioned stylets across obverse branch surface. Reverse surface texture relatively gran- ular, becoming more coarsely granular with astogeny; bearing a moderate number of rows of closely spaced longitudinal striae atop which are positioned closely spaced rows of small to intermediate-size macrostylets; macrostylet size and shape highly variable. Macrosty- lets increase in diameter with astogeny, becoming more irregularly positioned along reverse branch surface; longitudinal striae becoming covered through astoge- netic thickening of lamellar skeleton. Autozooecia ar- ranged in two rows, except third row at sites of branch bifurcation where middle autozooecium evidently shared by both branches; pronounced thickening of branches proximal, thinning distal to sites of branch bifurcation. Circular to slightly ovate depressions (ovi- cells?) occurring between nodes along middle of ob- verse branch surface; mean diameter of polymorphs approximately twice that of autozooecial apertures; no direct connection evident between apertural opening and polymorphs. Dissepiments thin, slightly less than half branch width, width variable; short, quite constant in length; connecting branches at highly regular intervals. Dis- sepiments barlike, slight medial thinning; highly re- cessed from obverse, slightly so from reverse surface. Pronounced astogenetic thickening of dissepiments. Obverse dissepiment surface with two to three longi- tudinal striae across dissepiment perpendicular to branch length; reverse dissepiment surface with lon- gitudinal striae atop which occur rows of stylets; striae covered by lamellar skeleton, stylet number decreasing and size increasing as dissepiment thickens during as- togeny; both obverse and reverse dissepiment surfaces granular in texture. Dissepiments emplaced perpen- dicular to or at slight angle from perpendicular to branch length. Apertures commonly open on proximal or dis- tal edge or in middle of dissepiment edge at branch- dissepiment contact; arranged symmetrically or asym- metrically between branches. Fenestrules small; shape varying from (most com- monly) rectangular to elliptical, elongate proximodis- tally, to rarely square; moderately regular in size and shape; expanding slightly in width and length in ob- verse-reverse direction. Width of fenestrule slightly less than branch width on obverse surface, approxi- mately equal to branch width on reverse, mean width of fenestrule approximately 1.28 branch width; fe- nestrule opening becoming small toward proximal end of zoarium with astogenetic thickening of lamellar skel- eton. Width to length ratio of fenestrule ranging from 1:1 to slightly less than 1:2, variable; constancy of length and width equal. Two to three apertures per fenestrule length, two most common; distance between closest aperture centers along branch approximately four-fifths of spacing across branch and across fenestrule, spacing of aperture centers across fenestrules varying from less than that along branch to twice that distance; spacing along branch much more constant than across branch or across fenestrule, which are moderately variable. Autozooecial apertures very small, shape circular, uniform in size and shape; opening oriented parallel to plane of obverse surface; thin, well-developed peri- stome continuous around all but small portion of most proximal-adaxial edge of aperture, leaving a small peri- stomal gap. Apertural stylets present, with five to eight intermediate-size stylets developing as extensions of PALAEONTOGRAPHICA AMERICANA, NUMBER 57 vestibule outer edge; apertural stylets moderately con- stant in number. Aperture margin extends into fenes- trule, causing pronounced inflections in fenestrule out- line in obverse surface. Centrally thickened terminal diaphragms present, occurring moderately infrequent- ly, confined to most proximal end of zoarium. Zoarial supports well-developed, as extension of re- verse zoarial surface and lateral edge of zoarium. Interior description. — Branches ovate or elliptical in transverse section, elongate parallel to zoarial surface (i.e., in width). Branches thin, moderately regular in thickness. Upper end of autozooecial living chamber small, chambers biserially arranged in alternating rows along planar branch axial wall; axial wall forming zigzag pat- tern extending diagonally across entire branch or con- necting with short chamber lateral walls. Chamber longest dimension paralleling reverse wall in proxi- modistal direction. Autozooecial chamber outline tri- angular or irregularly pentagonal near reverse wall and throughout most of chamber; becoming irregularly biolobate-elliptical near obverse surface, longest di- rection of ellipse oriented distal-abaxially; chamber shape highly uniform. Aperture positioned at distal- abaxial end of chamber, connected to chamber by rel- atively short vestibule of variable length. Autozooecial chamber width and depth approximately equal; ratio of depth to length 5:9; length much more constant than width and depth. Intermediately developed short su- perior hemiseptum present, formed as extension of proximal-adaxial vestibular edge, forming partial re- striction between vestibule and autozooecial chamber; inferior hemiseptum lacking. Autozooecial chamber diverges laterally from middle of branch at a moder- ately variable angle (mean of 30?); from reverse wall at highly constant angle (mean of 71?). Three-dimensionally reconstructed autozooecial chamber form highly cuneate, long in horizontal view with acute angles at proximal and distal ends of cham- ber, and obtuse angle toward branch midline; near re- verse wall, approaching box-like in mid chamber with angular extension toward branch midline; long as viewed from obverse surface; approximately equidi- mensional in depth and width as viewed from distal and lateral edges of branch, respectively. Internal granular skeletal layer thickness interme- diate, continuous with obverse nodes, stylets, keel, peristome, reverse longitudinal striae, stylets across dissepiments, in middle of zoarial supports. Outer la- mellar layer initially thin, with pronounced astogenetic thickening of skeleton toward proximal end of zoar- ium. Remarks.—R. tenax is similar to R. tenuissima (Cumings, 1906) and R. multispinosa (Ulrich, 1890) in autozooecial chamber shape and orientation of MISSISSIPPIAN BRYOZOANS: SNYDER 45 chambers relative to the branch. However, R. tenax differs moderately to substantially from the above two species in chamber dimensions, aperture size and shape (circular in R. tenax but not in R. tenuissima or R. multispinosa), and exterior accessory characters such as node placement and dissepiment ornamentation. Similarities in chamber shape and orientation are char- acteristic of generic level taxonomic groupings within the fenestellids and polyporids. Fenestella submicroporata Shulga-Nesterenko, 1952 was placed in synonymy with R. tenax due to simi- larities in mesh symmetry, accessory features, and chamber size and shape between the two species. Externally, R. tenax is similar in appearance to Lax- ifenestella serratula (Ulrich, 1890), however pro- nounced differences are observed in internal chamber Shape and orientation. Such similar patterns in exterior view most probably represent geometric constraints of Zoarial growth, and do not appear to denote close tax- onomic affinities. The moderately variable appearance of both obverse and reverse zoarial exteriors as a result of astogenetic thickening of lamellar skeleon makes interior analysis Mandatory for recognition of this species. Material studied.—Forty exterior fragments, 20 sec- tioned specimens; largest zoarial fragment 11 x18 mm (width to length). Most fragments examined were mod- erately well-preserved, although compaction of some autozooecial chambers was evident. Occurrence.—R. tenax is common thoughout the Warsaw study area, occurring primarily in facies thought to have been deposited in a lower energy en- vironment. Syntypes.—ISGS(ISM) 4486-4. USNM 43756, 43757. Several specimens from various localities are illustrated in Ulrich (1890, pl. 51, figs. 2, 2a, 2b, 2c, 2d, 2e). Figured and/or measured specimens.— UI X-6797- 6807 (loc. 49B, samples 10, 12), UI X-6889, 6890, 6892-6897, 6899 (loc. 10, samples 27, 31). Rectifenestella tenuissima (Cumings, 1906) Plate 2, figures 4-10, Plate 3, figures 1-8; Table 11 Fenestella tenuissima Cumings, 1906, p. 1279. Fenestella stocktonensis Condra and Elias, 1944, pp. 162-163, pl. 35, fig, 5. pl, 36, figs. 1, 2. Diagnosis.—Zoarium delicate, mesh intermediate and regular; branches delicate, width narrow, thickness thin, straight to broadly curved in trace; transversely Ovate to semicircular, elongate in plane of zoarial sur- face; distance between branches intermediate. Inter- Mediate-width, intermediate-length dissepiments con- nect branches at highly regular intervals. Fenestrule Size intermediate, rectangular to elliptical, moderately Variable in shape. Autozooecial apertures of interme- diate size, ovate, elongate proximodistally; peristome well-developed, incomplete, open only at proximoad- axial edge; three to six small stylets occurring in peri- stomal gap, large apertural stylet at distal-abaxial edge of aperture; two to four (most commonly three) ap- ertures per fenestrule length. Single narrow keel along middle of obverse branch, nodes of intermediate size, ovate, proximodistally elongate, positioned atop keel. Autozooecial chamber size lower-end intermediate, chambers emplaced in two rows, except third row at sites of branch bifurcation; chamber outline irregularly pentagonal throughout most of chamber depth, be- coming elliptical, then irregularly bilobate-elliptical near obverse surface. Chambers elongate proximodis- tally, parallel to reverse wall. Aperture at distal-abaxial end of chamber, connected to chamber by short ves- tibule of variable length. Short superior hemiseptum present, inferior hemiseptum absent. Lateral-wall bud- ding-angle highly variable (mean of 23?); reverse-wall budding-angle constant (mean of 68?). Large hetero- zooecia (ovicells?) rarely present. Table 11 presents statistical criteria used in species delimitation. Exterior description. — Zoarium delicate, expansion flat to slightly obversely curved, fan-shaped; mesh in- termediate; slight to moderate astogenetic thickening of both obverse and reverse lamellar skeleton; zoarial pattern regular. Probable mature widths 20 to 25 mm, lengths 30 to 40 mm. Branches delicate, narrow, relatively constant in width; straight to broadly curved toward lateral edge of zoarium. Branch spacing intermediate, distance be- tween adjacent branch centers moderately regular. Ob- verse surface texture moderately granular, surface rounded or moderately flat; except single narrow, con- tinuous keel anastomosing around autozooecial aper- tures, extending along branch midline, causing positive inflection. Keel widens, becomes covered by lamellar skeleton, and obverse surface becomes increasingly granular in texture with astogeny. Single row of inter- mediately developed, intermediate-size nodes; nodes ovate, elongate proximodistally, size and shape mod- erately regular, projecting from middle of keel; two to four nodes per fenestrule length, three most common; nodes intermediately, moderately unevenly spaced; node diameter increasing with astogeny. Extremely small, irregularly spaced stylets occurring between nodes and across obverse branch surface. Reverse sur- face texture granular, becoming more coarsely granular with astogeny, bearing numerous rows of longitudinal striae atop which are positioned closely spaced rows of small microstylets; longitudinal striae become cov- ered by lamellar skeleton; stylets become larger, less regularly positioned along branch surface with asto- geny. Two rows of autozooecia across branch, except third row at site of branch bifurcation where middle autozooecium evidently shared by both branches; pro- nounced proximal thickening of branches, thinning distal to sites of branch bifurcation. Dissepiments of intermediate width, two-thirds that of branch, moderately constant; length intermediate, moderately constant; connecting branches at highly regular intervals. Dissepiments relatively barlike, slight medial thinning; slightly to moderately recessed from obverse surface, even with reverse; pronounced asto- genetic thickening of dissepiments toward proximal end of zoarium. Obverse dissepiment surface with two to five longitudinal striae across dissepiment, oriented perpendicular to branch length; reverse dissepiment surface with longitudinal striae oriented perpendicular to branch length, atop which occur rows of small mi- crostylets; dissepiment surfaces granular, texture sim- ilar in appearance to obverse and reverse branch sur- faces. Dissepiment emplacement primarily perpendicular to branch length, less frequently at acute angle trending either proximally or distally. Apertures commonly open on proximal or distal edge or in mid- dle of dissepiment edge at branch-dissepiment contact; arranged symmetrically or assymmetrically between branches. Fenestrules of intermediate size, rectangular to el- liptical in tangential view, elongate proximodistally; moderately variable in shape, regular in size; opening constant in size and shape on both obverse and reverse surfaces. Mean width of fenestrule slightly less than that of branch; fenestrule opening becoming slightly smaller toward proximal end of zoarium with asto- genetic thickening of lamellar skeleton. Width to length ratio of fenestrule 2:5, relatively constant, length much more constant than width. Two to four apertures per fenestrule length, three most common; distance be- tween closest aperture centers along branch and across branch approximately equal; spacing of aperture cen- ters across fenestrule 1.3 X greater than across branch, much more variable. Autozooecial apertures of intermediate size, ovate, slightly elongate proximodistally and enlarged at distal end, width to.length ratio 9:10, size and shape uniform; opening oriented parallel to plane of obverse surface; thin, well-developed, incomplete peristome with small gap at most proximal-adaxial edge, three to six small stylets occurring in peristomal gap. Large apertural sty- let at distal-abaxial edge of each aperture, forms as a peristomal extension. Aperture margin extends into fenestrule, causing slight inflections in fenestrule out- line in obverse view. Centrally thickened terminal di- aphragms rare, confined to most proximal end of zoar- jum. Zoarial supports develop as extensions of reverse zoarial surface and lateral edge of zoarium, relatively poorly developed. PALAEONTOGRAPHICA AMERICANA, NUMBER 57 Table 11.—Summary numerical analysis of Rectifenestella ten- uissima (Cumings, 1906). For explanation of abbreviations of char- acters (left column), see Table 8b (foldout inside back cover). number of mea- coeffi- sure- standard cient of observed ments mean deviation variation range 1. WB 24 0.2015 010919 055172029 00095207550) 2. DBC 24 0.5023 0.0804 16.01 0.333-0.678 3. WD 24 0.1774 0.0353 19:90 -0:127-0:255 4. LF 24 0.6335 0.0736 11.62 0.500-0.777 5. WF 24 0.2513 0.0467 18.58 0.153-0.343 6. AF 24 379 0.61 18.70 2-4 7. AL 24 0.1006 0.0035 3.48 0.094-0.109 8. AW 24 0.0895 0.0044 4.92 0.080-0.096 9. ADB 24 0.2304 0.0252 10.94 0.188-0.295 10. AAB 24 0.2302 0.0248 10.77 0.187-0.283 11. ABB 24 0.2974 0.0501 16.85 0.198-0.397 12. DN 24 0.0756 0.0155 20.50 0.048-0.113 14. SNB 24 0.3258 0.1038 31.86 0.178-0.527 15. WK 24 0.0400 0.0110 27.50 0.010-0.059 16. DSO 24 0.0060 0.0012 20.00 0.004-0.009 17. SSO 24 0.0468 0.0156 33.33 0.022-0.067 18. WP 24 0.0226 | 0.0032 14.16 0.017-0.030 19. SA 24 4.33 0.89 20.48 3-6 20. SAD 24 0.0065 0.0019 29.23 0.004-0.011 22. RSS 24 0.0167 0.0026 15.57 0.012-0.021 24. SSS 24 0.0500 0.0112 22.40 0.022-0.088 30. OL 12 0.2500: 0.0211 8.44 0.222-0.267 31. OW 12 0.2000 0.0183 9.15 0.187-0.225 32. TRW 24 0.0071 0.0020 28.17 0.004-0.011 33. TLW 24 0.0138 0.0026 18.84 0.009-0.018 35. RWT 24 0.0442 0.0284 64.25 0.007-0.123 36. CL 24 OSO QUO 5.11 0.197-0.238 37. CD 24 01052 0.0102 9.70 0.089-0.126 38. MAW 24 010552 00079 7.49 0.091-0.118 39. MIW 24 0.0635 0.0071 11.18 0.050-0.074 40. VD 24 0.0431 0.0124 28.77 0.019-0.062 41. RA 24 67.79 5052 8.15 55-78 42. LA 24 23.42 4.53 19.34 17-33 43. TB 24 0.1957 0.0316 16.15 0.150-0.257 Interior description.—Branches ovate to semicircu- lar in transverse view, flattened on obverse surface, elongate parallel to plane of zoarial surface. Branch thin, moderately regular in thickness. Autozooecial living chamber size lower-end inter- mediate, chambers biserially arranged in alternating rows along planar branch axial wall; axial wall anas- tomosing toward sites of lateral-wall emplacement near reverse wall; axial wall becoming relatively straight with moderate inflections toward lateral walls in mid chamber and near obverse surface. Chamber longest dimension paralleling reverse wall in proximodistal direction. Autozooecial chamber outline irregularly pentagonal near reverse wall and toward mid chamber, becoming irregularly elliptical near obverse side of chamber; ellipse bilobate near obverse surface due to initiation of superior hemiseptum at proximal-abaxial edge of vestibule, longest direction of ellipse oriented distal-abaxially; chamber shape highly uniform. Ap- MISSISSIPPIAN BRYOZOANS: SNYDER 47 erture positioned at distal-abaxial end of chamber, connected to chamber by relatively short vestibule of variable length. Ratio of autozooecial chamber mini- mum width to maximum width 3:5; dimensions of maximum width and depth equal; ratio of depth to length of chamber approximately 1:2. Inferior hemi- septum lacking; small, reduced superior hemiseptum formed as slight extension of proximal-adaxial vestib- ular edge, forming very slight restriction between ves- tibule and autozooecial chamber. Autozooecial cham- ber diverges laterally from middle of branch at highly variable angle (mean of 23°); from reverse wall at con- Stant angle (mean of 68°). Heterozooecia rare, probably Ovicells; slightly longer than autozooecia and twice au- tozooecial width. Three-dimensionally reconstructed autozooecial chamber form moderately cuneate with rounded acute angles at proximal and distal ends of chamber, obtuse angle toward branch midline; elongate as viewed from obverse surface, approximately equi-dimensional in depth and width as viewed from distal and lateral edges of branch respectively. Internal granular skeletal layer thin, continuous with obverse nodes, stylets, keel, peristome, apertural sty- lets, reverse longitudinal striae, stylets across dissepi- ment, in middle of zoarial supports. Moderate asto- genetic thickening of lamellar skeleton toward proximal end of zoarium. Remarks.— Autozooecial chamber shape in this spe- cies is quite similar to that of R. multispinosa (Ulrich, 1890), indicating close affinities. Dimensions of the chamber are different, as are the general mesh dimen- Sions and symmetry. Chamber dimensions are similar to those of R. tenax (Ulrich, 1888). Exterior similarities are greatest between R. tenuissima and R. tenax. Ev- idence supporting emphasis on internal features for taxonomic assignment is strong. Fenestella stocktonensis Condra and Elias, 1944 was Separated from Fenestella tenuissima Cumings, 1906 by Condra and Elias. My analysis of stocktonensis in- dicated it was insufficiently different from tenuissima to justify separation as a new species, and it is therefore Placed in synonymy here. R. tenuissima is separated from other rectifenestel- lids by larger aperture size, ovate shape of aperture, Slightly larger autozooecial chambers, slightly different Shape of autozooecial chambers, and mesh dimensions and symmetry. Material studied.—Twenty-five exterior fragments; Six sectioned specimens; largest zoarial fragment 12 x 22 mm (width to length). Fragments examined were mod- erately well-preserved, although many zoarial frag- Ments were broken due to their delicate nature. Occurrence.—R. tenuissima is relatively rare at the Valmeyer, St. Louis, and White Hall localities, with Table 12.—Summary numerical analysis of Rectifenestella mul- tispinosa (Ulrich, 1890). For explanation of abbreviations of char- acters (left column), see Table 8b (foldout inside back cover). number of mea- coeffi- sure- standard cient of observed ments mean deviation variation range 1. WB 24 0.2606 0.0437 16.77 0.200-0.356 2. DBC 24 0.4096 0.0629 15.36 0.294-0.540 3. WD 24 0.1218 0.0226 18.56 0.085-0.188 4. LF 24 0.3576 0.0478 13.37 0.290-0.468 5. WF 24 0.2101 0.0307 14.61 0.140-0.266 6. AF 24 2) 0.44 16.77 2-3 7. AL 24 0.1174 0.0071 6.05 0.102-0.129 8 AW 24 0.0968 0.0057 5.89 0.086-0.110 9. ADB 24 0.2342 0.0190 8.11 0.184-0.260 10. AAB 24 0.2248 0.0222 9.88 0.191-0.278 11. ABB 24 0.2135 0.0419 19.63 0.122-0.308 12. DN 24 0.0834 0.0182 21.82 0.056-0.125 14. SNB 24 0.1743 0.0300 17.21 0.112-0.234 15. WK 24 0.0326 0.0059 18.10 0.021-0.044 16. DSO 24 0.0076 0.0018 23.68 0.005-0.011 17. SSO 24 0.0514 0.0197 38.33 0.029-0.164 18. WP 24 0.0119 0.0029 24.37 0.008-0.015 22. RSS 24 0.0081 0.0027 33.33 0.005-0.014 24. SSS 24 0.0324 0.0083 25.62 0.020-0.046 32. TRW 24 0.0063 0.0009 13.65 0.005-0.009 33. TLW 24 0.0065 0.0009 13.54 0.005-0.009 34. FWT 24 0.0880 0.0398 45.23 0.036-0.171 35. RWT 24 0.0684 0.0268 39.18 0.012-0.124 36. CL 24 0.2605 0.0117 4.49 0.234—0.286 37. CD 24 0.1511 0.0080 5.29 0.136-0.167 38. MAW 24 0.1461 0.0159 10.88 0.118-0.188 39. MIW 24 0.0887 0.0165 18.60 0.061-0.130 40. VD 24 0.0811 0.0250 30.83 0.041-0.126 41. RA 24 09:92 5.18 7.40 62-81 42. LA 24 23:25 3.51 15.08 17-31 43. TB 24 0.3436 0.0460 13.39 0.249-0.411 occurrence restricted to the Lower Warsaw. It occurs in both limestones and shale, and is more frequent in the latter. Type Material.— Unknown. Hypotypes.— UI X-6832-6836, 6891 (loc. 49B, sam- ples 8, 10, 15). Rectifenestella multispinosa (Ulrich, 1890) Plate 4, figures 1-13, Plate 5, figures 1-3; Table 12 Fenestella multispinosa Ulrich, 1890, pp. 540-541, pl. 50, figs. 3- 3c; Cumings, 1906, pp. 1278-1279, pl. 29, figs. 1, la, 1b, 1d; Nekhoroshev, 1926, pp. 1245-1246, pl. 19, figs. 5- 6; pl. 20, fig. 3; Nikiforova, 1927, pl. 178; Nikiforova, 1933, p. 16; Kaisin, 1942, p. 93; Condra and Elias, 1944, pp. 110-112, pl. 33, figs. 1- 4; Shulga-Nesterenko, 1951, p. 85; Trizna, 1958, p. 129, pl. 36, fig. 4; pl. 37, figs. 1-5; Miller, 1962, p. 121; Tavener-Smith, 1973, pp. 416-418, pl. 3, figs. 1-9. Fenestrellina multispinosa (Ulrich). McFarlan, 1942, p. 444. Diagnosis.—Zoarium robustness intermediate, mesh close, pattern regular; branches delicate, width narrow, thickness intermediate, straight to broadly curved; transversely circular to ovate, closely spaced; branches 48 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 joined at regular intervals by thin, short dissepiments; dissepiments emplaced at highly regular intervals. Fe- nestrules small; shape rectangular to elliptical, mod- erately variable in shape. Autozooecial aperture size intermediate, shape circular to ovate, elongate proxi- modistally; peristome thin, well-developed, complete; two to three (most commonly two) apertures per fe- nestrule. Single narrow, continuous keel along middle of obverse branch, atop which are positioned inter- mediate-size circular to ovate nodes. Autozooecial chamber size intermediate, emplaced in two rows, ex- cept third row at sites of branch bifurcation; chamber outline attaining an irregularly pentagonal shape throughout most of chamber depth, becoming bilo- bate-elliptical near obverse surface. Chambers elongate proximodistally, parallel to reverse wall. Aperture at distal-abaxial end of chamber, connected to chamber by relatively long, variable-length vestibule. Short su- perior hemiseptum at proximal vestibular edge, infe- rior hemiseptum absent. Lateral-wall budding-angle moderately variable (mean of 23°); reverse-wall bud- ding-angle highly constant (mean of 70°). Table 12 presents statistical criteria used in species delimitation. Exterior description.—Zoarium robustness inter- mediate, expansion flat, planar to slightly obversely curved, fan-shaped; mesh close; pronounced astoge- netic thickening of both obverse and reverse zoarial skeleton; external zoarial pattern regular. Probable ma- ture widths 12 to 15 mm, lengths 18 to 25 mm. Branches delicate; width narrow, relatively variable; branches most commonly straight, although locally broadly curved toward lateral edge of zoarium. Branches closely spaced, distance between adjacent branch centers regular. Obverse surface slightly gran- ular in texture, becoming increasingly so with astogeny, surface rounded; except for presence of single keel which is narrow, well-developed, continuous, relatively straight, extending along branch midline causing pos- itive inflection in obverse surface profile. Keel width increasing with astogeny. Nodes monoserially em- placed, well-developed and of intermediate size; node shape circular to ovate, elongate proximodistally when ovate; size and shape relatively regular; nodes develop as projections from middle of keel; two to three per fenestrule length, three most common; nodes evenly, closely spaced; diameter increasing with astogeny. Small, variable-size stylets irregularly positioned along obverse surface. Reverse surface texture relatively granular, coarsening with astogeny, bearing numerous intermediately spaced longitudinal striae which be- come covered by astogenetic thickening of lamellar skeleton; rows of closely spaced small microstylets be- _ come larger, more irregularly positioned along reverse branch surface with astogeny. Two rows of autozooecia across branch, except third row at sites of branch bi- furcation where middle autozooecium evidently shared by both branches; pronounced thickening proximal, thinning distal to sites of branch bifurcation. Hetero- zooecia absent in all zoarial fragments observed. Dissepiments thin, slightly less than half branch width, moderately constant in width; short, relatively constant in length; connect branches at highly regular intervals. Dissepiments barlike, with moderate medial thinning; highly recessed from obverse surface, even with reverse. Moderate to pronounced astogenetic thickening of dissepiments. Obverse dissepiment sur- face lacking ornamentation; reverse surface with lon- gitudinal striae atop which are emplaced closely spaced rows of small microstylets; striae becoming obscured by thickened lamellar skeleton with astogeny, micro- stylets increase in diameter. Obverse dissepiment sur- face texture slightly granular, reverse relatively gran- ular, both coarsening with astogeny. Dissepiment emplacement ranging from perpendicular to up to 20° from perpendicular to branch length. Apertures com- monly open on proximal or distal edge or in middle of dissepiment edge at branch-dissepiment contact; arranged symmetrically or asymmetrically between branches. Fenestrules small, shape rectangular to elliptical, elongate proximodistally; moderately variable in shape, regular in size; expanding in width and length in ob- verse-reverse direction. Mean width of fenestrule slightly less than branch width on obverse surface, ap- proximately equal on reverse; fenestrule opening be- coming smaller toward proximal end of zoarium with astogenetic thickening of lamellar skeleton. Ratio of mean fenestrule width to length approximately 3:5; constancy of length and width approximately equal. Two to three apertures per fenestrule length, two most common; distance between closest aperture centers along branch, across branch, across fenestrule approx- imately equal, forming relatively uniform grid of ap- erture openings over obverse surface; spacing along branch and across branch constant, spacing across fe- nestrule variable. Autozooecial apertures intermediate in size, shape circular to ovate, elongate proximodistally and slightly enlarged at distal end; opening most commonly ori- ented parallel to obverse surface, in some tilting toward fenestrule at slight angle; thin, well-developed com- plete peristome present. Aperture margin with pro- nounced extension into fenestrule, causing extreme in- flections in fenestrule outline on obverse surface. In late astogeny toward proximal end of zoarium, some apertures become capped by thin terminal diaphragm. Well-developed zoarial supports form as extensions of reverse zoarial surface and lateral edge of zoarium. Interior description.— Branches circular to ovate in MISSISSIPPIAN BRYOZOANS: SNYDER 49 transverse section, asymmetrically thickened on ob- verse surface through astogenetic thickening of lamel- lar skeleton and presence of keel and nodes; elongate parallel to zoarial surface. Branches intermediate, moderately constant in thickness. Autozooecial living chambers of intermediate size, biserially arranged in alternating rows along planar branch axial wall; axial wall sinuous, anastomosing toward and connecting with chamber lateral walls; ax- ial wall sinuous throughout chamber depth. Chamber longest dimension parallels reverse wall in proximo- distal direction. Autozooecial chamber outline irreg- ularly pentagonal near reverse wall and throughout most of chamber depth, becoming bilobate-elliptical near obverse surface, curved abaxially; chamber shape high- ly uniform. Aperture positioned at distal-abaxial end of chamber, connected to chamber by relatively long, well-developed vestibule of variable length. Ratio of autozooecial chamber minimum width to maximum width 3:5; maximum chamber width and depth ap- proximately equal; ratio of chamber depth to length approximately 3:5; chamber length and depth highly constant, minimum and maximum widths slightly variable. Short superior hemiseptum at proximal ves- tibular edge; inferior hemiseptum lacking. Autozooe- cial chambers diverge laterally from middle of branch at moderately variable angle (mean of 23?); from re- Verse wall at highly constant angle (70?). Three-dimensionally reconstructed chamber form moderately cuneate with pronounced angular exten- sion toward branch midline; long dimension as viewed from Obverse surface, approximately equidimensional In depth and width as viewed from distal and lateral edges of branch respectively. Internal granular skeleton relatively thin, continuous With obverse keel, nodes, stylets, and peristomes; re- Verse longitudinal striae and microstylets, across dis- Sepiments and in the middle of zoarial supports. As- togenetic thickening of lamellar skeletal layer Pronounced, most pronounced toward proximal end Of zoarium. Remarks. — R. multispinosa can be readily differ- entiated from R. tenax (Ulrich, 1888) and R. tenuis- Sima (Cumings, 1906) by the much greater size of its autozooecial chamber, although chamber shape closely resembles that of the two other rectifenestellids. Ap- *rture size is also greater in R. multispinosa than in the other rectifenestellid species. Interior appearance alone allows differentiation of R. multispinosa from R. lenuissima, but separation of these species based solely on exterior features is almost impossible because of Similarity in symmetry of mesh and associated char- acters. This species has been reported from geographically Widely separated areas, suggesting misidentification due to reliance on exterior characters. To determine wheth- er all species have been accurately assigned to R. mul- tispinosa requires section and reanalysis of all speci- mens. Material studied.—Thirty exterior fragments, five sectioned specimens; largest zoarial fragment 10 x 12 mm (width to length). Preservation excellent in some fragments, poor due to crushing in others. Occurrence.—Common in Warsaw study area; most abundant in shaly beds, although not restricted to this facies. Syntypes.—USNM 43349, 43350. Several speci- mens are illustrated in Ulrich (1890, pl. 50, figs. 3, 3a, 3b, 3c, 3d). Figured and/or measured specimens.—UI X-6734, 6872, 6874, 6870 (loc. 10, samples 16, 31), 6949 (loc. 49B, sample 12). Genus LAXIFENESTELLA Morozova, 1974 Text-figure 9 Type species.— Fenestella sarytshevae (Shulga-Nes- terenko, 1951) [Lower Carboniferous, Namurian Stage; Russian Platform]. Morozova, 1974, pp. 173-174; pls. 3-2. Typical Warsaw species. — Laxifenestella coniuncti- styla, n. sp. Osagean-Meramecian throughout Missis- sippi River Valley outcrop area. Diagnosis.— Zoarium robustness intermediate, mesh spacing close to intermediate; rectangular, parallelo- gram-shaped, irregularly pentagonal to elliptical cham- ber outline in mid tangential section, chamber size intermediate; aperture size small to intermediate; moderate to well-developed superior hemiseptum, well- developed inferior hemiseptum present; chamber re- verse-wall budding-angle means vary between 57? and v Three-dimensionally reconstructed chamber form rounded box- to box-like with indentations caused by hemiseptal positioning (Text-fig. 9). Description.— Zoarium robustness intermediate, ex- pansion flat to obversely curved, mesh spacing close to intermediate, extremely regular. Branch width narrow to wide, straight to sinuous in trace with lateral branches broadly curved toward edge of zoarium; branch surface flat to rounded. Keel pres- ent, single, width narrow, increasing with astogeny and frequently covered by lamellar skeleton. Nodes pres- ent, emplacement monoserial, size intermediate to large, shape circular to ovate, located atop keel in single or alternating rows, spacing close to intermediate. Ob- verse stylets present, size small to extremely small, occurring across obverse surface. Microstylets present, ranging in size from small to large. Macrostylets pres- ent in some species, large, typically located at site of 50 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 branch-dissepiment junction. Autozooecia in two rows, third row at site of branch bifurcation or three rows for distance along branch proximal to branch bifur- cation. Heterozooecia (ovicells?) present in some spe- cies. Dissepiments of intermediate width, length short to intermediate, connect branches at regular to variable intervals. Fenestrule size small to intermediate, shape ovate to elliptical to approaching rectangular. Aperture size small to intermediate, shape circular to ovate, oriented parallel to plane of obverse surface. Peristome present, either complete or incomplete; ap- ertural stylets absent; terminal diaphragms present, primarily occurring toward proximal end of zoarium. Branch shape in cross-section ranging from circular to ovate, shallow to thick in depth. Autozooecial chamber size intermediate, chambers biserially emplaced along straight to sinuous axial wall; maximum chamber length extending proximodistally, parallel to reverse wall. Chamber outline irregularly ovate to elliptical near reverse wall, becoming a rect- angle, parallelogram, irregular pentagon to elliptical in mid and throughout most of chamber depth, bilobate- elliptical to bilobate-ovate near obverse surface. Ves- tibule present, varying in length from short to long. Superior hemiseptum present, moderately to well-de- veloped, positioned at proximal vestibular edge; in- ferior hemiseptum present, well-developed, positioned on middle of reverse and lateral proximal wall, supe- rior and inferior hemisepta frequently fused in mid chamber. Lateral-wall budding-angle means ranging from 20° to 27°; reverse-wall budding-angle means from 57° to 77°. Lamellar skeletal layer thin to thick, exhib- iting moderate to pronounced astogenetic thickening; granular skeletal layer thickness intermediate to thick, exhibiting no astogenetic thickening. Three-dimensionally reconstructed chamber form rounded box- to box-like, with indentations in “box” caused by hemiseptal positioning near mid chamber. Text-figure 9 illustrates zoarial outlines in longitu- dinal, tangential, and transverse orientations and three- dimensional chamber reconstructions from distal, ab- axial branch edge, and obverse surface views. Remarks.—This genus is readily characterized by fused inferior and superior hemisepta in conjunction with chamber shape, anastomosing keel, and closely to intermediately spaced intermediate-size nodes. The limited diagnosis and illustrations available in Mo- rozova (1974) seem to agree with a generic grouping established in the Warsaw materials studied, and thus I use her genus herein. The general age of species she assigned to this genus also agree with my own mate- | rials. The use of the generic name is somewhat ten- tative because of Morozova's lack of three-dimension- al approach in the establishment of the genus and the inaccessibility of her study samples. The more highly anastomosing nature of branches and short, wide dissepiments in Laxifenestella fluc- tuata, n. sp. correspond with characters of Flexifenes- tella Morozova, 1974. However, internal analysis of L. fluctuata shows no appreciable difference between this species and the rest of the species of Laxifenestella found in the Warsaw, thus suggesting the genus Flex- ifenestella is probably synonymous with Laxifenestel- la. Detailed three-dimensional analysis of the type spe- cies of these two genera could lead to conclusive determination as to whether they are indeed synony- mous. Specific composition.— Approximately 70 species of Laxifenestella were recognized by Morozova. Herein, four species are assigned to this genus: L. coniuncti- styla, L. maculasimilis, n. sp., L. serratula (Ulrich, 1890), and L. fluctuata. Range.— Devonian-Lower Mississippian-Perm- ian(?); Permian species differ greatly from those in the Lower Mississippian, and might be better assigned to a separate genus (Morozova, 1974). Laxifenestella coniunctistyla, new species Plate 5, figures 4-12, Plate 6, figures 1-8, Plate 7, figures 1, 2; Table 13 Etymology of name.— Named for the occurrence of the stylet in the middle of the dissepiment. Diagnosis.— Zoarium robustness intermediate, mesh spacing close, pattern extremely regular; branch ro- bustness and width intermediate, thickness medium, trace straight to rarely broadly curved, transversely circular to rarely elliptical, closely spaced. Branches Text-figure 9.— Laxifenestella coniunctistyla illustrated. 1, dia- grammatic longitudinal section illustrating changing chamber out- line from deep section near middle of branch (bottom of figure) to shallow section near abaxial edge of branch (top of figure) [Inferior hemisepta well-developed, bridging reverse to obverse chamber walls (arrow) near the obverse surface in this species.], x 70; 2, diagram- matic tangential section showing changing chamber outline from deep section near reverse-wall budding-site (bottom of figure) to shallow section near obverse surface (top of figure) [Well-developed superior hemiseptum is illustrated in this view (arrow).], x 70; 3, diagrammatic transverse section across branch showing typical ori- entation of aperture relative to plane of obverse surface (arrow), x 70; 4, diagrammatic transverse section illustrating well-developed inferior hemiseptum (arrow), x 70; 5, reconstruction oftypical cham- ber shape (three-dimensional) as viewed from distal end of branch; chamber reconstructed is from the right side of the branch [Observe indentation caused by near connection of inferior and superior hem- isepta (arrow).], x 140; 6, reconstruction of typical chamber shape (three-dimensional) as viewed from abaxial edge of branch, showing indentation caused by the inferior and superior hemisepta (arrow), x 140; 7, reconstruction of typical chamber shape (three-dimension- al) as viewed from the obverse surface; chamber reconstructed is from the right side of the branch [Hemiseptal inflections into cham- ber outline are evident in this view (arrow).], X 140. MISSISSIPPIAN BRYOZOANS: SNYDER 51 connected at highly regular intervals by lower-end in- termediate width, short dissepiments. Fenestrule size intermediate; shape elliptical to approaching rectan- gular, moderately regular. Autozooecial aperture size intermediate, shape circular, surrounded by well-de- veloped complete peristome; two to four (most com- monly three) apertures per fenestrule. Single narrow keel along middle of obverse branch, atop which are positioned intermediate-size, circular to ovate nodes. Autozooecial chamber size intermediate, chambers emplaced in two rows, except third row at sites of branch bifurcation; outline elliptical near reverse wall, rapidly becoming a rectangle to parallelogram through- out mid and most of chamber, irregularly bilobate- elliptical near obverse surface. Chambers elongate proximodistally, parallel to reverse wall. Aperture at distal-abaxial end of chamber, connected to chamber by intermediate-length moderately variable vestibule. Both superior and inferior hemisepta present, well- developed, occasionally fuse along chamber abaxial wall restricting chamber opening. Lateral-wall bud- ding-angle moderately variable (mean of 20°); reverse- wall budding-angle highly constant (mean of 57°). Table 13 presents statistical criteria used in delim- iting this species. Exterior description.—Zoarium robustness inter- mediate; expansion flat to broadly obversely curved; mesh spacing close; pronounced astogenetic thickening of both obverse and reverse zoarial skeleton; zoarial pattern extremely regular. Probable mature widths 15 to 25 mm, lengths 20 to 35 mm. Branch robustness intermediate; width intermedi- ate, relatively variable; trace generally straight, more rarely broadly curved toward lateral zoarial edge, oc- casionally exhibiting slight inflections toward sites of dissepiment insertion. Branch spacing close, extremely regular. Obverse surface texture granular; surface rounded except single narrow, well-developed keel; keel continuous, straight to slightly anastomosing toward sites of dissepiment emplacement, extending along branch midline and causing positive inflection on ob- verse surface profile; keel thins toward distal end of zoarium, thickening toward proximal end with asto- geny. Single row of well-developed intermediate size nodes, circular to ovate, elongate proximodistally, pro- jecting from middle of keel; size and shape of nodes moderately regular; four to seven nodes per fenestrule length, five most common; closely, moderately evenly spaced; node diameter increasing with astogeny. Ex- tremely small, irregularly sized and positioned stylets across entire obverse branch surface. Reverse surface texture granular, bearing a moderate number of rows of intermediately spaced longitudinal striae; striae cov- ered by lamellar skeleton with astogeny; rows of ex- tremely small, closely spaced microstylets extend along branch surface; microstylet size irregular, diameter and positioning of microstylets not affected by astogeny. Autozooecia in two rows, except third row at sites of branch bifurcation where middle autozooecium is ev- idently shared by both developing branches; slight to intermediate thickening of branches proximal, thin- ning distal to sites of branch bifurcation. Heterozooe- cia not observed in any specimen examined. Dissepiments of lower-end intermediate width, slightly greater than half branch width, width moder- PALAEONTOGRAPHICA AMERICANA, NUMBER 57 Table 13.—Summary numerical analysis of Laxifenestella coni- unctistyla, n. sp. For explanation of abbreviations of characters (left column), see Table 8b (foldout inside back cover). number of mea- coeffi- sure- standard cient of observed ments mean deviation variation range 1. WB 24 0.3453 0.0553 16.02 0.263-0.456 2. DBC 24 0.5430 0.0690 12.71 0.456-0.719 3. WD 24 0.1882 0.0542 28.80 0.119-0.300 4. LF 24 0.7337 0.0738 10.06 0.563-0.875 5. WF 24 0.2429 0.0608 25.03 0.150-0.388 6. AF 24 3.08 0.65 viri p 24 7. AL 24 0.1035 0.0037 3.57 0.098-0.110 9. ADB 24 0.2995 0.0178 5.94 0.268-0.337 10. AAB 24 0.2890 0.0257 8.89 0.236-0.328 11. ABB 24 0.3779 0.0591 15.64 0.278-0.497 12. DN 24 0.0961 0.0184 19.15 0.065-0.130 13. DND 24 0.0882 0.0185 20.98 0.060-0.125 14. SNB 24 0.2087 0.0473 22.66 0.128-0.287 15. WK 24 0.0139 0.0021 15.11 0.012-0.018 16. DSO 24 0.0029 0.0010 34.48 0.002-0.005 17. SSO 24 0.0113 0.0039 30.00 0.007-0.020 18. WP 24 0.0125 0.0021 16.80 0.008-0.016 22. RSS 24 0.0036 0.0011 30.56 0.002-0.005 24. SSS 24 0.0124 0.0036 29.03 0.009-0.029 32. TRW 24 0.0102 0.0016 15.29 0.007-0.014 33. TLW 24 0.0106 0.0017 16.13 0.007-0.014 34. FWT 24 0.0463 0.0266 57.45 0.014-0.103 36. CL 24 0.2634 0.0078 2.96 0.251-0.278 37. CD 24 0.1709 0.0091 5.32 0.157-0.189 38. MAW 24 0.1480 0.0173 11.69 0.119-0.185 40. VD 24 0.0844 0.0170 20.14 0.046-0.123 41. RA 24 56.83 4.03 7.09 50-64 42. LA 24 20.00 3:13 15.64 15-28 43. TB 24 0.3233 0.0407 12.64 0.271-0.381 ately variable; length short, moderately variable; con- nect branches at highly regular intervals. Dissepiments exhibit slight medial thinning, slight flaring at dissep- iment-branch contact; slightly recessed from both ob- verse and reverse zoarial surfaces. Pronounced asto- genetic thickening of dissepiments, nearly tripling in width toward most proximal end of zoarium. Obverse dissepiment surface with one or two thick longitudinal striae across dissepiment perpendicular to branch length; one well-developed, intermediate size, ovate node atop longitudinal striae, node elongate parallel to striae in mid center of dissepiment; reverse dissepi- ment surface with rows of longitudinal striae atop which are positioned small stylets, stylets covered by lamellar skeleton with astogeny; both obverse and reverse dis- sepiment surface texture granular. Dissepiment em- placement perpendicular or nearly perpendicular to branch length. Apertures commonly open on proximal or distal edge or in middle of dissepiment edge at branch-dissepiment contact; arranged symmetrically or asymmetrically between branches. Fenestrule size intermediate; shape elliptical to ap- proaching rectangular, elongate proximodistally; mod- 2 ee Ge MISSISSIPPIAN BRYOZOANS: SNYDER 53 erately regular in shape; expanding slightly in width and length in obverse-reverse direction. Mean width of fenestrule seven-tenths branch width; fenestrule width and length decreasing toward proximal end of Zoarium due to astogenetic thickening of lamellar skel- eton. Ratio of fenestrule width to length ranging from 1:5 to 1:2, variable; mean ratio of 1:3 most common; length much more constant than width. Two to four apertures per fenestrule length, three most common; distance between closest aperture centers along branch and across branch approximately equal, spacing of ap- erture centers across fenestrule normally much greater, variable, ranging from slightly less than that along and across branch to almost twice that distance. Autozooecial aperture size intermediate, shape cir- cular, highly uniform; opening oriented parallel to plane of obverse surface; thin, well-developed continuous Peristome around aperture. Aperture margin extends Into fenestrule, causing moderate inflections in fenes- trule outline on obverse surface. Centrally thickened terminal diaphragms commonly occurring toward Proximal end of zoarium. Extremely well-developed zoarial supports develop as extensions of reverse zoarial surface and lateral edge of zoarium; most common toward proximal end of Zoarium. Interior description. —Branches approximately cir- Cular in transverse section, rarely elliptical, slightly elongate parallel to zoarial surface. Branches medium, relatively constant in thickness. _Autozooecial living chambers intermediate in size, biserially arranged in alternating rows along a predom- Mantly straight, planar to slightly sinuous branch axial wall, with inflections extending toward and connecting with lateral wall. Chamber maximum dimension par- allel to reverse wall in proximodistal direction. Au- tozooecial chamber outline elliptical near reverse wall; Tapidly becoming a rectangle to parallelogram, with longest dimension toward outer edge of chamber, in the middle and throughout most of chamber; chamber "regularly bilobate-elliptical near obverse surface, longest direction of ellipse oriented slightly distal- abaxially; chamber shape regular. Aperture located at distal-abaxial end of chamber, connected to chamber by intermediate-length, moderately regular vestibule. Ratio of chamber width to depth approximately 7:8; depth to length ratio 5:8; length and depth much more Consistent than width. Well-developed superior hemi- Septum forms as extension of proximal interior ves- ubular edge; superior hemiseptum directed toward the Teverse wall in a distal direction, curves around the Vestibule inner edge. Inferior hemiseptum located in Mid chamber along reverse wall, extending across en- üre chamber width; toward obverse surface, inferior €miseptum extends as a ridge along abaxial edge of chamber wall. Superior and inferior hemisepta occa- sionally fuse along chamber abaxial wall; positioning of these hemisepta restricts opening between auto- zooecial chamber and inner vestibule edge. Autozooe- cial chamber diverges laterally from mid chamber at a moderately variable angle (mean of 20°); from reverse wall at a highly constant angle (mean of 57°). Three-dimensionally reconstructed chamber form box-like with indentations in “box” caused by hemi- septal positioning; long dimension as viewed from ob- verse surface, depth as viewed from distal end of zoar- ium slightly greater than width as viewed from lateral edge of branch. Internal granular skeletal layer moderately thick, ex- hibiting slight astogenetic thickening in autozooecial chamber, continuous with obverse nodes, stylets, peri- stome and keel; reverse longitudinal striae and stylets; across dissepiments and in the middle of zoarial sup- ports. Outer lamellar layer initially thin, with extreme thickening during astogeny as observed toward prox- imal end of zoarium. Remarks.— General autozooecial chamber shape and presence of inferior and superior hemisepta in this spe- cies are also typical of several other Warsaw species including L. serratula (Ulrich, 1890), L. maculasimilis, n. sp., and L. fluctuata, n. sp. Hemisepta provide a chamber which offers protection against predators and adverse environmental conditions. Similar hemiseptal shapes, and the way in which they restrict the chamber, suggest physical similarities among the polypides of different species. Phylogenetic affinities between these species would seem close, probably closer than be- tween groups of fenestellids that do not have such ex- tensive hemiseptal development. For these among oth- er reasons, these species are herein all assigned to Laxifenestella. L. coniunctistyla is readily distinguished from the other laxifenestellids by the presence of a well-devel- oped, intermediate-size node occurring in the middle of each dissepiment, a larger apertural opening, dis- tinctive mesh dimensions, and characteristic auto- zooecial chamber dimensions. A very similar species was discovered in material collected by Cumings from the Salem Formation at Dark Hollow near Bloomington, Indiana and con- tained in collections at Indiana University. This spe- cies was not described in suites collected by Ulrich. Material studied.— Forty-four exterior fragments; nine sectioned specimens; largest zoarial fragment 18x28 mm (width to length). Excellent preservation observed in collected specimens. Occurrence.— Laxifenestella coniunctistyla, n. sp. is abundant in the Warsaw throughout the study area. Slight differences do exist between northern and south- ern specimens. Northern specimens consistently have 54 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 a slightly tighter mesh, but this difference is not ade- quate for species separation as it does not affect the internal chamber dimensions. The species is found in both calcarenite and shale facies. Holotype.— UI X-6790 (loc. 49B, sample 12). Paratypes.— UI X-6784—6789 and 6801 (loc. 49B, samples 12, 13, 17) UI X-6791, 6792 (loc. 10, sample 25): Laxifenestella maculasimilis, new species Plate 7, figures 3-9, Plate 8, figures 1-10, Plate 9, figures 1, 2; Table 14 Etymology of name.—The name refers to the similar external mesh symmetry between this species and spe- cies of Archimedes. Diagnosis.—Zoarium robustness intermediate, mesh intermediate, pattern extremely regular; branch ro- bustness intermediate, width narrow to lower-end in- termediate, thickness medium, branches straight to slightly sinuous toward sites of dissepiment emplace- ment, lateral branches often broadly curved toward edge of zoarium; branches transversely circular to ovate, closely spaced. Branches joined at highly regular in- tervals by intermediate-width, intermediate-length dissepiments. Fenestrule size intermediate, shape el- liptical to approaching rectangular, moderately irreg- ular. Autozooecial apertures small, circular, surround- ed by thin, well-developed incomplete peristome open only at proximal-adaxial edge; two to four (most com- monly three) apertures per fenestrule. Single narrow keel along middle of obverse branch, atop which are positioned intermediate-size, ovate nodes. Autozooe- cial chamber size intermediate, chambers emplaced in two rows, except third row at sites of branch bifurca- tion; outline irregularly ovate near reverse-wall bud- ding-site; rapidly expanding, becoming a parallelogram throughout mid chamber; bilobate-ovate near obverse surface. Chambers elongate proximodistally, parallel to reverse wall. Apertures at distal-abaxial end of chamber, connected to chamber by short, variable- length vestibule. Superior hemiseptum moderately well- developed, inferior hemiseptum well-developed, oc- casionally both fuse along chamber abaxial wall, re- stricting chamber opening. Lateral-wall budding-angle relatively constant (mean of 23°); reverse-wall bud- ding-angle highly constant (mean of 66°). Heterozooe- cia (ovicells?) occurring as intermediate size enlarge- ments between apertures. Table 14 presents statistical criteria used in delim- iting this species. Exterior description.—Zoarium robustness inter- mediate; generally forming a flat fan-shaped expan- sion, rarely slightly obversely curved; mesh spacing intermediate; moderate astogenetic thickening of both obverse and reverse zoarial skeleton; zoarial mesh pat- tern extremely regular. Probable mature widths of 10 Table 14.—Summary numerical analysis of Laxifenestella mac- ulasimilis, n. sp. For explanation of abbreviations of characters (left column), see Table 8b (foldout inside back cover). number of mea- - sure- standard cient of observed ments mean deviation variation range 1. WB 24 0.2997 0.0724 24.16 0.169-0.481 2. DBC 24 0.5203 "0.0513 9.86 | 0.450-0.650 3. WD 24 0.1676 0.0226 13.48 0.138-0.223 4. LF 24 0.6196 0.0646 10.43 0.457-0.730 5. WF 24 0.3118 0.0692 22.19 0.213-0.444 6. AF 24 3.08 0.50 16:33 2-4 7. AL 24 0.0759 0.0048 6.32 0.062-0.082 9. ADB 24 0.2552 0.0224 8.78 | 0.205-0.300 10. AAB 24 0.3010 0.0283 9.40 0.250-0.373 11. ABB 24 0.2567 0.0310 12.08 0.207-0.400 12. DN 24 0.1066 0.0250 23.45 0.060-0.163 14. SNB 24 0.5084 0.1416 27.85 0.288-0.747 15. WK 24 0.0199 0.0046 23.12 0.014-0.030 16. DSO 24 0.0085 0.0014 16.47 0.006-0.020 17. SSO 24 0.0163 0.0053 32.52 0.012-0.037 18. WP 24 0.0094. 0.0019 20.21 0.006-0.014 21. RSL 24 0.1421 0.0267 18.79 0.100-0.208 22. RSS 24 0.0283 0.0072 25.44 0.012-0.063 23. SSL 24 0.7627 0.2582 33.85 0.223-1.300 24. SSS 24 0.0467 0.0159 34.05 0.019-0.142 30. OL 14 0221320002 8.52 0.117-0.153 31. OW 14 0.1302 0.0110 8.45 0.116-0.149 32. TRW 24 0.0076 0.0010 13.16 0.006-0.010 33. TLW 24 0.0080 0.0012 15.00 0.006-0.011 34. FWT 24 0.0444 0.0310 69.82 0.009-0.104 35. RWT 24 0.0411 0.0176 42.82 0.008-0.076 36. CL 24 0.2299 0.0137 5.96 | 0.203-0.267 37. CD 24 0.1540 0.0099 6.43 0.132-0.167 38. MAW 24 0.1396 0.0115 10.74 0.121-0.168 40. VD 24 0.0698 | 0.0170 24.36 0.039-0.099 41. RA 24 65.54 4.36 6.66 59-77 42. LA 24 23.14 2.80 12.09 19-27 43. TB 24 0.3654 0.0804 22.00 0.250-0.500 to 25 mm; lengths 15 to 40 mm. Branch robustness intermediate; width narrow to lower-end intermediate, moderately variable; branches straight to slightly sinuous, bending toward sites of dissepiment emplacement, frequently lateral branches broadly curving toward edge of zoarium. Branches closely spaced, distance between adjacent branch cen- ters extremely regular. Obverse surface texture gran- ular; surface rounded except for presence of single nar- row, well-developed keel; keel continuous, straight, extending along branch midline, causing slight positive inflection on obverse surface profile. Keel frequently becomes covered by lamellar skeleton during astogeny, obverse surface texture becomes increasingly granular. Single row of well-developed intermediate size nodes, ovate in shape, elongate proximodistally, size and shape moderately regular, projecting from middle of keel; one to three nodes per fenestrule length, two most com- mon, spacing intermediate, moderately uneven; node E MISSISSIPPIAN BRYOZOANS: SNYDER 39 diameter slightly to moderately increasing with asto- geny. Small stylets, moderately regular in size, variably emplaced along obverse branch surface, increasing in size during astogeny. Reverse surface texture granular, becoming more coarsely granular with astogeny; bear- inga moderate number of rows of intermediately spaced longitudinal striae which become overgrown during astogenetic thickening of lamellar skeleton. Numerous large microstylets positioned atop striae; microstylet Size, shape and positioning atop striae moderately ir- regular, with size and irregularity increasing during as- togeny. Large macrostylets present along reverse branch midline; shape circular or ovate, elongate proximo- distally, with size and shape moderately regular; one to two macrostylets per fenestrule length, with most common placement at branch-dissepiment contact; macrostylet spacing highly irregular, with size of ma- Crostylets greatly increasing during astogeny. Auto- Zooecia arranged in two rows, except third row only at Sites of branch bifurcation where middle autozooecium evidently shared by both branches; branch diameter thickens proximal and thins slightly distal to sites of branch bifurcation; otherwise diameters moderately Constant. Heterozooecia (ovicells?) occurring as inter- mediate size enlargements positioned between aper- tures; mean width and length of polymorphs approx- imately twice that of autozooecial apertures; connection between polymorph and autozooecial chamber prob- àble; polymorphs primarily situated toward proximal end of zoarium. Dissepiment width intermediate, slightly greater than half branch width, width constant; length intermediate, Constant; dissepiments connect branches at highly reg- ular intervals. Dissepiments thin medially, flare at dis- Sepiment-branch contact; highly recessed from ob- Verse, approximately even with reverse surface. Moderate astogenetic thickening of dissepiments. Ob- Verse dissepiment surface with one to three longitu- dinal striae across dissepiment perpendicular to direc- tion of branch length; reverse dissepiment surface with Numerous rows of longitudinal striae atop which occur Closely spaced rows of small microstylets; microstylet Number decreasing, size increasing during astogenetic thickening of dissepiments; both obverse and reverse dissepiment surfaces granular in texture. Emplacement Of dissepiments perpendicular or at small angle from Perpendicular to branch length. Apertures commonly Open on proximal or distal edge of dissepiments, rarely In middle of dissepiment edge at branch-dissepiment Contact; apertures arranged symmetrically or asym- Metrically between branches. Fenestrule size intermediate; shape most commonly elliptical to approaching rectangular, elongate proxi- Modistally; irregular in size, moderately irregular in Shape; expanding in length and width in obverse-re- verse direction. Mean width of fenestrule slightly less than mean branch width on obverse surface, slightly greater on reverse; fenestrule opening decreasing in size toward proximal end of zoarium due to astogenetic thickening of lamellar skeleton. Width to length ratio of fenestrule approximately 1:2; length much more constant than width. Two to four apertures per fenes- trule length, three most common; distance between closest aperture centers along branch, across branch, and across fenestrule all approximately equal, resulting in an evenly spaced grid of apertures across obverse zoarial surface. Autozooecial apertures small, circular, sometimes irregular in outline; size uniform, shape moderately variable, opening oriented parallel to plane of obverse surface. Thin, well-developed incomplete peristome, continuous around all but most proximal-adaxial edge of aperture, leaving a small to intermediate size peri- stomal gap. Aperture margin extends into fenestrule, causing pronounced inflections in fenestrule outline on obverse surface. Centrally thickened terminal dia- phragm commonly present toward proximal end of zoarium. Zoarial supports rare, when present develop as ex- tensions of reverse zoarial surface and lateral edge of zoarium. Interior description.—Branches circular to ovate in cross-section, elongate parallel to zoarial surface. Branches medium in thickness, variable. Autozooecial living chamber size intermediate, chambers biserially arranged in alternating rows along a planar branch axial wall; axial wall straight to slightly sinuous, extending toward and connecting with mod- erately long chamber lateral walls. Chambers elongate proximodistally, parallel to reverse wall. Autozooecial chamber outline irregularly ovate near reverse-wall budding-site; expanding rapidly, becoming a parallel- ogram, with distal edge of parallelogram near branch edge, throughout most of chamber; bilobate-ovate ap- pearance to chamber near obverse surface, longest di- rection of ovoid oriented distal-abaxially; chamber shape highly uniform. Aperture positioned at distal- abaxial end of chamber, connected to chamber by well- developed short vestibule of variable length. Ratio of chamber width to depth 9:10; depth to length ratio approximately 2:3; depth and length more constant than width. Superior hemiseptum moderately well-de- veloped, forms as extension of proximal vestibular ad- axial edge and front chamber wall; well-developed in- ferior hemiseptum positioned in mid chamber along reverse wall and extending across entire chamber per- pendicular to chamber length; hemisepta restrict chamber opening size between autozooecial chamber and inner vestibule edge; occasionally fusing of supe- rior and inferior hemisepta observed. Autozooecial 56 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 chamber diverges laterally from middle of branch at relatively constant angle (mean of 23°); from reverse wall at a highly constant angle (mean of 66°). Length and depth of enlarged polymorphs (ovicells?) approx- imately equal to those of standard autozooecial cham- bers; width slightly greater. Three-dimensionally reconstructed chamber form box-like with indentations in “box” caused by hemi- septal positioning; long dimension as viewed from ob- verse surface, approximately equidimensional in depth and width, as viewed from distal and lateral edges of branch, respectively. Internal granular skeletal layer moderately thick, ex- hibiting slight astogenetic thickening, continuous with obverse nodes, keel and peristome; reverse longitudi- nal striae and both macrostylets and microstylets; across dissepiments and in the middle of zoarial supports. Outer lamellar layer thickness intermediate to thin, with moderate astogenetic thickening. Remarks.—Laxifenestella maculasimilis is similar to other laxifenestellids in development of superior and inferior hemisepta and fusion of these hemisepta across the autozooecial chamber, as well as characteristic in- dented box-like shape of the chamber. It can be dis- tinguished from other laxifenestellids by presence of reverse macrostylets and smaller aperture size than all other laxifenestellids, along with significantly smaller autozooecial chambers than the other coarsely meshed laxifenestellids, L. fluctuata, n. sp. and L. coniuncti- styla, n. sp. Although present in suites of the Warsaw fauna col- lected by Ulrich, this species was placed with Archi- medes Hall, 1858 on the basis of close general exterior appearance. Examination of oriented peels shows dis- tinctive features such as presence of superior and in- ferior hemisepta present in L. maculasimilis, but ab- sent in Archimedes. Material studied. — Thirty-two exterior fragments, 14 sectioned specimens; largest zoarial fragment 16x21 mm (width to length). Preservation of the zoarial frag- ments excellent, as observed in the microstructural detail evident. Occurrence.— Laxifenestella maculasimilis is com- mon throughout the Warsaw study area; occurring in both calcarenites and shales. Holotype.— UI X-6811 (loc. 49B, sample 8). Paratypes.—UI X-6808-6810, 6812-6815, 6759, 6760 (loc. 49B, samples 8, 10, 11, 17), 6944, 6945, 6767 (loc. 47A, sample 32), 6732, 6733 (loc. 49B, sam- ples 12, 16). Laxifenestella serratula (Ulrich, 1890) Plate 9, figures 3-11, Plate 10, figures 1-8, Plate 11, figure 1; Table 15 Fenestella serratula Ulrich, 1890, p. 544, pl. 50, figs. 5-5c [Keokuk Group, Nauvoo, Illinois; Warsaw Beds, Monroe County and War- saw, Illinois; St. Louis Limestone, Caldwell, Lyon, and Crittenden counties, Kentucky; Chester Group, Sloan's Valley, Kentucky]; Keyes, 1894, p. 23 [Keokuk Limestone, Keokuk, Iowa]; Cumings, 1906, p. 1280, pl. 30, figs. 2-2c, 3-3a; Condra and Elias, 1944, pp. 72-76, pl. 13, figs. 6-8; pl. 21, figs. 4, 5; pl. 36, fig. 3; Elias and Condra, 1957, p. 409, pl. 45, fig. 2; pl. 46, figs. 7-9; pl. 48, fig. 1; Koenig, 1958, pp. 137-138, pl. 21, fig. 5; Trizna, 1958, p. 135, pl. 39, figs. 1—5; pl. 40, figs. 1-3; Burckle, 1960, pp. 1082- 1083, pl. 131, figs. 4, 6. Diagnosis.— Zoarium robustness intermediate, mesh close, pattern extremely regular; branches delicate, width narrow, thickness thin; branches most com- monly straight, lateral branches frequently broadly curved toward edge of zoarium; branches usually trans- versely ovate, rarely circular, closely spaced. Inter- mediate width, short dissepiments connect branches at highly regular intervals. Fenestrules small, shape elliptical to approximately rectangular, regular. Au- tozooecial aperture size lower-end intermediate, pre- dominantly ovate, elongate proximoabaxially, rarely circular, surrounded by well-developed incomplete peristome open only at proximal-adaxial edge; two to three (most commonly two) apertures per fenestrule. Single narrow keel along obverse branch midline, atop which are positioned intermediate size, ovate nodes. Autozooecial chamber size lower-end intermediate, chambers emplaced in two rows, except third row at sites of branch bifurcation; outline irregularly ovate to elliptical near reverse-wall budding-site; rapidly ex- panding, becoming irregularly pentagonal throughout mid chamber; bilobate-elliptical near obverse surface. Chambers elongate proximodistally, parallel to reverse wall. Apertures at distal-abaxial end of chamber, con- nected to chamber by short, variable-length vestibule. Superior and inferior hemisepta present, both well- developed, frequently hemisepta fuse in mid chamber, partitioning chamber and restricting chamber opening. Lateral-wall budding-angle moderately variable (mean of 22°); reverse-wall budding-angle highly constant (mean of 71?). Table 15 presents statistical criteria used in delim- iting this species. ; Exterior description.—Zoarium robustness inter- mediate; expansion flat to slightly obversely curved, fan-shaped; mesh close; moderate to slight astogenetic thickening of both obverse and reverse zoarial lamellar skeleton; zoarial mesh pattern extremely regular. Prob- able mature widths 15 to 20 mm, lengths 15 to 25 mm. Branches delicate; width narrow, relatively variable; most commonly straight, outer branches frequently broadly curved toward lateral edge of zoarium. Branches closely spaced, with distance between adja- cent branch centers highly regular. Obverse surface tex- ture granular; surface flat to slightly rounded, except MISSISSIPPIAN BRYOZOANS: SNYDER 57 Table 15.—Summary numerical analysis of Laxifenestella serratu- la (Ulrich, 1890). For explanation of abbreviations of characters (left column), see Table 8b (foldout inside back cover). number of mea- coeffi- sure- standard cient of observed ments: mean deviation variation range 1. WB 24 0.2744 0.0434 15.82 0.193-0.343 2. DBC 24 0.4420 0.0330 7.47 0.380-0.513 3. WD 24 0:1559 0.0328: 220,63 710111520. 260: 4. LF 24 0.3354 0.0398 11.87 0.257-0.415 5. WF 24 0.2008 0.0259 12.90 0.150-0.096 6. AF 24 219 0.44 19.66 2-3 TAL 24 0.0995 0.0029 2.91 0.093-0.104 8. AW 24 0.0844 0.0040 4.74 . 0.073-0.096 9. ADB 24 0.2354 0.0144 6.12 0.192-0.258 10. AAB 24 0.2418 0.0167 6.91 0.210-0.273 11. ABB 24 0.2493 0.0241 9.67 0.192-0.295 12. DN 24 0.0885 0.0174 19.66 0.057-0.123 14. SNB 24 0.1659 0.0601 36.23 0.098-0.307 15. WK 24 0.0223 0.0048 21.52 0.014-0.033 16. DSO 24 0.0052 0.0009 17.31 0.004-0.006 17. SSO 24 0.0267 0.0091 34.08 0.011-0.043 18. WP 24 0.0129 0.0024 18.60 0.008-0.016 22. RSS 24 0.0064 0.0011 17.19 0.005-0.009 24. SSS 24 0.0286 0.0083 29.02 0.023-0.040 32. TRW 24 0.0065 0.0007 10.77 0.005-0.008 33. TLW 24 0.0064 0.0007 10.94 0.005-0.008 34. FWT 24 0.0341 0.0244 71.56 0.005-0.093 35. RwT 24 0:0417 2002227 553.24 9) 081 36. CL 24 0.2185 0.0078 3.57 0.209-0.230 37. CD 24 0.1386 0.0056 4.04 0.131-0.148 38. MAW 24 0:1433 3 QI S9" TTT OLIOT 39. MIW 24 00989000144 *515:360130:07]0118 40. VD 24 0.0596 0.0190 31.88 0.035-0.088 41. RA DA FLOA 3.57 5.02 64-80 42. LA 24 22 1 226 10.19 19-27 43. TB 24 029292 20:05092 219.10, 027720512 Single, narrow, moderately well-developed keel; keel Continuous, straight to slightly anastomosing, extend- ing along branch midline and causing positive inflec- tion on obverse surface. Keel exhibiting pronounced thickening toward proximal end of zoarium due to astogenetic thickening of lamellar skeleton. Single row of alternately emplaced, well-developed, intermediate- Size nodes; shape ovate, proximodistally elongate, size and shape of nodes moderately regular, formed as pro- Jections from middle of keel; two to four nodes per fenestrule length, three most common; nodes closely, Moderately unevenly spaced; node diameter increasing With astogeny. Small stylets, moderately regularly sized, Variably emplaced along obverse branch surface, in- creasing in size and frequently fusing with astogeny. Reverse surface texture granular, coarsening with as- togeny; bearing a moderate number of rows of closely Spaced longitudinal striae atop which are positioned Closely spaced rows of small microstylets; stylet size Moderately regular, stylets increasing in diameter Slightly with astogeny, frequently overgrowing and ob- scuring longitudinal striae toward proximal end of zoarium. Autozooecia arranged in two rows, except third row only at sites of branch bifurcation where middle autozooecium evidently shared by both branches; branch diameter thickens proximal and thins moderately distal to sites of branch bifurcation; oth- erwise diameters highly constant. Heterozooecia not observed in any specimen examined. Dissepiments of intermediate width, slightly greater than half branch width, width moderately variable; length short, constant; connect branches at highly reg- ular intervals. Dissepiments moderately barlike, flare slightly at dissepiment-branch contact; slightly re- cessed from obverse, approximately even with reverse surface. Moderate astogenetic thickening of dissepi- ment. Obverse dissepiment surface with one to three longitudinal striae across dissepiment perpendicular to direction of branch length; reverse dissepiment surface with moderate number of rows of longitudinal striae atop which occur intermediately spaced rows of small stylets; striae becoming obscured during astogeny; both obverse and reverse dissepiment surface texture gran- ular. Emplacement of dissepiments perpendicular or nearly perpendicular to branch length. Apertures open on proximal edge, distal edge, or in middle of dissep- iment at dissepiment-branch contact; apertures ar- ranged symmetrically or asymmetrically between branches. Fenestrule size small; shape most commonly ellip- tical to approximately rectangular, elongate proxi- modistally; both size and shape regular; moderately expanding in width and length in obverse—reverse di- rection. Mean width of fenestrule approximately three- fourths that of branch on obverse surface, about equal on reverse; fenestrule opening decreasing in size toward proximal end of zoarium due to astogenetic thickening of lamellar skeleton. Width to length ratio of fenestrule approximately 2:3; width and length both moderately constant. Two to three apertures per fenestrule length, two most common; distance between closest aperture centers along branch, across branch, and across fenes- trule all approximately equal, resulting in an evenly spaced grid of apertures across obverse zoarial surface. Autozooecial aperture size lower-end intermediate, apertures predominantly ovate, elongate proximoab- axially, rarely circular; opening moderately large rel- ative to branch diameter, size and shape both highly consistent; oriented parallel to plane of obverse sur- face. Peristome thin, well-developed; incomplete, con- tinuous around all but most proximal-adaxial edge of aperture, leaving a small peristomal gap. Aperture margin extends into fenestrule, causing pronounced inflections in outline on obverse surface. Apertures commonly capped by centrally thickened terminal di- aphragms toward proximal end of zoarium. 58 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 Zoarial supports common, develop as extensions of reverse zoarial surface and lateral edge of zoarium. Interior description.— Branches most commonly ovate in cross-section, elongate parallel to zoarial sur- face, rarely circular in cross-section. Branches shallow, moderately regular in thickness. Autozooecial living chamber size lower-end inter- mediate, chambers biserially arranged in alternating rows along a planar branch axial wall; axial wall sin- uous, extending toward and connecting with proximal and distal chamber lateral walls. Chambers elongate parallel to reverse wall in proximodistal direction. Au- tozooecial outline irregularly ovate to elliptical near reverse-wall budding-site; expanding rapidly, becom- ing irregularly pentagonal throughout most of chamber depth; chamber bilobate-elliptical near obverse sur- face, with separation between proximal-adaxial and distal-abaxial ends of the chamber; shape of chamber highly uniform. Aperture positioned at distal-abaxial end of chamber, connected to chamber by well-devel- oped short vestibule of variable length. Ratio of cham- ber minimum width to maximum width approxi- mately 2:3; maximum width and depth approximately equal; depth to length ratio 5:8; depth and length more constant than width. Superior hemiseptum well-de- veloped, forms as extension of proximal vestibular in- terior edge and front chamber wall, extending across width of entire chamber; well-developed, curved in- ferior hemiseptum, emerging from junction of lateral and reverse wall, divides chamber in half transversely and longitudinally from proximal end of vestibule to middle of chamber reverse wall; frequent fusing of su- perior and inferior hemisepta to form a partial to nearly complete partition across chamber and between cham- ber and inner vestibule edge. Autozooecial chamber diverges laterally from middle of branch at a moder- ately variable angle (mean of 22°); from reverse wall at a highly constant angle (mean of 71°). Three-dimensionally reconstructed chamber form box-like with pronounced indentations in “box” caused by hemiseptal partitioning; longest dimension of “box” as viewed from obverse surface, approximately equi- dimensional in depth and width as viewed from distal and lateral edges of branch, respectively. Internal granular skeletal layer thickness interme- diate, continuous with obverse nodes, stylets, keel, and peristome; reverse longitudinal striae and microstylets; across dissepiments and in the middle of zoarial sup- ports. Outer lamellar thickness intermediate to thin, with moderate astogenetic thickening. Remarks.—Superior and inferior hemiseptal devel- opment, in conjunction with three-dimensional auto- zooecial chamber shape, readily place Laxifenestella serratula with the other laxifenestellids. L. serratula is, however, distinguished by closer mesh spacing, closely spaced, slightly alternating obverse nodal develop- ment, smaller chamber size, and smaller branch width than the other laxifenestellids. Close external similarity exists between L. serratula and R. tenax (Ulrich, 1888) in mesh spacing, branch dimensions, nodal size and placement, and aperture placement. However, comparison of interior charac- ters in these two species shows moderate to extreme differences in autozooecial chamber size and shape, and illustrates lack of inferior hemisepta with only presence of short superior hemiseptal development in R. tenax when compared to the well-developed su- perior and inferior hemisepta in L. serratula. Using the micrometric (meshwork) formula, one would prob- ably place L. serratula and R. tenax in the same species; when based on internal and external characters com- bined, they are placed under separate genera. Recognition of L. serratula in numerous localities covering a long time range probably reflects reliance on the meshwork formula or similar approaches. Material studied.—Thirty-five exterior fragments, 11 sectioned specimens; largest zoarial fragment 11x16 mm (width to length). The preservation of many zoar- ial fragments is excellent, although materials are fre- quently crushed, obscuring internal details. Occurrence.— Laxifenestella serratula is common throughout the Warsaw study area, occurring both in shaly and calcarenitic facies. Zoarial mesh varies slightly from north to south with slight coarsening of mesh in the south. However, size and shape of internal char- acters are constant and apparently not dependent on mesh variation. Syntypes.—USNM 44079, ISGS (ISM) 2745-2/4. Several specimens are illustrated in Ulrich (1890, pl. 50, figs. 5, 54, 5b, 5c). Figured and/or measured specimens.—Ul X-6741 (loc. 11, sample 61), 6837-6843 (loc. 49B, samples 12, 13), 6765 (loc. 47A, sample 32). Laxifenestella fluctuata, new species Plate 11, figures 2-11, Plate 12, figures 1-8, Plate 13, figure 1; Table 16 Etymology of name.— The name refers to the fluc- tuating or anastomosing nature of the branches that characterizes this species. Diagnosis.— Zoarium robustness intermediate, mesh intermediate, pattern highly variable; branches robust, lower-end wide in width, upper-end intermediate in thickness; branches ranging from straight to highly sin- uous toward sites of dissepiment emplacement, lateral branches frequently broadly curved toward edge of ` zoarium; branches transversely ovate, closely spaced. Branches joined at moderately irregular intervals by MISSISSIPPIAN BRYOZOANS: SNYDER 59 Table 16.—Summary numerical analysis of Laxifenestella fluc- tuata, n. sp. For explanation of abbreviations of characters (left column), see Table 8b (foldout inside back cover). number of mea- coeffi- sure- standard cientof observed ments mean deviation variation range 1. WB 24 0.3941 0.0800 20.30 0.263-0.567 2. DBC 24 0.6724 0.1302 19.36 0.363-0.973 3. WD 24 0.3780 0.1304 34.50 0.194-0.673 4. LF 24 0.60873: 0.1973- 2871.. 0.270=1.100 5. WF 24 0.3630 0.0842 23.20 0.240-0.531 6. AF 24 on!) 0.78 22.29 2-5 7. AL 24 0.0913 0.0107 11.72 0.075-0.117 8. AW 24 0.0740 0.0073 9.86 0.060-0.088 9. ADB 24 0.2617 0.0316 12.07 01177-01323 10. AAB 24 0.2945 0.0377 12.80 0.231-0.364 11. ABB 24 0.3986 0.0848 21.27 0.270-0.590 12. DN 24 0.1308 0.0380 29.05 0.078-0.219 14. SNB 24 0.6309 0.1966 31.16 0.187-1.020 15. WK 24 0.0461 0.0078 16.92 0.032-0.059 16. DSO 24 0.0086 0.0020 23.26 0.004-0.018 17. SSO 24 0.0196 0.0059 30.10 0.014-0.039 18. wp 24 0.0196 0.0039 19.90 0.016-0.034 30. OL 17 0.1821 0.0266 14.61 0.138-0.240 31. OW 17 0.1525- 0.0209- 13:70- 0:127-0:192 32. TRW 24 0.0078 0.0009 11.54 0.006-0.010 33. TLW 24 0.0143 0.0053 36.96 0.008-0.027 34. FWT 24 0.0636 0.0272 42.77 0.024-0.129 35. RWT 24 0.0894 0.0323 36.13 0.029-0.141 36. CL 24 0.2807 0.0165 5.88 0.260-0.314 37. CD 24 0.1466 0.0135 9.21 0.121-0:176 38. MAW 24 0.1622 0.0151 9.31 0.129-0.185 40. VD 24 0.0606 0.0134 22.11 0.040-0.082 41. RA DA ET ARTS 8.50 11.08 64-95 42. LA AS 3.59 13.08 18-34 43. TB 24 0.1979 0.0116 5.86 0.179-0.225 Intermediate-width, intermediate-length dissepi- Ments. Fenestrule size intermediate, shape ovate to elliptical, variable. Autozooecial aperture size lower- end intermediate, ovate; surrounded by thin, inter- Mediately developed complete peristome; two to five (three or four most common) apertures per fenestrule. Single upper-end narrow keel along middle of obverse branch, atop which are positioned large, ovate nodes. Autozooecial chamber size intermediate, chambers Most commonly emplaced in two rows, occasionally three rows for short to intermediate distances imme- diately proximal to sites of branch bifurcation; outline regularly elliptical to ovate near reverse-wall bud- ding-site; rapidly expanding, becoming an irregular Parallelogram to ellipse throughout mid chamber; bi- lobate-ovate near obverse surface. Chambers elongate Proximodistally, parallel to reverse wall. Apertures at distal-abaxial end of chamber, connected to chamber by intermediate and variable-length vestibule. Superior and inferior hemisepta present, well-deve- loped, frequently fuse causing restriction in chamber opening at proximal vestibular edge. Lateral-wall bud- ding-angle variable (mean of 27°); reverse-wall budding- angle moderately variable (mean of 77°). Heterozooe- cia (ovicells?) occurring as intermediate size enlarge- ments of some chambers. Table 16 presents statistical criteria used in delim- iting this species. Exterior description.—Zoarium robustness inter- mediate; forming a flat to slight obversely curved fan- shaped expansion; mesh spacing intermediate; distrib- uted across zoarial surface, most frequently positioned at or near site of branch-dissepiment contact. Dissepiments of intermediate width, slightly less than branch width, width highly variable; length interme- diate, moderately variable; connect branches at mod- erately irregular intervals. Dissepiments thin medially, flare at dissepiment-branch contact; moderately re- cessed from obverse, less so from reverse surface. Pro- nounced astogenetic thickening of dissepiments. Ob- verse and reverse dissepiment surfaces highly granular, granularity increasing with astogeny; otherwise dissep- iment surfaces lack ornamentaion. Emplacement of dissepiments approximately perpendicular to branch length. Apertures commonly open on proximal or dis- tal edge or in middle of dissepiment edge at branch- dissepiment contact; apertures arranged symmetrically or asymmetrically between branches. Fenestrule size intermediate; shape ovate to ellip- tical, elongate proximodistally; variable in both size and shape; width and length the same on both obverse and reverse surfaces. Mean width of fenestrule slightly less than mean branch width, slight decrease in size of fenestrule opening toward proximal end of zoarium due to astogenetic thickening of lamellar skeleton. Ra- tio of fenestrule width to length approximately 1:2; both width and length moderately variable. Two to five apertures per fenestrule length, three to four most common; distance between closest aperture centers along branch and across branch approximately equal; distance between closest aperture centers across fenes- trule 1.4 times greater. Autozooecial aperture size lower-end intermediate; apertures ovate, elongate proximodistally or proxi- moabaxially, frequently irregular in outline, shape variable; opening ranging from parallel to plane of ob- verse surface to attaining slight angle toward fenestrule. Thin, intermediately developed continuous peristomes surround apertures. Minor extension of aperture into fenestrule, causing very slight inflections in fenestrule outline on obverse surface. Centrally thickened ter- minal diaphragms present, most common toward end of zoarium, moderate astogenetic thickening of both obverse and reverse zoarial skeleton; zoarial pattern highly variable. Probable mature widths of 25 to 30 mm; lengths 35 to 45 mm. Branches robust; lower-end wide in width, variable; ranging from straight to highly sinuous, with pro- nounced inflections toward sites of dissepiment em- placement, frequently lateral branches broadly curved toward edge of zoarium. Branches closely spaced, dis- tance between adjacent branch centers moderately reg- ular. Obverse surface texture granular; surface round- ed, except for presence of single upper-end narrow, poorly developed keel; keel intermittent, moderately straight, extending along branch midline, causing mod- erate positive inflection on obverse surface. During astogeny lamellar skeleton frequently develops to cov- er keel and granularity of obverse surface texture in- creases. Single row of well-developed large nodes pres- ent, ovate in shape, proximodistally elongate, size and shape moderately variable, projecting from middle of keel; one to two nodes per fenestrule length, one most common, spacing intermediate, highly uneven; node diameter greatly increasing with astogeny. Small vari- able size stylets irregularly positioned across obverse surface. Reverse surface texture highly granular, coars- ening with astogeny; moderate number of rows of closely spaced longitudinal striae at most distal end of zoarium atop which occur rows of small, irregular size and shape microstylets. Both striae and microstylets covered by secondary lamellar skeleton at middle and proximal end of zoarium. Autozooecia most com- monly in two rows across branch, occasionally three rows for short to intermediate distances immediately proximal to sites of branch bifurcation; branch di- ameter thickens proximal, exhibits pronounced thin- ning distal to sites of branch bifurcation, branch di- ameters moderately variable. Heterozooecia (ovicells?) occurring as moderate enlargements of some apertures, shape ovate, mean diameter of polymorphs approxi- mately twice that of autozooecial apertures, polymorph width-to-length ratio approximately 4:5. Zoarial supports common, develop as extensions of reverse zoarial surface and lateral edge of zoarium. Interior description.—Branches ovate in cross-sec- tion, moderately elongate parallel to plane of zoarial surface. Branch thickness upper-end medium, mod- erately variable. Autozooecial living chamber size intermediate, chambers biserially arranged in alternating rows along a straight to slightly sinuous branch axial wall, ex- tending toward and connecting with moderately long chamber lateral walls. Chambers elongate proximo- distally, parallel to reverse wall. Autozooecial chamber outline irregularly elliptical to ovate near reverse-wall budding-sites; rapidly expanding, becoming an irreg- ular parallelogram to ellipse in mid and throughout most of chamber depth; bilobate-ovate appearance to chamber near obverse surface, with longest direction of ovoid oriented proximodistally or proximoabaxi- PALAEONTOGRAPHICA AMERICANA, NUMBER 57 ally; chamber shape moderately uniform. Aperture po- sitioned at distal-abaxial end of chamber, connected to chamber by extremely well-developed intermediate length vestibule of variable length. Ratio of chamber width to depth approximately 10:9; depth to length ratio approximately 1:2; chamber length more constant than width and depth. Well-developed superior hemi- septum forms as proximal extension of adaxial ves- tibular edge, extends across almost entire depth of chamber; well-developed short inferior hemiseptum extends across reverse-wall width two-thirds the way distally from chamber proximal edge; superior and in- ferior hemisepta frequently fuse, greatly restricting opening between autozooecial chamber and inner ves- tibular edge. Autozooecial chambers diverge laterally from middle of branch at variable angle (mean of 27°); from reverse wall at a moderately variable angle (mean of 77°). Length and depth of enlarged polymorphs (ovi- cells?) approximately equal to those of standard au- tozooecial chambers; width 1.2 times greater. Three-dimensionally reconstructed chamber form box-like, rounded, with pronounced indentations in “box” caused by hemiseptal partitioning; longest di- mension of “box” as viewed from obverse surface, approximately equidimensional in depth and width as viewed from distal and lateral edges of branch respec- tively. Internal granular skeleton thick, continuous with ob- verse nodes, keel, and peristome; reverse longitudinal striae; across dissepiments and in the middle of zoarial supports. Outer lamellar layer intermediate to thick, showing moderate astogenetic thickening. Remarks.—Laxifenestella fluctuata is differentiated from other laxifenestellids by the presence of three rows of autozooecia for distances proximal to sites of branch bifurcation, whereas other laxifenestellids only have the third row at site of bifurcation; by greater chamber width than depth, whereas all other laxife- nestellids observed have greater depth than width; by generally anastomosing nature of branches; and by greater width and depth of branches. Interior characters including autozooecial chamber shape and symmetry, and development of superior and inferior hemisepta in this species closely resemble those found in other laxifenestellids. Exterior differences be- tween species are often quite pronounced. Material studied.—Twenty-five exterior fragments, 14 sectioned specimens; largest zoarial fragment 16 x 18 mm (width to length). Excellent preservation is ob- served in almost all zoarial fragments collected. Occurrence.— Laxifenestella fluctuata is a relatively rare component of the Warsaw fauna at the Valmeyer and St. Louis localities, but occurs throughout the for- ` mation in both limestones and shales at these localities. Holotype.—UI X-6778 (loc. 49B, sample 12). MISSISSIPPIAN BRYOZOANS: SNYDER 61 Paratypes.—UI X-6724-6729, 6771-6777 (loc. 49B, Samples 8, 11, 12, 17). Genus MINILYA Crockford, 1944 Text-figure 10 Minilya Crockford, 1944, pp. 165-185, pl. 1, figs. 5, 7; text-figs. Ic, d. Rhombofenestella Termier and Termier, 1971, p. 39. Type species.— Minilya duplaris Crockford, 1944; [Lower Permian, Australia]. Typical Warsaw species. — Minilya sivonella, n. sp. [Osage-Meramec, Warsaw, Illinois]. Diagnosis. — Zoarium robustness intermediate to ro- bust, mesh spacing intermediate; triangular to irregu- larly pentagonal chamber outline in mid tangential sec- tion, chamber size intermediate; poorly to well- developed superior hemiseptum present, inferior hemiseptum absent, reverse-wall budding-angle high (means of 74? to 89°); alternating rows of large stylets along obverse surface formed as extensions of apertural Peristomal ring. Three-dimensionally reconstructed chamber form Cuneate. Description.—Zoarium robustness intermediate to Tobust, expansion flat to slightly obversely curved, mesh Spacing intermediate, regular to variable in uniformity. Branch width narrow to intermediate, straight to Sinuous in trace with lateral branches broadly curved toward edge of zoarium, branch surface rounded. Keel Present, single, narrow, width increases with astogeny and keel becomes covered. Nodes present or absent, emplacement monoserial, size intermediate, shape Ovate, located in middle of keel, closely spaced. Ob- Verse stylets present, size extremely small to inter- mediate, occurring across obverse surface. Microsty- lets present, size small to extremely small. Macrostylets Present in some species, large, typically occurring at branch-dissepiment junction. Autozooecia in two rows, third row at sites of branch bifurcation. Heterozooecia absent, Dissepiment width thin to intermediate, length short to intermediate, placement regular to variable. Fenestrule size intermediate, shape rectangular, el- liptical to ovate. Aperture size small to intermediate, shape circular, Oriented parallel to plane of obverse surface or at slight angle toward fenestrule; peristome present, incom- Dlete; two sizes of apertural stylets, small apertural Stylets filling peristomal gap and two large apertural Stylets developing from adaxial and abaxial apertural edge; terminal diaphragms present, primarily occur- "Ing toward proximal end of zoarium. Branch shape in cross-section ranging from circular to ovate. Branches thick in depth. Autozooecial chamber size intermediate, chambers monoserially emplaced, becoming biserially arranged along zigzagged axial wall; maximum chamber length extending proximodistally, parallel to reverse wall. Chamber outline triangular near reverse wall, trian- gular to rarely irregularly pentagonal in mid chamber, becoming irregularly elliptical near obverse surface. Vestibule present, length short to long. Superior hemi- septum present, poorly to well-developed at proximal vestibular edge, inferior hemiseptum absent. Lateral- wall budding-angle approximately 22? to 25° (means); reverse-wall budding-angle approximately 74? to 89? (means). Lamellar skeletal layer thick, exhibiting pro- nounced astogenetic thickening; granular skeletal layer thick, exhibiting slight astogenetic thickening. Three-dimensionally reconstructed chamber form cuneate. Text-figure 10 illustrates zoarial outlines in longi- tudinal, tangential, and transverse orientations and three-dimensional chamber reconstructions from dis- tal, abaxial branch edge, and obverse surface views. Remarks.— Acceptance of this genus has been slow in coming. Crockford (1944) introduced the genus, us- ing the following diagnosis: Fenestrellinae in which the branches show two rows of alternating Zooecia, one on each side of a slight median carina; nodes small, in two rows on the carina, placed so that one node is lateral to each zooecial aperture; zooecia sub-triangular; structure of the reverse surface as in Fenestrellina (Crockford, 1944, p. 172). Elias and Condra (1957, p. 66) considered Minilya to be of subgeneric status because they doubted the taxonomic significance of biserial nodes adjacent to autozooecial apertures and the consistency of trian- gular zooecial chamber shapes; the main criteria used by Crockford in distinguishing the genus. Nekhoroshev (1960) placed Minilya in synonymy with Fenestella Lonsdale, 1839, for the same reasons as those of Elias and Condra. Both monoserial and biserial arrangement of nodes were found by Wass (1966) on the same zoaria and were considered nonspecific based on general mesh- work similarities. Wass also placed Minilya in syn- onymy with Fenestella. Morozova (1974), relying on tangential chamber outline, fenestrule shape, dissepi- ment size and shape, nodal number and placement, recognized Minilya and assigned 20 species to the ge- nus. Biserial nature of nodal placement can be achieved in several ways: as nodal extensions, nodes positioned across obverse surface without keel, large stylets that develop as extensions of peristome with one adaxially and one abaxially positioned stylet per aperture, biseri- al nature of aperture placement resulting in biserial nature of stylet placement. The latter characterizes Minilya as found in the Warsaw, and appears to be consistent with Minilya as described and illustrated by Crockford. Such stylet positioning associated with ap- 62 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 Table 17.—Summary numerical analysis of Minilya sivonella, n. sp. For explanation of abbreviations of characters (left column), see Table 8b (foldout inside back cover). number of mea- - sure- standard cient of observed ments mean deviation variation range 1. WB 24 0.3773 0.1034 27.41 0.225-0.600 2. DBC 24 0/7054: 01215 17.222 0:50070:675 3. WD 24 0.1745 0.0485 27.79 0.113-0.275 4. LF 24 0.8662 0.1765 20.38 0.500-1.125 5. WF 24 0.3336 0.0585 17.54 0.250-0.438 6. AF 24 3.50 0.78 MEER) 2-5 7. AL 24 0.1056 0.0107 10.13 0.080-0.120 9. ADB 24 0.3936 0.0366 9.30 | 0.350-0.500 10. AAB 24 0:3793 -0.0319 8.41 0.320-0.440 11. ABB 24 0.3914 0.0517 12.20 0.344-0.550 12. DN 24 0.1139 0.0173 -15.19 . 0.075-0.160 14. SNB 24 0.2393 0.0428 17.89 0.128-0.300 15. WK 24 0.0408 0.0080 19.61 0.030-0.055 16. DSO 24 0.0102 0.0039 38.24 0.004-0.020 17. SSO 24 0.0592 0.0211 35.64 0.030-0.100 18. WP 24 0.0222 0.0051 22.97 0.012-0.032 19. SA 24 10.42 0.67 7.42 10-12 20. SAD 24 0.0094 0.0044 46.32 0.003-0.023 21. RSL 24 0.1292 0.0498 38.54 0.050-0.250 22. RSS 24 0.0097 0.0027 28.72 0.007-0.015 23. SSL 24 0.8500 0.3754 44.16 ..0:675—1.330 24. SSS 24 0.0333 0.0123 36.94 0.020-0.063 32. TRW 24 0.0158 0.0045 28.48 0.010-0.025 33. TLW 24 0.0150 0.0045 30.00 0.010-0.025 34. FWT 24 0.1215 0.0340 27.98 0.053-0.167 35. RWT 24 0.1219 0.0386 31.67 0.056-0.180 36. CL 24 0.3693 0.0194 5.25 0.343-0.405 37. CD 24 0.1580 0.0175 11.08 0.125-0.180 38. MAW 24 0.1394 0.0130 9.33 0.120-0.175 40. VD 24 0.1628 0.0190 11.67 0.133-0.200 41. RA 24 88.50 4.49 5:07 80-93 42. LA 24 21.49 4.73 21.75 14-32 43. TB 24 0.5133 0.0858 16.72 0.363-0.650 ertural development suggests greater phylogenetic sig- nificance than nodes associated with keel or obverse surface development. Stylet development in conjunc- tion with chamber shape, superior hemisepta, high re- verse-wall budding-angle, and monoserial chamber emplacement endorse retention of Minilya as a valid genus. à Species composition.— The type species, Minilya du- plaris Crockford, 1944, and two additional species are herein assigned to this genus: M. sivonella, n. sp., and M. paratriserialis, n. sp. Morozova (1974) assigned 20 additional species. Range.—Lower Mississippian to Lower Permian; species included by other workers have a greater range. Minilya sivonella, new species Plate 13, figures 2-12, Plate 14, figures 1—5; Text-figure 10; Table 17 Etymology of name.— Named for Paul Sivon, whose input into concepts of taxonomy and research while I was preparing the manuscript was appreciated. Diagnosis.—Zoarium robust, mesh spacing lower- end intermediate, pattern moderately irregular; branches robust, width upper-end intermediate, thick in depth, predominantly sinuous to rarely straight, transversely circular to ovate, branch spacing moder- ately close; joined at moderately irregular intervals by thin, short to intermediate length dissepiments. Fe- nestrule size upper-end intermediate; shape elliptical to rarely ovate, moderately irregular. Autozooecial ap- erture size lower-end intermediate, shape circular, sur- rounded by thin, well-developed incomplete peristome open at proximal or distal edge of aperture, nine to 14 small stylets fill opening; two to five (most commonly three or four) apertures per fenestrule. Single narrow keel along middle of obverse branch. Biserially ar- ranged large stylets along obverse surface; stylets form as extensions of either proximal or distal-adaxial peri- stomal edge. Autozooecial chamber size intermediate, monoserially emplaced, rapidly becoming two rows toward obverse surface throughout zoarium, except third row at sites of branch bifurcation; outline round- ed triangle near reverse-wall budding-site and through- out most of chamber; becoming irregularly elliptical near obverse surface. Chambers elongate proximodis- tally, parallel to reverse wall. Aperture at distal-abaxial end of chamber, connected to chamber by long ves- tibule of moderately constant length. Superior hemi- septum well-developed, short to intermediate in length; inferior hemiseptum absent. Lateral-wall budding-an- gle highly variable (mean of approximately 22”); re- verse-wall budding-angle highly constant (mean of ap- proximately 89°). Table 17 presents statistical criteria used in delim- iting this species. Exterior description.—Zoarium robust, expansion flat or slightly curved in obverse direction, less fre- quently curved in reverse direction or undulating, fan- Text-figure 10.—Minilya sivonella illustrated. 1, diagrammatic longitudinal section illustrating changing chamber outline from deep section near middle of branch (bottom of figure) to shallow section near abaxial edge of branch (top of figure) [Superior hemiseptum (arrow) is shown in this illustration.], x 70; 2, diagrammatic tan- gential section showing changing chamber outline from deep section near reverse-wall budding-site (bottom of figure) to shallow section near obverse surface (top of figure) [Observe large apertural stylet at proximoadaxial edge of aperture (arrow).], x10; 3, diagrammatic transverse section across branch, x70; 4, diagrammatic transverse section across branch illustrating typical orientation of apertures (arrow) relative to plane of obverse surface, x 70; 5, reconstruction of chamber shape (three-dimensional) as viewed from distal end of branch, chamber reconstructed from right side of branch, x 140; 6, reconstruction of chamber shape (three-dimensional) as viewed from _ abaxial edge of branch [Observe inflection in chamber outline caused by superior hemiseptum (arrow).], x 140; 7, reconstruction of cham- ber shape (three-dimensional) as viewed from obverse surface, X 140. MISSISSIPPIAN BRYOZOANS: SNYDER 63 shaped; mesh lower-end intermediate; pronounced as- togenetic thickening of both obverse and reverse zoar- ial lamellar skeleton; zoarial pattern moderately irreg- ular. Probable mature widths 20 to 35 mm; lengths 30 to 45 mm. Branches robust; width upper-end intermediate, variable; most commonly sinuous, extending toward sites of dissepiment insertion, rarely straight, lateral branches exhibiting large-scale curvature toward edge of zoarium. Branch spacing moderately close, distance between adjacent branch centers regular. Obverse sur- face smooth to slightly granular in texture; surface 64 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 rounded except for single, narrow, well-developed keel; keel continuous, straight or anastomosing, extending along branch midline and causing very slight inflection on obverse surface. With astogeny, keel becomes cov- ered by lamellar skeleton and obverse surface texture becomes increasingly granular. A single large stylet de- velops on either proximal or distal adaxial edge of each autozooecial aperture, forms as extension of the peri- stome, resulting in biserial emplacement pattern. Sty- lets well-developed, size intermediate; shape circular to ovate, elongate proximodistally, less frequently stel- late; size moderately regular, shape variable; two to five stylets per fenestrule length, three or four most common, spacing very even. With astogeny, stylets migrate toward middle of branch and away from ap- ertural edge, forming alternating row of large stylets along obverse branch surface; these stylets are not po- sitioned atop keel and thus cannot be considered nodes by definition; stylet diameter increasing with astogeny as well. Lower-end intermediate, variable-size stylets irregularly positioned across obverse surface. Reverse surface texture smooth to slightly granular, becoming more coarsely granular with astogeny; bearing numer- ous rows of closely spaced longitudinal striae atop which are positioned rows of extremely small, irregular size and shape microstylets; both striae and stylets covered by lamellar skeleton during astogenetic thickening. Large circular macrostylets, variable in size and shape, positioned in middle of reverse branch; most com- monly occurring at or near branch-dissepiment con- tact; moderately irregularly spaced, increasing in size during astogeny. Autozooecia arranged in two rows, except third row at sites of branch bifurcation where middle autozooecium evidently shared by both branches; slight thickening of branches proximal, thin- ning distal to sites of branch bifurcation. Heterozooe- cia absent in zoarial fragments examined. Dissepiments of thin width, less than half width of branch, width variable; dissepiments short to inter- mediate in length, connect branches at moderately ir- regular intervals. Dissepiments exhibit pronounced medial thinning, moderately flared at branch-dissep- iment contact; highly recessed from obverse, moder- ately so from reverse surface. Moderate astogenetic thickening of dissepiment. Ornamentation lacking on both obverse and reverse dissepiment surfaces; both obverse and reverse surfaces moderately granular in texture. Dissepiments emplaced perpendicular to or at a slight angle from perpendicular to branch length. Apertures commonly open on proximal or distal edge, or in middle of dissepiment edge at branch-dissepi- ment contact; arranged symmetrically or asymmetri- cally between branches. Fenestrule size upper-end intermediate; shape pre- dominantly elliptical to more rarely ovate, elongate proximodistally; moderately irregular in shape; ex- panding slightly in width and length in obverse-reverse direction. Mean width of fenestrule slightly less than branch on obverse surface, approximately equal on reverse; fenestrule opening decreasing in size toward proximal end of zoarium due to astogenetic thickening of lamellar skeleton. Width to length ratio of fenestrule ranging from 1:2 to slightly greater than 1:4, variable, with ratio of 1:3 most common; width slightly more constant than length. Two to five apertures per fenes- trule length, three to four most common; distance be- tween closest aperture centers along branch and across branch approximately equal, slightly less than that of closest aperture centers between branches. Autozooecial aperture size lower-end intermediate, shape circular, moderately variable in size, constant in shape; opening oriented parallel to plane of obverse surface, more rarely attaining a slight angle toward fenestrule; thin, well-developed peristome present; peristome incomplete, formed at either proximal or distal edge of aperture; peristomal gap filled by nine to 14 small, evenly positioned stylets which form a semicircle. Aperture margins extend into fenestrule, causing moderate to pronounced inflections in fenes- trule outline on obverse surface. Terminal diaphragms commonly present, most frequently occurring toward proximal end of zoarium. Zoarial supports present, well-developed, occurring as extensions of reverse zoarial surfaces and lateral edge of zoarium. Interior description.—Branches circular to slightly ovate in transverse section, elongate in obverse-re- verse direction. Branches thick, moderately variable in depth. Autozooecial living chamber size intermediate, monoserial emplacement at or near reverse-wall bud- ding-site, becoming biserially arranged toward obverse surface along planar branch axial wall; axial wall form- ing zigzag pattern, extending diagonally across entire branch and forming chamber lateral walls. Chamber longest dimension paralleling reverse wall in proxi- modistal direction. Autozooecial chamber outline tri- angular with rounded corners near reverse-wall bud- ding-site and throughout most of chamber; becoming irregularly elliptical near obverse surface, ellipse elon- gate in proximal-abaxial direction and slightly enlarged at distal end of chamber. Aperture positioned at distal- abaxial end of chamber, connected to chamber by rel- atively long vestibule of moderately constant length. Ratio of chamber width to depth approximately 8:9; depth to length ratio approximately 2:5; length much more constant than width and depth. Well-developed superior hemiseptum, short to intermediate in length, extending distally from proximal inner edge of vesti- bule and forming partial restriction between vestibule MISSISSIPPIAN BRYOZOANS: SNYDER 65 and autozooecial chamber; inferior hemiseptum ab- sent. Autozooecial chamber diverges laterally from middle of branch at a highly variable angle (mean of approximately 22°); from reverse wall at a highly con- Stant angle (mean of approximately 89°). Three-dimensionally reconstructed chamber form cuneate with acute angles oriented proximally and dis- tally, and obtuse angle toward branch midline; mod- erate indentation in chamber form caused by superior hemiseptum; longest dimension as viewed from ob- verse surface; smaller, approximately equidimensional in depth and width as viewed from distal and lateral €dges of branch respectively. Inner granular skeletal material thick, continuous with obverse large stylets, small stylets, peristome, ap- ertural stylets, and keel; reverse longitudinal striae and both large and small stylets; across dissepiments and in the middle of zoarial supports. Outer lamellar layer thick, with pronounced astogenetic thickening on both Obverse and reverse zoarial surfaces; thickest toward Proximal end of zoarium. Remarks.—M. sivonella is differentiated from M. Paratriserialis, n. sp., the only other species of Minilya Crockford, 1944 in the Warsaw, by a substantially larg- er autozooecial chamber, better developed superior hemiseptum, much coarser meshwork, and substan- tially thicker branches. Similarities in autozooecial Chamber shape and inflection in chambers caused by Superior hemiseptum suggest close phylogenetic affın- 1ty between the two species, as does the large stylet developed at the peristomal edge. M. sivonella appears similar to an unnamed species Contained in a faunal suite collected by Ulrich from Kings Mountain, Kentucky and stored in collections at the U. S. National Museum of Natural History. The restriction of occurrence of this species to the southern half of the study area (an area not extensively dealt With by Ulrich, who concentrated on the northern por- tion of the area included in this study), could account for Ulrich’s not describing this species in his extensive Works. Another reason could be that he did not deal In great detail with much of the material collected from Kings Mountain. Material studied. — Forty-four exterior fragments; 12 Sectioned specimens; largest zoarial fragment 21 x 30 mm (width to length). There is little skeletal alteration ?r crushing in the zoaria collected. Occurrence.— Minilya sivonella is common at the Valmeyer and St. Louis localities, although it occurs Primarily in the Lower Warsaw. It is also infrequently Ound in the Upper Warsaw. It is present in both cal- Càrenites and shales. Holotype. —UI X-6905 (loc. 49B, sample 12). Paratypes.—UI X-6904, 6906, 6876-6879, 6951- 6955 (loc. 49B, samples 8, 10, 15, 16). Minilya paratriserialis, new species Plate 14, figures 6-10, Plate 15, figures 1-9; Table 18 Etymology of name.—Named for its similarity in appearance to F. triserialis Ulrich, 1890. Diagnosis.—Zoarium robustness intermediate, mesh spacing intermediate, pattern extremely regular; branches moderately robust, narrow in width, thick in depth; branches straight to slightly curved, transversely irregularly ovate or circular, closely spaced; connected at highly regular intervals by intermediate width and length dissepiments. Fenestrule size lower-end inter- mediate; shape approaching rectangular to less com- ` monly elliptical, highly regular. Autozooecial aperture size small, shape circular, surrounded by well-devel- oped incomplete peristome from or near to which two intermediate-size apertural stylets, one abaxial and the other adaxial, originate and form an alternating biserial arrangement across the keel; two to four (most com- monly three) apertures per fenestrule. Single upper-end narrow width keel along middle of obverse branch, atop which are positioned intermediate-size ovate nodes. Autozooecial chamber size lower-end inter- mediate, monoserially emplaced, rapidly becoming two rows toward obverse surface and throughout zoarium, except third row at sites of branch bifurcation; outline rounded triangle near reverse-wall budding-site; usu- ally remaining triangular throughout mid chamber, more rarely becoming irregularly pentagonal; becom- ing irregularly elliptical near obverse surface. Cham- bers elongate proximodistally, parallel to reverse wall. Aperture at distal-abaxial end of chamber, connected to chamber by short vestibule of moderately variable length. Superior hemiseptum poorly developed, short; inferior hemiseptum absent. Lateral-wall budding-an- gle variable (mean of approximately 25°); reverse-wall budding-angle highly constant (mean of approximately 74°). Table 18 presents statistical criteria used in delim- iting this species. Exterior description.—Zoarium robustness inter- mediate; expansion flat to slightly obversely curved, fan-shaped; mesh spacing intermediate; pronounced astogenetic thickening of both obverse and reverse la- mellar skeleton; zoarial pattern extremely regular. Probable mature widths 15 to 20 mm; lengths 20 to 30 mm. Branches moderately robust; narrow in width, mod- erately variable; most commonly straight, some lateral branches slightly curved toward edge of zoarium. Branches closely spaced, distance between adjacent branch centers extremely regular. Obverse surface texture granular; surface rounded except for single up- per-end narrow width well-developed keel; keel con- tinuous, predominantly straight to more rarely anas- 66 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 tomosing, positioned along branch midline and causing positive inflection along obverse surface. With asto- geny, keel exhibits pronounced astogenetic thickening, primarily toward proximal end of zoarium. Single row of well-developed intermediate-size nodes, shape ovate, elongate proximodistally; size and shape of node mod- erately variable; projecting from middle of keel; one to three nodes per fenestrule length, two most com- mon; node spacing even, intermediate; node diameter greatly increasing with astogeny. Extremely small, reg- ular-size, variably positioned stylets emplaced across obverse branch surface. Two intermediate-size aper- tural stylets form as extensions of the apertural peri- stome; one at the mid-distal adaxial edge, positioned abaxial to keel and forming an alternating biserial ar- rangment across the keel; the other at the mid-distal abaxial edge, extending into the fenestrule opening; during astogeny these stylets migrate away from sites of origin along peristomal edge, the first toward the branch edge and the second into the fenestrule opening. Reverse surface texture granular, coarsening with as- togeny; bearing numerous rows of closely spaced lon- gitudinal striae atop which are positioned small mi- crostylets variable in both size and shape; both striae and microstylets frequently become covered during as- togenetic thickening of lamellar skeleton. Autozooecia arranged in two rows, except third row at sites of branch bifurcation where middle autozooecium evidently shared by both branches; branches exhibit slight thick- ening proximal, slight thinning distal to sites of branch bifurcation. Heterozooecia absent in zoarial fragments examined. Dissepiments of intermediate width, two-thirds width of branch, width relatively constant; length in- termediate, relatively constant; connect branches at highly regular intervals. Dissepiments exhibit slight medial thinning, moderately barlike in appearance; highly recessed from obverse, less so from reverse sur- face. Pronounced astogenetic thickening of dissepi- ments. Obverse dissepiment surface with one to three longitudinal striae across dissepiment perpendicular to branch length; both obverse and reverse dissepiment surfaces containing rows of small stylets and granular in texture. Emplacement of dissepiments either per- pendicular or at an angle of 10° to 15° from perpen- dicular to branch length. Apertures commonly open on proximal or distal edge or in middle of dissepiment at branch-dissepiment contact; arranged symmetri- cally or asymmetrically between branches. Fenestrule size lower-end intermediate; shape ap- proaching rectangular to less commonly elliptical, elongate proximodistally; highly regular in size and shape; expanding slightly in width and length in ob- verse-reverse direction. Mean width of fenestrule slightly less than branch width on obverse surface, ap- Table 18.—Summary numerical analysis of Minilya paratriseri- alis, n. sp. For explanation of abbreviations of characters (left col- umn), see Table 8b (foldout inside back cover). number of mea- coeffi- sure- standard cient of observed ments mean deviation variation range 1. WB 24 0.2567 0.0427 16.63 0.184-0.356 2. DBC 24 0.4766 0.0560 11.75 0.359-0.581 3. WD 24 0.1654 0.0305 18.44 0.114-0.248 4. LF 24 0.4783 0.0715 14.95 0.311-0.587 5. WF 24 0.2708 0.0512 18.91 0.156-0.362 6. AF 24 3.00 0.42 13.90 2-4 7. AL 24 0:07.12°20.0035 4.92 0.064-0.079 9. ADB 24 02272" 700136 5.99 0.207-0.257 10. AAB 24 0.3115 0.0439 14.09 0.236-0.401 11. ABB 24 0.3212 0.0450 15.15 0.231-0.422 12. DN 24 0.1088 0.0284 26.10 0.064-0.159 14. SNB 24 0.3527 0.0472 13.38 0.269-0.467 15. WK 24 0.0480 0.0102 21.25 0.032-0.065 16. DSO 24 0.0033 0.0053 16.31 0.002-0.005 17. SSO 24 02105 00139 6.60 0.188-0.234 18. WP 24 0.0165 0.0033 20.00 0.014-0.022 19. SA 24 2.00 0.00 0.00 2 20. SAD 24 0.0262 0.0064 24.43 0.019-0.044 22. RSS 24 0.0172 0.0041 23.84 0.010-0.024 24. SSS 24 0.1077 0.0272 25.26 0.073-0.156 32. TRW 24 0.0114 0.0035 30.70 0.006-0.018 33. TLW 24 0.0175 0.0040 22.86 0.010-0.026 34. FWT 24 0.0405 0.0165 40.74 0.016-0.071 35. RWT 24 0.0942 0.0422 44.80 0.028-0.186 36. CL 24 0.2104 0.0107 5.09 0.194-0.229 37. CD 24 0.1516 0.0076 5.01 0.139-0.167 38. MAW 24 0.1269 0.1084 6.62 0.115-0.148 39. MIW 24 0.0618 0.0084 13.59 0.049-0.078 40. VD 24 0.0766 0.0107 13.97 0.065-0.103 41. RA 24 73.67 5.44 7.39 62-82 42. LA 24 24.67 3.45 13.97 20-32 43. TB 24 0.3951 0.0451 11.41 0.292-0.483 proximately equal on reverse; fenestrule opening de- creasing in size toward proximal end of zoarium due to astogenetic thickening of lamellar skeleton. Width to length ratio of fenestrule approximately 1:2, length more constant than width. Two to four apertures per fenestrule length, three most common; distance be- tween closest aperture centers along branch approxi- mately three-fourths of spacing either across branch or across fenestrule, which are approximately equal; spac- ing along branch much more constant than spacing across branch or across fenestrule. Autozooecial apertures small, shape circular, uni- form; opening oriented parallel to plane of obverse surface or at slight angle toward fenestrule; thin, well- developed peristome present, incomplete with peristo- mal gap at proximal edge, peristome site from which two previously described intermediate size stylets orig- inate. Aperture margin extends into fenestrule, causing ' pronounced inflections in fenestrule outline on obverse surface. Centrally thickened terminal diaphragms pres- MISSISSIPPIAN BRYOZOANS: SNYDER 67 €nt, moderately uncommon; occurring predominantly at proximal end of zoarium. Zoarial supports extremely well-developed, form as €xtensions of reverse zoarial surfaces and lateral edge of zoarium. Interior description.—Branches irregularly ovate, elongate in obverse-reverse direction, to approxi- Mately circular in transverse section, slightly expanded on obverse side. Branches thick, regular in depth. Autozooecial living chamber size lower-end inter- Mediate, chambers monoserially emplaced at or near Teverse-wall budding-site, becoming biserially ar- Tanged toward obverse surface along planar branch axial wall; axial wall forming zigzag pattern, extending diagonally across entire branch and forming chamber lateral walls. Chamber maximum dimension extending Proximodistally, parallel to chamber reverse wall. Au- tozooecial chamber outline triangular with rounded Corners near reverse-wall budding-site; remaining pri- Marily triangular, less frequently irregularly pentago- nal, throughout mid chamber; becoming irregularly elliptical near obverse surface, ellipse elongate in prox- imal-abaxial direction and slightly enlarged at distal end of chamber. Aperture positioned at distal-abaxial end of chamber, connected to chamber by short ves- tibule of moderately variable length. Ratio of chamber Minimum to maximum width approximately 1:2; Maximum width to depth ratio 5:6; depth to length Tatio approximately 7:10; chamber length, depth, and Maximum width much more constant than minimum width. Superior hemiseptum poorly developed, posi- tioned at inner proximal vestibular edge; inferior hemi- Septum absent. Autozooecial chamber diverges later- ally from middle of branch at a variable angle (mean Of 25°); from reverse wall at a highly constant angle (mean of 74°). Three-dimensionally reconstructed chamber form Cuneate with acute angles oriented proximally and dis- tally and obtuse angle toward branch midline; slight Indentation in chamber form caused by superior hemi- Septum; longest dimension as viewed from obverse Surface, depth smaller than length as viewed from dis- tal end of branch; width smallest, viewed from lateral edge of branch. Inner granular skeletal layer thick, continuous with Obverse nodes, small stylets, peristome, apertural sty- lets, and keel; reverse longitudinal striae and stylets; across dissepiments and in the middle of zoarial sup- Ports. Outer lamellar layer extremely thick on reverse, thinner on obverse side of branch, with pronounced astogenetic thickening evident on both surfaces; thick- est toward proximal end of zoarium. Remarks.— M. paratriserialis is readily distin- 8uished from M. sivonella, n. sp. by its finer mesh, Smaller autozooecial chamber, nodal development atop keel, reduced hemiseptal development, and smaller ap- erture opening. Close phylogenetic relationships ap- pear to exist between them based on similar cuneate three-dimensional chamber shape, presence of supe- rior hemisepta, and relatively large apertural stylet de- velopment at the peristomal edge. M. paratriserialis is similar in appearance to Fen- estella triserialis Ulrich, 1890 which occurs in the Low- er Keokuk Limestone near Keokuk, Iowa. Biserially arranged stylets are positioned across a central keel in both species; however M. paratriserialis is distin- guished from F. triserialis by a finer mesh, smaller , autozooecial chambers, thinner branches, less distinct rows of stylets, and more pronounced nodes. Material studied.— Thirty-eight exterior fragments; six sectioned specimens; largest zoarial fragment 14 x 22 mm (width to length). Intermediate robustness of the zoarium normally results in excellent preservation of this species. Occurrence.— Minilya paratriserialis is common throughout the Warsaw study area. It occurs in both calcarenites and shales, but is more common in the latter. Holotype. —UI X-6871 (loc. 10, sample 35). Paratypes.— UI X-7023 (loc. 49B, sample 12), 7024, 6948, 6947, 6950 (loc. 10, samples 28, 35, 42). Genus EXFENESTELLA Morozova, 1974 Text-figure 11 Type species. — Fenestella erkovae (Shulga-Nester- enko, 1951); [Lower Carboniferous, Namurian Stage; Russian Platform]: Morozova, 1974, p. 174, pl. 3-3. Typical Warsaw species.— Exfenestella exigua (Ul- rich, 1890) [Warsaw Beds, Monroe County, Illinois]. Diagnosis.—Zoarium robust, mesh spacing inter- mediate; chamber outline an assymetrical rectangle to parallelogram in mid tangential section, chamber size intermediate, aperture size small; well-developed su- perior hemiseptum present on proximal vestibular edge, well-developed inferior hemiseptum present on prox- imal side of distal lateral chamber wall approximately halfway up wall, extending across entire width of chamber and half chamber depth; chamber reverse- wall budding-angle approximately 71? (mean). Three-dimensionally reconstructed chamber form a rectangular box exhibiting inflections in mid chamber due to hemiseptal emplacement. Description. — Zoarium robust, expansion obversely curved, mesh spacing intermediate, extremely regular. Branch width narrow to intermediate, straight to sinuous in trace with lateral branches broadly curved toward edge of zoarium; branch surface rounded. Keel present, single, width intermediate, increasing with as- togeny and in many covered by lamellar skeleton. Nodes present, emplacement monoserial, size intermediate, 68 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 shape circular to ovate, located atop keel, closely spaced. Obverse stylets present, small, occurring across ob- verse branch surface. Microstylets present, extremely small in size. Macrostylets present, large, typically lo- cated at site of branch-dissepiment junction. Auto- zooecia in two rows, third row at sites of branch bi- furcation. Heterozooecia not observed. Dissepiments of intermediate width, length inter- mediate, connect branches at highly regular intervals. Fenestrule size intermediate, shape regularly to ir- regularly elliptical, less frequently rectangular to ovate. Aperture size small, shape circular to rarely ovate, oriented parallel to plane of obverse surface or at slight angle toward fenestrule. Peristome present, complete; apertural stylets present, developed as extensions of peristomal edge; terminal diaphragms present, occur- ring toward proximal edge and in middle of zoarium. Branches circular to ovate in cross-section; medium in thickness. Autozooecial chamber size intermediate, chambers biserially emplaced along sinuous axial wall; maxi- mum chamber length parallel to proximal and distal lateral chamber walls. Chamber outline an asymmet- rical diamond near reverse wall, becoming an asym- metrical parallelogram to rectangle in mid chamber and throughout most of chamber depth, bilobate-el- liptical near obverse surface. Vestibule present, length intermediate. Superior hemiseptum present, posi- tioned at proximal vestibular edge, inferior hemisep- tum present, well-developed at proximal side of distal lateral chamber wall. Lateral-wall budding-angle ap- proximately 25° (mean); reverse-wall budding-angle approximately 71°(mean). Lamellar skeletal layer thick, exhibiting moderate astogenetic thickening; granular skeletal layer thin, exhibiting no astogenetic thicken- ing. Three-dimensionally reconstructed chamber form a rectangular box exhibiting inflections in middle of box length due to hemiseptal emplacement. Text-figure 11 illustrates zoarial outlines in longi- tudinal, tangential, and transverse orientations and three-dimensional chamber reconstructions from dis- tal, abaxial branch edge and obverse surface views. Remarks.—Morozova (1974, p. 174) based the ge- nus Exfenestella on “hemisepta located on branches in two rows", a fabiform (irregular parallelogram- shaped) chamber shape, carina size, and rows of nodes. Hemiseptal positions are unclear from Morozova’s il- lustrations; however, general chamber shape allows as- signment of Fenestella exigua Ulrich, 1890 to her ge- nus, assuming proximal inflections in chamber lateral walls represent locations of inferior septal emplace- ment, thus forming the two rows used in Morozova’s diagnosis. Because of the variable form of the auto- zooecial chamber within and between specimens of E. exigua and because these shapes most consistently ap- proach that of a parallelogram to rectangle throughout the majority of the chamber depth, I have found use of the term “fabiform” to be unnecessary. The general age of species assigned this genus, Lower Carboniferous for the type species and Devonian to Permian for the genus overall, readily overlaps the age of the Warsaw. Exfenestella is similar in some characters to Ban- astella, n. gen.; however, the former is distinguished by the presence of hemisepta, different chamber out- line, presence of a pronounced keel, and stellate nodal shape. Similarities of the two genera include apertural stylets, relatively low angle at which chamber emerges from the reverse wall, and longest chamber direction paralleling lateral chamber walls. Species composition.— Approximately 30 species were recognized by Morozova. E. exigua is the only Warsaw species assigned to this genus. Range.— Devonian to Permian. Exfenestella exigua (Ulrich, 1890) Plate 16, figures 1-8, Plate 17, figures 1-7, Plate 18, figure 1; Text-figure 11; Table 19 Fenestella exigua Ulrich, 1890, p. 545, pl. 51, figs. 1, 1a [Warsaw Beds: Monroe County, Illinois]; Cumings, 1906, p. 1278, pl. 38, figs. 3-3a; Trizna, 1958, p. 121, pl. 33, figs. 4-5. Fenestella exigua var. springerensis Elias and Condra, 1957, pp. 406- 407, pl. 42, figs. 13-15. Diagnosis.—Zoarium robust, mesh spacing inter- mediate, pattern extremely regular; branches moder- ately robust, width narrow to intermediate, medium in thickness; straight, sinuous to broadly curved in trace, transversely circular to ovate, spacing interme- diate; branches joined at highly regular intervals by intermediate width and length dissepiments. Fenes- Text-figure 11.— Exfenestella exigua illustrated. 1, diagrammatic longitudinal view showing changing chamber outline from deep sec- tion near middle of branch (bottom of figure) to shallow section near adaxial edge of branch (top of figure) [Observe presence of well- developed inferior hemiseptum on proximal side of distal lateral wall (arrow).], x70; 2, diagrammatic tangential section showing changing outline of chamber from deep section near reverse wall (bottom of figure) to shallow section near obverse surface (top of figure) [Extension of inferior hemisepta across chambers (arrow) and short superior hemisepta at proximal vestigular edges typical of this genus are illustrated.], x 70; 3, diagrammatic transverse section across branch illustrating aperture orientation to obverse surface, x 70; 4, diagrammatic transverse section showing inferior hemiseptum de- velopment (arrow), x 70; 5, reconstruction of typical chamber shape (three-dimensional) as viewed from distal end of branch; chamber reconstructed from right side of branch [Observe inflection of inferior hemiseptum into adaxial edge of chamber (arrow).], x140; 6, re- construction of typical chamber shape (three-dimensional) as viewed from abaxial edge of branch; inflection of inferior hemiseptum into distal part of chamber is shown (arrow), x 140; 7, reconstruction of typical chamber shape (three-dimensional) as viewed from obverse zoarial surface [Extension of inferior hemiseptum across chamber (arrow) and superior hemiseptum causing inflections in chamber shape are illustrated.], x 140. MISSISSIPPIAN BRYOZOANS: SNYDER 69 trule size intermediate; shape regularly to irregularly elliptical, less frequently rectangular to ovate, highly Tegular. Autozooecial apertures small, shape circular to rarely ovate, surrounded by well-developed com- Plete peristome; seven to 11 (mean of nine) small sty- lets form as extension of peristome, fuse during asto- geny; two to four (most commonly three) apertures per fenestrule. Single, intermediate-width keel along mid- dle of obverse branch surface; single row of interme- diate-size, circular to ovate nodes along middle of ob- 70 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 verse branch surface. Autozooecial chamber size intermediate, emplaced in two rows, except third row at sites of branch bifurcation; outline asymmetrical parallelogram-shaped to rectangular throughout mid chamber, irregularly bilobate-elliptical near obverse surface. Chambers elongate parallel to proximal and distal chamber lateral walls. Aperture at distal-abaxial end of chamber, connected to chamber by interme- diate-length vestibule of variable length. Short superior hemiseptum present, inferior hemiseptum situated on proximal side of distal lateral chamber wall, one-third the distance in obverse direction from reverse wall. Lateral-wall budding-angle moderately variable (mean of 25°); reverse-wall budding-angle moderately vari- able (mean of 71°). Table 19 presents statistical criteria used in delim- iting this species. Exterior description.—Zoarium robust; expansion obversely curved, fan-shaped; mesh spacing interme- diate; moderate astogenetic thickening of both obverse and reverse lamellar skeleton; external zoarial pattern extremely regular. Probable mature widths of 20 to 30 mm; lengths 30 to 40 mm. Branches moderately robust; width thin to inter- mediate, variable; trace straight or sinuous, extending toward sites of dissepiment emplacement; lateral branches frequently broadly curved toward edge of zoarium. Branch spacing intermediate, distance be- tween adjacent branch centers extremely regular. Ob- verse surface texture slightly granular; surface rounded, except for single intermediate-width, well-developed keel, continuous, straight, extending along branch mid- line and causing positive inflection in obverse surface. Keel frequently covered by lamellar skeleton with as- togeny. Single row of nodes, well-developed and of intermediate-size, shape circular to ovate, elongate proximodistally; size and shape of nodes moderately regular; nodes project from middle of branch, two to four (most commonly three) nodes per fenestrule length, moderately evenly spaced; nodes and surrounding la- mellar skeleton on obverse surface thickening with as- togeny. Small stylets, moderately closely, unevenly spaced and moderately variably sized, across obverse branch surface, increasing in number and diameter with astogeny. Reverse surface texture slightly granular, coarsening with astogeny; bearing numerous rows of closely spaced longitudinal striae atop which are po- sitioned rows of small, closely spaced microstylets; size of microstylets variable; with astogeny longitudinal striae covered by lamellar skeleton, microstylets per- sist. Macrostylets present, large, circular to slightly ovate, elongate proximodistally; macrostylets moder- ately regular in size and shape, positioned in middle of branch along reverse surface primarily at or near site of branch-dissepiment junction, spacing highly variable; diameter increasing slightly with astogeny. Table 19.—Summary numerical analysis of Exfenestella exigua (Ulrich, 1890). For explanation of abbreviations of characters (left column), see Table 8b (foldout inside back cover). number of mea- coeffi- sure- standard cient of observed ments mean deviation variation range 1. WB 24 0.2958 | 0.0543 18.36 0.214-0.399 2. DBC 24 0.5603 0.0683 12.19 0.406-0.676 3. WD 24 0.1663 0.0346 20.81 0.123-0.254 4. LF 24 0.5600 0.0506 9.04 0.464-0.660 5. WF 24 0.2801 0.0302 10.78 0.220-0.327 6. AF 24 3.00 0.42 13.90 2-4 7. AL 24 0.0887 0.0028 3.16 0.083-0.093 9. ADB 24 0.2389 0.0090 3.77 | 0.220-0.254 10. AAB 24 0.3012 0.0315 10.46 0.252-0.359 11. ABB 24 0.2955 0.0596 20.17 0.181-0.388 12. DN 24 0.1191 0.0204 17.13 0.089-0.152 14. SNB 24 0.3430 0.0590 17.20 0.174-0.429 15. WK 24 0.0985 0.0212 21.52 0.061-0.132 16. DSO 24 0.0083 0.0020 24.10 0.006-0.120 17. SSO 24 0.0462 0.0122 26.41 0.024-0.071 18. WP 24 0.0101 0.0021 20.79 0.007-0.014 19. SA 24 9.00 1527 15:54 7-11 20. SAD 24 0.0119 0.0037 31.09 0.007-0.022 21. RSL 24 0.0919 0.0216 23.50 0.059-0.149 22. RSS 24 0.0111 0.0029 26.13 0.005-0.016 23. SSL 24 0.5667 0.2504 44.19 0.320-0.867 24. SSS 24 0.0241 0.0088 36.37 0.013-0.036 32. TRW 24 0.0079 0.0015 18.99 0.005-0.011 33. TLW 24 0.0071 0.0015 21.13 0.005-0.010 34. FWT 24 0.0588 0.0212 36.05 0.027-0.088 35. RWT 24 0.0854 0.0370 43.33 0.024-0.170 36. CL 24 0.2869 0.0106 3.69 0.267-0.310 372CD 24 0.1401 0.0147 10.49 0.115-0.164 38. MAW 24 0.1384 0.0111 8.02 0.123-0.168 40. VD 24 0.0652 0.0137 21.01 0.039-0.080 41. RA 24 43.17 5.26 12.19 33-55 42. LA 24 25.04 3.48 13.91 19-33 43. TB 24 0.3701 0.0802 21.67 0.249-0.527 Autozooecia in two rows across branch, except third row at sites of branch bifurcation where middle au- tozooecium evidently shared by both branches; pro- nounced thickening of branch proximal, slight thinning distal to sites of branch bifurcation. Heterozooecia ab- sent in all zoarial fragments examined. Dissepiment width intermediate, slightly greater than one-half that of branch, width variable; length inter- mediate, quite constant; dissepiments connect branch- es at highly regular intervals. Dissepiments exhibit moderate medial thinning, slight flaring at dissepi- ment-branch contact; highly recessed from obverse surface, less so from reverse. Pronounced astogenetic thickening of dissepiments, primarily toward proximal end of zoarium. Obverse dissepiment surface with one to three longitudinal striae across dissepiment perpen- ‘dicular to branch length; reverse dissepiment surface with similar but more numerous longitudinal striae atop which are positioned small stylets; number of MISSISSIPPIAN BRYOZOANS: SNYDER 71 Striae covered by lamellar skeleton and stylet size slightly increasing with dissepiment thickening during astogeny; both obverse and reverse dissepiment sur- faces slightly granular in texture. Emplacement of dis- Sepiments approximately perpendicular to branch length. Apertures commonly open on proximal or dis- tal edge, less frequently in middle of dissepiment edge at branch-dissepiment contact; arranged symmetri- cally or asymmetrically between branches. Fenestrule size intermediate; shape most commonly Tegularly to irregularly elliptical, elongate proximodis- tally, less frequently approaching rectangular to ovate; highly regular in size and shape; moderately expanding In width, less so in length in obverse-reverse direction. Mean width of fenestrule slightly less than branch width 9n obverse surface, approximately equal to or slightly &reater on reverse; fenestrule opening decreasing in size toward proximal end of zoarium due to astogenetic thickening of the lamellar skeleton. Width to length ratio of fenestrule 1:2, highly constant; constancy of Width and length equal. Two to four apertures per fe- Destrule length, three most common; spacing of closest aperture centers along branch approximately four-fifths of Spacing across branch and across fenestrule; spacing along and across branch highly to moderately constant, Spacing across fenestrule highly variable. Autozooecial apertures small, shape circular, very rarely slightly ovate, elongate proximodistally, highly Uniform in size and shape; opening orientation ranging from parallel to plane of obverse surface to attaining à slight angle toward fenestrule; thin, well-developed complete peristome present, seven to 11 (mean of nine) small stylets form as extensions of peristome, frequent- ly stylets fuse during astogeny. Aperture margin ex- tends into fenestrule, causing slight inflections in fe- Destrule outline on obverse surface. Terminal diaphragms present, most commonly found in proxi- mal and central part of zoarium. Zoarial supports develop moderately infrequently, form as extensions of reverse zoarial surface and lateral edge of zoarium. Interior description. — Branches circular to ovate in transverse view, frequently slightly enlarged on ob- Verse side of branch, elongate in obverse-reverse di- rection. Branch thickness medium, variable. Autozooecial living chamber size intermediate, bise- rially arranged in alternating rows along planar branch axial wall; axial wall sinuous, exhibiting pronounced Inflections toward and connecting with relatively long Chamber lateral walls. Chamber longest dimension Paralleling proximal and distal chamber lateral walls. Autozooecial chamber outline attaining an asymmet- Neal diamond shape near reverse wall; rapidly becom- Mg an asymmetrical parallelogram to rectangle thr Oughout most of mid chamber; outline irregularly bilobate-elliptical near obverse surface, longest direc- tion of ellipse oriented distal-abaxially; chamber shape highly regular. Aperture positioned at distal-abaxial end of chamber, connected to chamber by well-devel- oped, intermediate-length vestibule of variable length. Autozooecial chamber width and depth approximately equal; ratio of depth to length approximately 1:2; length much more constant than width and depth. Moder- ately well-developed short, superior hemiseptum pres- ent, formed as extension of proximal-adaxial vestib- ular edge, forming partial restriction between vestibule and autozooecial chamber; well-developed inferior . hemiseptum present, situated on proximal side of dis- tal lateral chamber wall one-third the distance in ob- verse direction from reverse wall; lateral wall exhib- iting slight inflection into chamber toward site of inferior hemiseptum emplacement, with inferior hemi- septum extending up to half the diameter of chamber depth. Autozooecial chamber diverges laterally from middle of branch at a moderately variable angle (mean of 25°); from reverse wall at a moderately variable angle (mean of 71°). Three-dimensionally reconstructed chamber form a rectangular box exhibiting inflections in middle of box length due to hemiseptal emplacement; long dimen- sion as viewed from lateral edge of branch; width and depth approximately equidimensional as viewed from obverse surface and distal end of branch, respectively. Internal granular skeletal layer relatively thin, con- tinuous with obverse nodes, stylets, peristome and ap- ertural stylets; reverse longitudinal striae and both large and small stylets; across dissepiments and in the mid- dle of zoarial supports. Outer lamellar layer thick, with moderate to pronounced astogenetic thickening, most prevalent toward end of zoarium. Remarks.— Exfenestella exigua was first recognized as Fenestella Lonsdale, 1839, by Ulrich (1890) from the Warsaw Beds near Warsaw, Illinois. The exterior appearance of E. exigua closely resembles that of Ar- chimedes wortheni (Hall, 1857b), with traditional meshwork formula and number of apertural stylets similar in both species. However, E. exigua is readily distinguished in interior view by the presence of su- perior and inferior hemisepta, which are lacking in A. wortheni, and by having an asymmetrical parallelo- gram-shaped to rectangular chamber outline in mid chamber, as opposed to the irregular pentagonal cham- ber outline in A. wortheni. The relative chamber dimensions in E. exigua, par- ticularly with regard to longest chamber dimension, closely resemble those of species of Banastella, n. gen., although chamber shape and hemiseptal development is very different between E. exigua and species of Ban- astella. Hemiseptal placement in E. exigua resembles that in the laxifenestellids, however chamber shapes 12 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 and direction of chamber elongation are significantly different. Placement within the genus Exfenestella by Moro- zova (1974) appears appropriate, although access to her type materials would definitely be desirable. From Morozova’s illustrations, the outline of chambers in tangential views and hemiseptal emplacement for Ex- fenestella are the critical criteria used for placement of this species herein. Material studied. — Twenty-eight exterior fragments, 19 sectioned specimens; largest zoarial fragment 18 x 26 mm (width to length). The thin internal granular skel- etal layer, particularly in the lateral walls, results in poor preservation with many fragments being crushed and of little use for internal analysis. Occurrence.— Exfenestella exigua is relatively rare in the Warsaw study area. It is most common in the Valmeyer, St. Louis, and associated localities, and is restricted to Warsaw Beds in the north. Figures and/or measured specimens.—Ul X-6873 (loc. 11, sample 57), 6749, 6898, 6761-6764, 6716, 6810, 6816—6818, 6735, 6736 (loc. 49B, samples 125 13,15), 6769, 6768, 6759, 6868, 6942, 7021 (loc. 47A, samples 32, 37). Genus BANASTELLA, new genus Etymology of name.—Named for Champaign-Ur- bana, where the work leading to recognition of this genus took place. Type species. — Banastella guensburgi, n. sp. Diagnosis.—Zoarium ranging from delicate to ex- tremely robust, mesh ranging from close to open; chamber outline irregularly rectangular, parallelo- gram-shaped to irregularly pentagonal in mid tangen- tial section, chamber size typically large to less com- monly intermediate; aperture size large, apertural stylets present in most species; three rows of autozooecia pres- ent for prolonged distances proximal to branch bifur- cation; chamber reverse-wall budding-angle low, means vary between 22? and 55°. Three-dimensionally recon- structed chamber form a rectangular to parallelogram- shaped box. Description.— Zoarium robustness ranging from del- icate to extremely robust, expansion flat, obversely to reversely curved, slightly sinuous or cupped; mesh spacing variable, ranging from close to open, regular to irregular. Branch width intermediate to more commonly wide, straight to sinuous in trace with lateral branches broad- ly curved toward edge of zoarium; branch surface rounded to angular. Keel present, typically single to rarely multiple, width varying from narrow to wide, straight to anastomosing, moderately to greatly in- creasing with astogeny and frequently covered by la- mellar skeleton. Nodes present, emplacement mono- serial, size large to intermediate, shape typically stellate to more rarely elliptical, located atop middle of keel, spacing ranging from intermediate to wide. Obverse stylets present or absent, size small to intermediate, occurring across obverse surface, however, most com- mon at keel edge and between nodes. Microstylets pres- ent, size small to intermediate. Macrostylets absent. Autozooecia in two rows, third row at sites of branch bifurcation or for moderate to pronounced distances along branch proximal to sites of branch bifurcation. Heterozooecia (ovicells?) present in some species. Dissepiment width ranging from thin to wide, length varying from short to long, placement regular to vari- able. Fenestrule size intermediate to large, shape varying from elliptical, ovate, rectangular, to approaching square. Aperture size large, shape ovate to more rarely cir- cular, oriented parallel to plane of obverse surface or at slight angle toward fenestrule. Peristome present, complete; apertural stylets either present or absent, when present well-developed, form as extensions of peristomal edge; terminal diaphragms present, posi- tioned at proximal end and throughout zoarium. Branch shape in cross-section from circular to ovate to elliptical, shallow to thick in depth. Autozooecial chamber size typically large, less com- monly intermediate, chambers biserially emplaced along straight to slightly sinuous axial wall; maximum chamber length parallel to proximal and distal lateral chamber walls in most species, rarely parallel to reverse wall at proximal and curving to become parallel to lateral walls toward distal end of chamber. Chamber outline varying from triangular to irregularly pentag- onal to ovate near reverse wall; becoming a parallel- ogram, irregular rectangle to irregular pentagon in mid chamber and throughout most of chamber depth; ir- regularly ovate to elliptical near obverse surface. Ves- tibule present, varying from short to long. Superior hemiseptum typically absent, although short superior hemiseptum present in one species analyzed; present at proximal vestibular edge; inferior hemiseptum ab- sent. Lateral-wall budding-angle means ranging from 16? to 22°; reverse-wall budding-angle means from 22° to 55°. Lamellar skeletal layer varying from thin to thick, exhibiting slight to pronounced astogenetic thickening; granular skeletal layer thin to thick, exhib- iting slight astogenetic thickening. Three-dimensionally reconstructed chamber form an irregular to slightly irregular, rectangular to paral- lelogram-shaped box, frequently with tubular exten- sion at distal obverse end caused by the vestibule. Text-figure 12 illustrates zoarial outlines in longi- ' tudinal, tangential, and transverse orientations, and three-dimensional chamber reconstructions from ab- MISSISSIPPIAN BRYOZOANS: SNYDER 13 axial branch edge, obverse surface, and distal views. Remarks.—This genus includes a significant per- centage of fenestellid species found in the Warsaw. Its members are typically well-preserved due to their ro- bust nature. Species of Banastella can be separated from other fenestellids by the following combination of characters: frequent presence of well-developed apertural stylets, which fuse during ontogeny to form a peristome; large aperture opening, complete lack of inferior and rare Superior hemisepta, typically large to less commonly intermediate autozooecial chamber size, elongate shape Parallel to proximal and distal lateral chamber walls, low reverse-wall budding-angle, and typically stellate nodes, Autozooecial chambers occurring in more than two TOWS across the branch appear directly related to low chamber budding angles from the reverse wall; such low angles are present in both Banastella and Polypora McCoy, 1844, the latter being recognized by typically having more than two rows of autozooecia across the branch Proximal to sites of branch bifurcation. A pos- sible close phylogenetic connection between Banastella and Polypora is suggested by the presence of stellate nodes, well-developed apertural stylets, and similar Chamber outlines and low reverse-wall budding-angles. Ulrich (1 890) assigned Polypora biseriata Ulrich, 890 to the polyporids based on pronounced external Similarities even though P. biseriata had two rows of Zooecia across the branch, a criterion that should have excluded placement in that genus. Herein. P. biseriata 18 placed in Banastella which, as stated above, appears Phylogenetically close to Polypora. Ulrich’s insight into taxonomy of fenestellids, based significantly on exte- nor analysis of a great volume of material, is impres- Sive even after 100 years. ‚Species composition.—Six Warsaw species are as- Signed to this genus: Banastella guensburgi, n. sp., Ban- astella cingulata (Ulrich, 1890), Banastella mediocre- Orma, n. sp., Banastella limitaris (Ulrich, 1890), Banastella biseriata (Ulrich, 1890), and Banastella de- licata, n. sp. Range.—Lower Mississippian (Valmeyeran), pres- Ent in the Keokuk, Warsaw, Salem and St. Louis for- Mations, Banastella guensburgi, new species Plates 18, figures 2-9, Plate 19, figures 1-10, Plate 20, figure 1; Text-figure 12; Table 20 Etymology of name.—Named for Tom Guensburg, Who assisted greatly in developing techniques for work- Ing with these bryozoans. . Diagnosis. —Zoarium extremely robust, mesh spac- ing Close, pattern moderately regular; branches robust, wide, extremely thick in depth; straight to sinuous, broadly curved at lateral zoarial edge; transversely el- liptical, spacing moderately close; branches joined at moderately constant intervals by intermediate-width, short dissepiments. Fenestrules large; shape irregularly ovate to more rarely irregularly elliptical, moderately variable. Autozooecial apertures large, shape circular to slightly ovate, surrounded by well-developed, wide, complete peristome formed from fusion of 15 to 25 large stylets regularly positioned around aperture; three to five (most commonly four) apertures per fenestrule. Single wide, continuous keel along middle of obverse branch, atop which are positioned large, stellate, four- _ to eight-lobed nodes. Autozooecial chambers large, emplaced in two rows, except three rows occurring for pronounced distances proximal to sites of branch bi- furcation; outline irregularly pentagonal near reverse wall, rapidly becoming a rectangle to parallelogram in mid and throughout most of chamber length, irregu- larly ovate near obverse surface, slightly enlarged at distal end. Chamber longest dimension parallel to proximal and distal lateral chamber walls. Aperture at distal and slightly abaxial end of chamber, connected to chamber by long vestibule of variable length. Su- perior and inferior hemisepta both absent, Lateral-wall budding-angle highly variable (mean of approximately 19°); reverse-wall budding-angle moderately constant (mean of approximately 38°). Enlarged apertural open- ings, possibly representing ovicells. Table 20 presents statistical criteria used in delim- iting this species. Exterior description.—Zoarium extremely robust, expansion flat to slightly obversely curved, fan-shaped; mesh spacing close; pronounced astogenetic thickening of both obverse and reverse lamellar skeleton; zoarial pattern moderately regular. Probable mature widths 30 to 45 mm; lengths 30 to 50 mm. Branches robust; wide, moderately variable in width; straight to slightly sinuous, with inflections toward sites of dissepiment insertion; lateral branches frequently broadly curved toward edge of zoarium. Branch spac- ing moderately close, distance between adjacent branch centers regular. Obverse surface texture smooth, be- coming slightly granular with astogeny; surface round- ed; except single wide, extremely well-developed keel; keel continuous, straight to slightly anastomosing, ex- tending along branch midline and causing pronounced positive inflection on obverse surface. With astogeny pronounced thickening of keel occurs; keel forming a ropy expansion across most of obverse surface toward proximal end of zoarium, frequently extending over adaxial edge of aperture; lamellar skeleton covering much of keel with astogeny. Single row of extremely well-developed, large stellate nodes with four to eight pronounced lobes; node size regular, shape moderately variable; nodes projecting from middle of keel; one to 74 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 two per fenestrule length; widely, moderately evenly spaced, most commonly located at or near branch— dissepiment junction; with astogeny node diameter in- creases and nodes frequently become covered by thick- ened secondary lamellar skeleton of the keel. Inter- mediate, highly variable size stylets in single row along middle of keel, located between nodes and along ab- axial edges of keel. Reverse surface texture highly gran- ular, becoming more coarsely granular with astogeny; bearing an intermediate number of closely spaced lon- gitudinal striae atop which are positioned rows of small, closely spaced, variable-size microstylets. With asto- geny longitudinal striae disappear, becoming covered by lamellar skeleton, and microstylets become larger, more unevenly positioned across surface. Autozooecia arranged in two rows, except third row at site of, or three rows occurring for pronounced distances proxi- mal to sites of branch bifurcation; branches with pro- nounced thickening proximal, thinning distal to sites of branch bifurcation. Enlarged apertural openings, possibly representing ovicells, infrequently occurring at most proximal end of zoarium. Dissepiments of intermediate width, approximately one-half width of branch, width highly variable; short, variable in length; connect branches at moderately con- stant intervals. Dissepiments with pronounced medial thinning, flaring at branch- dissepiment contact; slight- ly recessed from both obverse and reverse surfaces. Moderate to pronounced astogenetic thickening of dis- sepiments. Obverse dissepiment surface lacking or- namentation; reverse dissepiment surface with longi- tudinal striae oriented perpendicular to branch length, atop which occur rows of small microstylets; striae covered by lamellar skeleton and microstylet size in- creasing with astogeny; obverse dissepiment texture smooth, reverse surface highly granular, both coars- ening with astogeny. Emplacement of dissepiments ap- proximately perpendicular to branch length. Apertures commonly open on proximal or distal edge, or in mid- dle of dissepiment edge at branch-dissepiment contact; arranged symmetrically or asymmetrically between branches. Fenestrules large; shape most commonly irregularly ovate to more rarely irregularly elliptical, highly elon- gate proximodistally; moderately irregular in size and shape; expanding moderately in width and length in obverse-reverse direction. Mean width of fenestrule appreciably less than branch width on obverse surface, approaching equal to branch width on reverse; fenes- trule opening decreasing in size toward proximal end of zoarium due to astogenetic thickening of lamellar skeleton. Width to length ratio of fenestrule ranging from 1:3 to 1:5, moderately variable; mean ratio of width to length approximately 1:4; length of fenestrule more constant than width. Three to five (most com- Table 20.— Summary numerical analysis of Banastella guensburgi, n. sp. For explanation of abbreviations of characters (left column), see Table 8b (foldout inside back cover). number of mea- coeffi- sure- standard cient of observed ments mean deviation variation range 1. WB 24 0.4568 0.0969 21.02 0.257-0.600 2. DBC 24 0.8121 0.1433 17.65 0.563-1.063 3. WD 24 0.3145 0.1378 43.82 0.200-0.820 4. LF 24 1:21:51 02012297) e Ee 5. WF 24 0.3458 0.0891 25.11 0.200-0.500 6. AF 24 4.21 0.59 13.78 3-5 7. AL 24 0.1958 0.0087 4.44 0.180-0.210 8. AW 24 0.1647 0.0204 12.39 0.120-0.200 9. ADB 24 0.4367 0.0523 11.98 0.360-0.560 10. AAB 24 0.4188 0.0529 12.63 0.320-0.520 11. ABB 24 0.4524 0.0852 18.83 0.343-0.660 12. DN 24 0.1929 0.0306 15.86 0.110-0.250 14. SNB 24 1.4579 0.2368 16.24 1.050-2.130 15. WK 24 0.2133 0.0756 35.44 0.110-0.375 16. DSO 24 0.0101 0.0035 34.65 0.006-0.017 17. SSO 24 0.1144 0.0438 38.29 0.050-0.200 18. WP 24 0.0523 0.0134 25.62 0.036-0.080 19. SA 24 15129 2.44 13.34 15-25 20. SAD 24 0.0185 0.0126 68.11 0.007-0.038 22. RSS 24 0.0176 0.0045 25.57 0.011-0.028 24. SSS 24 0.0412 0.0174 42.23 0.024-0.073 32. TRW 24 0.0074 0.0014 18.92 0.005-0.010 33. TLW 24 0.0078 0.0014 17.95 0.005-0.010 34. FWT 24 0.1296 0.0396 30.56 0.070-0.175 35. RWT 24 0.0839 0.0251 29.92 0.050-0.140 36. CL 24 0.5890 0.0466 7.91 | 0.500-0.675 37. CD 24 0.2243. ° 0.0185 8.25 0.200-0.250 38. MAW 24 0.1743 0.0191 10.96 0.150-0.210 40. VD 24 0.1140 0.0280 24.56 0.093-0.158 41. RA 24 38.17 3.50 9.16 33-48 42. LA 24 18.67 4.44 23.78 9-30 43. TB 24 1.0096 0.1667 16.51 0.750-1.380 Text-figure 12.—Banastella guensburgi illustrated. 1, diagram- matic longitudinal section showing changing chamber outline from deep section near middle of branch (bottom of figure) to shallow section near abaxial edge of branch (top of figure) [Observe mod- erately low reverse-wall budding-angle (arrow) characteristic of this genus.], x 70; 2, diagrammatic tangential section showing changing chamber outline from deep section near reverse-wall budding-site (bottom of figure) to shallow section near obverse surface (top of figure) [Apertural stylets are well-developed in this example (arrow).], x70; 3, diagrammatic transverse section across branch showing typ- ical aperture orientation to obverse surface (arrow), x70; 4, dia- grammatic transverse section illustrating reverse stylet development as an extension of granular skeleton (arrow), x 70; 5, reconstruction oftypical chamber shape (three-dimensional) as viewed from abaxial edge of branch [Observe much greater length than width or depth typical of this genus.], x140; 6, reconstruction of typical chamber shape (three-dimensional) as viewed from obverse surface; chamber reconstructed is from right side of branch, x 140; 7, reconstruction of typical chamber shape (three-dimensional) as viewed from distal . end of branch; chamber reconstructed is from right side of branch [Observe slight inflection into vestibule by apertural stylets (arrow).], x 140. MISSISSIPPIAN BRYOZOANS: SNYDER 13 monly four) apertures per fenestrule length; distance and across fenestrule all approximately equal; spacing between closest aperture centers along, across branch, along and across branch slightly more constant than across fenestrule; all moderately constant. Autozooecial apertures large, shape circular to slightly ovate, elongate proximoabaxially; width to length ratio approximately 4:5, size and shape uniform; opening oriented parallel to plane of obverse surface or at slight angle toward fenestrule; wide, extremely well-devel- oped peristome frequently present, continuous around aperture where present, occurring primarily at proxi- mal end of zoarium. Fifteen to 25 (most commonly 18) large, variable-size, well-developed, and regularly positioned stylets surround aperture; peristome de- velops from fusion of these stylets during astogeny, with stylets most common at lateral and distal edges of zoarium. Aperture margins extend into fenestrule, causing pronounced inflections in fenestrule outline on obverse surface. Centrally thickened terminal dia- phragms present, commonly occurring throughout the zoarium. Zoarial supports commonly develop as extensions of reverse zoarial surface and lateral edge of zoarium. Interior description.—Branches elliptical in trans- verse section, moderately flaring on obverse side, elon- gate in obverse-reverse direction. Branches extremely thick in depth, moderately variable. Autozooecial living chambers large, biserially ar- ranged in alternating rows along planar branch axial wall; axial wall straight to slightly sinuous, extending toward and connecting with long chamber lateral walls. Chamber longest direction parallel to proximal and distal lateral chamber walls. Autozooecial chamber outline irregularly pentagonal near reverse-wall bud- ding-site; rapidly becoming a rectangle to parallelo- gram in middle and throughout most of chamber length, irregularly ovate near obverse surface, slightly enlarged at distal end of chamber; chamber shape highly uni- form. Aperture positioned at distal and slightly abaxial end of chamber, connected to chamber by long ves- tibule of moderately variable length. Ratio of auto- zooecial chamber width to depth approximately 3:4; depth to length ratio 3:8; width, depth, and length all highly constant. Superior and inferior hemisepta both absent. Autozooecial chambers diverge laterally from middle of branch at a highly variable angle (mean of 19°); from reverse wall at a moderately constant angle (mean of 38°). Three-dimensionally reconstructed chamber form a slightly irregular rectangular box with tubular exten- sion at distal-obverse end of vestibule; long dimension as viewed from lateral edge of branch; depth, viewed from distal end of branch, moderately greater than width, viewed from obverse surface. Large apertural stylets connect to inner granular skel- etal material; stylets increase in diameter in the ves- tibule, forming a slight to moderate restriction im- mediately chamberward from aperture opening. PALAEONTOGRAPHICA AMERICANA, NUMBER 57 Internal granular skeletal layer moderately thick, well- developed; continuous with obverse nodes, stylets, peristome, and keel; reverse longitudinal striae and microstylets atop these striae; across dissepiments and in the middle of zoarial supports. Outer lamellar layer thick, showing pronounced astogenetic thickening on both obverse and reverse exterior surface, greatest at proximal end of zoarium. Remarks.—Reverse-wall budding-angle, chamber dimensions, aperture dimensions and spacing, and ap- ertural stylet count (when stylets are present) are all characters with low coefficients of variation and high taxonomic importance within Banastella. Mesh spac- ing and dimensions, branch width and thickness, and stylet and nodal diameters, although usually exhibiting higher variability than reverse-wall budding-angle, etc., are also important. Pronounced astogenetic thickening of the lamellar skeletal layer is characteristic of B. guensburgi, partic- ularly over the keel, which expands to form a ropy overgrowth which partially covers apertures. This gives a highly varied appearance to the zoarial exterior, re- quiring reliance on interior characters for proper spe- cies assignment. Other distinguishing characters in- clude large aperture openings surrounded by highly symmetrical apertural stylets that extend into and slightly fill the middle of vestibule, and large, well- developed lobate nodes. Apertural stylets occur in oth- er species of Banastella, but they are best developed in B. guensburgi. B. guensburgi is similar in exterior appearance to both Fenestella regalis Ulrich, 1890 [pp. 538-539] and Fenestella funicula Ulrich, 1890 [pp. 542-543]. F. re- galis, although having a similar ropy keel, has much wider branches and coarser mesh pattern than P. guensburgi. F. funicula has similar branch width, mesh symmetry, and ropy keel to that in B. guensburgi, how- ever smaller apertures, lack of apertural stylets, greater number of apertures per fenestrule length, and lack of three rows of autozooecia for moderate to pronounced distances proximal to sites of branch bifurcation readi- ly distinguish F. funicula from B. guensburgi. Material studied.— Fourty-eight exterior fragments, 16 sectioned specimens; largest zoarial fragment 27 x 58 mm (width to length). Little skeletal alteration of these colonies is evident, although several sectioned zoaria were crushed, probably due to compacting of mud. Occurrence.— Banastella guensburgi is extremely common at the Valmeyer and St. Louis localities; it ranges through the Warsaw, but is much less common toward the top. It is abundant in both limestones and shales. Holotype. — UI X-6779 (loc. 49B, sample 12). Paratypes.—UI X-6748, 6794-6796, 6780, 7016, 6941, 6959— 6966 (loc. 49B, samples 8, 12, 13). MISSISSIPPIAN BRYOZOANS: SNYDER "y Table 21. Summary numerical analysis of Banastella cingulata (Ulrich, 1890). For explanation of abbreviations of characters (left column), see Table 8b (foldout inside back cover). number of mea- coeffi- sure- standard cient of observed ments mean deviation variation range l. WB 24 0.3150 0.0744 23.62 0.188-0.456 2. DBC 24 0.4820 0.0595 12.4 0.375-0.580 3. WD 24 0.2091 0.0417 19.94 0.125-0.288 4. LF 24 0.5611 0.0980 17.47 0.356-0.675 5. WF 24 0.3061 0.0723 23.62 0.219-0.433 6. AF 24 3.00 0.67 22.30 2-4 7. AL 24 0.1697 0.0111 6.54 0.148-0.188 8. AW 24 0.1484 0.0169 11.39 0.129-0.188 9. ADB 24 0.3144 0.0578 18.38 — 0.260-0.450 10. AAB 24 0.2757 0.0379 13.75 0.243-0.320 ll. ABB 24 0.3228 0.0540 16.73 0.240-0.400 12. DN 24 0.0955 0.0288 30.16 0.060-0.163 14. SNB 24 0.3812 0.0766 20.09 0.275-0.533 15. WK 24 0.0250 0.0087 34.80 0.012-0.043 18. Wp 24 0.0342 0.0096 28.07 0.021-0.071 19. SA PALEIS 3.42 16.24 16-28 20. SAD 24 0.0158 0.0034 2.52 0.012-0.024 22. RSS 24 0.0117 0.0025 21.37 0.009-0.018 24. SSS 24 0.0541 0.0162 29.94 0.029-0.086 32. TRW 24 0.0101 0.0022 21.78 0.006-0.014 3. TLW 24 0.0187 0.0078 41.71 0.010—0.034 3. FWT 54 0.1242 0.0633 50.97 0.049-0.245 35. RWT 54 0.1619 0.0689 42.56 0.069-0.286 36. CL 24 0.4894 0.0291 5.95 0.449-0.554 37. CD 24 0.2122 0.0171 8.06 0.185-0.243 3. MAW 24 0475 9019189 ola 1012220856 40. VD 24 01280" 70:04180.032072 2010720. 214 41. RA 24 55.00 4.79 8.70 46-62 42. LA 24 15.83 2.97 18.77 16-22 43. TB 24 (5457 01282. 25140. 03080715 Banastella cingulata (Ulrich, 1890) Plate 20, figures 2-10, Plate 21, figures 1-6; Table 21 Fenestella cingulata Ulrich, 1890, p. 543, pl. 52, figs. 1-1d [Keokuk Group: Nauvoo, Illinois; Keokuk, Iowa]; Keyes, 1894, p. 23 [Keo- kuk Limestone; Keokuk, Iowa]. Diagnosis.—Zoarium robust, mesh spacing inter- Mediate, pattern regular; branches robust, width lower- End intermediate, thick in depth; branches sinuous, lateral branches frequently broadly curved toward Z0arial edge; transversely elliptical, spacing close; branches joined at moderately regular intervals by in- termediate-width, very short dissepiments. Fenestrule Size intermediate; shape ranging from ovate to ellip- tical, moderately variable. Autozooecial apertures large, Shape circular to slightly ovate, surrounded by inter- Mediate-size well-developed, complete peristome formed from fusion of 16 to 28 intermediate-size sty- ets regularly positioned around aperture; two to four Most commonly three) apertures per fenestrule. Single Narrow, intermittent keel along middle of obverse branch, from which project intermediate-size, stellate multilobed nodes. Autozooecial chambers large, em- placed in two rows, except three rows occurring for pronounced distances proximal to sites of branch bi- furcation; outline irregularly pentagonal near reverse wall, rapidly becoming irregularly rectangular to more rarely slightly irregularly pentagonal throughout most of chamber, irregularly ovate to elliptical near obverse surface, slightly enlarged at distal end. Chambers elon- gate parallel to proximal and distal lateral chamber walls. Aperture at distal-abaxial end of chamber, con- nected to chamber by long vestibule of highly variable length. Superior and inferior hemisepta both absent. _ Lateral-wall budding-angle highly variable (mean of 16°); reverse-wall budding-angle moderately constant (mean of 55°). Table 21 presents statistical criteria used in delim- iting this species. Exterior description.—Zoarium robust; expansion curving slightly toward obverse surface, rarely cupped, fan-shaped; mesh spacing intermediate; pronounced astogenetic thickening of obverse and reverse lamellar skeleton; external zoarial pattern regular. Probable ma- ture widths 20 to 25 mm; lengths 20 to 30 mm. Branches robust; width lower-end intermediate, variable; generally sinuous, exhibiting slight inflections toward sites of dissepiment emplacement, lateral branches frequently broadly curved toward edge of zoarium. Branches closely spaced, distance between adjacent branch centers extremely regular. Obverse surface texture granular; surface moderately angular as a result of close spacing of large apertures; single nar- row, poorly developed, intermittent, highly anasto- mosing keel curving around apertures on obverse branch surface, causing very slight inflection on ob- verse surface. Keel covered by lamellar skeleton during astogenetic thickening and obverse surface becomes increasingly granular in texture. Nodes monoserially emplaced and well-developed, size intermediate, shape stellate, multilobed, generally elongate proximodistal- ly, highly irregular in size and shape, positioned in slightly anastomosing way along middle of obverse branch surface, projecting from keel and most com- monly occurring between two apertural openings across the branch surface; two to three (most commonly two) per fenestrule length, intermediately evenly spaced, node diameter greatly increasing with astogeny. Re- verse surface texture moderately granular, coarsening with astogeny; bearing an intermediate number of in- termediately spaced longitudinal striae which become covered by lamellar skeleton with astogeny; closely spaced rows of small microstylets positioned atop stri- ae; microstylets increase in diameter and become scat- tered across reverse zoarial surface with astogeny. Au- tozooecia arranged in two rows, except three rows frequently occurring for pronounced distances proxi- 78 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 mal to sites of branch bifurcation; pronounced thick- ening of branches proximal, thinning distal to sites of branch bifurcation. Dissepiments of intermediate width, two-thirds that of branch, width moderately constant; very short, moderately variable in length; connect branches at moderately regular intervals. Pronounced astogenetic thickening of dissepiments. Dissepiments exhibiting pronounced medial thinning, flaring at branch-dissep- iment contact; highly recessed from obverse, approx- imately even with reverse surface. Obverse dissepi- ment surface lacking ornamentation; reverse surface with rows of poorly developed longitudinal striae ori- ented perpendicular to branch length, atop which proj- ect rows of small stylets; striae covered by lamellar skeleton, stylet diameter increasing as dissepiments thicken during astogeny; both obverse and reverse dis- sepiment surfaces granular in texture. Emplacement of dissepiments perpendicular or approximately perpen- dicular to branch length. Apertures commonly open on proximal or distal edge, less frequently in middle of dissepiment at branch-dissepiment contact; ar- ranged symmetrically or asymmetrically between branches. Fenestrule size intermediate; shape ranging from ovate to elliptical, elongate proximodistally, to rarely approaching square; moderately regular in size, mod- erately variable in shape; greatly expanding in width and length in obverse-reverse direction. Mean width of fenestrule much less than branch width on obverse surface, approximately equal on reverse; fenestrule opening decreasing in size toward proximal end of zoarium with astogenetic thickening of lamellar skel- eton. Width to length ratio of fenestrule ranging from 1:1 to approximately 1:3, variable; mean width to length ratio approximately 1:2; length more constant than width. Two to four (most commonly three) apertures per fenestrule length; distance between closest aperture centers along branch and across branch approximately equal, slightly less than spacing of aperture centers across fenestrule; spacing along branch, across branch, and across fenestrule all moderately variable. Autozooecial apertures large, shape circular to slightly ovate, elongate proximodistally, width to length ratio approximately 7:8, size uniform, shape moderately uniform; opening oriented parallel to plane of obverse surface; intermediate-size, well-developed peristome present, continuous around aperture at proximal end of zoarium. Sixteen to 28 (most commonly 21) stylets, intermediate in size, well-developed and regularly po- sitioned, surrounding aperture; peristome develops from fusion of these stylets during astogeny, with sty- lets present at middle and distal edges of zoarium. Aperture margins exhibit pronounced extension into fenestrule, causing pronounced inflections in fenestrule outline on obverse surface. Centrally thickened ter- minal diaphragms commonly occurring throughout the zoarium. Large zoarial supports develop as extensions of re- verse zoarial surface and lateral edge of zoarium. Interior description.—Branches elliptical in trans- verse section, moderately flaring on obverse side, elon- gate in obverse-reverse direction. Branches thick, vari- able in depth. Autozooecial living chambers large, biserially ar- ranged in alternating rows along planar branch axial wall; axial wall straight to slightly sinuous, extending toward and connecting with long chamber lateral walls. Chamber longest direction parallel to proximal and distal lateral chamber walls. Autozooecial chamber outline irregularly pentagonal near reverse-wall bud- ding-site; rapidly becoming irregularly rectangular to more rarely slightly irregularly pentagonal throughout most of chamber depth; irregularly ovate to elliptical near obverse surface, slightly enlarged at distal end of chamber; chamber shape moderately regular. Aperture located at distal-abaxial end of chamber, connected to chamber by long vestibule of highly variable length. Ratio of autozooecial chamber width to depth ap- proximately 7:10; depth to length ratio approximately 4:9: chamber length and depth more constant than width. Superior and inferior hemisepta both absent. Autozoocial chamber diverges laterally from middle of branch at a highly variable angle (mean of 16°); from reverse wall at a moderately constant angle (mean of 55°). Three-dimensionally reconstructed chamber form an irregular rectangular box, with slight tubular exten- sion of vestibule; long dimension as viewed from lat- eral edge of branch; depth, viewed from distal end of branch, moderately greater than width, viewed from obverse surface. Intermediate-size apertural stylets connect to inner granular skeletal material; stylets increase in diameter in the vestibule, forming a slight restriction immedi- ately chamberward from aperture opening. Internal granular skeletal layer extremely thick; continuous with obverse keel, nodes, and apertural stylets; reverse lon- gitudinal striae and stylets; across dissepiments and in the middle of zoarial supports; granular layer exhib- iting secondary astogenetic thickening slightly filling chamber. Outer lamellar layer thick, exhibiting pro- nounced astogenetic thickening on both obverse and reverse exterior surfaces at proximal end of zoarium. Remarks.— Ulrich (1890, p. 543) described the ap- ertural stylets in B. cingulata as “a ring of minute tu- bules around the zooecial aperture.” A longitudinal section through one of the stylets (Pl. 20, figs. 7a, 8b) illustrates the granular skeletal composition and their connection with the internal granular skeleton. MISSISSIPPIAN BRYOZOANS: SNYDER 79 Characters typical of species of Banastella include autozooecial chamber shape and great chamber elon- gation, direction of maximum elongation paralleling lateral chamber walls, apertural stylets and their fusion to form a peristome, stellate nodes, and centrally thick- ened terminal diaphragms. B. cingulata is distin- guished from other species of Banastella by its closer mesh spacing, moderately high reverse-wall budding- angle compared to other species of this genus, and Characteristic autozooecial chamber dimensions. Material studied.—Twenty-two exterior fragments, five sectioned specimens; largest zoarial fragment 24x28 mm (width to length). The robust nature of the Colonies leads to preservation of nearly complete zoar- ia, although some secondary alteration of microstruc- ture is evident. Occurrence.—Banastella cingulata is moderately common at the Valmeyer and St. Louis localities, and Tanges throughout the Warsaw. It is present in both limestone and shale. Figured and/or measured specimens.—UI X-6719, 6720 (loc. 49B, sample 12), 6747, 7025, 7026 (loc. 47A, sample 37). Banastella mediocreforma, new species Plate 22, figures 1-11, Plate 23, figures 1-6; Table 22 Etymology of name.—Named for the moderately in- distinct exterior appearance that characterizes this spe- Cles. 4 Diagnosis. —Zoarium extremely robust, mesh spac- Ing lower-end intermediate, pattern moderately regu- lar; branches robust, wide, thick, straight to sinuous, transversely circular, spacing lower-end intermediate; branches joined at moderately variable intervals by Wide, short dissepiments. Fenestrules large; shape el- liptical to more rarely ovate, moderately variable. Au- tozooecial apertures large, shape ovate, surrounded by well-developed, intermediate-width, complete peri- Stome formed from fusion of nine to 17 small stylets regularly positioned around aperture; three to four (mean of 3.5) apertures per fenestrule. Single narrow, Intermittent keel along middle of obverse branch, atop which are positioned large, stellate, four- to 10-lobed Nodes. Autozooecial chambers large, emplaced in two Tows, except three rows occurring for pronounced dis- tances proximal to sites of branch bifurcation; outline regularly pentagonal near reverse wall, rapidly be- Coming a rectangle to parallelogram in mid and throughout most of chamber, ovate near obverse sur- face, slightly enlarged at distal end. Chamber elongate Parallel to proximal and distal lateral chamber walls. Aperture at distal and slightly abaxial end of chamber, Connected to chamber by short vestibule of moderately Variable length. Superior and inferior hemisepta both absent. Lateral-wall budding-angle highly variable (mean of 22°); reverse-wall budding-angle slightly vari- able (mean of 36°). Table 22 presents statistical criteria used in delim- iting this species. Exterior description.—Zoarium extremely robust, expansion flat to rarely slightly obversely curved, fan- shaped; mesh spacing lower-end intermediate; pro- nounced astogenetic thickening of both obverse and reverse lamellar skeleton; zoarial pattern moderately irregular. Probable mature widths 20 to 35 mm, lengths 30 to 45 mm. Branches robust; wide, slightly variable in width; relatively straight, however frequently with slight in- flections toward sites of dissepiment insertion. Branch spacing lower-end intermediate, distance between ad- jacent branch centers extremely regular. Obverse sur- face texture highly granular, becoming more coarsely granular with astogeny; surface rounded, except single narrow, poorly developed keel; keel intermittent, high- ly anastomosing, extending along branch midline and causing slight positive inflection on obverse surface. Keel becomes covered by lamellar skeleton with as- togeny, completely obscuring keel on obverse surface. Single row of well-developed, large irregularly stellate nodes with four to 10 lobes; nodes elongate proxi- modistally, size moderately regular, shape highly vari- able; nodes projecting from keel, one to two per fe- nestrule length, widely and evenly spaced, commonly opening at or near branch-dissepiment junction; node diameter increases with astogeny, with nodes frequent- ly covered by secondary lamellar skeleton and becom- ing no longer visible on obverse surface. Small to up- per-end small regularly sized stylets variably positioned across obverse surface. Reverse surface texture gran- ular, becoming increasingly granular with astogeny; in- termediate number of closely spaced longitudinal striae atop which are positioned rows of intermediately spaced small, variable-size microstylets. With astogeny lon- gitudinal striae disappear and stylets increase in size, becoming more unevenly positioned across surface; striae visible on reverse exterior of zoarium only at most distal end of zoarium. Autozooecia arranged in two rows, except three rows frequently occurring for pronounced distances proximal to sites of branch bi- furcation; branches exhibit pronounced thickening proximal, thinning distal to sites of branch bifurcation. Heterozooecia absent in all zoarial fragments analyzed. Dissepiments wide, width greater than that of branch, moderately variable; length short, moderately vari- able; connect branches at moderately variable inter- vals. Dissepiments thin medially, exhibit moderate flaring at branch-dissepiment contact; approximately even with both obverse and reverse surfaces. Pro- nounced astogenetic thickening of dissepiments. Ob- verse dissepiment surface lacking ornamentation; re- 80 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 verse dissepiment surface with longitudinal striae oriented perpendicular to branch length, atop which occur rows of small stylets; with astogeny striae cov- ered by lamellar skeleton and stylet size increases along with increasingly irregular placement of stylets across reverse surface; both obverse and reverse dissepiment surface textures granular, becoming increasingly gran- ular with astogeny. Emplacement of dissepiments varying from approximately perpendicular to branch length to a slight angle toward fenestrule. Apertures commonly open on proximal or distal edge, or in mid- dle of dissepiment edge at branch-dissepiment contact; arranged symmetrically or asymmetrically between branches. Fenestrule large; shape primarily elliptical, more rarely irregularly ovate, highly elongate proximodis- tally; irregular in both size and shape; very slight ex- pansion in width and length in obverse-reverse direc- tion. Mean width of fenestrule approximately five-sixths that of branch; slight decrease in fenestrule opening size toward proximal end of zoarium due to astogenetic thickening of lamellar skeleton. Width to length ratio of fenestrule ranging from 1:3 to 1:2, mean width to length ratio approximately 2:5; equally variable width and length of fenestrule. Three to four (mean of 3.5) apertures per fenestrule length; distance between clos- est aperture centers along branch and across branch approximately equal, approximately seven-eighths spacing across fenestrule; constancy of spacing along and across branch approximately equal, much more constant than spacing across fenestrule, which is mod- erately variable. Autozooecial apertures large, shape ovate, elongate proximoabaxially, width to length ratio approximately 3:4; opening most commonly oriented parallel to plane of obverse surface, more rarely at a slight angle toward fenestrule; peristome width intermediate, well-devel- oped, continuous around aperture where present to- ward proximal end of zoarium. Nine to 17 (most com- monly 13) small, well-developed, and irregularly positioned stylets surround aperture; peristome de- velops from fusion of these stylets during astogeny, with stylets present at lateral and distal edge of zoar- ium. Aperture margin exhibiting slight extension into fenestrule, causing slight inflections in fenestrule out- line on obverse surface. Apertures covered toward proximal end of zoarium by astogenetically thickened lamellar skeleton. Large zoarial supports commonly develop as exten- sions of reverse zoarial surface and lateral edge of zoar- ium. Interior description:—Branches a near-perfect to slightly irregular circle in transverse section, moder- ately flaring on obverse side. Branch thick, moderately regular in depth. Table 22. — Summary numerical analysis of Banastella mediocre- forma, n. sp. For explanation of abbreviations of characters (left column), see Table 8b (foldout inside back cover). number of mea- coeffi- sure- standard cient of observed ments mean deviation variation range 1. WB 24 0.4543 0.0854 18.80 0.321-0.725 2. DBC 24 0.8261 0.0934 11.31 0.670-1.042 3. WD 24 0.4711 0.1086 23.05 0.317-0.783 4. LF 24 1.0410 0.2274 21.84 0.879-1.296 5. WF 24 0.3803 0.0944 24.82 0.246-0.625 6. AF 24 3.50 0.51 14.59 3-4 T. AE 24 0.2235 0.0081 3.62 0.209-0.240 8. AW 24 0.1705 0.0081 4.75 0.152-0.190 9. ADB 24 0.3832 0.0340 8.87 0.296-0.463 10. AAB 24 0.3758. -20.0291 7.74 0.321-0.428 11. ABB 24 0.4408 | 0.0763 17.31 0.283-0.558 12. DN 24 0.1446 0.0208 14.38 0.107-0.188 14. SNB 24 0.8788 0.2052 23.35 0.438-1.183 15. WK 24 0.0365 0.0132 36.16 0.020-0.064 16. DSO 24 0.0078 0.0015 19.23 0.005-0.008 17. SSO 24 0.0981 0.0284 28.95 0.048-0.138 18. WP 24 0.0324 0.0037 11.42 0.027-0.040 19. SA 24 12.96 1.83 14.11 9-17 20. SAD 24 0.0141 0.0052 36.88 0.005-0.028 22. RSS 24 0.0126 0.0026 20.63 0.009-0.018 24. SSS 24 0.1209 0.0363 30.02 0.078-0.179 32. TRW 24 0.0057 0.0008 14.04 0.004—0.008 33. TLW 24 0.0061 0.0009 14.75 0.004—0.008 34. FWT 24 0.0937 0.0334 35.65 0.043-0.155 35. RWT 24 0.0750 0.0278 37.07 0.028-0.124 36. CL 24 0.5574 0.0123 2.21 0.535-0.583 37. CD 24 0229500210 9.15 0.193-0.265 38. MAW 24 0.2083 0.0137 6.58 | 0.192-0.250 40. VD 24 0.0926 0.0183 19.76 0.049-0.138 41. RA 24 35.54 5.52 15.54 23-46 42. LA 24 21.54 4.32 20.07 14-32 43. TB 24 0.4964 0.0566 11.40 0.357-0.566 Autozooecial living chamber large, biserially ar- ranged in alternating rows along planar branch axial wall; axial wall straight, slightly sinuous near reverse wall of chamber, curving toward sites of long lateral- wall emplacement. Chamber longest dimension par- allel to proximal and distal lateral chamber walls. Au- tozooecial chamber outline irregularly pentagonal near reverse-wall budding-site; rapidly becoming a rectan- gle to parallelogram in the mid and throughout most of chamber; ovate near obverse surface, slightly en- larged at distal end of chamber; chamber shape highly regular. Aperture positioned at distal-abaxial end of chamber, connected to chamber by short vestibule of moderately variable length. Ratio of autozooecial chamber width to depth approximately 9:10; depth to length ratio approximately 2:5; length more constant than width or depth, however all regular. Superior and 'inferior hemisepta both absent. Autozooecial chamber diverges laterally from middle of branch at highly vari- MISSISSIPPIAN BRYOZOANS: SNYDER 81 able angle (mean of 22°); from reverse wall at a slightly variable angle (mean of 36°). Three-dimensionally reconstructed chamber form a Slightly irregular rectangular box; long dimension as viewed from lateral edge branch; depth, viewed from distal end of branch, slightly greater than width, viewed from obverse surface. Internal granular layer thickness intermediate; con- tinuous with obverse keel, nodes, stylets, peristome, and apertural stylets; reverse longitudinal striae and Microstylets atop these striae; across dissepiment and in the middle of zoarial supports. Outer lamellar layer thick, exhibiting pronounced astogenetic thickening on both obverse and reverse exterior surfaces, most pro- Nounced at proximal end of zoarium. Remarks.—Banastella mediocreforma is distin- guished from the closely similar species, B. limitaris (Ulrich, 1890), by having lower-end intermediate mesh Spacing rather than intermediate spacing, single as Compared to multiple keels, autozooecial chamber Slightly shorter in length and smaller in volume, fewer apertural stylets, and a smaller reverse-wall budding- angle, one of the lowest for any of the species of Ban- astella. A highly granular zoarial exterior is also highly Characteristic of B. mediocreforma. Material studied. — Twenty-eight exterior fragments; four sectioned specimens; largest zoarial fragment 20x25 mm (width to length). The highly robust nature Ofthis species results in the presence of nearly complete colonies that exhibit little secondary skeletal alteration. Occurrence.— Banastella mediocreforma is relative- ly rare, and is present at the Valmeyer and St. Louis localities. It ranges throughout the Warsaw, and is pres- ent in both limestones and shales. Holotype. — UI X-6717 (loc. 49B, sample 12). Paratypes. — UI X-6916, 6917, 6746 (loc. 49B, sam- ples 120, 12, 13). Banastella limitaris (Ulrich, 1890) Plate 24, figures 1-10, Plate 25, figures 1-8; Table 23 Fenestella limitaris Ulrich, 1890, p. 538, pl. 49, figs. 4, 4a [Keokuk Group: Bentonsport and Keokuk, Iowa]; Keyes, 1894, p. 23 [Keo- kuk Limestone: Keokuk, Iowa]. Diagnosis. —Zoarium robustness intermediate, mesh Spacing intermediate, pattern regular; branches mod- *rately robust, wide, depth thick; straight to sinuous, frequently broadly curved at lateral zoarial edge; trans- Versely irregularly ovate to elliptical, spacing close; Tanches joined at regular intervals by lower-end in- termediate width, short to lower-end intermediate length dissepiments. Fenestrules large; shape elliptical to Ovate, variable. Autozooecial apertures large, shape vate, elongate proximoabaxially; surrounded by well- €veloped, intermediate-width, complete peristome formed from fusion of 16 to 26 small stylets regularly positioned around aperture; three to four (mean of 3.67) apertures per fenestrule. Single to multiple in- termediate-width intermittent keel(s), straight to anas- tomosing around autozooecial apertures along middle of obverse branch, atop which are positioned large, stellate nodes. Autozooecial chambers large, emplaced in two rows, except third row at sites of branch bifur- caion or three rows for pronounced distances proximal to sites of branch bifurcation; outline irregularly ovate to rounded triangle near reverse wall, rapidly becoming irregularly pentagonal immediately obverse from re- verse wall, a rectangle to parallelogram throughout mid and most of chamber length, elliptical to ovate near obverse surface, slightly enlarged at distal end of cham- ber. Chamber longest dimension parallel to proximal and distal lateral chamber walls. Aperture at distal- abaxial end of chamber, connected to chamber by long vestibule of variable length. Superior and inferior hemi- septa both absent. Lateral-wall budding-angle variable (mean of 21°); reverse-wall budding-angle constant (mean of 47°). Table 23 presents statistical criteria used in delim- iting this species. Exterior description.—Zoarium robustness inter- mediate, expansion flat, flaring at distal end, fan-shaped; mesh spacing intermediate; slight to moderate asto- genetic thickening of both obverse and reverse lamellar skeleton; zoarial pattern regular. Probable mature widths 40 to 50 mm; lengths 30 to 45 mm. Branches moderately robust; wide, slightly variable in width; ranging from straight to sinuous, with in- flections toward sites of dissepiment insertion; lateral branches frequently broadly curved toward edge of zoarium. Branch spacing close, distance between ad- jacent branch centers moderately regular. Obverse sur- face texture slightly granular; surface profile angular with single to multiple intermediate-width, well-de- veloped keel(s); keel(s) intermittent, varying from straight to moderately anastomosing, curving around autozooecial apertures; keel(s) extending along branch midline, causing moderate positive inflection(s) on ob- verse surface. Slight thickening of keel(s) occurring with astogeny, due to covering of keel(s) by lamellar skel- eton; near proximal end of zoarium partially covering adaxial edge of aperture. Single row of extremely well- developed, large elliptical to slightly stellate, proxi- modistally elongate nodes; node size moderately reg- ular, shape variable; nodes projecting from middle of keel; most commonly one, rarely two nodes per fe- nestrule length, widely, evenly spaced, most frequently located at or near branch-dissepiment junction; node diameter increases with astogeny. Extremely small sty- lets in rows along middle of keel(s) positioned between nodes. Reverse surface texture highly granular, becom- 82 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 ing more coarsely granular with astogeny; bearing an intermediate number of closely spaced longitudinal striae atop which are positioned rows of intermediate- size, closely spaced, variable microstylets. With asto- geny longitudinal striae disappear and microstylets be- come larger, more scattered across surface. Autozooe- cia arranged in two rows, except third row at site of branch bifurcation or three rows extending for pro- nounced distances proximal to branch bifurcation, branches exhibiting pronounced thickening proximal, thinning distal to sites of branch bifurcation. Enlarged apertural openings, possibly representing ovicells, in- frequently occurring at most proximal end of zoarium. Dissepiments of lower-end intermediate width, ap- proximately three-fifths branch width, width highly variable; short to lower-end intermediate in length, moderately constant; connect branches at regular in- tervals. Dissepiments exhibit pronounced medial thin- ning, flaring at branch-dissepiment contact; moder- ately recessed from obverse, approximately even with reverse surface. Slight to moderate astogenetic thick- ening of dissepiments. Obverse dissepiment surface with two to five barlike longitudinal striae located across dissepiment surface, oriented perpendicular to branch length, extremely small stylets positioned atop striae; reverse dissepiment surface with less pronounced lon- gitudinal striae across dissepiment surface, oriented perpendicular to branch length, small to intermediate- size microstylets project from these striae; with asto- geny reverse striae disappear, microstylets become larger, more scattered across dissepiment surface; ob- verse dissepiment texture slightly granular, reverse sur- face highly granular. Emplacement of dissepiments most commonly at a slight angle from perpendicular to branch length, more rarely emplaced perpendicular thereto. Apertures commonly open on proximal or dis- tal edge, or in middle of dissepiment at branch-dis- sepiment contact; predominantly arranged symmetri- cally, less commonly arranged asymmetrically between branches. Fenestrules large; shape elliptical to ovate, elongate proximodistally; moderately regular in size, variable in shape; expanding slightly in width and length in obverse-reverse direction. Mean width of fenestrule approximately equal to branch width on obverse, slightly greater on reverse surface; very slight decrease in size of fenestrule opening toward proximal end of zoarium due to astogenetic thickening of lamellar skel- eton. Ratio of mean fenestrule width to length ap- proximately 1:3, moderately constant; length of fenes- trule more constant than width. Three to four (mean of 3.67) apertures per fenestrule length; distance be- tween closest aperture centers across branch nine-tenths of that along branch; aperture center spacing along branch four-fifths of that across fenestrule; spacing along and across branch and across fenestrule all variable. Table 23.—Summary numerical analysis of Banastella limitaris (Ulrich, 1890). For explanation of abbreviations of characters (left column), see Table 8b (foldout inside back cover). number of mea- sure- standard cient of observed ments mean deviation variation range 1. WB 24 0.4851 0.0854 17.60 0.369-0.619 2. DBC 24 0.7810 0.1248 15.98 0.581-1.038 3. WD 24 0.2898 0.0749 25.86 0.213-0.456 4. LF 24 1.2220 0.1598 13.08 0.981-1.500 5. WF 24 0.4420 0.0851 19.25 0.350-0.625 6. AF 24 3.67 0.49 13.43 3-4 7. AL 24 0.2040 0.0184 9.02 0.178-0.240 8. AW 24 0.1615 0.0192 11.89 0.135-0.193 9. ADB 24 0.3979 0.0668 16.79 0.331-0.550 10. AAB 24 0.3653 0.0496 13.58 0.265-0.455 11. ABB 24 0.4908 0.1009 20.56 0.350-0.700 12. DN 24 0.1338 0.0297 22.20 0.098-0.170 14. SNB 24 1.3820 0.2100 15.20 12100217825 15. WK 24 0.0745 0.0248 33.29 0.043-0.130 16. DSO 24 0.0145 0.0035 24.14 0.011-0.031 17. SSO 24 0.0348 0.0110 31.61 0.029-0.086 18. WP 24 0.0254 0.0045 17.72 0.018-0.033 19. SA 24 20529 2.90 14.30 16-26 20. SAD 24 0.0162 0.0032 19.75 0.013-0.023 22. RSS 24 0.0182 0.0050 27.47 0.011-0.031 24. SSS 24 0.0515 0.0131 25.44 0.030-0.075 32. TRW 24 0.0129 0.0033 25.58 0.008-0.020 33. TLW 24 0.0188 0.0038 20.21 0.012-0.025 34. FWT 24 0.0960 0.0305 31.77 0.037-0.147 35. RWT 24 0.0984 0.0491 49.90 0.023-0.180 36. CL 24 009157 10:0377 5.45 0.600-0.750 37D) 24 0.1950 0.0187 9.59 0.160-0.225 38. MAW 24 012055... 00253... 12:31) . .0.175-0:230 40. VD 24 0.1236 0.0304 24.60 0.074-0.181 41. RA 24 47.15 4.04 8.56 40-54 42. LA 24 gi 3.59 16.95 15-28 43. TB 24 0.5603 0.0883 15.76 0.425-0.718 Autozooecial apertures large, shape ovate, elongate proximoabaxially, width to length ratio 4:5, shape moderately uniform; opening oriented parallel to plane of obverse surface, more rarely at slight angle toward fenestrule; intermediate-width, well-developed peri- stome present, complete, continuous around aperture, best developed toward proximal end of zoarium. Six- teen to 26 (most commonly 20) small, variable-size stylets, well-developed and regularly positioned around aperture; peristome develops from fusion of these sty- lets during astogeny, with stylets most common at lat- eral and distal edges of zoarium. Slight to moderate extension of aperture margin into fenestrule, causing inflections in fenestrule outline on obverse surface. Centrally thickened terminal diaphragm rarely present, capping apertural openings in late astogeny toward proximal end of zoarium. Zoarial supports occurring infrequently, develop as extensions of reverse zoarial surface and from lateral edge of zoarium. MISSISSIPPIAN BRYOZOANS: SNYDER 83 Interior description.—Branches irregularly ovate to irregularly elliptical in transverse section, most com- monly flaring on obverse surface, elongate either in obverse-reverse direction or parallel to zoarial surface; branches thick, moderately variable in depth. Autozooecial living chambers large, biserially ar- ranged in alternating rows along planar branch axial wall; axial wall highly sinuous near reverse wall, curv- ing toward sites of lateral wall emplacment connecting With intermediate-length lateral walls, becoming Straight toward obverse surface. Chamber longest di- mension parallel to proximal and distal lateral cham- ber walls. Autozooecial chamber outline irregularly Ovate to rounded triangular near reverse-wall budding- Site; rapidly becoming irregularly pentagonal imme- diately toward obverse surface from reverse wall; be- coming a rectangle to parallelogram through mid Chamber and most of chamber length; elliptical to ovate, Slightly enlarged at distal end of chamber near obverse Surface; chamber shape moderately regular. Aperture Positioned at distal-abaxial end of chamber, connected to chamber by long, well-developed vestibule of vari- able length. Autozooecial chamber width approxi- Mately equal to depth; depth to length ratio approxi- mately 3:10; length more constant than depth or width, all moderately constant. Superior and inferior hemi- Septa both absent. Autozooecial chambers diverge lat- erally from middle of branch at variable angle (mean pa 21°); from reverse wall at a constant angle (mean of TS); Three-dimensionally reconstructed chamber form an irregular rectangular or parallelogram-shaped box; long dimension as viewed from lateral edge of branch; approximately equidimensional in depth and width, as viewed from the distal end of branch and obverse Surface, respectively. Internal granular layer thick, well-developed; con- tinuous with obverse nodes, stylets, keel, apertural sty- lets, and peristome; reverse longitudinal striae and mi- Crostylets atop these striae; across dissepiments and in the middle of zoarial supports. Outer lamellar layer of Intermediate thickness, exhibiting slight astogenetic thickening on both obverse and reverse exterior zoarial Surfaces. Remarks.— The intermittent, “faint” nature of the keel was observed by Ulrich (1890, p. 538), and is Moderately characteristic of B. limitaris. Ulrich com- Pared this species to Fenestella rudis (Ulrich, 1890), indicating the two species to be phylogenetically closely related. Interior analysis indicates pronounced differ- ences in chamber shape between. these two species, With B. limitaris having a much larger chamber that is elongate parallel to chamber lateral walls and C. rudis aving a smaller chamber elongate parallel to the re- Verse wall. Many characteristics are common to B. limitaris and the other species of the genus, B. guensburgi, n. sp., B. cingulata (Ulrich, 1890), and B. mediocreforma, n. sp. These include fusion of apertural stylets to form the peristome, autozooecial chamber shape and place- ment, and nodal development. Such similarities in- dicate probable close phylogenetic association among these species. B. limitaris is distinguished from the closest other species of Banastella, B. mediocreforma, by a slightly longer autozooecial chamber, multiple rather than sin- gle keel, greater reverse-wall chamber budding-angle, and greater number of apertural stylets. Exquisite preservation of specimens of this species makes them some of the most visually elegant to be found in the Warsaw. Material studied.— Twelve exterior fragments; three sectioned specimens; largest zoarial fragment 28 x 30 mm (width to length). The robust nature of this species results in its frequent excellent preservation. Occurrence. — Banastella limitaris is restricted to the Upper Keokuk and Lower Warsaw in the northern part of the study area near Warsaw, Illinois and Keokuk, Iowa; it ranges as far south as Mt. Sterling, Illinois. It is rare, found most frequently in shaly facies. Lectotype of F. limitaris (herein designated)—ISGS ASM) 2770. Hypotypes.—UI X-7015, 7027 (loc. 10, sample 31). Banastella biseriata (Ulrich, 1890) Plate 26, figures 1—10, Plate 27, figure 1; Table 24 Polypora biseriata Ulrich, 1890, p. 592, pl. 60, figs. 4-4b [Warsaw Beds: Monroe County, Illinois; Warsaw, Illinois. ?St. Louis Lime- stone: ?Barrett’s Station, Missouri]; Keyes, 1894, p. 2a [St. Louis Limestone: Barrett’s Station, Missouri]; Trizna, 1958, p. 166, pl. 46, figs. 2-4. Diagnosis.—Zoarium robustness intermediate, mesh spacing close, pattern moderately regular; branches moderately robust, depth thin, wide; branches straight to broadly curved at lateral zoarial edge; transversely circular to ovate, spacing close; branches joined at fair- ly regular intervals by thin, short dissepiments. Fe- nestrule size intermediate, shape irregularly elliptical to rarely irregularly ovate, fairly regular. Autozooecial apertures large, shape ovate, surrounded by interme- diate-width, well-developed complete peristome; two to four (most commonly three) apertures per fenes- trule. Single intermediate-width intermittent keel anastomosing along branch midline and curving around apertures; lower-end intermediate size slightly stellate nodes positioned atop keel. Autozooecial chamber size intermediate, chambers emplaced in two rows, except three rows occurring for moderately to extremely pro- nounced distances proximal to sites of branch bifur- cation; outline irregularly triangular to pentagonal near reverse wall, rapidly becoming an irregular rectangle to parallelogram in mid and throughout most of cham- 84 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 ber length, irregularly ovate to elliptical near obverse surface, slightly enlarged at distal end. Chamber long- est dimension parallel to proximal and distal lateral chamber walls. Aperture positioned at distal or distal- abaxial end of chamber, connected to chamber by short vestibule of variable length. Short superior hemisep- tum present; inferior hemiseptum absent. Lateral-wall budding-angle variable (mean of 22°), reverse-wall budding-angle constant (mean of 39°). Table 24 presents statistical criteria used in delim- iting this species. Exterior description.—Zoarium robustness inter- mediate, expansion most commonly flat, less frequent- ly obversely or reversely curved, fan-shaped; mesh spacing close; slight astogenetic thickening of both ob- verse and reverse lamellar skeleton; zoarial pattern moderately regular. Probable mature widths 18 to 25 mm; lengths 30 to 40 mm. Branches moderately robust; wide, highly variable in width; straight, except lateral branches broadly curved toward edge of zoarium. Branch spacing close, distance between adjacent branch centers moderately regular. Obverse surface texture smooth; surface rounded except single intermediate-width, poorly de- veloped keel; keel intermittent, anastomosing, extend- ing along branch midline and curving around auto- zooecial apertures, causing slight positive inflection in obverse surface profile. Keel covered during astoge- netic thickening of lamellar skeleton, exhibiting slight increase in width; obverse branch surface becoming slightly granular with astogeny. Single row of well-de- veloped, lower-end intermediate size, slightly stellate nodes; node size and shape regular; nodes anastomos- ing, project from middle of keel; two to four per fe- nestrule length, most commonly one per pair of ap- ertures across branch, intermediately unevenly spaced; with astogeny, node diameter increases and nodes fre- quently become covered by thickened secondary la- mellar skeleton of keel. Reverse surface texture mod- erately smooth, becoming slightly granular with astogeny; bearing numerous rows of closely spaced lon- gitudinal striae atop which are positioned rows of small, closely spaced,. variable-size microstylets. With asto- geny striae become more pronounced and microstylet diameters increase. Autozooecia arranged in two rows, except three rows frequently occurring for moderate to extremely pronounced distances proximal to sites of branch bifurcation; branches exhibit pronounced thickening proximal, thinning distal to sites of branch bifurcation. Heterozooecia not found in any zoaria an- alyzed. Dissepiments of thin width, slightly less than half branch width, width moderately variable; short, mod- erately variable in length; connect branches at fairly regular intervals. Dissepiments thin medially, flaring Table 24.—Summary numerical analysis of Banastella biseriata (Ulrich, 1890). For explanation of abbreviations of characters (left column), see Table 8b (foldout inside back cover). number of mea- coeffi- sure- standard cientof observed ments mean deviation variation range 1. WB 24 0.4823 0.1293 26.81 0.300-0.738 2. DBC 24 0.6859 0.1033 15.06 0.525-0.880 3. WD 24 0.2128 0.0489 22.98 0.144-0.312 4. LF 24 0.7468 0.0874 11.70 0.575-0.831 5. WF 24 0.2644 0.0638 24.13 0.175-0.356 6. AF 24 3.00 0.60 20.10 2—4 7. AL 24 0.1610 0.0093 5.78 | 0.144—0.178 8. AW 24 0.1338 0.0136 10.32 0.116-0.156 9. ADB 24 0.3239 0.0439 13.55 0.264-0.390 10. AAB 24 0.2923 0.0281 9.61 0.234-0.328 11. ABB 24 0.3869 0.0737 19.05 0.238-0.500 12. DN 24 0.0729 0.0082 11.25 0.058-0.088 14. SNB 24 0.3494 0.0944 27.02 0.148-0.508 15. WK 24 0.0617 0.0091 14.75 0.048-0.080 18. WP 24 0.0435 0.0068 15.63 0.034-0.056 22. RSS 24 0.0099 0.0021 21.21 0.007-0.014 32. TRW 24 0.0103 0.0016 15.53 0.008-0.014 33. TLW 24 0.0093 0.0018 19.35 0.007-0.012 34. FWT 24 0.0396 0.0214 54.04 0.018-0.086 35. RWT 24 0.0302 0.0166 54.97 0.011-0.061 36. CL 24 0.3293 0.0102 3.10 0.311-0.347 37. CD 24 0.2102 0.0136 16.47 0.189-0.235 38. MAW 24 0.1604 0.0120 7.18 0.139-0.187 40. VD 24 0.0615 0.0132 21.46 0.042-0.094 41. RA 24 39.0 3.01 eles 34-44 42. LA 24 22.00 SI 16.90 14-27 43. TB 24 0.2917 0.0614 21.05 0.204-0.395 at branch-dissepiment contact; both obverse and re- verse dissepiment surfaces recessed from respective branch surfaces. Slight astogenetic thickening of dis- sepiments. Obverse dissepiment surface with one to four rows of longitudinal striae oriented perpendicular to branch length; reverse dissepiment surface with nu- merous rows of longitudinal striae oriented perpen- dicular to branch length, atop which occur small mi- crostylets similar in all respects to those found on branch reverse surface; both obverse and reverse dissepiment surfaces smooth, becoming slightly granular with as- togeny. Emplacement of dissepiments approximately perpendicular to branch length. Apertures open on proximal or distal edge, or in middle of dissepiment edge at branch-dissepiment contact; most commonly arranged asymmetrically between branches, more rare- ly arranged symmetrically. Fenestrule size intermediate; shape irregularly ellip- tical to rarely irregularly ovate, moderately elongate proximodistally; size and shape both fairly regular; ex- panding in width and length in obverse-reverse direc- tion. Mean width of fenestrule slightly greater than half branch width on obverse surface, slightly greater than half branch width on reverse; fenestrule opening de- MISSISSIPPIAN BRYOZOANS: SNYDER 85 creasing in size toward proximal end of zoarium due to astogenetic thickening of lamellar skeleton. Mean width to length ratio approximately 1:3. Two to four (most commonly three) apertures per fenestrule length; distance between closest aperture centers along branch Slightly greater than across branch, ratio approximately 10:9, spacing across branch appreciably less than that across fenestrule, ratio of approximately 7:10; spacing along and across branch fairly constant, much more regular than spacing across fenestrule, which is highly variable. Autozooecial apertures large; shape ovate, elongate Proximodistally to proximoabaxially, width to length ratio approximately 4:5, size and shape highly uniform; Opening most commonly oriented parallel to plane of Obverse surface, less frequently at slight angle toward fenestrule; intermediate-width, well-developed com- plete peristome present; peristome width increasing with astogeny toward proximal end of zoarium. Ap- €rture margin extends into fenestrule, causing pro- nounced inflection in fenestrule outline on obverse sur- face, Centrally thickened terminal diaphragms present, Occurring toward proximal end of zoarium. Zoarial supports rare, develop as extensions of re- Verse zoarial surface. Interior description. — Branches circular to ovate in transverse section, slightly flaring on obverse side, elongate parallel to zoarial surface. Branches shallow, Moderately variable in depth. Autozooecial living chamber size intermediate, chambers biserially arranged in alternating rows along Planar branch axial wall; axial wall exhibiting pro- nounced inflections toward and connecting with inter- Mediate-length lateral walls near reverse wall, becom- mg straight in mid and shallow tangential sections. Chamber maximum dimension parallel to proximal and distal lateral chamber walls. Autozooecial cham- ber outline irregularly triangular to pentagonal near reverse-wall budding-site; rapidly becoming an irreg- ular rectangle to parallelogram in middle and through- Out most of chamber length; irregularly ovate to ellip- tical near obverse surface, with slightly enlarged distal €nd of chamber; chamber shape highly regular. Ap- €tture positioned at distal or distal-abaxial end of Chamber, connected to chamber by short vestibule of Variable length. Ratio of autozooecial chamber width to depth approximately 3:4; depth to length ratio ap- Proximately 5:8; length slightly more constant than Width or depth, all dimensions highly constant. Short Superior hemiseptum present at proximal apertural edge; inferior hemiseptum absent. Autozooecial cham- er diverges laterally from middle of branch at a vari- able angle (mean of 22°); from reverse wall at constant angle (mean of 39°). Three-dimensionally reconstructed chamber form an irregular rectangular box, long dimension as viewed from lateral edge of branch; depth, viewed from distal end of branch, slightly greater than width, viewed from obverse surface. Internal granular skeletal layer thin, continuous with obverse nodes, keel, and peristome; reverse longitu- dinal striae and microstylets atop these striae; across dissepiments and in the middle of zoarial supports. Outer lamellar skeleton thin, exhibiting slight astoge- netic thickening. Remarks.—This species was originally assigned to Polypora McCoy, 1844 by Ulrich (1890, p. 592) based on the presence of three rows of autozooecia “at a point 2 or 3 mm below branch divisions,” and appearance similar to that of P. varsoviensis Prout, 1858a, although the latter species typically has “one row of cells more to the branch, and larger fenestrules.” (Ulrich, 1890, p. 593) Ulrich’s inclusion in Polypora of a species that has two rows of autozooecia across the branch — tra- ditionally the standard criterion for placement in the fenestellids — seems to indicate that Ulrich was aware of the problem of number of apertural rows in fenes- tellid taxonomy. Banastella, a genus exhibiting characters of both the traditional fenestellids (i.e., two rows of autozooecia across branch) and polyporids (i.e., long autozooecial chambers having small reverse-wall budding-angles and three rows of autozooecia proximal to branch bifur- cation), apparently lies between Fenestella Lonsdale, 1839 and Polypora. ; Banastella biseriata is herein assigned: to Banastella because of chamber shape, low reverse-wall budding- angle, large aperture size, and presence of two rows of autozooecia along branch with three rows present for moderate to prolonged distances proximal to sites of branch bifurcation, Separation of B. biseriata from oth- er species of the genus is based on smaller chamber size, close mesh spacing, and lack of apertural stylets. Material studied. — Eighteen exterior fragments, three sectioned specimens; largest zoarial fragment 8x23 mm (width to length). Little secondary skeletal alter- ation of this species is evident. The thin nature of the internal granular skeleton results in frequent mechan- ical crushing of this species, particularly common in shales. Occurrence.— Banastella biseriata is rare, and is re- stricted to the Lower Warsaw in the southern portion of the outcrop area near St. Louis, Missouri, and Val- meyer, Illinois. Syntypes. — ISGS(ISM) 2805 (10 fragments). Figured and/or measured specimens.—UI X-6742, 6743, 6915 (loc. 11, sample 55). 86 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 Banastella delicata, new species Plate 27, figures 2-10, Plate 28, figures 1-5; Table 25 Etymology of name.—Named for the characteristic delicate growth habit. Diagnosis.—Zoarium delicate, mesh spacing highly open, pattern highly irregular; branches moderately delicate, width intermediate, thickness medium; straight, sharply curved to broadly curved at zoarial edge in trace; transversely circular, spacing wide; branches joined at moderately variable intervals by thin, long dissepiments. Fenestrules extremely large; shape regularly to irregularly rectangular, variable. Au- tozooecial apertures large, shape ovate to rarely cir- cular, surrounded by thin, well-developed complete peristome formed from fusion of 13 to 17 small stylets regularly positioned around aperture; five to nine (most commonly seven) apertures per fenestrule. Single in- termediate-width continuous keel along middle of ob- verse branch, atop which are positioned large irregu- larly stellate nodes. Autozooecial chambers large, emplaced in two rows, except third row at sites of branch bifurcation; outline irregularly pentagonal near reverse wall, rapidly becoming an irregular rectangle to parallelogram in mid and throughout most of cham- ber, irregularly elliptical near obverse surface, slightly enlarged at distal end. Chamber longest dimension par- alleling proximodistal direction for proximal two-thirds of chamber, most distal third of chamber paralleling proximal and distal chamber lateral walls. Aperture at distal and slightly abaxial end of chamber, connected to chamber by short vestibule of variable length. Short superior hemiseptum present; inferior hemiseptum ab- sent. Lateral-wall budding-angle highly variable (mean of 21°); reverse-wall budding-angle variable (mean of 23-0 Table 25 presents statistical criteria used in delim- iting this species. Exterior description. — Zoarium delicate, expansion flat to slightly sinuous, lateral branches broadly curved toward edge of zoarium, fan-shaped; mesh highly open; slight astogenetic thickening of both obverse and re- verse lamellar skeleton; zoarial pattern highly irregular. Probable matüre widths 20 to 40 mm, lengths 30 to 60 mm. Branches moderately delicate; width intermediate, moderately consistent; straight or slightly curved, sharply curved distal to sites of branch bifurcation, lateral branches commonly broadly curved toward edge of zoarium. Branch spacing wide, distance between adjacent branch centers moderately regular. Obverse surface texture smooth, becoming slightly granular with astogeny; surface well rounded, except for single in- termediate-width, extremely well-developed keel; keel continuous, straight to slightly anastomosing, curving around autozooecial apertures, extending along branch Table 25.—Summary numerical analysis of Banastella delicata, n. sp. For explanation of abbreviations of characters (left column), see Table 8b (foldout inside back cover). number of mea- coeffi- sure- standard cient of observed ments mean deviation variation range 1. WB 24 0.3411 0.0480 14.07 0.250-0.438 2. DBC 24 0.9005 0.1567 17.40 0.625-1.213 3. WD 24 0.1452 0.0259 17.84 0.105-0.200 4. LF 24 1.3116. 02578 1423 413752225 5. WF 24 0.5155 0.1308 25.37 0.325-0.750 6. AF 24 6.96 1.16 16.67 5-9 7. AL 24 0.1982 0.0232 11.71 0.165—0.225 8. AW 24 0.1578 0.0153 9.70 0.130-0.195 9. ADB 24 0.4364 0.00352 8.07 0.388-0.525 10. AAB 24 0.3468 0.0270 7.79 0.300—0.400 11. ABB 24 0.5813 0.1051 18.08 0.231-0.919 12. DN 24 0.1555 0.0374 24.05 0.100-0.250 13. DND 24 0.0228 0.0064 27.93 0.013-0.031 14. SNB 24 1.1900 0.2009 16.88 0.813-1.625 15. WK 24 0.0583 0.0152 26.07 0.038-0.084 16. DSO 24 0.0092 0.0027 29.35 0.005-0.014 17. SSO 24 0.1055 0.0246 13.32 0.071-0.152 18. WP 24 0.0156 0.0045 28.85 0.010-0.025 19. SA 24 Lo 241 0.97 6.41 13-17 20. SAD 24 0.0107 0.0039 36.45 0.004-0.019 22. RSS 24 0.0150 0.0043 28.67 0.011-0.028 24. SSS 24 0.0314 0.0125 39.81 0.020-0.069 32. TRW 24 0.0045 0.0008 17.78 0.004-0.006 33. TLW 24 0.0047 0.0009 19.15 0.004-0.006 34. FWT 24 0.0073 0.0217 38.07 0.050-0.114 35. RWT 24 0.0602 0.0201 33.39 0.023-0.089 36. CL 24 0.6389 0.0351 5.49 0.595-0.720 $7 6D 24 0.1699 0.0230 13.54 0.138-0.225 38. MAW 24 0.1544 0.0162 10.49 0.130-0.200 40. VD 24 0.0607 0.0103 16.97 0.040-0.075 41. RA 24 pists) Syd 16.05 18-30 42. LA 24 20.92 4.44 2.1623 12-27 43. TB 24 0.3564 0.0563 15.80 0.257-0.436 midline and causing slight positive inflection on ob- verse surface. Keel thickens slightly with astogeny due to partial covering by lamellar skeleton, most common toward proximal end of zoarium. Single row of inter- mediately developed, large, irregularly stellate nodes present; size and shape fairly regular; nodes project from middle of keel; one to two per fenestrule length, widely, moderately evenly spaced, most frequently lo- cated at or near branch-dissepiment junction; with as- togeny, node diameters exhibit slight increase due to partial covering by lamellar skeleton. Small, variable- size stylets positioned along obverse branch surface, most commonly occurring atop or on lateral edge of keel. Reverse surface texture finely granular, coarsen- ing with astogeny; bearing numerous rows of closely spaced longitudinal striae atop which are positioned rows of very small, closely spaced, variable-size mi- crostylets. With astogeny, longitudinal striae become covered by lamellar skeleton and disappear, micro- stylets increase in size, become unevenly positioned MISSISSIPPIAN BRYOZOANS: SNYDER 87 across branch surface. Autozooecia arranged in two rows, except third row at sites of branch bifurcation where middle autozooecium is evidently shared by both branches; branches with little or no thickening proxi- mal or thinning distal to sites of branch bifurcation. Heterozooecia not present on any zoarial fragments observed. Dissepiments of thin width, approximately two-fifths Width of branch, width fairly regular; long, variable in length; connect branches at moderately variable inter- vals. Dissepiments barlike, exhibit slight flaring at branch-dissepiment contact; slightly recessed from both Obverse and reverse surfaces. Little or slight astoge- netic thickening of dissepiment. Obverse dissepiment Surface with one to three longitudinal striae across dis- Sepiment perpendicular to direction of branch length; median ridge pronounced, forming elongate node-like Projection along entire dissepiment length, continuous With peristome or apertural stylets where aperture oc- Curs at middle edge of dissepiment; reverse dissepi- ment surface with longitudinal striae oriented perpen- dicular to branch length, atop which occur rows of Small microstylets; striae covered by lamellar skeleton and microstylets increase in size with astogeny; obverse dissepiment surface texturally smooth, reverse texture finely granular, coarsening with astogeny. Emplace- Ment of dissepiments oriented approximately perpen- dicular to branch length, although deviation from per- Pendicular by angles of up to 15° is observed. Apertures Open on proximal or distal edge or in middle of dis- Sepiment edge at branch-dissepiment contact; ar- Tanged symmetrically or asymmetrically between branches. Fenestrules extremely large; shape regularly to ir- Tegularly rectangular, highly elongate proximodistally, regular in length, variable in width; variable in shape; exhibiting little or no expansion in width or length in Obverse-reverse direction. Width of fenestrule vari- able, ranging from equal to 2.5 times branch width; Slight decrease in size of fenestrule opening toward Proximal end of zoarium due to astogenetic thickening Of lamellar skeleton. Width to length ratio of fenestrule Tanging from 1:2 to 1:7, highly variable, mean ratio 1:3,5; length of fenestrule much more constant than width. Five to nine (most commonly seven) apertures Per fenestrule length; distance between closest aperture Centers along branch five-fourths that of spacing across branch; spacing across branch three-fifths that across fenestrule; spacing along and across branch constant, Spacing across fenestrule highly variable. Autozooecial apertures large, shape ovate, elongate Proximal to slightly abaxially, to rarely circular; width to length ratio approximately 4:5, size and shape mod- Crately uniform; opening most commonly oriented Parallel to plane of obverse surface, more rarely at slight angle toward fenestrule; thin, well-developed peristome present, continuous around aperture where present at proximal end of zoarium. Thirteen to 17 (most commonly 15) small, variable-size well-devel- oped and moderately regularly positioned stylets sur- round aperture; peristome develops from fusion of these stylets during astogeny, with stylets most commonly occurring at lateral and distal edges of zoarium. Ap- erture margin extends into fenestrule, causing slight inflection in fenestrule outline on obverse surface. Cen- trally thickened terminal diaphragms present, most common at proximal end of zoarium. Zoarial supports lacking on all zoarial fragments an- alyzed. Interior description.— Branches a nearly perfect cir- cle in transverse section, slightly flaring on obverse side. Branches medium, slightly variable in thickness. Autozooecial living chambers large, biserially ar- ranged in alternating rows along planar branch axial wall; axial wall straight throughout most of chamber except near reverse wall, where axial wall exhibits in- flections toward and connects with relatively long lat- eral walls. Chamber maximum dimension parallel to proximodistal direction of branch growth paralleling reverse wall from proximal end of chamber to near distal end; curving obversely two-thirds of distance up the chamber and becoming parallel to proximal and distal lateral chamber walls. Autozooecial chamber outline irregularly pentagonal near reverse-wall bud- ding-site; rapidly becoming an irregular rectangle to parallelogram, with distalmost edge of parallelogram occurring at outer branch edge, in the mid and through- out most of chamber; irregularly elliptical near obverse surface, slightly enlarged at distal end of chamber; chamber shape moderately regular. Aperture posi- tioned at distal and slightly abaxial end of chamber, connected to chamber by short vestibule of moderately variable length. Ratio of autozooecial chamber width to depth approximately 9:10; depth to length ratio ap- proximately 1:4; length much more constant than width or depth, which are moderately constant. Short supe- rior hemiseptum present at vestibular proximal edge, inferior hemiseptum absent. Autozooecial chambers diverge laterally from middle of branch at a highly variable angle (mean of 21°); from reverse wall at a variable angle (mean of 22°). Three-dimensionally reconstructed chamber form a slightly irregular rectangular box; long dimension as viewed from lateral edge of branch, approximately equidimensional in depth and width, as viewed from distal end of branch and obverse surface, respectively. Internal granular layer thin, continuous with obverse nodes, stylets, keel, apertural stylets, and peristome; reverse longitudinal striae and microstylets atop these striae; and across dissepiments. Outer lamellar layer moderately thin, exhibiting slight astogenetic thick- ening toward proximal end of zoarium. Remarks.—In many respects, the exterior of B. de- licata closely resembles that of Fenestella filistriata Ul- rich, 1890, described from the Burlington Limestone near Burlington, Iowa. The two species can be readily separated on the basis of exterior analysis (no interior views of F. filistriata were available) by the more del- icate nature of branches and zoaria in B. delicata, its larger apertures ringed by apertural stylets, and the presence of a more pronounced keel from which stel- late nodes project. Fenestella regalis Ulrich, 1890, from materials collected at Kings Mountain, Kentucky, also exhibits many characters in common with B. delicata, but can be readily distinguished by its much wider branches, almost twice those of B. delicata, and its extreme robustness. This species is distinguished from other species of Banastella, n. gen. by its much more open mesh, elon- gate nodes occurring lengthwise across the dissepiment obverse surface, longest chamber dimension which parallels the reverse wall proximally and curves toward the obverse surface distally, and measured chamber dimensions. The open, loosely knit mesh found in B. delicata is moderately rare in Warsaw fenestrates, with a closer mesh pattern more typical. Material studied.—Twenty-six exterior fragments, eight sectioned specimens; largest zoarial fragment 11x20 mm (width to length). The delicate nature of this species results in infrequent preservation of un- crushed complete zoaria, although disarticulated frag- ments in various states of preservation are common. Occurrence. — Banastella delicata is relatively rare at the Valmeyer and St. Louis localities; it occurs pri- marily in the Lower Warsaw, where it is present in both limestones and shales. Holotype.—UI X-6793 (loc. 49B, sample 12). Paratypes.— UI X-6781, 6782, 6783, 6967-6970 (loc. 49B, samples 8, 13). Genus CUBIFENESTELLA, new genus Etymology of name.— Named for the approximately cubic form characteristic of autozooecial chambers in this genus. Type species.— Fenestella rudis Ulrich, 1890; p. 537, pl. 49, figs. 3-3d [Lower Carboniferous, Valmeyeran Stage; Keokuk Limestone; Illinois Basin]. Diagnosis.— Zoarium robustness intermediate to ro- bust, mesh spacing intermediate to open; chamber out- line an irregular pentagon to rectangle in mid tangential section, chamber size intermediate; aperture size vari- able, small to large, opening at slight to pronounced angle toward and into fenestrule; superior and inferior hemisepta absent; chamber reverse-wall budding-an- gle varies between 64? and 81? (means). Three-dimensionally reconstructed chamber form a PALAEONTOGRAPHICA AMERICANA, NUMBER 57 regular cubic to irregular rectangular box. Description.—Zoarium robustness intermediate to robust, expansion flat to obversely or reversely curved, mesh spacing intermediate to open, ranging from reg- ular to irregular. Branch width narrow to intermediate, straight to sinuous in trace with lateral branches broadly curved toward edge of zoarium; branch surface rounded to angular. Keel present, single, width intermediate to wide, straight to slightly anastomosing, exhibiting pro- nounced astogenetic thickening. Nodes present, em- placement monoserial, size large to intermediate, shape stellate, ovate to circular, located in middle of keel, spacing intermediate. Obverse stylets present, size in- termediate, occurring across obverse surface or be- tween nodes along keel. Microstylets present, size small to intermediate, occurring across obverse surface or between nodes along keel. Macrostylets present in some species, large, typically located at sites of branch-dis- sepiment junction. Autozooecia in two rows, third row at site of branch bifurcation. Heterozooecia absent. Dissepiments of intermediate width, length inter- mediate to long, connect branches at regular to variable intervals. Fenestrule size intermediate to large, shape elliptical, ovate, rectangular to polygonal. Aperture size ranging from small to large, shape ovate, orientation ranging from slight to pronounced angle toward and into fenestrule. Peristome present or absent, complete where present. Apertural stylets pres- ent, develop as extension of aperture end, fuse to form peristome. Terminal diaphragms present, occurring to- ward proximal end and throughout zoarium. Branch shape in cross-section ranging from ovate to elliptical to circular, thick to medium in depth. Autozooecial chamber size intermediate, chamber emplacement monoserial or biserial along sinuous to zigzagged axial wall; chamber length and depth ap- proximately equal. Chamber outline triangular to ovate Text-figure 13.— Cubifenestella rudis illustrated. 1, diagrammatic longitudinal section illustrating chamber outline from deep section near middle of branch (bottom of figure) to shallow section near abaxial edge of branch (top of figure) [Observe approximately equal length and depth of chambers typical in this genus.], x 70; 2, dia- grammatic tangential section showing changing chamber outline from deep section near reverse-wall budding-site (bottom of figure) to shallow section near obverse surface (top of figure), x70; 3, dia- grammatic transverse section illustrating orientation of aperture openings to plane of obverse surface (arrow) and continuity of gran- ular skeleton across the dissepiment between branches, x 70; 4, re- construction of typical chamber shape (three-dimensional) as viewed from distal end of branch; chamber reconstructed is from right side of branch, x140; 5, reconstruction of typical chamber shape (three- dimensional) as viewed from abaxial edge of branch, x140; 6, re- construction of typical chamber shape (three-dimensional) as viewed from obverse surface; chamber reconstructed is from the right side of branch [Observe ovate shape of aperture (arrow), which is posi- tioned on distal-abaxial edge of chamber.], x 140. MISSISSIPPIAN BRYOZOANS: SNYDER 89 near reverse wall; becoming irregularly pentagonal to rectangular in mid chamber and throughout most of chamber depth; pentagonal, rectangular, elliptical, Square to ovate near obverse surface. Vestibule present, Varying in length from short to long. Superior and Inferior hemisepta both absent. Lateral-wall budding- angle ranging from 18? to 37° (means); reverse-wall budding-angle ranging from 64? to 81? (means). La- mellar skeletal layer thickness intermediate to thick, exhibiting moderate to pronounced astogenetic thick- ening; granular skeletal layer thickness intermediate to thick, exhibiting moderate astogenetic thickening. Three-dimensionally reconstructed chamber form a regular cubic to irregular rectangular box. 90 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 Text-figure 13 illustrates zoarial outlines in longi- tudinal, tangential, and transverse orientations, and three-dimensional reconstructions from distal, abaxial edge of branch, and obverse surfaces. Remarks.—Morozova (1974) assigned Fenestella rudis Ulrich, 1890, herein designated the type species of Cubifenestella, to the genus Rectifenestella Moro- zova, 1974. Species of Rectifenestella typically have a chamber form that is more cuneate, compared to the box-like form in Cubifenestella, they have short su- perior hemisepta, which are lacking in Cubifenestella, and they typically exhibit a much finer meshwork than does Cubifenestella. These factors result in removal of Fenestella rudis from Rectifenestella and its placement in a genus of its own, Cubifenestella. Among the fenestellids, members of Cubifenestella most closely resemble members of Apertostella, n. gen., another genus based on Warsaw specimens. Cubife- nestella is distinguished by a more open meshwork, a third apertural row at the site of branch bifurcation only, rather than for distances along the branch prox- imal to the bifurcation as is found in many species of Apertostella, and chambers that open at a slight to pronounced angle toward and into the fenestrule, as compared with Apertostella, which has apertures open- ing generally parallel to the plane of the obverse surface or at a slight angle toward the fenestrule. Primary dif- ferences in chamber form are the position and orien- tation of the aperture relative to the chamber (see Text- figs. 16-4, 17-4); and a more cubic chamber in Cubi- fenestella than in Apertostella. However, similarities in chamber shape suggest close phylogenetic affinities. Species composition.—Three Warsaw species are as- signed to the genus: C. rudis (Ulrich, 1890), C. usitata, n. sp., and C. globodensata, n. sp. Range.—Middle Mississippian (Valmeyeran), oc- curring in the Keokuk, Warsaw, Salem and St. Louis formations. Cubifenestella rudis (Ulrich, 1890) Plate 29, figures 1-11, Plate 30, figures 1-7; Text-figure 13; Table 26 Fenestella rudis Ulrich, 1890, p. 537, pl. 49, figs. 3-3d [Keokuk Limestone, Keokuk and Bentonsport, Iowa; Warsaw and Nauvoo, Illinois]; Keyes, 1894, p. 23, pl. 34, fig. 5 [Keokuk Limestone, St. Francisville, Missouri]; Cumings, 1906, p. 1277, pl. 27, figs. 3- 3d; Koenig, 1958, p. 136, pl. 21, fig. 7, text-figs. li, 1jj, table 8; Trizna, 1958, p. 127, pl. 34, fig. 5; pl. 35, figs. 1—4; Elias, 1964, p. 377, fig. 1; pl. 2, figs. 1-3. Fenestella iowensis Elias, 1964, p. 378, pl. 1, fig. 2; pl. 3 [entire plate]; pl. 5, fig. T. Fenestella rudiformis Elias, 1964, p. 379, pl. 1, fig. 3; pl. 4 [entire plate]; pl. 5, fig. 2. Diagnosis.—Zoarium extremely robust, mesh spac- ing intermediate, pattern moderately regular; branches Table 26.—Summary numerical analysis of Cubifenestella rudis (Ulrich, 1890). For explanation of abbreviations of characters (left column), see Table 8b (foldout inside back cover). number of mea- coeffi- sure- standard cient of observed ments mean deviation variation range 1. WB 24 0.3504 0.1559 44.49 0.144-0.775 2. DBC 24 0.6671 0.1495 22.41 0.369-0.960 3. WD 24 0.2388 0.0969 23.88 0.131-0.475 4. LF 24 0.7455 0.1990 26.69 0.300-1.125 5. WE 24 0.3619 0.0645 17.82 0.269-0.490 6. AF 24 3.08 0.78 29.19 2-4 7. AL 24 0.1759 0.0081 4.61 0.166-0.198 8. AW 24 0.1435 0.0054 3.76 0.130-0.154 9. ADB 24 0.3058 0.0221 7.23 0.266-0.355 10. AAB 24 0.3259 0.0358 10.98 0.255-0.393 11. ABB 24 0.4388 0.0774 17.64 0.304—0.549 12. DN 24 0.1785 0.0560 31.37 0.102-0.300 14. SNB 24 0.6614 0.1205 18.22 0.421-0.964 15. WK 24 0.1815 0.0534 29.42 0.088-0.273 16. DSO 24 0.0137 0.0055 40.15 0.007-0.028 17. SSO 24 0.0452 0.0209 46.24 0.013-0.096 18. WP 24 0.0129 0.0024 18.60 0.009-0.029 21. RSL 24 0.0799 0.0173 21.65 0.047-0.119 22. RSS 24 0.0131 0.0041 31.30 0.008-0.023 23. SSL 24 0.6543 0.3238 49.49 0.313-1.313 24. SSS 24 0.0426 0.0148 34.74 0.014-0.074 32. TRW 24 0.0091 0.0028 30.77 0.005-0.016 33. TLW 24 0.0089 0.0033 37.08 0.006-0.014 34. FWT 24 0.1812 0.1077 59.44 0.066-0.447 35. RWT 24 0.2199 0.2029 92.37 0.050-0.859 36. CL 24 0.2832 0.0149 5.26 0.255-0.316 37. CD 24 0.2699 0.0139 5.15 0.241-0.295 38. MAW 24 0.1874 0.0154 8.22 0.163-0.221 39. MIW 24 0.1298 0.0150 11.56 0.108-0.166 40. VD 24 0.1567 0.0712 45.44 0.085-0.357 41. RA 24 64.46 4.98 TIZ 55-74 42. LA 24 18.42 3.84 20.87 12-26 43. TB 24 0.6899 0.0738 10.70 0.569-0.819 robust, width intermediate, depth thick; straight to sin- uous, broadly curved at lateral zoarial edge; trans- versely ovate to elliptical, intermediately spaced and joined at highly variable intervals by intermediate- width, intermediate-length dissepiments. Fenestrule size upper-end intermediate; shape elliptical to ovate, highly variable. Autozooecial apertures large, ovate, elongate proximoabaxially to proximodistally; sur- rounded by thin, intermediately developed, complete peristome across which small apertural stylets project; two to four (most commonly three) apertures per fe- nestrule. Single wide, continuous keel; straight, ex- tending along middle of obverse branch surface, atop which are positioned large, slightly stellate to ovate nodes. Autozooecial chamber size upper-end inter- mediate, chambers emplaced in two rows, except third row at sites of branch bifurcation; outline irregularly triangular near reverse wall, rapidly becoming irregu- larly pentagonal in mid chamber, outline changing from MISSISSIPPIAN BRYOZOANS: SNYDER 91 Pentagonal to rectangular approaching obverse surface; Near obverse surface irregularly ovate. Chambers elon- gate parallel to proximal and distal lateral chamber walls. Aperture at distal-abaxial end of chamber, con- nected to chamber by extremely long vestibule of high- ly variable length. Superior and inferior hemisepta both absent. Lateral-wall budding-angle highly variable (mean of 18°); reverse-wall budding-angle constant (mean of 64°). 1 Table 26 presents statistical criteria used in delim- iting this species. Exterior description.—Zoarium extremely robust, expansion flat, exhibiting little or no obverse or reverse Curvature in any zoarial fragments examined, fan- Shaped; mesh spacing intermediate; pronounced astogenetic thickening of both obverse and reverse Zoarial skeleton; external zoarial pattern moderately irregular. Probable mature widths 20 to 30 mm, lengths 35 to 45 mm. Branches robust, width intermediate, highly vari- àble; straight to sinuous, exhibiting slight inflections toward sites of dissepiment insertion, lateral branches commonly broadly curved toward edge of zoarium. Branch spacing intermediate, distance between adja- Cent branch centers slightly irregular. Obverse surface texture highly granular, becoming increasingly so with astogeny; surface rounded, except for presence of single keel; keel wide, well-developed, continuous, straight to slightly sinuous extending along branch midline and Causing pronounced positive inflection in obverse sur- face profile. Pronounced astogenetic thickening of keel; toward most proximal end of zoarium keel extends across entire obverse surface, nearly to completely cov- ering apertural openings, starting at most adaxial edge and filling in toward the abaxial direction. Nodes mono- Serially emplaced, well-developed, extremely large, Slightly stellate to ovate in shape, elongate proximo- distally; variable in both size and shape; develop as Projections from middle of keel; one to two per fenes- trule length, frequently positioned at or near sites of branch-dissepiment Junction; spacing intermediate, Moderately even; pronounced increase of node di- ameter with astogeny. Intermediate, variably sized sty- lets irregularly positioned along obverse surface. Re- Verse surface texture granular, coarsening with astogeny, bearing few rows of widely spaced longitudinal striae, Occurring in exterior view at distal end of zoarium, becoming covered immediately proximal from zoarial distal edge due to pronounced astogenetic thickening Of lamellar skeleton; rows of small, closely spaced mi- Crostylets develop as extensions of longitudinal striae, become variably spaced across entire reverse surface and exhibit slight increase in diameter with astogeny. arge, approximately circular macrostylets, moderate- Y regular in size and shape and variable in placement, located at or near sites of branch-dissepiment Junction on reverse surface. Autozooecia in two rows across branch, except third row at sites of branch bifurcation where middle autozooecium evidentiy shared by both branches; pronounced thickening proximal, thinning distal to sites of branch bifurcation. Heterozooecia ab- sent in all zoarial fragments observed. Dissepiments of intermediate width, approximately two-thirds that of branch, slightly variable in width; length intermediate, constant; connect branches at highly variable intervals. Dissepiments exhibit mod- erate medial thinning, pronounced flaring at branch- dissepiment junction; highly recessed from obverse surface, even with reverse. Pronounced astogenetic thickening of dissepiment toward proximal end of zoarium. Obverse dissepiment surface with medially thickened ridge atop which occur rows of small, irreg- ularly spaced stylets which increase in diameter with astogeny; reverse dissepiment surface with small sty- lets irregularly positioned across surface, stylet number and size increase with astogeny. Both obverse and re- verse dissepiment surfaces granular in texture, becom- ing increasingly so with astogeny. Dissepiment emplacement most commonly approximately perpen- dicular to branch length, more rarely at angle up to 20° from perpendicular to branch length. Apertures com- monly positioned on proximal or distal edge or in mid- dle of dissepiment edge at branch-dissepiment contact; arranged symmetrically or asymmetrically between branches. Fenestrule size upper-end intermediate, shape ellip- tical to ovate, becoming increasingly ovate with as- togeny, elongate proximodistally; highly variable in size and shape; slightly expanding in width and length in obverse-reverse direction. Mean width of fenestrule slightly greater than branch width; fenestrule becoming appreciably smaller, at times completely closed toward proximal end of zoarium with astogenetic thickening of lamellar skeleton. Ratio of mean fenestrule width to length approximately 1:2; width more constant than length, both variable. Two to four (most commonly three) apertures per fenestrule length; distance between closest aperture centers along branch and across branch approximately equal, spacing of apertures across fe- nestrule approximately 1.5 times greater; spacing along branch and across branch constant, spacing across fe- nestrule moderately variable. Autozooecial apertures large, ovate, elongate prox- imoabaxially to proximodistally, width to length ratio approximately 4:5; size and shape highly uniform; opening most commonly oriented at slight angle to- ward and into fenestrule or rarely at pronounced angle toward and into fenestrule; thin, intermediately de- veloped complete peristome surrounding aperture, commonly with small apertural stylets projecting from 92 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 peristome toward proximal end of zoarium, forming through secondary overgrown lamellar skeletal layer and having the same dimensions as small obverse sty- lets. Aperture margins extend into fenestrule, causing pronounced inflections in fenestrule outline on obverse surface. In late astogeny apertures become covered by centrally thickened terminal diaphragms. Large, well-developed zoarial supports develop as extensions of reverse zoarial surface and lateral edge of zoarium. Interior description.— Branches ovate to elliptical in transverse section, commonly slightly enlarged on ob- verse surface, elongate in obverse-reverse direction. Branches thick, regular in depth. Autozooecial living chamber size upper-end inter- mediate, chambers biserially arranged in alternating rows along planar branch axial wall; axial wall highly sinuous, exhibiting inflections toward and connecting with chamber lateral walls near reverse wall and throughout chamber; inflections become less pro- nounced near obverse surface. Chamber longest di- mension only slightly greater than depth, elongate par- allel to proximal and distal lateral chamber walls. Autozooecial chamber outline rounded, irregularly tri- angular near reverse wall; rapidly becoming irregularly pentagonal throughout most of chamber length, outline changing from pentagonal to rectangular approaching obverse surface; near obverse surface chambers irreg- ularly ovate; chamber shape highly uniform. Aperture positioned at distal-abaxial end of chamber, connected to chamber by extremely long, well-developed, highly variable-length vestibule. Ratio of autozooecial cham- ber minimum width to maximum width approxi- mately 7:10; maximum width to depth ratio about 7:10; dimensions of depth to length of chamber ap- proximately equal, length only very slightly greater than depth; chamber length and depth highly constant, max- imum and minimum widths moderately constant. Su- perior and inferior hemisepta both absent. Autozooe- cial chambers diverge laterally from middle of branch at highly variable angle (mean of 18°); from reverse wall at a constant angle (mean of 64°). Three-dimensionally reconstructed chamber form a regular box; approximately equidimensional in length and depth as viewed from lateral edge and distal end of branch respectively; width as viewed from obverse surface moderately less than length or depth. Internal granular skeletal layer thick, well-devel- oped; continuous with obverse nodes, stylets, keel, per- istome; reverse longitudinal striae, microstylets and macrostylets; across dissepiments and in the middle of zoarial supports. Outer lamellar layer extremely thick, exhibiting pronounced astogenetic thickening on both obverse and reverse exterior zoarial surfaces. Remarks.—Fenestella rudis Ulrich, 1890 was first described from the Keokuk Limestone and Warsaw Beds near Keokuk, Iowa, and Warsaw, Illinois. Ulrich (1890, p. 537) noted marked variation within this spe- cies, caused in his opinion by varying “age and state of preservation.” Based on my observations, astoge- netic variability of exterior appearance is greater than in most other fenestellids. The assignment of Ulrich’s syntypes of Fenestella rudis into two species, Fenestella iowensis Elias, 1964, and Fenestella rudiformis Elias, 1964, is not justified by internal analyses. Interior and exterior dimensions for both F. iowensis and F. rudiformis are within the observed range for C. rudis, and I therefore place these species in synonymy with C. rudis. Characteristic astogenetic thickening, chamber shape, presence of apertural stylets, mesh pattern, and aper- ture orientation are similar in C. rudis, C. usitata, and C. globodensata, suggesting close taxonomic affinities. Variability of mesh symmetry due to astogenetic thick- ening makes recognition of C. rudis heavily dependent on use of internal characteristics such as autozooecial chamber dimensions and reverse-wall budding-angle. C. rudis is distinguished from other species of Cubi- fenestella by a finer mesh, larger autozooecial chamber, and thicker branches. Material studied.—Fourty-four exterior fragments, 14 sectioned specimens; largest zoarial fragment 32 x 26 mm (width to length). Microstructural and whole spec- imen preservation is good to excellent in all material collected. Occurrence.— Cubifenestella rudis is common throughout the Warsaw Formation: it is also reported from the Keokuk and Salem formations in the study area. Observation suggests the zoarial mesh is more open in shaly facies, and becomes coarser with thicker branches in calcarenitic facies; internal characters re- main the same regardless of exterior mesh variation. Syntypes.—ISGS(ISM) 2745-1, 2776-1/2; USNM 43759. One specimen is illustrated in Ulrich (1890, pl. 49, figs. 3, 3a, 3b, 3c, 3d). Figured and/or measured specimens.— UI X-6718, 6744,6752, 6754 (loc. 10, samples 28, 31), 6900-6903, 6753, 6755-6758 (loc. 49B, samples 8, 12, 13). Cubifenestella usitata, new species Plate 31, figures 1-12, Plate 32, figures 1-6; Table 27 Etymology of name.—Named for the lack of dis- tinctive distinguishing characteristics in exterior view, this species exhibits a typical fenestellid fan shape. Diagnosis.—Zoarium robustness intermediate, mesh intermediate, pattern moderately regular; branch ro- bustness and width intermediate, branches thick in depth; branches straight to broadly curved; transverse ly ovate to approaching circular, spacing intermediate; branches joined at regular intervals by intermediate MISSISSIPPIAN BRYOZOANS: SNYDER 93 Table 27.— Summary numerical analysis of Cubifenestella usitata, n. sp. For explanation of abbreviations of characters (left column), see Table 8b (foldout inside back cover). number of mea- coeffi- sure- standard cient of observed ments mean deviation variation range 1. WB 24 0.3189 0.0816 25.59 0.219-0.500 2. DBC 24 0.6244 0.1149 18.40 0.403-0.853 3. WD 24 0.2018 0.0288 14.27 . 0.150-0.263 4. LF 24 0.8459 0.0743 8.78 0.673-0.973 5. WF 24 0.3199 0.0765 23.91 0.167-0:463 6. AF 24 3.96 0.46 11473 3-5 7. AL 24 0.1434 0.0066 4.60 0.125-0.155 8. AW 24 0.1043 0.0086 8.25 0.088-0.128 9. ADB 24 0.2715 0.0184 6.78 0.243-0.313 10. AAB 24 0.2624 0.0339 12.92 0.203-0.337 ll. ABB 24 0.4178 _..0.0990. 23.70: _ 0.223-0,565 12. DN 24 0.1456 0.0243 16.69 0.101-0.203 14. SNB 24 0.7747 0.1611 20.80 -0.413-1.150 15. WK 24 0.1177 0.0377 3208 -0,071=0.200 16. DSO 24 0.0119 0.0028 23.53 - 0:008-0:019 17. SSO 24 0.0524 0.0131 25.00 0.026-0.088 19. SA 24 8.58 0.88 10.26 HW) 20. SAD 24 0.0110 0.0019 17.36 0.008-0.013 22. RSS 24 0.0189 0.0032 16.85 0.034-0.026 24. SSS 24 0.0571 0.0130 22.77 0.033-0.091 32. TRW 24 0.0085 0.0013 15.70 0.006-0.011 33. TLW 24 0.0111 0.0017 15.56 0.008-0.014 34. FWT 24 0.0838 0.0388 46.28 0.026-0.166 35. RWT 24 0.0720 0.0304 42.24 0.014-0.123 36. CL 24 0.2454 0.0100 4.07 0.221-0.264 37. CD 24 0.1834 0.0123 6.71 | 0.160—0.209 38. MAW 24 0.1450 0.0174 12.00 0.116-0.184 39. MIW 24 0.0868 0.0123 14.17 0.068-0.121 40. VD 24 0.0505 0.0190 37.77 0.030-0.082 4l. RA 24 67.87 4.87 ily 58-77 42. LA 24 37.29 5.43 14.57 28-49 43. TB 24 0.4117 0.0798 19.38 0.294-0.596 width and length dissepiments. Fenestrule size inter- Mediate, shape elliptical to approaching rectangular, highly regular. Autozooecial aperture size intermedi- ate, shape ovate, elongate proximodistally; surrounded by seven to 11 (mean of nine) small stylets; three to five (most commonly four) apertures per fenestrule. ingle intermediate-width, continuous keel; straight, extending along middle of obverse branch surface, atop which are positioned large, circular to ovate nodes. Autozooecial chamber size intermediate, emplaced in two rows, except third row at sites of branch bifurca- tion; outline irregular-ovate to rounded-triangle near Teverse wall, rapidly becoming irregularly pentagonal throughout chamber, shape becoming increasingly rectangular toward obverse surface; near obverse sur- face chamber rectangular to elliptical, nearest obverse Surface chamber approximately square. Chambers elongate parallel to proximal and distal lateral chamber Walls. Aperture at distal and highly abaxial edge of Chamber, connected to chamber by short, variable- length vestibule. Superior and inferior hemisepta ab- sent. Lateral-wall budding-angle moderately variable (mean of 37°); reverse-wall budding-angle constant (mean of 68°). Table 27 presents statistical criteria used in species delimitation. Exterior description.—Zoarium robustness inter- mediate, expansion flat, planar to slightly obversely curved, fan-shaped; mesh spacing intermediate; mod- erate astogenetic thickening of both obverse and re- verse zoarial lamellar skeleton; external zoarial pattern moderately regular. Probable mature widths 20 to 35 mm, lengths 35 to 50 mm. Branch robustness intermediate; width intermedi- ate, variable; straight in trace, lateral branches fre- quently broadly curved toward edge of zoarium. Branch spacing intermediate, distance between adjacent branch centers moderately regular. Obverse surface texture granular, becoming increasingly so with astogeny, sur- face profile angular to slightly rounded; except for pres- ence of single keel of intermediate width, extremely well-developed, continuous, straight, positioned along branch midline causing pronounced positive inflection in obverse surface profile. Pronounced astogenetic thickening of keel, which develops to extend across entire obverse surface between apertures and frequent- ly covers most adaxial edge of aperture. Nodes em- placed in single row, extremely well-developed, large; shape circular to ovate, elongate proximodistally when Ovate; size and shape moderately regular; one to two nodes per fenestrule length, frequently positioned at or near sites of branch-dissepiment junction; node spac- ing upper-end intermediate, moderately even; diam- eter increasing with astogeny. Intermediate-size stylets, variable in size and positioning, located across obverse branch surface, increasing in number and diameter with astogeny. Reverse surface texture granular, coarsening with astogeny; bearing relatively few rows of inter- mediately spaced longitudinal striae which become covered by astogenetic thickening of lamellar skeleton; rows of closely spaced intermediate-size microstylets atop striae along reverse surface, microstylet size mod- erately regular; with astogeny microstylets increase in diameter and become more irregularly positioned across reverse branch surface. Two rows of autozooecia across branch, except third row at sites of branch bifurcation where middle autozooecium evidently shared by both branches; moderate to pronounced thickening of branches proximal, thinning distal to sites of branch bifurcation. Heterozooecia not present in any zoarial fragments examined. Dissepiments of intermediate width, approximately two-thirds that of branch; constant in width; length intermediate, moderately variable; connect branches at regular intervals. Dissepiments barlike, exhibiting 94 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 slight medial thinning and moderate flaring at branch- dissepiment contact; highly recessed from obverse sur- face, moderately recessed from reverse. Moderate to pronounced astogenetic thickening toward proximal end of zoarium. Obverse dissepiment surface with thickened barlike expansion positioned longitudinally across dissepiment and oriented approximately per- pendicular to branch length; small, irregularly spaced stylets occurring across obverse dissepiment surface; reverse surface with longitudinal striae oriented per- pendicular to branch length, atop which occur rows of small to intermediate-size stylets; both obverse and reverse dissepiment surfaces granular, becoming in- creasingly so with astogeny. Dissepiments most com- monly emplaced approximately perpendicular to branch length. Apertures commonly open on proximal or distal edge or in middle of dissepiment edge at branch-dissepiment contact; arranged symmetrically or asymmetrically between branches. Fenestrule size intermediate, shape elliptical to ap- proaching rectangular, elongate proximodistally; high- ly regular in shape, overall size variable; exhibiting little or no expansion in length and width in obverse- reverse direction. Mean width of fenestrule approxi- mately equal to branch width; fenestrule opening be- coming moderately to appreciably smaller toward proximal end of zoarium with astogenetic thickening of lamellar skeleton. Ratio of mean fenestrule width to length approximately 3:8; length constant, much more so than width, which is highly variable. Three to five (most commonly four) apertures per fenestrule length; distance between closest aperture centers along branch and across branch approximately equal, spac- ing of apertures across fenestrule 1.6 times greater; spacing along branch and across branch constant, spac- ing across fenestrule moderately variable. Autozooecial aperture size intermediate, shape ovate, elongate proximodistally and slightly enlarged at distal end; aperture opening oriented approximately 45° into fenestrule from parallel to plane of obverse surface, rarely approaching parallel to plane of obverse surface; peristome lacking. Seven to 11 (mean of nine) small stylets fairly constant in size and moderately variable in number, surround aperture; stylet diameter exhib- iting slight increase in diameter with astogeny. Aper- tures even with branch surface, causing no inflections in fenestrule outline. Centrally thickened terminal di- aphragms frequently occurring at most proximal end of zoarium, less frequently distally. Well-developed zoarial supports present as exten- sions of reverse zoarial surface. Interior description.—Branches ovate to approach- ing circular in transverse view, moderately symmet- rical, elongate in obverse-reverse direction. Branches thick, variable in depth. Autozooecial living chambers of intermediate size, monoserially emplaced at or near reverse-wall bud- ding-site, become biserially arranged in alternating rows along a planar branch axial wall; axial wall sinuous, exhibiting pronounced inflections toward and con- necting with chamber lateral walls near reverse surface and throughout most of chamber length, toward ob- verse surface sinuous nature is reduced and axial wall becomes nearly straight. Chamber longest dimension parallel to proximal and distal lateral chamber walls. Autozooecial chamber outline irregular ovate to rounded triangle near reverse wall; rapidly becoming irregularly pentagonal throughout most of chamber length, with outline becoming increasingly rectangular toward obverse surface; approaching obverse surface chamber outline rectangular to elliptical, nearest ob- verse surface chamber approximately square; chamber shape highly uniform. Aperture positioned at distal and highly abaxial edge of chamber, connected to chamber by short, intermediately developed variable- length vestibule. Ratio of autozooecial chamber min- imum width to maximum width approximately 3:5; maximum width to depth ratio about 4:5; ratio of depth to length of chamber approximately 3:4; chamber length and depth highly constant, minimum and maximum widths slightly variable. Superior and inferior hemi- septa both lacking. Autozooecial chambers diverge lat- erally from middle of branch at moderately variable angle (mean of 37°); from reverse wall at a constant angle (mean of 68°). Three-dimensionally reconstructed chamber form a rectangular irregular box; length as viewed from lateral edge of branch; depth as viewed from distal end of branch; width as viewed from obverse surface. Internal granular skeletal layer width intermediate, continuous with obverse nodes, stylets, keel, and ap- ertural stylets; reverse striae and stylets; across dissep- iments and in the middle of zoarial supports. Moderate to pronounced thickening of lamellar skeleton toward proximal end of zoarium with astogeny. Remarks.— Differentiation between C. usitata, n. sp. and C. globodensata, n. sp. based on exterior charac- teristics is difficult due to similarity in mesh pattern, astogenetic thickening, aperture orientation, and pres- ence of apertural stylets. C. usitata differs from C. glo- bodensata by its larger chamber size, more widely spaced obverse nodes, wide branches, and more closely spaced mesh. Pronounced differences in positioning of the chamber relative to the branch exist between the two species as well. Internal similarity to C. rudis (UI- rich, 1890) suggests strong affinities among the three species; differences include chamber dimensions and general mesh symmetry. ' C. usitata exhibits slight similarity in exterior ap- pearance with Fenestella funicula Ulrich, 1890. It dif- fers in having narrower branches, tighter mesh, and MISSISSIPPIAN BRYOZOANS: SNYDER 95 Table 28.—Summary numerical analysis of Cubifenestella globo- densata, n. sp. For explanation of abbreviations of characters (left column), see Table 8b (foldout inside back cover). number of mea- coeffi- sure- standard cient of observed ments mean deviation variation range 1. WB 24 0.2777 0.0601 21.64 0.188-0.407 2. DBC 24 0.7034 0.1873 26.63 0.400-1.133 3. WD 24 0:2110: 130106706. 3132:04:05 40410220367 4. LF 24 0.975358 OLEG 17506 101667—1. 267; 5. WF 24 0.4104 0.1400 34.11 0.222-0.760 6. AF 24 4.25 0.85 19.93 3-6 ESTATE 24 0.0835 0.0075 8.98 0.069-0.100 8. AW 24 0.0671 0.0061 9.03 0.057-0.083 9. ADB 24 0.2799 0.0269 9.61 0.238-0.340 10. AAB 24 0.2946 0.0293 9.95 0.247-0.343 11. ABB 24 0.5333 0.0964 18.08 0.313-0.903 12. DN 24 0.1247 0.0336 26.94 0.072-0.213 14. SNB 24 0.4451 0.0956 21.48 0.214-0.600 15. WK 24 0.1277 0.0429 33.59 0.067-0.216 16. DSO 24 0.0188 0.0041 34.75 0.006-0.023 17. SSO 24 0.0534 0.0165 30.90 0.021-0.089 18. WP 24 0:0211- 0.005172 24.17 20:01550/039) 19. SA 24 16.28 3.99 21.81 14-22 20. SAD 24 0.0107 0.0045 42.06 0.007-0.017 22. RSS 24 0.0249 0.0065 26.10 0.016-0.043 24. SSS 24 0.0529 0.0168 431.76" 0.027-0:096 32. TRW 24 0.0069 0.0010 13.91 0.006-0.009 33. TLW 24 0.0107 0.0013 12.06 0.008-0.013 34. FWT 24 00592 00337. 5695 0.015-0250 35. RWT 24 0.0988. 20.0507 51.32 °0.01720200 36. CL 24 0.2133 0.0083 3.89 0.199-0.229 37. CD 24 0.1546 0.0071 4.59 0.143-0.169 38. MAW 24 02123352.0:.012972 10.02 20.21220754 39. MIW 24 0.0415 0.0143 34.46 0.016-0.068 40. VD 24 0.0757 0:02 T2 3801. COR OTIO 41. RA 24 81.04 7.67 9.46 69-94 42. LA 24 33.96 6.13 18.04 20-44 43. TB 24 013238. DIOSA aida: 20265037 More pronounced orientation of aperture opening into fenestrule opening than was reported and observed by Ulrich in F. funicula. Material studied.— Twenty-two exterior fragments; Seven sectioned specimens; largest zoarial fragment 27x38 mm (width to length). Excellent microstruc- tural and whole specimen preservation is observed in all material collected. Occurrence.— Cubifenestella usitata is common at the Valmeyer, St. Louis and associated localities in the Southern part of study area. It occurs throughout the Warsaw Formation, and is equally common in lime- Stones and shales. Holotype. —UI X-6709 (loc. 49B, sample 12). Paratypes.— UI X-6704, 6708, 6712 (loc. 49B, sam- ples 12, 13, 15), 6723, 6831 (loc. 10, samples 24, 29), 6869 (loc. 47A, sample 27). Cubifenestella globodensata, new species Plate 33, figures 1-11, Plate 34, figures 1-6; Table 28 Etymology of name.—Named for the globularly thickened obverse surface, resulting from overgrowth of the keel and obverse surface by the external lamellar skeletal layer, resulting in infilling of apertural openings during astogeny. Diagnosis.— Zoarium robustness intermediate, mesh open, pattern highly variable; branches moderately ro- bust, width thin, depth intermediate; straight to anas- tomosing to broadly curved; branches transversely cir- cular to irregularly ovate, widely spaced; branches joined at variable intervals by intermediate-width, long dissepiments. Fenestrules large; shape elliptical, irreg- ularly polygonal to ovoid, moderately irregular. Au- tozooecial apertures small, shape ovate, elongate prox- imodistally, surrounded by moderately well-developed, thin, complete peristome formed from fusion of 14 to 22 small stylets irregularly positioned around aperture; three to six (most comonly four) apertures per fenes- trule. Single intermediate-width, continuous keel along middle of obverse branch, atop which are positioned lower-end large, irregularly ovate to slightly stellate nodes. Autozooecial chamber size lower-end inter- mediate, emplaced in two rows, except third row at sites of branch bifurcation; outline irregularly ovate to rounded triangular near reverse wall, rapidly becoming irregularly pentagonal throughout most of chamber depth, outline irregularly elliptical near obverse sur- face, slightly enlarged at distal end. Chamber longest dimension parallel to reverse wall in proximodistal direction. Aperture positioned at distal-abaxial end of chamber, connected to chamber by intermediate, vari- able-length vestibule. Superior and inferior hemisepta both absent. Lateral-wall budding-angle variable (mean of 34°); reverse-wall budding-angle moderately con- stant (mean of 81?). Table 28 presents statistical criteria used in delim- iting this species. Exterior description.—Zoarium robustness inter- mediate, expansion flat, planar to rarely slightly ob- versely or reversely curved, fan-shaped; mesh spacing open; pronounced astogenetic thickening of both ob- verse and reverse zoarial lamellar skeleton, external zoarial pattern highly variable within and between zoaria. Probable mature widths 25 to 35 mm, lengths 35 to 60 mm. Branches moderately robust; thin, variable in width; straight to slightly anastomosing toward sites of dis- sepiment emplacement, lateral branches frequently broadly curved toward edge of zoarium. Branches widely spaced, distance between adjacent branch cen- ters moderately irregular. Obverse surface texture granular, becoming increasingly so with astogeny, sur- face rounded, except for presence of single, moderately well-developed positive inflection in obverse surface profile. Pronounced thickening of keel occurs with as- 96 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 togeny; keel forming a ropy expansion across most of obverse surface toward proximal end of zoarium, fre- quently extending over adaxial edge of aperture to completely overgrow aperture; lamellar skeleton cov- ering much of keel with astogeny. Nodes emplaced in single row, well-developed, size lower-end large; irreg- ularly ovate to slightly stellate in shape, elongate prox- imodistally; size and shape both highly variable; one to five nodes per fenestrule length; spacing interme- diate, moderately evenly spaced; diameter greatly in- creasing with astogeny. Intermediate-size stylets, vari- able in size, typically variably positioned in rows, located along obverse surface between nodes; increas- ing in diameter and number with astogeny. Reverse surface texture granular, coarsening with astogeny; bearing few rows of widely spaced longitudinal striae; with astogeny striae covered by thickening of lamellar skeleton, most prominent toward proximal end of zoarium; rows of intermediate size microstylets, close- ly spaced, located atop striae along reverse surface, microstylet size moderately variable; with astogeny microstylets greatly increase in diameter and become more irregularly positioned across reverse branch sur- face. Autozooecia in two rows across branch, except third row at sites of branch bifurcation where middle autozooecium evidently shared by both branches; slight to moderate thickening of branches proximal, thinning distal to site of branch bifurcation. Heterozooecia not present in any zoarial fragments examined. Dissepiments of intermediate width, approximately three-fourths that of branch; highly variable in width; dissepiments long, highly variable in length; connect branches at variable intervals. Dissepiments moder- ately barlike, exhibiting slight medial thinning and in- termediate flaring at branch-dissepiment contact; moderately recessed from obverse, approximately even with reverse surface. Moderate to pronounced asto- genetic thickening, most pronounced toward proximal end of zoarium. Obverse dissepiment surface with two to four thickened barlike expansions oriented longi- tudinally across dissepiment and emplaced perpendic- ular to branch length; small, irregularly spaced stylets occurring in rows atop striae; reverse dissepiment sur- face with two to four thickened barlike expanions, ori- ented perpendicular to branch length, atop which are positioned rows of small to intermediate-size stylets; both obverse and reverse dissepiment surfaces granular in texture, coarsening with astogeny. Dissepiments typically emplaced perpendicular to branch length, more rarely at a small angle from perpendicular. Ap- ertures commonly open on proximal or distal edge, more rarely in middle of dissepiment edge at branch- dissepiment contact; arranged symmetrically or asym- metrically between branches. Fenestrules large, typically elliptical, but also asym- metrically polygonal to ovoid in shape, elongate prox- imodistally; moderately irregular in shape, overall size variable; exhibiting no change in size or shape of open- ing from obverse to reverse surface. Mean width of fenestrule 1.5 times that of branch; fenestrule opening exhibiting slight decrease in size toward proximal end of zoarium due to astogenetic thickening of lamellar skeleton. Ratio of mean fenestrule width to length ap- proximately 2:5; length moderately constant, much more so than width, which is highly variable. Three to six (most commonly four) apertures per fenestrule length; distance between closest aperture centers along branch and across branch approximately equal, spac- ing of aperture centers across fenestrule approximately three times greater; spacing along branch and across branch moderately constant, spacing across fenestrule variable. Autozooecial apertures small, shape ovate, elongate proximodistally and slightly enlarged at distal end; ap- erture openings typically at a moderate to pronounced angle into fenestrule, rarely parallel to plane of obverse surface; thin, moderately well-developed complete peristome present. Fourteen to 22 (most commonly 16) small, variable-size, moderately well-developed and irregularly positioned stylets surround aperture; peri- stome develops from fusion of these stylets during as- togeny, with stylets most common at lateral and distal edges of zoarium. Aperture margins extend into fe- nestrule, causing very slight inflections in fenestrule outline on obverse surface. In late astogeny apertures frequently capped by centrally thickened terminal di- aphragms. Well-developed zoarial supports present as exten- sions of reverse zoarial surface and lateral edge of zoar- ium. Interior description.— Branches circular to irregular- ly ovate in transverse view, moderately symmetrical, elongate either parallel to plane of zoarium or in ob- verse-reverse direction. Branches intermediate, mod- erately regular in thickness. Autozooecial living chamber size lower-end inter- mediate, chambers monoserially emplaced at or near reverse-wall budding-site, rapidly becoming biserially arranged toward obverse surface along planar branch axial wall; axial wall forming zigzag pattern, extending diagonally across entire branch and forming chamber lateral walls; inflections reduced in mid chamber, axial wall connecting with short lateral walls; inflections fur- ther reduced near obverse surface. Chamber longest dimension parallel to reverse wall in proximodistal direction. Autozooecial chamber outline irregularly ovate to rounded triangular near reverse wall; rapidly becoming irregularly pentagonal throughout most of chamber depth; outline irregularly elliptical near ob- verse surface, slightly enlarged at distal-abaxial end of | | | | MISSISSIPPIAN BRYOZOANS: SNYDER 97 chamber; chamber shape moderately uniform. Aper- tures positioned at distal-abaxial edge of chamber, con- nect to chamber by well-developed, intermediate-length vestibules; vestibules variable in length. Ratio of au- tozooecial chamber minimum width to maximum width approximately 1:3; maximum width to depth ratio about 5:6; ratio of depth to length of chamber approximately 5:7; chamber length and depth highly constant, maximum width slightly variable and min- imum width highly variable. Superior and inferior hemisepta both absent. Autozooecial chamber diverg- es laterally from middle of branch at a variable angle (mean of 34°); from reverse wall at a moderately con- Stant angle (mean of 81°). Three-dimensionally reconstructed chamber form an irregular slightly rectangular box, length as viewed from lateral edge of branch; depth as viewed from distal end of branch, width as viewed from obverse Surface. Internal granular skeletal layer thick, exhibiting pro- hounced astogenetic thickening resulting in partial to complete infilling of autozooecial chambers toward most proximal end of zoarium; granular skeletal layer continuous with obverse nodes, stylets, keel, peri- stome, and apertural stylets; reverse striae and mi- Crostylets; across dissepiments including dissepiment longitudinal striae and stylets, and in the middle of Zoarial supports. Pronounced thickening of lamellar Skeleton, moderate thickening of granular skeleton with astogeny. Remarks.—The initial monoserial chamber em- Placement in Cubifenestella globodensata, n. sp. is sim- ilar to that found in species of Minilya Crockford, 1944 (e.g., M. sivonella, n. sp.); however, all other internal chamber and most external characters closely match those found in species of Cubifenestella, n. gen. Marked Similarities in appearance between C. globodensata and C. usitata, n. sp. suggest close phylogenetic affinity. Smaller chamber and aperture size, and highly variable Nature of node placement and mesh pattern of C. glo- bodensata allow ready separation of this species from C. usitata, the most similar congeneric species. Sole Teliance on external characters and mesh patterns for differentiation of these two species is not effective be- Cause of their overlapping external dimensions and Similarity in external characters. Cubifenestella globodensata moderately closely re- sembles Fenestella compressa Ulrich, 1890 from Kings Mountain, Kentucky in its large fenestrules, small and widely separated apertures, numerous nodes on a well- developed keel, and apertures facing into the fenes- trule. It is clearly separated by its much narrower branches, more closely spaced apertures, and finer mesh. Internal sections of F. compressa would be ben- eficial in species comparison, but were unavailable. Material studied.—Thirty-four exterior fragments; 26 sectioned specimens; largest zoarial fragment 20 x 36 mm (width to length). Excellent microstructural and whole specimen preservation is observed in most ma- terial collected. Occurrence.— Cubifenestella globodensata is com- mon at the Valmeyer, St. Louis, and associated local- ities in the southern part of the study area, south of White Hall. It occurs throughout the Warsaw and into the Lower Salem Formation at these localities, and is equally abundant in both limestones and shales. Holotype.— UI X-6702 (loc. 49B, sample 15). Paratypes.—UI X-6819-6830, 6705-6707, 6710, 6711, 6715, 6713, 6714 (loc. 49B, samples 13, 15, 16), 6703, 6700, 6701 (loc. 47A, samples 32, 35), 6750, 6751 (loc. 20, sample 10). Genus APERTOSTELLA, new genus Etymology of name.— Named for the distinctive, ir- regularly ovate, intermediate-size apertures character- istic of the genus. Type species.— Apertostella crassata, n. sp. Diagnosis. — Zoarium robustness ranging from del- icate to robust, mesh spacing close to intermediate; chamber outline irregularly pentagonal, rectangular to elliptical in mid tangential section, chamber size in- termediate; aperture size intermediate, opening typi- cally oriented parallel to plane of obverse surface or infrequently at slight angle toward fenestrule, superior and inferior hemisepta absent, chamber reverse-wall budding-angle varies between 67? and 69? (means). Three-dimensionally reconstructed chamber form a rectangular box. Description. — Zoarium robustness variable, ranging from delicate to robust, expansion flat, undulating to slightly obversely curved, mesh spacing close to inter- mediate, regular. Branch width intermediate to wide, straight to sin- uous in trace with lateral branches curved toward edge of zoarium; branch surface ranging from flat, slightly concave, angular to slightly rounded. Keel present, sin- gle, width narrow to intermediate, straight to slightly anastomosing, slightly thickening with astogeny and frequently covered by lamellar skeleton. Nodes pres- ent, emplacement monoserial, size intermediate to large, shape ovate to circular, located atop middle of keel, spacing intermediate to wide. Obverse stylets present or absent; where present, size large, occurring across obverse surface. Microstylets present, ranging in size from small to large, emplaced in rows, becoming variably placed with astogeny. Macrostylets present in some species, large, typically located at site of branch- dissepiment junction. Autozooecia in two rows, third row at sites of branch bifurcation or three rows for distance along branch proximal to branch bifurcation. 98 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 Heterozooecia absent. Dissepiments of thin to intermediate width, length short to intermediate, connect branches at regular in- tervals. Fenestrule size variable, ranging from small to large, shape rectangular to elliptical to ovate. Aperture size intermediate, shape ovate, oriented parallel to plane of obverse surface or infrequently at slight angle toward fenestrule. Peristome present, com- plete; apertural stylets either present or absent, develop as extension of peristomal edge; terminal diaphragms present, primarily occurring toward proximal end of zoarium. Branch shape in cross-section ranging from polyg- onal to ovate to elliptical, medium to deep in thickness. Autozooecial chamber size intermediate, chambers biserially emplaced along sinuous to zigzagged axial wall; maximum chamber dimension (length) extending proximodistally, parallel to reverse wall. Chamber out- line triangular, polygonal to irregularly pentagonal near reverse wall; becoming irregularly pentagonal, rect- angular to elliptical in mid chamber and throughout most of chamber depth; irregularly elliptical to ovate near obverse surface. Vestibule present, ranging in length from short to intermediate. Superior and infe- rior hemisepta both absent. Lateral-wall budding-angle ranging from 22° to 25° (means); reverse-wall budding- angle from 67° to 69° (means). Lamellar skeletal layer thickness intermediate to thick, exhibiting moderate to pronounced astogenetic thickening; granular skeletal layer thickness intermediate to thick, exhibiting no as- togenetic thickening. Three-dimensionally reconstructed chamber form a rectangular box. Text-figure 14 illustrates zoarial outlines in longi- tudinal, tangential, and transverse orientations, and three-dimensional chamber reconstructions from dis- tal, abaxial edge of branch, and obverse surfaces. Remarks.— Moderate similarities exist between spe- cies of Apertostella and Cubifenestella n. gen. Species of Apertostella are distinguished by a typically more closed meshwork, third row of autozooecia at sites of branch bifurcation and for pronounced distances along the branch proximal to sites of branch bifurcation, and chambers that open generally parallel to the plane of obverse surface. Species of Apertostella also typically exhibit a less cubic and more rectangular chamber shape than species of Cubifenestella, and have a more highly ovate apertural shape. Similarities between the two genera suggest close phylogenetic affinities, however difference in chamber orientation to the obverse surface is consistently pres- ent between them. The orientation of the chamber rel- ative to the zoarial surface, which is very different in Cubifenestella and Apertostella, apparently would have Table 29.—Summary numerical analysis of Apertostella foramen- major, n. sp. For explanation of abbreviations of characters (left column), see Table 8b (foldout inside back cover). number of mea- coeffi- sure- standard cient of observed ments mean deviation variation range 1. WB 24 0.3030 0.0608 20.07 0.213-0.488 2. DBC 24 0.5033 0.0678 13.47 0.313-0.612 3. WD 24 0.1591 0.2063 16.53 0.107-0.212 4. LF 24 0.5627 0.0793 14.09 0.433-0.740 5. WF 24 0.2571, : 0.042852 16.53, 2.0.133=0.333 6. AF 24 3:55 0.48 14.45 3-4 T A TS 24 0.1246 0.0108 8.67 0.105-0.145 8. AW 24 0.0718 0.0070 9.75 | 0.063-0.093 9. ADB 24 0.2457 0.0255 10.38 0.208-0.295 10. AAB 24 0.2376 0.0246 10.35 0.188-0.290 11. ABB 24 0.2981 0.0645 21.64 0.137-0.425 12. DN 24 0.0969 0.0144 14.86 0.073-0.132 14. SNB 24 0.4867 0.1097 22.54 0.317-0.655 15. WK 24 0.0099 0.0015 15.15 0.008-0.013 18. WP 24 0.0170 0.0091 11.18 0.014-0.022 21. RSL 24 0.1128 0.0347 30.76 0.063-0.167 22. RSS 24 0.0383 0.0131 34.20 0.027-0.088 23. SSL 24 0.5790 0.2514 43.42 0.206-1.047 24. SSS 24 0.0767 0.0239 31.16 0.042-0.141 32. TRW 24 0.0080 0.0020 25.00 0.005-0.011 33. TLW 24 0.0070 0.0010 14.29 0.005-0.009 34. FWT 24 0.0432 0.0194 44.91 0.019-0.084 35. RWT 24 0.0650 0.0353 54.22 0.018-0.131 36. CL 24 0.1979 0.0063 3.18 0.189-0.210 3 CD 24 0.1592 0.0062 3.89 0.146-0.175 38. MAW 24 0.1338 0.0082 6.13 0.116-0.146 39. MIW 24 0.0967 0.0069 7.14 0.086-0.112 40. VD 24 0.0494 0.0115 23.28 0.036-0.072 41. RA 24 67.79 4.42 6.52 59-77 42. LA 24 DIES 3.96 15.65 18-34 43. TB 24 0.3083 0.0365 11.84 0.259-0.378 had a great effect on polypide feeding. Species composition.—Three species are assigned to this genus: A. foramenmajor, n. sp., A. crassata, n. Sp., and A. venusta, n. sp. Range.—Lower Mississippian (Valmeyeran); pres- ent in the Keokuk, Warsaw, Salem and St. Louis for- mations. Text-figure 14.— Apertostella crassata illustrated. 1, diagrammatic longitudinal section illustrating changing chamber outline from deep section near middle of branch (bottom of figure) to shallow section near abaxial edge of branch (top of figure) [Observe lack of hemisepta characteristic of this genus.], x 70; 2, diagrammatic tangential section illustrating changing chamber outline from deep section near reverse- wall budding-site (bottom of figure) to shallow section near obverse surface (top of figure) [Typical ovate aperture opening is shown (arrow).], x 70; 3, diagrammatic transverse section across branch, x 70; 4, reconstruction of typical chamber shape (three-dimensional) as viewed from distal end of branch; chamber reconstructed is from the right side of branch, x 140; 5, reconstruction of typical chamber shape (three-dimensional) as viewed from abaxial edge of branch, x 140; 6, reconstruction of typical chamber shape (three-dimension- al) as viewed from obverse surface; chamber reconstructed is from the right side of branch [Observe slight displacement of aperture opening toward abaxial edge of chamber.], x 140. MISSISSIPPIAN BRYOZOANS: SNYDER 99 Apertostella foramenmajor, new species Plate 35, figures 1-12, Plate 36, figures 1-3; Table 29 Etymology of name.— Named for the relatively large apertural openings that characterize the species. Diagnosis. — Zoarium robustness intermediate, mesh Spacing lower-end intermediate, pattern regular; branch robustness intermediate, width lower-end intermedi- ate, depth lower-end medium; branches straight to broadly curved toward zoarial edge; transversely asym- metrically ovate, flattened on obverse surface, branch- es moderately closely spaced and joined at regular in- tervals by thin to lower-end intermediate width, relatively short dissepiments. Fenestrule size inter- mediate; shape more elliptical on obverse, more rect- 100 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 angular on reverse surface, regular. Autozooecial ap- erture size upper-end intermediate, large relative to branch width, shape ovate, elongate proximodistally; surrounded by thin, extremely well-developed com- plete peristome; three to four (most commonly three) apertures per fenestrule. Single narrow, continuous keel; straight to slightly sinuous, extending along middle of obverse branch surface, atop which are positioned in- termediate-size, ovate nodes. Autozooecial chamber size lower-end intermediate, chambers emplaced in two rows, except third row at sites of branch bifurca- tion; outline rounded triangular to irregularly pentag- onal near reverse wall, becoming angularly pentagonal toward mid chamber; from mid chamber toward ob- verse surface, chamber shape rectangular to elliptical, irregularly elliptical near obverse surface. Chambers elongate proximodistally, parallel to reverse wall. Ap- erture at distal-abaxial end of chamber, connected to chamber by short vestibule of highly variable length. Superior and inferior hemisepta both absent. Lateral- wall budding-angle moderately variable (mean of 25°); reverse-wall budding-angle highly constant (mean of 68°). Table 29 presents statistical criteria used in delim- iting this species. Exterior description.—Zoarium robustness inter- mediate, expansion flat, exhibiting little or no obverse or reverse curvature in zoarial fragments examined, fan-shaped; mesh spacing lower-end intermediate; slight to moderate astogenetic thickening of both ob- verse and reverse zoarial skeleton; external zoarial pat- tern regular. Probable mature widths 20 to 25 mm, lengths 30 to 40 mm. Branch robustness intermediate, width lower-end intermediate, moderately variable; most frequently straight, lateral branches broadly curved toward edge of zoarium. Branch spacing moderately close, distance between adjacent branch centers regular. Obverse sur- face texture smooth to slightly granular, becoming in- creasingly granular with astogeny; surface flat or very slightly rounded, except for presence of single keel; keel narrow, well-developed, continuous, straight to slight- ly sinuous, extending along branch midline and curv- ing around autozooecial apertures; keel causing slight positive inflection in obverse surface profile. Keel cov- ered during astogenetic thickening of lamellar skeleton, most prominent toward proximal end of zoarium. Nodes monoserially emplaced, well-developed, inter- mediate in size, shape ovate, elongate proximodistally; moderately regular in both size and shape; nodes de- velop as extensions from middle of keel; two to three (most commonly two) nodes per fenestrule length; spacing intermediate, moderately regular; slight to moderate increase in node diameter with astogeny. Re- verse surface texture granular, coarsening with asto- geny, bearing an intermediate number of moderately closely spaced longitudinal striae, evident in exterior view at most distal end of zoarium, becoming covered by astogenetically thickened lamellar skeleton toward proximal end of zoarium; large microstylets positioned atop striae, emplaced in rows, closely spaced; micro- stylets highly variable in size and placement, increasing in diameter and becoming more irregularly positioned across reverse branch surface with astogeny. Large, approximately circular macrostylets, variable in Size, moderately regular in shape, highly variable in place- ment, most commonly located at or near sites of branch-dissepiment junction. Autozooecia in two rows . across branch, except third row at sites of branch bi- furcation where middle autozooecium evidently shared by both branches, very slight thickening of branch proximal, thinning distal to sites of branch bifurcation. Heterozooecia absent in zoarial fragments analyzed. Dissepiments of thin to lower-end intermediate width, width approximately equal to half that of branch, moderately variable in width; relatively short in length, moderately constant; connect branches at regular in- tervals. Dissepiments barlike, with slight medial thin- ning and flaring at branch-dissepiment contact; mod- erately recessed from obverse surface, approximately even with reverse. Moderate astogenetic thickening of dissepiments, most pronounced toward proximal end of zoarium. Obverse dissepiment surface with two to five longitudinal striae across dissepiment oriented perpendicular to branch length; reverse dissepiment surface with one well-developed, medially located, thickened bar oriented perpendicular to branch length extending across dissepiments; dissepiments highly an- gular toward distal end of zoarium, becoming rounded toward proximal end with astogeny; rows of small sty- lets occurring atop reverse dissepiment bar, stylets in- crease in diameter and become more irregularly po- sitioned with astogeny. Surface texture similar to respective branch surface; obverse smooth to slightly granular, reverse granular; both surfaces coarsening with astogeny. Emplacement of dissepiments ranging from perpendicular to branch length to 20? from perpendic- ular. Apertures commonly open on proximal or distal edge, or in middle of dissepiment edge at branch-dis- sepiment contact; arranged symmetrically or asym- metrically between branches. Fenestrule size intermediate; shape rectangular to elliptical, becoming increasingly elliptical with asto- geny, elongate proximodistally; regular in size and shape; slight expansion of width and length in obverse- reverse direction, shape more elliptical from obverse surface, more rectangular from reverse. Mean width of fenestrule approximately two-thirds branch width; slight decrease in fenestrule opening toward proximal end of zoarium due to astogenetic thickening of la- MISSISSIPPIAN BRYOZOANS: SNYDER 101 mellar skeleton. Ratio of fenestrule mean width to length approximately 1:2; width and length both mod- erately constant. Three to four (most commonly three) apertures per fenestrule length; distance between clos- est aperture centers along branch and across branch approximately equal, spacing of aperture centers across fenestrule 1.3 times greater; spacing along and across branch constant, spacing across fenestrule moderately variable. Autozooecial aperture size upper-end intermediate, large relative to branch width; apertures ovate, elon- gate proximodistally, width to length ratio approxi- mately 4:7; size and shape moderately uniform; open- ing orientation most commonly ata slight angle toward fenestrule, more rarely parallel to plane of obverse sur- face; surrounded by thin, extremely well-developed, Complete peristome; peristome exhibiting slight thin- ning at proximal end. Aperture margins exhibiting no or slight extension into fenestrule, the latter causing very slight inflections in fenestrule outline on obverse surface. Centrally thickened terminal diaphragms pres- ent, rare; most common at proximal end of zoarium. Zoarial supports develop as extensions of reverse Zoarial surface and lateral edge of zoarium, moderately Tare in occurrence. Interior description. — Branches asymmetrically ovate in transverse section, flattened and slightly enlarged on Obverse surface, elongate parallel to plane of zoarial Surface. Branches lower-end medium, highly regular in depth. Autozooecial living chamber size lower-end inter- mediate, chambers arranged in alternating rows along Planar axial wall; axial wall highly sinuous, extending toward and connecting with chamber lateral walls near Ieverse wall of zoarium, becoming relatively straight With only slight inflections toward lateral walls in mid Chamber and near obverse surface. Chamber longest dimension paralleling reverse wall in proximodistal direction. Autozooecial chamber outline rounded tri- angular to irregularly pentagonal near reverse wall, be- Coming more angularly pentagonal toward mid cham- ber; from mid chamber toward obverse surface, chamber shape rectangular to elliptical; in shallow ob- verse section, chamber becomes irregularly elliptical, Slightly enlarged at distal-abaxial end; chamber shape highly uniform. Aperture positioned at distal-abaxial €nd of chamber, connected to chamber by short, poorly developed, highly variable length vestibule. Ratio of autozooecial chamber minimum width to maximum Width approximately 3:4; maximum width to depth Tatio 5:6; ratio of depth to length of chamber approx- imately 4:5; chamber length and depth slightly more Constant than minimum and maximum widths, all di- Mensions highly constant. Superior and inferior hem- Isepta both absent. Autozooecial chambers diverge lat- erally from middle of branch at variable angle (mean of 25°); from reverse wall at a highly uniform angle (mean of 68°). Three-dimensionally reconstructed chamber form a rectangular box; length as viewed from lateral edge of branch; depth as viewed from distal end of branch slightly greater than width as viewed from obverse surface. Internal granular skeletal layer thin to intermediate, continuous with obverse nodes, keel, peristome, and dissepiment striae; reverse longitudinal striae, micro- stylets and macrostylets; across dissepiments and in the middle of zoarial supports. Outer lamellar layer thickness intermediate, exhibiting slight to moderate astogenetic thickening, most pronounced toward prox- imal end of zoarium. Remarks.—The exterior pattern of Exfenestella ex- igua (Ulrich, 1890) is very similar to that of Aperto- stella foramenmajor, n. sp. However, A. foramenmajor has a much smaller chamber than does E. exigua, lacks hemisepta (whereas the latter has both superior and inferior hemisepta), and has chambers whose length is parallel to the reverse wall rather than having the long- est chamber dimension paralleling the lateral chamber walls, as in E. exigua. This species-pair provides yet another example of taxonomic problems that can result from excessive reliance on specimen exteriors. A. foramenmajor is distinguished from other species of Apertostella by a larger chamber and aperture open- ings that are large relative to branch width. Interior chamber dimensions are highly characteristic for spe- cies of Apertostella. Material studied. — Twenty-two exterior fragments, five sectioned specimens; largest zoarial fragment 20x28 mm (width to length). Although microstruc- turally unaltered, many zoarial fragments are crushed due to compaction of shales. Occurrence.— Apertostella foramenmajor is moder- ately common at the Keokuk and Warsaw localities. It occurs as far south as Jerseyville, and is most fre- quently found in shales, although some fragments oc- cur in biocalcarenites. Holotype.—UI X-6766 (loc. 11, sample 53). Paratypes.—UI X-6745 (loc. 11, samples 53, 57), 6721, 6722, 6770 (loc. 10, samples 28, 33). Apertostella crassata, new species Plate 36, figures 4-9, Plate 37, figures 1-9; Text-figure 14; Table 30 Etymology of name.— The species name refers to the closely spaced mesh and small fenestrule openings characteristic of this species. Diagnosis.— Zoarium robust, mesh spacing ex- tremely close, pattern highly regular; branches mod- erately robust, width intermediate, moderately deep in 102 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 thickness, straight to sinuous, broadly curved at lateral zoarial edge; transversely irregularly polygonal to ap- proaching ovate, very closely spaced and joined at highly regular intervals by intermediate-width, short dissepiments. Fenestrule size small; shape ovate on obverse surface, becoming elliptical on reverse, mod- erately regular. Autozooecial aperture size upper-end intermediate, shape ovate, highly elongate proximo- abaxially; surrounded by thin, intermediately devel- oped, complete peristome; two to three (most com- monly three) apertures per fenestrule. Single moderately narrow, continuous keel; straight to slightly anasto- mosing, extending along middle of obverse branch sur- face, atop which are positioned intermediate-size ovate nodes. Autozooecial chamber size lower-end inter- mediate, chambers emplaced in two rows, except third row at sites of branch bifurcation, rarely three rows for short distances proximal to sites of branch bifurcation; outline irregular rounded-triangular to polygonal near reverse wall, rapidly becoming irregularly pentagonal in mid and throughout most of chamber, ovate to el- liptical in shape near obverse surface. Chambers elon- gate parallel to reverse wall in proximodistal direction. Aperture at distal-abaxial end of chamber, connected to chamber by intermediate-length vestibule; vestibule length variable. Superior and inferior hemisepta both absent. Lateral-wall budding-angle variable (mean of 22°); reverse-wall budding-angle constant (mean of 67°). Table 30 presents statistical criteria used in delim- iting this species. Exterior description.—Zoarium robust, expansion flat to slightly undulating, fan-shaped; mesh spacing extremely close; pronounced astogenetic thickening of both obverse and reverse zoarial skeleton; external zoarial pattern highly regular. Probable mature widths 40 to 50 mm, lengths up to 60 mm. Branches moderately robust, width intermediate, constant; straight to slightly sinuous in trace, with in- flections toward sites of dissepiment insertion, lateral branches commonly broadly curved toward edge of zoarium. Branch spacing very close, distance between adjacent branch centers highly regular. Obverse surface texture slightly granular, remaining texturally the same throughout astogeny; surface regularly angular to slightly rounded, except for presence of single keel; keel moderately narrow, well-developed, continuous, straight to slightly anastomosing extending along branch midline and causing moderate positive inflection in obverse surface profile. Keel becomes covered by la- mellar skeleton during astogeny. Nodes monoserially emplaced, poorly developed, intermediate in size, highly ovate, elongate proximodistally; regular in both size and shape; develop as projections from middle of keel; one to two per fenestrule length, spacing inter- mediate, constant; nodes partially to completely cov- Table 30.—Summary numerical analysis of Apertostella crassata, n. sp. For explanation of abbreviations of characters (left column), see Table 8b (foldout inside back cover). number of mea- coeffi- sure- standard cient of observed ments mean deviation variation range 1. WB 24 0.3471 0.0436 12.56 0.283-0.480 2. DBC 24 0.5067 0.0536 10.58 0.413-0.603 3. WD 24 0.2976 0.0475 15.96 0.191-0.410 4. LF 24 0.4053 0.0680 16.78 0.238-0.505 5. WF 24 0.1567 0.0206 17.05 0.125-0.200 6. AF 24 2.83 0.38 13.44 2-3 7 AL 24 0.1401 0.0069 4.93 0.127-0.154 8. AW 24 0.0962 0.0046 4.78 | 0.086—0.108 9. ADB 24 0.2158 0.0167 7.74 0.184-0.253 10. AAB 24 0.2218 0.0190 8.57 0.192-0.262 11. ABB 24 0.2970 0.0351 11.82 0.228-0.365 12. DN 24 0.0852 0.0122 14.32 0.069-0.115 14. SNB 24 0.3761 0.0574 15.26 0.239-0.464 15. WK 24 0.0470 0.0087 18.51 0.039-0.068 18. WP 24 0.0090 0.0021 23.80 0.005-0.012 22. RSS 24 0.0087 0.0020 23.09 0.006-0.011 24. SSS 24 0.0286 0.0109 38.11 0.018-0.060 32. TRW 24 0.0093 0.0020 21.51 0.005-0.013 33. TLW 24 0.0081 0.0019 22.96 0.006-0.102 34. FWT 24 0.0594 0.0222 37.37 0.029-0.143 35. RWT 24 0.1208 0.0616 50.99 0.034-0.280 36. CL 24 0.2015 0.0070 3.47 0.189-0.214 37. CD 24 0.1767 0.0072 4.07 0.165-0.193 38. MAW 24 0.1363 0.0177 12.997 702) 15-07195 39. MIW 24 0.0764 0.0141 18.46 0.052-0.104 40. VD 24 0.0661 0.0115 17.40 0.051-0.091 41. RA 24 67.04 5.84 8.71 53-78 42. LA 24 21.58 3.50 16:22 17-31 43. TB 24 0.4157 0.0715 17.20 0.326-0.587 ered by lamellar skeleton with astogeny. Reverse sur- face texture granular, coarsening with astogeny, bearing few rows of widely spaced longitudinal striae, evident in exterior view at most distal end of zoarium, becom- ing covered immediately proximal from zoarial distal edge due to astogenetic thickening of lamellar skeleton; rows of very small microstylets develop atop longi- tudinal striae; microstylets closely spaced, become variably positioned across entire reverse surface and exhibit slight increase in diameter with astogeny. Au- tozooecia in two rows across branch; except third row at sites of branch bifurcation where middle autozooe- cium evidently shared by both branches, rarely three rows for short distances proximal to sites of branch bifurcation; pronounced thickening proximal, thinning distal to sites of branch bifurcation. Heterozooecia ab- sent in all zoarial fragments examined. Dissepiments of intermediate width, approximately seven-eighths width of branch, moderately constant; short in length, constant; connect branches at highly regular intervals. Dissepiments thin medially, exhibit pronounced flaring at branch-dissepiment contact; MISSISSIPPIAN BRYOZOANS: SNYDER 103 highly recessed from obverse, approximately even with reverse surface. Moderate to pronounced astogenetic thickening of dissepiments toward proximal end of zoarium. Obverse dissepiment surface lacking orna- Mentation; reverse surface with longitudinal striae ori- ented perpendicular to branch length atop which are Positioned small stylets; striae covered and stylets in- crease in diameter, become more irregularly positioned with astogeny. Obverse dissepiment surface texture Slightly granular, remaining the same with astogeny; teverse surface texture granular, coarsening with as- togeny. Emplacement of dissepiments ranging from Perpendicular to branch length to angles deviating up to 20° from perpendicular. Apertures commonly po- Sitioned on proximal or distal edge or in middle of dissepiment edge at branch-dissepiment contact; ar- ranged symmetrically or asymmetrically between branches. Fenestrule size small; shape ovate on obverse sur- face, becoming elliptical on reverse, elongate proxi- modistally; moderately regular in size and shape; slight to moderate expansion of fenestrule width and length in obverse-reverse direction. Mean width of fenestrule Slightly less than half branch width on obverse surface, greater than half branch width on reverse; fenestrule Opening decreasing in size, becoming appreciably Smaller to completely closed toward proximal end of Zoarium with astogenetic thickening of lamellar skel- eton. Ratio of fenestrule mean width to length ap- Proximately 3:10; width slightly more constant than length, both moderately constant. Two to three (most commonly three) apertures per fenestrule length; dis- tance between closest aperture centers along branch and across branch approximately equal; distance be- tween apertures across fenestrule approximately 1.35 times greater; spacing along and across branch con- Stant, spacing across fenestrule slightly variable. Autozooecial aperture size upper-end intermediate, Shape ovate, highly elongate proximoabaxially, width to length ratio approximately 2:3; size highly uniform, Shape moderately uniform; opening most commonly Oriented parallel to plane of obverse surface, rarely at Slight angle toward fenestrule; thin, intermediately de- veloped complete peristome surrounding aperture. No extension of aperture margin into fenestrule, apertures even with obverse branch surface. Thin, uniform thick- ness terminal diaphragms cover some apertures, most Common near proximal end of zoarium. _ Zoarial supports develop near proximal end of zoar- lum, form as extension of lateral zoarial edge and re- verse zoarial surface. Interior description.—Branches irregularly polygo- Nal to approaching ovate in transverse section, irreg- ular shape due to astogenetic thickening of lamellar Skeleton; branches commonly slightly flaring on ob- verse surface, elongate either in obverse-reverse di- rection or parallel to plane of obverse surface. Branches moderately deep, variable in thickness. Autozooecial chamber size lower-end intermediate, chambers biserially arranged in alternating rows along planar branch axial wall; axial wall sinuous, anasto- mosing toward sites of lateral-wall emplacement near reverse wall, becoming relatively straight, exhibiting slight inflections toward lateral walls from mid cham- ber to obverse surface. Chamber longest dimension only slightly greater than depth, elongate parallel to reverse wall in proximal-distal direction. Autozooecial chamber outline irregular, rounded triangular to po- lygonal near reverse wall; rapidly becoming irregularly pentagonal in shape throughout mid chamber and to- ward obverse surface; ovate to elliptical in shape near obverse surface, slightly enlarged at distal end; cham- ber shape moderately uniform. Aperture positioned at distal-abaxial end of chamber, connected to chamber by well-developed, intermediate-length vestibule; ves- tibule length variable. Ratio of autozooecial chamber minimum width to maximum width approximately 5:9; maximum width to depth ratio about 7:9; depth to length ratio about 7:8. Superior and inferior hemi- septa both absent. Autozooecial chambers diverge lat- erally from middle of branch at a variable angle (mean of 22°); from reverse wall at a constant angle (mean of 67°). Three-dimensionally reconstructed chamber form a rectangular box; length as viewed from lateral edge of branch; depth as viewed from distal end of branch, and width as viewed from obverse surface. Internal granular layer width intermediate, well-de- veloped; continuous with obverse nodes, keel, and per- istome; reverse longitudinal striae and microstylets; across dissepiments and in the middle of zoarial sup- ports. Outer lamellar skeletal layer usually thick, ex- hibiting pronounced astogenetic thickening on both obverse and reverse exterior surfaces, most pro- nounced thickening occurring at proximal end of zoar- ium. Remarks.—The robust fan, close mesh, and small fenestrule openings allow relatively easy exterior rec- ognition of Apertostella crassata, n. sp. Although ex- teriors of this species are similar to those of species of Hemitrypa Phillips, 1841, A. crassata is readily as- signed to Apertostella by its lack of exterior secondary reticulate structure, difference in fenestrule shape and size, and interior characters such as autozooecial chamber size and shape. A. crassata is distinguished from other species of Apertostella by having the largest chamber size, most closely spaced mesh, fewest number of apertures per fenestrule, and largest size aperture opening. All species of Apertostella have extremely similar reverse-wall and lateral-wall budding-angles, characters extremely con- stant within this genus. Material studied. — Twenty-eight exterior fragments; four sectioned specimens; largest zoarial fragment 30x38 mm (width to length). The robust fan in this species resulted in the collection of many large, nearly complete zoarial fragments. The preservation of frag- ments is also good, although some colonies have been crushed by shale compaction. Occurrence.— Apertostella crassata is present in the Warsaw Formation and Upper Keokuk Formation in the northern half of the study area. It is most common near Keokuk, Iowa and Warsaw, Illinois, but occurs as far south as White Hall, and is found in both lime- stones and shales. Holotype.—UI X-6737 (loc. 10, sample 28). Paratypes.—UI X-6738-6740 (loc. 10, samples 28, 35). Apertostella venusta, new species Plate 38, figures 1-9, Plate 39, figures 1-5; Table 31 Etymology of name.—Name refers to the pleasing exterior appearance of this species. Diagnosis.—Zoarium delicate, mesh spacing upper- end intermediate, pattern moderately regular; branch- es robust, width lower-end wide, medium in thickness; straight to broadly curved toward lateral zoarial edge; transversely irregularly ovate to elliptical, flattened or slightly concave on obverse surface, intermediately spaced and joined at highly regular intervals by inter- mediate width and length dissepiments. Fenestrules large; shape elliptical to approaching rectangular, mod- erately constant. Autozooecial aperture size interme- diate, ovate, elongate proximodistally; surrounded by thin, well-developed, complete peristome with very small stylets projecting from peristome outer edge; five to six apertures per fenestrule. Single intermediate- width, continuous keel, straight to slightly sinuous, ex- tending along middle of obverse branch surface, atop which are positioned lower-end large size, circular or ovate nodes. Autozooecial chamber size intermediate, chambers emplaced in two rows, except either third row at sites of branch bifurcation or three rows for short distances along branch proximal to sites of branch bifurcation; outline rounded triangular near reverse wall, rapdily becoming irregularly pentagonal through- out mid chamber, irregularly elliptical near obverse surface with ellipse elongate distal-abaxially. Cham- bers elongate parallel to reverse wall in proximodistal direction. Aperture at distal-abaxial end of chamber, connected to chamber by short, variable-length ves- tibule. Superior and inferior hemisepta both absent. Lateral-wall budding-angle slightly variable (mean of 22°); reverse-wall budding-angle highly constant (mean of 69°). PALAEONTOGRAPHICA AMERICANA, NUMBER 57 Table 31.—Summary numerical analysis of Apertostella venusta, n. sp. For explanation of abbreviations of characters (left column), see Table 8b (foldout inside back cover). number of mea- coeffi- sure- standard cient of observed ments mean deviation variation range 1. WB 24 0.3952 0.0673 17.03 0.298-0.556 2. DBC 24 0.7297 0.1884 25.82 0.375-1.081 3. WD 24 0.2651 0.0567 21.39 —07173-0:365 4. LF 24 1.3480 0.1525 11.31 1.125-1.556 5. WF 24 0.4292 0.0833 19.41 0.300-0.600 6. AF 24 5.67 0.49 8.68 5-6 7. AL 24 0.1211 0.0094 7.76 0.098-0.148 8. AW 24 0.0746 0.0072 9.65 0.058-0.088 9. ADB 24 0.2956 0.0312 10.55 0.250-0.356 10. AAB 24 0.3145 0.0346 11.00 0.253-0.375 11. ABB 24 0:4775- . 0.1010 21.15 © 0:325-0.650 12. DN 24 0.1282 0.0208 16.22 0.015-0.275 14. SNB 24 1.2780 0.3285 25.70 0.790-1.920 15. WK 24 0.0606 0.0121 19.97 0.042-0.085 16. DSO 24 0.0382 0.0161 42.15 0.019-0.068 17. SSO 24 0.0685 0.0333 48.61 0.041-0.104 18. WP 24 0.0231 0.0048 20.78 0.015-0.030 22. RSS 24 0.0138 0.0039 28.26 0.012-0.028 24. SSS 24 0.0310 0.0106 34.19 0.023-0.078 32. TRW 24 0.0204 0.0032 15.69 0.014-0.027 33. TLW 24 0.0152 0.0028 18.42 0.011-0.020 34. FWT 24 0.0528 0.0192 36.36 0.025-0.085 35. RWT 24 0.0688 0.0324 48.55 0.024-0.154 36. CL 24 03555: 320101777. 4.97 0.338-0.371 37. CD 24 0.1743 0.0114 6.54 0.156-0.193 38. MAW 24 0.1636 0.0133 8.13 0.144-0.191 39. MIW 24 0.1028 | 0.0213 20.72 0.075-0.148 40. VD 24 0.0582 0.0167 28.69 0.035-0.088 41. RA 24 69.08 4.48 6.49 62—76 42. LA 24 22.42 3.34 14.91 8-29 43. TB 24 0.3583 0.0855 23.86 0.214-0.525 Table 31 presents statistical criteria used in delim- iting this species. Exterior description.—Zoarium delicate, expansion flat to slightly obversely curved, fan-shaped; mesh spacing upper-end intermediate; moderate astogenetic thickening of both obverse and reverse zoarial skele- ton; external zoarial pattern moderately regular. Prob- able mature widths 30 to 40 mm, lengths up to 50 or 60 mm. ; Branches robust, width lower-end wide, moderately variable; straight to broadly curved toward lateral edge of zoarium. Branch spacing intermediate, distance be- tween adjacent branch centers irregular. Obverse branch surface texture granular, becoming increasingly so with astogeny; surface flat to slightly concave, except for presence of single, intermediate-width keel; keel mod- erately well-developed, continuous, straight to slightly sinuous, extending along branch midline and causing slight positive inflection in obverse surface profile. Slight astogenetic thickening of keel, with keel becom- ing covered by lamellar skeleton during astogenetic MISSISSIPPIAN BRYOZOANS: SNYDER 105 thickening of obverse surface. Nodes monoserially em- Placed, well-developed, size lower-end large; shape cir- cular to ovate, elongate proximodistally; moderately constant in both size and shape; nodes develop as pro- Jections from middle of keel; most commonly one, more rarely two nodes per fenestrule length; nodes widely, unevenly spaced; moderate increase of node diameter with astogeny. Large, highly variable size sty- lets irregularly positioned across obverse surface; sty- lets exhibiting slight astogenetic thickening. Reverse Surface texture granular, becoming more coarsely so with astogeny; bearing numerous rows of closely spaced longitudinal striae which become partially covered by astogenetic thickening of lamellar skeleton; rows of small, closely spaced microstylets develop as exten- Sions of longitudinal striae; microstylets become vari- ably spaced across entire reverse surface and exhibit Slight increase in diameter with astogeny. Autozooecia in two rows across branch; except either third row at Sites of branch bifurcation where middle autozooecium €vidently shared by both branches or three rows for Short distances along branch proximal to sites of branch bifurcation; slight thickening proximal, thinning distal to sites of branch bifurcation. Heterozooecia absent in all zoarial fragments obversed. Dissepiments of intermediate width, approximately two-thirds that of branch, slightly variable in width; length intermediate, slightly constant; connect branch- €s at highly regular intervals. Dissepiments moderately barlike, exhibiting slight medial thinning and slight flaring at branch-dissepiment junction; highly recessed from obverse surface, slightly recessed from reverse. Slight astogenetic thickening toward proximal end of Zoarium. Obverse dissepiment surface with four to six longitudinal striae oriented perpendicular to branch length, large stylets similar in size to obverse stylets Positioned across dissepiment surface not covered by Striae; striae partially covered by astogenetic thicken- ing of lamellar skeleton, stylets increase in diameter with astogeny; reverse surface bearing numerous rows of longitudinal striae oriented perpendicular to branch Width, rows of closely spaced small stylets atop striae; Striae become covered by secondary lamellar thick- ening, stylets increase in diameter and become more irregularly positioned across dissepiment surface with astogeny. Both obverse and reverse dissepiment sur- faces granular in texture, becoming increasingly so with astogeny. Emplacement of dissepiments perpendicular Or approximately perpendicular to branch length. Ap- €rtures commonly positioned on proximal or distal edge or in middle of dissepiment edge at branch-dis- Sepiment contact; arranged symmetrically or asym- Metrically between branches. Fenestrules large, shape elliptical to approaching rectangular, highly elongate proximodistally; shape moderately constant, size slightly constant; opening constant in size and shape on both obverse and reverse surfaces. Mean width of fenestrule slightly greater than branch width; astogenetic thickening, primarily toward proximal end of zoarium, causing slight infilling of fenestrule opening. Ratio of mean fenestrule width to length approximately 1:3; length moderately constant, width slightly variable. Five to six apertures per fe- nestrule length; distance between closest aperture cen- ters along branch and across branch approximately equal, spacing of apertures across fenestrule 1.5 times greater; spacing along and across branch slightly vari- able, spacing across fenestrule highly variable. Autozooecial aperture size intermediate, shape ovate, elongate proximodistally, width to length ratio 3:5; size highly uniform, shape variable; opening at a slight an- gle toward fenestrule or parallel to plane of obverse surface; thin, well-developed complete peristome sur- rounding aperture, commonly with very small stylets irregularly projecting from peristome outer edge. Ap- erture margins extend into fenestrule, causing very slight inflections in fenestrule outline on obverse surface. Terminal diaphragms lacking. Zoarial supports rare, observed at most proximal reverse side and lateral zoarial edges. Interior description. — Branches irregularly ovate to elliptical in transverse section, frequently flattened or slightly concave on obverse surface, enlarged on ob- verse surface, elongate parallel to plane of zoarial sur- face. Branches medium in thickness, variable. Autozooecial living chambers intermediate in size, biserially arranged in alternating rows along planar branch axial wall; axial wall zigzags, extending diag- onally across entire branch near reverse chamber wall; sinuous, anastomosing toward and connecting with chamber lateral walls throughout the rest of chamber. Chamber longest dimension paralleling reverse wall in proximodistal direction. Autozooecial chamber out- line rounded triangular near reverse wall; rapidly be- coming irregularly pentagonal throughout all but most obverse end of chamber where chamber becomes ir- regularly elliptical in shape, ellipse elongate distal- abaxially relative to branch length; chamber shape moderately uniform. Apertures positioned at distal- abaxial end of chamber, connected to chamber by short, moderately well-developed, variable-length vestibule. Ratio of autozooecial chamber minimum width to maximum width approximately 5:8; chamber depth slightly less than maximum chamber width, ratio about 15:16; ratio of chamber depth to length approximately 2:3; chamber length, depth and maximum width highly constant, minimum width highly variable. Superior and inferior hemisepta both absent. Autozooecial chambers diverge laterally from middle of branch at a slightly variable angle (mean of 22°); from reverse wall 106 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 at a highly constant angle (mean of 69°). Three-dimensionally reconstructed chamber form an irregular rectangular box; length as viewed from lateral edge of branch; depth and width approximately equidimensional, as viewed from distal end of branch and obverse surface, respectively. Internal granular skeletal layer relatively thick, well- developed; continuous with obverse nodes, keel, sty- lets, and peristome; reverse longitudinal striae and sty- lets; across dissepiments and in the middle of zoarial supports. Moderate astogenetic thickening of lamellar skeletal layer, most pronounced toward proximal end of zoarium. Remarks.— Apertostella venusta, n. sp. is distin- guished from other species of the genus by a coarser mesh, much greater number of apertures per fenestrule length, obverse stylets, wider branches, and much larg- er autozooecial chambers. The open mesh in A. venusta is not typical of Apertostella, but the chamber shape, large aperture size relative to branch width, and lateral- wall and reverse-wall budding-angles are typical of this genus. The relatively rare occurrence and frequent poor preservation of this species may account for its not being recognized by Ulrich in his extensive work on the Mississippian bryozoans around Keokuk, Iowa and Warsaw, Illinois. Material studied. — Fourteen exterior fragments; four sectioned specimens; largest zoarial fragment 22x31 mm (width to length). Microstructurally most material is well-preserved, although mechanical crushing of fragments is common due to compaction of muds in shale development. Occurrence.— Apertostella venusta, n. sp. is extreme- ly rare in the Upper Keokuk and Warsaw formations in localities from Mt. Sterling to Keokuk. It is most commonly found in shale beds on the surfaces of thin limestone lenses. Holotype.— UI X-6875 (loc. 10, sample 33). Paratypes.—UI X-7028-7030 (loc. 10, samples 25, 28). Genus HEMITRYPA Phillips, 1841 Type species.— Hemitrypa oculata Phillips, 1841 [Devonian of England]. Typical Warsaw species.— H. perstriata Ulrich, 1890, p. 564, pl. 57, figs. 6, 6a [Keokuk Group: Bentonsport and Keokuk, Iowa]. Diagnosis.— Zoarium robustness delicate to robust, mesh spacing close to intermediate; reticulate mesh- work present, developed as extension of keel across obverse zoarial surface; chamber outline an irregular pentagon, rectangle to parallelogram in mid tangential section; chamber size intermediate; aperture size in- termediate to large; hemisepta absent; chamber re- verse-wall budding-angle varies between 60? and 70? (means). Three-dimensionally reconstructed chamber form an irregular rectangular to cubic box. Description.—Zoarium robustness delicate to ro- bust, expansion flat, undulating to obversely or re- versely curved, mesh spacing close to intermediate, regular to variable; reticulate meshwork present, de- velops as extension of keel and extends across obverse zoarial surface in middle and at proximal ends of the zoarium. Branch width narrow to intermediate, straight to sinuous in trace with lateral branches broadly curved toward edge of zoarium; branch surface profile round- ed to angular. Keel present, single, width intermediate, exhibiting pronounced astogenetic thickening, deve- loping into reticulate meshwork with, astogeny. Nodes present, emplacement monoserial, size intermediate, shape stellate, ovate to circular, located atop keel, spac- ing close to intermediate. Obverse stylets present, size small to intermediate, occurring across obverse sur- face. Microstylets present, ranging in size from inter- mediate to large. Macrostylets present in some species, size intermediate to large, located at branch-dissepi- ment junction or irregularly across reverse branch sur- face. Autozooecia in two rows, third row at sites of branch bifurcation or three to four rows for moderate distances proximal to branch bifurcation. Heterozooe- cia (ovicells?) present in some species. Dissepiments of intermediate width, length short to intermediate, connect branches at regular to variable intervals. Fenestrule size small to intermediate; shape ellipti- cal, ovate to rarely circular on obverse, rectangular, square to polygonal on reverse zoarial surfaces. Aperture size intermediate to large, shape elliptical, ovate to rarely circular, oriented parallel to plane of Text-figure 15.— Hemitrypa perstriata illustrated. 1, diagrammatic longitudinal section showing changing chamber outline from deep section near middle of branch (bottom of figure) to shallow section near abaxial edge of branch (top of figure) [Observe reticulate mesh- work (arrow) characteristic of this genus and composed of granular skeletal material], X 70; 2, diagrammatic tangential section illus- trating changing chamber outline from deep section near reverse- wall budding-site (bottom of figure), to shallow section of chambers (middle of figure), to view of reticulate meshwork (arrow) in the most shallow section (top of figure) [Each chamber in the meshwork cor- responds to an underlying aperture opening.], x 70; 3, diagrammatic transverse section across branch illustrating typical aperture orien- tation to plane of obverse surface (arrow) and reticulate meshwork covering obverse surface, x 70; 4, reconstruction of typical chamber shape (three-dimensional) as viewed from abaxial edge of branch [Observe the well-developed, long vestibule.], x 140; 5, reconstruc- tion of typical chamber shape (three-dimensional) as viewed from distal end of branch; chamber reconstructed is from the right side of branch, x 140; 6, reconstruction of typical chamber shape (three- dimensional) as viewed from obverse surface; chamber reconstructed is from the right side of branch, x140. MISSISSIPPIAN BRYOZOANS: SNYDER 107 obverse surface to slight angle toward fenestrule. Per- minal diaphragms present, primarily occurring toward istome present, complete; apertural stylets absent; ter- proximal end of zoarium. 108 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 Branches ranging from circular, ovate to elliptical in cross-section, medium to very thick in depth. Autozooecial chamber size intermediate, chambers biserially emplaced along a straight to sinuous axial wall; maximum chamber length extending proximo- distally, parallel to reverse wall. Chamber outline ovate, elliptical, irregularly pentagonal to triangular near re- verse wall; becoming irregularly pentagonal, rectan- gular to parallelogram-shaped in mid chamber and throughout most of chamber depth; ovate to elliptical near obverse surface. Vestibule present, varying in length from short to long. Superior and inferior hemi- septa both absent. Lateral-wall budding-angle ranging from 17° to 23° (means); reverse-wall budding-angle from 60° to 77° (means). Lamellar skeletal layer thick- ness intermediate to thick, exhibiting moderate to pro- nounced astogenetic thickening; granular skeletal layer thickness intermediate to thick, exhibiting no astoge- netic thickening. Three-dimensionally reconstructed chamber form an irregular rectangular to cubic box. Text-figure 15 illustrates zoarial outlines in longi- tudinal, tangential, and transverse orientations show- ing position of reticulate meshwork over zoarial sur- face, and three-dimensional chamber reconstructions from abaxial branch edge, obverse surface, and distal end of branch. Remarks.—The genus Hemitrypa was first recog- nized and described by Phillips (1841) from the De- vonian of England, and is readily recognized by the presence of a reticulate meshwork. This meshwork forms as extensions of granular skeletal material de- veloping atop the keel and dissepiments, forming a honeycomb-like cover over the obverse surface. Each hole in the mesh corresponds to an underlying auto- zooecial aperture. The reticulate meshwork in Hemitrypa is usually restricted to the more proximal portions of the zoar- ium, with the distalmost third of the zoarium normally not covered. Where the meshwork is absent, the ex- terior morphology of zoarial fragments is highly similar to and frequently confused with that of species of Aper- tostella, n. gen. Interiors are also similar in chamber shape and lack of superior and inferior hemisepta. Presence of reticulate meshwork is the best criterion for recognition of Hemitrypa, however, should this be absent, the genus can be separated from Apertostella by typical presence of more closely spaced nodes, changing fenestrule shape from obverse to reverse zoarial surface, and a more cubic chamber form. Sim- ilarities in chamber form are great enough between Apertostella and Hemitrypa to render presence of re- ticulate meshwork definitive. Previous workers, including Ulrich and Keyes, fre- quently depended on reverse exteriors for species rec- ognition. Reverse exteriors exhibit great change with astogeny, and their use led to species based on asto- genetic stage. Species composition.—Five Warsaw species have been assigned to this genus: H. perstriata Ulrich, 1890, H. hemitrypa (Prout, 1859), H. aprilae, n. sp., H. as- pera Ulrich, 1890, and H. vermifera (Ulrich, 1890). Range.—Silurian to Permian; Silurian and Lower Devonian species are distinct from those found in the Warsaw. Hemitrypa perstriata Ulrich, 1890 Plate 39, figures 6-12, Plate 40, figures 1-10, Plate 41, figures 1-5; Text-figure 15; Table 32 Hemitrypa perstriata Ulrich, 1890, p. 564, pl. 57, figs. 6, 6a [Keokuk Group, Bentonsport and Keokuk, Iowa]; Keyes, 1894, p. 25 [Keo- kuk Limestone, Keokuk, Iowa]. Hemitrypa pateriformis Ulrich, 1890, p. 564, pl. 57, figs. 7-7c [Keo- kuk Group, Keokuk, Iowa]; Keyes, 1894, p. 26 [Keokuk Lime- stone, Keokuk, Iowa]. Diagnosis.—Zoarium moderately robust, mesh spacing upper-end intermediate, pattern moderately regular; reticulate meshwork present, intermediately to poorly developed, polygonal (primarily hexagonal) in shape; branch robustness and width intermediate, thick in depth; straight to less commonly sinuous, lat- eral branches broadly curved at zoarial edge; trans- versely irregularly ovate, spacing lower-end interme- diate and joined at moderately regular intervals by lower-end intermediate width, intermediate-length dissepiments. Fenestrule size intermediate; shape el- liptical to ovate on obverse surface, rectangular to po- lygonal on reverse, highly variable. Autozooecial ap- erture size intermediate, elliptical to ovate, elongate proximodistally or proximoabaxially, rarely circular, surrounded by thin, well-developed, complete peri- stome; three to five (most commonly four) apertures per fenestrule. Single, lower-end intermediate width continuous keel present; keel straight to slightly anas- tomosing, extending along middle of obverse branch surface, atop which are positioned intermediate-size, irregularly stellate or ovate nodes. Autozooecial cham- ber size intermediate, chambers emplaced in two rows, except three rows, less frequently four rows proximal to sites of branch bifurcation; outline irregularly ovate to rounded pentagonal near reverse wall, rapidly be- coming slightly irregularly rectangular throughout most of chamber, irregularly ovate near obverse surface. Chamber longest dimension very slightly greater than depth, slightly elongate parallel to reverse wall in prox- imodistal direction. Aperture at distal-abaxial end of chamber, connected to chamber by intermediate-length, variable length vestibule. Superior and inferior hemi- septa both absent. Lateral-wall budding-angle highly variable (mean of 18°); reverse-wall budding-angle MISSISSIPPIAN BRYOZOANS: SNYDER 109 Table 32.—Summary numerical analysis of Hemitrypa perstriata Ulrich, 1890. For explanation of abbreviations of characters (left column), see Table 8b (foldout inside back cover). number of mea- coeffi- sure- standard cient of observed ments mean deviation variation range 1. WB 24 0.3145 0.0550 17.48 0.248-0.480 2. DBC 24 0.5120 0.0608 11.88 110/34620:612 3. WD 24 011600 -0:0322 2018++0:113=0:281 4. LF 24 0.5825 0.1576 27.06 0.369-0.803 5. WF 24 0.3563 0.0769 21.58 0.219-0.569 6. AF 24 4.15 0.32 [262 3-5 Us INE: 24 0.1320 0.0073 5.53 0.112-0.154 8. AW 24 0.0920 0.0065 7.07 | 0.058—0.108 9. ADB 24 0.2400 0.0167 6.96 | 0.222-0.302 10. AAB 24 0 2520500233 2102622. 0452-.0292 ll. ABB 24 0:3217 -0.0435 1352 0226-0434 12. DN 24 0:099020:01267 12.73 70072207160 14. SNB 24 0.4580 0.0965 20.96 0.316-0.800 15. WK 24 0:0592:75010123. 7720.78 7 20:02 8502114) 16. DSO 24 0.0120 0.0029 23.97 0.008-0.018 17. SSO 24 0.0386 0.0123 31.86 0.022-0.096 18. WP 24 0.0135 20.0027 - 20.00 0.006=01025 22. RSS 24 0.0220 0.0034 15.45 0.013-0.031 24. SSS 24 0.0456 0.0138 30.26 0.020-0.085 25. LRM 24 0.2380 0.0220 9.24 0.156-0.292 26. WRM 24 0.2240 0.0271 12.10 0.180-0.388 32. TRW 24 0.0128 0.0018 14.06 0.007-0.017 33. TLW 24 0.0094 0.0012 12.77 0.006-0.014 34. FWT 24 0.0741 0.0255 34.41 0.040-0.175 35. RWT 24 0.1884 0.0604 32.06 0.121-0.295 36. CL 24 0.2286 0.0162 7.09 0.195-0.245 37. CD 24 0.2250 0.0118 5.24 0.205-0.265 38. MAW 24 0.1325 0.0214. 165 . 10:092=0.168 39. MIW 24 oI 00170 153.22 00790.1141 40. VD 24 0.0720 0.0173 24.03 0.050-0.106 41. RA 24 70.70 5.61 7.94 58-82 ANA: 24 18.00 3.38 18.78 13-25 43. TB 24 0.4250 0.0887 20.88 0.325-0.571 highly constant (mean of 71°). Table 32 presents statistical criteria used in delim- iting this species. Exterior description.— Zoarium moderately robust, €xpansion flat to undulating, fan-shaped; mesh spacing Upper-end intermediate; pronounced astogenetic thickening of both obverse and reverse zoarial skele- ton; external zoarial pattern moderately regular. In- termediately to poorly developed reticulate meshwork Covering primarily proximal and medial obverse zoar- lal Surfaces, absent at lateral and distal edges of zoar- lum; reticulate meshwork thickened along branch mid- line, with mesh forming as secondary extension of keel, Nodes, and dissepiments; meshwork develops toward fenestrule from branch midline and dissepiment sur- face to form polygonal, primarily hexagonal feature Covering obverse zoarial surface, each facet of polygon (hexagon) developing around single apertural opening; Width and length of meshwork dimensions approxi- mately same as aperture spacings along and across ob- verse branch; width five-sevenths that of branch, meshwork opening width to length ratio approximately 1:1; variable number, four to seven, nodular extensions into meshwork opening from mesh skeletal edge. Prob- able mature zoarial widths and lengths of half a meter or more attained in large colonies. Branch robustness intermediate, width intermedi- ate, slightly variable; typically straight, less commonly exhibiting inflection toward sites of dissepiment em- placement, lateral branches broadly curved toward edge of zoarium. Branch spacing lower-end intermediate, distance between adjacent branch centers highly reg- ular. Obverse surface texture moderately granular, be- coming increasingly so with astogeny; surface rounded to moderately angular, except for presence of single keel; keel width lower-end intermediate, well-devel- oped, continuous, straight to slightly anastomosing, extending along branch midline and causing pro- nounced positive inflection in obverse surface profile. Pronounced astogenetic thickening of keel; most pro- nounced toward proximal end of zoarium. Nodes monoserially emplaced, well-developed, intermediate- size, irregularly stellate to ovate, elongate proximodis- tally; nodes regular in size, variable in shape; develop as projection from middle of keel; one to three (most commonly two) per fenestrule length; spacing inter- mediate, moderately even; pronounced increase of node diameter with astogeny. Intermediate-size stylets, vari- ably sized and positioned, occurring across obverse branch surface. Reverse surface texture granular, coarsening with astogeny, bearing relatively few rows of intermediately spaced longitudinal striae, which be- come covered by lamellar skeleton during astogeny; rows of intermediate-size microstylets, closely spaced, develop as extensions of longitudinal striae along re- verse branch surface, microstylet diameters increase with astogeny and microstylets become more variably positioned across reverse branch surface. Autozooecia in two rows across branch, except three rows, less fre- quently four rows for moderate to pronounced dis- tances proximal to sites of branch bifurcation; pro- nounced thickening proximal, moderate thinning distal to sites of branch bifurcation. Heterozooecia absent in all zoarial fragments examined. Dissepiments of lower-end intermediate width, slightly greater than half branch width, slightly vari- able; length intermediate, variable; connect branches at moderately regular intervals. Dissepiments exhibit pronounced medial thinning, pronounced flaring at branch-dissepiment junction; highly recessed from ob- verse, approximately even with reverse branch surface. Pronounced astogenetic thickening of dissepiments to- ward proximal end of zoarium. Obverse dissepiment surface with two to four longitudinal ridges emplaced 110 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 perpendicular to branch length, intermediate-size sty- lets, similar in size to obverse branch stylets, develop atop these ridges; stylets become irregularly positioned across dissepiments with astogeny; reverse dissepi- ment surface with single medially thickened ridge bear- ing intermediate-size microstylets. Obverse dissepi- ment surface texture moderately granular, reverse surface texture granular, both coarsening with asto- geny. Dissepiments emplaced perpendicular to branch length. Apertures commonly positioned on proximal or distal edge, or in middle of dissepiment edge at branch-dissepiment contact; arranged symmetrically or asymmetrically between branches. Fenestrule size intermediate; shape varying from el- liptical to ovate on obverse surface, becoming rect- angular to polygonal with highly angular appearance on reverse, elongate proximodistally; highly irregular in size and shape; greatly expanding in width and length in obverse-reverse direction. Width of fenestrule slightly less than that of branch on obverse surface, appreciably greater than branch width on reverse; fe- nestrule opening size reduced toward proximal end of zoarium due to astogenetic thickening of lamellar skel- eton. Width to length ratio of fenestrule variable, rang- ing from 1:2 to approximately 1:4; ratio of fenestrule mean width to length approximately 3:5; width more constant than length, both variable. Three to five (most commonly four) apertures per fenestrule length; dis- tance between closest aperture centers along branch and across branch approximately equal, spacing of ap- ertures across fenestrule approximately 1.3 times great- er; spacing along and across branch moderately con- stant, spacing across fenestrule variable. Autozooecial aperture size intermediate, large rela- tive to branch, shape elliptical to ovate, rarely circular; elongate proximodistally or proximoabaxially; width to length ratio approximately 7:10; size uniform, shape variable; opening typically oriented primarily parallel to plane of obverse surface, less frequently at slight angle toward fenestrule; surrounded by thin, well-de- veloped complete peristome. Aperture margins extend into fenestrule, causing slight to moderate inflections in fenestrule outline on obverse surface. Terminal di- aphragms, in places centrally thickened, occurring at proximal end of zoarium beneath reticulate meshwork. Zoarial supports common, well-developed, form primarily as extensions of reverse zoarial surface, less frequently from lateral edges of zoarium. Interior description.—Branches irregularly ovate in transverse section, enlarged on obverse surface, elon- gate in obverse-reverse direction, becoming increas- ingly elongate with addition of secondary lamellar skel- eton during astogeny. Branches thick, moderately variable in depth. Autozooecial living chamber size intermediate, chambers biserially arranged in alternating rows along planar branch axial wall; axial wall highly sinuous, exhibiting inflections toward and connecting with chamber lateral walls near reverse wall, axial wall be- coming straight in mid chamber and toward obverse surface. Chamber longest dimension very slightly greater than depth, elongate parallel to reverse walls in proximodistal direction. Autozooecial chamber out- line irregularly ovate to rounded pentagonal near re- verse wall; rapidly becoming slightly irregularly rect- angular throughout mid chamber and most of chamber depth; irregularly ovate near obverse surface, longest dimension of ovoid oriented distal-abaxially; chamber shape highly uniform. Aperture positioned at distal- abaxial end of chamber, connected to chamber by well- developed vestibule of intermediate length, length variable. Ratio of autozooecial chamber minimum width to maximum width approximately 4:7; maxi- mum width to depth ratio about 7:12; chamber depth and length essentially equal; chamber length and depth highly constant, maximum and minimum widths high- ly variable. Superior and inferior hemisepta both ab- sent. Autozooecial chambers diverge laterally from middle of branch at highly variable angle (mean of 18°); from reverse wall at highly constant angle (mean of 71°). Three-dimensionally reconstructed chamber form a slightly irregular square box; length as viewed from lateral edge of branch, and depth as viewed from distal end of branch approximately equal; width as viewed from obverse surface substantially shorter. Internal granular skeletal layer thickness interme- diate; granular skeletal layer well-developed, contin- uous with obverse nodes, stylets, keel, peristome, and reticulate meshwork, which is entirely formed of gran- ular skeletal material; reverse longitudinal striae and stylets; across dissepiments and in the middle of zoarial supports. Outer lamellar layer extremely thick, exhib- iting pronounced astogenetic thickening, most prom- inent toward proximal end of zoarium. Remarks.— Hemitrypa perstriata was based on ma- terials from the Keokuk Group in Bentonsport and Keokuk, Iowa, that emphasized the reverse zoarial sur- face and fenestrule dimensions, characters both highly dependent on zoarial astogeny: The “very narrow fe- nestrules and strongly striate branches" used by Ulrich (1890, p. 565) to differentiate H. perstriata from H pateriformis Ulrich, 1890 are characters which are ap- plicable toward the distal, but not proximal, end of the zoarium. As best I can determine from Ulrich’s illus- trations (the holotype of H. pateriformis was not found), H. pateriformis represents the most proximal end, and H. perstriata the most distal end, of zoarial fragments from the same species; therefore I am placing H. pa- teriformis in synonymy with H. perstriata. MISSISSIPPIAN BRYOZOANS: SNYDER 111 Within the hemitrypids, H. perstriata most closely resembles H. hemitrypa (Prout, 1859), with pro- nounced similarity in autozooecial chamber shape and size. Although H. hemitrypa exhibits a characteristi- cally greater chamber width than H. perstriata, the length and depth of the chambers in the two species are essentially the same. H. perstriata is further differ- entiated by thicker, deeper branches, coarser mesh with larger fenestrule openings, greater number of apertures per fenestrule length, and larger aperture openings. The approximately equal length and depth of the autozooecial chambers in these two species group them together, separating them from other hemitrypids which characteristically have lengths substantially greater than widths. Reticulate meshwork in these two species is also not typically as well-developed as in other hem- itrypids. Those similarities in chamber shape and size ob- served in H. perstriata and H. hemitrypa suggest close phylogenetic affinity. Material studied.— Fourty exterior fragments, 17 sectioned specimens; largest zoarial fragment 62 x 44 mm (width to length). The preservation of zoarial frag- ments is excellent as a result of the robust nature of Zoarium. The relatively delicate character of the retic- ulate meshwork results in its common compaction onto the obverse zoarial surface. Occurrence.— Hemitypa perstriata is most abundant In the northern half of the study area, although it is also found in lesser numbers in the southern portion. As its in situ occurrences are primarily in lower energy depositional environments, it is commonly found in argillaceous micrites and biomicrites. Syntypes.—ISGS (ISM) 2717 and USNM 43766 were apparently both figured by Ulrich (1890). Figured and/or measured specimens. —U1l X-6934, 6886, 6887, 6859-6862 (loc. 10, samples 28, 29), 6730, 6731 (loc. 47A, samples 32, 35), 6924-6927, 6847— 6850 (loc. 11, samples 52, 57). Hemitrypa hemitrypa (Prout, 1859) Plate 41, figures 6, 7, Plate 42, figures 1-12, Plate 43, figures 1-9; Table 33 Fenestella hemitrypa Prout, 1859, p. 444, pl. 17, figs. 4, 4a [Second Archimedes Limestone, Barrett’s Station, St. Louis County, Mis- Souri]. Hemitrypa proutana Ulrich, 1890, p. 560, pl. 57, figs. 1-1c [Keokuk Group, Warsaw, Illinois, Keokuk, Iowa. Warsaw Beds, Monroe County and Warsaw, Illinois, Barrett's Station, Missouri]; Trizna, 1958, p. 25, pl. 43, figs. 3-6, pl. 44, figs. 1-3. Hemitrypa hemitrypa Prout. Keyes, 1894, p. 25. Diagnosis.— Zoarium moderately robust, mesh Spacing intermediate, pattern regular; reticulate mesh- Work present, intermediately to poorly developed, po- lygonal in shape; branch robustness lower-end inter- Mediate, narrow in width, medium in depth; branches Table 33.—Summary numerical analysis of Hemitrypa hemitrypa (Prout, 1859). For explanation of abbreviations of characters (left column), see Table 8b (foldout inside back cover). number of mea- coeffi- sure- standard cient of observed ments mean deviation variation range 1. WB 24 0.2550 0.0460 18.08 0.145-0.356 2. DBC 24 0.4800 0.0580 12.08 0.352-0.572 3. WD 24 0.1663 0.0345 20.72 0.106-0.231 4. LF 24 0.4513 0.0821 18.20 0.252-0.575 5. WF 24 0.2625 0.0518 19.72 0.156-0.425 6. AF 24 2.50 0:51 20.43 2-3 T AL 24 0.1220 0.0083 6.80 0.096-0.146 8. AW 24 0.0880 0.0066 7.47 | 0.066—0.114 9. ADB 24 0.2215 0.0208 9.40 0.170-0.288 10. AAB 24 0.2320 0.0274 11.82 0.156-0.282 11. ABB 24 0.2925 0.0503 17.20 0.208-0.394 12. DN 24 0.1128 0.0099 8.82 0.072-0.170 14. SNB 24 0.4620 0.0558 12.08 0.360-0.612 15. WK 24 0.0920 0.0206 22.40 0.046-0.163 16. DSO 24 0.0114 0.0032 38.07 0.006-0.023 17. SSO 24 0.0286 0.0010 34.96 0.014-0.071 18. WP 24 0.0155 0.0343 22.18 0.007-0.032 21. RSL 24 0.1160 0.0279 24.05 0.074-0.146 22. RSS 24 0.0143 0.0023 16.15 0.008-0.020 23. SSL 24 0.5800 0.2197 37.88 0.240-0.784 24. SSS 24 0.0286 0.0076 26.40 0.013-0.052 25. LRM 24 0.2260 0.0188 8.33 0.160-0.310 26. WRM 24 0.2180 0.0228 10.47 0.160-0.322 30. OL 24 0.2400 0.0265 11.06 0.200-0.298 31. OW 24 02320 "0.0228 9.85 0.192-0.300 32. TRW 24 0.0105 0.0015 15.05 0.009-0.019 33. TLW 24 0.0092 0.0013 13.83 0.008-0.016 34. FWT 24 0.0828 0.0341 41.20 0.014-0.161 35. RWT 24 0.0675 0.0262 38.85 0.016-0.171 36. CL 24 0.2244 0.0135 6.02 0.205-0.264 37. CD 24 0.2185 0.0094 4.28 | 0.198-0.250 38. MAW 24 0.1625 0.0240 14.75 0.135-0.230 39. MIW 24 0.1250 0.0208 16.62 0.075-0.171 40. VD 24 0.0907 0.0262 28.85 0.043-0.176 41. RA 24 77.00 6.58 8.55 62-85 42. LA 24 18.00 3.20 17.24 12-26 43. TB 24 DESTA 0799: 21:95 7707257549 593 straight to slightly sinuous, broadly curved at lateral zoarial edge; branches transversely circular to rarely ovate, spacing lower-end intermediate, joined at reg- ular intervals by intermediate width and length dis- sepiments. Fenestrule size lower-end intermediate; shape elliptical to ovate on obverse surface, approach- ing rectangular to square on reverse, slightly regular. Autozooecial aperture size intermediate, elliptical to ovate, elongate proximodistally or proximoabaxially, rarely approaching circular; surrounded by thin, well- developed, complete peristome; two to three apertures per fenestrule. Single intermediate-width keel present; keel slightly anastomosing, extending along middle of obverse branch surface, atop which are upper-end in- termediate size, ovate to rarely irregularly stellate nodes. Autozooecial chamber size lower-end intermediate, 112 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 chambers emplaced in two rows, except either third row at sites of branch bifurcation or three rows for moderate to pronounced distances proximal to sites of branch bifurcation; outline irregularly ovate to round- ed pentagonal near reverse wall, irregularly pentagonal to approaching rectangular throughout most of cham- ber depth; irregularly ovate near obverse surface. Chamber longest dimension very slightly greater than depth, slightly elongate parallel to reverse wall in prox- imodistal direction. Aperture at proximodistal or dis- tal-abaxial end of chamber, connected to chamber by intermediate and variable length vestibule. Superior and inferior hemisepta both absent. Lateral-wall bud- ding-angle highly variable (mean of 18?); reverse-wall budding-angle constant (mean of 77?). Heterozooecia (ovicells?) occurring as intermediate size enlargements of some apertures. Table 33 presents statistical criteria used in delimiting this species. Exterior description. — Zoarium moderately robust, expansion flat, obversely or reversely curved or un- dulating, fan-shaped; mesh spacing intermediate; pro- nounced astogenetic thickening of both obverse and reverse zoarial skeleton; external zoarial pattern reg- ular. Intermediately to poorly developed reticulate meshwork covering primarily proximal and medial ob- verse zoarial surface, absent at lateral and distal edges of zoarium; reticulate meshwork slightly thickened along branch midline, with mesh forming as secondary extension of keel, nodes, and dissepiments; meshwork develops toward fenestrule from branch midline and dissepiment surface to form polygonal features cov- ering obverse zoarial surface, each facet of polygon developing around single apertural opening; width and length of meshwork dimensions approximately same as aperture spacing along and across obverse branch surface; width six-sevenths that of branch, meshwork opening width to length ratio approximately 1:1; vari- able number, three to seven, nodular extensions into meshwork opening from mesh skeletal edge. Probable mature zoarial widths 30 to 40 mm, lengths 35 to 50 mm. Branch robustness lower-end intermediate; branches narrow, slightly variable in width; straight to exhibiting slight inflections toward sites of dissepiment emplace- ment, lateralmost branches frequently broadly curved toward edge of zoarium. Branch spacing lower-end in- termediate, distance between adjacent branch centers highly regular. Obverse surface texture granular, coars- ening with astogeny; surface rounded, except for pres- ence of single keel; keel width intermediate, well-de- veloped, continuous, slightly anastomosing, positioned along branch midline and causing pronounced positive inflection in obverse surface profile. Pronounced as- togenetic thickening of keel; most pronounced toward proximal end of zoarium. Nodes monoserially em- placed, well-developed, size upper-end intermediate, irregularly ovate to more rarely irregularly stellate, elongate proximodistally; nodes highly regular in size, moderately variable in shape; develop as projections from middle of keel; one to two (most commonly one) per fenestrule length; spacing intermediate, even; pro- nounced increase of node diameter with astogeny. Lower-end intermediate stylets, variably sized and po- sitioned, occurring across obverse branch surface, Re- verse surface texture granular, coarsening with asto- geny, bearing relatively few rows of intermediately spaced longitudinal striae, which become covered by lamellar skeleton during astogeny; rows of small, close- ly spaced microstylets develop as extensions of lon- gitudinal striae along reverse branch surface; micro- stylet diameters increase with astogeny, microstylets become more variably positioned across reverse branch surface. Large macrostylets present along reverse branch midline; shape circular to ovate, elongate proximodis- tally, with size and shape barely regular; one to two macrostylets per fenestrule length, most common placement at branch-dissepiment junction; macrosty- let spacing highly irregular, with size of macrostylets greatly increasing during astogeny. Autozooecia in two rows across branch, except either third row at sites of branch bifurcation where middle autozooecium evi- dently shared by both branches, or three rows for mod- erate to pronounced distances proximal to sites of branch bifurcation; moderate thickening proximal, slight thinning distal to sites of branch bifurcation. Heterozooecia (ovicells?) occurring as intermdiate-size enlargements of some apertures; mean width and length of polymorphs approximately twice autozooecial ap- erture length; connection between polymorph and au- tozooecial chamber probable; polymorphs most com- monly situated toward proximal end of zoarium. Dissepiments of intermediate width, approximately two-thirds of branch width, variable; length interme- diate, constant; connect branches at regular intervals. Dissepiments exhibit moderate medial thinning, slight flaring at branch-dissepiment junction; slightly re- cessed from obverse, approximately even with reverse branch surface. Pronounced astogenetic thickening of dissepiments toward proximal end of zoarium. Ob- verse dissepiment surface with two to four longitudinal ridges emplaced perpendicular to branch length, small stylets similar in size to obverse branch stylets develop atop these ridges; stylets become irregularly positioned across dissepiments with astogeny; reverse dissepi- ment surface with medially thickened ridge bearing rows of intermediate-size microstylets. Obverse and reverse surface textures granular, coarsening with as- togeny. Dissepiments emplaced perpendicular to branch length. Apertures commonly positioned on proximal or distal edge, or in middle of dissepiment MISSISSIPPIAN BRYOZOANS: SNYDER H3 edge at branch-dissepiment contact, arranged sym- metrically or asymmetrically between branches. Fenestrule size lower-end intermediate; shape vary- ing from elliptical to ovate on obverse zoarial surface, approaching rectangular to square on reverse, elongate proximodistally; slightly regular in size, moderately regular in shape; greatly expanding in width and length in obverse-reverse direction. Width of fenestrule less than that of branch on obverse surface, appreciably greater than branch width on reverse; fenestrule open- ing size reduced toward proximal end of zoarium due to astogenetic thickening of lamellar skeleton. Width to length ratio of fenestrule variable, ranging from ap- proximately 1:1 to 1:3; ratio of fenestrule mean width to length approximately 7:12; both width and length barely constant. Two to three apertures per fenestrule length (mean of 2.5); distance between closest aperture centers along branch and across branch approximately €qual, spacing across fenestrule approximately 1.3 times greater; spacing along and across branch moderately Constant, spacing across fenestrule variable. Autozooecial aperture size intermediate, moderately large relative to branch, shape elliptical to ovate, rarely approaching circular; elongate proximodistally or Proximoabaxially; width to length ratio approximately 7:11; size uniform, shape variable; opening orientation ranging from parallel to plane of obverse surface to Slight angle toward fenestrule; surrounded by thin, well- developed, complete peristome. Aperture margins ex- tend into fenestrule, causing moderate inflections in fenestrule outline on obverse surface. Centrally thick- ened terminal diaphragms persent, occurring most commonly at proximal end of zoarium beneath over- lying reticulate meshwork. Zoarial supports develop as extensions of reverse Zoarial surface and lateral edges of zoarium. Interior description. — Branches most commonly cir- Cular, rarely ovate, in transverse section, slightly en- larged on obverse surface; elongate in obverse-reverse direction when ovate, becoming increasingly elongate With addition of secondary lamellar skeleton during astogeny. Branches medium, moderately variable in depth. Autozooecial living chamber size lower-end inter- Mediate, chambers biserially arranged in alternating rows along planar branch axial wall; axial wall zigzag- ging near reverse wall, extending diagonally across en- tire branch; axial wall becoming less sinuous in mid Chamber, inflected toward and connecting with cham- ber lateral walls, only slightly sinuous near obverse Surface. Chamber longest dimension very slightly greater than depth, elongate parallel to reverse wall in Proximodistal direction. Autozooecial chamber out- line irregularly ovate to rounded pentagonal near re- verse wall, rapidly becoming irregularly pentagonal to approaching rectangular throughout mid chamber and most of chamber depth; irregularly ovate near obverse surface, longest dimension of ovoid oriented proxi- modistally or slightly distal-abaxially; chamber shape moderately uniform. Aperture positioned at proxi- modistal or distal-abaxial end of chamber, connected to chamber by well-developed, intermediate-length vestibule; vestibule length highly variable. Ratio of autozooecial chamber minimum width to maximum width approximately 3:4; maximum width to depth ratio approximately 5:7; chamber depth and length essentially equal; chamber depth and length highly constant, minimum and maximum widths highly vari- able. Superior and inferior hemisepta both absent. Au- tozooecial chambers diverge laterally from middle of branch at highly variable angle (mean of 18°); from reverse wall at constant angle (mean of 77°). Three-dimensionally reconstructed chamber form a slightly irregular cubic box; length as viewed from lat- eral edge of branch, and depth as viewed from distal end of branch approximately equal; width as viewed from obverse surface moderately shorter. Internal granular skeletal layer thickness interme- diate; granular skeletal layer well-developed, contin- uous with obverse nodes, stylets, keel, peristome, and reticulate meshwork (completely composed of granular skeletal material); reverse longitudinal striae, micro- stylets and macrostylets; across dissepiments and in middle of zoarial supports. Outer lamellar layer thick- ness intermediate to thick, exhibiting pronounced as- togenetic thickening most prominent toward proximal end of zoarium. Remarks.—Fenestella hemitrypa was described by Prout (1859) from the Second Archimedes Limestone (Keokuk Limestone) at Barrett’s Station in St. Louis County, Missouri. The specimen reported by Prout lacked reticulate meshwork, and therefore he placed the species in Fenestella Lonsdale, 1839. Ulrich (1890) found zoaria having the same exterior appearance which contained reticulate meshwork locally across the ob- verse surface, and for this reason, Ulrich renamed the species Hemitrypa proutana for Prout, who originally described it. The original name H. hemitrypa is herein reapplied, as it has priority. Ulrich noted similarities between H. hemitrypa and H. plumosa (Fenestella plumosa Prout, 1860); the two species were distinguished by the latter’s coarser mesh spacing and restriction to the Keokuk Formation. H. hemitrypa closely resembles H. perstriata in au- tozooecial chamber shape and size, although the for- mer characteristically exhibits greater chamber width than the latter. H. hemitrypa also has narrower, thinner branches, finer mesh with smaller fenestrule openings, fewer apertures per fenestrule length, and smaller ap- erture openings. 114 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 I consider H. hemitrypa var. nodulosa Ulrich, 1890 to represent a different astogenetic stage of H. hemi- trypa, as well as a possible response to different de- positional environments. Material studied.— Fourty-eight exterior fragments, 12 sectioned specimens; largest zoarial fragment 22 x 32 mm (width to length). The zoarial fragments are well preserved, but the reticulate meshwork commonly is compacted onto obverse zoarial surfaces. Occurrence.—Hemitrypa hemitrypa is common throughout the Warsaw in the study area, primarily occurring in argillaceous micrites, biomicrites, and fa- cies thought to have had moderate- to low-energy de- positional environments. Syntypes.—ISGS(ISM) 2818-1/2; USNM 43371. Figured and/or measured specimens.—UI X-6844 (loc. 11, sample 55), 6845, 6928-6933 (loc. 10, samples 28, 33), 6846, 6853, 6858, 6943 (loc. 49B, samples 12, 14). Hemitrypa aprilae, new species Plates 44, figures 1-10, Plate 45, figures 1-8; Table 34 Etymology of name.—Named for the month of April, without doubt the finest time to do field work along the Mississippi. Diagnosis.—Zoarium moderately robust, mesh spacing close, pattern regular; reticulate meshwork present, extremely well-developed, polygonal (primar- ily hexagonal) in shape; branch robustness and width intermediate, deep in thickness; branches straight, broadly curved at lateral zoarial edge; transversely ap- proximately circular, becoming ovate to elliptical with astogeny, closely spaced and joined at moderately vari- able intervals by intermediate-width, short dissepi- ments. Fenestrules small; shape elliptical to ovate on obverse surface, approaching rectangular on reverse, moderately irregular. Autozooecial aperture size in- termediate, irregularly ovate, elongate proximo- abaxially, more rarely proximodistally to rarely cir- cular, surrounded by lower-end intermediate width, well-developed, complete peristome; two to three ap- ertures per fenestrule (mean of 2.5). Single interme- diate-width keel present; keel anastomosing, extending along middle of obverse branch surface, atop which develop upper-end intermediate size, irregularly stel- late to more rarely ovate nodes. Autozooecial chamber size lower-end intermediate, chambers emplaced in two rows, except either third row at sites of branch bifurcation or three rows for moderate to pronounced distances proximal to sites of branch bifurcation; out- line irregularly ovate to rounded triangular near re- verse wall; irregularly pentagonal throughout most of chamber depth, approaching rectangular nearer ob- verse surface; irregularly ovate to elliptical nearest ob- verse surface. Chamber longest dimension parallel to Table 34.—Summary numerical analysis of Hemitrypa aprilae, n. sp. For explanation of abbreviations of characters (left column), see Table 8b (foldout inside back cover). number of mea- coeffi- sure- standard cient of observed ments mean deviation variation range 1. WB 24 0.3627 0.0470 12.96 0.320-0.431 2. DBC 24 0.4465 0.0625 14.00 0.375-0.520 3. WD 24 02205 10:04890 22972 204156203235 4. LF 24 0.3958 0.0835 21.10 0.225-0.475 5. WF 24 0.1901 0.0351 18.46 0.125-0.320 6. AF 24 2:90) 0.92 20.89 2-3 7. AL 24 0.1238 0.0104 8.40 0.098-0.150 8. AW 24 0.0847 0.0108 12.00 0.062-0.106 9. ADB 24 0.2435 0.0230 9.45 0.210-0.280 10. AAB 24 0235540100233 9.89 0.208-0.272 11. ABB 24 0.2567 0:05 DI 19.91 | 0.160—0.352 12. DN 24 0.1138 0.0269 23.64 0.082-0.160 14. SNB 24 0.2598 0.0072 29.72 0.160-0.440 15. WK 24 0.0761 0.126 16.56 0.061-0.105 16. DSO 24 0.0156 0.0035 22.44 0.011-0.021 17. SSO 24 0.0497 0.0203 40.85 0.019-0.084 18. WP 24 0.0269 0.0068 25.28 0.016-0.043 22. RSS 24 0.0192 0.0037 19.27 0.013-0.030 24. SSS 24 0.0316 0.0093 29.43 0.020-0.055 25. LRM 24 0.2460 0.0238 9.67 0.151-0.320 26. WRM 24 0.2208 0.0297 13.45 0.141-0.309 30. OL L2 0.2242 0.0244 10.88 0.195-0.284 31. OW 12 0.1955 0.0241 12.33 0.167-0.264 32. TRW 24 0.0133 0.0029 21.80 0.008-0.022 33. TLW 24 0.0111 0.0018 16.22 0.009-0.015 34. FWT 24 0.1178 0.0339 28.78 0.065-0.186 35. RWT 24 0.1805 0.0759 42.05 0.096-0.375 36. CL 24 0.2240 0.0148 6.61 0.205-0.249 37, CD 24 0.1769 0.0091 5.14 0.161-0.195 38. MAW 24 0.1595 0.0247 15.49 0.125-0.200 39. MIW 24 0.1030 0.0205 19.90 0.068-0.133 40. VD 24 0.1361 0.0413 30.35 0.088-0.225 4]. RA 24 66.00 4.36 6.61 58-76 42. LA 24 20.00 4.21 21.54 1612-24 43. TB 24 0.4851 0.0843 17.38 0.388-0.612 reverse wall in proximodistal direction. Aperture at distal-abaxial end of chamber, connected to chamber by moderately long, variable-length vestibule. Superior and inferior hemisepta both absent. Lateral-wall bud- ding-angle highly variable (mean of 20°); reverse-wall budding-angle highly constant (mean of 66°). Hetero- zooecia (ovicells?) occurring as intermediate to pro- nounced enlargements of some apertures. Table 34 presents statistical criteria used in delim- iting this species. Exterior description.—Zoarium moderately robust, expansion most commonly flat, more rarely obversely or reversely curved, or undulating, fan-shaped; mesh spacing close; pronounced astogenetic thickening of both obverse and reverse zoarial skeleton; external zoarial pattern regular. Extremely well-developed re- ticulate meshwork covering obverse zoarial surface with | | | | MISSISSIPPIAN BRYOZOANS: SNYDER 115 astogeny, absent only at lateral and distal edges of zoar- ium; reticulate meshwork exhibiting pronounced thickening along branch midline, with mesh forming as secondary extension of keel, nodes, and dissepi- ments; meshwork develops toward fenestrule from branch midline and dissepiment surface to form po- lygonal (primarily hexagonal) features covering ob- verse zoarial surface, each facet of polygon (hexagon) developing around single apertural opening; width and length of meshwork dimensions approximately same as aperture spacings along and across obverse branch surface; width approximately three-fifths that of branch, mesh opening width to length ratio approximately 9: 10; variable number, three to six (most commonly four) nodular extensions into meshwork opening from mesh skeletal edge. Probable mature zoarial widths 20 to 60 mm, lengths 30 to 55 mm. Branch robustness intermediate, width intermedi- ate, moderately constant; straight, except lateral branches broadly curved toward edge of zoarium. Branches closely spaced, distance between adjacent branch centers regular. Obverse surface texture mod- erately granular, coarsening with astogeny, surface rounded to slightly angular, except for presence of sin- gle keel; keel width intermediate, extremely well-de- veloped, continuous, anastomosing, extending along branch midline and causing pronounced positive in- flection in obverse surface profile. Pronounced asto- genetic thickening of keel; most pronounced toward Proximal end of zoarium. Nodes monoserially em- Placed, well-developed, size upper-end intermediate, Shape typically irregularly stellate, more rarely ovate, elongate proximodistally; nodes moderately regular in Size, variable in shape; one to three (most commonly two) per fenestrule length; spacing lower-end inter- Mediate, uneven; pronounced increase of node di- ameter with astogeny. Intermediate-size stylets, vari- ably sized and highly variably positioned, occurring across obverse surface. Reverse surface texture gran- ular, coarsening with astogeny, bearing an intermediate Number of rows of closely spaced longitudinal striae, Which become completely covered by lamellar skeleton during astogeny; rows of intermediate size microsty- lets, closely spaced, develop as extensions of longitu- dinal striae along reverse branch surface, microstylets Slightly regular in size; microstylet diameters increase With astogeny, microstylets become more variably po- Sitioned across reverse branch surface. Autozooecia in two rows, except third row at sites of branch bifurca- tion where middle autozooecium evidently shared by both branches, or three rows for moderate to pro- Nounced distances proximal to sites of branch bifur- Cation; moderate thickening proximal, slight thinning distal to sites of branch bifurcation. Heterozooecia (ovicells?) occurring as intermediate to pronounced en- largements ofsome apertures; mean widths and lengths of polymorphs slightly less than twice autozooecial ap- erture length; connection evident between polymorph and autozooecial chamber; polymorphs most com- monly situated toward proximal end of zoarium. Dissepiments of intermediate width, approximately three-fifths branch width, moderately variable; short, moderately constant in length; connect branches at moderately variable intervals. Dissepiments barlike at distal end of zoarium, exhibiting only slight flaring at branch-dissepiment junction; exhibiting greater me- dial thinning and less barlike nature toward proximal end of zoarium; highly recessed from obverse, ap- proximately even with reverse branch surface. Pro- nounced astogenetic thickening of dissepiments to- ward proximal end of zoarium; highly recessed from obverse, approximately even with reverse branch sur- face. Obverse dissepiment surface with two to four longitudinal ridges emplaced perpendicular to branch length, intermediate stylets similar in size to obverse branch stylets develop atop these ridges; stylets become irregularly positioned across dissepiment surface and striae become covered by lamellar skeleton with as- togeny; reverse dissepiment surface with medially thickened ridge bearing intermediate-size microstylets. Obverse and reverse dissepiment surface texture gran- ular, coarsening with astogeny. Dissepiment emplace- ment typically perpendicular to branch length, more rarely at a slight angle from perpendicular. Apertures commonly positioned on proximal or distal edge, or in middle of dissepiment edge at branch-dissepiment contact, arranged symmetrically or asymmetrically be- tween branches. Fenestrules small; shape varying from elliptical to ovate on obverse surface, to approaching rectangular on reverse, elongate proximodistally; moderately ir- regular in size and shape; expanding in width and length in obverse-reverse direction. Width of fenestrule slightly less than half branch width on obverse surface, slightly greater than half branch width on reverse; fe- nestrule opening size greatly reduced toward proximal end of zoarium due to astogenetic thickening of la- mellar skeleton. Width to length ratio of fenestrule ranging from approximately 1:2 to nearly 1:4; ratio of fenestrule mean width to length approximately 1:2, length slightly more variable than width, both variable; two to three apertures per fenestrule length (mean of 2.5); distance between closest aperture centers along branch, across branch, and across fenestrule approxi- mately equal; spacing along and across branch mod- erately constant, spacing across fenestrule variable. Autozooecial aperture size intermediate, moderately large relative to branch, shape irregularly ovate to rare- ly circular, enlarged at distal end, typically elongate proximoabaxially, more rarely proximodistally; width 116 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 to length ratio approximately 2:3; size moderately uni- form, shape moderately variable; opening oriented typically parallel to plane of obverse surface, less com- monly at slight angle toward fenestrule; surrounded by lower-end intermediate width, well-developed com- plete peristome. Moderate projections of apertures into fenestrule, causing inflections in fenestrule outline on obverse surface. Centrally thickened terminal dia- phragm present, occurring most commonly at proxi- mal end of zoarium beneath overlying reticulate mesh- work. Zoarial supports common, develop as extensions of reverse zoarial surfaces. Interior description.—Branches approximately cir- cular in transverse section; becoming irregularly ovate to elliptical, elongate in obverse-reverse direction with addition of secondary lamellar skeleton during asto- geny. Branches thick, moderately variable in depth. Autozooecial living chamber size lower-end inter- mediate, chambers biserially arranged in alternating rows along planar branch axial wall; axial wall zigzag- ging near reverse wall, extending diagonally across en- tire branch; axial wall becoming less sinuous in mid chamber, inflected toward and connecting with cham- ber lateral walls, only slightly sinuous near obverse surface. Chamber longest dimension parallel to reverse wall in proximodistal direction. Autozooecial chamber outline irregularly ovate to rounded triangular near reverse wall, rapidly becoming irregularly pentagonal throughout mid chamber and most of chamber depth, approaching rectangular nearer obverse surface; be- coming irregularly ovate to elliptical nearest obverse surface, longest dimension oriented distal-abaxially; chamber shape moderately uniform. Aperture located at distal-abaxial end of chamber, connected to cham- ber by well-developed, moderately long, variable-length vestibule. Ratio of autozooecial chamber minimum width to maximum width approximately 2:3; maxi- mum width to depth ratio approximately 9:10; ratio of chamber depth to length about 4:5; chamber depth and length highly constant, minimum and maximum widths highly variable. Superior and inferior hemisep- ta both absent. Autozooecial chambers diverge later- ally from middle of branch at highly variable angle (mean of 20°); from reverse wall at highly constant angle (mean of 66°). Three-dimensionally reconstructed chamber form an irregular rectangular box; length as viewed from lateral edge of branch; depth, viewed from distal end of branch, slightly greater than width, viewed from obverse surface. Internal granular skeletal layer moderately thick, well- developed, continuous with obverse nodes, stylets, keel, peristome, and reticulate meshwork, which is com- pletely composed of granular skeletal material; reverse longitudinal striae and microstylets; across dissepi- ments and in the middle of zoarial supports. Outer lamellar layer extremely thick, exhibiting pronounced astogenetic thickening, most prominent toward prox- imal end of zoarium. Remarks.—Pronounced astogenetic thickening, which gives a highly varied appearance to the exterior reverse and to a lesser degree the obverse surface, char- acterizes H. aprilae. This species most closely resem- bles H. aspera Ulrich, 1890 among the species of Hemitrypa, but the two species are differentiated by the appreciably wider and deeper branches, slightly shorter and wider autozooecial chambers, moderately larger and narrower fenestrule openings, and lack of reverse macrostylets in H. aprilae. Similarities between H. aprilae and H. aspera do, however, suggest close phylogenetic affinities. Material studied.—Twenty-two exterior fragments, eight sectioned specimens; largest zoarial fragment 24x32 mm (width to length). The excellent preser- vation, including that of the reticulate meshwork, ob- served in this species probably is a result of pronounced astogenetic thickening of lamellar skeleton. Occurrence.— Hemitrypa aprilae is rare at the Val- meyer and St. Louis localities, and occurs primarily in the Lower and Middle Warsaw at these localities. It is present in both calcarenites and shales. Holotype.— UI X-6867 (loc. 49B, sample 15). Paratypes.— UI X-6865, 6866, 6935-6939 (loc. 49B, samples 12, 13). Hemitrypa aspera Ulrich, 1890 Plate 46, figures 1-13, Plate 47, figures 1-6; Table 35 Hemitrypa aspera Ulrich, 1890, p. 563, pl. 57, figs. 3a, 4-4f [Keokuk Group, Nauvoo, Illinois, Keokuk and Bentonsport, Iowa]; Keyes, 1894, p. 25 [Keokuk Limestone, Keokuk, Iowa]. Diagnosis.—Zoarium moderately delicate, mesh spacing lower-end intermediate, pattern moderately regular; reticulate meshwork present, well-developed, polygonal in shape; branches delicate, width narrow, intermediate in depth, branches straight to broadly sin- uous, lateral branches broadly curved at zoarial edge; transversely approximately circular, becoming ellip- tical to ovate with astogeny, closely spaced and joined at moderately regular intervals by lower-end inter- mediate width, short dissepiments. Fenestrules small; shape elliptical to ovate on obverse surface, approach- ing rectangular to square on reverse, irregular. Auto- zooecial aperture size intermediate, ovate, elongate proximodistally or proximoabaxially, to rarely circu- lar; surrounded by thin, well-developed, complete per- istome; one to three (most commonly two) apertures per fenestrule. Single intermediate width keel present; keel straight to anastomosing, extending along middle of obverse branch surface, atop which are intermediate MISSISSIPPIAN BRYOZOANS: SNYDER 147 Table 35.—Summary numerical analysis of Hemitrypa aspera Ul- rich, 1890. For explanation of abbreviations of characters (left col- umn), see Table 8b (foldout inside back cover). number of mea- coeffi- sure- standard cient of observed ments mean deviation variation range 1. WB 24 0.2750 0.0447 16.25 0.156-0.388 2. DBC 24 0.4250 0.0734 17.27 0.273-0.584 3. WD 24 0.1385 0.0294 21.23 0.108-0.294 4. LF 24 0.3540 0.1128 31.86 0.200-0.488 5. WE 24 0.2400 0.0531 22.13 0.138-0.356 6. AF 24 2.25 0.45 20.10 1-3 7. AL 24 0.1300 0.0087 6.69 0.104—0.156 8. AW 24 0.0880 0.0065 7.39 0.072-0.126 9. ADB 24 0.2400 0.0173 7.21 0.204-0.270 10. AAB 24 0.2580 0.0279 10.81 0.186-0.276 11. ABB 24 0.2670 0.0388 14.53 0.214-0.385 12. DN 24 0.1060 0.0119 11.23 0.072-0.200 14. SNB 24 0.2880 0.0467 16.23 0.194-0.388 15. WK 24 0.0888 0.0159 17.91 | 0.038-0.139 16. DSO 24 0.0165 0.0043 36.06 0.008-0.028 17. SSO 24 0.0465 0.0181 38.92 0.024-0.120 18. WP 24 0.0212 0.0035 16.51 0.020-0.038 21. RSL 24 0.0740 0.0187 25.27 0.046-0.126 22. RSS 24 0.0320 0.0043 13.44 0.018-0.058 23. SSL 24 0.1120 0.0360 32.14 0.068-0.248 24. SSS 24 0.0425 0.0089 20.94 0.034-0.088 25. LRM 24 0.2450 0.0227 9.27 0.132-0.320 26. WRM 24 0.2240 0.0296 13.21 0.120-0.336 30. OL 24 0.2420 0.0514 21.24 0.160-0.360 31. OW 24 0.2400 0.0450 18.75 0.174-0.392 32. TRW 24 0.0114 0.0020 17.54 0.009-0.026 33. TLW 24 0.0104 0.0014 13.46 0.008-0.019 34. FWT 24 0.0428 0.0172 40.19 0.013-0.126 35. RWT 24 0.0721 0.0231 32.04 0.021-0.135 36. CL 24 0.2385 0.0115 4.84 0.225-0.295 37. CD 24 0.1620 0.0111 6.85 0.146-0.220 38. MAW 24 0.1325 0.0228 17.21 0.102—0.200 39. MIW 24 0.0750 0.0142 18.93 0.033-0.128 40. VD 24 0.0450 0.0101 22.44 0.020-0.091 41. RA 24 68.50 Sn 8.42 60-84 42. LA 24 16.65 3.35 20.12 12-31 13. TB 24 0.4550 0.0684 19.27 0.368-0.627 Size, circular, ovate to iregularly stellate nodes. Au- lozooecial chamber size lower-end intermediate, Chambers emplaced in two rows, except either third Tow at sites of branch bifurcation or three rows for Moderate to pronounced distances proximal to sites of branch bifurcation; outline irregularly ovate to round- *d triangular near reverse wall; irregularly pentagonal throughout most of chamber depth; irregularly ovate to elliptical near obverse surface. Chamber longest di- Tension parallel to reverse wall in proximodistal di- rection. Aperture at distal-abaxial end of chamber, Connected to chamber by short, variable-length ves- übule, Superior and inferior hemisepta both absent. Lateral-wall budding-angle highly variable (mean of approximately 17°); reverse-wall budding-angle con- Stant (mean of 69°). Heterozooecia (ovicells?) occurring as intermediate size enlargements of some apertures. Table 35 presents statistical criteria used in delim- iting this species. Exterior description.— Zoarium moderately delicate, expansion flat to undulating, fan-shaped; mesh spacing lower-end intermediate; moderate to pronounced as- togenetic thickening of both obverse and reverse zoar- ial skeleton; external zoarial pattern moderately irreg- ular. Well-developed reticulate meshwork present throughout obverse surface of zoarium best developed typically covering proximal and medial zoarium sur- face, less common at lateral and distal edges of zoar- ium; reticulate meshwork slightly thickened along branch midline, with mesh forming as secondary ex- tensions of keel, nodes, and dissepiments; meshwork develops toward fenestrule from branch midline and dissepiment surface to form irregularly polygonal (ranging from square to hexagonal in shape) features covering obverse zoarial surface, each facet of polygon developing around single apertural opening; width and length of meshwork dimensions approximately same as aperture spacings along and across obverse branch surface; width approximately same as aperture spac- ings along and across obverse branch surface; width approximately four-fifths that of branch, meshwork opening width to length ratio approximately 11:12; three to seven (most commonly four) nodular exten- sions into meshwork opening from mesh skeletal edge. Probable mature zoarial widths 25 to 40 mm, lengths 30 to 50 mm. Branches delicate, narrow, moderately variable in width; straight to broadly sinuous, lateral branches broadly curved toward edge of zoarium. Branches closely spaced, distance between adjacent branch cen- ters moderately regular. Obverse surface texture mod- erately granular, becoming increasingly so with asto- geny, surface rounded to slightly angular, except for presence of single keel; keel width intermediate, ex- tremely well-developed, continuous, straight to anas- tomosing, extending along branch midline and causing pronounced positive inflection in obverse surface pro- file. Pronounced astogenetic thickening of keel; most pronounced toward proximal end of zoarium. Nodes monoserially emplaced, well-developed, intermediate- size, shape circular, ovate to irregularly stellate, elon- gate proximodistally; nodes highly regular in size, vari- able in shape; develop as projections from middle of keel; one to three (most commonly two) per fenestrule length; spacing intermediate, moderately even; pro- nounced increase of node diameter with astogeny. In- termediate-size stylets, highly variably sized and po- sitioned, occurring across obverse surface. Reverse surface texture granular, becoming increasingly so with astogeny, bearing few rows of widely spaced longtu- dinal striae which become partially to completely cov- 118 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 ered by lamellar skeleton during astogeny; rows of large microstylets, closely spaced, develop as extensions of longitudinal striae along reverse branch surface; during astogeny bimodal development of reverse microstylets occurs, with some microstylets remaining relatively unchanged, others joining to form aggregates that be- come intermediate-size macrostylets; shape circular to ovate, slightly elongate proximodistally, with size and shape both variable; irregularly positioned across branch surface; spacing close to intermediate, variable, with size of macrostylet greatly increasing during as- togeny. Autozooecia in two rows, except either third row at sites of branch bifurcation where middle au- tozooecium evidently shared by both branches, or three rows for moderate to pronounced distances proximal to sites of branch bifurcation; slight thickening prox- imal, thinning distal to sites of branch bifurcation. Het- erozooecia (ovicells?) occurring as intermediate to pro- nounced enlargements of some apertures; mean widths and lengths of polymorphs approximately twice au- tozooecial aperture length; polymorph widths and lengths approximately equal; connection evident be- tween polymorph and autozooecial chamber; poly- morphs most commonly situated toward proximal end of zoarium. Dissepiments of lower-end intermediate width, slightly greater than half branch width, variable; short, variable in length; connect branches at moderately reg- ular intervals. Dissepiments barlike, exhibiting slight medial thinning, slight flaring at branch-dissepiment junction; highly recessed from obverse, approximately even with reverse branch surface. Moderate astoge- netic thickening of dissepiments toward proximal end of zoarium. Obverse dissepiment surface with two to four longitudinal ridges emplaced perpendicular to branch length, intermediate stylets similar in size to obverse branch stylets develop atop these ridges; stylets become irregularly positioned across dissepiment sur- face and striae become covered by lamellar skeleton with astogeny; reverse dissepiment surface with me- dially thickened ridge bearing large microstylets and intermediate-size macrostylets. Obverse and reverse dissepiment surface texture granular, coarsening with astogeny. Dissepiment emplacement variable, ranging from perpendicular to branch length to angles up to 20° from perpendicular. Apertures commonly posi- tioned on proximal or distal edge, or in middle of dissepiment edge at branch-dissepiment contact, ar- ranged symmetrically or asymmetrically between branches. Fenestrules small; shape varying from elliptical to ovate on obverse surface, approaching rectangular to square on reverse, elongate proximodistally; irregular in size and shape; moderately expanding in width and length in obverse-reverse direction. Width of fenes- trule slightly less than branch width on obverse surface, slightly greater than branch width on reverse; fenes- trule opening size greatly reduced toward proximal end of zoarium due to astogenetic thickening of lamellar skeleton. Width to length ratio of fenestrule ranging from approximately 4:5 to 1:5; ratio of fenestrule mean width to length approximately 2:3, both width and length variable, with length more so than width. One to three (most commonly two) apertures per fenestrule length; distance between closest aperture centers along branch, across branch and across fenestrule approxi- mately equal; spacing along and across branch mod- erately constant to slightly variable, spacing across fe- nestrule variable. Autozooecial aperture size intermediate, moderately large relative to branch, shape ovate to rarely circular; elongate proximodistally or proximoabaxially; width to length ratio approximately 2:3; size uniform, shape moderately variable; opening orientation typically at slight angle toward fenestrule, less commonly parallel to plane of obverse surface; surrounded by thin, well- developed, complete peristome. Moderate projection of apertures into fenestrule, causing inflections in fe- nestrule outline on obverse surface. Centrally thick- ened terminal diaphragms present, occurring most commonly at proximal end of zoarium beneath over- lying reticulate meshwork. Zoarial supports moderately rare, develop as exten- sions of reverse zoarial surface and lateral edges of zoarium. Interior description.—Branches approximately cir- cular in transverse section; becoming irregularly ovate to elliptical, elongate either obverse-reversely or par- allel to plane of obverse surface, with addition of sec- ondary lamellar skeleton during astogeny. Branch depth medium, moderately variable. Autozooecial living chamber size lower-end inter- mediate, chambers biserially arranged in alternating rows along planar branch axial wall; axial wall zigzag- ging near reverse wall, extending diagonally across en- tire branch; axial wall becoming less sinuous in mid chamber, inflected toward and connecting with cham- ber lateral walls, only slightly sinuous near obverse surface. Chamber longest dimension parallel to reverse wallin proximodistal direction. Autozooecial chamber outline irregularly ovate to rounded triangular near reverse wall, rapidly becoming irregularly pentagonal throughout mid chamber and most of chamber depth; irregularly ovate to elliptical near obverse surface, longest dimension oriented distal-abaxially; chamber shape moderately to highly uniform. Aperture located at distal-abaxial end of chamber, connected to cham- ber by well-developed, short, variable-length vestibule. Ratio of autozooecial chamber minimum width to maximum width approximately 5:9; maximum width to depth ratio approximately 4:5; ratio of chamber MISSISSIPPIAN BRYOZOANS: SNYDER 119 depth to length approximately 2:3; chamber depth and length highly constant, minimum and maximum widths highly variable. Superior and inferior hemisepta both absent. Autozooecial chambers diverge laterally from middle of branch at highly variable angle (mean of approximately 17°); from reverse wall at constant angle (mean of 69°). Three-dimensionally reconstructed chamber form an irregular rectangular box; length as viewed from lateral edge of branch; depth, viewed from distal end of branch, moderately greater than width, viewed from Obverse surface. Internal granular skeletal layer relatively thick, well- developed, continuous with obverse nodes, stylets, keel, Peristome, and reticulate meshwork, which is com- pletely composed of granular skeletal material; reverse longitudinal striae, microstylets and macrostylets; across dissepiments and in middle of zoarial supports. Outer lamellar layer thickness intermediate to thick, exhibiting moderate to pronounced astogenetic thick- ening, most prominent toward proximal end of zoar- lum. Remarks.— Hemitrypa aspera was first identified by Ulrich from “Keokuk Group” materials collected near Nauvoo, Illinois and Keokuk and Bentonsport, Iowa. Ulrich included what is currently considered the Lower Warsaw in his “Keokuk Group”. H. aspera was rec- Ognized by Ulrich on the basis of nodes on the reverse dissepiment surface and strong spines extending from the reticulate meshwork. The presence of both reverse Microstylets and macrostylets characterizes this spe- Cies, although spinal development associated with the Obverse reticulate meshwork is typical of certain as- togenetic stages in all species of Hemitrypa Phillips, 1841. H. aspera is distinguished from other species of Hemitrypa by having the smallest autozooecial cham- ber size of all such species analyzed, the closest spaced branches, finest mesh spacing, and presence of mac- Tostylets on reverse branch and dissepiment surfaces. - aspera is the only Warsaw species which contains these macrostylets, thus allowing species recognition from the reverse surface. It is, however, desirable to have interior analyses as well. Material studied.— Thirty-four exterior fragments, 10 sectioned specimens; largest zoarial fragment 27 x 20 mm (width to length). The preservation of zoarial frag- Ments, including reticulate meshwork, is excellent in this species. Occurrence.—Hemitrypa aspera is common throughout the study area, most commonly occurring In facies deposited in moderately to extremely low en- ergy depositional environments. " Syntypes.—ISGS (ISM) 2823-1/2; USNM 43764, 3765. Figured and/or measured specimens. —UI X-6855, 6940 (loc. 10, sample 28), 6852 (loc. 11, sample 57), 6851, 6854, 6856, 6857 (loc. 49B, samples 12, 14, 17). Hemitrypa vermifera (Ulrich, 1890) Plate 47, figure 7, Plate 48, figures 1-10, Plate 49, figures 1—6; Table 36 Hemitrypa proutana var. vermifera Ulrich, 1890, p. 562, pl. 57, figs. 5, 5a [Warsaw Beds, Warsaw, Illinois]. Diagnosis.—Zoarium robust, mesh spacing close, pattern regular; reticulate meshwork present, well-de- veloped, polygonal (square to hexagonal) in shape; branches robust, width intermediate, very thick in depth; branches straight to less commonly sinuous, broadly curved at lateral zoarial edge; transversely cir- cular to irregularly elliptical, spacing close and joined at moderately regular intervals by intermediate-width, short dissepiments. Fenestrule size lower-end inter- mediate; shape typically elliptical, less commonly ovate, rarely circular, moderately irregular. Autozooecial ap- ertures large, irregularly ovate to elliptical, rarely cir- cular, typically elongate proximoabaxially or proxi- modistally; surrounded by upper-end thin, well- developed, complete peristome; two to three apertures per fenestrule (mean of 2.5). Single, intermediate-width, continuous keel present; keel straight to slightly anas- tomosing, extending along middle of obverse branch surface, atop which are positioned upper-end inter- mediate size, irregularly stellate to ovate nodes. Au- tozooecial chamber size intermediate, chambers em- placed in two rows, except either third row at sites of branch bifurcation or more rarely three rows for mod- erate distances proximal to sites of branch bifurcation; outline irregularly ovate, elliptical to rounded trian- gular near reverse wall, irregularly pentagonal imme- diately toward mid chamber, outline irregular paral- lelogram to rectangle throughout most of chamber, irregularly ovate near obverse surface. Chamber long- est dimension parallel to reverse wall proximodistally. Aperture at distal-abaxial end of chamber, connected to chamber by intermediate, highly variable length ves- tibule. Superior and inferior hemisepta both absent. Lateral-wall budding-angle highly variable (mean of 23°); reverse-wall budding-angle highly constant (mean of 60°). Heterozooecia (ovicells?) occurring as pro- nounced enlargements of some apertures. Table 36 presents statistical criteria used in delim- iting this species. Exterior description.—Zoarium robust, expansion flat to rarely slightly undulating, fan-shaped; mesh spacing close; extremely pronounced astogenetic thick- ening of both obverse and reverse zoarial skeleton; external zoarial pattern regular. Well-developed retic- ulate meshwork covering obverse zoarial surface, ab- sent only at lateral and distal edges of zoarium; retic- 120 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 ulate meshwork exhibiting pronounced thickening along branch midline, with mesh forming as secondary extension of keel, nodes, and dissepiments; mesh de- velops toward fenestrule from branch midline and dis- sepiment surface to form polygonal (ranging from square to hexagonal) feature covering obverse zoarial surface, each facet of polygon developing around single apertural opening; width and length of meshwork di- mensions slightly greater than aperture spacings along and across obverse branch; width approximately sev- en-eighths that of branch, meshwork width to length ratio approximately 1:1, width slightly greater than length; variable number, three to seven, nodular ex- tensions into meshwork opening from mesh skeletal edge. Probable mature zoarial widths and lengths of half a meter or more attained in large zoaria. Branches robust, width intermediate, slightly vari- able; typically straight, less commonly sinuous, exhib- iting minor inflections toward sites of dissepiment em- placement, lateral branches broadly curved toward edge of zoarium. Branch spacing close, distance between adjacent branch centers highly regular. Obverse surface texture slightly granular, becoming moderately gran- ular with astogeny; surface angular to slightly rounded, containing single keel; keel width intermediate, well- developed, continuous, straight or slightly anastomos- ing, extending along branch midline and causing pro- nounced positive inflection in obverse surface profile. Pronounced astogenetic thickening of keel; most pro- nounced toward proximal end and middle of zoarium. Node monoserially emplaced, well-developed, size up- per-end intermediate, shape irregularly stellate to ovate, elongate proximodistally; nodes highly regular in size, variable in shape; develop as projections from middle of keel; one to three (most commonly two) per fenes- trule length; nodes intermediately highly regularly spaced; pronounced increase of node diameter with astogeny. Intermediate-size stylets, variably sized and positioned, occurring across obverse branch surface. Reverse surface texture granular, coarsening with as- togeny, bearing relatively few rows of intermediately spaced longitudinal striae, which become covered by lamellar skeleton. during astogeny; rows of numerous intermediate-size microstylets, closely spaced, develop as extensions of longitudinal striae along reverse branch surface; microstylets moderately constant, diameters exhibiting slight increase with astogeny and micro- stylets become more variably positioned across reverse branch surface. Autozooecia in two rows across branch, except either third row at sites of branch bifurcation, or more rarely three rows extending for moderate dis- tances proximal to sites of branch bifurcation; pro- nounced thickening proximal, moderate thinning dis- tal to sites of branch bifurcation. Heterozooecia (ovicells?) occurring as pronounced enlargements of Table 36.—Summary numerical analysis of Hemitrypa vermifera (Ulrich, 1890). For explanation of abbreviations of characters (left column), see Table 8b (foldout inside back cover). number of mea- coeffi- sure- standard cient of observed ments mean deviation variation range 1. WB 24 0.3416 0.0580 16.98 0.225-0.500 2. DBC 24 0.5209 0.0679 13.04 0.400-0.640 3. WD 24 0.2334 0.0465 19.92 0.165-0.338 4. LF 24 0.4452 0.0945 21.23 0.231-0.588 5. WF 24 0.2457 0.0432 17.58 0.153-0.331 6. AF 24 2.50 0.51 20.43 2-3 7. AL 24 0.1655 0.0102 6.16 0.146-0.184 8. AW 24 0.1140 0.0081 7.11 0.100-0.130 9. ADB 24 0.2828 0.0210 7.43 0.240-0.320 10. AAB 24 0.2799 0.0347 12.40 0.206-0.348 11. ABB 24 0.3076 0.0399 12.97 0.250-0.400 12. DN 24 0.1181 0.0121 10.25 0.096-0.148 14. SNB 24 0.3057 0.0250 8.18 0.264-0.356 15. WK 24 0.0907 0.0165 18.19 0.066-0.136 16. DSO 24 0.0129 0.0028 21.71 0.008-0.021 17. SSO 24 0.0401 0.0117 29.18 0.024-0.078 18. WP 24 0.0198 0.0039 19.70 0.015-0.029 22. RSS 24 0.0198 0.0027 15.17 0.016-0.025 24. SSS 24 0.0343 0.0093 27.11 0.022-0.058 25. LRM 24 0.2817 0.0210 7.45 | 0.232-0.316 26. WRM 24 0.3093 0.0331 10.70 0.260-0.400 30. OL 24 0.2615 0.0367 14.03 0.206-0.344 31. OW 24 0.2113 0.0234 11.07 0.180-0.248 32. TRW 24 0.0243 0.0033 13.58 0.019-0.029 33. TLW 24 0.0163 0.0029 17.79 0.011-0.022 34. FWT 24 0.0898 0.0297 33.07 0.046-0.140 35. RWT 24 0.2186 0.0628 28.73 0.133-0.319 36. CL 24 0.2918 0.0133 4.56 0.278-0.318 37. CD 24 0.2146 0.0164 7.64 0.188-0.249 38. MAW 24 0.1667 0.0277 16.62 10:12020:2 10 40. VD 24 0.0823 0.0198 24.06 0.050-0.121 41. RA 24 59175 4.16 6.96 52-67 42. LA 24 23.00 4.47 19.44 14-30 43. TB 24 0.6672 0.1239 18.57 0.471-0.910 some apertures; mean widths and lengths of poly- morphs approximately twice autozooecial aperture length; polymorph width slightly less than length, ratio 4:5; connection evident between polymorph and au- tozooecial chamber; polymorphs most commonly sit- uated toward proximal end of zoarium. Dissepiments of intermediate width, approximately two-thirds that of branch, barely constant; short, mod- erately constant in length; connect branches at mod- erately regular intervals. Dissepiments exhibit mod- erate medial thinning, pronounced flaring at branch- dissepiment junction; highly recessed from obverse, approximately even with reverse branch surface. Pro- nounced astogenetic thickening of dissepiments to- ward proximal end of zoarium. Obverse dissepiment surface with one to three longitudinal ridges emplaced perpendicular to branch length, intermediate-size sty- lets, similar in size to obverse branch stylets, develop MISSISSIPPIAN BRYOZOANS: SNYDER 121 atop these ridges; stylets become irregularly positioned across dissepiment with astogeny; reverse dissepiment surface bearing rows of intermediate-size microstylets. Obverse dissepiment surface texture slightly granular, reverse surface texture granular, both coarsening with astogeny. Dissepiments emplaced approximately per- pendicular to branch length. Apertures commonly po- sitioned on proximal or distal edge, or in middle of dissepiment edge at branch-dissepiment contact; ar- ranged symmetrically or asymmetrically between branches. Fenestrule size lower-end intermediate; shape typi- cally elliptical; less commonly ovate, elongate proxi- modistally, rarely circular; moderately irregular in size and shape; slightly expanding in width and length in Obverse-reverse direction. Width of fenestrule ap- proximately half that of branch on obverse surface, four-fifths branch width on reverse; fenestrule opening size reduced toward proximal end of zoarium due to astogenetic thickening of lamellar skeleton. Width to length ratio of fenestrule variable, ranging from 1:1 to as much as 1:4; ratio of fenestrule mean width to length approximately 5:9; width more constant than length, width barely constant and length slightly variable. Two to three apertures per fenestrule length (mean of 2.5); distance between closest aperture centers along branch and across branch equal, slightly less than spacing across fenestrule which is approximately 1.1 times greater; Spacing along branch moderately constant, spacing across branch and across fenestrule both moderately variable. Autozooecial apertures large, shape irregularly ovate to elliptical, rarely circular, enlarged slightly at distal end; elongate proximoabaxially or proximodistally; width to length ratio approximately 2:3; size highly uniform, shape moderately variable; opening typically Oriented parallel to plane of obverse surface, less fre- quently at slight angle toward fenestrule; surrounded by upper-end thin, well-developed complete peri- Stome. Aperture margins extend into fenestrule, caus- Ing slight inflections in fenestrule outline on obverse Surface. Centrally thickened terminal diaphragms oc- Curring at proximal end of zoarium beneath reticulate meshwork. Zoarial supports well-developed, forming as exten- sions of reverse zoarial surface or lateral edges of zoar- lum, Interior description.— Branches circular to irregular- ly elliptical in transverse section, slightly enlarged on obverse surface, elongate in obverse-reverse direction, coming increasingly elongate with addition of sec- Ondary lamellar skeleton during astogeny. Branches very thick, moderately variable in depth. Autozooecial living chamber size intermediate, Chambers biserially arranged along planar branch axial wall; axial wall zigzagging near reverse wall, extending diagonally across entire branch; becoming less sinuous toward mid chamber, extending toward and connect- ing with chamber lateral walls; axial wall approaching straight in mid chamber and near obverse surface, in some branches slightly sinuous. Chamber longest di- mension parallel to reverse wall in proximodistal di- rection. Autozooecial chamber outline irregularly ovate, elliptical to rounded triangular near reverse wall; be- coming irregularly pentagonal toward mid chamber and an irregular parallelogram to rectangle throughout mid chamber and most of chamber depth; irregularly ovate near obverse surface, slightly enlarged at distal end, longest dimension of ovoid oriented distal-abax- ially; chamber shape highly uniform. Aperture posi- tioned at distal-abaxial or distal end of chamber, con- nected to chamber by well-developed, intermediate- length vestibule of highly variable length. Ratio of au- tozooecial chamber width to depth approximately 7:9; chamber depth to length ratio approximately 3:4; chamber depth and length highly constant, width high- ly variable. Superior and inferior hemisepta both ab- sent. Autozooecial chambers diverge laterally from middle of branch at highly variable angle (mean of 23°); from reverse wall at highly constant angle (mean of 60°). Three-dimensionally reconstructed chamber form an irregular rectangular box, length as viewed from lateral edge of branch; depth, viewed from distal end of branch, moderately greater than width, viewed from obverse surface. Internal granular skeletal layer thick; granular skel- etal layer extremely well-developed, continuous with obverse nodes, stylets, keel, peristome, and reticulate meshwork, which is entirely formed of granular skel- etal material; reverse longitudinal striae and micro- stylets; across dissepiments and in the middle of zoarial supports. Outer lamellar layer extremely thick, exhib- iting pronounced astogenetic thickening, most prom- inent toward proximal end of zoarium. Remarks.—Hemitrypa vermifera was first recog- nized by Ulrich in materials from Geode Glen (War- saw Beds of Ulrich), where this species was considered a new variety of H. hemitrypa. Recognition of this variety was based on “certain peculiar, tubular, ver- miform bodies, which are irregularly distributed over and form part of the reverse face of the zoarium” (Ul- rich, 1890, p. 561). Interior analysis of these features reveals them to be zoarial supports, their tubular na- ture as seen by Ulrich a result of differential preser- vation of outer lamellar versus inner granular skeletal material. Similar supports are present toward the prox- imal end of the zoarium in all species of Hemitrypa, making the use of such criteria for species identification tenuous at best. 122 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 H. vermifera is distinguished from all other species of the genus by having the largest autozooecial cham- bers, largest aperture size, smallest reverse-wall bud- ding-angle, and widest apertural spacing of all species analyzed. The highly granular nature caused by the presence of numerous intermediate-size stylets is high- ly diagnostic of H. vermifera. External mesh similarity between this species and H. hemitrypa is pronounced, probably accounting for inclusion of H. vermifera as a variety of H. hemitrypa by Ulrich, but once interior characters are considered, the differences between the two species are readily apparent. The variety H. prou- tana vermifera is, therefore, elevated to the species H. vermifera herein. Material studied. — Thirty-six exterior fragments, four sectioned specimens; largest zoarial fragment 48 x 33 mm (width to length). The preservation of zoarial frag- ments is good to excellent as a result of the robust nature of zoarium. Physical compaction of branches is rare, although silicification of internal granular skel- etal layer is common. The reticulate meshwork is fre- quently compacted onto the obverse zoarial surface. Occurrence.— Hemitrypa vermifera is present in the northern half of the study area, occurring as far south as Mt. Sterling. In situ occurrences are primarily ob- served in lower energy depositional environments, such as argillaceous micrites and biomicrites. Vermiform features apparently were used as supports in these muddy environments. Syntypes of H. proutana vermifera. — ISGS(ISM) 2815-1. A specimen is illustrated in Ulrich (1890, pl. 57 fips- 5; 5a): Figured and/or measured specimens.—UI X-6880- 6885, 6863—6865 (loc. 11, sample 57). Genus ARCHIMEDES Hall, 1858 Type species.— Fenestella (Archimedes) wortheni Hall, 1857b [Lower Mississippian (Valmeyeran), War- saw Formation]. Diagnosis.— Zoarium robustness delicate to robust, mesh spacing close; tightly coiled central axis present, composed of thickened lamellar skeletal layer formed around lateral spiraling branch from which all mesh originates; chamber outline irregularly pentagonal in mid tangential section, chamber size upper-end small to lower-end intermediate; aperture size intermediate; superior and inferior hemisepta absent; chamber re- verse-wall budding-angle varies between 58° and 70° (means). Three-dimensionally reconstructed chamber form a slightly irregular rectangular box. Description.— Zoarial robustness varying from del- icate to robust, expansion cupped or fan-shaped around tightly coiled central axis, mesh spacing close, regular; central axis present, forms as thickened lamellar skel- etal layer which develops around lateralmost spiraling branch from which all mesh originates. Branch width narrow to intermediate, trace straight as viewed from obverse, sinuous and irregular as viewed from reverse zoarial surface, with reverse sinuous due to secondary thickening of lamellar skeleton; branch surface flat to rounded. Keel present, single, width nar- row, covered by lamellar skeleton with astogeny. Nodes present, emplacement monoserial, size small to inter- mediate, shape circular, ovate to slightly stellate, lo- cated atop keel, spacing close to intermediate. Obverse stylets present, size small, occurring across obverse surface. Microstylets present, small, positioned ini- tially in rows, becoming more variably positioned across branch surface with astogeny. Macrostylets ab- sent. Autozooecia in two rows, third row at sites of branch bifurcation or three rows for distance along branch proximal to branch bifurcation. Heterozooecia (ovicells?) present in some species. Dissepiments of intermediate width, length short, connect branches at regular intervals. Fenestrule size intermediate, shape elliptical on ob- verse surface; elliptical, ovate, circular to square on reverse depending on degree of thickening of lamellar skeleton. Aperture size intermediate, shape varying from cir- cular to ovate to elliptical, oriented parallel to plane of obverse surface. Peristome present, incomplete; ap- ertural stylets present or absent, form as extensions of peristomal edge; terminal diaphragms present, occur- ring toward proximal end of zoarium and adjacent to central axis. Branch shape in cross-section ranging from circular to ovate to elliptical, branches thin to thick in depth. Autozooecial chamber size upper-end small to low- er-end intermediate, chambers biserially emplaced Text-figure 16.— Archimedes wortheni illustrated. 1, diagrammatic longitudinal section showing changing chamber outline from deep section near middle of branch (bottom of figure) to shallow section near abaxial edge of branch (top of figure) [Observe the thickened reverse lamellar skeletal layer (arrow) continuous with the lamellar central axis.], x 70; 2, diagrammatic tangential section illustrating changing chamber outline from deep section near reverse-wall bud- ding-site (bottom of figure) to shallow section near obverse surface (top of figure) [Observe presence of incomplete peristome (arrow) characteristic of this genus.], x 70; 3, diagrammatic transverse sec- tion across branch showing typical aperture orientation (arrow) to plane of obverse surface, x 70; 4, reconstruction of typical chamber shape (three-dimensional) as viewed from abaxial edge of branch, x 140; 5, reconstruction of typical chamber shape (three-dimension- al) as viewed from distal end of branch; chamber reconstructed i$ from the right side of branch, x140; 6, reconstruction of typical chamber shape (three-dimensional) as viewed from obverse surface; chamber reconstructed is from the right side of branch [The smooth, curved outlines of chamber shapes are the result of a lack of hemi- septa.], x 140; 7, reconstruction of tightly coiled central axis, illus- trating mesh radiating outward from spire (arrow), x140. MISSISSIPPIAN BRYOZOANS: SNYDER 123 along sinuous axial wall; maximum chamber length extending proximodistally, parallei to reverse wall. Chamber outline ovate, irregularly pentagonal in mid chamber and throughout most of chamber depth; ir- regularly elliptical to irregularly ovate near obverse Surface. Vestibule present, varying in length from short to intermediate. Superior and inferior hemisepta ab- Sent. Lateral-wall budding-angle ranging from 20° to 27° (means); reverse-wall budding-angle varying from 58° to 70° (means). Lamellar skeletal layer intermediate to thick, exhibiting moderate to pronounced astoge- netic thickening; granular skeletal layer thickness in- termediate to thick, exhibiting no astogenetic thick- ening. Three-dimensionally reconstructed chamber form a slightly irregular rectangular box. Text-figure 16 illustrates zoarial outlines in longi- tudinal, tangential, and transverse orientations, three- dimensional chamber reconstructions from abaxial branch edge, distal, and obverse surface views, and side view of central axis. Remarks.— LeSueur (fide Owen, 1842) was appar- ently the first to apply the name Archimedes to the spiralling screw-like forms found in Mississippian rocks. Owen (1838) referred to Upper ? Mississippian rocks as “Archimedes limestone", recognizing the spiral axis of LeSueur but not offering a formal description. Owen (1842, p. 19) discussed and illustrated as “Retepora Archimedes" a fossil which was “‘ventricillated spirally like a continuous screw”; attributing the name Archi- medes to this form based on the unpublished work of LeSueur. Hall (1857b) described a number of species of Fenestella (Archimedes), providing a loose descrip- tion of the subgenus Archimedes. In 1858, Hall more formally decribed the subgenus, but when describing the species wortheni and reversa elevated the subgenus to the rank of genus. This is therefore the first formal description and species assignment to the described genus present in the literature. The genus is readily recognized by the distinctive tightly spiraling axis at the center of the zoarium, from which the zoarial mesh radiates outward. Both loosely spiraled axes and extremely open spires are represented in several closely related genera. The axis develops as thickened lamellar skeleton around the interlateral col- ony branch, which rotates slightly during growth, giv- ing the spiraled configuration of the axis. Tightness of spiraling appears to have been greatly influenced by environment and thus is not of great importance in species delimitation. Width of spiral also appears to be primarily environmentally influenced, with asto- genetic thickening adding to the lamellar skeletal layer. Accurate determination of species of Archimedes re- quires thorough examination of the axis and zoarial mesh, using both interior and exterior analyses. Species based solely on axes, such as A. grandis Ulrich, 1890, have little or no taxonomic validity, as environmental influence greatly affects axis diameter and whorl spac- ing (McKinney, 1979; McKinney and Gault, 1980). Although the central axis is characteristic of this genus, the outer.appearance of the meshwork is similar in appearance to that of Rectifenestella Morozova, 1974, Laxifenestella, Apertostella, n. gen., and even species of Hemitrypa that lack covering reticulate meshwork. Internally, Archimedes chambers lack hemisepta and can therefore be readily separated from Rectifenestella and Laxifenestella. Pronounced similarities in general chamber shape exist among Archimedes, Apertostella, and Hemitrypa; Archimedes can be separated from the others by its consistently smaller chamber size and incomplete peristome. Although a central axis with attached fronds are most desirable, carefully sectioned axes are adequate for PALAEONTOGRAPHICA AMERICANA, NUMBER 57 identification as all three mesh views (longitudinal, tangential, and transverse) can be obtained. Species composition.—Four species of Archimedes were recognized in the Warsaw: A. negligens Ulrich, 1890, A. owenanus (Hall, 1857b), A. wortheni (Hall, 1857b), and A. valmeyeri, n. sp. Range.— Mississippian to Permian. Archimedes negligens Ulrich, 1890 Plate 50, figures 1-13, Plate 51, figures 1-6, Plate 52, figures 1-4; Table 37 Archimedes negligens Ulrich, 1890, p. 569, pl. 63, figs. 6, 7-7a [Keo- kuk Group, Bentonsport and Keokuk, Iowa]; Condra and Elias, 1944, pp. 79-80, pl. 14, figs. 1-6. Diagnosis.— Zoarium relatively delicate, mesh close, pattern regular; central axis well-developed, robustness delicate to intermediate; volutions dextral or sinistral, diverging from axis at a moderately constant angle (mean of approximately 66°); branch robustness deli- cate to intermediate, width narrow, depth thin; straight on obverse, slightly sinuous on reverse surface; trans- versely ovate to elliptical, becoming increasingly ellip- tical with astogeny, spacing close and joined at mod- erately regular intervals by lower-end intermediate width, short dissepiments. Fenestrule size lower-end intermediate; shape irregularly elliptical on obverse, irregularly elliptical to ovate on reverse; size regular, shape variable. Autozooecial aperture size lower-end intermediate, shape irregularly ovate to elliptical, rare- ly circular, elongate proximoabaxially or proximodis- tally; surrounded by upper-end thin, well-developed, incomplete peristome, opening at proximal to proxi- mal-adaxial edge; two to three (most commonly two) apertures per fenestrule. Single narrow, continuous keel present; keel slightly anastomosing, extending along middle of obverse branch surface, atop which are po- sitioned small nodes; nodes circular to ovate, elongate proximodistally. Autozooecial chamber size lower-end intermediate, chambers emplaced in two rows, except third row at sites of branch bifurcation; outline irreg- ularly ovate near reverse wall, irregularly pentagonal throughout most of chamber depth, irregularly ellip- tical to more rarely irregularly ovate near obverse sur- face. Chamber longest dimension parallel to reverse wall proximodistally. Aperture at distal-abaxial end of chamber, connected to chamber by moderately short, highly variable length vestibule. Superior and inferior hemisepta both absent. Lateral-wall budding-angle variable (mean of approximately 26°); reverse-wall budding-angle highly constant (mean of 65°). Table 37 presents statistical criteria used in delim- iting this species. Exterior description.—Zoarium relatively delicate, forming a flat to slightly cupped, fan-shaped expansion MISSISSIPPIAN BRYOZOANS: SNYDER 125 Table 37.—Summary numerical analysis of Archimedes negligens Ulrich, 1890. For explanation of abbreviations of characters (left column), see Table 8b (foldout inside back cover). number of mea- coeffi- sure- standard cient of observed ments mean deviation variation range 1. WB 24 0.2484 0.0232 9.34 0.215-0.288 2. DBC 24 0.3938 0.0398 10.11 0.333-0.467 3. WD 24 0.1347 0.0249 18.49 0.105—-0.182 4. LF 24 0.4353 0.0820 18.84 0.267-0.550 5. WE 24 0.2000 0.0298 14.90 0.167-0.267 6. AF 24 255 0.49 21.05 2-3 SEN) 24 0.1109 0.0081 7.30 0.096-0.124 8. AW 24 0.0942 0.0086 9.13 0.083-0.108 9. ADB 24 0.1984 0.0163 8.22 0.171-0.233 10. AAB 24 0.1887 0.0205 10.86 0.158-0.222 11. ABB 24 0.2434 0.0387 15.90 0.183-0.320 12. DN 24 0.0529 0.0129 24.39 0.033-0.080 14. SNB 24 0.1450 0.0383 26.41 0.067-0.204 15. WK 24 0.0192 0.0049 25.52 0.013-0.027 16. DSO 24 0.0095 0.0022 23.16 0.006-0.014 17. SSO 24 0.0237 0.0093 39.24 0.010-0.041 18. WP 24 0.0199 0.0061 30.65 0.011-0.031 22. RSS 24 0.0114 0.0026 22.81 0.009-0.018 24. SSS 24 0.0293 0.0111 37.88 | 0.016—0.052 27. WSC 24 5.0 1.38 27.60 2.7-7.2 28. DCA 24 5.1 1.13 21.95 3072 29. ACA 24 65.75 SSA 1752 48—82 30. OL 24 0:1555 0.0230 14.79 0.133-0.182 3l. OW 24 0.1088 0.0122 19:21 0.092-0.120 32. TRW 24 0.0115 0.0029 25.22 0.008-0.022 33. TLW 24 0.0158 0.0029 18.35 0.011-0.020 34. FWT 24 0.1077 0.0524 48.65 0.035-0.229 35. RWT 24 0.0863 0.0626 72.54 0.025-0.257 36. CL 24 02092 0.0122 5.83 0.189-0.229 37. CD 24 0.1252 0.0078 6.23 0.113-0.141 38. MAW 24 0.1249 0.0135 10.81 0.109-0.160 39 MIW 24 0.0643 0.0115 17.88 0.049-0.085 40. VD 24 0.0556 0.0248 44.60 0.022-0.111 41. RA 24 65.08 3.65 5.61 59-71 42. LA oe n. 5.05 19.67 18-36 43. TB 24 0.2738 0.0998 36.45 0.186-0.543 radiating outward from the exterior edge of a spiraling Central axis; mesh spacing close; slight to moderate astogenetic thickening of obverse and reverse zoarial Skeleton; zoarial mesh pattern regular. Central axis ro- bustness delicate to intermediate, well-developed, Maximum diameter moderately variable (mean of 5.14 mm), greatly thickening immediately distal to site of Initial axis development; volution spacing irregular Mean spacing 5 mm), developing into either a dextral °F sinistral spiral; zoarial mesh diverging from central axis at a mean angle of approximately 66°, moderately Constant. Distal end of axial flange flat to slightly con- Cave; proximal side slightly to moderately concave; Oth sides ofaxis with slightly striated texture spiraling around and outward from central axis, resulting from thickening of lamellar skeletal material around axis With astogeny. Probable mature zoarial widths of up to 10 cm, lengths in excess of 20 cm. Branch robustness delicate to intermediate, depend- ing on degree of astogenetic thickening; branch narrow, highly constant in width; straight as observed on ob- verse surface; slightly sinuous on reverse. Branches closely spaced, distance between adjacent branch cen- ters highly regular. Obverse surface texture moderately granular, coarsening with astogeny; surface flat to slightly rounded except for presence of single narrow, intermediately developed keel; keel continuous, slight- ly anastomosing, extending along branch midline, causing slight positive inflection in obverse surface profile. Keel covered by lamellar skeleton with asto- geny. Nodes monoserially emplaced, well-developed, small; shape circular to ovate, elongate proximodis- tally; nodes slightly regular in size and shape, develop as projections from middle of keel; two to five (most commonly three) nodes per fenestrule; nodes closely and slightly unevenly spaced; node diameter moder- ately increasing with astogeny. Small stylets, variably sized and highly variably positioned, occurring across obverse branch surface. Reverse surface texture gran- ular, coarsening with astogeny; bearing relatively few rows of intermediately spaced longitudinal striae which rapidly become covered by lamellar skeleton during astogeny; rows of small microstylets, closely spaced, develop as extensions of longitudinal striae along re- verse branch surface; microstylet diameter moderately increasing with astogeny and microstylets become more variably positioned along reverse branch surface. Au- tozooecia in two rows across branch, except third row at sites of branch bifurcation; branches exhibit slight thickening proximal, slight thinning distal to sites of branch bifurcation. Heterozooecia absent in all zoarial fragments examined. Dissepiments of lower-end intermediate width, ap- proximately five-ninths that of branch, moderately constant; short, constant in length; connect branches at moderately regular intervals. Dissepiments exhibit slight medial thinning, slight flaring at branch-dissep- iment junction; moderately recessed from obverse, ap- proximately even with reverse branch surface. Mod- erate to pronounced astogenetic thickening toward proximal end of zoarium. Obverse dissepiment surface with single longitudinal ridge emplaced perpendicular to branch length; small stylets, similar in size to ob- verse branch stylets, develop across dissepiment sur- face; ridge partially to completely covered by lamellar skeleton during astogeny, stylets slightly increase in diameter; reverse dissepiment surface with relatively few rows of longitudinal striae atop which occur closely spaced rows of small microstylets; longitudinal striae become covered by lamellar skeleton, microstylets be- come more irregularly positioned across dissepiment surface with astogeny. Obverse dissepiment surface 126 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 texture moderately granular, reverse surface texture granular, both coarsening with astogeny. Emplacement of dissepiments perpendicular or at small angle from perpendicular to branch length. Apertures commonly positioned on proximal or distal edge, or in middle of dissepiment edge at branch-dissepiment contact; typ- ically arranged symmetrically, less commonly asym- metrically between branches. Fenestrule size lower-end intermediate; shape irreg- ularly elliptical on obverse surface, irregularly elliptical to ovate, elongate proximodistally on reverse; regular in size, variable in shape; moderately expanding in width and length in obverse-reverse direction. Width of fenestrule four-fifths branch width on obverse sur- face, equal to or slightly greater than branch width on reverse; fenestrule opening size moderately to greatly reduced toward proximal end of zoarium and toward central axis due to astogenetic thickening of lamellar skeleton. Width to length ratio of fenestrule moderately constant, ranging from 1:1 to approximately 1:3; ratio of fenestrule mean width to length approximately 4:9; width slightly more constant than length, both mod- erately constant. Two to three (most commonly two) apertures per fenestrule length; distance between clos- est aperture centers along branch and across branch approximately equal, less than spacing across fenes- trule, which is approximately 1.3 times greater; form- ing an overall moderately even grid of apertures across obverse zoarial surface; spacing along and across branch moderately constant, spacing across fenestrule mod- erately variable. Autozooecial aperture size lower-end intermediate, shape irregularly ovate to elliptical, rarely circular, en- larged slightly at distal end; elongate proximoabaxially or proximodistally; width to length ratio approxi- mately 6:7; size uniform, shape variable, opening ori- ented parallel to plane of obverse surface; aperture surrounded by upper-end thin, well-developed incom- plete peristome; peristome open around one-fourth to one-third of aperture at proximal to proximal-adaxial edge of aperture. Aperture margins extend into fenes- trule, causing moderate to pronounced inflections in fenestrule outline on obverse surface. Centrally thick- ened terminal diaphragms occurring at proximal end of zoarium and near zoarial axis. Zoarial supports moderately well-developed, form- ing as extensions of reverse zoarial surface and distal edge of mesh radiating outward from central axis. Interior description. — Branches irregularly ovate to elliptical in transverse section at distal end of zoarium, elongate parallel to plane of obverse surface, slightly enlarged on obverse surface; with astogeny branches become moderately elongate elliptical in transverse view, elongate in obverse-reverse direction due to ad- dition of lamellar skeleton to reverse branch surface. Branches thin, highly variable in thickness. Autozooecial chamber size lower-end intermediate, chambers biserially arranged along planar branch axial wall; axial wall moderately sinuous near reverse wall and throughout mid chamber, extending toward and connecting with chamber lateral walls; becoming less sinuous near obverse surface. Chamber longest di- mension parallel to reverse wall in proximodistal di- rection. Autozooecial chamber outline irregularly ovate near reverse wall, rapidly becoming irregularly pen- tagonal in mid chamber and throughout most of cham- ber depth; irregularly elliptical to more rarely irregu- larly ovate near obverse surface, slightly enlarged at distal end, longest dimension near obverse surface ori- ented distal-abaxially; chamber shape highly uniform. Aperture positioned at distal-abaxial end of chamber, connected to chamber by well-developed, moderately short vestibule; vestibule highly variable in length. Ra- tio of autozooecial chamber minimum width to max- imum width approximately 1:2; maximum width and depth equal; chamber depth to length ratio approxi- mately 3:5; chamber depth and length highly constant, maximum width slightly variable, minimum width highly variable. Superior and inferior hemisepta both absent. Autozooecial chambers diverge laterally from middle of branch at a variable angle (mean of approx- imately 26°); from reverse wall at a highly constant angle (mean of 65°). Three-dimensionally reconstructed chamber form a slightly irregular rectangular box; long dimension as viewed from lateral edge of branch, approximately twice depth; viewed from distal end of branch, and width, viewed from obverse surface, which are approximately equal. Internal granular skeletal layer thickness interme- diate; granular skeletal layer moderately well-devel- oped, continuous with obverse nodes, stylets, keel, and peristome; reverse longitudinal striae and microstylets, across dissepiments and in the middle of zoarial sup- ports. Outer lamellar layer thickness intermediate, ex- hibiting moderate astogenetic thickening; zoarial cen- tral axis formed from massively accreted lamellar skeleton which completely covers mesh surface at site of and near central axis. Remarks.— Archimedes negligens was named by Ul- rich (1890) from materials collected at Bentonsport and Keokuk, Iowa. Condra and Elias (1944, p. 79) observed that this species had the smallest screw of axis of any pre-Chester species; with Chester species most similar to this form being A. distans Condra and Elias, 1944, A. meekanus Condra and Elias, 1944, and A. terebriformis Condra and Elias, 1944. In general, Chester species are found to have smaller, finer axes than species from Osagean or Meramecian (Valmey- eran) age rocks. MISSISSIPPIAN BRYOZOANS: SNYDER 127 Within the Warsaw fauna, A. negligens most closely resembles A. owenanus (Hall, 1857b). The character- istic smaller size and finer nature of the central axis Separates the former from the latter, however. Internal Chamber characteristics ofthese two species are similar (with the exception of one of the most constant interior characters, reverse-wall budding-angle, which is mod- erately greater in A. negligens). A. negligens can also be differentiated from A. owenanus by the former's lack Of apertural stylets, narrower and thinner branches Which are more closely spaced, smaller fenestrules and therefore fewer apertures per fenestrule length, and Slightly larger apertures. A. negligens and A. owenanus occur concurrently in the same fauna, exhibiting little or no overlap of axis form. Of all zoarial fragments observed, none were found that exhibited characteristic axes of A. negligens Joined to an axis of A. owenanus or other species of Archimedes. Thus, retention of A. negligens as a sep- arate species appears justified in spite of only slight Chamber size dissimilarity from that of A. wortheni. Material studied.—Twenty-four exterior fragments, five sectioned specimens; largest zoarial fragment 3.5x 20 cm (width to length). The preservation of the Central axis is good, due to its moderately robust na- ture, but the preservation of the mesh is intermediate. An interior analysis of the mesh was done only on Samples in which the mesh was still attached to the Central axis, to ensure no confusion in determining the Source of the mesh relative to zoarial axes analyzed. The type specimen had attached meshwork and was analyzed in this way. Occurrence.—Archimedes negligens is a moderately Tare component of the Lower Warsaw and Upper Keo- kuk faunas in the northern half of the study area, hav- Ing its best occurrence near Keokuk. It is found pri- Marily in low-energy environments. Lectotype (herein designated). -ISGS(ISM) 2785-2. Paralectotype (herein designated).—ISGS(ISM) 2785-1, Figured and/or measured specimens.—UI X-7009 (loc. 10, sample 33), 7010 (loc. 6, sample 36), 6975 (loc. 11, sample 52). Archimedes owenanus (Hall, 1857b) Plate 52, figures 5-9, Plate 53, figures 1-10, Plate 54, figures 1-7, Plate 55, figures 1-7, Plate 56, figures 1, 2; Table 38 Fenestella owenana Hall, 1857b, p. 178 [Keokuk Limestone, Keo- kuk, Iowa; Appanoose, Illinois]. Archimedes owenanus (Hall). Ulrich, 1890, p. 570, pl. 63, figs. 6- 6c [Keokuk Group, Keokuk, Iowa; Appanoose, and 3 mi NE of Quincy, Illinois]; Keyes, 1894, p. 26, pl. 33, fig. 2 [Keokuk Lime- Stone, St. Francisville, Missouri]; Condra and Elias, 1944, pp. 92- p» pl. 14, figs. 7-15; Burckle, 1960, pp. 1089-1090, pl. 130, fig. Table 38. — Summary numerical analysis of Archimedes owenanus (Hall, 1857b). For explanation of abbreviations of characters (left column), see Table 8b (foldout inside back cover). number of mea- coeffi- sure- standard cient of observed ments mean deviation variation range 1. WB 24 0.3001 0.0255 8.50 0.260-0.345 2. DBC 24 0.5630 0.0885 15.72 0.449-0.720 3. WD 24 0.2773 0.0507 18.28 0.220-0.400 4. LF 24 0.6215 0.1059 17.04 0.464-0.860 5. WF 24 0.2117 . 0.0435. .20.53 . 0.157—0.285 6. AF 24 3:33 0.49 14.77 3-4 7. AL 24 0.1060 0.0059 5.57 0.096-0.113 8. AW 24 0.0836 0.0083 9.93 0.069—0.094 9. ADB 24 0:22281:5:50:0212 9.52 0.188-0.260 10. AAB 24 0.2028 0.0201 9.91 0.167-0.238 11. ABB 24 0.2684 0.3064 13.00 0.216-0.343 12. DN 24 0.0596 0.0244 40.94 0.026-0.132 14. SNB 24 0.7278 0.1827 -— 25.10 — 0:380—1.120 15. WK 24 0.0184 0.0045 24.46 0.013-0.028 16. DSO 24 0.0090 0.0024 26.67 0.006-0.014 17. SSO 24 0.0259 0.0093 35.91 0.014-0.044 18. WP 24 0.0151. . 0.0035 23.18. 0.011—0.025 19. SA 24 20.58 5.30 2373 14-32 20. SAD 24 0.0087 0.0021 24.14 0.005-0.011 22. RSS 24 0.0158 0.0064 40.51 0.008-0.033 24. SSS 24 0.0373 0.0208 55.76 0.012-0.075 27. WSC 24 9.7 pss 26.21 5.5-14.0 28. DCA 24 10.9 3.69 3847 6.2-19.0 29. ACA 24 68.83 Told 11.28 59-79 30. OL 24 0.3118 0.0618 19.82 0.233-0.429 31. OW 24 0.2240 0.0319 14.24 0.169-0.280 32. TRW 24 0.0178 0.0026 14.61 0.013-0.021 33. TLW 24 0:0131....0:0015.. — 11.45... 0:011-0:016 34. FWT 24 0.0682 0.0465 68.18 0.024-0.182 35. RWT 24 0.2958 0.1634 55.24 0.071-0.629 36. CL 24 0.2199 0.0118 5.37 0.200-0.240 37. CD 24 0.1224 0.0102 8.33 0.104—0.139 38. MAW 24 0.1133 0.0079 6.97 0.096-0.125 39. MIW 24 0.0838 0.0160 19.09 0.057-0.112 40. VD 24 0.0902 0.0352 39.02 0.035-0.138 41. RA 24 59.42 4.90 8.25 52-64 42. LA 24 28.08 4.55 16.20 22-35 43. TB 24 0.5299 0.2058 38.84 0.186-0.915 Archimedes grandis Ulrich, 1890, p. 569, pl. 63, fig. 10 [Keokuk Group, Jersey County, Illinois]. Archimedes halli Condra and Elias, 1944, pp. 97—98, pl. 2, fig. 3; pl. 15, fig. 4. Diagnosis.— Zoarium robust, mesh close, pattern ex- tremely regular; central axis well-developed, robust, volutions dextral or sinistral, diverging from axis at a constant angle (mean of approximately 69°), pillarlike supports between flanges of spiral, branches moder- ately robust, width lower-end intermediate, thick in depth; branches straight on obverse, sinuous and ir- regular on reverse surface; transversely circular to slightly ovate, becoming highly elliptical with asto- geny, spacing close and joined at moderately regular intervals by upper-end intermediate width, short dis- 128 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 sepiments. Fenestrule size intermediate, shape irreg- ularly elliptical on obverse, irregularly elliptical, ovate to circular on reverse; size regular, shape variable. Au- tozooecial aperture size lower-end intermediate, irreg- ularly ovate to elliptical, rarely circular, elongate prox- imoabaxially or proximodistally; surrounded by thin, well-developed, incomplete to more rarely complete peristome, open at proximal to proximal-adaxial edge; three to four (most commonly three) apertures per fe- nestrule. Single narrow, continuous keel present; keel slightly anastomosing to approaching straight, extend- ing along middle of obverse branch surface, atop which are positioned small nodes; nodes ovate, elongate prox- imodistally, rarely circular. Autozooecial chamber size lower-end intermediate, chambers emplaced in two rows, except either third row at sites of branch bifur- cation or more rarely three rows for moderate distances proximal to sites of branch bifurcation; outline irreg- ularly ovate to pentagonal near reverse wall, irregularly pentagonal throughout most of chamber depth; irreg- ularly elliptical to more rarely ovate near obverse sur- face. Chamber longest dimension parallel to reverse wall proximodistally. Aperture at distal-abaxial end of chamber, connected to chamber by intermediate, high- ly variable length vestibule. Superior and inferior hemisepta both absent. Lateral-wall budding-angle moderately variable (mean of approximately 28°); re- verse-wall budding-angle constant (mean of approxi- mately 59°). Heterozooecia (ovicells?) occurring as globular expansions infilling fenestrules. Table 38 presents statistical criteria used in delim- iting this species. Exterior description. — Zoarium robust, forming a flat to slightly cup-shaped expansion radiating outward from the exteriormost edge of a spiraling central axis; mesh spacing close; pronounced astogenetic thickening of obverse and reverse zoarial skeleton; zoarial mesh pattern extremely regular. Central axis robust, well- developed, maximum diameter moderately variable (mean of 10.93 mm), greatly thickening immediately distal to site of initial axis development; volution spac- ing irregular (mean spacing 9.67 mm), developing into either a dextral or sinistral spiral; zoarial mesh di- verging from central axis at a mean angle of approxi- mately 69°, constant. Distal end of axial flange flat, slightly concave, or slightly convex; proximal side slightly to moderately concave; slight striated texture to axis, with striae spiraling around and outward from central axis, resulting from thickening of zoarial skel- eton around axis with astogeny. Pillarlike supports de- veloping between flanges along axis, zoarial mesh over- grown by zoarial skeleton from axis development during astogeny. Probable mature zoarial widths half a meter or more, length greater than 1 m. Branches moderately robust, becoming increasingly so during astogenetic thickening; lower-end interme- diate in width, moderately variable; straight on ob- verse surface, highly sinuous and irregular on reverse surface due to astogenetic thickening of lamellar skel- eton. Branch spacing upper-end close, distance be- tween adjacent branch centers moderately regular. Ob- verse surface texture moderately granular, coarsening with astogeny; surface rounded, except for presence of single narrow, well-developed keel; keel continuous, slightly anastomosing to approaching straight, extend- ing along branch midline, causing slight inflection in obverse surface profile. Keel becomes covered by la- mellar skeleton during astogeny. Nodes monoserially emplaced, well-developed, small; shape ovate, elon- gate proximodistally, rarely circular; nodes highly vari- able in both size and shape; develop as projections from middle of keel; one to three (most commonly two) nodes per fenestrule; node spacing upper-end in- termediate, slightly variable; node diameter greatly in- creasing with astogeny. Upper-end small stylets, vari- ably sized and positioned, occurring across obverse surface. Reverse surface texture granular, coarsening with astogeny; bearing relatively few rows of closely to intermediately spaced longitudinal striae which rapidly become covered by lamellar skeleton during astogeny; rows of small microstylets, closely spaced, develop as extensions of longitudinal striae along reverse branch surface; microstylet diameters highly variable, slightly increase with astogeny and microstylets become vari- ably positioned across reverse branch surface. Auto- zooecia in two rows across branch, except either third row at sites of branch bifurcation, or more rarely three rows extending for moderate distances proximal to sites of branch bifurcation. Heterozooecia (ovicells?) oc- curring as pronounced globular expansions infilling fe- nestrules; mean widths and lengths of polymorphs slightly less than three times autozooecial aperture lengths and widths; polymorph length appreciably greater than width, ratio approximately 5:7; connec- tion between polymorph and autozooecial chamber lacking; polymorphs most commonly situated imme- diately distal from central axis along branch. Dissepiments of upper-end intermediate width, ap- proximately nine-tenths that of branch, moderately constant; short, slightly variable in length; connect branches at moderately regular intervals. Dissepiments exhibit slight medial thinning, slight flaring at branch- dissepiment junction; slightly recessed from obverse, approximately even with reverse branch surface. Pro- nounced astogenetic thickening of dissepiments to- ward proximal end of zoarium. Obverse dissepiment surface with single longitudinal ridge emplaced per- pendicular to branch length; small stylets, similar in size to obverse branch stylets, develop across dissep- iment surface; ridge partially covered by lamellar skel- MISSISSIPPIAN BRYOZOANS: SNYDER 129 eton during astogeny, stylets increase in diameter; re- verse dissepiment surface with an intermediate number of rows of longitudinal striae atop which occur closely Spaced rows of small microstylets; longitudinal striae become covered by lamellar skeleton, microstylets be- come more irregularly positioned across dissepiment Surface with astogeny. Obverse and reverse dissepi- ment surfaces granular, coarsening with astogeny. Em- Placement of dissepiments perpendicular or at small angle from perpendicular to branch length. Apertures commonly positioned on proximal or distal edge, or In middle of dissepiment edge at branch-dissepiment Contact; arranged symmetrically or asymmetrically be- tween branches. Fenestrule size intermediate; shape irregularly ellip- tical on obverse surface, irregularly elliptical to ovate, elongate proximodistally to more rarely circular on reverse; moderately regular in size, irregular in shape; Moderately to highly expanding in width and length in Obverse-reverse direction. Width of fenestrule ap- Proximately one-half branch width on obverse surface, €qual to or slightly greater than branch width on re- verse; fenestrule opening size greatly reduced toward Proximal end of zoarium and toward central axis due to astogenetic thickening of lamellar skeleton. Width to length ratio of fenestrule moderately constant, rang- Ing from 1:1 to approximately 1:4; ratio of fenestrule mean width to length approximately 1:3; length mod- rately constant, width lower-end variable. Three to four (most commonly three) apertures per fenestrule length; distance between closest aperture centers along Tanch and across branch approximately equal, less than spacing across fenestrule which is approximately 1.25 times greater; forming a moderately even grid of apertures across zoarium obverse surface; spacing along and across branch moderately constant, spacing across fenestrule moderately variable. Autozooecial aperture size lower-end intermediate, Shape irregularly ovate to elliptical, rarely circular, en- larged slightly at distal end; elongate proximoabaxially Or proximodistally; width to length ratio approxi- mately 7:9: size uniform, shape variable; opening ori- ented parallel to plane of obverse surface; aperture Surrounded by thin, well-developed, typically incom- Plete peristome; peristome open up to one-fourth of aperture at proximal or proximal-adaxial edge of ap- Crture; more rarely peristome complete. Aperture mar- 8ins extend into fenestrule, causing pronounced in- flections in fenestrule outline on obverse surface. Centrally thickened terminal diaphragms occurring at Proximal end of zoarium and near zoarial axis. Zoarial supports extremely well-developed, forming 35 extensions of reverse zoarial surface and distal edge Of mesh radiating outward from central axis. Interior description. — Branches approaching circular to slightly ovate in transverse section at distal end of zoarium, slightly elongate parallel to plane of obverse surface and enlarged on obverse surface; with astogeny branches become moderately to highly elongate ellip- tical in shape in transverse view, elongate in obverse- reverse direction due to addition of lamellar skeleton to reverse branch surface. Branches thick, highly vari- able in depth. Autozooecial chamber size lower-end intermediate, chambers biserially arranged along planar branch axial wall; axial wall moderately to highly sinuous near re- verse wall and throughout mid chamber, extending toward and connecting with chamber lateral walls; be- coming slightly sinuous near obverse surface. Chamber longest dimension parallel to reverse wall in proxi- modistal direction. Autozooecial chamber outline ir- regularly ovate to pentagonal near reverse wall; irreg- ularly pentagonal in mid chamber and throughout most of chamber depth; irregularly elliptical to more rarely irregularly ovate near obverse surface, slightly to mod- erately enlarged at distal end, longest dimension near obverse surface oriented distal-abaxially; chamber shape highly uniform. Aperture positioned at distal- abaxial end of chamber, connected to chamber by ex- tremely well-developed, intermediate-length vestibule; vestibule highly variable in length. Ratio of autozooe- cial chamber minimum width to maximum width ap- proximately 3:5; maximum width to depth ratio ap- proximately 9:10; chamber depth to length ratio approximately 3:4; chamber maximum width, depth and length highly constant, minimum width highly variable. Superior and inferior hemisepta both absent. Autozooecial chambers diverge laterally from middle of branch at a moderately variable angle (mean of ap- proximately 28?); from reverse wall at constant angle (mean of approximately 59?). Three-dimensionally reconstructed chamber form a slightly irregular rectangular box; length, viewed from lateral edge of branch, greater than depth; viewed from distal end of branch, greater than width, viewed from obverse surface. Internal granular skeletal layer thick; granular skel- etal layer extremely well-developed, continuous with obverse nodes, stylets, keel, and peristome; reverse longitudinal striae and microstylets; across dissepi- ments and in the middle of zoarial supports. Outer lamellar layer extremely thick, exhibiting pronounced astogenetic thickening; zoarial central axis formed of massively accreted lamellar skeleton which completely covers mesh surface at site of and near central axis. Remarks.— Although originally described by Hall, this species was never illustrated by him. For this rea- son, the lectotype [ISGS (ISM) 2782-1] is here desig- nated from specimens illustrated by Ulrich and by Condra and Elias. ISGS (ISM) 2728- 2/3 are assigned 130 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 the status of paralectotypes. A. grandis Ulrich, 1890 and A. halli Condra and Elias, 1944 are herein placed in synonymy under A. owenanus, which has priority. Condra and Elias noted the possibility that A. grandis should be grouped under A. owenanus, but did not do so. Although A. grandis has a slightly wider flaring flange and higher volutions than A. owenanus, interior analysis indicates the two to be essentially identical. Interiors of A. halli were also found to be essentially identical to those of A. owenanus, although A. halli has a smaller axis, prob- ably due to environmental responses. Meshwork for- mulas, as given in Condra and Elias (1944), are also almost identical for A. halli and A. owenanus. This, in conjunction with interior analysis, resulted in placing the two species in synonymy in this study. A. owenanus is extremely similar in both exterior and interior characters to A. wortheni (Hall, 1857b), as noted by Ulrich (1890). The former is differentiated by more numerous apertural stylets (mean of 21 as opposed to 11 in the latter), much lower reverse-wall budding-angle, slightly wider branches, more open mesh, and slightly wider spacing of apertures along, across, and between branches. The overlap in variation of axial characters makes the use of the central axis for species differentiation of little value, although the angle between the distal end of the axis and the axial whorl seems to have some taxonomic significance. This angle is slightly greater in A. owenanus (69°) than in A. wor- theni (61°). Material studied.—Seventy-three exterior frag- ments, 15 sectioned specimens; largest zoarial frag- ment 21x68 cm (width to length). The preservation of the central axis is good, even though the granular skeleton is susceptible to silicification. Interior analysis of zoarial axis and mesh was undertaken only on sam- ples with mesh still attached to the central axis, en- suring there could be no confusion in determining the source of mesh relative to the zoarial axes analyzed. Type material of this species is deposited at the Illinois State Geological Survey. Occurrence.— Archimedes owenanus is abundant in the Upper Keokuk and Lower Warsaw, with best oc- currence at the Warsaw- Keokuk contact, and is found as far south as Jersey County, Illinois. It occurs pri- marily in low-energy environments, less frequently in inferred higher energy environments where zoarial fragments were probably washed in with other clastic particles. Lectotype and paralectotypes. — 1SGS(ISM)2782-1, and ISGS(ISM) 2782-2/3, 2790. Figured and/or measured specimens.—UI X-6972, 6973, 7008, 6986, 6983, 7006, 6971, 7011 (loc. 6, samples 26, 27, 30, 32, 47), 6985, 6984, 7003, 6993, 7013, 7001 (loc. 10, samples 32, 42). Archimedes wortheni (Hall, 1857b) Plate 56, figures 3-9, Plate 57, figures 1-9, Plate 58, figures 1-9, Plate 59, figures 1-5, Plate 60, figures 1, 2; Table 39 Fenestella wortheni Hall, 1857b, p. 178 [Warsaw Limestone, War- saw, Illinois]. Archimedes wortheni (Hall). Hall, 1858, p. 651, pl. 22, figs. 3, 4a- b, 5a-b [Warsaw Limestone, Warsaw, Illinois]; Miller, 1889, p. 292, fig. 452; Ulrich, 1890, p. 571, pl. 63, figs. 8, 8a. [Warsaw Beds, Warsaw, Illinois]; Keyes, 1894, p. 26, pl. 33, fig. 1. [Keokuk Limestone, Wayland and La Grange, Missouri]; Van Tuyl, 1925, pl. 6, fig. 6. Archimedes reversa Hall, 1858, p. 652, pl. 22, fig. 2 [Warsaw Lime- stone, Warsaw, Illinois]. Archimedes welleri Condra and Elias, 1944, pp. 85-88, pl. 18, figs. 4a-b; pl. 19, figs. 1, 2; pl. 20, fig. 5 [Warsaw Formation, Warsaw, Illinois]. Diagnosis. —Zoarium robust, mesh close, pattern ex- tremely regular; central axis well-developed, robust, volutions dextral or sinistral, diverging from axis at moderately constant angle (mean of 61°), pillarlike sup- ports between flanges of spiral; branch robustness in- termediate to pronounced; branch width narrow, depth thick; branches straight on obverse and sinuous on reverse surface; transversely ovate to circular, becom- ing highly elliptical with astogeny, spacing close and joined at highly regular intervals by intermediate-width, short dissepiments. Fenestrule size lower-end inter- mediate; shape irregularly elliptical on obverse, irreg- ularly elliptical, ovate to circular on reverse; size regular, shape variable. Autozooecial aperture size lower-end intermediate, shape irregularly ovate to elliptical, rare- ly circular, elongate proximoabaxially or proximodis- tally; surrounded by thin, well-developed, incomplete peristome, open at proximal to proximal-adaxial edge; intermediate size apertural stylets, seven to 14 per ap- erture (mean of 10.5), positioned atop peristome; two to four (most commonly three) apertures per fenes- trule. Single narrow, continuous keel present; keel slightly anastomosing to approaching straight, extend- ing along middle of obverse branch surface, atop which are positioned small nodes; nodes ovate, highly elon- gate proximodistally, rarely circular. Autozooecial chamber size upper-end small to lower-end interme- diate, chambers emplaced in two rows, except either third row at sites of branch bifurcation or more rarely three rows for moderate distances proximal to sites of branch bifurcation; outline irregularly ovate near re- verse wall, irregularly pentagonal throughout most of chamber depth, irregularly elliptical to ovate near ob- verse surface. Chamber longest dimension parallel to reverse wall proximodistally. Aperture at distal-ab- axial end of chamber, connected to chamber by inter- mediate, highly variable length vestibule. Superior and inferior hemisepta both absent. Lateral-wall budding- angle highly variable (mean of 23°); reverse-wall bud- MISSISSIPPIAN BRYOZOANS: SNYDER 131 Table 39.—Summary numerical analysis of Archimedes wortheni (Hall, 1857b). For explanation of abbreviations of characters (left column), see Table 8b (foldout inside back cover). number of mea- coeffi- sure- standard cient of observed ments mean deviation variation range l. WB 24 0.2620 0.3048 13.28 | 0.220-0.300 2. DBC 24 0.4140 0.0677 16.35 0.357-0.580 3. WD 24 0.1834 0.0277 15.10 0.144-0.255 4. LF 24 0.4353 0.0472 10.84 0.343-0.540 5. WF 24 0.2024 0.0269 13.29 0.167-0.247 6. AF 24 3.08 0.50 16.33 2-4 T. AL 24 0.1019 0.0085 8.34 0.088-0.120 8. AW 24 0.0844 0.0081 9.60 0.071-0.100 9. ADB 24 0.1909 0.0164 8.59 0.169-0.221 10. AAB 24 0.1878 0.0123 6.71 | 0.166-0.214 ll. ABB 24 012133. 5:0,0218 10.22 0.180-0.250 12. DN 24 0.0513 0.0170 33.14 0.031-0.088 14. SNB 24 0.3060 0.0624 20.39 0.225-0.393 15. WK 24 0.0163 0.0070 42.94 0.009-0.026 16. DSO 24 0.0081 0.0022 27.16 0.005-0.012 17. SSO 24 0.0169 0.0064 37.87 0.009-0.029 18. WP 24 0.0221 0.0094 42.53 0.012-0.040 19. SA 24 10.50 2.07 19.68 7-14 20. SAD 24 0.0224 0.0088 39.29 0.009-0.043 22. RSS 24 0.0089 0.0024 26.97 0.006-0.014 24. SSS 24 0.0165 0.0045 27.27 0.011-0.026 27. WSC 24 82 339 41.04 2.9-14.2 28. DCA 24 19.2 11.85 61.75 1.8-48.5 29. ACA 24 60.92 9.15 15.02 48-78 30. OL 24 0.2368 0.0245 10.35 0.205-0.286 31. OW 24 0.1999 0.0188 9.40 0.168-0.235 32. TRW 24 0.0338 0.0074 21.89 0.021-0.044 33. TLW 24 0.0145 0.0024 16.55 0.011-0.019 34. FWT 24 0.0923 0.0407 44.10 0.040-0.165 35. RWT 24 0.2155 0.1686 78.24 0.025-0.550 36. CL 24 0.1746 0.0084 4.81 0.160-0.190 37. CD 24 0.1278 0.0080 6.26 0.115-0.145 38 MAW 24 0.1151 0.0099 8.60 0.098-0.137 39. MIW 24 0.0680 0.0149 21.91 0.049-0.095 40. VD 24 0.0918 0.0444 48.37 0.028-0.140 41. RA 24 70.08 3.78 5.39 63-76 42. LA 22 005750177 4.63 19.98 7232 43. TB 24 0.5123 0.1944 37.95 0.257-0.880 ding-angle highly constant (mean of 70?). Heterozooe- Cla (ovicells?) occurring as pronounced expansions along branch midline and globular expansions infilling fe- hestrules. Table 39 presents statistical criteria used in delim- Ting this species. Exterior description.—Zoarium robust; forming a Slightly cupped, fan-shaped expansion radiating out- ward from the exteriormost edge of a spiraling central Axis; mesh spacing close; pronounced thickening of obverse, extremely pronounced astogenetic thickening Of reverse zoarial skeleton; zoarial mesh pattern ex- tremely regular. Central axis robust, well-developed, Maximum diameter highly variable (mean of 19.19 Mm), greatly thickening immediately distal to site of initial axis development; volution spacing irregular (mean spacing 8.16 mm), developing into either a dex- tral or sinistral spiral; zoarial mesh diverging from central axis at a mean angle of approximately 61°, mod- erately constant. Distal end of axial flange flat to slight- ly concave; proximal side slightly to moderately con- vex; both sides of axis with striated texture spiraling around and outward from central axis, resulting from thickening of lamellar skeletal material around axis with astogeny. Pillarlike supports developing between flanges along axis; zoarial mesh overgrown by zoarial skeleton from axis development during astogeny. Probable mature zoarial widths half a meter or more, lengths in excess of 1 m. Branch robustness intermediate to pronounced, de- pending on degree of astogenetic thickening; branches narrow, moderately constant in width; straight as ob- served on obverse surface; highly sinuous and irregular on reverse surface due to astogenetic thickening of la- mellar skeleton. Branches closely spaced, distance be- tween adjacent branch centers moderately regular. Ob- verse surface texture smooth to slightly granular, coarsening with astogeny; surface irregularly rounded except for presence of single narrow, well-developed keel; keel continuous, slightly anastomosing to ap- proaching straight, extending along branch midline, causing slight to moderate positive inflection in ob- verse surface profile. Keel becomes covered by lamellar skeleton with astogeny. Nodes monoserially emplaced, well-developed, small; shape ovate, highly elongate proximodistally, rarely circular; nodes variable in size and shape; develop as projections from middle of keel; one to three (most commonly two) nodes per fenes- trule; node spacing intermediate, moderately evenly spaced; node diameter increasing with astogeny. Small stylets, variably sized and positioned, occurring across obverse branch surface. Reverse surface texture gran- ular, coarsening with astogeny; bearing relatively few rows of closely to intermediately spaced longitudinal striae which rapidly become covered by lamellar skel- eton during astogeny; rows of small microstylets, close- ly spaced, develop as extensions of longitudinal striae along reverse branch surface; microstylet diameters in- crease slightly with astogeny and microstylets become highly variably positioned across reverse branch sur- face. Autozooecia in two rows across branch, except either third row at sites of branch bifurcation, or more rarely three rows extending for moderate distances proximal to sites of branch bifurcation. Heterozooecia (ovicells?) occurring as pronounced expansions along branch midline and globular expansions infilling fe- nestrules; mean widths and lengths of polymorphs slightly greater than twice autozooecial aperture widths and lengths; polymorph length slightly greater than width, ratio approximately 5:6; connection between 132 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 polymorph and autozooecial chamber lacking; poly- morphs most commonly situated immediately distal from central axis along branch. Dissepiments of intermediate width, approximately seven-tenths that of branch, moderately constant; short, constant in length; connect branches at highly regular intervals. Dissepiments exhibit slight medial thinning, slight flaring at branch-dissepiment junction; slightly recessed from obverse, approximately even with re- verse branch surface. Pronounced astogenetic thick- ening of dissepiments toward proximal end of zoarium. Obverse dissepiment surface with single longitudinal ridge emplaced perpendicular to branch length; small stylets, similar in size to obverse branch stylets, de- velop across dissepiment surface; ridge covered by la- mellar skeleton during astogeny, stylets slightly in- crease in diameter; reverse dissepiment surface with an intermediate number of rows of longitudinal striae atop which occur closely spaced rows of small micro- stylets; longitudinal striae rapidly become covered by lamellar skeleton, microstylets become more irreg- ularly positioned across dissepiment surface with as- togeny. Obverse dissepiment surface texture smooth to slightly granular, reverse surface texture granular, both coarsening with astogeny. Emplacement of dis- sepiments perpendicular or at small angle from per- pendicular to branch length. Apertures commonly po- sitioned on proximal or distal edge, or in middle of dissepiment edge at branch-dissepiment contact; typ- ically arranged symmetrically, less commonly asym- metrically between branches. Fenestrule size lower-end intermediate; shape irreg- ularly elliptical on obverse surface, irregularly elliptical to ovate, elongate proximodistally, to more rarely cir- cular on reverse; regular in size, variable in shape; moderately to highly expanding in width and length in obverse-reverse direction. Width of fenestrule two- thirds branch width on obverse surface, appreciably greater than branch width on reverse; fenestrule open- ing size greatly reduced toward proximal end of zoar- ium and toward central axis due to astogenetic thick- ening of lamellar skeleton. Width to length ratio of fenestrule moderately constant, ranging from 1:1 to approximately 1:3; ratio of fenestrule mean width to length approximately 7:9; length slightly more constant than width, both highly constant. Two to four (most commonly three) apertures per fenestrule length; dis- tance between closest aperture centers along branch and across branch approximately equal, slightly less than spacing across fenestrule which is approximately 1.1 times greater; forming an overall even grid of ap- ertures across zoarium obverse surface; spacing along and across branch and across fenestrule all moderately constant. Autozooecial aperture size lower-end intermediate, shape irregularly ovate to elliptical, rarely circular, en- larged slightly at distal end; elongate proximoabaxially or proximodistally; width to length ratio approxi- mately 5:6; size moderately uniform, shape variable; opening oriented parallel to plane of obverse surface; aperture surrounded by thin, well-developed incom- plete peristome; peristome open around one-fourth to one-third of aperture at proximal to proximal-adaxial edge of aperture. Intermediate-size apertural stylets de- velop as projections from peristome, seven to 14 per aperture (mean of 10.5); apertural stylets highly vari- able in size and number. Aperture margins extend into fenestrule, causing pronounced inflections in fenestrule outline on obverse surface. Centrally thickened ter- minal diaphragms occurring at proximal end of zoar- ium and near zoarial axis. Zoarial supports extremely well-developed, forming as extensions of reverse zoarial surface and distal edge of mesh radiating outward from central axis. Interior description.—Branches ovate to circular in transverse section at distal end of zoarium, elongate parallel to plane of obverse surface, slightly enlarged on obverse surface; with astogeny branches become moderately to highly elongate-elliptical in shape in transverse view, elongate in obverse-reverse direction, due to pronounced addition of lamellar skeleton to reverse branch surface. Branches thick, variable in depth. Autozooecial chamber size upper-end small to low- er-end intermediate, chambers biserially arranged along planar branch axial wall; axial wall moderately sinuous near reverse wall and throughout mid chamber, ex- tending toward and connecting with chamber lateral walls; becoming very slightly sinuous near obverse sur- face. chamber longest dimension parallel to reverse wall in proximodistal direction. Autozooecial chamber outline irregularly ovate near reverse wall, rapdily be- coming irregularly pentagonal in mid chamber and throughout most of chamber depth; irregularly ellip- tical to more rarely irregularly ovate near obverse sur- face, slightly enlarged at distal end, longest dimension near obverse surface oriented distal-abaxially; cham- ber shape highly uniform. Aperture positioned at dis- tal-abaxial end of chamber, connected to chamber by extremely well-developed, intermediate-length vesti- bule; vestibule highly variable in length. Ratio of au- tozooecial chamber minimum width to maximum width approximately 3:5; maximum width and depth about equal, ratio of 9:10; chamber depth to length ratio approximately 3:4; chamber maximum width, depth and length highly constant, minimum width highly variable. Superior and inferior hemisepta both absent. Autozooecial chambers diverge laterally from middle of branch at a highly variable angle (mean of 23°); from reverse wall at highly constant angle (mean MISSISSIPPIAN BRYOZOANS: SNYDER 133 of 70°). Three-dimensionally reconstructed chamber form a Slightly irregular rectangular box; length, viewed from lateral edge of branch, greater than depth, viewed from distal end of branch; which in turn is slightly greater than width, viewed from obverse surface. Internal granular skeletal layer thick; granular skel- etal layer extremely well-developed, continuous with obverse nodes, stylets, keel, peristome, and apertural Stylets; reverse longitudinal striae and microstylets; across dissepiments and in the middle of zoarial sup- Ports. Outer lamellar layer extremely thick, exhibiting Pronounced astogenetic thickening; zoarial central axis formed of massively accreted lamellar skeleton which Completely covers mesh surface at site of and near central axis. Remarks.—A. wortheni was described by Hall from the Warsaw beds near Warsaw, Illinois. A. reversa Hall, 1858 was later differentiated by Hall as a species having a sinistral, rather than dextral spiraling axis, as in A. wortheni. The direction of the axis spiral was consid- ered an invalid criterion for species differentiation by Ulrich (1890), and he placed the two species in syn- Onymy under A. wortheni, which had priority. Dextral and sinistral spiraling axes can both be observed in the Same zoarium, therefore I am in agreement with Ulrich 1n placing these two species in synonymy with A. wor- theni. Ulrich (1890, pp. 571-572) criticized Hall for de- Scribing A. wortheni as having “three rows of apertures below a bifurcation, and sometimes with zooecia on the dissepiments", saying both assertions were based on “defective observation”. In my work with over 80 axes having meshwork attached, I found numerous examples of branches having three rows present prox- mal to sites of branch bifurcation as well as occurrence of aperture opening on the edges of dissepiments. Ul- Tich’s apparent overreliance on the central axis for spe- Cles assignment in Archimedes Hall, 1858 probably led is his not observing these characters, and thus his crit- Icısm of Hall is doubly unjustified. Archimedes welleri Condra and Elias, 1944 was based On Keyes’ largest specimen and Van Tuyl’s described materials. Condra and Elias' criteria for establishing this species are greater length and larger size of axial flange, and development of prominent nodes in A. wel- leri. These criteria all represent axis and branch char- acters that greatly increase during zoarial astogeny; the Mesh spacing and other criteria listed for species dif- *rentiation are essentially identical between A. welleri and A. wortheni. For these reasons, A. welleri is herein Placed in synonymy with A. wortheni, which has pri- Ority, A. wortheni is distinguished from A. owenanus (Hall, 1857p), the most similar Warsaw species of Archi- medes analyzed, by substantially smaller autozooecial chamber size, fewer apertural stylets, higher reverse- wall budding-angle, narrower branches, more tightly closed mesh, closer aperture spacing along, across and between branches, and slightly smaller angle between the distal end of the axis and axial whorl. Other tax- onomic criteria are similar between these two species, suggesting close phylogenetic affinities. Material studied.—Eighty-four exterior fragments, 20 sectioned specimens; largest zoarial fragment 30 x 108 cm (width to length). The preservation of the central axis is excellent due to its highly robust nature; the preservation of the mesh is moderately good. In- terior analyses of the zoarial axis and mesh were un- dertaken only on samples in which the mesh was still attached to the central axis, thus assuring no confusion in determining the source of mesh relative to zoarial axes. Occurrence.— Archimedes wortheni is an abundant component of the Upper Warsaw fauna in the northern half of the study area, having its most abundant oc- currence in Geode Glen (Warsaw Beds) at Warsaw. It is found primarily in rocks deposited in lower-energy environments, such as argillaceous biocalcilutites and shales; it rarely occurs in biocalcarenites. Holotype.—AMNH 7525/1 (Hall Coll. 5058/1). Topotypes. — ISGS(ISM) 10636, ISGS(ISM) 2780-1/2, UI X-28-1/3. Figured and/or measured specimens. — UI X-7005, 7012, 7004, 7014, 6995-7000, 6874, 6991, 6992, 7002 (loc. 11, samples 48, 50, 51, 58, 61, 63), 6990, 6994, 7007, 7008 (loc. 29, sample 5). Archimedes valmeyeri, new species Plate 60, figures 3-9, Plate 61, figures 1-8, Plate 62, figures 1-6; Table 40 Etymology of name. — Named for the species’ prime area of occurrence: Valmeyer, Illinois. Diagnosis.— Zoarium moderately robust, mesh close, pattern extremely regular; central axis well-developed, moderately robust, volutions dextral or sinistral, di- verging from axis at moderately constant angle (mean of approximately 43?), pillarlike supports between flanges of spiral; branch robustness pronounced, width intermediate, thick in depth; branches straight on ob- verse and sinuous on reverse surface; transversely cir- cular to ovate, becoming highly elliptical with asto- geny, spacing close and joined at highly regular intervals by intermediate-width, short dissepiments. Fenestrule size lower-end intermediate; shape irregularly elliptical on obverse, irregularly elliptical to ovate, to more rare- ly circular to square on reverse; size and shape both variable. Autozooecial aperture size lower-end inter- mediate, shape symmetrically circular, irregularly cir- cular to slightly ovate, elongate slightly proximodis- 134 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 tally, proximoabaxially, or perpendicular to direction of branch growth; surrounded by thin, well-developed complete or incomplete peristome, open at proximal to proximal-adaxial edge; small apertural stylets, seven to 16 per aperture (mean of 11.5), positioned atop peristome; two to three (most commonly three) aper- tures per fenestrule. Single narrow, continuous keel present; keel slightly anastomosing to approaching straight, extending along middle of obverse branch sur- face, atop which are positioned intermediate-size nodes; nodes circular, ovate to slightly stellate, slightly elon- gate proximodistally. Autozooecial chamber size low- er-end intermediate, chambers emplaced in two rows, except either third row at sites of branch bifurcation or more rarely three rows for moderate distances prox- imal to sites of branch bifurcation; outline irregularly ovate to rounded triangle near reverse wall, irregularly pentagonal throughout most of chamber depth, irreg- ularly elliptical to more rarely irregularly ovate near obverse surface. Chamber longest dimension parallel to reverse wall proximodistally. Aperture at distal-ab- axial end of chamber, connected to chamber by inter- mediate, highly variable length vestibule. Superior and inferior hemisepta both absent. Lateral-wall budding- angle highly variable (mean of approximately 20°); re- verse-wall budding-angle highly constant (mean of 58°). Heterozooecia (ovicells?) occurring as pronounced globular expansions infilling fenestrules. Table 40 presents statistical criteria used in delim- iting this species. Exterior description.—Zoarium moderately robust; forming a slightly cupped, fan-shaped expansion ra- diating outward from the exteriormost edge of a spi- raling central axis; mesh spacing close; pronounced astogenetic thickening of obverse, extremely pro- nounced astogenetic thickening of reverse zoarial skel- eton; zoarial mesh pattern extremely regular. Central axis moderately robust, well-developed, maximum di- ameter highly variable (mean of 14.48 mm), exhibiting pronounced thickening immediately distal to site of initial axis development; volution spacing irregular (mean spacing 3.77 mm), developing into either a dex- tral or sinistral spiral; zoarial mesh diverging from central axis at a mean angle of approximately 43°, mod- erately constant. Distal end of axial flange flat or slight- ly concave; proximal side flat to slightly concave; both sides of axis exhibiting striated texture spiraling around and outward from central axis, resulting from thick- ening of lamellar skeletal material around axis with astogeny. Pillarlike supports rare, develop between flanges along axis; zoarial mesh overgrown by zoarial skeleton from axis development during astogeny. Probable mature zoarial width up to 20 cm, length of 50 cm. Branch robustness pronounced; width intermediate, Table 40.—Summary numerical analysis of Archimedes valmeyeri, n. sp. For explanation of abbreviations of characters (left column), see Table 8b (foldout inside back cover). number of mea- coeffi- sure- standard cientof observed ments mean deviation variation range 1. WB 24 0.3716 0.0769 20.69 0.225-0.505 2. DBC 24 0.4818 0.0553 11.48 0.431-0.575 3. WD 24 0.2317 0.0390 16.83 0.194-0.306 4. LF 24 0.4786 0.1204 25.16 0.350-0.675 5. WF 24 0.2425 0.0801 33.03 0.105-0.363 6. AF 24 2.67 0.49 18.46 2-3 7. AL 24 0.1112 0.0086 7.73 0.096-0.127 8. AW 24 0.0872 0.0126 14.45 0.069-0.105 9. ADB 24 0.2198 0.0154 7.001 0.196-0.246 10. AAB 24 0.2407 0.0252 10.47 0.208-0.293 11. ABB 24 0.2687 0.0521 19.39 0.169-0.365 12. DN 24 0.0923 0.0243 26.33 0.055-0.140 13. DND 24 0.0860 0.0241 28.02 0.055-0.132 14. SNB 24 0.1652 0.0437 26.45 0.090-0.224 15. WK 24 0.0187 0.0028 14.97 0.015-0.023 16. DSO 24 0.0081 0.0019 23.46 0.005-0.012 17. SSO 24 0.0218 0.0092 42.20 0.011-0.039 18. WP 24 0.0154 0.0052 33.77 0.011-0.027 19. SA 24 10750 2.61 2/20 0) 7-16 20. SAD 24 0.0140 0.0054 38.57 0.009-0.026 222 RSS 24 0.0099 0.0036 36.36 0.006-0.019 24. SSS 24 0.0158 0.0079 50.00 0.008-0.034 27. WSC 24 14.5 37 45.92 3.2-26.4 28. DCA 24 3.8 1.1 28.52 2.7-6.1 29. ACA 24 42.58 4.19 9.84 38-52 30. OL 16 0.2594 0.0305 11.76 0.212-0.290 31. OW 16 0.2096 0.0921 15.31 0.199-0.299 32. TRW 24 0.0129 0.0024 18.60 0.008-0.016 33. TLW 24 0.0135 0.0025 18.52 0.010-0.018 34. FWT 24 0.1396 0.0726 52.01 0.043-0.292 35. RWT 24 0.2926 0.1646 56.25 0.086-0.686 36. CL 24 0.2293 0.0110 4.80 0.214-0.251 37. CD 24 0.1382 0.0101 7.31 0.124-0.158 38. MAW 24 0.1193 0.1097 8.13 0.105-0.140 39. MIW 24 0.0681 0.0110 16.15 0.050-0.088 40. VD 24 0.1030 0.0351 34.08 0.039-0.143 41. RA 24 58.0 3.67 6.32 51-64 42. LA 24 19.67 6.39 32.47 10-30 43. TB 24 0.5685 0.1598 28.11 0.286-0.852 variable, depending on degree of astogenetic thickening of lamellar skeleton; straight as observed on obverse surface, highly sinuous and irregular on reverse surface due to astogenetic thickening of lamellar skeleton. Branch spacing close, distance between adjacent branch centers highly regular. Obverse surface texture slightly granular, coarsening with astogeny; surface rounded, except for presence of single narrow, well-developed keel; keel continuous, straight to slightly anastomosing, extending along branch midline, causing slight to mod- erate positive inflection in obverse surface profile. Keel covered by lamellar skeleton with astogeny. Nodes monoserially emplaced, well-developed, size inter- mediate; shape circular, ovate to slightly stellate, elon- MISSISSIPPIAN BRYOZOANS: SNYDER 135 gate proximodistally; nodes variable in size, highly variable in shape; develop as projections from middle of keel; four to seven (most commonly five or six) nodes per fenestrule; node spacing close, moderately unevenly spaced; node diameter increasing with as- togeny. Small stylets, variably sized and highly vari- ably positioned, occurring across obverse branch sur- face. Reverse surface texture granular, coarsening with astogeny; bearing an intermediate number of closely to intermediately spaced longitudinal striae which rap- idly become covered by lamellar skeleton during as- togeny; rows of small microstylets, closely spaced, de- velop as extensions of longitudinal striae along reverse branch surface; microstylets variable in size, diameters Increase with astogeny; microstylets become highly variably positioned across reverse branch surface. Au- tozooecia in two rows across branch, except either third TOW at sites of branch bifurcation, or more rarely three Tows extending for short to moderate distances prox- imal to sites of branch bifurcation. Heterozooecia (ovi- Cells?) occurring as pronounced globular expansions Infilling fenestrules; mean widths and lengths of poly- Morphs slightly greater than twice autozooecial aper- ture widths and lengths; polymorph length moderately greater than width, ratio approximately 4:5; connec- tion between polymorph and autozooecial chamber lacking: polymorphs most commonly located imme- diately distal from central axis along branch. Dissepiments of intermediate width, approximately five-eighths that of branch, moderately constant; short, Moderately constant in length; connect branches at Moderately regular intervals. Dissepiments exhibit Slight medial thinning, slight flaring at branch-dissep- Iment junction; slightly recessed from obverse, ap- Proximately even with reverse branch surface. Ex- tremely pronounced astogenetic thickening of dissepiments toward proximal end of zoarium. Ob- verse dissepiment surface with single longitudinal ridge emplaced perpendicular to branch length; one to three (most commonly two) intermediate-size stylets devel- OP as extensions of ridge; small stylets, similar in size to obverse branch stylets, develop across dissepiment Surface; ridge covered by lamellar skeleton, nodes and Stylets increase in diameter during astogeny; reverse dissepiment surface with an intermediate number of rows of longitudinal striae atop which occur closely Spaced rows of small microstylets; longitudinal striae Tapidly become covered by lamellar skeleton, micro- Stylets become more irregularly positioned across dis- Sepiment surface with astogeny. Obverse dissepiment Surface texture slightly granular, reverse surface texture Sranular, both coarsening with astogeny. Emplacement 9f dissepiments perpendicular to moderate angle from Perpendicular to branch length. Apertures commonly Positioned on proximal or distal edge, or in middle of dissepiment edge at branch-dissepiment contact; ar- ranged symmetrically or asymmetrically between branches. Fenestrule size lower-end intermediate; shape irreg- ularly elliptical on obverse surface, irregularly elliptical to ovate, elongate proximodistally, to more rarely cir- cular to square on reverse; variable in both size and shape; moderately to highly expanding in width and length in obverse-reverse direction. Width of fenes- trule approximately two-thirds branch width on ob- verse surface, appreciably greater than branch width on reverse; fenestrule size greatly reduced toward prox- imal end of zoarium, toward central axis, and toward distal edge of mesh where zoarial supports develop, due to pronounced astogenetic thickening of lamellar skeleton. Width to length ratio of fenestrule moderately to highly variable, ranging from approximately 1:1 to 1:6; ratio of fenestrule mean width to length approx- imately 1:2; length slightly more constant than width, both highly variable. Two to three (most commonly three) apertures per fenestrule length; distance between closest aperture centers along branch approximately nine-tenths distance along branch, spacing across fe- nestrule approximately 1.2 times greater than distance between closest apertures along branch; spacing along and across branch moderately constant, spacing across fenestrule variable. Autozooecial aperture size lower-end intermediate, shape symmetrically circular, irregularly circular to slightly ovate, enlarged slightly at distal end; elongate slightly proximodistally, proximoabaxially, or perpen- dicular to direction of branch growth; where elongate, width to length ratio approximately 7:9; length mod- erately uniform, width moderately variable, shape variable; opening oriented parallel to plane of obverse surface; aperture surrounded by thin, well-developed complete or incomplete peristome; where incomplete, peristome open up to one-fourth of aperture at prox- imal to proximal-adaxial edge of aperture. Small ap- ertural stylets develop as projections from peristome, seven to 16 per aperture (mean of 11.5); apertural sty- lets highly variable in size and number. Aperture mar- gins extend into fenestrule, causing pronounced in- flections in fenestrule outline on obverse surface. Centrally thickened terminal diaphragms occurring at proximal end of zoarium and near zoarial axis. Zoarial supports extremely well-developed, forming as extensions of reverse zoarial surface and distal edge of mesh radiating outward from central axis. Lamellar skeleton on supports developing at lateral edge of mesh frequently covers apertures and fills fenestrules. Interior description. — Branches circular to ovate in transverse section at distal end of zoarium and away from central axis, elongate parallel to plane of obverse surface, slightly enlarged on obverse surface; with as- 136 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 togeny branches become moderately to highly elon- gate-elliptical in shape in transverse view, elongate in obverse-reverse direction due to pronounced addition of lamellar skeleton to reverse branch surface. Branch- es thick, variable in depth. Autozooecial chamber size lower-end intermediate, chambers biserially arranged along planar branch axial wall; axial wall highly sinuous near reverse wall, be- coming moderately sinuous throughout mid chamber, extending toward and connecting with chamber lateral walls; becoming very slightly sinuous to approaching straight near obverse surface. Chamber longest dimen- sion parallel to reverse wall in proximodistal direction. Autozooecial chamber outline irregularly ovate to rounded triangle near reverse wall, rapidly becoming irregularly pentagonal in mid chamber and throughout most of chamber depth; irregularly elliptical to more rarely irregularly ovate near obverse surface, slightly enlarged at distal end, longest dimension near obverse surface oriented distal-abaxially, chamber shape highly uniform. Aperture positioned at distal-abaxial end of chamber, connected to chamber by extremely well- developed, intermediate-length vestibule; vestibule highly variable in length. Ratio of autozooecial cham- ber minimum width to maximum width approxi- mately 4:7; maximum width slightly less than depth, ratio about 6:7; chamber depth to length ratio ap- proximately 3:5; chamber maximum width, depth and length highly constant, minimum width highly vari- able. Superior and inferior hemisepta both absent. Au- tozooecial chambers diverge laterally from middle of branch at a highly variable angle (mean of approxi- mately 20°); from reverse wall at highly constant angle (mean of 58°). Three-dimensionally reconstructed chamber form a slightly irregular rectangular box; length, viewed from lateral edge of branch substantially greater than depth, viewed from distal end of branch; which is slightly greater than width, viewed from obverse surface. Internal granular skeletal layer thick; granular skel- etal layer extremely well-developed, continuous with obverse nodes and nodes occurring on dissepiments, stylets, keel, peristome, and apertural stylets; reverse longitudinal striae and microstylets; across dissepi- ments and in the middle of zoarial supports. Outer lamellar layer extremely thick, exhibiting pronounced astogenetic thickening; zoarial central axis formed of massively accreted lamellar skeleton which completely covers mesh surface at site of and near central axis. Remarks.—The chamber shape, size, and placement of A. valmeyeri closely resemble those of A. owenanus. A. valmeyeri is distinguished by shorter and slightly wider fenestrule openings, wider and deeper branches, slightly larger aperture openings, greater spacing of ap- ertures along, across, and between branches, fewer ap- ertural stylets (similar in number to A. wortheni), much more numerous and closely spaced nodes atop keel along obverse surface, and appreciably lower angle be- tween the distal end of the axis and the axial whorl. Autozooecial chamber size is very similar between A. valmeyeri and A. owenanus, suggesting extremely close phylogenetic positioning of these two species. Extremely well-developed supports at the distal end of the zoarial mesh suggest 4. valmeyeri was highly specialized for growth in a muddy substrate or sup- ported itself by resting on shells. Such supports are found only in this species of Archimedes Hall, 1858 and are useful for species recognition in the field. Material studied.—Fourty-one exterior fragments, 11 sectioned specimens; largest zoarial fragment 16 X 34 cm (width to length). The preservation of the central axis is generally good, although frequently axes are partially silicified, probably due to the presence of moderately abundant detrital clays, which acted as a source of silica. Interior analyses of mesh were under- taken only on samples in which the mesh was still attached to the central axis, minimizing confusion in determining the source of the mesh relative to the zoar- ial axes analyzed. Occurrence.—Archimedes valmeyeri is a moderately abundant component of the Warsaw fauna in the southern part of the study area, occurring throughout the Warsaw at the Valmeyer and St. Louis localities, and found as far north as White Hall. It occurs pri- marily in low-energy environments, in argillaceous biocalcilutites and shales, and more rarely in biocal- carenites. Holotype.— UI X-6987 (loc. 49B, sample 13). Paratypes.— UI X-6988, 6989 (loc. 47A, sample 35), 6976-6982, 6946 (loc. 49B, samples 10, 12, 15, 20). Family POLYPORIDAE Vine, 1884 Zoaria robust, fan-shaped, constructed of branches bifurcating at regular to variable intervals. Dissepi- ments connect branches at varying distances (trans- verse links lacking autozooecial chambers) which may or may not have apertures opening onto the dissepi- ments at branch-dissepiment edge. Each individual (autozooecium) with a single apertural opening; open- ings occurring on one side of fan, the front or obverse surface, the back or reverse surface being without ap- ertural openings. Three to seven rows of zooecia typ- ically present across each branch. Exterior obverse OT“ namentation can consist of longitudinal keels [rarely occurring in the polyporids and referred to as carina by some authors]; nodes of various forms positioned along branch surfaces and/or on dissepiments; stylets positioned down the branch, on dissepiments and/or around apertures; peristomal structures and hetero” zooecial features. Reverse exterior surfaces frequently MISSISSIPPIAN BRYOZOANS: SNYDER 137 with longitudinal striae, microstylets and macrostylets of varying sizes, zoarial supports, and exhibiting pro- nounced astogenetic changes. Interior features include typical autozooecial chamber shape and orientation (elongate chamber characteristically emplaced at an acute angle to reverse wall), infrequent presence of su- Perior hemiseptum (adjacent to obverse interior wall), vestibule and terminal diaphragms. Range.— Ordovician to Permian. Genera included.—The Warsaw genera Polypora McCoy, 1844, and Fenestralia Prout, 1858a, are in- Cluded in this family. Genus FENESTRALIA Prout, 1858a Type species.—Fenestralia sanctiludovici Prout, 1858a [Mississippian, Meramec, Missouri]. Diagnosis.—Zoarium robust, mesh spacing close to Open; chamber outline irregularly pentagonal, rectan- gular or a parallelogram in mid tangential section, Chamber size intermediate; chambers emplaced in two adaxial and two abaxial rows away from medial axial wall from which keel develops; aperture size inter- Mediate; superior hemiseptum poorly developed, in- ferior hemiseptum absent; chamber reverse-wall bud- ding-angle 42° (mean), adaxial zooecia bud from reverse 20arial wall, abaxial zooecia bud from two rows of abaxial axial walls. Three-dimensionally reconstructed chamber form a Slightly rectangular tube. Description.— Zoarium robust, expansion flat to ob- versely curved, mesh spacing varying from close to Open, irregular. Branches wide, straight to sinuous in trace with lat- eral branches broadly curved toward edge of zoarium; branch surface rounded. Keel present, single, width Intermediate, thickening with astogeny and frequently Covered by lamellar skeleton. Nodes present, emplace- ment monoserial, large, shape ovate to elliptical, lo- ‘ated in middle of keel, spacing intermediate. Obverse Stylets present, size intermediate, occurring across ob- Verse surface. Microstylets present, small. Macrostylets absent, Autozooecia in four rows, two rows on each Side of medial keel; five to six rows of autozooecia at Sites of branch bifurcation or for distance along branch Proximal to site of branch bifurcation. Heterozooecia (Ovicells?) present. Dissepiments of intermediate width, length inter- Mediate, connnect branches at regular intervals. €nestrule size intermediate to large, shape elliptical to ovate, Aperture size intermediate, shape circular to ovate; Adaxial two rows oriented approximately parallel to plane of obverse suface, abaxial two rows oriented ap- Proximately perpendicular to plane of obverse surface. eristome present, complete; apertural stylets absent; terminal diaphragms present, located throughout zoar- ium. Branch shape circular, ovate to polygonal in cross- section, thick in depth. Autozooecial chamber size intermediate, chambers arranged in four rows, two adaxial and two abaxial, along three straight to slightly sinuous axial walls; mid axial wall separates adaxial rows of zooecia, lateral axial walls form reverse wall for abaxial rows of zooe- cia; maximum chamber length parallel to proximal and distal lateral chamber walls. Chamber outline ovate near reverse wall; becoming rectangular to parallelo- gram-shaped to more rarely irregularly pentagonal in mid chamber and throughout most of chamber depth; bilobate-ovate near obverse surface. Vestibule present, length intermediate. Superior hemiseptum present, poorly developed at proximal-abaxial vestibular edge; inferior hemiseptum absent. Adaxial lateral-wall bud- ding-angle 17° (mean); abaxial lateral-wall budding- angle 51° (mean); reverse-wall budding-angle the same for both adaxial and abaxial rows of zooecia (mean of 42°). Lamellar skeletal layer thickness intermediate, exhibiting moderate astogenetic thickening; granular skeletal layer thickness intermediate, exhibiting no as- togenetic thickenings. Three-dimensionally reconstructed chamber form a slightly rectangular tube. Text-figure 17 illustrates zoarial outlines in longi- tudinal, tangential, and transverse orientations, and three-dimensional chamber reconstructions from dis- tal, abaxial edge of branch, and obverse surfaces. Remarks .—Fenestralia was described by Prout (1858a) from Warsaw materials collected near Mera- mec, Missouri. Members of this genus are readily rec- ognized in exterior view by the pronounced median keel from which two rows of autozooecia develop on either side. Particular care must be taken in sectioning and ori- enting specimens of Fenestralia, as adaxial chambers are oriented parallel to the obverse surface and abaxial chambers are oriented perpendicular to the obverse surface. When taking this into consideration when sec- tioning, one finds adaxial and abaxial chambers to be identical in shape. Only a single species, F. sanctiludovici, is known. The distinctive nature of abaxial zooecial budding from lateral rows of axial walls is not found in any other fenestrate, a feature that warrants generic recognition. Fenestralia can be distinguished from Polypora Mc- Coy, 1844, the most similar genus, by presence of a keel along the middle of the branch obverse surface, lack of apertural stylets, abaxial rows of zooecia bud- ding from lateral rows of axial walls, and presence of a superior hemiseptum. Significant similarities in chamber shape exist. 138 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 Species composition.—F. sanctiludovici is the only known species. Range.—Mississippian; restricted to the Kinder- hookian and the Valmeyeran. Fenestralia sanctiludovici Prout, 1858a Plate 63, figures 1-10, Plate 64, figures 1-8; Table 41 Fenestralia St. Ludovici Prout, 1858a, p. 235, pl. 15, figs. 1-1a. Fenestralia sancti-ludovici Prout. Ulrich, 1890, p. 604, pl. 55, fig. 5 [St. Louis Group and Warsaw Beds: St. Louis and Barrett's Station, Missouri; Monroe County, Alton, Columbia, and Warsaw, Illi- nois]; Simpson, 1895b, p. 717, fig. 62; Burckle, 1960, pp. 1090- 1091, pl. 12a, figs. 6, 12. Fenestralia? sancti-ludovici Prout. Keyes, 1894, p. 30 [St. Louis Limestone: St. Louis, Missouri]. Diagnosis.—Zoarium robust, mean mesh spacing lower-end intermediate, varying from close to open, pattern moderately to highly irregular; branches ro- bust, width wide, extremely thick in depth; branches straight to slightly sinuous, broadly curved at lateral zoarial edge; transversely circular, irregularly circular, ovate to polygonal, spacing intermediate to close; branches joined at moderately constant intervals by intermediate-width, intermediate-length dissepi- ments. Fenestrule size large; shape irregularly elliptical to rarely irregularly ovate, moderately variable. Au- tozooecial aperture size lower-end intermediate, shape symmetrically circular, irregularly circular to irregu- larly ovate, slightly elongate proximodistally to prox- imoabaxially, surrounded by upper-end intermediate width, well-developed, complete peristome; four to seven (most commonly five) apertures per fenestrule. Single intermediate-width, continuous keel along branch midline, forming division between the four rows of autozooecia; large, ovate to elliptical nodes, elongate proximodistally, positioned atop keel. Autozooecial chamber size intermediate; chambers emplaced in four rows, adaxial chamber rows alternating, abaxial rows alternating or adjacent, either five or six rows at sites of branch bifurcation or five or six rows for moderate to pronounced distances proximal to sites of branch bifurcation; outline irregularly ovate near reverse wall, becoming irregularly pentagonal toward mid chamber; rectangular to parallelogram-shaped in mid chamber and throughout most of chamber length; biolbate ovate near obverse surface, enlarged at distal end with in- flection at proximo-adaxial apertural edge; shape and symmetry of adaxial and abaxial autozooecial cham- bers equal. Chamber longest dimension parallel to proximal and distal lateral chamber walls. Aperture at distal-abaxial end of chamber for both adaxial and abaxial rows of autozooecia, connected to chamber by intermediate, highly variable length vestibule. Short superior hemiseptum present at proximal apertural edge, inferior hemiseptum absent. Lateral-wall bud- ding-angle of adaxial two rows of autozooecial cham- bers moderately variable, mean of 17°; lateral budding angle of abaxial two rows of autozooecial chambers moderately variable (mean of 51°); reverse-wall bud- ding-angle of adaxial and abaxial rows of chambers both highly constant (mean approximately 42°). En- larged autozooecial chambers (ovicells?) observed in tangential section, length same as autozooecia, width 1.35 times greater. Table 41 presents statistical criteria used in delimiting this species. Exterior description.—Zoarium robust, expansion flat to slightly obversely curved, fan-shaped; mean mesh spacing lower-end intermediate, varying from close to open; moderate astogenetic thickening of both obverse and reverse lamellar skeleton; zoarial pattern moder- ately to highly irregular. Probable mature widths 30 to 50 mm; lengths 20 to 60 mm. Branches robust; wide, variable in width; straight to slightly irregularly sinuous, lateral branches commonly broadly curved toward edge of zoarium. Branch spac- ing intermediate to more rarely close in some zoarial fragments, distance between adjacent branch centers variable. Obverse surface texture slightly to moder- ately granular, coarsening with astogeny; surface well- rounded, except single intermediate-width, well-de- veloped keel; keel continuous, straight, extending along branch midline and causing moderate to pronounced positive inflection on obverse surface. Keel thickens, becomes partially covered by lamellar skeleton and partially overgrows adaxial edge of middle aperture with astogeny. Single rows of well-developed, large, ovate to elliptical nodes, elongate proximodistally; size and shape of nodes moderately regular; nodes pro- jecting from middle of keel; one to two per fenstrule Text-figure 17.— Fenestralia sanctiludovici illustrated. 1, diagram- matic longitudinal section illustrating changing chamber outline for adaxial rows of chambers from deep section near middle of branch (bottom of figure) to shallow section (top of figure) [Abaxial rows of chambers exhibit same chamber outlines, but require a longitudinal section to be oriented at an angle from perpendicular required for adaxial rows. Observe relatively low reverse-wall budding-angle (ar- row) typical of genera exhibiting more than two rows of chambers across the branch.], x 70; 2, diagrammatic tangential section showing change in chamber outline of adaxial chambers from deep section near reverse-wall budding-site (bottom of figure) to shallow section near obverse surface (top of figure) [Poorly developed superior hemi- septa are illustrated in this figure (arrow).], x 70; 3, diagrammatic transverse section across branch [Observe orientation of adaxial (ar- row a) and abaxial (arrow b) aperture openings relative to plane of obverse surface.], x 70; 4, reconstruction of typical chamber shape (three-dimensional) as viewed from distal end of branch; chamber reconstructed is from the right adaxial side of branch, x140; 5, reconstruction of typical adaxial chamber shape (three-dimensional) as viewed from abaxial edge of branch, x 140; 6, reconstruction of typical adaxial chamber (three-dimensional) as viewed from obverse surface; chamber reconstructed is from right side of branch [Observ e slight inflection into chamber caused by poorly developed superior hemiseptum (arrow).], x 140. ‘Ga Wr. Pweg AES OCOD. DS “EC I OI BE 140 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 length; nodes intermediately, moderately unevenly spaced, frequently occurring at or near sites of branch- dissepiment junction; with astogeny node diameter in- creases and nodes frequently become partially to com- pletely covered by secondary lamellar skeleton of keel. Lower-end intermediate-size stylets, highly variably sized and variably positioned along obverse surface; most commonly positioned between nodes along keel or at abaxial edges of keel, more rarely across branch surface. Reverse surface texture moderately granular, coarsening with astogeny; bearing relatively few rows of intermediately spaced longitudinal striae atop which are positioned rows of upper-end small-size, inter- mediately spaced, variably sized microstylets. Longi- tudinal striae become covered by lamellar skeleton with astogeny and microstylets become larger, more un- evenly positioned across surface. Autozooecia ar- ranged in four rows, except either five or six rows at sites of branch bifurcation or five or six rows for mod- erate to pronounced distances proximal to sites of branch bifurcation; branches with pronounced thick- ening proximal, pronounced thinning distal to sites of branch bifurcation. Dissepiment width intermediate, approximately three-fifths width of branch, width moderately vari- able; length intermediate, highly variable; connect branches at moderately constant intervals. Dissepi- ments with slight medial thinning, flaring at branch— dissepiment contact; moderately recessed from ob- verse surface, approximately even with reverse surface. Moderate to pronounced astogenetic thickening of dis- sepiment. Obverse dissepiment surface with one to two longitudinal ridges emplaced perpendicular to branch length, atop which are positioned lower-end interme- diate-size stylets; ridges become covered by lamellar skeleton, stylets become more variably positioned across obverse surface with astogeny; reverse dissepi- ment surface also with longitudinal ridges atop which are positioned upper-end small microstylets; ridges covered by lamellar skeleton, microstylets more vari- ably positioned across obverse surface with astogeny; obverse dissepiment surface texture slightly to mod- erately granular, reverse surface texture moderately granular, both coarsening with astogeny. Emplacement of dissepiments perpendicular or approaching perpen- dicular to branch length. Abaxial apertures typically project toward and open onto dissepiment at branch- dissepiment contact, frequently highly projecting onto dissepiment, less frequently positioned at proximal or distal edge of dissepiment; typically arranged sym- metrically between branches, less frequently arranged asymmetrically between branches. Fenestrule size large; shape typically irregularly el- liptical to more rarely irregularly ovate, highly elongate proximodistally; moderately variable in size and shape; Table 41.—Summary numerical analysis of Fenestralia sanctilu- dovici Prout, 1858a. For explanation of abbreviations of characters (left column), see Table 8b (foldout inside back cover). number of mea- coeffi- sure- standard cient of observed ments mean deviation variation range 1. WB 24 0.5700 0.1250 21.93 0.414-0.833 2. DBC 24 0.9370 0.2160 23.05 0.500-1.200 3. WD 24 0.3460 0.0860 24.86 0.244-0.560 4. LF 24 1.2600 0.2117 17.22 1.000-1.670 5. WF 24 0.4720 0.1390 29.45 0.280-0.720 6. AF 24 921 0.83 16.16 4-7 7. AL 24 0.1030 0.0094 9.13 0.088-0.113 8. AW 24 0.0810 0.0091 11.23 0.063-0.092 9. ADB 24 0.2640 0.0400 15.15 0.203-0.358 10. AAB 24 0.1970 0.0320 16.24 0.120-0.269 11. ABB 24 0.5810 0.1570 27.02 0.356-0.890 12. DN 24 0.1270 0.0310 24.41 0.080-0.180 14. SNB 24 0.5840 0.1230 21.06 0.380-0.820 15. WK 24 0.0690 0.0164 23.77 0.045-0.106 16. DSO 24 0.0111 0.0029 26.12 0.008-0.017 17. SSO 24 0.0262 0.0081 30.92 0.014-0.042 18. WP 24 0.0423 0.0091 21.51 0.028-0.058 22. RSS 24 0.0174 0.0100 57.47 0.008-0.022 24. SSS 24 0.0462 0.0140 30.30 0.029-0.074 32. TRW 24 0.0098 0.0023 23.46 0.006-0.014 33. TLW 24 0.0088 0.0020 22.72 0.005-0.012 34. FWT 24 0.1133 0.0695 61.34 0.034-0.286 35. RWT 24 0.1718 0.1172 68.22 0.054-0.471 36. CL 24 0.3883 0.0204 2.67 0.370-0.410 37. CD 24 0.1423 0.0120 8.43 0.124-0.162 38. MAW 24 0.1208 0.0090 7.45 0.108-0.140 39. MIW 24 0.0610 0.0119 19.51 0.042-0.082 40. VD 24 0.0815 0.0291 35.71 0.037-0.129 41. RA 24 41.75 DIS 6.55 38-47 42A. LA-1 24 17235 3.45 13.89 12-24 42B. LA-2 24 51.00 6.55 12.85 42-66 43. TB 24 0.6543 0.1196 18.28 0.486-0.870 44. WOT 10 0.1630 0.0187 11.47 0.142-0.177 equal in size and shape on both obverse and reverse surfaces. Mean width of fenestrule slightly less than branch width, ratio approximately 5:6; fenestrule opening moderately decreasing in size toward proximal end of zoarium due to astogenetic thickening of la- mellar skeleton. Width to length ratio of fenestrule ranging from 7:10 to 1:6; moderately variable, mea? ratio of width to length approximately 3:8; length of fenestrule more constant than width. Four to seven (most commonly five) apertures per fenestrule length; distance between closest aperture centers along branch 1.34 times spacing across branch, spacing across fe- nestrule 2.95 times spacing across branch; spacing along and across branch moderately variable, spacing across fenestrule highly variable. Autozooecial aperture size lower-end intermediate, shape symmetrically circular, irregularly circular to ir- regularly ovate, slightly elongate proximodistally of proximoabaxially; width to length ratio approximately MISSISSIPPIAN BRYOZOANS: SNYDER 141 7:9, size moderately uniform and shape variable; ad- axial rows of apertures open parallel to plane of obverse Surface, abaxial rows of apertures opening into fenes- trule perpendicular to plane of obverse surface; upper- end intermediate-width, well-developed, continuous Peristome present. Abaxial rows of aperture margins €xtend into fenestrule, causing slight inflections in fe- Nestrule outline on obverse surface. Centrally thick- ened terminal diaphragms present, commonly occur- nng throughout the zoarium. Zoarial supports develop as extensions of reverse Zoarial surface and lateral edge of zoarium. Interior description.—Branches circular, irregularly Circular, ovate to polygonal in transverse section, slightly to moderately elongate parallel to plane of ob- Verse surface; symmetrical on obverse or reverse sur- face. Branches thick, moderately variable in depth. Autozooecial living chamber size intermediate, chambers arranged in four rows along planar branch axial walls, adaxial rows alternating, abaxial rows al- ternating to adjacent; mid-axial wall straight in mid Chamber and toward obverse surface, extending along Tanch midline dividing adaxial autozooecia which are emplaced in alternating rows, highly sinuous near re- verse wall, dividing adaxial two rows of chambers; abaxial two rows of chamber axial walls straight, acting as reverse walls for abaxial two rows of autozooecia, remaining moderately straight throughout branch depth. Chamber longest direction parallel to proximal and distal lateral chamber walls. Autozooecial cham- er outline irregularly ovate near reverse wall, rapidly “coming irregularly pentagonal toward mid chamber; rectangular to parallelogram-shaped in outline in mid Chamber and throughout most of chamber length; ir- Tegularly bilobate-ovate near obverse surface, enlarged at distal end with inflection into chamber at proximo- adaxial apertural edge; chamber shape highly uniform, Same in both adaxial and abaxial rows of chambers. Perture positioned at distal-abaxial end of chamber, Connected to chamber by intermediate, highly variable oe vestibule. Ratio of autozooecial chamber min- D width to maximum width 1:2; width to depth iue approximately 6:7; depth to length ratio approx- us ately 3:8: maximum width, depth, and length highly stant, minimum width highly variable. Short, poor- y developed superior hemiseptum present at proxi- mal-abaxial edge, inferior hemiseptum absent. Adaxial Ows of autozooecial chambers diverge laterally from mad branch at a moderately variable angle (mean e Proximately 17°); abaxial rows of autozooecial po diverge laterally from middle of branch at Wa E variable angle (mean of 5 19). Although ori- ES of apertures to chamber varies between ad- ànd abaxial rows of chambers, both adaxial and abaxial chamber shapes and dimensions are the same. Autozooecial chambers diverge from respective re- verse walls at a highly constant angle (mean approxi- mately 42°). Heterozooecia (ovicells?) present, evident in tangential section, length same as autozooecia, width 1.35 times maximum chamber width; occurring most commonly toward proximal end of zoarium. Three-dimensionally reconstructed chamber form a slightly rectangular tube; length, viewed from lateral edge for adaxial and approximately 45? from perpen- dicular to obverse surface, substantially greater than depth, viewed from distal end of branch; which in turn is slightly greater than width, viewed from obverse surface. Internal granular skeletal layer thickness interme- diate; granular skeletal layer well-developed, contin- uous with obverse nodes, stylets, keel, and peristome; reverse longitudinal striae and microstylets; across dis- sepiments and in the middle of zoarial supports. Outer lamellar layer thickness intermediate, exhibiting mod- erate astogenetic thickening; covering apertures and keel with astogeny. Remarks.— Named by Prout (18582) for materials found in the St. Louis Group near St. Louis, Missouri and Alton, Illinois. Ulrich (1890) recognized the spe- cies in the Warsaw Beds near Warsaw, Illinois as well as in the St. Louis near St. Louis, Missouri. F. sanctiludovici is readily distinguished by the pres- ence of a distinctive keel along the branch midline, dividing the four rows across the branch into two groups of two rows; inner adaxial rows oriented parallel to obverse surface and outer abaxial rows oriented at moderate angle toward the fenestrule. Lack of a keel in Polypora allows ready separation of F. sanctiludo- vici. Interior view allows delimitation of this species, based on the straight, well-developed mid-axial wall and adaxial two rows of autozooecia, basically iden- tical chamber shape between adaxial and abaxial rows of autozooecia, in conjunction with distinctive lateral- wall budding-angles between adaxial and abaxial au- tozooecia. This species has some similarities to species of Ban- astella, however four rows of autozooecia typically oc- cur across the branch in Fenestralia, whereas typically two rows are found in Banastella. Material studied. — Eighteen exterior fragments, two sectioned specimens; largest zoarial fragment 31 x 44 mm (width to length). Moderately well-preserved due to robust nature of zoarium. Occurrence. — Common in Warsaw Beds at type sec- tion, present in Salem and St. Louis formations throughout study area. Holotype.—1SGS (ISM) 4486-1. Paratype.—ISGS (ISM) 4482-2. 142 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 Genus POLYPORA McCoy, 1844 Flabelliporella Simpson, 1895a (fide Bassler, 1953, p. G125). Polyporella Simpson, 1895a (fide Bassler, 1953, p. G125). Polyporina Frederiks, 1920 (fide Bassler, 1953, p. G125). Type species.—Polypora dendroides McCoy, 1844 [Lower Carboniferous of Ireland]. Typical Warsaw species.—Polypora varsoviensis Prout, 1858a, p. 237 [Warsaw, Illinois]. Diagnosis.—Zoarium robust, mesh spacing varying from close to open; chamber outline variable, ranging from elliptical, rectangular, hexagonal, triangular, ovate, to circular in mid tangential section, chambers in three to five rows diagonally across branch, chamber size intermediate to large; aperture size intermediate to large; superior and inferior hemisepta absent, chamber reverse-wall budding-angle varying between 18° and 77° (means). Three-dimensionally reconstructed chamber form a polygonal or irregular tube. Description.—Zoarium robust, expansion flat, ob- versely or reversely curved to cupped, mesh varying from close to open, regular to irregular. Branches wide, straight to slightly sinuous in trace with lateral branches broadly curved toward edge of zoarium; branch surface rounded, angular to flat. Keel absent. Nodes present in most species, emplacement monoserial, size intermediate to large, shape stellate to ovate, located along middle of branch in straight to anastomosing rows, spacing intermediate to wide. Ob- verse stylets either present or absent, size intermediate to large, occurring in rows along or spaced across ob- verse surface. Microstylets present or absent, size in- termediate to large. Macrostylets present or absent, size large, positioned atop longitudinal striae or at branch- dissepiment junction. Autozooecia typically in three to five rows across branch; five to seven rows at or along branch proximal to sites of branch bifurcation. Heterozooecia (ovicells?) present in some zoarial frag- ments reported by other workers; none observed in Warsaw specimens. Dissepiment width thin to intermediate, length vary- ing from short to long, connecting branches at regular to variable intervals. Fenestrule size intermediate to large, shape highly variable, ranging from ovate, circular, rectangular, par- allelogram-shaped, elliptical, to polygonal. Aperture size intermediate to large, shape ovate, el- liptical, to circular; adaxial row(s) oriented parallel to plane of obverse surface, abaxial rows parallel to plane or at slight angle toward fenestrule. Peristome present, either complete or incomplete; apertural stylets pres- ent, develop as extensions at edge of peristome; ter- minal diaphragms present, located at proximal end or throughout zoarium. Branch shape elliptical, ovate, circular, to polygonal in cross-section, thick in depth. Autozooecial chamber size intermediate to large, chambers arranged in three to five rows along straight to slightly sinuous axial wall; maximum chamber length parallel to proximal and distal lateral chamber walls. Chamber outline ovate, circular, diamond-shaped, to polygonal near reverse wall; elliptical, rectangular, hexagonal, ovate, to circular in mid chamber and throughout most of chamber depth; ovate circular, bi- lobate-ovate to elliptical near obverse surface. Vesti- bule present, length intermediate to long. Superior and inferior hemisepta absent. Adaxial lateral-wall bud- ding-angle 7° to 12° (means); abaxial lateral-wall bud- ding-angle 25° to 47° (means); reverse-wall budding- angles constant within species, highly variable between species, ranging from 18° to 77° (means). Lamellar skel- etal layer thickness intermediate to thick, exhibiting slight to pronounced astogenetic thickening; granular skeletal layer thickness intermediate to thick, exhib- iting no astogenetic thickening. Three-dimensionally reconstructed chamber form a polygonal or irregular tube. Text-figure 18 illustrates zoarial outlines in longi- tudinal, tangential, and transverse orientations, and three-dimensional chamber reconstructions from dis- tal, abaxial edge of branch and obverse surfaces. Remarks.—Polypora was described by McCoy from Lower Carboniferous specimens from Ireland. Lack of medial keel, rows of obverse nodes, and three to seven rows of autozooecia across each branch allow ready recognition. Both adaxial and abaxial chambers, although differ- ing in orientation relative to the branch axis, have essentially the same chamber shape. Reverse-wall bud- ding-angle has a broad range for the genus: within spe- cies, however, this angle is highly constant. Zoarial characters are more varied in Polypora than in other meshwork fenestrates. Warsaw polyporid spe- Text-figure 18.—Polypora varsoviensis illustrated. 1, diagram- matic longitudinal section illustrating changing chamber outline for adaxial rows of chambers from deep section near middle of branch (bottom of figure) to shallow section (top of figure) [Low reverse wall budding-angle (arrow) is typical of most species in this genus.], X 70; 2, diagrammatic tangential section showing changing chamber outlines from deep section near reverse-wall budding-site (botto™ of figure) to shallow section near obverse surface (top of figure) [Adaxial (arrow a) and abaxial (arrow b) chamber outlines are ap” proximately the same in mid tangential section in Polypora.], X 40; 3, diagrammatic transverse section across branch [Observe similar orientation of apertures to plane of obverse surface (arrows).], * 70; 4, reconstruction of typical chamber shape (three-dimensional) as viewed from distal end of branch; chamber reconstructed is from right side of branch, x 70; 5, reconstruction of typical chamber shape (three-dimensional) as viewed from abaxial edge of branch, x 70; 6; reconstruction of typical chamber shape (three-dimensional) as viewed from obverse surface; chamber reconstructed is from right side 0 branch [Observe how length as shown in tangential view (Text-fi£ 18.2) only expresses a small amount of the total chamber length when viewed from the obverse surface.], x 70. MISSISSIPPIAN BRYOZOANS: SNYDER 143 Cies are highly distinctive, but available material does and P. simulatrix. Not justify generic subdivision. Polypora spininodata Species composition.— Five Warsaw species of this and P. varsoviensis are closely allied, as are P. gracilis genus were recognized: P. gracilis, P. varsoviensis, P. 144 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 spininodata, P. simulatrix, and P. retrorsa. Range.— Ordovician to Permian. Polypora gracilis Prout, 1860 Plate 65, figures 1-9, Plate 66, figures 1-4; Table 42 Polypora gracilis Prout, 1860, p. 580. [Warsaw Limestone: Warsaw, Illinois]; Prout, 1866, p. 422, pl. 21., figs. 1, la [Keokuk Limestone: Warsaw, Illinois]; Ulrich, 1888, p. 73 [Waverly Group: Richfield and Sciotoville, Ohio]. Polypora(?) gracilis Prout. Ulrich, 1890, p. 590, pl. 61, figs. 10, 10a [Keokuk Group: Warsaw and Nauvoo, Illinois; Keokuk, Iowa; King’s Mountain, Kentucky]. Polypora cf. gracilis Prout. Sakagami, 1970, p. 689 [Upper Paleozoic: Thailand and Malaya]. Diagnosis.— Zoarium moderately robust, mean mesh spacing upper-end intermediate, varying from inter- mediate to wide, pattern highly irregular; branch ro- bustness intermediate to robust; branches thick in depth; branches wide, straight to slightly sinuous, broadly curved at lateral zoarial edge; transversely cir- cular, irregularly circular, ovate to polygonal, spacing upper-end intermediate to wide; branches joined at fairly regular intervals by lower-end intermediate width, upper-end intermediate to long dissepiments. Fenes- trules large; shape varying from rectangular to paral- lelogram-shaped to elliptical; variable. Autozooecial aperture size upper-end intermediate to lower-end large, shape irregularly ovate to approaching circular, elon- gate proximodistally to proximoabaxially, surrounded by intermediate size, well-developed, complete peri- stome; nine to 15 (most commonly 11 to 12) moder- ately large apertural stylets surround aperture; five to nine (most commonly seven) apertures per fenestrule. Large, irregularly lobed stellate to ovate nodes, elon- gate proximodistally, positioned in single row along branch midline. Autozooecial chamber size upper-end intermediate, emplaced in three or more rarely four alternating rows, except five rows at sites of or for pronounced distances proximal to sites of branch bi- furcation, and two or three rows for short distances distal to sites of branch bifurcation; chamber outline irregularly ovate to polygonal near reverse wall; tri- angular, rounded triangular to rarely irregularly polyg- onal throughout mid and most of chamber length; ir- regularly ovate near obverse surface, enlarged at distal end; chamber shape uniform in all rows across branch. Chamber longest dimension parallel to proximal and distal lateral chamber walls. Aperture positioned at distal to distal-abaxial end of chamber, connected to chamber by intermediate, highly variable length ves- tibule. Superior and inferior hemisepta both absent. Lateral-wall budding-angle of adaxial autozooecial chambers highly variable (mean about 12°); lateral budding angle of abaxial autozooecial chambers vari- able (mean approximately 47°); reverse-wall budding- angle of adaxial and abaxial chambers individually Table 42.—Summary numerical analysis of Polypora gracilis Prout, 1860. For explanation of abbreviations of characters (left column), see Table 8b (foldout inside back cover). number of mea- - sure- standard cient of observed ments mean deviation variation range 1. WB 24 0.5770 0.1660 28.77 0.375-0.900 2. DBC 24 1.3270 0.3496 26.34 0.875-1.875 3. WD 24 0.3000 0.0633 21.10 0.205-0.431 4. LF 24 2.3030 0.4646 20.17 1.750-3.380 5. WF 24 0.7823 0.2960 37.84 0.450-1.380 6. AF 24 7217 0.94 13.08 5-9 7. AL 24 0.1543 0.0116 7.52 0.134-0.177 8. AW 24 0.1117 . 0.0095 8.51 0.095-0.129 9. ADB 24 0.4004 0.0423 10.56 0.323-0.475 10. AAB 24 0.2463 0.0205 8.32 0.219-0.294 11. ABB 24 0.8284 0.2695 32.53 0.450-1.330 12. DN 24 0.1976 0.0292 14.78 0.138-0.250 14. SNB 24 1.4990 0.5200 34.69 0.975-2.800 16. DSO 24 0.0147 0.0042 28.57 0.009-0.022 17. SSO 24 0.0623 0.0411 65.97 0.020-0.142 18. WP 24 0.0286 0.0061 21.33 0.018-0.039 19. SA 24 11.58 1.68 14.47 9-15 20. SAD 24 0.0360 0.0052 14.44 0.029-0.046 22. RSS 24 0.0330 0.0119 36.06 0.014-0.052 24. SSS 24 0.0528 0.0178 33.71 0.021-0.086 32. TRW 24 0.0103 0.0018 17.48 0.008-0.013 33. TLW 24 0.0155 0.0032 20.65 0.001-0.021 34. FWT 24 0.1108 0.0501 45.21 0.036-0.214 35. RWT 24 0.0786 0.0382 48.60 0.020-0.143 36. CL 24 0.3789 0.0161 4.25 0.354-0.402 37. CD 24 0.2129 0.0183 8.60 0.188-0.252 38. MAW 24 0.2060 0.0310 15.05 0.164-0.260 40. VD 24 0.1017 0.0298 29.30 0.057-0.165 41. RA 24 53.92 7.66 14.20 42-64 42A. LA-1 24 12:35 5.93 48.09 2-22 42B. LA-2 24 47.42 12:19 23.36 36-60 43. TB 24 0.5044 0.0985 19.53 0.374-0.714 uniform, each exhibiting a slightly variable angle (mean approximately 54°). Table 42 presents statistical cri- teria used in delimiting this species. Exterior description.—Zoarium moderately robust, expansion flat to slightly obversely curved, fan-shaped; mesh spacing intermediate to open, mean spacing up- per-end intermediate; intermediate astogenetic thick- ening of both obverse and reverse lamellar skeleton; zoarial pattern moderately irregular. Probable mature widths 15 to 30 mm; lengths 20 to 40 mm. Branch robustness intermediate to robust; branches wide, highly variable in width; straight to slightly sin- uous, curving toward sites of dissepiment insertion, lateral branches broadly curved toward edge of zoar- ium. Branch spacing upper-end intermediate to wide; distance between adjacent branch centers moderately irregular. Obverse surface texture smooth, exhibiting slight granular coarsening with astogeny; surface flat to slightly rounded, less frequently angular. Single row of well-developed, large irregularly lobed stellate 10 MISSISSIPPIAN BRYOZOANS: SNYDER 145 Ovate nodes, elongate proximodistally; node size reg- ular, shape moderately regular; nodes projecting from middle of branch in straight single row; one to two nodes per fenestrule length; widely, unevenly spaced, frequently located at or near site of branch-dissepi- Ment junction; node diameter slightly increases and nodes frequently become partially covered by thick- ened secondary lamellar skeleton during astogeny. Rows of intermediate-size stylets, variable in size and highly variably positioned, anastomosing around apertures along obverse branch surface, giving a coarsely gran- ular appearance to surface at low magnifications; sty- lets Increasing in size and number with astogeny. Re- Verse surface texture granular, coarsening with astogeny; bearing an intermediate number of intermediately Spaced longitudinal striae which persist throughout as- togenetic thickening of lamellar skeleton; microstylets large, shape irregularly polygonal to circular, highly Variable in both size and shape, microstylets posi- toned atop longitudinal striae, irregularly spaced, in- creasing in size with astogeny. Autozooecia typically arranged in four rows diagonally across branch, except as many as five rows at sites of or for pronounced distances proximal to sites of branch bifurcation and as few as two or three rows for short distances im- Mediately distal to sites of branch bifurcation; branch- es exhibit pronounced thickening proximal, pro- nounced thinning distal to sites of branch bifurcation. eterozooecia absent in all zoarial fragments analyzed. Dissepiment width lower-end intermediate, slightly Steater than one-half branch width, width moderately Variable; length upper-end intermediate to long, highly Variable; connect branches at fairly regular intervals. br, piments barlike, exhibiting slight flaring at „.ch-dissepiment contact; highly recessed from ob- a Tecessed from reverse branch surface. Slight as- genetic thickening of dissepiment. Obverse dissepi- a Surface with two to four longitudinal ridges is Placed perpendicular to branch length across dis- “Piment surface, rows of intermediate-size stylets atop ati ridges become partially covered by lamellar 8); ? = questionable occurrence due to preservation; — = not present. (6) Hamilton- Warsaw Roadcut, Illinois (1) Bentonsport, Iowa (2) Iowa Terminal, Iowa (3) Keokuk Industrial, Iowa (4) White Hollow, Iowa (5) Grays Quarry, Illinois (7) Geode Glen, Illinois (8) Soap Factory Hollow, Illinois (9) Buel Branch, Illinois (23) Dennis Hollow, ( Valmeyer), Illinois (15) Little Whitaker Creek, Illinois (22) Columbia Roadcut, Illinois (10) Sand Branch, Illinois (11) La Grange, Missouri (12) Mount Sterling, Illinois (13) McKee Creek, Illinois (14) Versailles West, Illinois (16) White Hall-C, Illinois (17) White Hall-D, Illinois (18) White Hall-F, Illinois (19) Otter Branch, Illinois (20) Troy Roadcut, Missouri (21) Cragwold Road, Missouri . Banastella limitaris . Apertostella venusta . Archimedes negligens 15. Banastella biseriata . Archimedes owenanus . Fenestralia sanctiludovici . Archimedes wortheni . Apertostella crassata . Polypora spininodata . Hemitrypa aspera 3. Rectifenestella multispinosa 4. Laxifenestella coniunctistyla 6. Laxifenestella serratula . Cubifenestella globodensata . Hemitrypa perstriata . Hemitrypa hemitrypa . Hemitrypa vermifera 1. Rectifenestella tenax 5. Laxifenestella maculasimilis = 9. Minilya paratriserialis = . Banastella mediocreforma = 17. Cubifenestella rudis = . Apertostella foramenmajor € . Banastella cingulata -— 16. Banastella delicata 3 18. Cubifenestella usitata = . Polypora simulatrix = . Polypora varsoviensis = . Polypora retrorsa er 2. Rectifenestella tenuissima SS e eec Reus 11. Banastella guensburgi See ae . Polypora gracilis Se e crar o ee 8. Minilya sivonella mel une er . Archimedes valmeyeri tel ex Wen. en. eed cn . Exfenestella exigua px uet cei au n qon 7. Laxifenestella fluctuata M Mr . Hemitrypa aprilae rcu e cd EA A dm MALE | IARIı MA SCA O Mole dolo | | IPNn»>NAR LOOGA > aa 1 pr ap > TOF FOO I | po d WOO PRA ¡DOM Sale ie IO E Oo | MOTO GA ae ar MO DAD | Laos LOGO Onn A000 G7 © | LAQNI|ALAARO! | Ww | | APR | | Wont OPA an: OO OG Op OO OI E mme rar O03 G E00 | moto: Com i IROCO POOF OF OOP! Orr AO ©) dqeaeeso TO | | mr EM | BA T | |. | | E A: | | I | | | beet | | | | | | ¡LALA! 119.0 GO II SOON II SO FAR III Cre m-I P] | | a Li LQOQAO> APRO | PO | EA Oo EO | Ac Ag! b 1l | E NDA Urs AI DOLO NES IO O ESQ. lO b. TARA ALA LO ELO M CELO AN 2 pw oO ec me Para: [Coco eio oro aI CANO OO Oil | Ww D eu 2 OG. OG: tO IO. PRAT Far e IPIRNARRP-NIPARRIRANN ai | DEOKFAZARR | al | | | ^n | CADA AAN a RI S wl FAO Re OTRON | ¡LALA ERICO I) NOOO ASCO ROO Tore wm awe O ADA Der p exp AMO A I A E. | | | | | | | | | | | | | | | | | | | IY eier LOR | | AR | [OHO oy] | | | | | | | | | | | OOOO: OOOO AP 2 O07 OOo] ANAAFFFAAFAANF 1 FAAFAINNSFANNFAO | [og woelimewwicNOGQORGRG A O | | | | | | | | | | lypora simulatrix. Certain of the remaining 17 species were present throughout individual measured sections, but were restricted geographically along a north-south trend; changing composition for these 17 species is shown in Text-figure 20. The depositional sequence present at the Keokuk- Warsaw contact is that of a carbonate shelf (the Keo- kuk) overlain by calcareous and argillaceous shales (the Warsaw). Sediment source for these sediments is prob- ably from the east-northeast (Atherton and Palmer 1979) and the northwest (see pp. 10, 11 for details). Similar facies relationships, faunal succession, and tro- phic structuring observed throughout the Warsaw sug gest that depositional environments were probably broadly comparable. Changes in the lower Warsaw fau- na probably reflect evolution rather than shifts in en“ vironment. Unfortunately, because of little resistance to weath- MISSISSIPPIAN BRYOZOANS: SNYDER ering, the upper Warsaw frequently is poorly exposed, limiting the possibilities for detailed biostratigraphic analysis. Further work with underlying (Keokuk) and Overlying (Salem, Sonora, Spergen, and St. Louis) units 159 is required to establish definitively whether geograph- ically changing composition of Warsaw species assem- blages is biostratigraphically (evolutionarily) or envi- ronmentally (ecologically) controlled. Based on the 2 = Ina “>| = id PA "m~ H - H 5 = ^ Q » H "y ^ Q9 2 © y E am can RE g o O a e a = wp E. m m O e tt Weg qnas am i a p TOL cda ta? e pd. PEE CNRC ION ONT ^U nn KH [0] Ba RA A RS ofr eem ES a A Asa HEETE O at oie ae o O “Hd HB a DO U FH UVA AHA BOM MS OS ESTR LG SEO VOL VEHTHT ad [5] Osu H OD mudo dgsotnst-dG:'sgcosgitusg'cgru a Qo mc ou SWL En DO = O O e ib debe a B E cà rà ov H O eeke Refn [e] a oO disse Myo Uc 000 tH ERES pg 2 Seiser Dor UU CU SO O ed, 60s £i ES. O doo 8 26 DMMP HHH bP oO dm GE oonu aan ro oO on e aa a OO Bar pe DER E MES yp ee ES O OS 5968324 D O / OS ASS AS TODAS S Banastella limitaris — 9-90 99090 Apertostella venusta —.”o.“. 2 Archimedes negligens eee 2@ er 77 Banastella biseriata —8 960 9 990 e Archimedes owenanus 0009000930 800 Fenestralia sanctiludovici o — 040 Archimedes wortheni 04400 Apertostella crassata e—0000 0990 00 — 09090 Polypora retrorsa eee — Zu] Neetirenestella tenuissima Banastella guensburgi Polypora gracilis Minilya sivonella Archimedes valmeyeri Exfenestella exigua Laxifenestella fluctuata Hemitrypa aprilae 4 Text-figure 20. — Changing species composition of localities in the Warsaw study area. 160 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 general trend of infilling of the Illinois Basin from north to south, which would indicate the boundary between the Keokuk and Warsaw is not time equivalent throughout the basin, it appears evolutionary control is the most probable explanation. TROPHIC STRUCTURE IN SUSPENSION-FEEDING COMMUNITIES INTRODUCTION Polypide shape in modern bryozoans is closely re- flected by chamber skeletal shape (Winston, 1977). Chamber skeletal shape in fossil bryozoans is therefore assumed to reflect ancient polypide shape. Further, many modern bryozoans and the Warsaw fenestrates have limited intraspecific chamber variability, but a broad range of interspecific chamber variation. Studies of modern Bryozoa (Winston, 1977, 1982; Strath- mann, 1973; Bullivant, 1968b) indicate niche differ- entiation as the most probable cause of such intraspe- cific consistency and interspecific variability. Using criteria derived from studies of modern chei- lostome Bryozoa, analagous in many respects to mesh- work fenestrates, patterns of niche differentiation re- flected by variation in zooecial size and species diversity are proposed for Warsaw fenestrates. The basis for concepts of trophic structuring in seemingly similar recent communities and implications for recognition of niche differentiation in fossil assemblages will be established in the following section. Hutchinson (1959), Turpaeva (1957), and Schoener (1974), among others, observed that organisms inhab- iting a single environment tend to use different food resources. Nevertheless, within suspension-feeding communities, the general consensus (Knight-Jones and Moyse, 1961) was that no need exists for trophic spe- cialization because suitable and abundant food is avail- able. Levinton (1972) suggested that species would not exploit the same food resources and thus would not complete; consequently trophic structuring within communities does not develop. Winston (1977, p. 263) presented a strong argument for trophic structuring, stating that “While food may not be a limiting factor in most marine habitats, it is true that at least partial separation of the trophic re- sources does exist among suspension feeders in the same community.” Basing these conclusions on her own extensive work with modern bryozoan species and on previous work concerning niche partitioning by Mullin (1963) and Edmondson (1965), Winston ob- served that species share overlapping but observably separate food resources, and thus exhibit trophic par- titioning. Marischal (1965) and Dales (1957) reported feeding preferences for bryozoans and polychaetes; Winston’s conclusions are similar to those reached by these earlier workers. Three means by which bryozoans might achieve some degree of trophic separation are through selection based on physical, chemical, or biological factors (Winston, 1977), all primarily concerned with either food char- acteristics or feeding behavior. NICHE DIFFERENTIATION AMONG LIVING AND FOSSIL SPECIES The concept that within a community each niche is occupied by a single species (competitive exclusion per Hardin, 1960) has met with recent opposition. Wiens (1977) suggested competition among species is inter- mittent to rare and, subsequently, gave minimal im- portance to competition in natural selection. Wiens argued that fluctuating environments are primary caus- es of change in populations during periods of stress, with little competitive interaction during times of plen- ty, as populations during these periods are below the environmental carrying capacity. Smith (1981) found competition to be detectable only during periods of stress; however, these environmental periods are in- terpreted to be quite frequent. Connell (1975), based on work with the marine intertidal and terrestrial pond and plant communities, argued for predation as the primary interspecific interaction. However, when pop- ulation levels become adequately high, competition for food resources becomes more significant than preda- tion. Lesser levels of predator activity in Paleozoic than Holocene settings (Meyer and Macurda, 1977; Ver- meij, 1977) could lead also to competition as a major factor in communities not thinned by predators. Diamond (1978) argued for competition as a major aspect of natural selection, using modern birds in his study. Schoener (1982, p. 594), based on a synthesis of many authors as well as on original research, con- cluded that “Competition must still be considered of major ecological importance.” The effects of predation and variable environments were also acknowledged by Schoener as affecting natural selection. Niche differentiation and the constraints governing such differentiation are frequently difficult to recognize among living organisms. In fossils this difficulty in- creases appreciably as one must rely on skeletal fea- tures. One advantage in working with fossils is the dimension of time, which allows observation of pos- sible progressive niche differentiation as species evolve within a community. Although application of niche theory to ancient communities is difficult conceptually and in many respects limited, it is appropriate and necessary if a thorough understanding of these com- munities, their structure, function, and the way ancient communities relate to their modern counterparts is tO be established (Ausich, 1980). Competition is herein considered the major factor leading to niche differentiation within Warsaw mesh- MISSISSIPPIAN BRYOZOANS: SNYDER 161 work fenestrates; predation and variability of environ- ment are considered to have played a minor role rel- ative to competition. BRYOZOAN FEEDING MECHANISM AND BEHAVIOR The lophophore is a food gathering organ consisting of a circle of varying numbers of tentacles. Tentacles are hollow protruberances containing a coelomic lu- men continuous with a ring coelom in the lophophore base (Hyman, 1959). They attached to a basal ridge at the outer edge of the mouth and, unlike the brachio- Pods, the lophophore is extended from the skeleton for feeding. When extended, the tentacles expand into a broad, open funnel; when contracted, the tentacles form a tight bundle inside the zooecium (Winston, 1977; also see Text-figs. 21, 22). Retraction of the lophophore occurs when the re- tractor muscles, attached to the cardia, and funicular Muscles contract while the atrial dilators are relaxed (Boardman, 1975; Neilsen and Pedersen, 1979). Once the tentacle sheath encloses the entire lophophore, the atrial sphincter contracts. Retraction of the tentacles 1$ a rapid process typically, whereas protrusion occurs direction of feeding current E $ ]— lophophore \ de e eae mouth tentacle ——/ sheath longitudinal muscle 4 -—— dilator muscle caecum retractor muscle attached to cardia || L.S DAE. nad retractor es en TEE | muscle ; $ H— testes | | | funicular muscle N eet muscle H— entosaccal n coelom | L Sn IN E IN a t figure 21.—Modern stenolaemate showing zooid with ten- Us es extended. Observe direction of current flow across tentacles, Aracteristic of all members of the Bryozoa. (adapted from Board- man, 1975: Winston, 1977; Nielsen, 1970) u exosaccal cavity much more slowly (Boardman, 1975). For protrusion, the retractor and all other muscles first relax, then an- nular muscles of the membranous sac contract se- quentially, proximally to distally in the zooid, thus forcing out the polypide (Nielsen and Pedersen, 1979). Hydrostatic pressure of coelomic fluid increases prox- imally as the atrium contracts, forcing fluid in the coe- lomic lumen in this direction (Boardman, 1975). Inner and lateral tentacle surfaces of the lophophore are covered with fine cilia; the lateral cilia move in such a way that metachronal waves move up the left side and down the right side of each tentacle (Winston, 1977). Reversals of ciliary action can occur (Bullivant, 1968a; Strathmann, 1973), and cilia at one point may stop beating without affecting other cilia along the ten- tacle. Median cilia apparently lack mobility; however, they and specific lateral cilia may act as sensory or- ganelles (Hyman, 1959; Bullivant, 1968a). Gordon (1974) observed elongate solitary and short tufts ofcilia on the abfrontal tentacle surface which act apparently as sensory organelles. When stimulated, these cilia probably initiate retraction or flick of tentacles, or re- verse ciliary motion (Lutaud, 1955, 1973; Bullivant, 1968a; Gordon, 1974). Two mechanisms of feeding have been suggested for bryozoans and other lophophorates. The first of these, proposed by Bullivant (19682), is termed impingement feeding. Outward beating of the lateral cilia causes wa- ter to flow inward through the aboral side of the ten- atrium dilator muscle | tentacle sheath longitudinal muscle membranous sac ganglion retractor — muscle —— zooid wall retractor muscle attached to cardia || annular muscle | caecum —+4 || entosaccal coelom | ! n funicular da Kai exosaccal cavity 1| Text-figure 22.— Modern stenolaemate showing zooid with ten- tacles retracted. Observe how zooid almost completely fills chamber when in the retracted position. (after Boardman, 1975; Winston, 1977; Nielsen, 1970) 162 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 tacular funnel. Water carrying food particles is directed into the mouth, which lies in the middle of the ten- tacles. Upon reaching the mouth, the current of water is deflected upward and outward between the tentacles, and food particles are deposited in the mouth. The latter is accomplished, as suggested by Bullivant, by eddying of the current immediately over the mouth due to sharp inflection of the current at the mouth’s outer edge. Carrying capacity of the current is thus reduced and food accumulates in the still water over the mouth. From here, the food is sucked into the digestive tract by muscular dilation of the pharynx. Although in general agreement with Bullivant’s model, Winston (1977) modified it, reporting that rather than forcing water to flow into the tentacular funnel, the lateral cilia cause current movement up the left side and down the right side of each tentacle. A second feeding mechanism was presented by Strathmann (1971, 1973), who suggested the impinge- ment model could not work because of the similar density between food particles and that of water. In this second model, brief reversals of the cilia were thought by Strathmann to bounce food particles into the mouth because of the presence of strongest current in the center of the lophophore. Neither model has yet been proven. Length and number of tentacles should cause a pro- nounced effect on efficiency of feeding in bryozoans, as more and longer tentacles should increase volume of food brought to the mouth, yet only recently has tentacle number been considered in studies on Bryo- zoa. Use of tentacle number as an important taxonom- ic character was proposed by Waters (1904), but ig- nored by most subsequent workers (per Winston, 1977). Attempts have been made to attach tentacle number and length to depth of occurrence (Braem, 1940; Bul- livant, 1968a), but conclusions lack broad application. Hyman (1959) found tentacle number to vary both within and between species, ranging from eight to 34. Winston (1977, p. 242), in over 200 cyclostome, cteno- stome, and cheilostome species determined “1) range of variation in each of the orders and in selected fam- ilies, genera, and species, and 2) whether tentacle num- ber can be related to morphological or ecological pa- rameters." Winston recognized five groups based on growth form and taxonomy: (1) cyclostomes contain- ing eight to 16 tentacles [31 species examined]; (2) stoloniferous ctenostomes containing predominantly eight to 10 tentacles with a few species having up to 25 tentacles per polypide [29 species examined]; (3) carnose ctenostomes containing eight to 35 tentacles per polypide [39 species examined]; (4) amascan chei- lostomes, with a bimodal distribution of tentacles with peaks between 11 and 16 and between 20 and 28 ten- tacles per polypide [60 species examined]; and (5) as- cophoran cheilostome species containing predomi- nantly 11 to 19 tentacles per polypide, with few species having 20 to 28 tentacles per polypide [53 species ex- amined]. In general, groupings possessing the greatest zoarial regularity in pattern (carnose ctenostomes and both amascan and ascophoran cheilostomes) show the greatest variation in tentacle count. Bullivant (1968b) and Winston (1976, 1977) deter- mined food passage rates (i.e., from mouth to anus) depend on animal condition, food quality and con- centration, and species differences, ranging from a min- imum of 21 minutes in Bugula turrita to a maximum of 60 minutes of Zoobotryon verticillatum. Consistent differences between species and orders were also ob- served by Winston. She observed that non-nutritive particles pass through the bryozoan digestive system more rapidly than food particles. Food Particle Size Although based on somewhat limited data, physical size of food particles is the primary means by which niche differentiation in modern bryozoans is thought to occur (Parsons and Le Brasseur, 1970; Winston, 1977). Size of modern phytoplankton particles ranges generally from 1 to 120 microns (Dussart, 1964; Shel- don, Sutcliffe, and Prakash, 1973). Sheldon empha- sized the pronounced size and volume differences be- tween a bacterium at 1 um and a diatom or protozoan at 100 um, observing variation of two orders of mag- nitude in diameter and six orders of magnitude in vol- ume. Such differences would seem to allow niche dif- ferentiation. A relationship between mouth and food particle size was observed in a study of modern bryozoans by Win- ston (1977). In this study, Winston also illustrated the apparent correlation of phytoplankton abundance with bryozoan mouth diameters. Although certain types of algae were found to be selected preferentially by dif- ferent species of bryozoan, the primary differentiation of trophic resources is based apparently on food par- ticle size. Because mouth dimensions in modern chei- lostome species equal approximately the maximum diameter food particle which an individual zooecium can assimilate (Winston, 1977), mouth dimension is considered critical in determining niche differentia- tion. Winston (1977) suggested a shallow-water, tropical marine environment (such as that of the Warsaw) pro- vided the greatest potential for pronounced differen- tiation of food resources. According to her, this dif- ferentiation should be represented by variation in tentacle number, lophophore diameter, mouth diam- eter, and apertural and zooecial characters. MISSISSIPPIAN BRYOZOANS: SNYDER 163 Morphological Features Governing Feeding Rates in Modern Bryozoan Species Winston (1977), in a study of shallow water marine bryozoans from Woods Hole, Massachusetts, com- Pared ten species in terms of tentacle number, tentacle length, lophophore diameter, length of zooecium, width of Zooecium, length of orifice (aperture), width of or- ifice (aperture), diameter of mouth, and size of fecal Pellet. Moderate to pronounced variation of the above features is observed between species: tentacle numbers range from eight to 30, tentacle length from 0.2 to 1.0 mm, expanded lophophore diameters from 0.2 to 1.4 mm, and mouth diameters from 0.019 to 0.009 mm. In contrast, Winston observed pronounced regularity of these features within species. Clearance rate, defined as the rate at which a sus- Pension feeder clears a suspension, can be studied by Placing colonies in containers with fixed amounts of Suspended algae. Bullivant (1968b) observed clearance Tates of between 0.152 and 1.050 ml/zooid/hr in dif- ferent species of Zoobotryon Ehrenberg, 1831. An at- tempt to measure clearance rate indirectly was pre- sented by Strathmann (1973). He proposed (for fluid flowing at a velocity of 1 cm/sec) that clearance rate 1S equal to the product of the tentacle length times the tentacle number times 1.4 ml/hr/cm. His theoretical Tesults equate well with those observed by Bullivant 1n living Zoobotryon colonies (Winston, 1977). This formula indirectly provides a tool for the analysis of fossils. Polypide dimensions were calculated by Winston (1977) to determine theoretical maximum clearance Tate using Strathmann's (1973) formula. Difference in Clearance rate for species with smallest number and length and those with largest number and length of tentacles is between 0.21 ml/hr/zooid (Crisia eburnea Lamouroux, 1812) and 3.78 to 4.20 ml/hr/zooid (Flus- trellidra hispida Fabricius, 1780), a difference in rate Approaching 20 times. Winston demonstrated that the larger the number and greater the length of tentacles, the more efficient the feeding cone developed. Winston observed substantially greater polypide siz- es associated with species having greatest clearance rates. Increased size of both mouth and polypide is associated with increased tentacle number, length, and Sreater lophophore diameter, suggesting food special- ation, Warsaw ENVIRONMENTAL AND PALEOECOLOGICAL SETTING The abundant fenestrate-dominated assemblages in le Warsaw provide an opportunity to evaluate pos- Sible niche differentiation in a Paleozoic shallow-water marine community. Sequential stages of faunal suc- cession have been recognized (Snyder, 1987) which indicate both physical and biological factors contrib- uted to Warsaw community development. Facies interrelationships and thus broad deposition- al environments appear comparable throughout the sample area (see pp. 11-14) for both the Warsaw and underlying Keokuk Formations. Fenestrate species within Warsaw communities change between the northernmost and southernmost ends of the sample area (see p. 156). Such changes can result from evolutionary or environmental variability; however, causes for these differences are beyond the scope of this study. Warsaw communities and their trophic structuring, however, will be dealt with in terms of species confined to the northernmost area, species confined to the southernmost area, species occurring throughout the area, and all three combined. Both northern and southern communities developed in sim- llar facies and thus in similar inferred depositional environments, with community development follow- ing highly similar stages of succession. Materials and Approach. — Data employed for eval- uating Warsaw niche differentiation are derived from the section on taxonomy (pp. 40-156). Such data sets not only establish a sound base for taxonomy but also provide the opportunity for paleoecologic studies such as that of possible trophic structuring in the meshwork fenestrates. Table 47 lists species employed in the trophic anal- ysis of Warsaw Bryozoa, assigning a number to each for future identification and records area(s) of occur- rence (such as north, south, or throughout) in the area. The following nine characters are used in determining meshwork fenestrate niche assignment: (1) zooecial length; (2) zooecial depth; (3) maximum zooecial width; (4) aperture length; (5) aperture width; (6) aperture spacing along branch; (7) aperture spacing across branch; (8) aperture spacing between branches; and (9) number of apertural stylets. The arithmetic mean of these measurements, using 24 measurements of each character per species, was used. Table 49 lists the char- acter dimensions from species analyzed. ZOARIAL EMPLACEMENT AND FEEDING IN WARSAW MESHWORK FENESTRATES In the Warsaw, zoarial emplacement and mecha- nisms of feeding are assumed to be the same as those observed in modern species; analagous features as well as those specific to fossils themselves are considered as follows: A. Colony positioning within the environment. 1. Colony growth was perpendicular or at a slight angle from perpendicular to the substrate, ex- tending the zoarium upward into the water col- 164 Table 49.—Fenestrate characters used in niche differentiation. Explanations of species numbers are shown in Table 47. PALAEONTOGRAPHICA AMERICANA, NUMBER 57 Le Deo al eax 0.1 x closest aperture lophoph. aper. mini- diam- aper- aper- aper- loph. space= mum= eter= ture ture ture dia. = interp. interp. interp. mean mean mean aper- aper- spacing spacing spacing tentacle interp. lopho- diameter diameter (Ixdxw) zooecial zooecial zooecial ture ture along across between number tentacle phore of of zooecial length depth width length width branch branch branches (stylet length diameter mouth mouth volume (mm) (mm) (mm) (mm) (mm) (mm) (mm) (mm) number) (mm) (mm) (mm) (mm) (mm?) 1. 0.184 0.100 0.104 0.064 — 0.231 0.282 0.301 6.42 0.347 0.347 0.026 0.035 0.0019 25. Uis 0105. 20.L06 0.101. 0.090... 0230. 0230 — “0,297 4553091501345 0.345 0036 0,055) 92: 010024 A. 0.261 0.151 0.146 0.117 0.096 0.234 0.225 0.214 = 0.338 0.338 0.039 0.034 0.0058 4 0263 OcE71 0.148 0.104 — 0.300 0.289 0.378 — 0.434 0.434 0.042 0.043 0.0067 >. '0.230 0.154 0.140 0.076 — 0:255 0.301 0.257, = 0.383 0.383 0.030 0.038 0.0050 622 0.219 0.139 0.143 0.100 0.084 0.235 0.242 0.249 = (95553 0.353 0.034 0.035 0.0044 Teu 0,281 0.147 0.162 0.091 0.074 0.262 0.295 0.399 = 0.393 0.393 0.030 0.039 0.0067 8.: 0.269 0.158 0.139 0.106 — 0.394 0.370 0.391 10.42* 0.569 0.569 0.042 0.057 0.0081 O... 0.210 0.152 0:127 0.071 — 0:227 0312 0.321 2.00 0.341 0.341 0.028 0.034 0.0041 IU 0757 0.140 0.138 0.089 — 0.239 0.301 0.296 9.00 0.359 0.359 0.036 0.036 0.0055 0580" 9,204. 70 I74^ 0196 — 065^ 0/437. (;419. 0.452 18.29 0.629 0.629 0.066 0.063 0.0230 12. 0.489 212 0.148 0.170 0.148 0.314 0.276 0.323 21.08 0.414 0.414 0.059 0.041 0.0153 BAS 90.2300 0208.2 02724. 30.1753 (0383-0376 0.441 12.96 0.564 0.564 0.068 0.056 0.0267 14. 0.692 0.195 0.206 0.204 0.162 0.398 0.365 0.491 20:25 0.548 0.548 0.065 0.055 0.0278 13. 9329 0.210 0.160 0.161 0.134 0.324 0.292 0.387 = 0.438 0.438 0.054 0.044 0.0111 16. 0.639 0.170 0.154 0.198 0.158 0.436 0.347 0.581 15.21 0.521 0.521 0.063 0.052 0.0167 17.02 0.270 0.187 0.176 0.144 0.306 0.326 0.439 — 0.459 0.459 0.058 0.046 0.0142 18. 0.245 0.183 0.145 0.143 0.104 0272 0.262 0.418 8.58 0.393 0.393 0.042 0.039 0.0065 19... 0.213 0.155 0.129 0.084 0.067 0.280 0.295 0.583 16.28 0.420 0.420 0.027 0.042 0.0043 20 0.198 0 159 - 01354 0.123 0072 0248 0.239 0298 0.357 0.357 0.029 0.036 0.0042 21. 20202 0.177 0.136 0.140 0.096 0.216 0,222 0.297 — 0.324 0.324 0.038 0.032 0.0049 22. 0.356 0.174 0.164 0.128 0.075 0.296 0:715 0.478 — 0,323 0523 0.030 0.032 0.0102 Oe 709 20.225 0091332 0.1322 7:0.0922220124070N0232: 0322 — 0.348 0.348 0.037 0.035 0.0069 24. 0.224 0.219 0.163 0.122 0.088 0.222 0232 0.293 — (0/333 0.333 0.035 0.033 0.0080 25. 0.224 0:177 0.160 0.124 0.085 0.244 0.236 0954 _ 0.354 0.354 0.034 0.035 0.0063 25.. 0.238 0162. .0.4334 0:30... 0.088 20.240. 7.0253. 0:207 — 0.360 0.360 0.035 0.036 0.0051 24. 092 0.215 0.167 0.166 0.114 0.283 0.280 0.308 — 0.420 0.420 0.046 0.042 0.0105 28. 0.209 0175 0.125 0.111 0.094 0.198 0.189 0.243 — 0.284 0.284 0.038 0.028 0.0033 29, 0:220 0:122 0.113 0.106 0.084 0:223 0.203 0.268 20.58 0.305 0.305 0.034 0.031 0.0030 W Cl 0.128 0.115 0.102 0.084 0.191 0.188 0.213 10.50 0.282 0.282 0.034 0.028 0.0026 21 -0.229 0.138 0.119 0.111 0.087 0.220 0.241 0.269 11:50 0.330 0.330 0.035 0.033 0.0038 32. 0.388 0.142 0.121 0.103 0.081 0.264 0.197 0.581 — 0.296 0.296 0.032 0.030 0.0067 SO 35/9 0213 0.206 0.154 0.112 0.400 0.246 0.829 11,98 0.369 0.369 0.045 0.037 0.0166 34. 0.779 0.140 0.174 0.198 0.168 0.376 0.274 0.516 20.67 0.411 0.411 0.067 0.041 0.0190 35. 0:536 0.198 0.189 0.220 0.164 0:377 0.291 0.479 12.67 0.437 0.437 0.066 0.044 0.0201 36: 0.791 0.167 0.170 0.248 0.174 0.549 0.351 0.776 30.50 0/327. 0927 0.070 0.053 0.0225 37. 0695 0.336 0.128 0.135 0:125 0.233 0.190 0.366 Tf gis, 0.285 0.285 0.050 0.029 0.0299 * In Minilya sivonella, there are also two large stylets per aperture. ently resulted in colony dislocation. umn. Upright orientations are observed in nu- merous zoaria preserved in situ. . Inferred dominant colony orientation extended perpendicular (across colony width) to primary current direction, thus allowing the entire col- ony equal feeding opportunity. Colonies formed straight, anastomosing, obversely or reversely curved or cupped expansions. . Obverse colony surface was typically oriented down-current (away from direction of primary current), inferred from the significantly greater occurrence of preserved zoaria with obverse surface facing downward onto bed surfaces in areas where a single depositional event appar- . Colony height above the sea floor was varied, ranging in mature colonies from tens of mm to in excess of 1 m in some species, with most common development from 2 to 20 cm in height. . Colony spacing across the sea floor appears tO minimize sheltering of colonies behind one an- other relative to current direction, as observed on Warsaw slab surfaces. B. Polypide feeding characteristics. 1. Lophophores are considered to be symmetrical cones, opening upward (Winston, 1977). 2. The lophophore gathers food selectively through combined tentacle and cilia activity (Bullivant, 1968a; Strathmann, 1971, 1973) MISSISSIPPIAN BRYOZOANS: SNYDER 165 PARAMETERS USED FOR DETERMINING NICHE DIFFERENTIATION IN WARSAW FENESTRATES In modifying Winston’s (1977) work to apply to Pa- leozoic fenestrates, autozooecial chamber dimensions are treated as being equal approximately to those of the polypide, as is the case in many modern bryozoan Species (Winston, 1977, 1982). Length and width of the aperture can be determined in both living bryo- Zoans and fossil fenestrates. Although number of ten- tacles per zooid can not be determined directly in fos- sils, apertural stylets, where present, are taken as Indicators of tentacle number because they are typi- Cally greatly consistent intraspecifically in number and Size just as tentacles themselves are constant in modern bryozoans. Interpretation of niche or trophic differentiation among Warsaw fenestrates (or any other bryozoans) requires estimating approximate tentacle length, lo- Phophore diameter, and mouth diameter. Lacking soft Parts, an indirect means of approximating these di- mensions must be found in fossil bryozoans. Modern ascophoran cheilostomes offer a suitable analogue for the fenestrates. In both groups, there is a larger degree of intraspecific consistency in size and shape of both autozooecial chambers and apertures and a general reg- ularity of pattern to the zoaria (Winston, 1977). In my work, I observed that like the fenestrates, many as- Cophoran cheilostome species exhibit equal aperture Spacing over the zoarium surface, with apertures form- Ing an even gridwork across the colony. This pattern lophophore diameter tentacle length tentacle angle lophophore feeding zone aperture (orifice) zooecium 5 Text-figure 23.—Schematic illustration ofthe obverse zoarial sur- ace of Cryptosula pallasiana (Moll, 1803), showing characters used °F niche differentiation and lophophore feeding zones. Observe the almost complete coverage of the obverse surface by these feeding Zones. Tentacle number = 16; tentacle length = 0.749 mm; lophop- Ore diameter = 0.796 mm; zooecium length = 0.742 mm; zooecium nh 7 0.479 mm; orifice width — 0.188 mm; mouth diameter — a 69-0.047 mm; fecal pellet size = 0.080-0.127 mm; mean diagonal Perture spacing = 0.531 mm (most dimensions from Winston, 1977). suggests partitioning of the surface into individual zooecial feeding zones. Aperture spacing can vary ap- preciably between species, but does not vary substan- tially within most species of fenestrates and ascophor- an cheilostomes. Winston (1977) reported a size correlation between tentacle length, lophophore diameter, and diameter of the mouth. Tentacle length and lophophore diameter means were found to be approximately equal within any species, most lying within 10% to 20% of each other, with a maximum of +40%. The angle between tentacles and plane of obverse surface when the loph- ophore was extruded was not presented by Winston. Reapplying data from Winston’s study, mouth diam- eters are consistently found to measure approximately 10% of the lophophore diameter. In an interpretation of Winston’s data, the regular ascophoran cheilostome species Cryptosula pallasiana is used herein to determine the relationship between aperture spacing across the zoarial surface, tentacle number, and lophophore diameter (Text-fig. 23). Spac- ing between aperture centers along and diagonally across the zoarial surface yields a range of from 0.395 mm to 0.585 mm, with a mean value of 0.531 mm and a coefficient of variation of 10.48. This mean measure- ment corresponds closely to two-thirds of the mean lophophore diameter of 0.796 mm. Spacing of loph- ophores in a regular pattern over the obverse surface would seem most advantageous to the colony, as it would allow uniform tentacle coverage of the major portion of the zoarial obverse surface, resulting in ef- ficient use of food resources. Partitioning of the obverse surface into evenly divided, uniformly positioned feed- ing areas for each lophophore of C. pallasiana is il- lustrated in Text-figure 23. Based on the analysis of C. pallasiana and other data from Winston’s works, the following conclusions con- cerning soft part dimensions and their relationship to preservable skeletal features are drawn: 1. Tentacle length and lophophore diameter typically approximate each other (within + 10% to 20%). Fol- lowing Winston, the lophophore is a symmetrical, conically shaped feeding organ with the mouth po- sitioned at the tip of the cone. 2. Mean spacing of closest aperture centers across the obverse zoarial surface is approximately two-thirds the mean lophophore diameters, or lophophore di- ameter equals 1.5 times closest aperture spacing (based on analysis of C. pallasiana). . Diameter of the mouth can be determined two ways: (a) +10% of the measure of the lophophore diam- eter; and (b) approximately 40% of the width of the orifice (aperture). 4. A direct relationship is observed between lopho- phore and mouth diameter in modern Bryozoa (Win- w 166 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 ston, 1977, p. 247, fig. 4). Chamber volume (cal- culated from Winston, 1977, table 1) is found also to increase proportionally to lophophore and mouth diameter. The above relationships provide a means by which the probable soft part dimensions can be calculated (i.e., tentacle length and lophophore and mouth di- ameter) for fossils from skeletal dimensions. Once mean spacing of closest apertures is found, this is multiplied by 1.5 to determine lophophore diameter, which in turn approximates (+ 10% to 20%) the tentacle length. Mouth diameter can next be determined as approxi- mately + 10% of the lophophore diameter and checked by comparing this measurement with 40% of that of the orifice (aperture) width. These two measurements should be equal approximately. Interpreted lophophore feeding zones for Banastella guensburgi, a Warsaw fenestrate species exhibiting moderately uniform aperture spacing are illustrated in Text-figure 24. Spacing of aperture centers along, across, and between branches gives a range of 0.320 to 0.660 mm, with mean values quite similar, ranging from 0.419 to 0.452 mm, and standard deviations of 11.98 to 18.83. Iflophophore diameter in B. guensburgi were 1.5 x mean aperture spacing (as in C. pallasiana), then coverage of the obverse surface would have been rel- atively complete (Text-fig. 24). Text-figure 25 shows mean ranges of aperture spac- ing along, across, and between branches across the fe- nestrule in Warsaw fenestrate species. The pronounced similarities in all three dimensions for most species of meshwork fenestrates are considered important to my hypothesis: they are considered to reflect colony in- tegration for feeding purposes. Such integration is not a new idea, but has been developed in works of nu- merous authors for both recent and fossil Bryozoa (Banta, McKinney, and Zimmer, 1974; McKinney, 1977; Cook, 1977; Winston, 1978). More open mesh- work in some species produces anomalously large spac- ings between branches across the fenestrule relative to spacings along and across the branch, due to wider branch spacings. This might reflect response to currents or even lack thereof, although this is a tenuous hy- pothesis. POSSIBLE NICHE DIFFERENTIATION IN WARSAW FENESTRATE BRYOZOA Interspecific variation in tentacle number, lopho- phore size, and mouth size are criteria used to indicate, probably, the separation of trophic resources in mod- ern cheilostomes. Such criteria can be also applied to meshwork fenestrates for recognition of niche parti- tioning. In modern bryozoans a direct relationship has been observed between orifice (aperture) diameter and mouth diameter, as has a relationship between mouth and lophophore diameters. Text-figure 26 illustrates in- ferred mouth diameter (based on 40% minimum ap- erture dimension) plotted against lophophore diameter (calculated from 1.5 x the closest aperture spacing across the zoarial surface) for Warsaw meshwork fe- nestrates. Arithmetic means of characters are used for interpreting soft-part dimensions; use of character ranges in these interpretations is deemed unnecessary due to their extremely low coefficients of variation and consequently low ranges. (Character ranges and coef- ficients of variation are given for all respective species in section on systematics.) From Text-figure 26D, a grouping of species occur in the range of the range of 0.025 to 0.040 mm mouth diameter and 0.259 to 0.400 mm lophophore diameter. The remaining species, with the exception of a few anomalies, plot in a linear man- ner, showing that species with inferred larger mouth sizes typically have inferred larger lophophores. Win- ston (1977) observed similar distribution of mouth size versus lophophore diameter in modern species, and suggested larger mouth and lophophore sizes for spe- cies indicates the ability to exploit larger size food particles. Text-figure 26A-C shows plots of species restricted to the northern, occurring throughout, and restricted to the southern parts of the study area, respectively. Similarities in values observed in Text-figures 26A and 26C suggest species replacement between the northern and southern areas, thus suggesting similar niches. Spe- lophophore feeding zone aperture (orifice) branch dissepiment fenestrule Text-figure 24.—Schematic illustration of the obverse surface of Banastella guensburgi, n. sp., showing characters used to infer niche differentiation and possible positioning of lophophore feeding zones. Such zones form a moderately even, overlapping covering of the obverse zoarial surface in most meshwork fenestrate species. Ten- tacle number = 18; tentacle length = 0.629 mm; lophophore di- ameter — 0.629 mm; zooecium length — 0.589 mm; zooecium depth — 0.224 mm; zooecium width — 0.174 mm; zooecial volume — 0.023 mm; aperture (orifice) length = 0.196 mm; aperture (orifice) width = 0.165 mm; mouth diameter (10% of lophophore diameter) = 0.063 mm; mouth diameter (40% of aperture width) = 0.066 mm; aperture spacing along branch = 0.437 mm; aperture spacing across branch — 0.419 mm; aperture spacing between branches — 0.452 mm. MISSISSIPPIAN BRYOZOANS: SNYDER cies might possess slightly larger lophophore diameters relative to mouth size in the southern area. In some species of fenestrates, stylets surround the autozooecial aperture. Based on their largely consistent interspecific number, size, and positioning, these sty- lets are interpreted as tentacle guides, with their num- ber equal to or closely approximating the number of tentacles. Text-figure 27 illustrates calculated tentacle number plotted against inferred tentacle length, herein Considered approximately equal to the lophophore di- ameter (see above). As inferred tentacle count increas- €s, so does inferred tentacle length in many extant Species, although this relationship is not as clear as that between mouth and lophophore diameters. A general similarity between Text-figures 27A and 230 again suggests species replacement between the Northern and southern areas, although data points are relatively few. 167 Table 50 and Text-figure 28 show clearance rate cal- culated for all Warsaw meshwork fenestrates (per Strathmann, 1973; see above), along with parameters used in clearance rate determination and calculated chamber volume. If chamber volume indeed approximates polypide dimensions, assuming similar interspecific metabolic rates, an increase in calculated clearance rate should be proportional to increased chamber volume. Al- though an anomalous reading is given by species num- ber 37, a general increase in chamber volume is as- sociated with increased calculated rates, and presumably ability of polypide to gather food. Twenty of the 37 Warsaw species do not possess apertural stylets and thus do not lend themselves to calculation ofinferred clearance rates. The relationship of increased clearance rates to increases in chamber volume allows additional interpretations to be made .95 15 ‚25 35 .45 .55 65 75 .85 ; a. A BT : ' À à; À 2 AB C i ETRE RANGE OF APERTURE SPACINGS 4 BA [e] 5 AC B 6 ABC 7 A B [e 8 BCA 9 A B. C 10 A CB cc "3 EAG u 12 BE ING Mm 13 BA [o = 14 B A C =) m B A (o z 16 B A C o dut rem c iu 18 EA 5 O 19 AB u fe BA c Qa E AB c 10) 22 B A c " BA io 24 AB G < 25 BAC o [e ABC T 2T BA C » 28 BA C < 29 BA G 3o — BAC 31 A B 32 B A ® 33 B A ic 34 B A c 35 B A Cc 36 B A [9] 37 B A C E Text-figure 25.—Range of aperture spacing over obverse zoarial surface for Warsaw meshwork fenestrates. A = spacing along branch; B = Pacing across branch; C = spacing between branches across fenestrule. The more nearly equal all three spacings are, the more even the feeding rid developed across the zoarial obverse surface by the lophophores. Measurements A and B more commonly approach each other than do ĉasurements of C. Trivial names corresponding to assigned species number are given in Table 47. 168 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 on species both with stylets and without. Following the observations presented in previous paragraphs, as chamber volume increases and therefore a larger poly- pide occupies the chamber, an increase in mouth and lophophore diameter is expected. Text-figures 29 and 30 plot calculated mouth di- ameter (based on 0.4 x aperture minimum dimension) and calculated lophophore diameter (based on 1.5 x closest aperture spacing), respectively, against auto- zooecial chamber volume. In Text-figure 29, a group- ing of inferred mouth diameters between 0.025 and 0.040 mm is found at chamber volumes of between 0.0025 and 0.0080 mm}, with the remainder exhibiting steady increase of inferred mouth diameter (0.4 x ap- erture minimum dimension) and corresponding cham- ber volumes. Text-figure 30 exhibits a grouping of inferred lophophore diameters in the lower chamber- volume ranges, between 0.0025 and 0.0080 mm?, with a steady increase in inferred lophophore diameter (1.5 X closest aperture spacing) corresponding to increasing chamber volumes. Correspondence of species exhib- iting increases in both apparent mouth diameter (i.e., aperture size) and inferred lophophore diameter (i.e., 26A 0.08 = E nc J u 0.07 A z 14 a 006 = > 0.05 19 o = a = 0.04 2A Az = T 2 0.034 32 9 22 < © 0.02 0.20 0.25 030 035 0.40 045 050 055 0.60 0.65 0.70 LOPHOPHORE DIAMETER mm 26B 0.08 E E a 0.07 3 o 20 13 = 34 35 3 006 Oo o 18 ae 1217 = 2 0.05 E O = $ uj 0.04 3 23 18 4 E 26 3 Rs) 2 0.03 O 3 920% O q 7 19 © 002 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 LOPHOPHORE DIAMETER mm aperture spacing) with increase in chamber volume is extremely good, fitting the observation in modern spe- cies that increase in lophophore and mouth diameter occur together. Text-figures 29A and 29C exhibit sim- ilar patterns resulting from similar niche placement of different species between the northern and southern areas, as do Text-figures 30A and 30C. Trends in spe- cies character of this type suggest niche replacement by species in essentially the same community between the northern and southern parts of the study area. Al- though species composition of the community has changed, niche positioning within the community does not appear to have changed appreciably. Within the Warsaw’s meshwork fenestrate domi- nated communities, niche differentiation could have occurred on two levels: 1. Position within the physical environment, including both height above the sea floor and location relative to direction of current flow. Ausich (1978, 1980) considered height above the sea floor to be significant in Mississippian crinoid niche differentiation. Height 26C 0.08 E = cc P007 5 < 11 = 0.06 = 2 0.05 m 9 37 z [133 a El] tu 0.04 2 8 E 10 E 31 2 0.08 23 E O a f Ed O 0.02 TE 0.20 0.25 030 035 0.40 045 0.50 055 0.60 0.65 0.70 LOPHOPHORE DIAMETER mm 26D E 0.08 _— E $5 0.07 na 5 9 o A m < e a 0.06 i e ò E A 3 0.05 m = a ô a Ul 0.04 Cdi = = A A® P AA Pa 2 0.03 A o 9H = o e E e © 0.02 0:25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 LOPHOPHORE DIAMETER mm e by o Text-figure 26.— Relationship of mouth diameter (calculated as 4096 of minimum aperture diameter) to lophophore diameter (calculated as 1.5 x closest aperture spacing) for Warsaw meshwork fenestrates. The general trend of increased mouth diameter appears as a function O increased lophophore diameter in most species. Species numbers correspond to those on Table 47, which also shows their names. A, spec occurring only in the northern half of the study area (species numbers enclosed by A); B, species occurring throughout the study area (species numbers enclosed by O); C, species occurring only in the southern half of the study area (species numbers enclosed by LJ); D, all species. ies MISSISSIPPIAN BRYOZOANS: SNYDER 169 is of more minor significance among the Warsaw fenestrates as zooecia are of uniform size throughout the zoarium, and thus do not exhibit the vertical Stratification suggested by Ausich for the crinoids. . Competition for available food resources. Food size selection, considered secondary by Ausich in crinoid communities, is herein considered the dominant means of trophic structuring in Warsaw fenestrate communities. N Among modern suspension-feeding assemblages, trophic structuring is suggested by broad interspecific variation among organisms dependent on a common food supply (Winston, 1977), consisting of phyto- plankton varying in size but generally under 50 um in diameter. Further, increased food-gathering capabili- ties and ability to assimilate larger size food particles 1n modern species are associated with larger individual polypides and their enclosing zooecium. Zoaria of different Warsaw species exhibiting simi- larity in some physical characteristics (i.e., height, width, robustness, and — as can best be determined 27A LOPHOPHORE DIAMETER mm e a a 29 30 0 5 10 15 20 25 30 35 TENTACLE NUMBER - APERTURAL STYLETS TENTACLE LENGTH 27B LOPHOPHORE DIAMETER mm e e a o o a © [^] a O 29 S TENTACLE LENGTH o pO [s] 0 5 10 15 20 25 30 35 TENTACLE NUMBER - APERTURAL STYLETS — orientation to each other and to current direction) express pronounced differences in zooecial skeletal di- mensions and shapes, which suggests different polypide sizes and/or shapes. Zooecia with larger chamber di- mensions are associated with characters interpreted to allow the individual greater food gathering capability; such increased capability is directly related to the abil- ity of the individual polypide to assimilate larger size food particles in modern species. Consequently, par- titioning of resources based on food particle size ap- pears to have occurred in Warsaw meshwork fenes- trates. Where taxa of similar zooecial morphologies are sympatric, differences such as behavior with regard to suspended particles, feeding height, and positioning across the sea floor relative to current direction could have been significant. Understanding what effects these differences could produce on niche differentiation in modern bryozoans might allow their use as an analogue for fossils; however, such studies have not been un- dertaken. Schoener (1974) observed that although species sim- 27C 0.65 0.60 ze] 0.55 0.50 0.45 LOPHOPHORE DIAMETER mm 0.40 o Elss .35 0.3 - 10 D 0.30 a 0.25 0 5 10 15 20 25 30 35 TENTACLE NUMBER = APERTURAL STYLETS TENTACLE LENGTH 27D E c 0.65 u = = 0.60 L < = a e Q w 0.55 a 4 . x E 0.50 2 & 0.45 "S Pe e P wt 040 e m u 2 0.35 ne * i LJ u = w A d 090 Pen x E 0.25 u 0 5 10 15 20 25 30 35 TENTACLE NUMBER - APERTURAL STYLETS Text-figure 27.— Relationship between tentacle length (= lophophore diameter) and tentacle number (= number of apertural stylets) for the 17 Species of Warsaw meshwork fenestrates that bear apertural stylets. Species numbers correspond to those in Table 47, which also shows = names. A, species occurring only in the northern half of the study area (species numbers enclosed by A); B, species occurring throughout 3 ge area (species numbers enclosed by O); C, species occurring only in the southern half of the study area (species numbers enclosed by > D, all 17 species. 170 ilarities exist in one of several dimensions, dissimilar- ities can and frequently do exist in others. Although height above the sea floor and orientation to direction of currents are observed in some individuals and ap- pear significant to niche differentiation, the difficulty in gathering precise data which yield significant con- fidence in their application to a species population pro- hibits use of this in any but a broad sense. CONCLUSIONS Winston (1977) demonstrated that bryozoan species within a fauna specialize in food based on particle size, with a correlation between particle size and mouth size. Mouth dimension is considered critical by Winston in determining niche differentiation. Clearance rate (based on tentacle length and tentacle number), when consid- ered in conjunction with lophophore diameter and zooecial character (predominantly dimensions), were proposed to be factors in partitioning of resources by different modern species. From Winston’s work, in- creased clearance rate is associated with increased mouth and lophophore diameters, which in turn occur 28A æ 250 E a 9 2.25 N 200 = ul ES 150 A = 14 ur 1.25 o = < 1.00 a q ui 0.75 29 o = 0.50 - 2 0.25 30 x< < = 0.00 0.000 0.005 0.010 0.015 0.020 0.025 0.030 CHAMBER VOLUME = (LxWxD) mm? 28B Œ 2.50 E S 2.25 O 36 8 2.00 ur w Kr 1.50 4 x 8 1.25 Q 6 Oo & 1.00 dis e O = 19 uy ul 9.75 2 35 = 0.50 4 e] E O 18 x 0.25 : 9 = 0.00 O 0.000 0.005 0.010 0.015 0.020 0.025 0.030 CHAMBER VOLUME = (LxWxD) mm? PALAEONTOGRAPHICA AMERICANA, NUMBER 57 in conjunction with increased chamber volume in modern species. Intraspecific consistency of the above features is great; however, great interspecific variability commonly exists, suggesting trophic structuring. Fur- ther, consistent trends of increased polypide size and clearance rate associated with increased mouth size and thus increased size of food particle assimilable indicate that polypide size and clearance rate are pa- rameters also worth considering when determining possible niche differentiation between modern species. Parameters applied to modern species can be inter- preted for Paleozoic meshwork fenestrates in the fol- lowing manner, based on analysis of and comparison to modern cheilostomes: 1. mouth diameter = 0.4 X minimum aperture di- mensions or 0.1 x lophophore diameter. 2. lophophore diameter = 1.5 x closest aperture spac- ing across the zoarial surface. 3. tentacle length = lophophore diameter. 4. polypide size = autozooecial chamber volume. 5. tentacle number = number apertural stylets (where present). 28C tr I 2.50 a ipi [s] X 2.00 = u 1.75 ul A 1.50 11 ee ae = 1.00 ae a m BOND 8 o = g 3 0.50 E 33 z 10 2 s 025] [El 37 < 2 = 0.00 0.000 0.005 0.010 0.015 0.020 0.025 0.030 0.035 CHAMBER VOLUME = (LxWxD) mm? 28D t£ 25 " I 2.50 pit a o 225 e [e] N 2.00 z # t75 w L| Z asi) e cc w 1.25 e & 1.00 NL e 5 pa e I 0.75 a = - 0.50 á mo ® m E 025| "m * = 0.00 0.000 0.005 0.010 0.015 0.020 0.025 0.030 0.035 CHAMBER VOLUME = (LxWxD) mm? Text-figure 28.— Relationship of maximum clearance rate and chamber volume for the 17 species of Warsaw meshwork fenestrates in which number of tentacles can be indirectly determined. Observe the moderately good correlation between chamber volume and clearance r: ate in the species analyzed. Species numbers correspond to those shown in Table 47, which also shows their names. A, species occurring only in the northern half of the study area (species numbers enclosed by A); B, species occurring throughout the study area (species numbers enclos (O); C, species occurring only in the southern half of the study area (species numbers enclosed by O); D, all 17 species. ed by MISSISSIPPIAN BRYOZOANS: SNYDER Table 50.— Calculated tentacle lengths, clearance rates, and cham- ber volumes for species with determinable tentacle numbers, in order of increasing chamber volume. Explanations of species numbers are shown in Table 47. maximum clearance tentacle rate chamber Species tentacle length (ml/ volume number number (cm) hr/zooid) (mm?) 1 6.42 0.0347 0.31 0.0019 2 4.33 0.0345 0.21 0.0024 30 10.50 0.0282 0.41 0.0026 29 20.58 0.0305 0.88 0.0030 31 11.50 0.0330 0.53 0.0038 9 2.00 0.0341 0.10 0.0041 19 16.28 0.0420 0.96 0.0043 10 9.00 0.0359 0.45 0.0055 18 8.58 0.0393 0.47 0.0065 8 10.42 0.0569 0.83 0.0081 12 21.08 0.0414 1:22 0.0153 33 11.58 0.0369 0.60 0.0166 16 1521 0.0521 1.11 0.0167 34 20.67 0.0411 1.19 0.0190 35 12.67 0.0437 0.78 0.0201 36 30.50 0.0527 2.25. 0.0225 11 18.29 0.0629 1.61 0.0230 13 12.96 0.0564 1.02 0.0267 14 20.25 0.0548 1259 0.0278 37 TEAS) 0.0285 0.31 0.0299 29A g 0081—— E E 0.07 A^ S 0.06 14 T 5 A O 0.054 15 = a Hi 0.04 x 28 21 e 0.03 30 29 ^ a 22 9 002 0.000 0.005 0.010 0.015 0.020 0.025 0.030 CHAMBER VOLUME = (LxWxD) mm3 29B E 0.08 B x W 0.07 O E 9o * q Q 0.06 E OS S O 0.05 E: ql 0.04 1804 2n Si 26 Q 5 CO 230 0 x o %95 9 n. 19 0.000 0.005 0.010 0.015 0.020 0.025 0.030 CHAMBER VOLUME - (LxWxD) mm3 171 The same proportional size increases present in modern species are observed in Warsaw meshwork fenestrates, and thus based on these calculations, tro- phic structuring appears to have existed among these fossils. Predominance of a single group of organisms, in this case meshwork fenestrates, using similar food sizes at a time when predation levels were presumed small, sugests interspecific competition for food re- sources leading to niche differentiation. The difficulties biologists experience in defining in- terspecific competition and niche differentiation in modern organisms are numerous and varied (Schoe- ner, 1974), contain many unresolved areas, and thus suggest even greater problems and pitfalls for the pa- leontologist. However, exceptionally well-preserved materials, such as those found in the Warsaw, can pro- vide unexpected insight into the history of ecologic dynamics. APPENDIX A DESCRIPTIONS OF WARSAW FORMATION SAMPLED OUTCROPS AND LOCALITIES Columnar sections for some localities are included 29C 0.04 10 0.03 CALCULATED MOUTH DIAMTER mm o o a El 0.02 0.000 0.035 0.010 0.015 0.020 0.025 0.030 CHAMBER VOLUME = (LxWxD) mm3 0.005 29D 0.04 A A9 mU. e XU et CALCULATED MOUTH DIAMTER mm o o a a 0.02 0.000 0.005 0.010 0.015 0.025 CHAMBER VOLUME = (LxWxD) mm3 0.020 0.030 0.035 Text-figure 29.—Relationship between inferred mouth diameter and calculated chamber volume for some Warsaw meshwork fenestrates. Pecies numbers correspond to those shown in Table 47, which also gives their names. A, species occurring only in the northern half of the vod area (species numbers enclosed by A); B, species occurring throughout the study area (species numbers enclosed by O); C, species “urring only in the southern half of the study area (species numbers enclosed by D); D, all species. St 132 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 as Appendix B; these sections were used for analysis of faunal occurrence. Brief lithologic descriptions are provided here for sections not so illustrated. 1. Augusta Northwest. W Y NE Ya, sec. 8, T. 69 N., R. 4 W., Des Moines County, Iowa (no quadrangle map available at time of study). Section described by Harris and Parker (1964), exposed on north side of dirt road approximately 4 mi west of Augusta, Iowa. Mea- sured from stream base and correlated with road cut following re- sistant bed connecting the two. Exposure consists of 7' Keokuk (cherty, crinoidal, and bryozoan biocalcarenite interbedded with thin shale) conformably overlain by 24' Warsaw (fossiliferous argillaceous shale and thin calcarenitic beds containing abundant bryozoan skeletal debris). Keokuk-Warsaw contact picked on change in lithology from moderately massive calcarenite to predominantly argillaceous shale with calcarenite interbeds. Exposure moderately overgrown and fos- sils leached. Possibly 14" overgrown and very poorly preserved So- nora (Spergen) unconformably overlying Warsaw. Sonora a cross- bedded calcareous sandstone. 2. Bentonsport, Iowa. SE % SE Ya, sec. 35, T. 69 N., R. 9 W., Van Buren County, Iowa. Bonaparte Quadrangle, 1:24,000; 1968. From downtown Bentonsport, proceed two blocks northwest, then right and proceed four blocks northeast. Section measured exposed in ditch along east side of road cut toward top of hill. Exposure consists 30A LOPHOPHORE DIAMETER mm 8 0.000 0.005 0.010 0.015 0.020 0.025 0.030 CHAMBER VOLUME - (LxWxD) mm3 30B LOPHOPHORE DIAMETER mm E 0.25 0.000 0.005 0.010 0.015 0.020 0.025 0.030 CHAMBER VOLUME = (LxWxD) mm3 Text-figure 30.—Relationship between lophophore diameter and chamber volume for some Warsaw meshwork fenestrates. As with mo diameter, an increase in lophophore diameter is normally observed with increased chamber volumes. Species numbers correspond to th shown in Table 47, which also gives their names. A, species occurring only in the northern half of the study area (species numbers enclo by ; A); B, species occurring throughout the study area (species numbers enclosed by O); C, species occurring only in the southern half of the study area (species numbers enclosed by O); D, all species. of 14' Keokuk (fairly massive, crinoidal calcarenite) conformably overlain by approximately 6' of Warsaw (interbedded lenticular bryozoan calcarenite with argillaceous shale). Keokuk-Warsaw con- tact picked on lithologic change from crinoidal calcarenite to lentic- ular bryozoan calcarenite interbedded with argillaceous shale. Ex- posure fresh, fossils well-preserved and moderately abundant. See columnar section on p. 177. 3. Lacy Keosauqua. N Y. SW 4, sec. 1, T. 68 N., R. 10 W., Van Buren County, Iowa. Keosauqua Quadrangle, 1:24,000; 1968. Two large, and numerous smaller exposures along main road leading into Lacy Keosauqua Park. Exposures measured: (1) 0.7 mi in from park entrance along small stream valley on north side of road. Exposed is 5'2” calcareous, unfossiliferous shale (Warsaw) unconformably overlain by 16' cross-bedded calcareous sandstone (Sonora); (2) 150 yards downstream from first exposure is found 11'8" of unfossili- ferous calcareous shale (Warsaw) containing small amounts of chert unconformably overlain by 2'4" of cross-bedded calcareous sand- stone (Sonora). Relative thicknesses of both formations vary con- siderably laterálly due to the unconformable boundary between them. Warsaw-Sonora contact picked on abrupt lithologic change from unfossiliferous calcareous shale to cross-bedded calcareous sand- stone. Exposure well-weathered and partly overgrown in stream cut. 4. Niota, Illinois. E. '» NW Ya, sec. 17, T. 7 N., R. 8 W., Hancock County, Illinois. Niota Quadrangle, 1:24,000, 1964. Section exposed along west bank of stream valley on road southeast of Niota, Illinois. Measured section starts 50' upstream from power lines crossing road 30C n 0.40 Or 0.35 2,0 - 2 31 0.30 C37 LOPHOPHORE DIAMETER mm 0.25 0.000 0.005 0.010 0.015 0.020 0.025 0.030 0.035 CHAMBER VOLUME = (LxWxD) mm? 30D 0.40 " e em 035] em Ho bs 7 = A LOPHOPHORE DIAMETER mm 0.30 = 0,25 035 0.000 0.005 0.010 0.015 0.020 0.025 0.030 0. CHAMBER VOLUME = (LxWxD) mm? uth ose sed MISSISSIPPIAN BRYOZOANS: SNYDER 173 and extending up stream valley for approximately Y. mi. Exposure Consists of 42’ Warsaw (unfossiliferous to locally fossiliferous cal- careous and argillaceous shale interbedded and locally containing abundant small geodes) conformably overlain by 6’ Spergen (massive laminated and cross-bedded silty dolostone probably representing channel deposits and silty calcareous shale) unconformably overlain by thin conglomeratic zone consisting of Spergen and St. Louis lithic clasts, topped by approximately 2’ of bedded St. Louis Limestone. Contacts picked on the lithic changes described above. Although exposure moderately fresh where cut by stream, fossils are highly leached and poorly preserved. 5. Iowa Terminal. NW '4 SW 1⁄4, sec. 19, T. 66 N., R. 5 W., Lee County, Iowa. Keokuk Quadrangle, 1:24,000; 1964. Section expo- Sure along railroad tracks and roadway cut in cliff along Mississippi River for grain terminal. Section measurement starting 150 yards South of road crossing railroad tracks; measurements carried to ex- cellent exposure in cliff along roadcut to the south side of the road. Exposure consists of 1534’ of Keokuk (cherty, crinoidal biocalcar- enite) conformably overlain by 52'^' of Warsaw (bryozoan biocal- Carenite interbedded with argillaceous shale and thick accumulations of argillaceous shale locally containing dolomitic and geodiferous Zones) conformably overlain by 8’ of Sonora (massive lamellar and Cross-bedded calcareous sandstone with thin shale interbeds), which IS in turn overlain unconformably by highly weathered St. Louis Limestone (calcilutite varying in thickness from 2’ to 23’). Keokuk- arsaw contact picked on pronounced increase in argillaceous shale (dominant over calcarenites, which characterize the Keokuk). War- saw-Sonora and Sonora-St. Louis contacts picked on abrupt litho- logic changes and unconformable nature of the contacts. Exposure very fresh, highly fossiliferous, with skeletal debris generally well- Preserved; excellent outcrop. See columnar section on p. 177. 6. Keokuk Industrial. SW Y NW Ya, sec. 35, T. 65 N., R. 5 W., Lee County, Iowa. Keokuk Quadrangle, 1:24,000; 1964. Good ex- Posures of Keokuk and Warsaw west of river road along Keokuk Industrial area. Section measured directly across from Foote Mineral Co., approximately 100’ north of transformers on west side of road South of main entrance to Foote. Exposure consists of 21%’ Keokuk (cherty, crinoidal biocalcarenite interbedded with thin beds of bryo- zoan fossiliferous argillaceous shale) conformably overlain by 29.3' of Warsaw (bryozoan fossiliferous argillaceous shale, calcareous fos- Siliferous shale, and thin beds of fossiliferous biocalcarenite). Keo- i Uk-Warsaw contact picked where argillaceous shale becomes dom- Mant lithic component. Exposure fresh, with fossils both abundant and well-preserved. See columnar section on DITA 7. White Hollow. NW 44 SE Ya, sec. 26; T.65 N, R- 5 W., Lee County, lowa. Keokuk Quadrangle, 1:24,000; 1964. Good exposure of Warsaw on north side of streamcut approximately Y. mi upstream from its joining with the Mississippi River. Consists of 32' argilla- Ceous Shale, calcarenite, and calcilutite containing geodes and cherty lenses on the bottom of the exposure overlain by 11' of fossiliferous “alcarenite and argillaceous shale. Exposure moderately fresh, con- faining abundant, although frequently slightly leached, fauna toward the top. See columnar section on p. 178. 8. Keokuk West. SE 4 NE WA, sec. 33, T. 65 N., R. 5 W., Lee Coun- ty, Iowa, Keokuk Quadrangle, Illinois-Iowa-Missouri, 1:24,000; ~ Partially overgrown exposure of Warsaw in roadcut on west © of U. S. Highway 61 at north end of Des Moines River bridge. Xposure consists of 24' of geodiferous shale interbedded with ar- Sillaceous dolomite and calcarenite. E 9. Grays Quarry. SW Ys NE Ya, sec. 31, T. 5 N., R. 8 W., Hancock EU Illinois. Hamilton Quadrangle, 1:24,000; 1964. Measured = Ction taken in northeastmost corner of quarry along road leading P north quarry face; measurement started approximately 5’ below in uec Warsaw contact, however, over 80' of Keokuk is exposed lifer e ey. Warsaw consists of 3934’ of predominantly unfossi- en 9us, geodiferous argillaceous dolomicrite, micrite, calcarenite, Shale. A small number of bryozoan fragments are observed in thinly bedded calcarenite present toward the top of the measured section. Keokuk-Warsaw contact picked where massive calcarenite is conformably overlain by argillaceous geodiferous dolomicrite. Ex- posure is very fresh, but fossil fragments are frequently leached and poorly preserved. See columnar section on p. 178. 10. Hamilton-Warsaw Roadcut. S Y NE %, sec. 2, T. 4 N., R: 9 W., Hancock County, Illinois. Warsaw Quadrangle, 1:24,000; 1964. Ex- cellent exposure of Keokuk and Warsaw on east side of Hamilton- Warsaw road, extending along road uphill from stream valley to entrance to Kibbe Station. Exposure consists of over 80’ of Keokuk conformably overlain by Warsaw. Measured section includes upper 18' of Keokuk (massive cherty biocalcarenite) overlain by approx- imately 38’ Warsaw (argillaceous fossiliferous and unfossiliferous shale with thin beds and lenses of highly bryozoaniferous biocal- carenite). Keokuk-Warsaw contact picked where change in domi- nant lithic type from cherty biocalcarenite to argillaceous shale oc- curs. Exposure moderately fresh along roadcut, with fossils well- preserved and abundant, but large spalled slabs atop shale starting to cover lower shale. See columnar section on p. 179. 11. Geode Glen (type section of the Warsaw). SE Ya, sec. 4, NE Ys NE Ya, sec. 9, and NW Y, sec. 10, T. 4 N., R. 9 W., Hancock County, Illinois. Warsaw Quadrangle, 1:24,000; 1964. Warsaw, Sonora, and St. Louis formations exposed in stream valley (Geode Glen) at north edge of Warsaw, extending upstream to south side of highway. War- saw at this locality informally divided into lower and upper members by Ulrich (1890); such a division does not appear appropriate and is not followed herein. Exposure consists of 74’ Warsaw (bottom 40’ argillaceous geodiferous dolomicrite occurring in moderately thick beds interbedded with dolomitic argillaceous shale; upper 34’ con- sists of fossiliferous argillaceous shale with beds of fossiliferous bio- calcarenite and argillaceous biocalcarenite), unconformably overlain by 5.3’ Sonora (massive biocalcarenite) which is unconformably overlain by 3.3’ St. Louis (massive cherty micrite, locally brecciated). Warsaw-Sonora-St. Louis contacts picked on lithic changes and unconformable surfaces. Moderately well-exposed outcrop; how- ever, beds had to be correlated upstream for continuity of section. Fossil fragments well-preserved in upper 34’ of Warsaw. See colum- nar section on p. 179. 12. Warsaw East. SW 4 NW 4, sec. 4, T. 4 N., R. 9 W., Hancock County, Illinois. Warsaw Quadrangle, 1:24,000; 1964. Exposure on east side of Hamilton- Warsaw road approximately Y. mi east of Warsaw. Exposure consists of 40' Warsaw; bottom 20' argillaceous dolomicrite and shale, becoming increasingly fossiliferous toward top of upper 20' of section, with lithology consisting of fossiliferous argillaceous shale and thin fossiliferous biocalcarenitic beds and lens- es. At very top of section occur several beds that appear to be chan- nel-fill deposits. Exposure moderately fresh along roadcut, but much of the fossil material is leached and poorly preserved. 13. Soap Factory Hollow. SE 1⁄4, sec. 16, T. 4 N., R. 9 W., Hancock County, Illinois. Warsaw Quadrangle, 1:24,000; 1964. Exposure of Keokuk and Warsaw in stream valley Y. mi south of Warsaw. Section started just upstream from farm house at end of dirt road, measured upstream. Exposure consists of 31' of Keokuk (massive to medium- thick beds of fossiliferous cherty biocalcarenite with argillaceous shale interbeds) conformably overlain by 19.3' Warsaw (fossiliferous biocalcarenitic thin beds and lenses in argillaceous shale; number of fossil fragments reduced, geodes in shale toward top of section). Keokuk-Warsaw contact picked where overlying shale becomes the dominant lithic component relative to the cherty biocalcarenite typ- ical of the underlying Keokuk. Exposure highly weathered, occurring in bottom of stream valley; hand-level required to correlate beds upstream. See columnar section on p. 180. 14. Buel Branch. NE Y SW 1⁄4, sec. 13, T. 2 N., R. 9 W., Adams County, Illinois. Mendon Quadrangle, 1:62,500; 1946. Good ex- posure on north side of road following Buel Branch to the Mississippi flood plain. Exposure consists of 7.7' of Keokuk (massive cherty biocalcarenite) conformably overlain by 14.9' of Warsaw (argilla- 174 ceous and calcareous shale with fossiliferous biocalcarenitic beds). Keokuk-Warsaw contact picked on break in lithic type from massive cherty biocalcarenite to predominantly shale. Moderately fresh ex- posure in roadcut, fossil fragments fairly well-preserved. See colum- nar section on p. 180. 15. Sand Branch. SW Ys NW 4, sec. 28, T. 1 N., R. 8 W., Adams County, Illinois. Mendon Quadrangle, 1:62,500; 1946. Exposure of Salem and Warsaw in abandoned quarry along Sand Branch Creek. Section measured in middle of south quarry face. Exposure consists of 17.9' of typical Salem (massive laminated and cross-bedded bio- calcarenite) conformably overlain by and interbedded with 5' of typical Warsaw (fossiliferous argillaceous shale with thin lenses of biocalcarenite). This section gives no appearance of being over- turned, and is an example of contemporaneous nature of Salem (Sonora) and Warsaw deposition in the northern part of the study area. Salem- Warsaw contact is picked on break in lithic type from massive biocalcarenite to fossiliferous shale. Exposure partially over- grown; however, fossils found in the Warsaw are complete with excellent preservation of fine detail. See columnar section on p. 180. 16. La Grange. E !^ SW Ya, sec. 35, T. 61 N., R. 6 W., Lewis Coun- ty, Missouri. La Grange Quadrangle, 1:24,000; 1950. Good exposure of Keokuk, Warsaw, and Salem in roadcut Y. mi west of U. S. High- way 61; section measured on east side of highway. Exposure consists of 1534' Keokuk (moderately massive fossiliferous cherty biocalcar- enite with thin argillaceous shale interbeds) conformably overlain by 2234' of Warsaw (locally fossiliferous argillaceous shale and cal- careous shale, both with thin dolomicritic lenses), which is uncon- formably overlain by 6.9' of Salem (massive lamellar and cross- bedded cherty and silty dolocalcarenite). Keokuk-Warsaw contact is picked on change in lithic type from cherty biocalcarenite to pre- dominantly argillaceous shale. Warsaw-Salem contact is based on lithic change from argillaceous shale to dolocalcarenite. Roadcut probably 20 years old, moderately weathered. Fossil debris frequent- ly highly leached and poorly preserved. See columnar section on p. 181. 17. Canton, Missouri — A. SE % NE %, sec. 36, T. 62 N., R. 6 W., Lewis County, Missouri. La Grange Quadrangle, 1:24,000; 1950. Section measured in roadcut 1 mi south of Canton exit on U. S. Highway 61, exposed on east side of road. Exposure consists of 12.2’ of Keokuk (cherty fossiliferous biocalcarenite) conformably overlain by 3.2’ of Warsaw (argillaceous shale and dolocalcarenite). Keokuk— Warsaw contact picked on lithic change from biocalcarenite to pre- dominantly shale and dolocalcarenite. Best exposed of Canton out- crops, containing moderately well-preserved fossil fragments. 18. Canton, Missouri - B. NW %4 NE %, sec. 33, T. 62 N., R. 6 W., Lewis County, Missouri. La Grange Quadrangle, 1:24,000; 1950. Section measured in roadcut 1 mi south of Canton exit on U. S. Highway 61, exposed on east side of road. Exposure consists of 7.8' of Keokuk (cherty fossiliferous biocalcarenite) conformably overlain by 2.4' of Warsaw (argillaceous shale and dolocalcarenite). Keokuk— Warsaw contact picked on lithic change from biocalcarenite to pre- dominantly shale. Although a partially overgrown and moderately old exposure, fossil fragments are well-preserved. 19. Canton, Missouri — C. NW % SE Ya, sec. 33, T. 62 N., R. 4 W., Lewis County, Missouri. La Grange Quadrangle, 1:24,000; 1950. Section measured in roadcut on east side of U. S. Highway 61, 1.4 mi south of Canton exit. Exposure consists of 3.3' of Keokuk (cherty biocalcarenite with thin shale interbeds) conformably overlain by 23.7' of Warsaw (geodiferous unfossiliferous argillaceous and cal- careous shales), which is unconformably overlain by 3' of Salem (massive fossiliferous cross-bedded biocalcarenite). Keokuk-War- saw contact based on lithic change from cherty biocalcarenite to geodiferous argillaceous and calcareous shale. Warsaw-Salem con- tact picked on unconformable break between the shale and massive cross-bedded biocalcarenite. Exposure moderately well-weathered and overgrown, with some Warsaw shale covered. PALAEONTOGRAPHICA AMERICANA, NUMBER 57 20. Mount Sterling. NE % SE Ya, sec. 24, T. 2 S., R. 4 W., Brown County, Illinois. Mount Sterling Quadrangle, 1:62,5000; 1926. Ex- cellent section of Warsaw 200 yards upstream from bridge crossing McKee Creek. Exposure consists of 23.6' of Warsaw (fossiliferous argillaceous shale with biocalcarenitic beds toward bottom and lens- es toward top of section). Shale and biocalcarenitic beds and lenses contain abundant and extremely well-preserved bryozoan fossils. Exposure in cut bank of stream and although fresh, the upper shale is covering the lower calcarenitic beds in many places. See columnar section on p. 181. 21. McKee Creek. Middle SE %, sec. 19, T. 2 S., R. 3 W., Brown County, Illinois. Mount Sterling Quadrangle, 1:62,500; 1926. Ex- posure in bank of small stream south of and emptying into McKee Creek, section measured upstream. Warsaw and Salem interdigitat- ing at this locality (all grouped under Warsaw in section). Exposure consists of 9.9' of Warsaw (calcareous argillaceous shale) uncon- formably overlain by 8.7' of Salem (fossiliferous cross-bedded bio- calcarenite) conformably overlain by 7.7' of Warsaw (as below), which is in turn unconformably overlain by 10.7' of Salem (as below). No faulting or folding is evident, so the above relationships appear depositional in origin. Contacts are based on lithic changes from shale for the Warsaw to biocalcarenite for the Salem. Exposure highly weathered and although fossil debris is abundant, much of it is leached. See columnar section on p. 181. 22. Versailles West. SW Y NE WA. sec. 24, T. 2 S., R. 3 W., Brown County, Illinois. Meredosia Quadrangle, 1:62,500; 1928. Measured section in roadcut on north side of dirt road going west from Ver- sailles. Section consists of 25.3' of Warsaw (argillaceous and calcar- eous shale containing moderately thick interbeds of biocalcarenite and dolocalcarenite, many of which are geodiferous). Collinson el al. (1962) refer to the section as Sonora, due to the presence of biocalcarenite and dolocalcarenite beds, but it appears these beds are channels developed in the Warsaw. Section moderately to highly overgrown, with many fossil fragments leached and poorly pre- served. See columnar section on p. 182. 23. Little Whitaker Creek. NE Y4 SE Ya, sec. 25, T. 11 N.,R. 12 W. Greene County, Illinois. Roodhouse Quadrangle, 1:62,500; 1924. Exposure along north bank of Little Whitaker Creek, 50' upstream from blacktop road over stream. Outcrop consists of 10.6' of typical Warsaw (fossiliferous argillaceous and calcareous shale interbedded with fossiliferous biocalcarenitic beds, many of which are laterally discontinuous). Exposure moderately overgrown, with many fossil fragments partially leached. See columnar section on p. 182. 24. White Hall - A. NW 4 NE Y, sec. 25, T. 11 N., R. 12 W» Greene County, Illinois. Roodhouse Quadrangle, 1:62,500; 1924. Exposure in Whitaker Creek stream bottom. Outcrop consists O approximately 4' of Warsaw (argillaceous biocalcarenite with fine interbeds of argillaceous shale). Highly weathered exposure with 4 few fossils present; however, most are leached and poorly preserved. 25. White Hall — B. NE 4 SE %, sec. 25, T. 11 N., R. 12 W., Greene County, Illinois. Roodhouse Quadrangle, 1:62,500; 1924. Exposure in stream bed of Whitaker Creek. Outcrop consists of 3.5' of typical lower Warsaw (fossiliferous biocalcarenite with thin argillaceous in- terbeds). Moderately weathered exposure, although the abundant bryozoan fossils are well-preserved. 26. White Hall - C. Middle SE Ya, sec. 25, T. 11 N., R. 12 W., Greene County, Illinois. Roodhouse Quadrangle, 1:62,500; 1924. Exposure in stream bed of Whitaker Creek. Outcrop consists of 8.2 of typical Warsaw (medium- to thin-bedded bryozoan biocalcarenite interbedded with argillaceous shale). Good, although moderately weathered, exposure; well-preserved abundant bryozoan fossils. See columnar section on p. 182. 27. White Hall - D. SE% SW %, sec. 31, T. 11 N., R. 11 Ww. Greene County, Illinois. Roodhouse Quadrangle, 1:62,500; 1924. Exposure in stream bed of Whitaker Creek approximately Y mi south of county road bridge crossing stream. Outcrop consists of 19.3 0 Á MISSISSIPPIAN BRYOZOANS: SNYDER 175 typical lower Warsaw (slightly geodiferous medium- to thin-bedded biocalcarenite turning to geodiferous argillaceous shale upsection). Exposure moderately overgrown; fossils rare, frequently poorly pre- served due to freshwater leaching of calcite. See columnar section 9n p. 182. 28. White Hall - E. SE '4 NW %, sec. 31, T. 11 N., R. 11 W., Greene County, Illinois. Roodhouse Quadrangle, 1:62,500; 1924. Exposure 100 yards south of small bridge across Whitaker Creek. Outcrop consists of 2.5’ of typical lower Warsaw in stream valley (fossiliferous biocalcarenite with thin argillaceous interbeds, small amount of geode float in stream). Moderately weathering exposure In bottom of stream valley containing well-preserved fossil debris. 29. White Hall — F. SE Ys NE Ya, sec. 25, T. 11 N., R. 12 W., Greene County, Illinois. Roodhouse Quadrangle, 1:62,500; 1924. Good ex- Posure in stream bed of Whitaker Creek. Outcrop consists of 12.1’ of lower Warsaw (predominantly geodiferous argillaceous shale in- terbedded with medium beds and lenses of bryozoaniferous biocal- Carenite). Fresh exposure containing both bryozoan fossils and ge- Odes in the lower biocalcarenite and shale, a combination of Occurrences rare in the Warsaw. See columnar section on p: 82. 30. White Hall - G. NW % SE V4, sec. 2, T. 11 N., R. 12 W., Greene County, Illinois. Roodhouse Quadrangle, 1:62,500; 1924. Exposed On north bank of Seminary Creek, section measured 50 yards east of Highway 167 bridge. Outcrop consists of 9.9' of lower Warsaw (fossiliferous cherty biocalcarenite containing moderately abundant chert nodules and interbeds; thin argillaceous shale interbeds also E Highly weathered exposure, fossils leached and poorly pre- erved 31. White Hall - H. W Y, sec. 11, T. 11 N., R. 12 W., Greene County, Illinois. Roodhouse Quadrangle, 1:62,500; 1924. Exposure IM stream bed of Seminary Creek 200 yards east of Highway 167; Outerop on both sides of stream. Outcrop consists of 3.4' of Keokuk (massive crinoidal biocalcarenite) conformably overlain by 11.8' of lower Warsaw (bryozoaniferous cherty biocalcarenite interbedded with thin bands of fossiliferous argillaceous shale). Exposure mod- ‘rately fresh. Although some fossils are slightly leached, many others are extremely well-preserved. 32. Carrollton, Illinois. NE % SW %, sec. 35, T. 9 N., R. 12 W., Greene County, Illinois. Roodhouse Quadrangle, 1:62,500; 1924. “Utcrop consists of 3.8’ of Warsaw (unfossiliferous calcareous ar- Sillaceous shale) unconformably overlain by 10.4’ of typical Salem (massive biocalcarenite with few fine shale interbeds). Exposure Moderately weathered. 33. Benchmark on State Highway 369. NW Ya, sec. 26, T. 14 N., ibe W., Scott County, Illinois. Brighton Quadrangle, 1:62,500; Es E Exposure in roadcut on north side of State Highway 369, un approximately 100 yards along highway. Exposure con- jon of 2.4' of Warsaw (unfossiliferous argillaceous shale) uncon- i on overlain by 8.1' of Salem (massive cross-bedded biocal- i enite), Moderately weathered exposure with bioclasts highly Cached. dd Otter Branch. Wh SE Ys, sec. 12, T. 7 N., R. 11 W., Jersey $ rR Ilinois. Jerseyville Quadrangle, 1:62,500; 1930. Exposure on bottom of small stream emptying into Otter Creek; section Ripa from north to south, upstream in stream bottom. Outcrop md of 11.8' of Keokuk (cherty crinoidal biocalcarenite with thin a cn shale interbeds) conformably overlain by 21 Y of War- dos EB cw argillaceous shale interbedded with medium thick- Na O lenses of cherty bryozoan biocalcarenite). Although moder- bu. Weathered and poorly exposed, bryozoan fossils are moderately a E particularly in the upper shale. See columnar section ONE McClusky West. NE 14 SW Ys, sec. 18, T. 7 N., R. 11 W., Jersey NE Illinois. Jerseyville Quadrangle, 1:62,500; 1930. Exposure & north fork of Otter Creek, north-south trending on west side of stream immediately south of road crossing stream. Outcrop con- sists of 2.4' of Warsaw (argillaceous shale) unconformably overlain by 4' of Salem (massive cross-bedded biocalcarenite). Outcrop mod- erately highly weathered and overgrown in stream valley. 36. South Fork Otter Creek. NE '4 NW Ya, sec. 17, T. 7 N.,R. 11 W., Jersey County, Illinois. Jerseyville Quadrangle, 1:62,500; 1930. Ex- posure along south fork of Otter Creek, along east-west running section of stream in stream bottom. Outcrop consists of 1.8' of Warsaw (argillaceous shale) unconformably overlain by 2.9' of Salem (fossiliferous biocalcarenite). Exposure highly weathered. 37. Briggs Branch. SW 44 NW YA, sec. 10, T. 6 N., R. 11 W., Jersey County, Illinois. Jerseyville Quadrangle, 1:62,500; 1954. Exposure in small stream bed along dirt road, much of section covered. Out- crop consists of approximately 24' of Keokuk (cherty fossiliferous biocalcarenite) conformably overlain by 6.2' of Warsaw (fossiliferous argillaceous shale interbedded with bryozoan biocalcarenite). Ex- posure highly weathered and partially covered, with fossil debris frequently leached. 38. Piasa Creek. N % SW 4, sec. 13, T. 6 N., R. 11 W., Jersey County, Illinois. St. Charles Quadrangle, 1:62,500; 1954. Exposure in roadcut along cutbank of bend in Piasa Creek, extended to quarry Ya mi east of road outcrop. Outcrop consists of 31.7’ of Warsaw (geodiferous argillaceous and calcareous shale interbedded with me- dium to thick beds of dolocalcarenite and dolocalcilutite) uncon- formably overlain by 43' of Salem (extremely massive fossiliferous biocalcarenite with thin shale interbeds). Warsaw-Salem contact picked on change in lithology from predominantly shale to biocal- carenite. Exposure moderately weathered, with fossil debris leached and poorly preserved. 39. Cuiver River. NE 4 NW 4, sec. 30, T. 49 N., R. 1 E., Lincoln County, Missouri. Mary Knott Quadrangle, 1:24,000; 1972. Expo- sure Y mi west of Cuiver River bridge on Highway 47, on north side of highway. Section consists of 24.2' of Warsaw (geodiferous and nongeodiferous argillaceous and calcareous shale) apparently conformably overlain and interdigitating with 18.8' of Salem (ex- tremely massive cross-bedded biocalcarenite with thin shale and geodiferous dolocalcilutitic interbeds). Contact between Warsaw and Salem picked on lithic break from predominantly shale to biocal- carenite. Exposure fresh, good, although some of the Warsaw shale beds are covered. 40. Troy Roadcut. NE % NE !4, sec.25, T. 49 N., R. 1 E., Lincoln County, Missouri. Troy Quadrangle, 1:24,000; 1972. Exposure in roadcut on Highway 61 1 mi south of northern Troy exits, section measured on east side of road. Measured section consists of 3.8' of Keokuk (fossiliferous cherty biocalcarenite) conformably overlain by 13.1' of typical lower Warsaw (interbedded bryozoan biocalcar- enite with fossiliferous argillaceous shale; local cherty areas are also present). Keokuk-Warsaw contact picked on lithic change from pre- dominantly cherty biocalcarenite to interbedded biocalcarenite and shale. Exposure moderately fresh along roadcut, with fossil debris well-preserved. See columnar section on p. 183. 41. Moscow Mills. SW 4 NW 14, sec. 4, T. 48 N., R. 1 E., Lincoln County, Missouri. Troy Quadrangle, 1:24,000; 1972. Exposure Ya mi east of Moscow Mills on main blacktop road leading to town from Highway 61, section measured along south side of road. Ex- posure consists of 26.2' of Warsaw (biocalcarenite interbedded with argillaceous geodiferous shale, both of which are moderately fossil- iferous). Section moderately overgrown, with fossil debris frequently poorly preserved because of leaching. 42. County Road U. SW '4 SW Ya, sec. 31, T. 48 N., R. 1 E., Lin- coln County, Missouri. Troy Quadrangle, 1:24,000; 1972. Exposure on both sides of intersection of county road U with Highway 61, section measured on west side of highway. Exposure consists of 23' of upper Warsaw (interbedded massive biocalcarenite with argilla- ceous shale and dolocalcarenite). Outcrop fresh, containing an ex- tremely well-preserved diverse bryozoan assemblage. 176 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 43. Lisbon, Missouri. NE 1⁄4, sec. 26, T. 50 N., R. 18 W., Howard County, Missouri. Arrow Rock Quadrangle, 1:24,000; 1971. Ex- posure along cutbank of Missouri River % mi south of Lisbon, Mis- souri and in an old quarry 1'^ mi south of Lisbon. Outcrop consists of 18.8’ of Keokuk (cherty biocalcarenite with thin shale partings) conformably overlain by 16.7’ of lower Warsaw (fossiliferous argil- laceous shale interbedded with medium beds to lenses of fossilif- erous, sometimes cherty biocalcarenite). Keokuk-Warsaw contact picked on lithic change from predominantly biocalcarenite to pre- dominantly argillaceous shale. Exposure moderately highly weath- ered, fossil debris fairly well-preserved. 44. Dupo Quarry. NW 4 SW Ya, sec. 27, T. 1 N., R. 10 W., St. Clair County, Illinois. Cahokia Quadrangle, 1:24,000; 1954. Expo- sure on northwest face of quarry along east bluff of the Mississippi River. Exposure consists of a total of 112.8’ of Warsaw-Salem-St. Louis, with Warsaw and Salem exhibiting a gradational contact, as do the Salem and overlying St. Louis. This exposure environmentally probably represents a high-energy bank deposit which existed throughout Warsaw, Salem and St. Louis deposition. Exposure is excellent, but access is restricted and only cursorily analyzed. 45. Meramec River Bend. NW U NE Ya, sec. 15, T. 44 N.,R. 5E., St. Louis County, Missouri. Kirkwood Quadrangle, 1:24,000; 1954. Exposure at sharp bend in the Meramec River, at what was once cutbank of river. Outcrop consists of 21.2’ of Keokuk (cherty cri- noidal biocalcarenite with thin shale interbeds) conformably over- lain by 12' of Warsaw (fossiliferous argillaceous shale interbedded with thin biocalcarenitic lenses). Contact picked on lithic change from predominantly biocalcarenite to dominantly argillaceous shale. Outcrop highly weathered, overgrown and leached. 46. Marshall Road. SE Ya, sec. 10, T. 44 N., R. 5 E., St. Louis County, Missouri. Kirkwood Quadrangle, 1:24,000; 1954. Exposure along roadcut on Marshall Road. Outcrop consists of 28' of Keokuk (cherty crinoidal biocalcarenite with thin argillaceous interbeds) con- formably overlain by 22.4' of Warsaw (fossiliferous argillaceous and dolomitic shale interbedded with fossiliferous biocalcarenite) un- conformably overlain by 6.2' of Salem (massive cross-bedded bio- calcarenite). Keokuk- Warsaw contact picked on lithic change from predominantly biocalcarenite to argillaceous and dolomitic shale. Warsaw-Salem contact picked on distinctive lithic change from shale to massive biocalcarenite. Outcrop highly weathered, overgrown and poorly exposed. 47. Cragwold Road (A and B). SE '4 NW Ya, sec. 14, T. 44 N., R. 5 E., St. Louis County, Missouri. Kirkwood Quadrangle, 1:24,000; 1954. Exposure is a composite of two outcrops in the northeast quadrant of the intersection of Interstate 270 and Interstate 44; lower part of section east of bridge crossing the Missouri River on I-44, upper section at northeast onramp to 1-270 from 1-44. Outcrop consists of 22.1' of Keokuk (cherty biocalcarenite with argillaceous shale interbeds) conformably overlain by 35' of Warsaw (fossiliferous argillaceous shale interbedded with cherty biocalcarenitic beds and lenses) apparently conformably overlain by 61.3' of Salem (massive geodiferous argillaceous calcilutite and dolocalcilutite, massive cross- bedded cherty biocalcarenite, and argillaceous shale). Keokuk- Warsaw contact picked on lithic break from predominantly bio- calcarenite to dominantly argillaceous shale. Warsaw-Salem contact established on lithic break from argillaceous shale to massive geo- diferous argillaceous dolocalcilutite. This section is particularly well- exposed and well-preserved, having fresh surfaces and good, whole fossil debris. It is also part of the Meramecian Series stratotype. See columnar sections on p. 184. 48. Columbia Roadcut. NE % SE Ys and SE '4 SE M4, sec. 22; and NW % SW !4 and SW Ys SW, sec. 23, T. 1 S., R. 10 W., Monroe County, Illinois. Waterloo Quadrangle, 1:62,500; 1955. Exposure in a long roadcut along Illinois Highway 3, about 1 mi south of Co- lumbia, Illinois; measured on west side of road from north to south. Outcrop consists of 23.6' of Warsaw (locally fossiliferous argillaceous shale with cherty and geodiferous biocalcarenitic interbeds and lens- es) apparently conformably overlain by 40.2' of Salem (massive, cross-bedded, locally cherty and geodiferous biocalcarenite with fos- siliferous argillaceous and calcareous shale interbeds). Valmeyeran rocks in this section are not typical of either the Warsaw or Salem in the Illinois Basin. Warsaw-Salem contact picked on lithic change from predominantly argillaceous shale to massive biocalcarenite. Section well-exposed and fossil debris well-preserved. See columnar section on p. 183. 49. Dennis Hollow (Valmeyer). S 2, sec. 2, T. 35 N., R. 11 W., Monroe County, Illinois. Valmeyer Quadrangle, 1:24,000; 1954. Ex- posure on north side of Illinois Highway 156, 1.5 mi east of Val- meyer, Illinois; outcrops at two sites (A and B) along road approx- imately 200 yards apart. Outcrop consists of 50.8’ of Keokuk (cherty crinoidal biocalcarenite with thin argillaceous shale interbeds) con- formably overlain by 18.8’ of Warsaw (fossiliferous argillaceous shale with thin biocalcarenitic beds and lenses). Keokuk-Warsaw contact picked on lithic change from crinoidal biocalcarenite to predomi- nantly argillaceous shale. Exposure moderately fresh, containing €x- cellent bryozoan fauna which is both diverse and extremely well- preserved. This section was studied extensively because of the ex- cellent bryozoan fauna. See columnar sections on p. 185. APPENDIX B COLUMNAR SECTIONS FOR LOCALITIES INCLUDED IN THE SPECIES DISTRIBUTION STUDY Arrows mark horizons of samples used for faunal analysis. MISSISSIPPIAN BRYOZOANS: SNYDER EZ gaa uns u 9 5 5 2 E 3 " TII E leis? E D e 2121518 A 131618 2 ul 2|2|z|$ 2 $1 Sele = z be 2 2 æ a [4 2 = ul ui © T a ba = E = z N [^] uw b o mn wn uw [d wn pont Z E v3 ES = < = 513 B o z ul [75] ^s £i = < o ac = i € a o Ll ul 9 uj E pe ul > = ] z fe uy 7 iy m = = a 2 o o e Ija cz m Pd = 2 < a lu > ul = 2H E > Sie A zi Us 2 uu cm = x o Í = $3 ul o o | ojx E ales O rl KEOKUK INDUSTRIAL (Kl) IOWA TERMINAL (IA) SECTION NO. 6 SECTION NO. 5 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 178 Y3BWAN 3 dWVS S3HONI NI SSINADIHL NOI LVW3O3 MVSHVM 303035 (S9sn)saiu3s NVIOINVIIN NVIO9VSO| (S9SI) S31Y3S NVH3A3W IVA YSEWNN 3 1dWVS S3HONI NI SS3NMDIHL NOILVNUOJ MVSHVM (S9SN) S31Y3S NV 39VW'50 (S9SI) S31Y3S NVYSAAW TVA z | SH313W WHITE HOLLOW (WTH) UPPER GRAY'S QUARRY (GQ) SECTION NO. 9 SECTION NO. 7 MISSISSIPPIAN BRYOZOANS: SNYDER 179 D E> no 2d Ei x O $ z D F4 o = a u a |e = 2 o 8181318 3 SEE afasie z „er Coe EN = = SERERE: z -D = = > Sa p < ja m ge zc wj o O ien Los -]u ze ulziz tig =|“1|< ie Ji |o 5 n Zls ee | [ed pare < SS a x ep oA |u z e m >= g fe w -AM*. = oul T ES = <|5 ud ees ls) at wm |W o|*< o 8 9 - 8 3 34 2 HAMILTON=- WARSAW ROADCUT (WR) EE] SECTION NO. 10 GEODE GLEN (GG) SECTION NO. II y NA! N y H38WünN 31dWVvS | MH38WnN 331dWVvS | Y 6 ina Lo. ron gma - m Tee a 13. | 1 a HE 2 o one I - CAE | 5 < = [ t z 2 ES | = = ; o S3HONI NI SS3NX2IHL 4 S S3HONI NI SS3NXOIH.L 2 D ? l 8 4 $ mm o L G du NOILYNYO4 MVSHVM 0303 a NOILVWYO4 IMVSYVM N3T1VS = A m (sosn) S31Y3S NVIO3AVH3W NV39VSO (S9SN)S31Y3S NVIOAWVYAW T (S9S1) S31Y3S NVH3A3W1VA (S9SI) S31Y3S NVYSASW VA | M38WüN 314WVS | PALAEONTOGRAPHICA AMERICANA, NUMBER 57 iL o = O d zn Sins ee Z> S3H9NI NI SSINXOIIHL y B. 5 Ww Mm NOILVWHOJ MVSHVM » pe MISSISSIPPIAN BRYOZOANS: SNYDER 205 EXPLANATION OF PLATE 14 Figure Page Nome Viimiya sibonella; new species ie ee 62 1, 2. Paratype, UI X-6876. FA45. 1. Very shallow tangential section illustrating biserial arrangement of large apertural stylets across branch (arrow), x60; 2. Shallow tangential of zoarium exhibiting pronounced ontogenetic thickening. Note large stylet at proximal-adaxial apertural edge (arrow), x 60. 3-5. Holotype, UI X-6905. FA43. 3. Very shallow to shallow tangential section illustrating apertural placement at site of branch bifurcation (arrow a) and small obverse stylets (arrow b) positioned atop thickened median keel (arrow c), x 40; 4. Shallow to deep tangential section showing typical chamber outline in mid section (arrow a), continuity of granular skeleton across dissepiment (arrow b), and recessed dissepiment relative to obverse branch surface (arrow c), x 20; 5. Greatly enlarged shallow to deep tangential section. Observe chamber outline near reverse-wall budding-site (arrow a), attitudinal relationship of aperture to obverse surface, and small apertural stylets (arrow b), large single apertural stylet developed at distal-adaxial apertural edge (arrow c) and across branch, large single apertural stylet developed at proximal—adaxial apertural edge (arrow d), granular center of keel (arrow e), longitudinal striae along reverse surface (arrow f), and microstylets atop these striae and across dissepiments (arrow g), X 60. 6-10. Minilya paratriserialis, new species Holotype, UI X-6871. 6. Reverse exterior of zoarial fragment exhibiting moderate consistency of fenestrule size and shape (arrow a), microstylet development atop longitudinal striae (arrow b), and site of branch bifurcation (arrow c), x8; 7. Obverse exterior view illustrating general mesh symmetry, variability in fenestrule shape (arrow a) when compared with that of reverse surface, and aperture position (arrow b) at site of branch bifurcation, x8; 8. FH15, transverse section of branches illustrating continuity of granular skeletal layer (arrow) around autozooecial chambers, x 60; 9. FH15, transverse section showing typical opening of aperture (arrow) relative to branch surface, x60; 10. FH15, transverse section showing continuity of granular skeleton with obverse node (arrow a), large apertural stylet (arrow b), peristome (arrow c), and across dissepiment (arrow d), and typical autozooecial chamber shape in mid transverse view (arrow e), X 60. 206 Figure PALAEONTOGRAPHICA AMERICANA, NUMBER 57 EXPLANATION OF PLATE 15 Page 1 DL dd Li LM BOLTON e CR cuo ME C E EE EL T Lo ties M E 2-9. Paratype, UI X-6947. Obverse exterior surface of zoarial fragment illustrating nodes (arrow a) positioned atop keel, longitudinal striae developed across fenestrule (arrow b), intermediate-size stylet developed at proximal-adaxial edge of aperture (arrow c), second stylet at proximal-abaxial edge of aperture (arrow d), and peristome surrounding aperture (arrow e), x25. Holotype, UI X-6871. 2. FH4, mid longitudinal section, obverse to right, showing typical chamber outline (arrow) in mid section, x 70; 3. FH3, mid to shallow longitudinal section showing cross-section of dissepiment across which granular skeleton extends (arrow a), most abaxial edge of aperture (arrow b) opening into fenestrule, adaxial intermediate-size apertural stylet (arrow c), and outer edge of abaxial intermediate-size apertural stylet (arrow d), x 70; 4. FH4, mid shallow longitudinal section, obverse to right, illustrating continuity of thick granular skeleton along reverse wall of chambers (arrow a) and centrally thickened terminal diaphragm (arrow b), x 70; 5. FH3, mid shallow to deep longitudinal section, obverse to right, showing typical mid chamber outline with vestibule development (arrow a), chamber outline in deep longitudinal view (arrow b), and continuity of granular skeleton with reverse microstylets (arrow c), x 70; 6. FH6, very shallow to shallow tangential section illustrating chamber outline in very shallow (arrow a) to shallow (arrow b) tangential view, x70; 7. FH6, very shallow to mid tangential section illustrating intermediate-size apertural stylets developed from abaxial (arrow a) and adaxial (arrow b) edges of the aperture. The adaxial stylet is connected to the vestibular granular layer in some individuals, to the peristome in others; the abaxial stylet is always connected to the peristome. The keel (arrow c) from which nodes (arrow d) extend is also shown, x40; 8. FH5, mid to mid shallow tangential section illustrating typical chamber outline in mid tangential section (arrow a), slight inflection of apertures into fenestrule in mid shallow tangential view (arrow b), and lack of such inflection as section deepens (arrow c), x 40; 9. FHS, deep tangential section showing chamber outline near reverse-wall budding-site (arrow a), and longitudinal striae (arrow b) continuous with inner granular skeletal layer, with reverse microstylets (arrow c) emerging from and continuous with granular skeleton of striae, x 70. 65 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 PLATE 15 PLATE 16 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 MISSISSIPPIAN BRYOZOANS: SNYDER 207 EXPLANATION OF PLATE 16 Figure Page AS LL E E LL SACRE Ner E eC e. ee 68 1-5. Figured specimen, UI X-6816. Large, well-preserved zoarial fragment. 1. Obverse exterior surface exhibiting moderate onto- genetic thickening near proximal end of zoarium (arrow a) and slight ontogenetic thickening toward more distal end of zoarium (arrow b), Note terminal diaphragms (arrow c) capping apertures near proximal end of zoarium, which are absent toward more distal end of fragment (arrow d), x8; 2. Reverse exterior surface illustrating similar ontogenetic thickening toward proximal end of zoarium and thinning toward more distal end. Note longitudinal striae (arrow) evident at most distal end of zoarium but covered by lamellar skeleton toward proximal end of zoarium due to ontogenetic thickening of lamellar skeleton, x8; 3. F133, deep longitudinal section, obverse to right, showing typical chamber shape near middle of branch (arrow a) and granular skeletal layer continuous with obverse nodes (arrow b), and microstylets (arrow c), x 70; 4. Obverse exterior surface showing aperture placement at site of branch bifurcation (arrow a), small stylet placement across obverse branch surface (arrow b), nodes (arrow c), longitudinal striae across dissepiments (arrow d), small stylets forming as extensions of peristome (arrow e), and attitudinal relationship of aperture to plane of obverse zoarial surface. Note slight inflection of apertures into fenestrule, x 30; 5. Reverse exterior surface illustrating macrostylet (arrow a) and microstylet (arrow b) development along reverse zoarial surface, and general fenestrule shape as viewed from reverse surface. Note placement of macrostylets near sites of branch bifurcation, x 30. 6. Figured specimen, UI X-6817. FI53, transverse section showing typical general branch outline and continuity of thin granular layer encompassing autozooecial chambers and continuous with reverse longitudinal striae (arrow), x 70. 7, 8. Figured specimen, UI X-6810. FI69. 7. Transverse section showing major zooecial characteristics in this view including inferior hemiseptal development (arrow a), nodes (arrow b), terminal diaphragm (arrow c) capping aperture that exhibits typical attitudinal relationship to plane of obverse surface, granular skeleton of peristome (arrow d) continuous with internal granular skeletal layer around autozooecia, and granular skeletal layer (arrow e) extending between branches across dissepiment, x 70; 8. Mid longi- tudinal section, obverse to right, showing granular skeletal layer continuous around autozooecial chamber (arrow a), typical autozooecial chamber shape in mid tangential view (arrow b), inferior hemiseptum positioned on proximal side of distal lateral chamber wall (arrow c) about one-third of the way toward obverse surface, with hemiseptum increasing in length as section shallows (arrow d), short superior hemiseptum (arrow e) at proximal edge of vestibule, and terminal diaphragm capping aperture (arrow f), x 70. 208 Figure PALAEONTOGRAPHICA AMERICANA, NUMBER 57 EXPLANATION OF PLATE 17 Ir Exfenestella exrena (Uil. 890). 8. ous as ye ep ae tor vote Re ee a Eee re eto delit ken. 1,2. Figured specimen, UI X-6810. 1. Deep tangential section illustrating microstylet (arrow a) and macrostylet (arrow b) devel- opment, x 70; 2. shallow to mid shallow longitudinal section, obverse to right, catching lateral edge of autozooecial chambers and showing terminal diaphragm capping aperture (arrow a), and microstylet (arrow b) continuous with inner granular skeleton, x70. . Figured specimen, UI X-6749. Large, moderately ontogenetically thickened zoarial fragment. 3. TD90, deep longitudinal section, obverse to right, showing typical chamber outline in deep longitudinal view (arrow a), reverse macrostylet (arrow b), and obverse node (arrow c), both continuous with granular skeleton surrounding autozooecial chamber, x40; 5. TD91, shallow longitudinal section, obverse to right, showing typical chamber outline in this view and extension of apertures onto dissepiments (arrow), x40; 6. TD94, shallow to mid tangential section. Illustrated is chamber outline at site of branch bifurcation (arrow a) and continuity of granular skeleton across dissepiment (arrow b), x40. . Figured specimen, UI X-6817. FI57, mid to very shallow tangential section illustrating nodes (arrow a) and small obverse stylets (arrow b) positioned across obverse branch surface, aperture shape and positioning relative to plane of obverse surface (arrow c), complete peristome (arrow d) and small stylets that form as extensions of peristome (arrow e). Although an extension of the axial wall toward the obverse surface is observed (arrow f), a true keel is lacking, x 70. . Figured specimen, UI X-6768. FG32, mid shallow to deep tangential section showing typical chamber outline in mid tangential view (arrow a) and inferior hemiseptum placement diagonally across autozooecial chamber (arrow b), also shown is superior hemiseptum placement at proximal peristomal edge (arrow c) giving bilobate appearance to chamber outline, and chamber outline near reverse-wall budding-site (arrow d), x 70. PALAEONTOGRAPHICA AMERICANA, NUMBER 57 PLATE 17 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 PLATE 18 MISSISSIPPIAN BRYOZOANS: SNYDER 209 EXPLANATION OF PLATE 18 Figure Page AIDA OACI Se. RODA T aan e N Eu ce sea ES 68 Figured specimen, UI X-7021. FM22, shallow to mid tangential section of zoarial fragment exhibiting little ontogenetic thickening of lamellar skeletal layer (arrow), x 40. 2-9. B tella g I IRIEWESDEGLESE ics e ER RUE EE CONDO Pr MEIN ae 73 2-4. Paratype, UI X-7016. Large, well-preserved zoarial fragment exhibiting slight ontogenetic thickening of lamellar skeletal layer. 2. Obverse exterior surface. Observe presence of either third row of autozooecia at site of branch bifurcation (arrow | a) or three rows for moderate to pronounced distances proximal to sites of branch bifurcation (arrow b) and recessed dissepiments (arrow c), relative to plane of obverse zoarial surface, x 8; 3. Reverse exterior surface illustrating longitudinal striae atop which are positioned rows of small, variable-size microstylets (arrow). Note pronounced thickening of branch proximal and thinning distal to sites of branch bifurcation, and variable fenestrule size and shape in this species, x 8; 4. Greatly enlarged obverse exterior surface illustrating large, well-developed and regularly positioned apertural stylets (arrow a) surrounding essentially circular aperture capped in this case by centrally thickened terminal diaphragm; also shown is well-developed ropy keel (arrow b), atop which develop small stylets (arrow c) positioned between large nodes (arrow d) and along edge of keel, x25. 5,6, 8, 9. Holotype, UI X-6779. Large moderately ontogenetically thickened zoarial fragment exhibiting good preservation of interior detail. 5. Obverse exterior surface illustrating fusion of apertural stylets around aperture (arrow a), overgrowth of aperture adaxial edge by keel (arrow b) and thickened keel (arrow c) in this zoarial fragment, x25; 6. FA18, very shallow tangential section. Note typical attitudinal relationship of aperture to plane of obverse surface and well-developed apertural stylets (arrow a) surrounding apertural opening, well-developed node (arrow b) atop keel and small stylets along obverse surface (arrow c), x60; 8. FA14, transverse section illustrating terminal diaphragm development (arrow a), node (arrow b), and apertural stylet (arrow c) in view exhibiting typical attitudinal relationship of aperture to obverse surface, x 40; 9. FA11, transverse section of single branch showing reverse microstylets (arrow) with core of granular skeleton, x40. 7. Paratype, UI X-6796. Obverse exterior surface of highly ontogenetically thickened zoarial fragment. Note pronounced thickening of keel (arrow) almost completely overgrowing apertural openings, x8. 210 Figure 1-10. B t PALAEONTOGRAPHICA AMERICANA, NUMBER 57 EXPLANATION OF PLATE 19 ll CERIN OY CADIS Ol e NENNEN A Mie, UOS oir v MEER ON CU USO V od ce 1-5, 10. Paratype, UI X-7016. 1. PA9, very shallow longitudinal section, obverse to right, illustrating aperture opening onto edge of and continuity of granular skeleton across dissepiment (arrow a) and abaxial edge of aperture (arrow b) where it extends into fenestrule, x 40; 2. PA9, shallow to mid longitudinal section, obverse to right, showing centrally thickened terminal diaphragm (arrow a) and “brown bodies" (arrow b) often positioned behind these diaphragms, x 40; 3. PA2, mid longitudinal section, obverse to right, illustrating typical chamber outline and continuity of granular skeleton around autozooecial chambers (arrow), x 40; 4. PAl, mid longitudinal section obverse to right. Observe typical chamber outline in this view (arrow a) showing low reverse-wall budding-angle typical of this species; also shown are reverse microstylets (arrow b) continuous with granular skeleton, x40; 5. PAl, mid to deep longitudinal section, obverse to right, showing chamber outline in deep view (arrow a) and continuity of large nodes (arrow b) with internal granular skeletal layer, x 40; 10. PAS, shallow to deep tangential section showing continuity of granular skeleton across dissepiment (arrow a), variation of chamber outline in mid tangential view from that of a parallelogram (arrow b) to that of a rectangle (arrow c), inflections in fenestrule outline near obverse surface due to projections of apertures into fenestrule (arrow d) and lack of such inflections in mid to deep tangential view (arrow e), x 20. . Holotype, UI X-6779. 6. FA15, transverse section showing development of apertural stylets (arrow) which, when observed in vestibule, are inflected into inner vestibular area causing a restriction in the vestibular opening, x40; 7. FA18, very shallow tangential section illustrating keel development (arrow a) betwen large stellate nodes, and small stylets occurring between nodes (arrow b), x60; 8. FA9, shallow tangential section showing typical node and aperture arrangement along branch and at site of branch bifurcation (arrow) where, in this case, the third aperture is shared between both diverging branches, x 20; 9. FA18, shallow to mid tangential section showing typical chamber outline in mid section view and site of branch bifurcation (arrow), x 20. PALAEONTOGRAPHICA AMERICANA, NUMBER 57 PLATE 19 PLATE 20 NUMBER 57 > PALAEONTOGRAPHICA AMERICANA MISSISSIPPIAN BRYOZOANS: SNYDER 214 EXPLANATION OF PLATE 20 Figure Page IS Banastella-muensburguinew. SPECIES a O o la ne ee le ER EIU ES 73 Paratype, UI X-7016. PA5, deep tangential section illustrating autozooecial chamber outline near reverse-wall budding-site (arrow a), longitudinal striae (arrow b) developing as extensions of reverse granular autozooecial wall and small microstylets (arrow c) which form as projections from these striae, x 40. B llacio u ae (Walz d 590) E e ack cere dn ee Sidra ee ne fons ae a PME Ta. Figured specimen, UI X-6720. Large, well-preserved zoarial fragment exhibiting moderate ontogenetic thickening. 2. Obverse exterior surface illustrating centrally thickened terminal diaphragm capping aperture (arrow a), intermediate-size stellate nodes (arrow b), peristome (arrow c) surrounding pronounced inflection of apertures into fenestrule opening (arrow d), and site of branch bifurcation { (arrow e) showing greatly widened three rows across branch proximal and narrowed two rows distal to site, x 20; 3. Reverse exterior surface showing typical ovate shape of fenestrule in this species (arrow a), large zoarial support developed as extension of reverse zoarial surface (arrow b) and longitudinal striae (arrow c) atop which are positioned rows of microstylets, x 8; 4. TX40, transverse section illustrating thickening of lamellar skeletal layer and typical attitudinal relationship of aperture to plane of obverse surface (arrow), x 40; 5. TX38, transverse section. Note typical branch outline in cross-section, terminal diaphragm (arrow a) and attitudinal relationship of aperture to obverse surface, and microstylets (arrow b) which connect with granular skeleton of longitudinal striae (arrow c), x 70; 6. TX40, transverse section showing continuity of nodes (arrow a) and peristome (arrow b) with granular skeleton as well as continuity of granular skeleton between branches (arrow c) across dissepiment, x 70; 7. TX39, shallow to mid shallow longitudinal section, obverse to right, illustrating apertural stylets (arrow a), stylets developed along lateral edge of branch (arrow b) and thickened area on reverse surface (arrow c) corresponding to occurrence of dissepiment, x70; 8. TX40, mid longitudinal section, obverse to right, showing typical chamber outline in this view (arrow a), and continuity of apertural stylets (arrow b) and microstylets (arrow c) with internal granular skeleton, x70; 9. TX40, mid longitudinal section, obverse to right, showing variable chamber outline in this view (arrow), x 40; 10. TX40, shallow to mid longitudinal section, obverse to right, showing apertural edge extending into fenestrule (arrow a) and continuity of granular skeleton across dissepiment (arrow b), x40. 2-10. 212 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 EXPLANATION OF PLATE 21 Figure Page tab. Patel aa (Ole 1990) a HER e RA I T eeu eu cre to ae cae en th Wil Figured specimen, UI X-6720. 1. TX43, mid longitudinal section, obverse to right, illustrating continuity of granular skeleton along reverse wall (arrow a), along chamber lateral walls (arrow b) and in center of nodes (arrow c). Note typical chamber outline in mid longitudinal view (arrow d), x 70; 2. TX49, shallow to mid tangential section illustrating typical chamber outline in mid tangential (arrow a) and shallow tangential (arrow b) view. Observe continuity of granular skeleton across dissepiments (arrow c), typical fenestrule shape (arrow d) and overall chamber arrangement and symmetry, x 40; 3. TX45, deep tangential section showing chamber outline near reverse-wall budding-site (arrow a) and microstylets (arrow b) occurring in rows along reverse branch surface, developing as extensions of longitudinal striae (arrow c), x 70; 4. TX49, shallow tangential section. Observe typical attitudinal relationship of aperture to obverse zoarial surface (arrow a), apertural stylets (arrow b), aperture inflection into fenestrule opening near obverse surface (arrow c), and stellate node appearance (arrow d) as well as relatively close placement of nodes, x 70; 5. TX49, shallow to mid tangential section showing typical symmetry and site of branch bifurcation (arrow), x 40; 6. TX45, mid to deep tangential section illustrating pronounced thickening of lamellar skeleton associated with site of zoarial support development (arrow a). Observe partial plugging of fenestrule (arrow b) along reverse zoarial surface associated with lamellar skeletal thickening, x40. PLATE 21 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 PLATE 22 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 | MISSISSIPPIAN BRYOZOANS: SNYDER 213 | EXPLANATION OF PLATE 22 | Figure Page | l=11. Banastella mediocreforma, new SPECIES u nen ee a E e Ne woes a a ex eed seo eee e eats Tees 79 1-3, 6-11. Holotype, UI X-6717. Large, well-preserved zoarial fragment exhibiting moderate ontogenetic thickening. 1. Obverse exterior surface illustrating typical autozooecial aperture shape and attitudinal relationship to plane of obverse surface (arrow a), peristome surrounding aperture (arrow b) formed from fusion of apertural stylets and slight extension of aperture into fenestrule margin, nodes (arrow c) widely spaced along middle of obverse branch surface, small stylets (arrow d) across obverse surface and aperture placement at site of branch bifurcation (arrow e), X 30; 2. Reverse exterior surface showing fenestrules (arrow a) that exhibit irregularity in size and shape, small microstylets across reverse branch | surface (arrow b), and thickening proximal and thinning distal to sites of branch bifurcation (arrow c), x 12; 3. Obverse exterior surface showing typically moderately irregular mesh pattern, keel (arrow a) and apertures partially to completely overgrown by lamellar skeleton (arrow b), x12; 6. TX1, transverse section showing typical branch outline in cross- section and node (arrow) continuous with granular skeleton, x 70; 7. TX7, deep to mid longitudinal section, obverse to right, showing typical chamber outline in deep longitudinal view (arrow), x 70; 8. TX5, shallow mid longitudinal section, obverse to right, showing lamellar skeleton partially overgrowing aperture (arrow a) and reverse microstylets (arrow b) in continuity with internal granular skeletal layer, x 70; 9. TX7, mid longitudinal section, obverse to right, illustrating typical autozooecial chamber outline (arrow) associated with low reverse-wall budding-angle, x40; 10. TX5, transverse section illustrating branch that is rounded in cross-section, typical attitudinal relationship of aperture (arrow a) to plane of obverse surface, granular skeleton continuous around autozooecial chambers, with reverse longitudinal striae (arrow b) and across dissepiments (arrow c). Note moderate thickening of lamellar skeletal layer (arrow d), x70; 11. 1X5, | transverse section of widened branch near site of branch bifurcation illustrating apertural stylets (arrow) at edge of aperture, x 70. 4, 5. Paratype, UI X-6917. PI92. 4. Shallow to mid longitudinal section, obverse to right, illustrating typical attitudinal relationship of aperture to obverse surface (arrow a), apertural stylets (arrow b), and granular skeleton extending across dissepiments between branches (arrow c), x 70; 5. Mid longitudinal section, obverse to right, showing continuity of granular skeleton along reverse chamber wall (arrow a), around autozooecial chambers, and with obverse nodes (arrow b), x40. PALAEONTOGRAPHICA AMERICANA, NUMBER 57 | EXPLANATION OF PLATE 23 | Figure Page 1-6. Bünweliy-mediscroforua; Hew Species o. Tu TAT CUL Were do ed e NE OF DM CEN NO UR a TU Y IRR codes Cd 79 1, 3-6. Holotype, UI X-6717. 1. TX13, mid to shallow tangential section showing three rows of autozooecia across branch surface proximal to site of branch bifurcation (arrow a) and slight inflection of apertures into fenestrule in mid shallow tangential view (arrow b), x25; 3. TX13, shallow tangential section illustrating apertural stylets (arrow a) that fuse to become the peristome (arrow b), and median keel (arrow c) atop which are located small stylets (arrow d), x 70; 4. TX1, transverse section showing typical cross-section of autozooecial chamber (arrow), x70; 5. TX13, shallow to deep tangential section showing chamber outline in mid tangential view (arrow a), mid shallow tangential view (arrow b) and near reverse-wall budding-site (arrow c). Note longitudinal striae (arrow d) from which microstylets (arrow e) originate, x25; 6. TX50, shallow tangential section showing inflection of autozooecial apertures into fenestrule (arrow a), well-developed median keel (arrow b) atop which are positioned widely spaced stellate nodes (arrow c), x40. 2. Paratype, UI X-6917. PI94, shallow to deep tangential section of zoarial fragment exhibiting slight ontogenetic thickening. Observe lack of inflection into fenestrule outline by apertures in mid tangential section (arrow), x 20. PLATE 23 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 PLATE 24 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 MISSISSIPPIAN BRYOZOANS: SNYDER 215 —— e EXPLANATION OF PLATE 24 j Figure Page \ A ee en a ed 81 L Hypotype, UI X-7015. Large, well-preserved zoarial fragment exhibiting slight ontogenetic thickening. 1. Obverse exterior surface P illustrating typical mesh symmetry. Observe either third row at site of branch bifurcation (arrow a) or three rows for moderate distance proximal to site of branch bifurcation (arrow b), x8; 2. Enlarged obverse exterior surface showing ring of apertural stylets f partially fused to become peristome (arrow a), site of branch bifurcation (arrow b), and median keel (arrow c) atop which are positioned well-developed nodes (arrow d), x 20; 3. WR56, transverse section showing well-developed node (arrow) continuous with interior granular skeletal material, x70; 4. WR56, transverse section illustrating typical attitudinal relationship of aperture to plane of obverse surface (arrow a), continuity of granular skeletal layer across dissepiment (arrow b) and longitudinal ridge development ) across dissepiment obverse surface (arrow c), X 70; 5. Enlarged reverse exterior surface showing variability in fenestrule shape (arrow } a), microstylets (arrow b) developing as extensions of longitudinal striae, and microstylets (arrow c) developed across dissepiments, i x 20; 6. WR53, transverse section showing continuity of granular skeleton with stylets and subsequently with peristome surrounding | aperture (arrow a), and inception of dissepiment as extension of longitudinal striae at lateral edge of branch (arrow b), x70; 7. ! WRS1, mid shallow to shallow longitudinal section, obverse to right, showing narrow longitudinal outline of autozooecial chamber | (arrow), x70; 8. WR51, mid to shallow longitudinal section, obverse to right, showing continuity of granular skeleton across dissepiment (arrow a) and elongate typical autozooecial chamber in mid longitudinal section with shape altered by fracturing of chamber lateral walls (arrow b),x40; 9. WR57, mid longitudinal section, obverse to right, illustrating granular skeleton surrounding \ autozooecial chambers and continuous with reverse microstylets (arrow a) and obverse nodes (arrow b), x 70; 10. Enlarged obverse exterior view. Note slight to moderate extension of aperture into fenestrule (arrow a), sinuous keel (arrow b), nodes developing as extensions of keel (arrow c), barlike longitudinal ridges across dissepiments (arrow d), and small obverse stylets (arrow e), x 20. 1 | 216 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 EXPLANATION OF PLATE 25 Figure Page 1-8. Dane ibis A eee Ceres ie buck Ple v Bee eum merece Ru 81 Hypotype, UI X-7015. 1. WR64, very shallow to shallow tangential section showing keel (arrow a), nodes (arrow b) developed atop D keel, small obverse stylets (arrow c), typical aperture shape and orientation to plane of obverse surface (arrow d), apertural stylets | (arrow e), and fusion of these stylets to become the peristome (arrow f), x70; 2. WR63, mid to deep tangential section showing autozooecial chamber shape near reverse-wall budding-site (arrow a), granular skeletal composition of longitudinal striae extending along reverse chamber surface (arrow b), microstylets (arrow c) developing atop the longitudinal striae and across disepiments (arrow d) along reverse zoarial surface, x 40; 3. WR53, transverse section of branch proximal to site of branch bifurcation, x 70; 4. Reverse exterior surface illustrating longitudinal striae and site of branch bifurcation (arrow), x 8; 5. WR63, mid to deep mid tangential section. Observe continuity of granular skeleton across dissepiments (arrow a) and lack of aperture extension into fenestrule (arrow b) in this i view, x40; 6. WR64, shallow tangential section showing aperture extending onto edge of dissepiment (arrow a) and thin axial ridge (arrow b) along obverse surface, x 40; 7. WR63, mid shallow tangential section showing typical autozooecial chamber outline in this view (arrow), x40; 8. WR64, shallow to mid tangential section showing chamber outline in mid tangential view (arrow), x40. PLATE 25 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 PLATE 26 i MISSISSIPPIAN BRYOZOANS: SNYDER 217 EXPLANATION OF PLATE 26 Figure Page LIO ebanastellaibisercata (Ulrich, 13590) teen green ee. ECT DEDE NE 83 Figured specimen, UI X-6915. 1. Obverse exterior of zoarial fragment illustrating three rows of apertures across branch surface developed for pronounced distances proximal to site of branch bifurcation (arrow) and polyporid-like appearance ofzoarium exterior, x 8; 2. Reverse exterior of zoarial fragment showing longitudinal striae (arrow a) atop which occur rows of small microstylets, site of branch bifurcation (arrow b) and typical fenestrule shape in reverse view (arrow c), x8; 3. High magnification obverse exterior | view illustrating typical attitudinal relationship of aperture (arrow a) to plane of obverse surface, peristome (arrow b), intermittent and anastomosing keel (arrow c), stellate node (arrow d), and longitudinal striae atop obverse dissepiment surface (arrow e), x25; | 4. PO22, mid longitudinal section, obverse to left, showing continuity of granular skeleton (arrow) around autozooecial chambers, x 70; 5. PO26, transverse section showing centrally thickened terminal diaphragm capping aperture oriented in typical fashion to plane of obverse surface (arrow a), and longitudinal striae (arrow b) continuous with internal granular skeletal layer and nodes (arrow €), and characteristic chamber outline in mid transverse view (arrow d), x 70; 6. PO20, shallow to mid longitudinal section, obverse to left, showing terminal diaphragm (arrow a) and typical chamber outline in mid tangential section (arrow b) illustrating low budding-angle of reverse wall, x 70; 7. PO22, shallow to mid longitudinal section, obverse to left, illustrating typical chamber outline in mid longitudinal view and short vestibule with superior hemiseptum (arrow a), continuity of granular skeletal layer with reverse microstylets (arrow b) and across dissepiments (arrow c), x 70; 8. PO27, shallow to mid tangential section showing typical chamber outline in mid section view (arrow a) and continuity of granular skeleton across dissepiment (arrow b). Note typical zoarial surficial view in tangential section, x 35; 9. PO31, very shallow tangential section. Observe typical aperture outline (arrow a), peristome (arrow b), keel (arrow c), and node (arrow d) developed at proximal edge of aperture, also very slight superior hemiseptum present at inner vestibule proximal edge (arrow e), x 70; 10. PO29, shallow to deep tangential section showing typical chamber outline in mid tangential view (arrow a), site of branch bifurcation (arrow b), chamber outline near reverse-wall budding-site (arrow c), microstylets developed as extensions of longitudinal striae (arrow d) and across dissepiment surface (arrow e), x 35. 218 Figure PALAEONTOGRAPHICA AMERICANA, NUMBER 57 EXPLANATION OF PLATE 27 l. Banastenn:Diseriann ce ltich,. 1890)... a ee Be ESE v se c CH ERES Figured specimen, UI X-6915. PO29, shallow to mid tangential section. Observe short superior hemiseptum present at proximal aperture edge (arrow a) and typical autozooecial chamber outline near obverse surface (arrow b), x70. SV. STC REPETI, TN AR A Ree PES. Decore A II e CI REO MR Eee cvm pee PO HS ET pas 3, 7-10. Holotype, UI X-6793. Obverse exterior surface of large, well-preserved zoarial fragment showing apertures surrounded by peristomes (arrow a) which apparently develop from fusion of apertural stylets, aperture position at site of branch bifurcation (arrow b), keel (arrow c), nodes (arrow d) positioned atop keel, ornamentation across dissepiment surface (arrow e) and projection of aperture into fenestrule opening (arrow f), x8. Paratype, UI X-6781. 3. Reverse exterior surface showing longitudinal striae (arrow a) atop which develop microstylets (arrow b). Note site of branch bifurcation (arrow c), x8; 7. FA58, shallow longitudinal section, obverse to left, showing slight aperture extension into fenestrule at branch lateral edge (arrow a) and continuity of granular skeleton across dissepiment (arrow b), x 70; 8. FA58, shallow to mid shallow longitudinal section, obverse to left, illustrating typical chamber outline in mid shallow section (arrow) x 40; 9. FA66, mid to mid shallow longitudinal section, obverse to left, illustrating terminal diaphragm (arrow a) and mid longitudinal section with low reverse-wall budding-angle (arrow b), x40; 10. FA66, mid deep to deep longitudinal section, obverse to left, showing typical chamber outline in deep longitudinal view (arrow a) and apertural stylet development at adaxial aperture edge (arrow b), x 70. . Paratype, UI X-6782. 4. FA63, transverse section showing apertural stylet (arrow a) at edge of aperture exhibiting typical attitudinal relationship to plane of obverse surface, longitudinal striae continuous with inner granular skeleton (arrow b), and part of longitudinal ridge across dissepiment surface (arrow c), x 70; 5. FA57, transverse section showing continuity of granular skeleton with obverse nodes and keel (arrow a) and typical circular cross-section of branch (arrow b), x 70. . Paratype, UI X-6783. FA65, mid shallow tangential section illustrating well-developed longitudinal ridge (arrow) extending between branches atop dissepiment, x40. PALAEONTOGRAPHICA AMERICANA, NUMBER 57 PLATE 27 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 ER Ez PLATE 28 MISSISSIPPIAN BRYOZOANS: SNYDER 219 EXPLANATION OF PLATE 28 Figure Page 1-5. Banastella doloa new SPE CIOS Gee visi den ee NEUEN. No fd M NO M E BER EE Qu. Sates 86 Holotype, UI X-6793. Large zoarial fragment exhibiting slight ontogenetic thickening. 1. FA73, shallow to deep tangential section ilustrating chamber outline near reverse-wall budding-site (arrow a), reverse longitudinal striae (arrow b) atop which develop | microstylets (arrow c) and recessed dissepiment relative to plane of reverse surface (arrow d), x 40; 2. FA51, mid shallow tangential Section showing typical chamber outline (arrow a) in this view and at site of branch bifurcation (arrow b), slight inflection of apertural abaxial edge into fenestrule (arrow c) and short superior hemiseptum (arrow d) at proximal vestibular edge, x 40; 3. FA65, shallow tangential section. Note aperture location at site of branch bifurcation (arrow a) and autozooecial chamber outline as section slightly deepens (arrow b), x 40; 4. FA71, shallow to deep tangential section illustrating typical autozooecial chamber outline in mid tangential View (arrow a), typical aperture shape and attitudinal relationship to plane of obverse surface (arrow b), node (arrow c), continuity of granular skeleton across dissepiment (arrow d) and lack of apertural inflection into fenestrule (arrow e), x 20; 5. FA65, enlarged i shallow tangential view showing aperture surrounded by stylets (arrow a) at edge of dissepiment, fusing of these stylets in slightly deeper section to form peristome (arrow b), stylets along obverse branch surface (arrow c), ridge atop dissepiment formed from granular skeleton (arrow d) and thickened keel along middle of branch (arrow e), x 70. 220 Figure PALAEONTOGRAPHICA AMERICANA, NUMBER 57 EXPLANATION OF PLATE 29 Li Cubienesivila rudis (Ulrick 1890) > o o ae nur te ner Ek eH erates prions een ee en le eec A 1-4, 9-11. Figured specimen, UI X-6752. Large, well-preserved zoarial fragment exhibiting pronounced ontogenetic thickening. 1. Reverse exterior surface. Observe fenestrules overgrown by lamellar skeleton (arrow a) near proximal end of zoarium and those not overgrown (arrow b) toward more distal end of zoarium, zoarial supports developed from reverse surface (arrow c), and initial site of zoarial development (arrow d), x4; 2. Obverse exterior surface illustrating pronounced ontogenetic thickening of lamellar skeleton near proximal end of zoarium covering autozooecial apertures (arrow a) when compared to more distal end of zoarial fragment where apertures remain uncovered (arrow b), zoarial supports developed at lateral mesh edge (arrow c), and initial site of zoarial development (arrow d), x4; 3. Obverse exterior surface near proximal end of zoarium showing pronounced thickening of keel (arrow a), most autozooecial apertures covered by lamellar skeleton (arrow b), and increased node diameter (arrow c), all resulting from ontogenetic thickening, x 8; 4. Obverse exterior toward more distal end of zoarium showing apertures not covered by lamellar skeleton (arrow a) and less keel and nodal thickening (arrow b), x8; 9. TA94, deep to mid longitudinal section, obverse to right, showing macrostylets (arrow a), nodes (arrow b), small obverse stylets (arrow c), microstylets (arrow d) all in continuity with granular skeletal layer (arrow e) surrounding autozooecial chambers, x 40; 10. TA3, transverse section illustrating typical chamber shape and attitudinal relationship of aperture to plane of obverse surface (arrow a), characteristic chamber outline in mid transverse view (arrow b), and intermediate thickening of lamellar skeletal layer, x 40; 11. TA6, transverse section showing typical branch profile in cross-sectional view, branch spacing, and centrally thickened terminal diaphragm (arrow), x40. . Figured specimen, UI X-6902. Zoarial fragment exhibiting slight to moderate ontogenetic thickening. 5. Obverse exterior illustrating slight keel and nodal development (arrow a) as well as apertures not covered by lamellar skeleton, and site of branch bifurcation (arrow b), x8; 6. Reverse exterior surface illustrating variability in fenestrule size and shape and macrostylets (arrow) typically positioned at or near site of branch-dissepiment junction, x8; 7. Greatly enlarged obverse exterior surface view. Note aperture shape and attitudinal relationship to plane of obverse surface (arrow a), centrally thickened terminal diaphragm capping aperture (arrow b), peristome (arrow c), nodes (arrow d) atop keel, obverse stylets (arrow e) and median ridge across dissepiment (arrow f), x 25. . Figured specimen, UI X-6900. EF12, transverse section of moderately ontogenetically thickened zoarial fragment showing granular skeletal layer continuous around autozooecial chambers and with longitudinal striae (arrow a), microstylets (arrow b), obverse node (arrow c), across dissepiment (arrow d) and with apertural stylets (arrow e), x 70. PLATE 29 NUMBER 57 d PALAEONTOGRAPHICA AMERICANA PALAEONTOGRAPHICA AMERICANA, NUMBER 57 PLATE 30 Veer AT MISSISSIPPIAN BRYOZOANS: SNYDER 221 EXPLANATION OF PLATE 30 Figure Page 7 @ubıfonestellaanudisstQluch 1890) ee are ews er es 90 1, 4, 6. Figured specimen, UI X-6752. 1. TA4, shallow to mid longitudinal section, obverse to left, showing centrally thickened terminal diaphragm (arrow a) capping autozooecial chamber with extremely long vestibule (arrow b) developed due to thickened lamellar skeletal layer, microstylets (arrow c) continuous with granular skeleton extending to reverse exterior surface (arrow d) and obverse node (arrow e), x40; 4. TA12, very shallow tangential section showing typical features including peristome surrounding aperture (arrow a), thick keel (arrow b), slightly stellate node (arrow c), obverse stylet | (arrow d), and similar stylets across dissepiment (arrow e), and site of branch bifurcation (arrow f), x 40; 6. TA97, shallow to deep tangential section. Note nearly complete plugging of fenestrule by lamellar skeleton near reverse surface (arrow a), pronounced inflection of aperture into fenestrule on obverse surface (arrow b), shallow tangential chamber outline (arrow c) and typical aperture outline (arrow d), continuity of granular skeleton across dissepiment (arrow e) and mid tangential view at site of branch bifurcation (arrow f), x20. 2,3, 5, 7. Figured specimen, UI X-6900. 2. EF9, mid to deep longitudinal section, obverse to left, showing typical chamber outline in deep section (arrow a) and granular skeleton continuous with reverse macrostylets (arrow b) and obverse nodes (arrow N €), x70; 3. EF96, very shallow to mid tangential section. Observe nodes (arrow a) positioned atop well-developed keel (arrow b), autozooecial chamber outline in shallow (arrow c) and mid (arrow d) tangential view, and lack of aperture extension into fenestrule opening in mid tangential view (arrow e), x 20; 5. EF14, very shallow to mid longitudinal section, obverse to left. Note slight extension of aperture onto lateral edge of dissepiment (arrow a) and into fenestrule opening (arrow b), typical chamber outline in mid longitudinal view (arrow c), and granular skeleton continuous across dissepiment (arrow d), x40; 7. EF96, deep tangential section showing autozooecial chamber outline near reverse-wall budding-site (arrow a), longitudinal striae (arrow b) from which develop microstylets (arrow c), and macrostylets typically associated with sites of branch-dissepiment junction (arrow d), x 40. 222, Figure PALAEONTOGRAPHICA AMERICANA, NUMBER 57 EXPLANATION OF PLATE 31 EAR GH ep LT A ee RE 1, 3, 6-8, 10-12. 4,9. Paratype, UI X-6708. Large, well-preserved moderately ontogenetically thickened zoarial fragment. 1. Obverse exterior surface illustrating typical mesh symmetry, x 8; 3. Reverse exterior surface showing variation in fenestrule size and shape in this species (arrows a and b), longitudinal striae atop which rows of microstylets develop (arrow c), and site of branch bifurcation (arrow d), x8; 6. FL36, transverse section of branch illustrating typical chamber and branch profile in cross-sectional view, x 70; 7. FL36, deep to mid longitudinal section, obverse to left, showing continuity of granular skeleton around autozooecial chambers (arrow a) and with reverse microstylets (arrow b), typical chamber outline in deep longitudinal view (arrow c), and adaxial apertural stylets (arrow d), x 70; 8. FL34, deep to mid longitudinal section, obverse to left, showing obverse nodal development (arrow a), obverse stylets (arrow b) and typical chamber outline in mid longitudinal view (arrow c), x70; 10. FL36, transverse section illustrating longitudinal striae (arrow a) and microstylets (arrow b) continuous with inner granular skeleton, and terminal diaphragm over aperture (arrow c) exhibiting typical attitudinal relationship of aperture to plane of obverse surface, x70; 11. FL34, transverse section showing typical branch outline with well-developed node (arrow) in continuity with interior granular skeleton, x 70; 12. FL34, shallow longitudinal section, obverse to left, showing typical chamber outline in shallow view (arrow a) and obverse stylet (arrow b), x 70. . Paratype, UI X-6712. High magnification of obverse exterior surface showing apertures (arrow a) without terminal diaphragm development, thickened ridge across dissepiment (arrow b), aperture positioning at site of branch bifurcation (arrow c) and thickened keel (arrow d), x 30. 5. Reverse exterior surface with development of reverse zoarial support (arrow), x8. Holotype, UI X-6709. Large, slightly ontogenetically thickened zoarial fragment. 4. High magnification of obverse exterior surface, illustrating aperture capped by centrally thickened terminal diaphragm (arrow a), nodes (arrow b), obverse stylets (arrow c), keel (arrow d), and site of branch bifurcation (arrow e), x 20; 9. FL46, shallow to mid longitudinal section, obverse to left, illustrating centrally thickened terminal diaphragm (arrow a) and apertural stylet (arrow b) continuous with interior granular skeleton, x 70. PLATE 31 PLATE 32 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 MISSISSIPPIAN BRYOZOANS: SNYDER 223 EXPLANATION OF PLATE 32 Figure Page 1-6. Gubifenestelluiusitatami WS DECIES en eene s I d mae ehe tn qot ERI eaten D d osse Regs ead 92 1. Paratype, UI X-6708. FL34, very shallow to shallow longitudinal section, obverse to left, illustrating transverse view of dis- sepiment with ridge developed on obverse surface (arrow a) and thickened lamellar skeleton on reverse (arrow b), x 70. 2-6. Holotype, UI X-6709. 2. FL48, shallow to deep tangential section. Observe variable chamber outline in mid tangential view at site of branch bifurcation (arrow a) when compared to typical chamber outline in mid tangential view along branch (arrow b), | chamber outline near reverse-wall budding-site (arrow c) and longitudinal striae along reverse wall (arrow d), x40; 3. FL47, very shallow to mid tangential section illustrating well-developed keel (arrow a), nodes developed atop keel (arrow b), and recessed dissepiment relative to plane of obverse surface (arrow c), x 40; 4. FL48, mid to shallow tangential section showing terminal diaphragm (arrow a) across aperture of chamber exhibiting typical view in shallow chamber outline, apertural stylets (arrow b), chamber outline in mid tangential view (arrow c), barlike ridge across dissepiment (arrow d), and obverse dissepiment stylets (arrow e), x 70; 5. FL48, deep tangential section illustrating longitudinal striae (arrow a) from which develop reverse microstylets (arrow b). Observe continuity of granular skeleton around autozooecial chamber near reverse-wall budding-site (arrow c) and with striae and microstylets, x 70; 6. FL48, shallow tangential section at site of branch bifurcation illustrating typical aperture placement (arrow a), apertural stylets (arrow b), and obverse stylets (arrow c), x 70. 224 Figure PALAEONTOGRAPHICA AMERICANA, NUMBER 57 EXPLANATION OF PLATE 33 LL Cubyonwstella globodensata; new Species: soei. erer reus erosion rent ae reds me oy in u we eR ca dri 153. AO, 10-11. Paratype, UI X-6710. Zoarial fragment exhibiting pronounced ontogenetic thickening. 1. Obverse exterior surface showing site of branch bifurcation (arrow a) and large, closely spaced nodes (arrow b) along obverse surface, x15; 3. Reverse exterior surface illustrating intermediate-size microstylets covering reverse zoarial surface, site of branch bifurcation (arrow a) and rows of microstylets across dissepiment surface (arrow b), x 30. . Paratype, UI X-6711. Obverse exterior surface of zoarial fragment illustrating aperture opening (arrow a), slight extension of aperture into fenestrule (arrow b), aperture placement at site of branch bifurcation (arrow c) and well-developed keel (arrow d), x30. Holotype, UI X-6702. Large, well-preserved moderately ontogenetically thickened zoarial fragment. 4. Reverse exterior surface showing variation in fenestrule size and shape, and site of branch bifurcation (arrow), x8; 5. Obverse exterior surface. Observe terminal diaphragm capping aperture (arrow a), intermediate-size obverse stylets (arrow b), barlike expansions across dissepiment surface (arrow c), and loss of distinct zoarial features due to surficial covering by lamellar skeleton, x 30; 7. FL27, deep to mid longitudinal section, obverse to left, illustrating continuity of granular skeleton along reverse wall (arrow a), around autozooecial chambers, reverse microstylets (arrow b), and obverse nodes (arrow c). Note typical chamber outline in deep mid longitudinal view (arrow d), x 70; 8. FL29, shallow to mid longitudinal section, obverse to left, showing autozooecial chamber outline in shallow (arrow a) and longitudinal (arrow b) views, x70. . Paratype, UI X-6750. TA65, transverse section of moderately ontogenetically thickened zoarial fragment showing con- tinuity of granular skeleton with longitudinal striae and microstylets (arrow a), across dissepiment between branches (arrow b) and thickened in the branch axis (arrow c), x 70. . Paratype, UI X-6826. FD35, transverse section showing typical chamber shape and attitudinal relationship to plane of obverse surface (arrow a), obverse stylets (arrow b) and chamber plugged by thickened granular skeleton (arrow c), x 70. Paratype, UI X-6823. 10. FD20, transverse section showing continuity of granular skeleton with keel (arrow) and initial nodal development, x70; 11. FD21, shallow longitudinal section, obverse to right, illustrating terminal diaphragm development (arrow a), apertural stylets (arrow b), and chamber outline in very shallow longitudinal view (arrow c), x 70. PLATE 33 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 PLATE 34 MISSISSIPPIAN BRYOZOANS: SNYDER 225 EXPLANATION OF PLATE 34 Figure Page 1-6. Gibifenestelln. globodensatu, new, SPCC ES oiis cack was A e en hs Supima ao Ps qure cde ela cassie elle de 95 l. Paratype, UI X-6828. FD38, shallow to deep tangential section of well-preserved zoarial fragment. Note change in chamber outline from deep tangential (arrow a) to mid tangential (arrow b) and to shallow tangential (arrow c) views: also, longitudinal | striae (arrow d) continuous with inner granular skeletal layer and microstylets developing atop striae along reverse surface (arrow e), and dissepiments (arrow f), x40. | 2. Paratype, UI X-6713. FL89, transverse section of dissepiment, distal to top and obverse to right, showing continuity of granular Skeleton across center of dissepiment (arrow), x 70. 3,5. Holotype, UI X-6702. FV69. 3. Shallow tangential section showing aperture outline (arrow a), apertural stylet developed at abaxial aperture edge (arrow b) and granular skeleton along center of branch over which keel (arrow c) develops from thickened lamellar skeletal material, x 70; 5. Shallow to deep tangential section illustrating nodes (arrow a) developed atop keel, and both shallow (arrow b) and mid (arrow c) tangential views of sites of branch bifurcation, x25. 4. Paratype, UI X-6822. FD14, shallow to very shallow longitudinal section, obverse to left, illustrating granular skeleton at edge of branch continuous with that at developing dissepiment edge (arrow a) and most adaxial edge of aperture (arrow b) extending slightly into fenestrule opening, x 70. 6. Paratype, UI X-6750. TA67, shallow to mid tangential section. Note typical chamber outline in mid tangential view (arrow a), apertural stylets around aperture (arrow b) which fuse to form the peristome, continuity of granular skeleton across dissepiment (arrow c), and obverse node developing atop keel (arrow d), x70. 226 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 EXPLANATION OF PLATE 35 Figure Page 1-12. Apertostella for POPPE ASPECT en ee AS ee ep) 1,3, 5-12. Holotype, UI X-6766. Large, well-preserved, moderately ontogenetically thickened zoarial fragment. 1. Reverse exterior surface showing macrostylet development (arrow), fenestrule openings, and site of branch bifurcation, x8; 3. FG7, transverse section of dissepiment, distal to top and obverse to left, showing continuity of granular skeleton across middle of dissepiment (arrow), x 70; 5. Greatly enlarged obverse exterior surface. Note typical attitudinal relationship of aperture to plane of obverse surface (arrow a), peristome surrounding aperture and slight extension of aperture into fenestrule (arrow b), keel (arrow c), nodes atop keel (arrow d), and longitudinal ridges across dissepiment (arrow e), x 30; 6. Obverse exterior surface illustrating site of branch bifurcation (arrow) and typical mesh pattern, x8; 7. FG52, shallow to shallow mid longitudinal section, obverse to left, showing continuity of granular skeletal material around chambers and with peristome at distal end of aperture (arrow), x 70; 8. FG3, transverse section showing continuity of granular skeleton with longitudinal striae (arrow a), obverse nodes (arrow b), and across dissepiments (arrow c). Note moderately thickened lamellar skeleton (arrow d) covering reverse surface, x 70; 9. FG52, mid longitudinal section, obverse to left, illustrating typical chamber outline in this view (arrow a). Note pronounced increase in chamber depth when compared to shallow longitudinal section, and high reverse-wall budding-angle (arrow b), x 70; 10. FG3, deep mid to deep longitudinal section, obverse to left, showing typical chamber outline in deep mid longitudinal view (arrow a), terminal diaphragm (arrow b), and granular skeletal layer continuous around autozooecial chambers (arrow c), and with reverse microstylets (arrow d), x70; 11. FG7, transverse section illustrating typical attitudinal relationship of aperture to plane of obverse surface (arrow a) and mid cross-sectional chamber outline (arrow b), x70; 12. FG7, shallow longitudinal section, obverse to left, showing chamber outline in this view (arrow). Note greatly reduced thickness of lamellar skeleton in this zoarium, x 70. . Paratype, UI X-6721. Reverse exterior surface of highly ontogenetically thickened zoarial fragment showing increased size of macrostylets (arrow) and reduced fenestrule opening size due to thickening of branches by lamellar skeletal layer, x8. . Paratype, UI X-6770. Reverse exterior surface of zoarial fragment exhibiting slight ontogenetic thickening of lamellar skeleton. Note longitudinal striae (arrow a), microstylets (arrow b), barlike ridge extending across reverse dissepiment surface (arrow c), and site of branch bifurcation (arrow d), x 30. PLATE 35 NUMBER 57 > PALAEONTOGRAPHICA AMERICANA PLATE 36 MISSISSIPPIAN BRYOZOANS: SNYDER 227 EXPLANATION OF PLATE 36 Figure Page 1-3. Apertostella for OPA S ESPECIES vi NERO S SETTIMANE X uu om LL M M LL. T. 99 Holotype, UI X-6766. FG53. 1. Shallow tangential section showing node (arrow a) positioned atop and as projection of keel (arrow b). Note attitudinal relationship of aperture (arrow c) to plane of obverse surface, x 70; 2. Shallow to mid tangential section illustrating typical mesh symmetry. Observe change in chamber outline from very shallow (arrow a), to shallow (arrow b) to shallow mid tangential section (arrow c), and continuity of granular skeleton across dissepiment (arrow d) between branches, x 70; 3. Mid to deep tangential section illustrating longitudinal striae (arrow a) extending along reverse chamber wall from which microstylets (arrow b) develop, and change in chamber outline from deep tangential (arrow c) near reverse-wall budding-site to mid tangential section (arrow d), x70. Ee Apenosiella Crassdfl, DON SDCCIOS ea cp Mere nee ee ee a se «wey ueque ELA. oe 101 4-6, 8, 9. Holotype, UI X-6737. Large, highly ontogenetically thickened zoarial fragment. 4. Obverse exterior surface showing typical mesh symmetry and sites of branch bifurcation, x8; 5. Greatly magnified obverse exterior surface illustrating keel (arrow a), aperture opening (arrow b) and its attitudinal relationship to plane of obverse surface, site of branch bifurcation (arrow c), nodes (arrow d), and recessed dissepiment (arrow e) connecting branches, x20; 6. FR7, transverse section Observe continuity of granular skeleton with reverse longitudinal striae (arrow a), keels and nodes (arrow b), and aperture opening (arrow c) illustrating typical attitudinal relationship of aperture to plane of obverse surface, x 70; 8. Reverse exterior surface illustrating fenestrule shape (arrow a) and site of branch bifurcation (arrow b). Note change in fenestrule outline from obverse (ovate) to reverse (elliptical) zoarial surfaces, x 4; 9. FR7, transverse section showing continuity of granular skeleton with reverse microstylets (arrow a) and across dissepiment (arrow b). Note typical chamber outline in cross-sectional view (arrow c), x70. 7. Paratype, UI X-6740. FR37, shallow tangential section illustrating keel (arrow a) and complete peristome (arrow b) surrounding aperture, also shown is typical aperture outline in this view, x 70. 228 Figure 1 O MIEN SIS NSB X du. en A Unde eie re uns NE ae A 1,59, e 0, PALAEONTOGRAPHICA AMERICANA, NUMBER 57 EXPLANATION OF PLATE 37 Holotype, UI X-6737. 1. FRS, shallow longitudinal section, obverse to right, abaxial edge of aperture (arrow a), and granular skeletal layer continuous across dissepiment (arrow b), x70; 8. FR11, mid tangential section illustrating continuity of granular skeleton across dissepiment (arrow), x 70; 9. FR12, deep tangential section. Observe autozooecial chamber outline near reverse-wall budding-site (arrow a) and continuity of lamellar skeletal layer with longitudinal striae, along branch (arrow b), and across dissepiment (arrow c), and microstylets developing as extensions of these striae (arrow d), x 70. Paratype, UI X-6738. 2. FR41, mid longitudinal section, obverse to left, illustrating typical chamber outline in this view (arrow a) and peristome developed at distal end of aperture (arrow b), x 70; 3. FR42, deep to mid longitudinal section, obverse to left, showing continuity of granular skeleton around autozooecial chambers (arrow a) and chamber outline in deep longitudinal view (arrow b), x 70; 5. FR41, very shallow longitudinal section, obverse to left, showing continuity of granular skeleton across dissepiment and with reverse microstylets (arrow), x 70; 6. FR42, mid longitudinal section, obverse to left, illustrating typical chamber outline in this view (arrow) and high reverse-wall budding-angle, x 70. . Paratype, UI X-6740. 4. FR39, shallow to mid shallow tangential section showing recessed dissepiment relative to plane of obverse surface (arrow a) and dissepiment continuous between branches in deeper view (arrow b), autozooecial chamber outline in mid shallow section (arrow c), and peristome surrounding aperture exhibiting slight inflection into fenestrule in shallow section (arrow d), x 70; 7. FR37, mid tangential section illustrating typical chamber outline in this view (arrow a) and lack of apertural inflection into fenestrule (arrow b), x 70. PALAEONTOGRAPHICA AMERICANA, NUMBER 57 PLATE 37 PLATE 38 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 MISSISSIPPIAN BRYOZOANS: SNYDER 229 EXPLANATION OF PLATE 38 Figure Page 1-9. Apertostella VERUSTARNEWASDECIE SHINE CHP re Nats ESOS UAM CE E Sen renee cuida 104 Holotype, UI X-6875. Large, well-preserved zoarial fragment exhibiting slight ontogenetic thickening. 1. Obverse exterior surface showing typical mesh symmetry and appearance, and sites of branch bifurcation (arrow), x8; 2. Enlarged obverse exterior surface view showing typical aperture surrounded by peristome (arrow a) and attitudinal relationship of aperture to fenestrule opening, keel (arrow b) atop which develop nodes (arrow c), site of branch bifurcation (arrow d), and longitudinal ridges across dissepiment (arrow , e), x 20; 3. WR22, transverse section showing aperture (arrow a) and peristome surrounding aperture (arrow b) continuous with inner granular skeletal layer, x 70; 4. WR14, transverse section illustrating continuity of granular skeleton around autozooecial chamber (arrow a), with reverse longitudinal striae (arrow b) and nodes (arrow c), x 70; 5. WR1, mid to shallow longitudinal section, obverse to left, showing typical chamber outline in mid chamber (arrow a) and shallow longitudinal view illustrating edge of aperture extending into fenestrule (arrow b) and peristome (arrow c), x 70; 6. WR20, shallow tangential section showing peristome surrounding aperture (arrow a), keel (arrow b) with nodes developed atop keel (arrow c), site of branch bifurcation (arrow d), and continuity of granular Skeleton across dissepiment (arrow e), x 40; 7. WR5, mid longitudinal section, obverse to left, showing peristome continuous with granular skeletal layer (arrow), x 70; 8. WR15, deep to mid longitudinal section, obverse to left. Observe granular skeletal layer along reverse wall (arrow a), surrounding autozooecial chambers (arrow b), and obverse node (arrow c), x 70; 9. WR15, longitudinal section, Obverse to left, showing change in chamber outline from moderately deep (arrow a) to mid shallow (arrow b) longitudinal view, x 70. 230 Figure PALAEONTOGRAPHICA AMERICANA, NUMBER 57 EXPLANATION OF PLATE 39 Page 1-5. Apertostella venusta, new species ..... nee Eee EE T. E ROS 20d 104 Holotype, UI X-6875. 1. WR20, shallow tangential section showing granular skeletal layer around peristome (arrow a) and small obverse stylets (arrow b), x40; 2. WR20, very shallow to deep tangential section. Note typical chamber outline in mid tangential (arrow a) and mid shallow (arrow b) tangential view, continuity of granular skeleton across dissepiment (arrow c) and site of branch bifurcation (arrow d), x 40; 3. WR20, deep tangential section illustrating granular skeletal composition of longitudinal striae (arrow), x40; 4. WR22, shallow to deep tangential section showing slight inflection of aperture into fenestrule (arrow a), chamber outline near reverse-wall budding-site (arrow b) and reverse microstylets (arrow c), x40; 5. WR22, mid to mid shallow tangential section, illustrating typical chamber outline in mid shallow section (arrow), x 40. 6-125 Hein pie pereiviaia lieh USD IE Pes De CUNG. SR a on IM PUT ductos de dites cem 108 6, T2; 7-9, 11. Figured specimen, UI X-6927. HB14. 6. Transverse section illustrating typical chamber profile in cross-section and terminal diaphragm (arrow) capping aperture, x70; 12. Transverse section illustrating continuity of granular skeletal layer with longitudinal striae (arrow a), microstylets (arrow b), nodes (arrow c), and with peristome surrounding aperture (arrow d), x70. Figured specimen, UI X-6848. 7. Obverse exterior surface of zoarial fragment showing typical poorly developed reticulate meshwork (arrow). Note widening of branch proximal and thinning distal to sites of branch bifurcation, x8; 8. Enlarged obverse exterior surface showing typical aperture outline (arrow a) with aperture surrounded by well-developed complete peristome, obverse stylets (arrow b), and nodes (arrow c) positioned atop keel (arrow d), x 25; 9. Enlarged obverse exterior surface illustrating slight to moderate extension of aperture into fenestrule (arrow a) and onto dissepiment (arrow b). Note longitudinal ridge developed across obverse dissepiment surface (arrow c), x25; 11. Reverse exterior surface showing typical angular appearance of branches and dissepiments. Note variation in fenestrule outline from approximately hexagonal (arrow a) to rectangular (arrow b), medially thickened ridge across dissepiment surface, and site of branch bifurcation (arrow c), x8. . Figured specimen, UI X-6849. HB6, shallow longitudinal section, obverse to right, illustrating continuity of granular skeleton along reverse wall (arrow a), reverse microstylets (arrow b), and across dissepiment (arrow c), x40. PLATE 39 NUMBER 57 ^ PALAEONTOGRAPHICA AMERICANA PALAEONTOGRAPHICA AMERICANA, NUMBER 57 PLATE 40 MISSISSIPPIAN BRYOZOANS: SNYDER 231 EXPLANATION OF PLATE 40 Figure Page sa NN EAA ea es 108 1. Figured specimen, UI X-6848. HB3, deep tangential section illustrating reverse view of longitudinal striae (arrow a), rows of microstylets developed atop these striae (arrow b), rounded fenestrule outline in mid deep tangential view (arrow c), and much more rhombic fenestrule outline in deep tangential section associated with sharp or angular appearance to reverse branch surface (arrow d), x40. 2, 10. Figured specimen, UI X-6927. HB14. 2. Transverse section showing sharp, angular appearance of reverse branch surface (arrow), x40; 10. Transverse section showing continuity of granular skeleton between branches (arrow), x 40. 3. Figured specimen, UI X-6925. HB7, slightly tilted mid longitudinal section, obverse to right, illustrating well-developed zoarial support (arrow) extending from reverse zoarial surface, x 40. 4, 6, 8. Figured specimen, UI X-6849. 4. HB6, mid to deep longitudinal section, obverse to right, showing continuous granular skeletal layer (arrow a) extending along reverse wall and around autozooecial chambers, with same granular layer also continuous with microstylets (arrow b), nodes (arrow c), and obverse stylets (arrow d); also illustrated is typical chamber outline in mid longitudinal view (arrow e) and angular dissepiments (arrow f), x 70; 6. Enlarged obverse exterior surface illustrating reticulate meshwork (arrow a) developed atop zoarial surface, with meshwork developing from nodes, keel, and } dissepiment ridges along obverse surface (arrow b) and mesh intersection in middle of branch and middle of fenestrule, x25; 8. HB6, shallow longitudinal section, obverse to right, showing continuity of granular skeleton across dissepiment (arrow a) and apertural extension into fenestrule at branch abaxial edge (arrow b), x 70. 5. Figured specimen, UI X-6934. FA76, shallow mid longitudinal section, obverse to left, showing granular skeleton continuous with peristome at obverse edge of aperture (arrow a) and typical chamber outline in this view (arrow b), x 70. 7,9. Figured specimen, UI X-6730. 7. Enlarged reverse exterior surface showing longitudinal ridges (arrow a) and reverse microstylets (arrow b), x 30; 9. Enlarged obverse exterior surface showing typical aperture capped by centrally thickened terminal diaphragm (arrow a) and obverse stylets across dissepiment (arrow b) and atop branches, x 30. 232 Figure PALAEONTOGRAPHICA AMERICANA, NUMBER 57 \ EXPLANATION OF PLATE 41 1-3. rey ah le iii er ACM Ele ee c a ee Er 108 by seas 2. 3. Figured specimen, UI X-6849. HB57. 1. Shallow to deep tangential section showing mesh symmetry characteristic of this species. Note longitudinal striae (arrow a), typical chamber outline near reverse-wall budding-site (arrow b), and irregular outline of fenestrule near obverse surface due to inflection of apertural adaxial edges into opening (arrow c) as compared to smooth elliptical fenestrule outline (arrow d) in mid tangential section and increasingly ovate (arrow e) to angular outline near reverse surface, x 20; 3. Mid to shallow tangential section showing typical chamber outline in mid tangential (arrow a) and in shallow tangential (arrow b) views, keel (arrow c) atop which develop obverse stylets (arrow d) and nodes (arrow e), and granular skeletal layer extending across dissepiment between branches (arrow f), x 40; 4. Shallow to very shallow tangential section. Observe slightly anastomosing or sinuous thickened keel (arrow a), near complete closure of fenestrule (arrow b) by thickened keel, typical attitudinal relationship of aperture to plane of obverse surface (arrow c) and peristome surrounding aperture (arrow d), x40. Figured specimen, UI X-6848. HB10, very shallow to shallow tangential section illustrating elongate node (arrow a) developed atop keel from which reticulate meshwork develops (arrow b), and intermediate-size obverse stylets (arrow c), x 70. Figured specimen, UI X-6924. HB13, shallow to deep tangential section showing site of branch bifurcation NN x 20. 6.7. Hon Henman ae EU 1359)... ie c oe cv ee Sn uM ir dt M DE 111 Figured specimen, UI X-6846. HB69, transverse section illustrating typical attitudinal relationship of aperture to plane of obverse surface (arrow a), longitudinal striae (arrow b) continuous with granular skeleton around autozooecial chambers, and thickened lamellar skeleton on reverse branch surface (arrow c), x 70. Figured specimen, UI X-6930. Reverse exterior view of large zoarial fragment showing typically rectangular, variably sized fenestrules (arrows a and b), x8. 6. T. PLATE 41 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 wu a pe T Pg d. [ I PLATE 42 NUMBER 57 m Te. LU PALAEONTOGRAPHICA AMERICANA MISSISSIPPIAN BRYOZOANS: SNYDER 233 y EXPLANATION OF PLATE 42 Figure Page ARE EMI Y DA hemitrypa eme ee ee ee 111 1-3. Figured specimen, UI X-6930. 1. Obverse exterior surface of large zoarial fragment illustrating intermediate to poor development of reticulate meshwork across obverse surface that exhibits typical mesh symmetry for this species. Arrow denotes site of branch bifurcation, x8; 2. Enlarged obverse exterior surface showing aperture (arrow a) exhibiting typical outline and attitudinal relationship to plane of obverse surface, peristome surrounding aperture, large nodes (arrow b), and poorly developed ridges across obverse dissepiment surface (arrow c), x25; 3. Enlarged exterior view of obverse surface partially covered by reticulate meshwork (arrow) that is typical of this species, x25. 4-6, 8, 9. Figured specimen, UI X-6844. 4. Enlarged obverse exterior surface showing aperture capped by centrally thickened terminal diaphragm (arrow a), inflection of aperture into fenestrule (arrow b), and intermediate-width keel (arrow c) atop which nodes develop (arrow d), x25; 5. Enlarged obverse exterior surface illustrating highly enlarged nodes (arrow) expanded to form reticulate meshwork which has been removed (probably during transport of specimen), x 25; 6. Enlarged reverse exterior surface showing macrostylet (arrow a) located at site of branch bifurcation, microstylets (arrow b), and typical fenestrule outline (arrow c), x 25; 8. Enlarged obverse exterior surface showing heterozooecia (ovicells?) developing as intermediate-size enlargements of autozooecial apertures (arrows a and b), x25; 9. FM8, transverse section showing continuity of granular skeleton (arrow) across dissepiment between branches, x70. 7, 11. Figured specimen, UI X-6932. HB23. 7. Mid to deep longitudinal section, obverse to left, showing typical chamber outline N in deep longitudinal view (arrow a) and obverse node (arrow b) connecting with inner granular skeletal material, x 40; 11. Mid longitudinal section, obverse to left, showing granular skeletal layer (arrow a) and typical autozooecial chamber outline (arrow b), and large reverse-wall budding-angle, x 40. 10. Figured specimen, UI X-6928. HB29, mid shallow to deep longitudinal section, obverse to left. Note granular skeletal layer continuous along reverse wall (arrow a) and surrounding autozooecial chambers; also shown are microstylets (arrow b), reticulate meshwork (arrow c), nodes (arrow d) of granular skeletal material connecting with reticulate meshwork, thickened nodes toward more medial section (arrow e), obverse stylets (arrow f) continuous with granular skeleton, and apertures capped by terminal diaphragms (arrow g) of granular skeletal material, x 70. 12. Figured specimen, UI X-6931. HB24, shallow longitudinal section, obverse to right, showing granular skeletal layer continuous across middle of dissepiment between branches (arrow), x40. 234 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 \ EXPLANATION OF PLATE 43 Figure Page VEN HOMER DURER ERE US LOUIS) aa CN Bee 111 1, 2, 7. Figured specimen, UI X-6930. HB26. 1. Shallow to deep tangential section showing typical mesh symmetry and longitudinal striae (arrow a) continuous with reverse microstylets (arrow b). Note inflection of autozooecial apertures into fenestrule (arrow c) causing slight closing of fenestrule toward obverse surface, x40; 2. Deep tangential section showing reverse microstylet development in rows along branch (arrow a) and across dissepiment (arrow b), x70; 7. Shallow tangential section illustrating thickened keel (arrow a) atop which develop nodes (arrow b) and obverse stylets (arrow c) all composed of granular skeletal material. Note reticulate meshwork (arrow d) developing as lateral extension of keel and nodes, and general appearance of meshwork in shallow tangential view (arrow e), X 70. 3, 4. Figured specimen, UI X-6933. HB33. 3. Transverse section showing typical branch profile in cross-section and attitudinal relationship of aperture to plane of obverse surface (arrow), x70; 4. transverse section showing granular skeletal layer (arrow a) continuous around autozooecial chamber, and obverse node (arrow b), x 70. 5, 6, 8, 9. Figured specimen, UI X-6844. 5. FM9, mid longitudinal section, obverse to left, showing typical chamber outline (arrow) in this view, x 70; 6. FMIO, shallow to mid longitudinal section, obverse to left, showing typical chamber outline (arrow) in shallow longitudinal view, x 70; 8. FM56, shallow to deep tangential section illustrating typical chamber outline in mid tangential view (arrow a), outline of enlarged heterozooecial chamber (arrow b), chamber shape at site of branch bifurcation (arrow c), extension of autozooecial aperture into fenestrule opening (arrow d), recessed dissepiment (arrow e), and continuity of granular skeletal layer across dissepiment (arrow f), x 40; 9. FM57, shallow to mid tangential section showing changing autozooecial chamber outline from shallow (arrow a) to mid (arrow b) tangential view, x 40. | PALAEONTOGRAPHICA AMERICANA, NUMBER 57 PLATE 43 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 PLATE 44 RW NITET Rp TT. ER | MISSISSIPPIAN BRYOZOANS: SNYDER 235 EXPLANATION OF PLATE 44 Figure Page 1-10. «Homitrypd Aprile MEN, SPECIOS E». c NEU enh tase ier fe Ea UNS CENE I Ecco ics we loc eg REED 114 1-3, 6-10. Holotype, UI X-6867. Large, well-preserved zoarial fragment exhibiting extremely well-developed reticulate meshwork characteristic of this species. 1. Obverse exterior surface illustrating thickened rows of meshwork atop branches (arrow a) compared to recessed, narrower rows between branches (arrow b), and in the middle of dissepiments and fenestrules; also note bifurcation of meshwork (arrow c) at site of branch bifurcation, x8; 2. Reverse exterior surface showing variation in fenestrule size, when comparing fenestrule at arrow a with fenestrule at arrow b, due to variation in thickening of lamellar skeletal layer, well-developed zoarial supports (arrow c) extending from reverse zoarial surface, and site of branch bifurcation (arrow d), x 8; 3. Enlarged obverse exterior surface of reticulate meshwork. Observe variation in mesh outline, varying from approaching square (arrow a) to hexagonal (arrow b), and typical four small projections into mesh openings (arrow c), x25; 6. HB94, deep to shallow longitudinal section, obverse to right, illustrating well-developed zoarial support (arrow a) projecting from reverse zoarial surface, enlarged dissepiments due to thickened lamellar skeletal layer (arrow b), centrally thickened terminal diaphragm with central granular skeletal spine (arrow c), typical chamber outline in mid longitudinal view (arrow d) and at abaxial edge of branch (arrow e), x40; 7. HB89, transverse section illustrating typical attitudinal relationship of aperture opening (arrow a) to plane of obverse surface, granular skeletal material composing reticulate meshwork (arrow b) and continuous with granular skeleton around autozooecial chambers i (arrow c) and with reverse microstylets (arrow d), x70; 8. HB89, transverse section showing granular skeletal layer | continuous with node (arrow a) which develops along middle of obverse surface atop keel to become centrally thickened ridge (arrow b) of reticulate meshwork (arrow c). Note typical chamber outline in mid transverse view (arrow d), x40; 9. HB89, deep to mid longitudinal section, obverse to right, illustrating chamber outline in deep longitudinal view (arrow a), and granular skeletal layer (arrow b) surrounding autozooecial chambers and continuous with reverse microstylets (arrow c), nodes developing into initial reticulate meshwork (arrow d), reticulate meshwork itself (arrow e), and obverse stylets (arrow f), x 70; 10. HB89, mid to shallow longitudinal section, obverse to right, showing continuity of granular i skeletal layer across dissepiment (arrow a) and typical chamber outline (arrow b) in mid longitudinal view, x40. | 4. Paratype, UI X-6865. Enlarged obverse exterior surface illustrating aperture with well-developed surrounding peristome t (arrow a), centrally thickened terminal diaphragm (arrow b), nodes (arrow c) located atop keel along branch midline; also note initiation of reticulate meshwork atop branch (arrow d) and longitudinal ridges (arrow e) atop dissepiment surface, x25. . Paratype, UI X-6866. Enlarged obverse exterior surface showing inflection of adaxial apertural edge into fenestrule opening (arrow a) and obverse stylet positioned near site of branch bifurcation (arrow b), x25. wn Page 236 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 EXPLANATION OF PLATE 45 Figure 1-8. Hemithypmuprilae, diewispeciescu uin Soon bar. a xm Ge em happened ore vr hd a ee ne 114 1, 2, 5, 6, 8. Holotype, UI X-6867. 1. HB89, mid to shallow longitudinal section, obverse to right, illustrating typical autozooecial chamber outline in mid shallow longitudinal view (arrow a), abaxial apertural edge projecting into fenestrule (arrow b), centrally thickened terminal diaphragm (arrow c), peristome (arrow d) at distal edge of aperture and continuous with granular skeletal layer, and from which obverse spines (arrow e) project and which are connected to the reticulate meshwork (arrow f). Note stylets projecting into fenestrule (arrow g), x70; 2. HB86, mid to very shallow tangential section. Note well-developed peristome (arrow a) surrounding aperture, nodes (arrow b) that when enlarged become part of reticulate meshwork (arrow c), which is composed of granular skeletal material (arrow d), obverse stylets (arrow e), recessed dissepiments (arrow f) and projections of apertures into fenestrule opening (arrow g), x40; 5. HB86, mid to very shallow tangential section showing stylets (arrow a) developing as projections of peristome surrounding aperture (arrow b), and thick keel (arrow c) from which projections develop to form the reticulate meshwork (arrow d), x 20; 6. HB86, shallow to deep tangential section. Observe pronounced projections of apertures into fenestrules (arrow a) near obverse surface not evident in mid tangential view (arrow b), where fenestrule outline is elliptical, fenestrule approaching rectangular (arrow c) in deep tangential view near reverse surface; note chamber outline at site of branch bifurcation (arrow d), x 20; 8. HB86, mid shallow to deep tangential section showing typical chamber outline near obverse surface (arrow a), in mid tangential view (arrow b) and near reverse-wall budding-site (arrow c); also shown are longitudinal striae (arrow d) from which reverse microstylets develop, x 40. . Paratype, UI X-6866. 3. HB39, deep tangential section showing numerous well-developed microstylets (arrow), x 40; 4. Reverse exterior surface showing typical fenestrule outline (arrow) in zooecial fragment exhibiting little secondary thickening of lamellar skeleton, x8. . Paratype, UI X-6865. HF94, transverse section illustrating branch spacing and continuity of granular skeleton between branches (arrow) across dissepiment, x 40. PLATE 45 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 PI rir Vas annem PLATE 46 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 | MISSISSIPPIAN BRYOZOANS: SNYDER 237 EXPLANATION OF PLATE 46 Figure Page E13: Hemitryparaspera@liich:1800. 2... Au c ae hes ee een 116 1. Figured specimen, UI X-6852. Obverse exterior surface of well-preserved zoarial fragment showing site of branch bifurcation (arrow a) and reticulate meshwork (arrow b) covering obverse surface, x 8. 2-5. Figured specimen, UI X-6854. Highly ontogenetically thickened zoarial fragment. 2. Enlarged reverse exterior surface illustrating longitudinal striae (arrow a), macrostylets (arrow b), microstylets (arrow c) and positioning of both macrostylets and microstylets across reverse branch and dissepiment surfaces, x 25; 3. Enlarged obverse exterior surface illustrating aperture (arrow a) capped by centrally thickened terminal diaphragm, nodal development (arrow b) with nodes and keel extending outward to form reticulate meshwork (arrow c), and longitudinal ridge developed across obverse dissepiment surface (arrow d), which also extends outward to form meshwork, x 25; 4. Reverse exterior surface showing macrostylet development toward proximal end of zoarium (arrow) and lack of macrostylets at distal zoarial end, x 8; 5. Enlarged obverse exterior surface illustrating typical appearance of well- developed reticulate meshwork (arrow a) and inflections (arrow b) into mesh openings due to enlargement of nodes, N29. 6, 7, 10, 11, 13. Figured specimen, UI X-6856. Well-preserved zoarial fragment exhibiting slight ontogenetic thickening. 6. Enlarged | reverse exterior surface showing initial macrostylet development (arrow), x 25; 7. Enlarged obverse exterior surface i illustrating development of reticulate meshwork (arrow) extending from atop nodes, keel, and dissepiment. Note | well-developed rounded inflections into meshwork openings, x25; 10. HF98, shallow to very shallow longitudinal section, obverse to left, showing typical chamber outline in shallow longitudinal view (arrow) and height of reticulate | meshwork above branch surface, x 40; 11. HF94, transverse section illustrating aperture opening (arrow a) and its | attitudinal relationship to plane of obverse surface, granular skeleton continuous with longitudinal striae (arrow b), around autozooecial chambers, and with obverse nodes (arrow c). Note reticulate meshwork covering obverse surface (arrow d), x 70; 13. HF98, deep longitudinal section, obverse to right. Observe typical chamber outline in deep longitudinal view (arrow a), thick granular skeletal layer (arrow b) continuous around autozooecial chambers, and with reverse microstylets (arrow c), macrostylets (arrow d), obverse nodes (arrow e), and reticulate meshwork \ ; which forms in part as an extension of these nodes, x 40. 8, 12. Figured specimen, UI X-6857. 8. HF60, mid longitudinal section, obverse to right, illustrating chamber size and outline (arrow) and spacing of reticulate meshwork above obverse surface, x 40; 12. HF64, mid to shallow longi- \ tudinal section. Note continuity of granular skeleton of stylets with reticulate meshwork (arrow) covering obverse P surface, x70. 9. Figured specimen, UI X-6940. Enlarged obverse exterior surface illustrating keel (arrow a), obverse stylets formed | across branch surface (arrow b), nodes (arrow c) atop keel, and heterozooecia (arrow d) probably representing ovicells and developing as pronounced enlargements of some apertures, x25. 238 Figure li Henippa esperen, 1890 2.2. 0, ee de cr pM M ce. s ee ed emend 116 1-4. 3,0. 7. Hemutrypa vermifera (Ubach, 1890)... je get eis ee PALAEONTOGRAPHICA AMERICANA, NUMBER 57 EXPLANATION OF PLATE 47 Figured specimen, UI X-6857. 1. HF64, mid longitudinal section, obverse to right, illustrating typical chamber outline in this view (arrow a) and terminal diaphragm capping aperture (arrow b), relatively high reverse-wall budding-angle (arrow c) and well-developed reticulate meshwork (arrow d), x 70; 2. HF61, deep to shallow tangential section. Note extension of apertures into fenestrule (arrow a) causing inflections in fenestrule outline near obverse surface with lack of such inflections in mid tangential view (arrow b), reverse longitudinal striae (arrow c), macrostylets (arrow d), chamber arrangement at site of branch bifurcation (arrow e), and continuity of granular skeleton across dissepiment (arrow f), x 20; 3. HF67, shallow tangential section illustrating autozooecial aperture (arrow a) and sequence of mesh development from keel (arrow b) to node (arrow c) to layer of granular skeletal material bridging between nodes to form the base of the reticulate meshwork (arrow d), x40; 4. HF67, mid to shallow tangential section showing autozooecial aperture enlarged to become heterozooecium (ovicell?) (arrow), x 40. Figured specimen, UI X-6856. 5. HF99, shallow to deep tangential section of zoarial fragment showing changing chamber outline from near reverse-wall budding-site (arrow a), to mid chamber view (arrow b), to near obverse surface (arrow c). Observe longitudinal striae (arrow d) from which microstylets (arrow e) and macrostylets (arrow f) develop; also shown are obverse stylets (arrow g), x 40; 6. HF100, very shallow tangential section of reticulate meshwork showing mesh initiation from nodes on obverse surface (arrow a), and thick mesh (arrow b) composed of granular skeletal material, x 40. Figured specimen, UI X-6884. HF25, transverse section showing typical close spacing of branches and extension of longitudinal striae (arrow) laterally, connecting to form dissepiment, x40. 119 PLATE 47 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 PLATE 48 Lae ve PRA Y oF + Sastry? Je SM | MISSISSIPPIAN BRYOZOANS: SNYDER 239 EXPLANATION OF PLATE 48 Figure Page lle Homitrypa vermifera (Ulrich, 1890)". <2, 0 es ee es ha cn ee ee, 119 1, 2, 7. Figured specimen, UI X-6864. Large, well-preserved zoarial fragment exhibiting moderate ontogenetic thickening and well- | developed reticulate meshwork. 1. Obverse exterior surface showing pronounced thickening along branch midline (arrow s a) and bifurcation of branches (arrow b) evident in pattern of overlying reticulate meshwork, x 8; 2. Reverse exterior surface | illustrating variation in fenestrule outline from ovate (arrow a) to elliptical (arrow b), and site of branch bifurcation (arrow | c), x8; 7. HF25, transverse section showing typical branch spacing, x 40. ' 3. Figured specimen, UI X-6865. HF18, shallow to deep longitudinal section, obverse to right, illustrating typical chamber outline in deep longitudinal view (arrow a) and granular skeletal layer (arrow b) continuous across dissepiment, x40. 4, 5. Figured specimen, UI X-6880. 4. Enlarged obverse exterior surface view of reticulate meshwork showing thickened mesh along branch midline (arrow a) and thinned meshwork between branches (arrow b); also note small inflections into mesh (arrow c) along the edges of mesh openings, x25; 5. Enlarged obverse exterior surface showing heterozooecia (ovicells?) (arrow a) developing as enlargements of some apertures, complete peristome (arrow b) surrounding autozooecial aperture, 4 aperture position at site of branch bifurcation (arrow c), keel (arrow d), and node (arrow e) atop keel, obverse stylet (arrow | f), and longitudinal ridges developed atop dissepiments (arrow g), x25. 6, 8. Figured specimen, UI X-6882. HF28. 6. Shallow longitudinal section, obverse to left, showing cross-section of dissepiment with continuity of granular skeleton across middle (arrow), x40; 8. Shallow to mid longitudinal section, obverse to right, illustrating typical chamber outline in shallow longitudinal view (arrow) x 40. 9. Figured specimen, UI X-6881. HF29, deep tangential section showing longitudinal striae (arrow a) from which rows of microstylets (arrow b) develop. These become increasingly irregularly positioned (arrow c) in deepest section toward reverse zoarial surface, x 40. 10. Figured specimen, UI X-6883. HF34, transverse section illustrating terminal diaphragm (arrow a) across aperture, which exhibits typical attitudinal relationship of opening to plane of obverse surface, continuity of granular skeletal material around autozooecial chambers, with longitudinal striae (arrow b), microstylets (arrow c), and nodes (arrow d), x 70. 240 Figure (A 1390). e det A rt i intent WD enc MM pen re als, GRA. gu Oe DEAS MNA oe ale 119 1:9, PALAEONTOGRAPHICA AMERICANA, NUMBER 57 EXPLANATION OF PLATE 49 Figured specimen, UI X-6881. 1. HF17, shallow to deep tangential section illustrating typical autozooecial chamber outline in mid tangential view (arrow a) as compared to outline in shallow tangential view (arrow b), site of branch bifurcation in mid chamber view (arrow c), and fenestrule outline in deep (arrow d), mid (arrow e), and mid shallow (arrow f) tangential view, x20. 5. HF33, mid to deep tangential section showing autozooecial chamber outline near reverse-wall budding-site (arrow a) and continuity of granular skeletal material between branches in middle of dissepiment (arrow b), x 20. . Figured specimen, UI X-6864. 2. HF35, shallow tangential section showing aperture (arrow a) surrounded by complete peristome, heterozooecium (arrow b) probably representing ovicell, obverse stylets (arrow c) projecting from top of recessed dissepiment, keel (arrow d), and nodes (arrow e) developing as extension of keel, x 40; 3. HF35, shallow tangential section of reticulate meshwork illustrating nodes (arrow a) with stylets (arrow b) developing atop keel between nodes, initial reticulate meshwork development as extensions of node, dissepiment, and keel (arrow c), increasing thickening of mesh granular skeleton (arrow d), with four inflections into mesh opening in most shallow view, and stylets of granular skeleton (arrow e) connecting with mesh. Note that each opening or hole in the meshwork corresponds to one aperture opening on the obverse surface, x 40; 6. HF27, tangential section of reticulate meshwork illustrating typical mesh pattern and inflections into mesh opening (arrow), x 20. . Figured specimen, UI X-6863. HF20, shallow to deep longitudinal section, obverse to left, illustrating terminal diaphragm (arrow a) capping autozooecial chamber that exhibits a typical outline in mid longitudinal view, aperture extension into fenestrule at abaxial branch edge (arrow b), granular skeletal layer surrounding autozooecial chambers (arrow c) continuous with reverse microstylets (arrow d), nodes (arrow e), reticulate meshwork (arrow f), and thinned meshwork (arrow g), not continuous with nodes, bridging obverse surface, x 70. PLATE 50 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 t MISSISSIPPIAN BRYOZOANS: SNYDER 241 EXPLANATION OF PLATE 50 Figure Page WS Archimedes Lee inca a eR E RI eem OW o NEM 124 1, 2, 5, 8, 10, 11. Figured specimen, UI X-6975. Well-preserved zoarial fragment containing central axis with attached mesh. 1. Enlarged obverse exterior surface illustrating incomplete peristome surrounding all but most proximal to proximal— adaxial edge of aperture (arrow a), moderate projection of aperture into fenestrule, keel (arrow b) atop which nodes develop (arrow c). Note longitudinal ridges across dissepiments (arrow d), x 30; 2. Exterior side view of dextrally | spiraling central axis showing typical axial shape and areas at the outer edge of axial whorls (arrow) where branches | have been broken from spiral, x 7.5; 5. Reverse exterior surface of mesh exhibiting moderate thickening due to addition of lamellar skeleton during ontogeny and illustrating typical fenestrule size and shape (arrow a), and site of branch bifurcation (arrow b), x15; 8. Exterior side view of dextrally spiraling central axis showing angle at which whorls diverge from plane of axis (arrow), x6; 10. AN88, shallow mid to mid longitudinal section, obverse to right, showing typical chamber outline in mid longitudinal section (arrow a) and continuity of granular skeletal material with peristome (arrow b), x 70; 11. ANSS, transverse section showing autozooecial aperture (arrow a) and typical attitudinal relationship of aperture to plane of obverse surface, and granular skeletal layer continuous with longitudinal striae (arrow b) and around autozooecial chambers, x 70. 3, 4, 6, 12, 13. Lectotype, ISGS (ISM) 2785-2. 3. Exterior side view of sinistrally spiraling zoarial axis attached to zoarial mesh (arrow) radiating outward from branch axis, x3; 4. Reverse exterior surface of zoarial mesh illustrating typical fenestrule shape and size (arrow a). Note fenestrule almost closed by thickened lamellar skeleton at edge of spiral axis (arrow b) and longitudinal striae (arrow c) along reverse branch surface, x12; 6. Enlarged obverse exterior surface showing typical mesh symmetry and site of branch bifurcation (arrow), x 30; 12. AN42, transverse section showing two branches joined by dissepiment (arrow) across which extends granular skeletal material continuous around autozooecial chambers, x 70; 13. AN42, transverse section illustrating typical spacing of branches and | chamber outline in mid transverse view, x 70. 7,9. Paralectotype, ISGS (ISM) 2785-1. 7. Exterior side view of sinistrally spiraling central axis illustrating delicate axis in this species (arrow a) and mesh (arrow b) developing at edge of axial whorls, x 3; 9. AN9, mid shallow to deep longitudinal section, obverse to left, illustrating typical autozooecial chamber outline in deep view (arrow a), highly elongate vestibule (arrow b) in mid longitudinal autozooecial chamber view. Note plugging of aperture by thickened lamellar skeleton composing central axis (arrow c), x 70. 242 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 EXPLANATION OF PLATE 51 Figure 1-8 WiehumeHes negligens OTC lise 190 we... modum en E. d I NEED RUE Dee 124 1. Paralectotype, ISGS (ISM) 2785-1. AN2, transverse view of zoarial axis exhibiting sinistral spiraling as viewed toward proximal end of zoarium. Observe transverse section of central axial branch (arrow a), flattening of mesh in tangential section at edge of whorl (arrow b), and fenestrule (arrow c) in tangential view; also shown is reorientation of mesh during spiraling from middle to lateral edge of axis, x 40. 2-5. Lectotype, ISGS (ISM) 2785-2. 2. AN47, shallow to mid tangential section illustrating extension of abaxial aperture margin into fenestrule (arrow a) causing inflection in fenestrule outline near obverse surface, lack of inflection in mid tangential view (arrow b) of fenestrule, typical chamber outline in shallow tangential view (arrow c) and incomplete peristome surrounding all but proximal to proximal-adaxial edge of aperture with apertural diaphragm (arrow d), x 70; 3. AN49, shallow to mid tangential section showing well-developed incomplete peristome (arrow a) and slight inflection of aperture opening onto dissepiment (arrow b), x 70; 4. AN44, mid shallow to mid tangential section showing typical mesh symmetry, and continuity of granular skeleton (arrow) across dissepiment, there forming single longitudinal ridge across dissepiment obverse surface, x 70; 5. AN49, shallow to deep tangential section illustrating typical chamber outline in mid tangential view (arrow a), chamber outline near reverse- wall budding-site (arrow b), and longitudinal striae (arrow c), connected with granular skeletal material which also connects with reverse microstylets (arrow d), x 70. . Figured specimen, UI X-7009. AN24, section cutting along central plane of sinistrally spiraling axis, illustrating change in central axial branch orientation from proximal to distal end of axial fragment. Spiraling central axial branch is well-documented in this figure, showing longitudinal section (arrow a) with obverse to left near proximal end of axial fragment, becoming a tangentially oriented branch (arrow b) in middle of axial fragment, shifting toward longitudinal (arrow c) toward distal end and at most distal edge of axial fragment becoming a longitudinal section (arrow d) with obverse now to right; fenestrule (arrow e) and apertures surrounded by peristome (arrow f) are visible in mid axis tangential view, x35. PLATE 51 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 PLATE 52 ( MISSISSIPPIAN BRYOZOANS: SNYDER 243 EXPLANATION OF PLATE 52 Figure Page 1-4. Archimedes UA 3890... A Se dae ES A each hac lac E e a 124 1-3. Figured specimen, UI X-6975. 1. AN73, transverse view of zoarial axis illustrating transverse section of central axial branch (arrow a) showing aperture plugged by lamellar skeleton of axis, granular skeletal layer continuous around autozooecial chambers and with reverse longitudinal striae (arrow b) and microstylets (arrow c), and flattening of mesh at edge of axis (arrow d). View is toward proximal end of axis, with lateral branches developing to the left of the axial branch in dextral spiraling, x 79; 2. AN81, longitudinal section near center of dextrally spiraling axis showing axial whorls (arrow a) and thickened lamellar skeletal layer forming bulk of central axis (arrow b), x 20; 3. AN56, shallow to deep longitudinal section, obverse to right, showing | typical chamber outline in mid longitudinal view (arrow a), and continuity of granular skeletal layer with obverse nodes (arrow b) and across dissepiment (arrow c), x70. | 4. Paralectotype, ISGS (ISM) 2785-1. AN10, mid to shallow longitudinal section, obverse to left, showing continuity of granular skeletal material continuous with peristome (arrow), x70. SY Areh medos OWENANUS al TESO e a Gee a EL. ccce IT ee 127 5,9. Paralectotype, ISGS (ISM) 2790. 5. Exterior side view of two central axes having a common point of origin (arrow a), exhibiting both dextral (arrow b) and sinistral (arrow c) spiraling within the same zoarium. Note abundant zoarial supports developed on reverse mesh surfaces, x2; 9. Other side of zoarial fragment shown in figure 5 above, illustrating common source (arrow a) from which both dextral (arrow b) and sinistral (arrow c) spiraling are observed. Oppositely coiled spirals of this nature as | extensions of one zoarium are commonly observed in Archimedes, x1. 6. Figured specimen, UI X-6993. Reverse exterior mesh surface illustrating variation in fenestrule outline (arrow) as a result of thickening of lamellar skeletal layer during ontogeny, x6. 7. Figured specimen, UI X-6973. AM41, transverse section showing typical branch and autozooecial chamber outline in this view, x 40. 8. Figured specimen, UI X-6983. Exterior side view of well-preserved zoarial fragment illustrating well-developed central axis (arrow a), reverse mesh surface extending outward from axis (arrow b), and obverse surface (arrow c) extending outward from | axis showing slightly concave mesh, x2. 244 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 EXPLANATION OF PLATE 53 Figure 1-10. Archimedes on eras OESTE 5570)... Vane en nee shes Begs ince, wot KO te ope, cod me Lp eor EC are 127 1-3. 4,5, 7:6. Page Figured specimen, UI X-6993. 1. exterior side view of sinistrally spiraling central axis illustrating overgrowths of mesh by lamellar skeleton extending for moderate distances laterally from edge of axis (arrow a) and zoarial supports formed from reverse mesh surfaces (arrow b), x2; 2. Exterior side view of sinistrally spiraling central axis illustrating pronounced thickening of lamellar skeleton along reverse mesh surface (arrow a), reverse mesh surface without overgrowths (arrow b) and zoarial support (arrow c) with three prongs extending toward distal end of support, x 1; 3. Obverse exterior surface of mesh exhibiting partial (arrow a) to complete (arrow b) overgrowth of obverse surface by thickened lamellar skeleton, x6. Figured specimen, UI X-7001. 4. Enlarged obverse exterior surface of extremely well-preserved zoarial fragment illustrating incomplete peristome (arrow a) partially surrounding aperture with gap (arrow b) at proximal to proximal-adaxial apertural edge. Note extension of aperture into fenestrule opening, aperture position at site of branch bifurcation (arrow c) with centrally thickened terminal diaphragm capping aperture, and keel (arrow d) atop which are positioned nodes (arrow e), x 30; 5. Enlarged obverse exterior surface showing site of branch bifurcation (arrow a) and single ridge (arrow b) extending across dissepiment, x 30; 7. Obverse exterior surface illustrating typical mesh pattern in this species, x10; 8. Enlarged reverse exterior surface of mesh illustrating variation in fenestrule shape (arrows a and b) as observed in reverse surficial view. Pronounced variation in reverse surface is a result of secondary overgrowths of lamellar skeleton on the reverse zoarial mesh surface, x 24. . Figured specimen, UI X-7006. Exterior side view of sinistrally spiraling zoarial fragment illustrating typical form of central axis (arrow) and axial whorls from which zoarial mesh emerges, x 2. . Figured specimen, UI X-6985. AO7. 9. Transverse section showing aperture capped by centrally thickened terminal diaphragm (arrow a) and exhibiting typical attitudinal relationship to plane of obverse surface. Note granular skeletal layer continuous with longitudinal striae (arrow b) and around autozooecial chambers (arrow c) as well as thickened lamellar skeletal layer covering reverse branch surface, x70; 10. Mid to deep longitudinal section, obverse to right, illustrating typical chamber outline in mid longitudinal section (arrow a), and granular skeletal layer continuous with obverse nodes (arrow b), around autozooecial chambers (arrow c) and with reverse microstylets (arrow d), x 70. | PLATE 53 A NUMBER 57 d PALAEONTOGRAPHICA AMERICANA PLATE 54 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 MISSISSIPPIAN BRYOZOANS: SNYDER 245 EXPLANATION OF PLATE 54 Figure Page rre ltimedesión ananusi(Elallasl ss): Sn... NELLO TEE ee eee ee 127 ; 1-4. Figured specimen, UI X-6985. 1. AO7, transverse section illustrating spacing between branches and fenestrule opening between | branches. Note great thickening of reverse lamellar skeletal layer (arrow a) and continuity of granular skeleton with reverse | microstylets (arrows b and c), x 70; 2. AO2, shallow to deep tangential section showing aperture capped by terminal diaphragm (arrow a), chamber outline near reverse-wall budding-site (arrow b), and longitudinal striae continuous with reverse microstylets (arrow c), initially occurring in rows which become more randomly positioned across reverse branch surface with ontogeny, x40; 3. AO7, mid shallow to very shallow longitudinal section, obverse to right, illustrating typical chamber outline in this | view and significant ontogenetic thickening (arrow) of lamellar skeleton along reverse branch surface, x 70; 4. AO7, very shallow to mid shallow longitudinal section, obverse to right, showing aperture in most shallow tangential view (arrow a) extending into fenestrule opening and onto distal part of dissepiment, typical chamber outline in mid shallow longitudinal view (arrow b) and thickened lamellar skeletal layer across dissepiment (arrow c), x 70. | 5, 7. Figured specimen, UI X-6986. 5. AO47, shallow to mid tangential section illustrating heterozooecia (ovicells?) with central | perforation (arrow a) and multi-generation heterozooecial development partially plugging fenestrule (arrow b), x70; 7. AO48, very shallow to deep longitudinal section, obverse to left, showing typical autozooecial chamber outline in deep (arrow a) and | mid (arrow b) longitudinal views, thin lamellar skeletal layer (arrow c) due to positioning of this zoarial fragment a pronounced | distance laterally away from central axis, and reverse zoarial support development (arrow d), x40. | 6. Figured specimen, UI X-6971. AG8, mid tangential section. Note typical autozooecial chamber outline in this view (arrow a), lack of apertural inflection into fenestrule (arrow b) in mid tangential view, and chamber outline at site of branch bifurcation (arrow c), x70. | ( 246 Figure DR ANCONS DWOHUHES Aral 1037 Bes ay) O e ere Oe Me da tob PEE, A TREE SERRE SUR 127 L 26. 4, 5. PALAEONTOGRAPHICA AMERICANA, NUMBER 57 EXPLANATION OF PLATE 55 Figured specimen, UI X-6986. AO47, shallow tangential section illustrating common heterozooecia (ovicells?) (arrow) developed locally across zoarial obverse surface, x 70. Figured specimen, UI X-6971. 2. AG8, mid to deep tangential section illustrating heterozooecia (arrow a) rimmed by lamellar skeletal layer and containing a central perforation (arrow b) giving it a doughnut-like appearance, typical chamber outline in mid tangential view (arrow c), and continuity of granular skeletal layer around autozooecial chambers and across dissepiment (arrow d), x 70; 6. Exterior side view of central axis with mesh attached (arrow) illustrating angle of mesh with axis, x2. . Figured specimen, UI X-6973. 3. AMAO, section cutting along central plane of sinistrally spiraling axis illustrating change in central axial branch orientation from slightly askew tangential (arrow a), to longitudinal with obverse to left (arrow b), and back to tangential section (arrow c) at distal end of axis, x 40; 7. AM46, section cutting along central plane of sinistrally spiraling axis with central axial branch exhibiting change of branch orientation (i.e., changing direction of obverse branch surface), which results in spiraling axis. Observe longitudinal section with obverse to left (arrow a), branch facing outward from page and becoming a tangential section distally (arrow b), and finally a nearly 180? turn is completed toward most distal end of axial section shown with obverse branch now to right (arrow c). Thick lamellar skeletal material comprises the axis, x 20. Figured specimen, UI X-7001. 4. AM5, mid to deep tangential section. Note longitudinal striae (arrow a) continuous with granular skeletal material that also connects with reverse microstylets (arrow b), and fenestrule outline in mid (arrow c) and deep (arrow d) tangential view, showing increase in fenestrule dimensions, x40; 5. AM21, very shallow to deep tangential section illustrating aperture outline in most shallow tangential view (arrow a), with aperture surrounded by peristome and capped by terminal diaphragm. Note change in autozooecial chamber size as aperture is connected to chamber at proximal edge (arrow b), autozooecial chamber outline in mid tangential view (arrow c) and near reverse-wall budding-site (arrow d), and nodes (arrow e) positioned atop keel, x 40. PLATE 55 NUMBER 57 > PALAEONTOGRAPHICA AMERICANA PALAEONTOGRAPHICA AMERICANA, NUMBER 57 PLATE \ MISSISSIPPIAN BRYOZOANS: SNYDER 247 EXPLANATION OF PLATE 56 Figure Page | DS ATOBIRedesOWehnanHs all E d Ro ID T UE. A ee... 127 | Figured specimen, UI X-6973. 1. AM42, section cutting plane of central axis showing whorl development (arrows a and b) as a result of thickened lamellar skeleton (arrow c) covering mesh surfaces laterally away from axial branch. Note obverse surface always faces upward in life position, x 12. 2. AM40, longitudinal section of spiral axis showing whorl (arrow a) connected to central axial branch | which changes orientation with spiraling (arrow b), x 20. | 3-9. Archimedes wortheni Gotai USS ADD SEE Oo ds E ÍA cq QN m incur E a 130 3. Figured specimen, UI X-6991. Reverse exterior view of mesh showing typical mesh pattern (arrow a) adjacent to area overgrown | by lamellar skeleton (arrow b). Such overgrown areas appear to represent healing of injured or broken areas of zoarial meshwork, x2 | 4, 6. Figured specimen, UI X-7014. 4. Dextrally spiraling central axis developed distal (arrow) to inferred ancestrula, x6; 6. Site of initial axial development at apparent distal end of mesh. Observe tip of thickened branch edge possibly representing ancestrula (arrow a) from which single thickened branch develops (arrow b). Mesh extends outward from one side of branch as suggested j by fenestrule development (arrow c), with initial spiral observed shortly in distal direction (arrow d), x24. | 5. Figured specimen, UI X-6992. Exterior side view of well-preserved dextrally spiraling specimen showing thick central axis | (arrow a) with mesh still attached to axis and extending outward at angle characteristic of that in life (arrows b and c). Observe area at edge of axis (arrow d) where mesh is partially overgrown by thickened lamellar skeleton of axis, and typical pattern of reverse mesh (arrow e), which radiates outward from axis, x2. | 7. Figured specimen, UI X-6995. Exterior side view of dextrally spiraling central axis (arrow a) showing zoarial supports (arrow b) developed between whorls as extensions of reverse zoarial (axial) surface (arrow c). Note thickened edge of axis from which mesh projects (arrow d), x2. | 8. Topotype, ISGS (ISM) 2780-2, exterior view of reverse mesh surface illustrating central axis (arrow a) with attached mesh | radiating outward (arrow b) from axis, X2. 9. Figured specimen, UI X-7005. View looking distally from end of axis showing mud and broken skeletal fragments infilling Í spacing between mesh projecting from axial whorls (arrow). Such infilling may have occurred while colony was in life position, x2. 248 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 EXPLANATION OF PLATE 57 Figure LEE EC wortnenr (Hall TEST da 130 1, 3. Figured specimen, UI X-6997. 1. Reverse exterior surface illustrating elliptical, ovate, or circular fenestrule shape (arrow a) and initial development of reverse zoarial supports (arrow b), x10; 3. Exterior side axial view showing mesh still attached to central axis (arrow), x1. 2, 7. Figured specimen, UI X-7005. 2. Exterior view of central axis from distal end of zoarium illustrating whorled appearance of thickened lamellar skeleton that forms the axis (arrow a), zoarial mesh overgrown by lamellar skeleton at edge of axis (arrow b) and mesh not overgrown (arrow c) toward most distal end of mesh, x 5; 7. Obverse exterior surface of zoarial mesh illustrating extension of abaxial aperture edge into fenestrule (arrow a), and thickening of keel and nodes along obverse branch surface (arrow b). Note thickening of lamellar skeleton across zoarial surface and capping of apertures by terminal diaphragms, x 30. 4-6. Figured specimen, UI X-6994. 4. Obverse exterior mesh surface of well-preserved fragment illustrating incomplete peristome Page (arrow a) surrounding aperture with opening occurring at proximal to proximal-adaxial aperture edge (arrow b), central keel (arrow c) atop which develop nodes (arrow d). Note site of branch bifurcation (arrow e) and centrally thickened terminal diaphragms capping apertures, x 30; 5. Obverse exterior surface view of meshwork overgrown by ridged lamellar skeleton (arrow) developing at edge of axis, x 12; 6. Exterior side axial view of large zoarial fragment containing large areas of mesh attached to axis (arrow), x2. . Figured specimen, UI X-6999. Obverse exterior surface showing heterozooecia (ovicells?) developed along branch midline (arrow), x40. . Figured specimen, UI X-7008. Reverse exterior surface of mesh illustrating pronounced variations in fenestrule outline (arrows a and b) in reverse view and appearance at site of branch bifurcation (arrow c), x20. | | | I PALAEONTOGRAPHICA AMERICANA, NUMBER 57 i PLATE 57 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 PLATE 58 | MISSISSIPPIAN BRYOZOANS: SNYDER 249 EXPLANATION OF PLATE 58 | Figure Page ED Archımedesshörtheni Grah TSI M SACR RUE. Gusta Si ee er ae 130 1, 2, 4-8. Figured specimen, UI X-6991. 1. AG72, transverse section showing secondary lamellar skeletal layer (arrow a) at axial edge overgrowing apertures (arrow b) which are capped with granular skeletal plug developed as extensions of centrally thickened diaphragm, x40; 2. AG69, transverse section showing typical attitudinal relationship of aperture to plane of obverse surface (arrow a), and granular skeletal layer continuous around autozooecial chambers (arrow b), with nodes (arrow c), reverse longitudinal striae (arrow d) and microstylets (arrow e). Note terminal diaphragm (arrow f) capping aperture, x 70; 4. AG77, mid to deep tangential section showing change in fenestrule outline from mid (arrow a) to deep (arrow b) tangential view, and granular skeletal layer continuous with longitudinal striae (arrow c), and reverse microstylets developing as extensions of these striae (arrow d), x 40; 5. AG70, shallow to very shallow longitudinal section, obverse to | left, illustrating aperture edge in very shallow longitudinal view (arrow a) and heterozooecia (ovicells?) as enlargements of | aperture (arrow b) extending into fenestrule, x 70; 6. AG70, mid to shallow longitudinal section, obverse to left, showing | aperture opening at edge of fenestrule (arrow a) and typical chamber outline in shallow longitudinal view (arrow b), x 70; 7. AG74, mid to mid shallow longitudinal section, obverse to left, illustrating typical autozooecial chamber outline in mid | shallow longitudinal view (arrow a) and terminal diaphragm (arrow b) capping aperture, x70; 8. AG70, mid to deep | longitudinal section, obverse to left, illustrating typical chamber outline in mid (arrow a) to deep (arrow b) longitudinal view, and continuity of granular skeletal material (arrow c) around autozooecial chambers, and with obverse nodes (arrow d) and reverse microstylets (arrow e), x 70. | 3. Figured specimen, UI X-6998. AM61, transverse section of axial branch (arrow a) viewed toward proximal end of zoarium with aperture plugged by lamellar skeleton of the axis, thick granular skeletal layer (arrow b) surrounding branch and continuous with microstylets (arrow c) extending through lamellar skeleton of axis. The axial branch acts as a guide determining direction and rate of of axis rotation, with adjacent lateral branches following the lead of this central, pivotal branch. The obverse surface of the axial branch “points” toward the direction of spiraling; whether the lateral branches | are in the left or right side of the axial branch determines if the spiral will be dextral or sinistral, x 60. 9. Figured specimen, UI X-7000. AM79, deep to mid shallow longitudinal section, obverse to right, showing elongate vestibule | (arrow a) developed as aperture was overgrown by lamellar skeleton in an attempt by the individual to remain connected | with the outside environment, and chamber outline in deep longitudinal view (arrow b), x 40. PALAEONTOGRAPHICA AMERICANA, NUMBER 57 \ EXPLANATION OF PLATE 59 Figure Ip AN CIIICU PS EH ONESIONY (NALLY 357). ae... a lee ee ba HARE oR 1. Figured specimen, UI X-6990. AI71, shallow to deep tangential section of zoarial fragment exhibiting pronounced ontogenetic thickening. Note site of branch bifurcation (arrow a) and fenestrules partially to completely plugged by lamellar skeleton (arrow b), x20. E 2. Figured specimen, UI X-6997. AM84, very shallow tangential section showing incomplete peristome (arrow a) surrounding all d but most proximal to proximal-adaxial aperture edge (arrow b), peristome at edge of aperture overgrown by lamellar skeleton Í (arrow c), keel (arrow d) atop which nodes develop (arrow e), and obverse stylets (arrow f) continuous with inner granular j $ f skeletal layer, x70. 3-5. Figured specimen, UI X-6991. Large, well-preserved zoarial fragment. 3. AG75, mid to shallow tangential section. Observe circular heterozooecia (ovicells?) with central opening (arrow a) surrounded by a circular layer of lamellar skeleton (arrow b), and extension of abaxial edge of aperture (arrow c) into fenestrule causing inflections in fenestrule outline near obverse surface, x 70; 4. AG75, very deep tangential section illustrating granular appearance caused by presence of abundant microstylets (arrow) | continuous with inner granular skeletal layer, x70; 5. AG67, mid to deep tangential section showing typical autozooecial chamber outline in mid (arrow a) and deep (arrow b) tangential views. Note increased variability of chamber outline in mid } tangential view at site of branch bifurcation (arrow c), lack of extension of aperture into fenestrule in mid tangential view (arrow d), and continuity of granular skeletal material between branches across dissepiment (arrow e), x70. | 1 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 PLATE 59 æ LI PLATE 60 NUMBER 57 > PALAEONTOGRAPHICA AMERICANA MISSISSIPPIAN BRYOZOANS: SNYDER 251 EXPLANATION OF PLATE 60 Figure Page ee Archimedes wonken IST on. m en: a en eee. RU eu ew oe eee. cod, 130 Figured specimen, UI X-6998. 1. AM61, transverse section of large central axis showing central axial branch (arrow a) pointing toward direction of axial spiral (in this case dextral) as viewed from proximal end of axis looking toward distal end. When viewed toward distal end of zoarium, if lateral branches develop to the right of the axial branch, spiraling is dextral; when lateral branches } develop to the left of axial branch in the same view, spiraling is sinistral. The axis spirals toward the obverse surface, resulting in } concave obverse and convex reverse mesh surfaces, respectively. Observe change in mesh orientation proceeding outward from | central axis, going from transverse (arrow a) to slightly askew, poorly oriented transverse (arrow b) to approaching tangential view | as mesh flattens toward whorl (arrow c). Also note development of thick lamellar skeletal layer (arrow d) forming central axis 1 surrounding axial branch, x15; 2. AMSS, longitudinal section near center of axis just shallow of central axial branch. Change in | branch orientation can be observed proceeding from axial whorl (arrow a), to longitudinal section approximately pointing toward axial whorl (arrow b). Also shown is a misoriented longitudinal section exhibiting elongate vestibule (arrow c), tangential section | (arrow d) associated with change of central axial branch orientation deeper in central axis than shown in section, and axial whorl (arrow e). Direction of axial spiral is dextral, x 12. | 3-9. Archimedes aaan anea aaa a ee ee ee 133 3. Holotype, UI X-6987. Exterior side view of dextrally spiraling specimen illustrating central axis (arrow) with zoarial mesh developed as extensions at lateral edge of axial whorls, x2. } 4. Paratype, UI X-6988. Exterior side view of sinistrally spiraling zoarium showing central axis (arrow a) and obverse mesh surfaces (arrow b) radiating outward from central axis, x2. | 5. Paratype, UI X-6989. Exterior side view of sinistrally spiraling specimen illustrating whorls (arrow) from which branches extend, T2 6, 9. Paratype, UI X-6981. 6. Obverse exterior surface of zoarial fragment having well-developed zoarial support (arrow a) at distal edge of fragment. Note fenestrules almost completely overgrown by lamellar skeleton at distal end of fragment (arrow b), and open with lesser overgrowths (arrow c) toward proximal end; also shown is site of branch bifurcation (arrow d), x8; 9. Reverse exterior surface illustrating zoarial support (arrow a) developed at distal edge of fragment, fenestrules almost completely overgrown by lamellar skeleton at fragment distal edge (arrow b) and fenestrules open toward proximal end (arrow c), and site of branch bifurcation (arrow d), x8. 7, 8. Paratype, UI X-6979. 7. Obverse exterior surface showing zoarial support (arrow a) and obverse mesh surface not covered by thickened lamellar skeleton (arrow b). Note typical mesh appearance in this species, x8; 8. Reverse exterior surface of zoarial fragment exhibiting pronounced ontogenetic thickening, with zoarial support developed at distal mesh edge and thickened lamellar skeleton (arrow) coating distal edge of zoarial mesh, x8. PALAEONTOGRAPHICA AMERICANA, NUMBER 57 | EXPLANATION OF PLATE 61 Figure Page 158, ATCHUREHESSPOLMIEyELT, De Speer... es cap, » MO Mp UII Lc 133 | 1. Paratype, UI X-6979. Obverse exterior surface showing aperture extending into fenestrule (arrow a) with incomplete peristome partially surrounding aperture open at proximal to proximal-adaxial edge, keel atop which develop numerous nodes (arrow b) which also are present atop dissepiment (arrow c), and small stylets (arrow d) atop obverse surface, x25. | 2, 3, 5-7. Paratype, UI X-6981. FY72. 2. Transverse section illustrating terminal diaphragm (arrow a) plugging aperture that exhibits } typical attitudinal relationship to plane of obverse surface, granular skeletal layer continuous around autozooecial chambers, | with reverse longitudinal striae (arrow b) and nodes (arrow c). Note fenestrule width between branches (arrow d) and typical chamber outline in transverse cross-sectional view (arrow e), x 70; 3. Very shallow longitudinal section, obverse to left, ) illustrating transverse section of dissepiment and continuity of granular skeleton through middle of dissepiment (arrow), x70; 5. Mid to deep longitudinal section, obverse to left, illustrating chamber outline in mid (arrow a) and deep (arrow | b) longitudinal views; also shown is obverse node (arrow c) continuous with granular skeletal layer surrounding autozooecial chambers, x 70; 6. Very shallow to mid longitudinal section, obverse to left, showing elongate vestibule (arrow) developing as a result of thickening of obverse lamellar skeletal layer, x70; 7. mid to very shallow longitudinal section showing N autozooecial chamber outline in mid (arrow a) and very shallow (arrow b) longitudinal views. Note extensions of aperture opening into fenestrule (arrow c), x 70. | 4. Holotype, UI X-6987. AI30, transverse section exhibiting pronounced ontogenetic thickening of lamellar skeletal layer at edge of axis covering obverse surface. Note continuity of granular skeletal layer around autozooecial chambers, across dissepiment (arrow a), with terminal diaphragm (arrow b), small obverse stylets (arrow c) and reverse microstylets (arrow d), x 70. 8. Paratype, UI X-6989. AI90, section cutting along central plane of sinistrally spiraling axis showing change in central branch orientation as this branch spirals along center of axis, changing branch orientations include tangential at proximal fragment end (arrow a), longitudinal with obverse to left in middle of fragment (arrow b), and back to approaching deep tangential at distal end of fragment (arrow c), x 20. PALAEONTOGRAPHICA AMERICANA, NUMBER 57 PLATE 61 PLATE 62 NUMBER 57 » PALAEONTOGRAPHICA AMERICANA TE A y AR MISSISSIPPIAN BRYOZOANS: SNYDER 253 - EXPLANATION OF PLATE 62 Figure Page | oWärchimedes yalmeyerim ew. Species TET D eee Ime facinora er lt M ees easly Tee 133 1. Paratype, UI X-6981. FY77, shallow to very shallow tangential section illustrating typical aperture outline (arrow a), extension | of aperture into fenestrule (arrow b) in shallow view causing inflection in fenestrule outline, incomplete peristome (arrow c) | open at proximal to proximal-adaxial edge (arrow d), keel (arrow e), and nodes (arrow f) positioned atop keel, x 70. 2-5. Holotype, UI X-6987. 2. AI28, mid shallow to deep tangential section. Note typical autozooecial chamber outline in mid tangential view (arrow a), chamber outline in deep section near reverse-wall budding-site (arrow b), and longitudinal striae (arrow c) comosed of granular skeletal material which is continuous with reverse microstylets (arrow d), x 40; 3. AI40, shallow | to very shallow tangential section illustrating chamber outline in shallow tangential view (arrow a), lamellar skeleton plugging aperture (arrow b) exhibiting expanded peristome, longitudinal ridge across dissepiment (arrow c), keel (arrow d), and node (arrow e) developing atop keel, x 70; 4. AI40, shallow to deep tangential section showing typical mesh symmetry of this species. Note site of branch bifurcation (arrow a) and fenestrule partially plugged by lamellar skeleton (arrow b). Such plugging is common | in mesh near axis, x40; 5. AI40, mid tangential section illustrating heterozooecia (ovicells?) consisting of lamellar skeleton i partially infilling fenestrule (arrow a) with perforation (arrow b) in center of infilling, x70. | 6. Paratype, UI X-6989. AI91, transverse section of central axis illustrating sinistral spiraling of axial section. When viewed toward distal end of axis, if lateral branches develop to the left of central axial branch (arrow a), spiraling is sinistral. Zoarial mesh flattens toward edge of spiral into tangential view showing aperture openings (arrow b) and fenestrules (arrow c) typical of this orientation. Note thick lamellar skeleton forming central spiral axis, x 20. 254 Figure 1-10. Fonestralsesanchindovier A Hote ae eq SRI EN ee An Wa Ree ee ame ehe HUE f. 2-10. PALAEONTOGRAPHICA AMERICANA, NUMBER 57 EXPLANATION OF PLATE 63 Page 138 Holotype, ISGS (ISM) 4486-1, obverse exterior surface of zoarial fragment exhibiting slight ontogenetic thickening and moderately poor preservation. Note fenestrule (arrow a) and variation in fenestrule outlines, longitudinal ridge across obverse dissepiment surface (arrow b) and site of branch bifurcation (arrow c), x18. Paratype, ISGS (ISM) 4486-2. Large, moderately ontogenetically thickened zoarial fragment. 2. Obverse exterior surface illustrating thickened lamellar skeleton covering apertures (arrow a), causing thickening of keel (arrow b) and partially covering both keel and nodes (arrow c). Note zoarial support developed at lateral edge of zoarium (arrow d), x18; 3. Side view of obverse exterior branch surface illustrating orientation of adaxial (arrow a) and abaxial (arrow b) autozooecial apertures across branch surface; also note keel (arrow c), and nodal (arrow d) development atop keel, x 35; 4. Reverse exterior zoarial surface showing site of branch bifurcation (arrow a) and microstylets (arrow b) across reverse zoarial surface, x18; 5. FSL89, deep longitudinal section near center of branch, obverse to left, illustrating adaxial chamber outline (arrow a) in this view, abaxial chamber (arrow b) budding from edge of adaxial chamber, and granular skeletal layer (arrow c) continuous around autozooecial chambers, and with reverse microstylets (arrow d), x 70; 6. FSL41, shallow longitudinal section, obverse to left, showing reverse (arrow a) and obverse (arrow b) ends of abaxial autozooecial chambers, x 70; 7. FSL48, shallow to mid longitudinal section, obverse to right, illustrating typical abaxial chamber outline in mid longitudinal view (arrow a) capped by terminal diaphragm, and abaxial chamber outline in shallow longitudinal view (arrow b), x 40; 8. FSL33, transverse section showing mid axial wall (arrow a) separating adaxial autozooecia, abaxial two rows of chamber axial walls (arrow b), and granular skeletal layer (arrow c) continuous around autozooecial chambers, and with reverse longitudinal striae (arrow d), microstylets (arrow e), and obverse nodes (arrow f), x 70; 9. FSL86, transverse section showing terminal diaphragm (arrow) capping adaxial aperture that exhibits typical attitudinal relationship to plane of obverse surface, x 70; 10. FSL89, transverse section illustrating attitudinal relationship of adaxial (arrow a) and abaxial (arrow b) apertures relative to plane of obverse surface; also shown is continuity of granular skeletal layer across dissepiment (arrow c) between branches, x 70. PALAEONTOGRAPHICA AMERICANA, NUMBER 57 PLATE 63 PLATE 64 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 MISSISSIPPIAN BRYOZOANS: SNYDER 255 EXPLANATION OF PLATE 64 Figure Page | owe Fonestralidisdnotiludoviorbroutal8o Sante ees Hu a ASE EA Berne 138 Paratype, ISGS (ISM) 4486-2. 1. FSL75, mid to shallow tangential section illustrating mid axial wall (arrow a) and abaxial wall (arrow | b) exhibiting typical appearance in this view, rectangular to slightly parallelogram-shaped outline of autozooecial chambers in mid | tangential view (arrow c), outline of abaxial chambers in shallow tangential view (arrow d) and abaxial aperture opening (arrow e), and short superior hemiseptum at proximal edge of vestibule (arrow f), x 70. 2. FSL75, shallow to deep tangential section illustrating } adaxial autozooecial chamber outline in mid (arrow a) and shallow (arrow b) tangential views, site of branch bifurcation (arrow c) and chamber outline at that site, and longitudinal striae (arrow d) continuous with granular skeletal layer surrounding autozooecial | chambers and extending across dissepiment (arrow e), x 20; 3. FSL81, mid to mid shallow tangential section illustrating mid axial wall (arrow a), mid shallow adaxial chamber outline (arrow b), and inflection into fenestrule opening of abaxial apertures (arrow c), X60; 4. FSL27, node with central core of granular skeletal material (arrow), x 70; 5. Obverse exterior view of well-preserved zoarial surface illustrating adaxial (arrow a) and abaxial (arrow b) attitudinal relationship of aperture relative to branch surface, keel (arrow | €) with nodes positioned atop, and small obverse stylets (arrow d), x45; 6. FSL86, very shallow to shallow longitudinal section, \ obverse to left, showing chamber outlines in this view, attitudinal relationship of aperture to plane of obverse surface (arrow a), and continuity of granular skeleton across dissepiment (arrow b), x 70; 7. FSL80, shallow tangential section at site of branch bifurcation illustrating thin peristome surrounding aperture (arrow a), and short superior hemiseptum at proximal edge of aperture opening (arrow b), x70; 8. FSL27, shallow tangential section showing thick keel (arrow) covered with lamellar skeletal material atop which nodes with granular skeletal cores occur, x 20. 256 Figure ee ae de Le Gly cooled o A C BR T ER eee A an HE E ER MT TOU Pca. PALAEONTOGRAPHICA AMERICANA, NUMBER 57 EXPLANATION OF PLATE 65 1, 3-9. Figured specimen, UI X-6919. Large, well-preserved zoarial fragment. 1. Obverse exterior surface illustrating aperture (arrow a) surrounded by apertural stylets, intermediate-size stylets (arrow b) anastomosing around apertures along obverse branch surface, extensions of apertures into fenestrule causing inflection in fenestrule outline (arrow c), site of branch bifurcation (arrow d), large stellate node (arrow e), and longitudinal ridges across dissepiment obverse surface (arrow f), x 8; 3. POS6, mid to deep longitudinal section, obverse to left, illustrating granular skeletal layer (arrow a) continuous around autozooecial chamber and with macrostylets (arrow b), x 40; 4. PO51, transverse section showing two branches separated by fenestrule opening (arrow) filled with sediment, x40; 5. POS6, mid to deep longitudinal section, obverse to left, illustrating typical chamber outline (arrow a) with aperture opening toward middle of branch, edge of more laterally positioned chamber (arrow b), peristome continuous with apertural stylets, and all connected with inner granular skeletal layer (arrow c), and obverse node (arrow d), x 70; 6. PO56, shallow to mid longitudinal section, obverse to left, showing autozooecial chamber exhibiting typical outline in mid longitudinal view (arrow a), edge of chamber near reverse-wall budding-site (arrow b), and well- developed obverse stylets (arrow c) continuous with inner granular skeleton, x 70; 7. PO4, shallow to deep tangential section illustrating typical adaxial chamber outline in mid tangential view (arrow a), abaxial chamber outline in mid tangential view (arrow b), and chamber outline near reverse-wall budding-site (arrow c). Note aperture position at site of branch bifurcation (arrow d), longitudinal ridges across obverse dissepiment surface (arrow e) and large fenestrule (arrow f), x20; 8. POS, transverse section showing attitudinal relationship of adaxial (arrow a) and abaxial (arrow b) aperture openings to plane of obverse surface, and obverse node (arrow c) continuous with inner granular skeletal layer, x 70; 9. PO56, mid shallow longitudinal section, obverse to left, illustrating chamber outline in this view (arrow a), and apertural stylets (arrow b), x 70. . Figured specimen, UI X-6920. Enlarged obverse and reverse surfaces of a zoarial fragment exhibiting pronounced ontogenetic thickening. Shown are longitudinal striae (arrow a) extending along reverse branch surface and across dissepiment (arrow b), and macrostylets (arrow c) developed atop reverse longitudinal striae. Note aperture (arrow d) plugged by lamellar skeleton added during ontogenetic thickening, x 30. PALAEONTOGRAPHICA AMERICANA, NUMBER 57 PLATE 65 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 PLATE 66 Figure 1-4, MISSISSIPPIAN BRYOZOANS: SNYDER 257 EXPLANATION OF PLATE 66 Polypora gracilis Prout, 860. va ER orc Nus ee a ge a a a a Ta 144 Figured specimen, UI X-6919. 1. PO4, shallow tangential section showing peristome surrounding aperture (arrow a), with peristomal projections expanding outward to become apertural stylets (arrow b), and intermediate-size stylets (arrow c) developed across obverse surface, x 70; 2. POS, transverse section showing granular skeletal layer continuous around autozooecial chambers (arrow a), with reverse macrostylets (arrow b), and apertural stylets (arrow c), x 70; 3. PO4, deep tangential section showing longitudinal striae (arrow a) of granular skeletal material, macrostylets (arrow b) developed as extensions of these striae and as extensions of striae extending across dissepiment (arrow c), x 70; 4. PO18, mid shallow to shallow tangential section. Note increased angularity, to accomodate fit into available space, of autozooecial chamber going from shallow (arrow a) to mid shallow (arrow b) tangential view, x 40. . Polypora varsoviensis Prout, 1858a .....i cesse ehh hehehe ener 146 5. Figured specimen, UI X-7022. Obverse exterior surface of moderately ontogenetically thickened zoarial fragment containing numerous apertures capped by centrally thickened terminal diaphragms. Note extension of apertures into fenestrule openings and onto edge of dissepiment (arrow), x8. 6-12. Figured specimen, UI X-6907. Large, well-preserved zoarial fragment. 6. Obverse exterior surface showing centrally thickened terminal diaphragm (arrow a) capping aperture, aperture not capped by terminal diaphragm (arrow b), obverse node (arrow c), and pronounced branch thickening proximal (arrow d), and thinning distal to site of branch bifurcation, x8; 7. Reverse exterior surface illustrating longitudinal striae (arrow a) atop which develop reverse microstylets, macrostylets (arrow b) typically located at site of branch-dissepiment junction, branch thickening proximal to site of branch bifurcation (arrow c), and zoarial support (arrow d) developed from reverse branch surface, x8; 8. PO90, transverse section showing typical attitudinal relationship of aperture to plane of obverse surface and part of centrally thickened terminal diaphragm (arrow), x 70; 9. PO90, transverse section of two branches immediately distal to site of branch bifurcation. Note attitudinal relationship of adaxial (arrow a) and abaxial (arrow b) apertures relative to plane of obverse surface, granular skeletal layer surrounding autozooecial chambers (arrow c) and continuous with longitudinal striae (arrow d), x 70; 10. PO80, mid shallow to shallow longitudinal section, obverse to left, showing aperture opening at abaxial branch edge (arrow a) and mid chamber outline of abaxial autozooecial chamber (arrow b), x 40; 11. PO82, deep longitudinal section, obverse to left, showing chamber outline in this view (arrow a) and near reverse-wall budding-site (arrow b), also note aperture opening onto branch center (arrow c), x40; 12. PO82, mid longitudinal section, obverse to left, illustrating typical autozooecial chamber outline in this view (arrow a) as well as continuity of granular skeletal layer along reverse wall (arrow b), and with reverse macrostylets (arrow c), x40. PALAEONTOGRAPHICA AMERICANA, NUMBER 57 EXPLANATION OF PLATE 67 Figure 1-0. POU PONE VAVSOVICTISISM LOM ROO OR... ec ee en i PR tee IRR oy erate NOR ee ee 1. Figured specimen, UI X-7022. Enlarged obverse exterior surface of well-preserved zoarial fragment illustrating typical outline of aperture (arrow a), obverse node (arrow b), and ridge across dissepiment surface (arrow c), x 20. 2-6. Figured specimen, UI X-6907. 2. PO77, mid to deep tangential section showing adaxial autozooecial chamber outline near reverse-wall budding-site (arrow a), adaxial chamber outline in mid tangential view (arrow b), and abaxial chamber outline in same view (arrow c). Note longitudinal striae composed of granular skeletal material (arrow d), and microstylets developing as extensions of striae along branch (arrow e) and dissepiment (arrow f) surfaces, x 20; 3. PO80, mid to shallow longitudinal section, obverse to left, showing typical abaxial autozooecial chamber outline in this view (arrow), x 70; 4. PO83, shallow tangential section illustrating peristome surrounding aperture that exhibits a typical apertural outline (arrow a), apertural stylets developed atop peristome (arrow b), and obverse node (arrow c), x 70; 5. PO87, mid to mid shallow tangential section showing typical autozooecial chamber outline in mid (arrow a) and mid shallow (arrow b) tangential views, also note continuity of granular skeletal material across dissepiment (arrow c), x40; 6. PO87, shallow to mid tangential section. Note inflection in fenestrule outline caused by extension of apertures into opening (arrow a) in shallow tangential view and lack of such inflections in mid tangential view (arrow b); also shown is recessed dissepiment near obverse surface (arrow c) with continuity of dissepiment evident between branches in mid tangential section (arrow d), x 20. T, SC POD N RW CO ee A Las: cas e aa 149 Figured specimen, UI X-7017. PA43. 7. Transverse section showing attitudinal relationship of abaxial (arrow a) and adaxial (arrow b) apertures relative to plane of obverse surface; also shown is granular skeletal layer continuous with peristome (arrow b). Note granular skeletal layer surrounding autozooecial chambers and continuous with longitudinal striae (arrow c) and reverse microstylets (arrow d), x40; 8. Transverse section illustrating centrally thickened terminal diaphragm capping aperture (arrow a), and continuity of granular skeletal material across dissepiment between branches (arrow b), x40. PLATE 67 PALAEONTOGRAPHICA AMERICANA, NUMBER PLATE 68 b 1-3 x iek et MISSISSIPPIAN BRYOZOANS: SNYDER 259 EXPLANATION OF PLATE 68 Figure Page ID PO POV asp ININOGALGRO Ghia RS te a ee ee T ML oca 149 1, 11, 12. Figured specimen, UI X-7017. Large, moderately ontogenetically thickened zoarial fragment. 1. Obverse exterior surface illustrating centrally thickened terminal diaphragm capping aperture (arrow a) at thickened branch area proximal to site of branch bifurcation, pronounced extension of apertures onto dissepiment surface (arrow b), and nodes (arrow c) along obverse branch surface, x 8; 11. PA41, greatly enlarged longitudinal section, obverse to right, illustrating centrally thickened terminal diaphragm (arrow a) with granular skeleton forming inner apertural plug (arrow b) apparently continuous with | inner granular skeletal layer (arrow c). Note thickened lamellar skeletal material (arrow d) infilling area between zones of granular skeleton, x 200; 12. Reverse exterior surface showing typical fenestrule outline (arrow), x8. 2, 3. Figured specimen, UI X-7018. 2. Reverse exterior surface containing branch exhibiting pronounced thickening proximal (arrow a) and thinning distal to site of branch bifurcation, longitudinal striae and microstylets developing atop striae (arrow b), and reverse zoarial support (arrow c) forming on reverse surface near site of branch bifurcation; x8; 3. Obverse exterior surface illustrating aperture not capped by terminal diaphragm (arrow a), and extension of abaxial aperture opening (arrow b) into fenestrule opening, x8. 4, 6. Figured specimen, UI X-7019. 4. Reverse exterior surface showing macrostylet development (arrow) typically at site of branch-dissepiment junction, x8; 6. PO68, transverse section. Note attitudinal relationship of abaxial (arrow a) and adaxial (arrow b) autozooecial chambers, both capped by centrally thickened terminal diaphragms, to plane of obverse surface; also note well-developed longitudinal striae of granular skeletal material (arrow c), and spacing between branches (arrow d) across fenestrule opening, x40. 5, 7-10. Figured specimen, UI X-6921. 5. PA21, shallow longitudinal section, obverse to right, illustrating aperture extending intc fenestrule in shallow longitudinal view (arrow a), and continuity of granular skeletal material across dissepiment (arrow b), x40; 7. PA21, transverse section of dissepiment, obverse to right, showing continuity of granular skeletal material (arrow) through middle of dissepiment, x40; 8. PA23, mid to deep longitudinal section, obverse to right. Note granular | skeletal layer continuous around autozooecial chambers, with reverse chamber wall (arrow a) and reverse microstylets (arrow b); also shown is edge of obverse node (arrow c), x40; 9. PA26, mid longitudinal section, obverse to right, illustrating typical chamber outline in this view (arrow a) and centrally thickened terminal diaphragm capping aperture (arrow b), x40; 10. PA26, mid to deep longitudinal section, obverse to right, showing variable chamber outline (arrows a and b) toward center of branch, and continuity of granular skeleton with peristome (arrow c) and with large reverse macrostylets (arrow d), x40. 260 Figure t7 Popma SEPIEHDUAUEL Uca Ss IO 45 a a ran a Ge fo re a Pe ac M CN den 149 1-3, 7. 4,5. 8,92 Polypora simulain Ulrich, 18901 00.2... 2050. udn oc te en ign AAG Heer oh do nus rap en 151 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 EXPLANATION OF PLATE 69 Figured specimen, UI X-6921. 1. PA31, shallow to deep tangential section showing typical mesh symmetry. Note extension of aperture into fenestrule in shallow tangential view causing inflection in fenestrule outline (arrow a), lack of such inflections in mid tangential view (arrow b), and pronounced increase in fenestrule size, particularly width, near reverse wall (arrow c), x20; 2. PA31, shallow to mid tangential section showing abaxial autozooecial chamber outline in mid (arrow a) and mid shallow (arrow b) tangential views, and site of branch bifurcation (arrow c), x 20; 3. PA29, very shallow tangential section illustrating typical aperture outline (arrow a), peristome surrounding aperture (arrow b), apertural stylets (arrow c) developing at lateral edge of peristome, and stellate nodes (arrow d) along obverse zoarial surface, x 75; 7. PA21, shallow to mid shallow longitudinal section, obverse to right, showing aperture opening into fenestrule at abaxial branch edge (arrow a), and diaphragm capping aperture in shallow longitudinal sectional view (arrow b), x40. Figured specimen, UI X-6913. Highly ontogenetically thickened zoarial fragment. 4. PO69, mid to deep tangential section showing continuity of granular skeletal material with reverse macrostylets (arrow a), and lamellar skeleton covering macrosty- lets in deeper tangential view (arrow b). Note macrostylet location near site of branch-dissepiment junction, x25; 5. PO74, shallow to mid tangential section illustrating typical adaxial (arrow a) and abaxial (arrow b) chamber outline in mid tangential view, adaxial (arrow c) and abaxial (arrow d) aperture outlines, continuity of granular skeleton across dissepiments (arrow e), and thickened lamellar skeletal layer (arrow f) partially filling fenestrules inside which microstylets develop, x25. . Figured specimen, UI X-7017. PA47, mid to deep tangential section of slightly ontogenetically thickened zoarial fragment showing typical chamber outline near reverse-wall budding-site (arrow a), longitudinal striae (arrow b) continuous with granular skeletal layer from which reverse microstylets (arrow c) and macrostylets (arrow d) develop, x 20. Figured specimen, UI X-6922. 8. PI43, mid shallow longitudinal section, obverse to right, showing typical autozooecial chamber outline (arrow) in this view, x 20; 9. PI27, transverse section of branch showing abaxial (arrow a) and adaxial (arrow b) attitudinal relationship of aperture to plane of obverse surface. Note continuity of granular skeletal material with peristome (arrow a) and apertural stylets (arrow b), x60. 10. Polypore spinmodam Ulrich; 1890.7. o tie ee ie o eere nn eee ia Te DN te eas 149 Figured specimen, UI X-6911. PO49, shallow tangential section illustrating apertural stylets (arrow a) and extension of apertures onto dissepiments (arrow b), x40. ) I \ PLATE 69 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 PLATE 70 MISSISSIPPIAN BRYOZOANS: SNYDER 261 | EXPLANATION OF PLATE 70 | Figure Page | l=12, Polypora simular 18908 a ee e ee ee Bea age a ee ARM oie o ADO EOS 151 | Figured specimen, UI X-6922. Well-preserved, moderately large zoarial fragment. 1. Obverse exterior surface showing aperture | position at site of branch bifurcation (arrow a) and longitudinal ridges extending across dissepiment (arrow b), x15; 2. Obverse exterior surface; note typical outlines of adaxial (arrow a) and abaxial (arrow b) autozooecial apertures, both capped by centrally thickened terminal diaphragms and surrounded by apertural stylets, and stylets (arrow c) occurring between and anastomosing around apertures and nodes, x15; 3. Obverse exterior surface illustrating adaxial aperture (arrow a) surrounded by apertural stylets and not capped by terminal diaphragm, and obverse node (arrow b), x15; 4. PI37, shallow mid longitudinal section, obverse to right, showing centrally thickened terminal diaphragm (arrow a) and granular skeletal layer (arrow b) continuous with reverse wall, around autozooecial chambers, and with reverse microstylets, x60; 5. PI35, transverse section of zoarial support illustrating core of granular skeletal material (arrow) continuous with small stylets at edge of support, x 60; 6. PI35, transverse section of dissepiment, obverse to right, showing aperture opening onto edge of dissepiment (arrow a), and continuity of granular skeletal material across middle of dissepiment between branches (arrow b), x60; 7. PI35, mid longitudinal section, obverse to right, illustrating typical autozooecial chamber outline in this view (arrow a), and continuity of granular skeletal layer with peristome (arrow b), x40; 8. l PI35, very shallow to shallow longitudinal section, obverse to right, showing changing autozooecial chamber outline from very shallow (arrow a) to shallow (arrow b) longitudinal view, x60; 9. PI29, transverse section of branch showing typical attitudinal | relationship of adaxial aperture to plane of obverse surface (arrow a), and zoarial support with core of granular skeletal material (arrow b) extending from reverse branch surface, x 60; 10. PI44, mid to deep longitudinal section, obverse to right, showing typical | chamber outline in deep longitudinal view (arrow a), and obverse node (arrow b) of granular skeletal material, x40; 11. PI45, mid longitudinal section, obverse to right, showing typical chamber outline in this view (arrow) with aperture capped by diaphragm, | x 40; 12. PIA5, shallow to mid longitudinal section, obverse to right, showing adaxial edge of apertural stylets (arrow), x 40. 262 Figure 1-4. 5-9 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 EXPLANATION OF PLATE 71 P p SUT O Ardua. EE EU Eo O maine I Ru. Uno ege nein dedere 151 Figured specimen, UI X-6922. 1. PI48, shallow to deep tangential section illustrating typical outline of adaxial chambers in mid (arrow a) and shallow (arrow b) tangential view, abaxial chambers in mid (arrow c) and shallow (arrow d) tangential view, continuity of granular skeleton across dissepiment (arrow e) and site of branch bifurcation (arrow f), x 20; 2. PI32, mid shallow tangential section showing chamber outline in this view (arrow), x60; 3. PI48, shallow tangential section illustrating aperture surrounded by apertural stylets (arrow a), and obverse stylet (arrow b) and nodal (arrow c) development, x60; 4. PI48, deep tangential section showing chamber outline near reverse-wall budding-site (arrow a), and granular skeletal layer continuous with longitudinal striae (arrow b), and microstylets (arrow c) developing atop and as extensions of striae (arrow c), x 60. Leto Ver m: UIriohe GO Sr oes ee UR Md ERES ed ce 82 vd EN ETE CP IERI Ca d t ton eti ote nime es rd tds 154 Figured specimen, UI X-6908. 5. Enlarged obverse exterior surface showing autozooecial aperture (arrow a) exhibiting slight inflection into fenestrule, aperture (arrow b) developed well onto edge of dissepiment, and site of branch bifurcation (arrow c), x 20; 6. PI17, mid longitudinal section, obverse to left, illustrating typical autozooecial chamber outline in this view (arrow a), and thick granular skeletal layer continuous around autozooecial chambers, with reverse wall (arrow b) and reverse microstylets (arrow c), x 40; 7. PI21, mid longitudinal section, obverse to left. Note typical autozooecial chamber outline in this view (arrow a), and continuity of granular skeletal layer with obverse stylets (arrow b), x 70; 8. PI63, transverse section illustrating zoarial base (arrow) from which colony developed and in which is contained the ancestrula of this zoarium, x 20; 9. Obverse exterior surface showing typical aperture outline (arrow) with aperture surrounded by incomplete peristome and containing apertural stylets, x 20. PLATE 71 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 PLATE 72 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 MISSISSIPPIAN BRYOZOANS: SNYDER 263 EXPLANATION OF PLATE 72 Figure Page lESERPOIVporasTetrorsa WEICH ee SO Uae M A UNDER Me D cc M 154 Figured specimen, UI X-6908. Large, moderately complete, well-preserved zoarial fragment. 1. Reverse exterior surface illustrating typical fenestrule shape as observed from reverse surface (arrow a), site of branch bifurcation (arrow b), and base of zoarium (arrow c) containing ancestrula, x1; 2. Obverse exterior surface illustrating slight inflection in fenestrule outline caused by extension of abaxial aperture edge into opening (arrow a), thickening of lamellar skeleton at proximal end of zoarium completely plugging fenestrules (arrow b), and site of branch bifurcation (arrow c), x1; 3. PI21, mid to deep longitudinal section, obverse to left, showing typical autozooecial chamber outline in mid longitudinal view (arrow), x40; 4. PI8, transverse section showing attitudinal relationship of adaxial (arrow a) and abaxial (arrow b) apertures to plane of obverse surface. Note thickened granular skeletal material around autozooecial chambers, and rounded chambers (arrow c) in transverse section, x 40; 5. PI6, transverse section showing continuity of granular skeletal layer (arrow a) around autozooecial chambers, with reverse microstylets (arrow b), and across dissepiment (arrow €) between branches, x 40; 6. PI67, shallow to mid shallow tangential section illustrating incomplete peristome surrounding aperture that exhibits a typical outline (arrow a), apertural stylets (arrow b), and obverse stylets (arrow c), x40; 7. PI67, deep mid to mid shallow tangential section showing typical bilobate chamber outline in mid shallow (arrow a) and ovate outline in mid (arrow b) tangential views. Note pronounced extension of autozooecial chambers onto dissepiment (arrow c), and rounded chamber shape (arrow d) in deep mid tangential section, x40; 8. PI62, mid to deep tangential section illustrating autozooecial chamber outline near reverse-wall budding-site (arrow a), and poorly defined longitudinal striae (arrow b) of thickened granular skeletal material which expands outward to become reverse microstylets (arrow c), x40. INDEX Note: Page numbers are in light face; plate numbers are in bold face type; pages on which principal discussions occur are in italics. F and B indicate the foldouts inside the front and back covers, respectively. AAB [distance between aperture centers across branch] D ou c Sage S ee Sic M de eere E illustrated ABB [distance between aperture centers between branches] UU RS ES ut epe e HM en BO cM Ep SO AA F,B E ee AR AS E RUC ERRARE QU Ee ree 35 Di iio qu 2) fuse oa t MS NNNM N MN 156 ACA [angle between distal end of axis and axial whorl] Dispo. ud com ub ccce D MA eS PN S 8 ue ANE F,B dol o T E e A E O AN illustrated Aequifenestella Vermmer and Termaer, LITE... ne... 23 AF [number of aperture openings per fenestrule length] RR N iS oon Gers er REQUE PE EE ON MEIN So oodd Afghanistan AL [aperture length] cogo eM com Pr A nn e do ho F,B MORSU Eu un e UR CERE Vere RE SE CLER E INTO CRE EE 2337 39 Alternifenestella Termier and Termier, 1971 .................... 23,24 AMNH [American Museum of Natural History, New York, NY] vocor ud MEM clc sene n o Auto c $m 40,133 angle between distal end of axis and axial whorl [ACA] Ne ESPERAN bah caus age cr o dbi NNNM: Conde reu "cuui. NEU I TER D Oo y certain NS Ammeg mud Perry (19 70) E A e Anstey and Perry (1973) .... EPO CHO OU ee oc s Din AA QM Apostostella, W. Sel. nennen 7,29-31,33,34,39,40,90,97, 98,101,103,106,108,124 crasso, Me ID. Lees cce ree 306,37 wa 7,39,97,98,101,102— 104,156,158,159,227,228 foramenmajor, n. SP. ................ 3536 ..... 7,39,98,99,101, 156,158,226,227 VORDSEA YR SD wenn 4839 em 7,39,98,104,106, 156,158,159,229,230 aperture length [AL] UC orm. cbe | ARE teenie MBER re F,B OUPTOIG ARI TEIL O E 35,57,9 aperture width [AW] defined ......... illustrated Appalachian Revolution C ie ore occu see rec vo cepe v ve ceu EXER E corse L5 Appalachian State University, Boone, NC ............... eee 2i aprilüe, CAIDO eee GAAS nta 7,39,108,114,116, 156,158,159,235,236 Arehaefenesiella Miller, 1962. ........ u nen ese 23,24 Archimedes Hall, 1858 ............... F,18,27,29-31,33,34,36,39,40, 54,56,122124,127,133,136 distans Comer andas, 1944-5... uices oret recen 126 Bras DIOS 1890 Lie ences vs E en rne 124,127,130 Ball Conelra and Elias, 1944 N. een 27130 mieekanus Condra aud Elías, 1944 s. ireira enerett, 126 negligens Ulrich, 1890 ........ 30.5152 oc. 39,124,125-127, 156,158,159,241-243 owenanus (Hall, 1857b) ........... 52,53,54,55,56 _...... 39,124, 127,130,133,136,156,158,159,243-247 tevensa Mall ESOS ee EE edo a 124,130,133 terebriformis Condra and Elias, 1944 norssi 126 valmeyeri, de SDE eder eie 60,61,62 ...... 7,39,124,133,134, 136,156,158,159,251-253 weler Condra and Elias, 1944. nn... een 130,133 wortheni (Hall, 1857b) ........ 56,57,58,59,60 ...... 39.7122 124,127,130,131,133,156,158,159,247-251 ARCHIE CRMC STONE: errer ae een seinen 124 Arrow Rock 124.000! quadrangle (1971) un... 176 aspera, LCI VDE SU S tae ne 46,47 ..... 39,108,116,117, 119,156,158,237,238 ASUOVd and Morozova (1990) erret ETE e cone 16,39 Atherton PANO 01979). 1o eere ederet EET A 10-12,158 ¡Augustaivomiwest docality Di... een 9,172 Ausich (1978) 168,169 Ausich (1980) 160,168,169 AUS hie AA sn EE SE PEE ices Bs A T EOT 22,01 autozooecial chamber depth [CD] Yi auf Tao E e RA ER es e E F,B VPN A q p c E Sv RA ee 37,38 autozooecial chamber length [CL] ANA c eM SS OA I EAE ee F,B ULSA Lr N todo CR Mgr Coe 37,38 AW [aperture width] doe fol oe pce pU UP EC Ur MS DET Pema UR illustrated b y capu exe Co en MIO I EA E en que Bonasielid W AA 7,28,30,32,34,39,40,68,71,72,73, 76,79,81,83,85,88,141,151 biseriata (Ulrich, 1890)... 5 sss 26127. cs 39,73,83,84, 85,156,158,159,217,218 cingulata (Ulrich, 1890) ............ O s 39,73,77,78,79, 83,156,158,211,212 delicata, meae o LLR. 2... 7,39,73,86,88,156,158,218,219 guensburgi, n. sp. ..... 18,19,20 .... 7,19-21,37,39,72,73,74, 76,83,156,158,159,166,209-211 limitaris (Ulrich, 1890) ............. DAS ur. 39,73,81,82,83, 156,158,159,215,216 mediocreformia, N. SP ... vices. asa fos PIE seats 7,39,73,79,80, 81,83,156,158,213,214 pa3nototb Do dde ee ee ROO 292232 Panero ISO. nee en N sh 2 Banta, McKinney, and Zimmer (1974)... eese con etanol 166 Basslet OLD e o m la E e ARE 16,17,22,142 BASE A cem TEE EUNT aie 14 Baer 6191720 Con oce Wiss O re E Ub eda E EE SEI 11 BASE EIA C Ber. ae EO cates EAS eL E 14 BER CLS SW) cea cs Chas os sts «os OS eed DOR a cbe EPA dS EIE 15 Beltrees-Melville Anticline norrir iarri 15:16 Benchmark on State Highway 369 (locality 33) ................ 9,175 Bentonsport, Iowa (locality 2; measured section 1) ....................-- a nance ums M UE 9,157-159,172,177 MISSISSIPPIAN BRYOZOANS: SNYDER 265 biseriata, ho teas oO ee s 11,14 Ion ast elg Serii ine 26:2 c res 39,73,83,84,85, Chronic APIO) rec 22 156,158,159,217,218 Cincinnati Arch-Nashville Donk: 10 T RECRUIT cingulata, Blake (1975) Banastella ... 20,21 ...... 39773,77118;79:83/156,158,211:212. Blake (1980) PENE ser een I MINES I x deis ERE 71 Blake (OSB). ns CL [autozooecial chamber length] BKE D -B runs dead E DD E T eas M aun Boardman (1975) AT AAA AA tian EIS Boardman and Cheetham (1969) ............ eese 223A CASIO RE aM coo aeta ure eid e. Boardman and Cheetham (1983)... PREISE 22 Collinson (1964) a RE: A Mc c c MM 10 Collinson, Scott, and Rexroad (1962) HS OAT GLEN EAT E ies NO DUM A EROR 7,18 Columbia Roadcut (locality 48; measured section 22) ................. Bonaparte ico 000 quadtancle (1968) ctr cette y” Ee nice ER ERN E EO 9,157-159,176,183 Borde ee MA Coltmbiais yace a 2er 16 Borden Siltstone Formation ocn common. (defined). era nasser 156 NA ice eee een een compressa, Fenestella .......... E UN Sea ee ee 97 A A BE eee Gondrasand) Blias\(94 4) ation ec en Bork and Bey 96e souche ava O O e ee rs 17,18,41,45,47,56,124,126,127,129,130,133 Piers (ISP e cred corre A ee coniunctistyla, Laxifenestella .......... 5:007 0 7,39,49,50,52, branch width [WB] 53,56,156,158,196-198 CELT RM RE TEN F,B Connell (19/75 soa retenu ni mno PER 160 CUSTER ED ee ae ee LT. DEN 39,90% sk COOK (197 7) ei ctrca dte BO eae coe Re 22,166 Barner 58) bd ana TERI. MR tueri o a County Road (locality 42). A... en e 9,175 Briggs Branch (logalitys 37) io. METER Pn Cragwold Road (locality 47; measured section 21) ...................... Brighton 1: 62:500:guadrangle«(1925)3 TE TI -— Poco been 9,56,58,72,79,95,97,111,136,149,157-159,176,184 DUB rancho „ea Das Kei bueno lr Crassata; Apertostellas aos 36,370— 2*4 7,39,97,98,101, Buel Branch (locality 14; sacha section 9) 102-104,156,158,159,227,228 ira FERN TRUE 9,157-159,173,180 erawfordsvillensis, DitiyOClOstus:.c; cuite i2 EEUU FATTER ok ee ne RR T 162 GPisImeburnea Lamouroux, 1812 2a aan. nee 163 Bullivant (1968a) 161,162,164 Crockford 494.2. 22.22 22-24,28,30,32,39-41,61,62,65,97 Bullivant (1968b) 160,162,163 Cryptosula pallasiana (Moll, 1803) .......... ee 165,166 Burckle WIRD) e Ems 41,56,127,138 Cubifenestella, n. gen. ........ 7,29-31,33,34,39-41,88,90,92,97,98 Burlington A A e e A 11 globodensata; ny SP: 3.4. 33,34 " 7,39,90,92,94,95, Burlington Limestone Formation ............ ee 10,11,14,88 97,156,158,224,225 Busk (1852) 16 tud (Urien OOO) aaa ar 20:30 uc 39,83,88,90, Butts (1915) 12 92,94,156,158,220,221 usitata dA IS Deer deua er e r 7,19-21,38,39,90,92, Cahokia 1:24 000:-gnadranele (LISA Bins A 176 93-95,97,156,158,222,223 Crai NO De re GUN (LION) E a O Bn eee 19,34 Canton, Missouri—A (locality 17) ... uns (1973) bee sk es ee er ee 16,17 Canton, Missouri—B (locality 18) QUIM Mr M a 175 Canton, Missouri —C (locality 19) Guiver River (locality 39) iii Rn 9,175 Cap au Gres Faulted Flexure a. Cumings (1901) Sa ON Mr NL RR RTI E Cumings (1904) Cenuai re Cumings (1905) Carrollton Anticline Cumings (1906) Carrollton, Illinois MA en ae a: Cumings (1922) Cavernella Morozova; 1974 une CUMS AR e edes tr rianls doce or dadas nea rober scsi a 53 Cavusgnathus unicornis—Apatognathus Zone u... 12 Greloporu Prot 1 SSS aK css ccasdeades E nee 12 CD [autozooecial chamber depth] Epcloporela WiC 589. u. ne 12 CLEP EL NAT E FB AAA A RE OE ROREM E 37,38 BUR Chronic, 1949 nennen ee 02 A ERE 160 Chamber lateral-wall budding-angle [LA] DBC [distance between branch centers] ETC A MED EL Ier EN F,B (LHe e PU E CRORE NUNC War ae ee LUSTRE OUI RM ee N 37,38 illustrated Chamber reverse-wall budding-angle [RA] DCA [maximum diameter of central axis] defined [Ono ae ce URN M UEM cau eei illustrated illustrated Cheetham, A. H poscit Ankolne een LL 15 Chester delicata, Banastella catas 243.28. 0 7,39,73,86,88, Group 156,158,218,219 Nana, Am A O fr A we eae CLE HNO LAG MOD ON Gis P NEN CREEK on 1H 142 266 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 Dennis Hollow at Valmeyer (locality 49; measured section 23) ..... . 9,45,47,49,54,56,58,60,61,65,67,72,76,79,81,88,92,95,97, 114,116,119,136,146,149,156-159,176,185 ieu ss A AENA N E S illustrated diameter of microstylets of reverse branch surface [RSS] A A ER 35 defined defined RICA SA e RU e dod eli F,B El EAS dS TAS ORE EE oed: se F,B diameter of stylets surrounding aperture [SAD] CEG ei N O A ur e Us vd scm rs illustrated Diamond (197E) oneone erii eE Dictyoclostus crawfordsvillensis (Hall, 1858) dissepiment width [WD] UU RE d EL d E eme Ss RAUM. AS VORNE. ER E E No CREME OR HEC TON F,B apa Eee a 35 distance between aperture centers along branch [ADB] E AIC ER O a Tors Nite O cpi illustrated distance between aperture centers between branches [ABB] oue coques E E E E E A F,B TINCT I d Nr A NEE AE T E O RS F,B A APS A A EEEREN E E 35 distance between node centers along obverse branch surface [SNB] O EEE Mo E ETA Winsirated. 2... distans, Archimedes DN [diameter of nodes along obverse branch surface] AA eere area ee F,B O ue dui RE A IO a Car 35 DND [diameter of nodes on dissepiments] ER reise er F,B PRON tus E REN E RIEN c CU 35 Dovaddaneciia Gancsam 1972. na. 22 Tuae Hall Amme- A: score en 15 DSO [diameter of stylets on obverse surface] Re DER DC. ce Luc AD E IM to IA A E UU mon aco COR acco pass AN HM MEM Ur qe Dunaeva and Morozova (1974) COPOS MENUYA eur Ice eese hene ich Dupo Quarry (locality 44) ..................... DUSSER (E964) A A A E N, a A nes) AF 10 eburnea, Crisia PCOS OTE CLO GO) acum cum RN KD tae 160 Ehrenberg (1831) POMBE OAD EN EEE ae Oct es ies and Comdra (1957) 5. nee F,16,18,23,41,56,61,68 NAO GU MILD Ss SAN an een eie odi 15 Engelaco rs Noe eere Engelmann (1847) IF oi 84 nn ol lee Need Mm M P re E «EDODI e s IM e RU LT erkovae, Fenestella .... = AA A E A A E dl e Exfenestela Morozova IITA nee: 23-25,27,28, 30,32,34,39,40,67,68,72 exigua (Ulrich, 1890) .......... 16,17,18 _...... 39,67,68,70-72, 101,156,158,159,207-209 exigua, VAN IIA m ee 16,17.18 5; 39,67,68,70-72, 101,156,158,159,207-209 Fabifenestela Morozova OU A ee 23-25 A ee 163 Family AcanthocladudaeZittel#18 30... ne. 17 Am HO sty Mae Unichi T888 nee ee SMS 17 Diploporidae Vine 1o84 nee era SER TT 107) Fenestellidae King, 1849 ..................... 16,17,29,34,39,40,156 ly phasmopordas Vine, 1884... nee 17 Melicertidae d'Orbigny, 1800 ra ee da 16 Phylloporinidae Dunaeva and Morozova, 1974 16,17 Polyporidae Vine, 1884.2: ee 17,30,34,39,136,156 Rhabdomesöntidae Vine, 1884. 1... ecce 17 Fenestella Lonsdale, 1839 .............. F,17-25,27,40,61,71,85,113 CUL NANA 39 eapite creep eremo NEUE TO dart VIRTU UTD RICH O e (YAT ONCOL AOI DART S SA DRESS TR TOTO CTS erkovae (Shulsa-Nesterenko0, LL) o ne ne Prapa Na an o E exigua springerensis Elias and Condra, 1957 .... Visita LS c eL Ex epa ES CUA UBI OR ee areas Demi pa puo, 1859 u. tomen Ei LOA oii RER OO 1890... ooo E A medvedkensis Shulga-Nesterenko, 1951 ...........................- WwluspitoscaeeicNa9 0... uo Toms rasen ON OWENANG AG ASS D: sn airs cree e cad tote m bea EO READ pianoa Pronin aU ne A regalis Ulrich, 1890 TUAUONINISTENNAS, 1964... Sat. CIERRE DM raon Wehe FORE nee sarytshevae (Shulga-Nesterenko, 1951) .........................0.-- SeratmldWltich: NOS Ose ee Eure stocktonensis Condra and Elias, 1944 .......................... SUDORHQURMEOLDIENY: 1839 tivo ee submicroporata Shulga-Nesterenko, 1952 ...................-- tender em ee tenussı ma: Comings 1900 Ener AS E WOTUHORE ES UBI isis d A A AS T Fenestella Archimedes) Hall 1837D E nee Vier Hall Uis Rr o RI DRACO RITE S TT OL VENESLCLU OF FINISH SYNOI AN een emper enr rare Fenestralia Prout, 18588... ss 27,29-31,33,34,39,137,141 SOUPE INAOVIEH PILOTEN nern eire den Feud ee YU 138 sanctiludovici Prout, 1858a ....... 63,64 ...... 39,137,138,140, 141,156,158,159,254,255 O SOS Aner cov tEn Petr eter mer 138 MISSISSIPPIAN BRYOZOANS: SNYDER 267 e nes alias ancla lU doy CRT ia TREES 138 enesiraporaEredeniks OON e OU VO TOA n OM lal Ord ovata YE en ANLASS ACL) AS ies cesarean LSU GREECE E te ee SAA HENCSTEL ON CS eli ceed Adee ee ea RO ISLA eO RHONE E ee Flabelliporella Simpson, 1895a Flabelliporina Simpson, 1895a Wiesifenestella Morozova, IDA DO OTI 23-25,50 Sluctuata, Laxifenestella ........ TRISTI SrA 7,39,50,53,56,58, 59,60,156,158,159,202-204 Flustrellidra hispida Fabricius, 1780 rna e a 163 Boote: Mineral ome emet HC RALIS I NEL on: 173 foramenmajor, Apertostella ..................—. ISSN 7,39,98, A A enana Fort Payne Formation Frederiks (1915) o A A IN yuca renestela ee 76,94,95 FWT [thickness of front-wall (obverse-wall) laminated layer] GIT CL A SECTOR e M A EE NA CNN cias te. Sen. F,B UIS LOU e recte e os TM CAES ES MI 37,38 Camer NOT A ser A a 22 EUER AUTO) een E hee cca dos AUR 2953] Gens a re TUI 22 Genevieve States andn dS SL LUI DERI dao 11 Geode Glen (locality 11; measured section 7) ted Ate 9:58:72! 85,101,111,114,119,121,122,127,133,148,149,151,153,157- 159,173,179 Ce Ia E S Ie E ARIES SET eu 39 (odes oline siue c e oS LET 15 8lobodensata, Cubifenestella ............... 39:94 Eos. 7,39,90,92, 94,95,97,156,158,224,225 Gnathodus texanus-Taphrognathus conodont Zone of Collinson, Scott, and Rexroad (1962) o... 12) Sordonz@sH..(1895)8 Hi a bec ea 12 SOLIONWIDRPR (IST Ana ner 161 &racilis, JOM OTE. Wace ae 65,66 ..... 39,143,144,146,153,156, 158,15912560:257 BENDER N ch ome tonnes icit ns dia oett NOR 144 SUSE) ROD Or c eee RE 144 ITA, ENA DAUD. E A TRUST 124,127,130 Grays Quarry (locality 9; measured section 5) .............. eene Een SECUS HO SEU OU ae e és 9.1:57715937 259176. ERR Ce assieme ct i RNS SER 7,73 Suensburgi, Banastella ..... 18,19,20 _...... 7,19-21,37,39,72,73, 74,76,83,156,158,159,166,209-211 Hageman (1987) Hageman, S. Hall (1847) Hall (1852) ile, LL a ete AC Hall (1857b) .... 17,39,71,122,124,127,129-131,133,156,243-251 Hall (1858) Hall (1864) Hall (1883) Hall CIS SS) ee E DE REN A NA: halliana, AN A E TETE FE NE Hamilton 1:24,000 quadrangle (1964) Hamilton-Warsaw Roadcut (locality 10; measured section 6) ....... . 9,45,49,54,67,83,92,95,101,104,106,111,114,119,127,130, 151,157-159,173,179 E T need ee menor A La 11 Hardin (OU) dau vrbes eu ode cime ee 160 InE ESAMI C TS T MM CM EU REUS 15 Harris and Parker (1964) ................ 11:172 Harrodsburg Limestone Formation 1112714 Hemiirypa Philips; eB Adie eu spe. oes eco F,23,27,29-31,33, 34,36,39,40,103,106,108,116,119,121,124 CDPHQENIN SD Sae EN re 44,45 ..... 7,39,108,114, 116,156,158,159,235,236 aspera: OIC PSIO 55 da 46,47 ...... 39,.108,116,117, 119,156,158,237,238 hemitrypa (Prout, 1859) ............. 41,42,43 ...... 39,108,111, 113,114,121,122,156,158,232-234 hemitrypamnodulosa Ultich. 1899 SE a ra ee 114 hibernicid:NMoGOoys SA Dar d ren ee 27 MOON LOS TA A E q RE Mee 114 GCHLAIIBHUNPSERBAL. une EM MM ES 106 malenformissulnici 1898 co ee ee A 108,110 perstriata Ulrich, 1890 anne 39,40,41 ...... 39,106, 108,109-111,113,156,158,230-232 DINOS ARETES 113 PROUT Galo TIC, SOO Aa ee a HRT proutanamermijerdsWilnichy: 1890, sus ooo UE a 119,122 vermuera (Ulrich: 1890)... nn 47,48,49 ...... 39,108, 119,120-122,156,158,238-240 hemitrypa, Benesiella sms coa EN EIF TIS RENTA a na a 41,42,43 ...... 39.108,111,113,114, 121,122,156,158,232-234 TIIGOO Vel aD Mec aede T sera o e 7 HopkinssandSiebenthak ID namen re 14 Eiorowitz 1968) een ee 19,34 ROTO WIE CANS catia RS EN Ra 7 Biuichinson. (L959) nenne 160 ED Tas GOS) ices ER . eet ete eae 161,162 Tenoivenestella:Morozoyas 1974: Erna 23,24 Illinois 911073 Adams GO istos añ 14,173,174 AO ss 15,138,141 APPO ae ee N 127 Beirastone tent rennen A Brown oec «e e en = (CHAN lio Us S Qe Mets ee t tee ico te dad MERE. SIE 15 Garp alors dada TRUE AN ER BOAO Tela hears ee (Coupe rior s een ae UR N OPONE (oh role ke a IST ILONA ME PIANC OOS Bora een Geode Cem a als recent 12,14,173 O CO csi b ERR IRR SC UVES ClO Kr eee Mad someone beled ON EE O es McDonough Co. NOTOS hi Alias 16,56,67,68,83,111,138,146,176 Dennis Hollow at Valmeyer ..................s 11,16,47,60 A 83,106,122 268 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 Illinois MUTO LIES LLL 8,56,77,90,116,119,144,146,151,153 Anc Qr. Mem erc E Fat eub ATE E NEAR T EINE utc E E d se TM d DHDSEU CO UID ee A CHE e Dn rs Ui eurer t mu ce ARAA PIRE ALS Ea EA OR A ener cue tO cM Edge Sonata Quarry Hear NAUVOO a... en een. ae ROU a IS EA Re ta ates a En ee aa BERN S ME rere VUELOS DIN eg OG rae te e eo nd nos een Valmeyer .... 8,15,65,72,76,79,81,85,88,95,97,116,133,136,176 ATI dul. 2 ARM Nette dc E AA 174 MNREBRWAR oo oe dese lla 15,56,61,71,83,90,92,101,104,106,111, 119,130,133,138,141,142,144,146,148,149,151,153,173 WERE A e c toe INT UR M e 14 ho, o A TERR LAT RATIS TURA o a RENT, 14,15 Kup an ERE M UE MANU LE EE 15,97,104,136 BIN BINE orte RP TERR ID 10,14,15,88,160,176 Illinois Highway S wv added eus dec edite o EUN A MITT Des Ha I. cd M epe caer erac c een oo e NS E M E TI E HOUR KU park Illinois River Indiana Dark Hollow near DIOOMMNBION ree rererere 39 X (CUS i P, ab rete ed 14 Parodo Dur ooroo eee gies Washington Co., Salem 14 Indiana Umversity, Bloomington, IN... 792 Interstate Route dc gel Rah do a E s SL T ED La ROT 2/00 Vereine Se ee eet A een BR a RE D t o ee EIER RES 15,81,90,106,108,110,116,119,124,126,151,153,172 11514 121215: A A A T 88 e CO, re eel ints a 172 LiL oa c EET SENE E IUE GTP ERR SERI ERES Ur 8 Keule... 9,15,56,67,77,81,83,90,92,101,104,106,108, 110,111,116,119,124,126,127,144,146,151,153,154,156 Lacy Koomugua Park nenn 172 E an po e A e ls TE 23 Sep Creeks atkeokuk ae conci DUNS Pi RG BIETE ic ck r ETE ONION 14 southern 12 eu PU BR een Dean 172 Iowa Terminal (locality 5; measured section 2) .......... ees EDO POLEN UAI EN 9,157-159,173,177 PO CHIC SCI Eu aet outset see 90,92 DINE E GRU ah ray RA ata Seah E NE 18,142 ISGS [Illinois State Geological Survey, Champaign, IL] ............... . 7,8,11,13,40,45,58,83,85,92,111,114,119,122,127,129,130, 133,141,146,151,241-243,247,254,255 ISM [Illinois State Museum, Champaign, IL] ................... 18,40 Jackson and Ciechan 1990) na ae 93 Jersey ville 1-62, 500 quadrangle (1930) 2.2... 2a 173 Po Aa Lae a A AS 47 O MEE CN P E E ee teil 7 REUS nee 12215 Galadwell'COr iore mec coo ror af 56 @rittenden Ca cito ses Nati Lo Re en 56 ms Mountains 65,88,97,144,146 Gc) nik CUn uti tte i s am ee 56 SAS Valley esteso diio nA 56 Keokuk 1:24,000:auadrangle (196450783. ae 179 Keokuk Group ne nn, 11,56,77,81,106,108,110,111,116, 119,124,127,144,148,151,153,154,156 Keokuk Industrial (locality 6; measured section 3) ....................-- PU Ba AS EE unsere 9,127,130,157-159,173,177 Keokuk Limestone Formation .................... arera 11-14,56,67, 73,77,81,83,88,90,92,98,104,106,108,113,116,127,130, 144,149,151,154,156,158-160,163,172-181,183-185 ‚Montrose Ghent Member anne 12 Short crek Oolite Member ua ek 12 Keokuk West (ldealiyv,. 8 errereen An 9,173 RROKU IN AES a rs 12 Kedsatiqua, 1:24.00 quadrangle (1968) en c ecd EE dS 11722 Keyes (1894) ............. 56,77,81,83,90, 108,111,116,127,130,133, 138,146,149,151,154 EEK e E area deines 12,14 NEN FE TOR orca org i REM ain re I NU EMEN 108 RAWSON o add e Dd. 173 do a Sertes nes era 11,138 A A ee e e E OR 17,39,40,156 ASS) me et m eerte e e eee seek TERN 17 Kirkwood 1:24,000 quadrangle (1954)... uses 176 ITO kG rd nas Wee ris eer EE coe PU tn 7 Knight-Jones and Moyse (1961) HOA DIO BI GEO (58 Phase CO Do ee tenes Ses ISO AQ elena oR ra aset aon i deed cente LAS V forie Own meinen RODUEDSERI BEAT erre ere hdd contio d alo il E aire ene EIE 15 La Grange (locality 16; measured section 11): 9v. en ee ubere UE c E T ME LTE ene 9,157-159,174,181 La Grange 124000 quadrangle (1950) ra 174 LA [chamber lateral-wall budding-angle] UE EE Bia A EEE ea, F,B DIS Eee een NO E Ta 37,38 Lacy Keosauqua (locality 3) Lamouroux (1812) i 163 TAER onus dance E dato Lo eM hee jl JS ims LOCAL), oq or cec TR Int Laxifenestella Morozova, 1974 ................... 23-25,27,28,30,32, 34,39-41,49,50,53,124 CONUUCHISEY IA ESP Le OT: 7,39,49,50,52, 53,56,156,158,196-198 NICO SIE ea I IQS) o 7,39,50,53,56, 58,59,60,156,158,159,202-204 TACHIOSTININS Me Spe yore sen p.i. Ue 7,39,50,53,54, 56,156,158,198-200 serratula (Ulrich, 1890) ......... 9,10,11 ...... 39,45,50,53,56, 57,58,156,158,200-202 length of fenestrule opening [LF] defined MPSS USUI (UNPUDUSREN eos eror Senne ertet or PRI Leren tela Miller 196 lan... nr greca aUo) Sr een ee EXIT 50/02 seen RITA LF [length of fenestrule opening] MISSISSIPPIAN BRYOZOANS: SNYDER 269 AMC Ras Ne tt DAA IA F,B SEIS OMIC Otter Greek. an vert tee 9,175 TS EP OO e AAA AAA Oe EER 35,37,38 Si BISDSSBTAaBe eSI VII e limitaris, onau EAO A O ee 9,175 DUNAS tells EO oa 24,25- 2 39,73,81,82,83,156, CEVO INE O Ve due I ES 9,175 158,159,215,216 40: Troy Roadcut (measured section 20) ... 9,157-159,175,183 ONES TEI ADRIA a eRe DO eU m E ee 81,83 MANOS GO Ws MIS t4 a eH DIES ee a ee eee eee 9,175 DELITO line Acti ti HERO O averse: OC Ne 15 249 6 Uh by ANO RE Nr A le 9 5 ISO Ine on MO) ordinaria P3 ASS DOVER tek ae A 9,176 ESOO en ee 15,16 44 Dupo Quarry (locality 44) ~. ua. anne 9,176 inae S(ARSY(N) pave I LEM 14 AS Meramec River Bend na ELS Macs 9,176 Lisbon, Missouri (locality 43) .............. eere ORO AAN COS 9,176 A ER EUNT 174 47: Cragwold Road (measured section 21) hice ne cneasa Little Whitaker Creek (locality: 23;:measured-section BR ae. OA 9,56,58,72,79,95,97,111,136,149,157-159,176,184 A AE sheet oa I qe 9,157-159,174,182 48: Columbia Roadcut (measured section 22) ...................sssss. LA A acu. MUS c. ne a DG en, 9,157-159,176,183 INAUSUS TUN OLLA ESA ee NUS 9v. 49: Dennis Hollow at Valmeyer (measured section 23) ............. 2: Bentonsport, Iowa (measured section 1) .................ssessesss . 9,45,47,49,54,56,58,60,61,65,67,72,76,79,81,88,92,95,97, UNICI AeA ROL Olen He bv UE Pn e S 9,157-159,172,177 114,116,119,136,146,149,156-159,176,185 SODISGVPEGOSdUdUae e evenire ve RR EE OE IIO 95125772 oeuipormad Euas end @ondrar TIST Pe ee a En 23 ANO LIT ONS, rer inene e enaa N 9172 ¡OBRAR OSD CT O ae 12 5: Iowa Terminal (measured section 2) ..... 9,157-159,173,177 LONS NETIGI Renner 17,18,23,24,40,61,71,85,113 6: Keokuk Industrial (measured section 3) ..........0cccccecceeeeeeeeeee LRM [reticulate meshwork spacing parallel to direction of branch TAS ale O SANSA A SNAN 9,127,130,157-159,173,177 growth] 7: White Hollow (measured section 4) ...... 9,157-159,173,178 ACHERN O DE F,B SURCO W OS baa ea E EM 9,173 THUS ATC UAL: A EEE Er 36 9: Grays Quarry (measured section 5) ....... 9,157-159,173,178 SS A E 161 10: Hamilton- Warsaw Roadcut (measured section 6) ............... DOUG CDS eee a. ORR ee REED 161 FERN een 9,45,49,54,67,83,92,95,101, 104,106,111,114,119,127,130,151,157-159,173,179 11: Geode Glen (measured section 7) ............. 9,58,72,85,101, DUGGOV ARE OD DONO Ls AE and ee AGED 146,153 111,114,119,121,122,127,133,148, maculasimilis, Laxifenestella ............... quU eT 7539:50,53; 149,151,153,157-159,173,179 54,56,156,158,198-200 LES WV AERA WA AS bees ciet enr dt e ene Ue SR LA RR 9,173 Malayer rie a ti SM d ee 13: Soap Factory Hollow (measured section 8) .......................- Marcas Cb d) eq utente ERS: WOES HORROR AN VILIA E VE DAR SALA NERA HS 9,157-159,173,180 IMERSCcHalt LOGS) c4 ONT cicer cep een See eee D ee 14: Buel Branch (measured section OR E 9,157-159,173,180 MeatshallRcad Re SRL ETHIOPIA 15: Sand Branch (measured section 10) ............... eese Marshsll;Rosd ocality-d6)« S TL DEOR ERSTES METER UNA EORR IANUENSIS ANM ARMS RS A 9,12,157-159,174,180 Mary Knott 1:24,000 quadrangle (1972) 16: La Grange (measured section 11) ........ 9,157-159,174,181 Massachusetts Woods TIOE nn. ren een A e E 9,174 MAW [maximum chamber width] ISAGANTOL Missoni BE ee ise 9,174 ONE EI ES ADA een F,B NO A@AT IOs NS SO Lites (DER b ecco et enue ener 9,174 Wt Patek avance VATE es LE 37,38 20: Mount Sterling (measured section 12)... maximum chamber width [MAW] Mcgee matt mere ga EEE REN 9,97,157-159,174,181 deed EN ne 21: McKee Creek (measured section 13)... STATE eax tN hd eg REL TES IR 37,38 a CHORE E Mm MN 9,12,157-159,174,181 maximum diameter of central axis [DCA] 22: Versailles West (measured section 14)... AMELIA DA ART c CUN F,B a E T E E ET RA I Ve E 9,12,157-159,174,182 23: Little Whitaker Creek (measured section DD) te Tannen sere ee EEE REIN 9,157-159,174,182 9,47,174 Max villesiiestone acd sense ee eee 146 9,47,174 MCCUE Westllocalits 35) ex nn een BITI BAHIA RS cae: MECC (TETI ite. a 1727,29—31,33:39;73,85,137;142 9,47,157-159,174,182 MeBkatlan (94D) aaa AE Ta 47 AS NER E Mektesrande Weit IS) sun O NETTER 9,47,157-159,174,182 NEG RESCH ERINNERN ns ee teet rb TA 28: White Hall= Bess ern sc ARMED 9,47,175 McKee Creek (locality 21; measured section 13) ......................... 29 White Hall bi(neasuted sections 9) air eee. RR S 9,12,157-159,174,181 AN 9,47,133,157-159,175,182 McKinney (1977) MEEL T a a E IO White Hili O 9,47,175 Meokinneyz(@l97 O) ir tee ee 124 SUM Witte Halle Hentai AA, 9,47,175 MAA USO 8,21,25,27,28,38 e Camoltonm Milioi e aeee a NS 91775. Mekinney amd Gat (1980) 9. 9 MU eee 124 33: Benchmark on State Highway 369... 9,175 NICKS yea ital e RR I I E 7 34: Otter Branch (measured section 19) .... 9,157-159,175,183 IVECIN ts G3) ASA ER 16 BOSMOGIUSE Westin OU a EST MoQuccn Hinchey; and Aid CLOS eet eee cree 15 270 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 Measured Sections: 1: Bentonsport, Iowa (locality 2) .............. 9,157-159,172,177 2: Iowa Terminal llocality 5) .............—.—-. 9,157-159,173,177 3: Keokuk Industrial (locality 6) ... 9,127,130,157-159,173,177 4: White Hollow (locality T). sere nn... 9,157-159,173,178 > Grays Quarry (locality I) essersi 9,157-159,173,178 6: Hamilton- Warsaw Roadcut (locality 10) ..................... sss . 9,45,49,54,67,83,92,95,101,104,106,111,114,119,127,130, 151,157-159,173,179 7: Geode Glen (locality 11). 2.2.2 9,59,/2,909 DOT, ALL, 114,119,121,122,127,133,148,149,151,153,157-159,173,179 8: Soap Factory Hollow (locality 13) ......... 9,157-159,173,180 9 Buel Branch (locality 141.222. 22.2: 9,157-159,173,180 10: Sand Branch (locality 15)................ 9,12,157-159,174,180 inka range (locality: TO) aan 9,157-159,174,181 12: Mount Sterling (locality 20) ........... 9,97,157-159,174,181 13: McKee Greek (locality 21)... to 9,12,157-159,174,181 14: Versailles West (locality 22) ..........- 9,12,157-159,174,182 15: Little Whitaker Creek (locality 23) ...... 9,157-159,174,182 16: White Hall—C (locality 26) ............ 9,47,157-159,174,182 17: White Hall—D (locality 27) ........... 9,47,157-159,174,182 18: White Hall—F (locality 29) ...... 9,47,133,157-159,175,182 19: Otter Branch (locality 34) .................. 9,157-159,175,183 20: Troy Roadcut (locality 40) .................. 9,157-159,175,183 di Ccumpoold Road docaliy FI) nn. ee ee, 9,56,58,72,79,95,97,111,136,149,157-159,176,184 22: Columbia Roadcut (locality 48) .......... 9,157-159,176,183 23: Dennis Hollow at Valmeyer (locality 49) ................... ss. . 9,45,47,49,54,56,58,60,61,65,67,72,76,79,81,88,92,95,97, 114,116,119,136,146,149,156-159,176,185 mediocreforma, Banastella ................- DONAU que 11:99, 72.791 80,81,83,156,158,213,214 PCR VCC SISD PCRS OUG zu: coke erreur T euere Coro RA 40 Mock and Worthen (1800). rennen 12 TIERES ÄNCHDMERES RURSUM CL E M 126 LO DEI EIOS Leu dsc pie sopa A S Peu 15 Mendon 1:62,500 quadrangle (1946) ......1..: cii 173,174 hi River... A NR re 176 Meramec River Bend (locality 45) ...............eur...r...00000000 9,176 Meramecian Groupe irs. ass a eier ee Fi Meramecian Series rn 11,13,49,61,126,176-185 Meredosia: 1:62,500 quadrangle (1928)... errore erret etn 174 Meremac [see Meramec] Meremec [see Meramec] meshwork formula of Condra and Elias (1944) ................. 18,58 Meyer and Macurda (1977) Delp Vet River ood E micrometric formula of Miller (19612) et seq. .................-- 18,58 Miller See 1889) aan ann erh 130 MER CECA) nenn ne nee 18,22 Killer TO IGI . eisen ee 18,22 Miller, T. G. (1962) 23,24,47 Minilya Crockford, 1944 ... 22-24,28,30,32,34,39-41,61,62,65,97 Anplarıs Crockiord, 1944. nme ee 61,62 DUFGEISEFIGIS, D Wenns 1415... 745391004605, 66,67,156,158,205,206 SIvonelhu, ti. Spe cou aee cene SALA da 7,39,61,62,65,67,97, 156,158,159,164,204,205 minimum chamber width [MIW] Beis EEE CT TTE NAE illustrated Mirandifenestella Termier and Termier, 1971 ...................... 23 Aiyenestella-Morozova, 1974... 15 ree eoc eee eren Bee 23,24 DU RON ERECT e cepe ee E A o pa 15 IMSS Der Tor mes: 8,9,12,15,16,18,49,173,176 MESSI I E RIVET ATO eer pc E aret toT AURA 10 Mussissippianestratolyper erede eee are Fs eh based 8,10 MISS Uta kno ERES Is err 8,9,15,16,173 bo S iN 174 COMICO iv ctr c VU EM 15:08 SDO A A o MEER IVECEAIMICE areas rA RE ET N Moscow Mills St. Francisville Sta Lonis ea en 116,136,138,141,176 Six Lows CoL Barrat S Station: oerna 83,111,113,138,146 TEONE ALS ia eier usque An 16,175 Wayland Missoni Geological Survey. en en 11 Missouri Highway hiat obras rd e don MER Te Met M M EOS 9.176 MIW [minimum chamber width] BENENNEN DSC eG AE RN lose tubae oid aot te hae ek e MGI CIS OS nee ors Doo SURE ea Monroe City Syncline MOUSSE. Morozova (1:999) ran ann. a NEZ AGI aea mer A nun WIGEOZ ONAN I VDE Fer e stupra Fk EN e PETS TN Morozova IIT I r rn a e A Wage nare tear Morozova (1974) 9 ata 8,18,19,22-25,27-30,32,39-41, 49,50,61,62,67,68,72,90,124 Moscow Mills locali Als anne Br er 9,175 Mount Sterling (locality 20; measured section 12) ......................- anal ete ig er A ek 9,97,157-159,174,181 Mount Sterling 1:62,500 quadrangle (1926) Vani G9 A NA m rige multispinosa, Meneatela e mere sanyo Ryn Moers 47 I CHOSEHEIIT E cie vbt dre teen dier iibris Fear IT da eie SU 47 IRGENTENOSIENDE ERAT eus streets: 4531. 35 39,41,44,45,47, 49,156,158,195,196 NESSES Arehimed es aus na condon 50,51,52 u... 39,124, 125-127,156,158,159,241-243 Nekhoroshev (1926) 18,41,47 o od AUOD ea 19,22 Niekhorosken (LOS Do na csetera PT annie 19,22 Nekktorosnevs A ret breit cas ec ERR eO EN 19,22 Nokhoroshe r (T933 a0 0. ee ae acs Ma Cu AN 19,22 NEKHOTOSHE GEO Geers ccd sean Fue rs car enor Ment hn ete n eto 19,22 Nekhoroshev CE960). ur Ar ra Ar ara TE UD 22,61 ING RING ROG RCN AA A ee AO pe) Nevada NOTASIE 1c reo er ee Nicholson and Lydekker (1889) Nickles and Bassler (1900) ................ NTE O cn rice Sene cs NielseteaudsPedetsem(1979). nassen ee vue dues Nikiforova (1927) Nikiforova (1933) Nikiforova (1935) MISSISSIPPIAN BRYOZOANS: SNYDER INIo tonene a GliO BS) RE E ia 19 INR Sul oni eH Pairs ee LAG 19 NO ta 24000 quadrangle o e ewe aoe eee 172 INiotayIlinois:(ocalitys4) iss. Ba ee. Oel. IODINE LE OD ORG ee A AS TTT 25 number of aperture openings per fenestrule length [AF] PLUS URAL EAN. IN E TAE es Re 35 COPED ee F,B number of stylets surrounding aperture [SA] CLS: t teens iR edm Ael hun NAE ut F,B UU TAC s aero ses IN omnet eR exer» Tomo 35 INUbwogd.Antcliden nueces d eo ER 15 AVe Dean adi nenn. RD 10 COUNTA GDLEPDOERNR etre ien E E A 106 Sir bonae ia Erbe E es 40 NIEN onna E a Mee Rel Rn en me rM aen 146 URS GLE Clip nen dca LA ae 144 SCIOTO E Peet Ba ss cousins sin L Ee ee at 144 OL [ovicell length] LOCUM ES CAN e Lot A ce aor AT AE USEE no nee o A NEE Pond die IDiSnA ESS) een ae br Ne eant GE Onor (ISAS = SS) eee E Order Ciclo A eect. DR REP Gryptostonata Vine Ese cocer terree eter re UE Eyelostomata ne Cystoporataen AA aa Trepostomata Ulrich, 1882 ...... Orthotetes keokuk (Weller, 1914) Osagean GROUP re RUE tot AA etn BR Osagean Series... 11,13,49,61,126,177-181,183-185 Osgood Fund 8 Osgood Prize 8 Otter Branch @ocality 34: measured section 9) 525... ee VA AA A AA. 9,157-159,175,183 A o E Otter Creek Syncline Ovicell length [OL] CENAS, IAEA RN F,B Ovicell width [OW] A A c D Need illustrated OW [ovicell width] A MO oe ccu ino MES FB MAMA ARA RA RANA AT EIA ECTS NN Owenanus, Archimedes ................ 52,53,54,55,56 ...... 39,124, 127,130,133,136,156,158,159,243-247 E De 10,15 IISUDU iv ee edet ceat 15 CGN Crm Gry AA E T 165,166 iS Sener ren he en 10 Parafenestella Miller, 19616... oP) Paratriserialis, NITE GRAS A IN ¡EN AA 7,39,62, 65,66,67,156,158,205,206 Parsons and Le Brasseur (1970) anne 162 ANA AAA A ICM 108,110 271 Pays ON ANCIN a anna re ee 15 Permofenestella Morozova, 1974 23,24,25 PESTO ACIDOS IA 39,40,41 ...... 39,106,108, 109-111,113,156,158,230-232 PRNIPSEBBO) nee bx cnm EE ane 17 Phillips (1841) .. 15,17,23,27,29-31,33,36,39,40,103,106,108,119 PINUS ARA ce e e ee toa ad 17 LASSE Ecke arate: i ei e ae TT 175 Blass Grece locali) uber a oco ME 9:175 PuttstieldbsAwiticlines. RR OR A L5 plumosa, enestelliersns sr b ben lm EE LI Loi itt VEREIN NL eee ctx OO et COME RE elei c oo tati N ME BOM tna de Polyfenestella Bancroft, 1986a .. PODA SAA. a ee en A 17,27,29-31,33,34,39,73,85,137,141,142,146 SAO ROS ISI dendroides McCoy, 1844... 00 Lo C Bae ona end 142 gracilis Prout S00 Eo. rel 65,66 ..... 39,143,144, 146,153,156,158,159,256,257 CUBS A GINSAPLOUU, een 144 halliana-Brout, 1800. sem a ee ege a 146 matcoya nah ERC I sae. ee er: Po qR 146,153 RETO PS OA Hm IR e ear AS 39,144, 154,156,158,159,262,263 simular irich is O a 69,707) osa 39,143, 144,148,151,152,153,156,158,260-262 spininodata Ulrich, 1890 ........... 67,68,69 ...... 39,143,144, 148,149,151,156,158,258-260 KarSOuViensisbrout en. are. 146 PASO UNEN ISG PVO aa Quo. arta een 146 varsoviensis Prout, 1858a ........... 66,67 ...... 39,85,142,143, 146,147,148,151,156,158,257,258 POM DOLE Rem PhO uty eae LOL anres ence iren EDEN 144 Péiyporelia Simpson 18950 Sam de FIRE en 142 PolyporinaFredrikssd9205 ait euere 142 Power and Pryor (LOS ERE EUN NE 10 PRI [Paleontological Research Institution, Ithaca, NY] ........ 7,8 Prout GS 58a) eat week ean nn 12,17,27,29-31,33,39,85, 137,138,140-142,146-148,156,254,255,257,258 Prout (998b): nase 17 Prout CSSD) ee cca 17,39,108,111,113,146,156,232-234 Prout 1360)5 85 4 t Eo bm 39,113,144,146,156,256,257 Rodt (LS GG) Rakai dM, A HL AD SEL IE E 17,144 pomana Hom yous d ad d rer A A Ea ee 21415113 puoulana vermifero, PREM NON cet cd E Ae 119,122 Frontea Th 1889.32... 22 ee ee 12 Lore al Sl A Rn 11 OP IOE n SAH: ee CIS 17 RA [chamber reverse-wall budding-angle] US IE een EN illustrated Rampr@reek Bimestone uk li ee 14 FORA MEE ee NE anne 156 Ruryenestelau Morozova; [QUA anche h See 23525 iRethifenesiella.Motoeovanl Anne. A AAA chicos’ ks 23-25,27,28,30,32,34,39,40,41,42,90,124 multispinosa (Ulrich, 1890) ............... 5. dx. 39,41,44,45, 47,49,156,158,195,196 tenax (Ulrich, 1888) en. 13. 8 39,41,42,44, 45,47,49,58,156,158,192,193 272 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 Rectifenestella Morozova, 1974 tenuissima (Cumings, 1906) .............. 20309233 39,41,42,44, 45,46,47,49,156,158,159,193,194 IC MR DOOR A SUUS Le ee A tese bte der eren 76,88 * Retepora Archimedes" of Owen (1842) ................. sss 124 reticulate meshwork spacing parallel to direction of branch growth [LRM] defined reticulate meshwork spacing perpendicular to direction of branch growth [WRM] (ien desc et MM Le e aire ic le SRR pM ER e F,B DE E E A A A RT a E 36 POM OTS POU A aree N es TIA 39,144,154, 156,158,159,262,263 FEV ICD OF A re 124,130,133 Restontrand Colimon (T965) 1. een nen 12 RIDERE UE Le DI N BEE ER aS a RSE ehe, 17 Rhodes, Awstin, and Drace (1969)... a2. 12 Rhombofenestella Termier and Termier, 1971 Roodhouse 1:62,500 quadrangle (1924) ........................ ERIS c 01000 rd patie Sevan A Mp MT D Rotaia subtrigona (Meek and Worthen, 1860) RSL [diameter of macrostylets on reverse branch surface] NO EHE NOE LA ORBE OE nee e EVEN cd UTE O e F,B ARDOR D RE Ue A E E pee Vine ets ee nod cole See epa 35 RSS [diameter of microstylets on reverse branch surface] BOULE UELLE LUE ER UE ae F,B ARA e HI NN ro E hey he 35 A O ccm E S maar A E 15 a a A een en ARE 90,92 rudis, a U ooe aNd ER 29,30: 5052 39,83,88,90, 92,94, 156,158,220,221 ae EEE RR RR PREND 41,83,88,90,92 Rugofenestella Termier and Termier, 1971 .......................... 7 RWT [thickness of reverse-wall laminated layer] TC IA eoo er ARE INDIE e et aden RUE PES F,B wr MEE EE SEHR RRR e oC 9 37498 SA [number of stylets surrounding aperture] QUUD E EOD ERR AU Iden ROMER EROR REIR F,B NOME EHE NEUE A EUER AUD SAD [diameter of stylets surrounding aperture] ROE. ER btn ek E A o aT F,B AA A A 95:57 O A E E E S E 144 Salem Limestone Formation ............... 11-16,53,73,90,92,97,98, 141,159,174-176,180,181,183,184 KREIS ENTER ER MA ee 14 Fults Member 14 Kidd Member 14 Rocher NOISE 2. RT EL 14 suicii-iudoviet, FONCTION. AA A ni 138 sanctiludovici, Fenena a 63,64 ...... 39,137,138,140, 141,156,158,159,254,255 TEE SPUMA AA E d nere dE RR E E ETE REAL Ad 138 Sand Branch (locality 15; measured section 10) .......................... ACE TON ERN See ee So, O EN EA CRT LE 9,12,157-159,174,180 SIR DEREN O een ee 174 SSndberE P. ai. ka Sangamon Arch sarytschevae, Fenestella Schoener (1974) Schoener (1982) di Scotland Midland Valley Eee 26 Second Archimedes Limestone nu Ar a TAS S UEBER Clee ead uude ue a e O etal 175 serratula, INENEOSTEN On ITO ee fe A O A iy 41,56 ECE COSTED s ideas AA E 39,45,50,53, 56,57,58,156,158,200-202 Sheldon. Sutelitfe, and Prakash (1973) ea ee 162 Shepherd College, Shepherdstown,.WV nennen 7, Faculty Minigrant Fund EO WAT TIS AE Ces ache hive AREA SHISHOV ARGO OS) Sst noe cct A terret E DERE IR te ee dere Fu Shulga-Nesterenko (1936) Shulga-Nesterenko (1941) Shulga-Nesterenko (1949) Shulga-Nesterenko (1951) Shulga-Nesterenko (1952) Shupa Nesterenko(1952) o. oe vorsago e verte EN 19,22 Shuloa-Nesterenko. 9.00) uote n doa eee e oM Kon Sen. and Hatten WA 31 A O O 22,142 o A doe Sd 138 SIPIMIGUIDS POlyporauoeeeeneere-s 69,70,71 u 39,143,144,148, 151,152,153,156,158,260—262 SISSE S Sine ree en tn, OUR Np John cA SRR Rs Fe) 7,62 BONN MINI a ri rer 13 ¢ ee 7,39,61,62,65, 67,97, 156,158,159, 164,204,205 A ARE 160 SNB [distance between node centers along obverse branch surface] OOTA ER METRE HD WISI IQ EA LAE aA dece veis ri eese ER SHY GE (LO Su) rl ecran Er CAR UPS Suyderand Kepler (IS Nenn SINGEN ORT E E AR E RR SAN In Soap Factory Hollow (locality 13; measured section 8) ..............-- A ARAS wr ETN 9,157-159,173,180 Sonora Formation. o eoe ee yos 11-15,159,172-174,177,179 SolloraSandstione en eremo eve tdv ge e RITE TRIN en 14 Somi Fork Otter Creek locali 36) evertere 9,173 spacing of macrostylets along reverse branch surface [SSL] aA A NC F,B VLSI CC EINE een teen 35 spacing of microstylets along reverse branch surface [SSS] A ee er ren illustrated spacing of stylets along obverse branch surface [SSO] AA SS A E F,B dd A RA E TAR RIE Lr DD spacing of whorls along central axis [WSC] (P Topics ee ecl SUN D A F,B A O gas er 36 y A no A cene trate ront 14 SPAIN Ge natos adios rate 14,159,172,173 spininodata, Polypora 67,68,69 ...... 39,143, 144,148,149,151,156,158,258-260 Spinofenestella Termier and Termier, 1971 ..................... 23,24 SPU TE, TOBA nia ABI 12 a eet 15 Springville Formation 14 SSL [spacing of macrostylets along reverse branch surface] (ops ri E SEN RETE A F,B PUSIO A seen 35 MISSISSIPPIAN BRYOZOANS: SNYDER 213 SSO [spacing of stylets along obverse branch surface] ACHTEN Ree Vat ee era Re F,B VIT ST OM Tal ess s o eRe ern oO ecc eut BC d m 35 SSS [spacing of microstylets along reverse branch surface] GEHN CCNA, ut ORO Tea era PUPA ernie Sete RE Tom F,B Uri ALC aA RR E cU NM Ele ER 35 St. Charles 1:62,500 quadrangle (1954) ................... eee 195 St. Genevieve A PME. m 11 GROUP nenn MRR Ta Mn 11 St. Louis (io ecc ne 11,138,141 ¡SONIDO ca 11-15,47,56, 73,83,90,98,138,141,146,159,173,176,177,179 NADO NOE ene tala tal EN 138 Sis Genevieve limestone era Md edd 115) MA einen 14 Stockdale: (LID) Ana Meet. PE ea E s disp ec 14 NOG RTOMCNS TSMC ICSTOU Gian: ern 45,47 Seta ot econ veces: tess eee NEU n 162,164 Siiathimann (1973) Mt RI eee ie Ursel. 160-164,167 SANTA UA AAA N een 25 Subfamily IBcHestellingde see nn en tr OR NOU A dieit 17 Goniocladiinae 17 Polyporinae 167 UIC Opornata Benesiella nn A DA 41,45 Suborder Fenestelloidea Astrova and Morozova, 1956 nn. oda EE UN TT 165517;21522:/27:830 Ptilodictyoidea Astrova and Morozova, 1956 ............... 16517 Rhabdomesoidea Astrova and Morozova, 1956 ............ 16,17 SUORONE ER DI ee a OS T AN A ee. SAATCA IT EE N T sciences Synocladia King, 1849 Synocladia(?) fenestelliformis Young, 1881... 26 Taphrognathus varians—Apatognathus Zone dobne tan eee 12 Taphrognathus varians-Cavusgnathus-Apatognathus Zone of Rhodes, Austin, and Druce (1969) aeee 12 Voyeur (del 90955 9 900 0 te Mas 18,34 a e 18 Tavener-Smith (1973) ............ se 18,22,47 Tavener-Smith and Williams A ee S ET 1617 LEOS, E ee ee en ier] 19 TB [thickness of branch] DOUCEUR EN et illustrated tenax, RENTE n C eaa ARTE DI ome on 40,41 IN QUIT NICHE er ee 152. nr: 39,41,42,44, 45,47,49,58,156,158,192,193 a OA EEE AAA 15 tenuissima, EHESTEN DE ecc eee este etre en P em EO 45,47 Rectifenestella ............... a 39,41,42,44,45,46,47,49, 156,158,159,193,194 KOIT OES: ALC un ea 126 Termier and Termier CLOT) ae ates a 8,18,23,24,61 EN Eo. ee rer ctt es a i 18,23 LL ERRARE taint HOUR ARN. Mcr 144 thickness of branch [TB] defined thickness of chamber lateral-wall granular layer [TLW] LEHREN Recto Merchant O cries ocu cicero RED F,B VU SUNT Oris ta Le ei rn Rte 37,38 thickness of front-wall (obverse wall) laminated layer [FWT] (Lir arp rd er cA SR illustrated eI EUR naaa REN NE CER IRA bcm LN doe E E STERNCHEN illustrated TLW [thickness of chamber lateral-wall granular layer] vinum AED EUR E c e eA en. DUST ALCO UR ARO eni vein cies IESO (LOSI) ee triserialis, Fenestella DEZE ISO ee rer ee REN zn IS U) ne A E UEM M DEZA IS See CR LIES. Tiza andas an OSA een a Troy 1:24,000 quadrangle (1972) Troy Roadcut (locality 40; measured section 20) ........................ e A T PURSE UI m 9,157-159,175,183 Tröy=Brussels Syncline ie OMNES. rn LESE 15 TRW [thickness of reverse-wall granular layer] A A E EEE LANE Turpaeva (1957) er TUTO, BNET vii oe ae era soe anA UTX [Uni versity, of Ilinois, Urbana, Eh a rn 7,40,45, 47,49,54,56,58,60,61,65,67,72,76,79,81,83,85,88, 92,95,97,101,104,106,111,114,116,119,122,127,130,133,136, 146,149,151,153,156,192-253,256-263 Ullen Formation [see Ullin Limestone Formation] Vil Limestone Formatii a are eines 11,13-15 (nol (1982) A e Rene ee Se ne 16,18 Ulrich (1888) .... 17-19,39-42,47,49,58,144,156,192,193 WITCH 8 IO) er F,8,12,16-19,22,39,41,44,45,47,50,53, 56-58,65,67,68,70,71,73,76-78,81-85,88,90,92,94,95, 97,101,106,108-111,113,114,116,117,119-122,124-127, 130,133,138,141,144,146,148,149,151-154,156,173, 195,196,200-202,207-209,211,212,215-218, 220,221,230-232,237-243,258-263 OE Aa A ae ects nets 17-19 Birch HINEIN ti NUECES A is Oia quos A meplut n 39,40,53,65,106,108,122,129 USGS [United States Geological Survey, Reston, VA] .... 8,11,13 SPI 0 ERGO ERO es cod E E NEN 1i 173,174 USHUAIA, Gubifenestella........ eeeesesetes eve 31325 05 7,19-21,38, 39,90,92,93-95,97,156,158,222,223 USNM [United States National Museum of Natural History, Smithsonian Institution, Washington, DC] .......................... 7,18,40,45,49,58,65,92,111,114,119,146 274 PALAEONTOGRAPHICA AMERICANA, NUMBER 57 USSR A A E E A A cu E ET 19 RUSO PIO aus. ae ae 40,49,67 a en 19 a Perry 960) arm na tnt Re ean 22 Uropa Potim dS de acci do odes, reete 21:25:27 nobhsqpamaude im Pocta, 1394)... eee ee 25 Valmeyer 1:24,000 quadrangle (1954) ............................0.- 176 Mover aite lee oor ong ee ode d dc ott 16 Valmeyeran Series ... 11,13,16,31,73,90,98,122,126,138,177-185 valmeyeri, Archimedes ............... 60,61,62 _...... 7,39,124,133, 134,136,156,158,159,251-253 ana IS A TAS - Sce 11,12,14,130,133 VltSOWWEnstseP OL VD ONG: ia AT AAA II o AURA 146 ALA a Le ya) y yl AN AR ette ter oon Oe. 146 Varsoviensis, Polypora. .............susse. 6667 ooe 39,85,142,143, 146,147,148,151,156,158,257,258 VD [vestibule depth] One doe Mi er he F,B BÜRSTEN 2 CENE tO C CT ERE 37,38 Verusta, Aperitostella. aeree 38540 o 7,39,98,104, 106,156,158,159,229,230 BORD SE us teo rs iol eas A 160 VeDWifera, Hemitypa: 2.00. RR 47,48,49 ...... 39,108, 119,120-122,156,158,238-240 Vera Alone rare I» Versailles West (locality 22; measured section 14) ...................... HO ose racecar, seit 9,12,157-159,174,182 RMN PD ca ties cs tu konnte accu nene mcr nete eee ete 162 vestibule depth [VD] hona cuum d lida UM DE NEM EDEN M MEE Lu rc Vine (1880) Vine (1884) Vine (1886) Wenceslao isa RI A A E a C19 S7 A ie ee RUTRUM Warsaw 1:24,000 quadrangle (1964) WIEN AIM CA A a na 5 NOSE IGS A A tek E e Waro: Eat (locality sd 2 ics A Haan Warsaw Formation ...... 7-17,26,27,29,31,34-37,39-41,47,49,50, 53,56,58,60,65,67,68,71-73,76,79,81,83,85,88,90,92, 95,97,98,104,106,108,111,116,119,121,122,124,127, 130,133,136-138,141-144,146,148,149,151, 153,156,158-160,162,163,165-185 Garret: Mall Sandstone Member... 12 DORMS Sale Member nr... nee 112% Wilde Sandstone Member zu... 2.222 3220 12 NAS ERROR N RE 11,15 WERBEN eMe e. cec A A A Oa. 23,61 Waterloo 62,500 quadrangle (1955) ............ nn 176 Waterloo robust [zoaria typically large, highly resistant to breakage]) . outward expansion (flat, obversely or reversely curved, undulating, cup-shaped, or spiralling from central axis) mesh spacing (close [WF < WB] > intermediate [WF = WB] > open [WF > WB]) . astogenetic thickening of the zoarial skeleton (slight, moderate, or pronounced) mesh uniformity (regular or irregular) . secondary features (e.g., central axis, reticulate meshwork) . dimensions of secondary features . probable size and shape of mature colonies 2. Branch characters > AO mia iO mA . robustness (delicate [fragile, frequently crushed, thin width and depth] — intermediate [moderate preservation, width and depth inter- mediate] ^ robust [wide, thick, typically well-preserved] . width (narrow [<0.30 mm] — intermediate [0.30-0.39 mm] — wide [70.39 mm], and constant [CV < 15] or variable [CV > 15]) . proximodistal trace (straight, sinuous [bending toward sites of dissepiment emplacement], or locally broadly curved) . spacing (close [DBC < 2.0 x WB] > intermediate [DBC 2.0-2.5 x WB] > wide [DBC < 2.5 x WB] . distance between adjacent branch centers (regular [CV < 20] or irregular [CV > 20]) . texture (smooth or granular, and effects of astogeny thereon) . surface profile (e.g., rounded [N], flat [-], or angular [^]) . keels (if present) . whether they are single or multiple, and the number across branch surface width (narrow [<0.05 mm] > intermediate [0.05-0.15 mm] > wide [70.15 mm, or «0.5 x WB]) . degree of development . linear characteristics (continuous or intermittent, straight or anastomosing) . position along branch (at branch midline or curving around apertures) . effect on obverse surface profile . effects of astogeny nodes (if present) . emplacement (monoserial or biserial) . degree of development (poorly developed, intermediate, or well-developed) . size (small [<0.07 mm] — intermediate [0.07-0.12 mm] — large [70.12 mm]) shape (e.g., circular, ovate [includes direction of elongation], stellate [(number of lobes]) . uniformity of size and shape (regular [CV « 25] or variable [CV > 25]) . location (on branch, on keel, and in a straight line or anastomosing) . number per fenestrule (includes range and mode) . spacing interval (close [40.25 mm] > intermediate [0.25-0.80 mm] > wide [70.80 mm]) and uniformity (even [CV < 25] or uneven [9V4225)]) 9. effects of astogeny stylets 1. size (small [<0.01 mm] > intermediate [0.01-0.02 mm] > large [70.02 mm]) 2. uniformity of size and position (regular [CV < 20] or irregular [CV > 20]) 3. location across branch surface 4. effects of astogeny XAO Uu bh uyn IDA RU T — . texture (smooth or granular, and effects of astogeny) longitudinal striae 1. number (few, intermediate, or numerous) 2. spacing (close, intermediate, or wide) 3. effects of astogeny . microstylets 1. relative size (small [<0.018 mm] > intermediate [0.018—0.026 mm] > large [70.026 mm]) 2. location and spacing across branch surface 3. size (regular [CV < 20] or variable [CV > 20]) 4. effects of astogeny . macrostylets . relative size (small [<0.05 mm] > intermediate [0.05-0.08 mm] > large [750.08 mm]) . shape (e.g., circular, ovate, or irregular) . uniformity of size and shape (regular [CV < 25] or variable [CV > 25]) . location on branch surface . spacing (regular or variable) . effects of astogeny Dúo bh UC F2 — Table 8a. — Continued. O. rows of autozooecia 1. number across normal branch surface 2. number and extent proximal to sites of branch bifurcation P. changes in branch thickness 1. thickening proximal to bifurcation (slight, moderate, or pronounced) 2. thinning distal to bifurcation (slight, moderate, or pronounced) Q. heterozooecia (if present) 1. type (e.g., ovicells, parazooecia, cyclozooecia, caverns, or microzooecia) 2. size and emplacement 3. Dissepiments A. width 1. overall width (thin [<0.5 x WB] — intermediate [0.5-1.0 x WB] — wide [>1.0 x WB)) 2. width relative to branch 3. uniformity (constant [CV < 20] or variable [CV > 20]) B. length 1. overall length (short [WF < WB] > intermediate [WF = WB] ^ long [WF > WB]J) 2. uniformity (constant [CV < 20] or variable [CV > 20]) . emplacement (at regular or irregular intervals) . shape (medially thinned, flaring at branch contact, or uniform, and degree of deformation, if any) . positioning relative to reference planes 1. obverse surface (even, recessed, or highly recessed) 2. reverse surface (even, recessed, highly recessed) F. overall astogenetic thickening (degree and effect) G. ornamentation 1. obverse surface (longitudinal striae [number and position] and stylets [size and position]) 2. reverse surface (longitudinal striae [size and position] and stylets [size and position]) H. texture 1. obverse (smooth or granular, and effects of astogeny thereon) 2. reverse (smooth or granular, and effects of astogeny thereon) I. emplacement relative to branch length (perpendicular or at a variable angle) J. aperture emplacement relative to dissepiment-branch contact (position and symmetry) 4. Fenestrules! A. relative size (small [length «0.4 mm; width «0.24 mm] — intermediate [length 0.4-0.9 mm; width 0.24-0.34 mm] — large [length >0.9 mm; width >0.34 mm]) . shape (e.g., elliptical, ovate, rectangular, or square) . direction of elongation (proximodistal or perpendicular to branch growth) . consistency of size (length, width) and shape (regular [CV < 20] or variable [CV > 20]) . variation in shape and size of fenestrules on obverse and reverse surfaces of zoarium . mean WF: WB; differences between obverse and reverse surface noted . changes in shape and size toward proximal end of zoarium, and effects of astogeny . WF: LF (and range if highly variable) and uniformity of this ratio (regular [CV < 20] or variable [CV > 20]) number of apertures per fenestrule length (range and mode) ADB: AAB, ADB: ABB, and ADB: ABB and relative variability of these ratios (constant [CV < 10] or variable [CV > 10]) 5. Aperture A. relative size (small [length «0.09 mm; width «0.07 mm] > intermediate [length 0.09-0.15 mm; width 0.07-0.12 mm] > /arge [length >0.15 mm; width >0.12 mm]) B. shape 1. circular 2. ovate (direction of elongation, distal enlargement, and AL: AW as applicable) 3. elliptical (direction of elongation, distal enlargement, and AL: AW as applicable) 4. uniformity (uniform [CV < 10] or variable [CV > 10]) C. attitudinal relationship of aperture to plane of obverse surface (parallel, inclined into fenestrule, or perpendicular) D. peristome (if present) 1. relative width (thin [<0.025 mm] — intermediate [0.025-0.050 mm] — wide [>0.050 mm]) 2. degree of development (poorly developed, intermediate, or well-developed) 3. complete or incomplete (if incomplete, location of peristomal gap) 4. stylet development in peristomal gap, and association of stylets with peristome E. stylets surrounding aperture (e.g., number, size [small ^ intermediate — large], constant or variable) F. projection into fenestrule and degree of inflection in fenestrule G. terminal diaphragm (of uniform thickness or centrally thickened, and area of occurrence) moo eS ne ee ! Caution: if WF: WB is large for colonies with extremely small WB, the following distinctions may not apply. Table 8a.—Continued. a pna > w . Zoarial supports A. placement (on reverse surface or on zoarial edges) B. degree of development Outline of Interior Description . Branch A. shape in transverse-section (e.g., elliptical, ovate, circular, semicircular, rhombic, polygonal) B. direction of elongation (obverse-reverse, or parallel to zoarial surface) C. branch thickness (shallow [<0.30 mm] ^ medium [0.30-0.39 mm] > thick [>0.39 mm], regular [CV < 15] or variable [CV > 15]) Autozooecial living chamber A. relative size (small [length «0.20 mm; depth «0.10 mm; maximum width «0.10 mm; minimum width «0.07 mm] intermediate [length 0.20-0.48 mm; depth 0.10-0.20 mm; maximum width 0.10-0.15 mm; minimum width 0.07-0.12 mm] > large [length >0.48 mm; depth >0.20 mm; maximum width 70.15 mm; minimum width >0.12 mm]) , B. emplacement at or near budding-site (monoserial, biserial [alternating or adjacent], or polyserial [alternating or adjacent]) C. axial wall trace (straight, sinuous [irregular], sinuous [extending toward and connecting with proximal and distal lateral chamber walls], or zigzag [extending diagonally across entire branch, lateral chamber walls short or absent]) and change in axial wall shape from reverse to obverse chamber surface D. orientation of autozooecial chamber elongation (elongate proximodistally parallel to reverse wall, parallel to proximal and distal lateral chamber walls, or length and depth equal [i.e., a cubic chamber]) E. chamber outline near reverse wall (e.g., triangular, rectangular, square, ovate, elliptical, circular, pentagonal, parallelogram-shaped, diamond-shaped) F. chamber outline in mid chamber (e.g., triangular, rectangular, square, ovate, elliptical, circular, pentagonal, parallelogram-shaped, diamond-shaped) G. chamber outline near obverse surface (e.g., triangular, rectangular, square, ovate, elliptical, circular, pentagonal, parallelogram-shaped, diamond-shaped), orientation of outline, and causes of irregularities in shape H. chamber shape uniformity (highly uniform, uniform, moderately uniform, moderately variable, variable, or highly variable) I. location of aperture relative to chamber J. vestibules (if present) 1. degree of development 2. length (short [<0.06 mm] — intermediate [0.06-0.12 mm] — long [>0.12 mm]) 3. variability of length (constant [CV < 15] or variable [CV > 15]) K. chamber ratios (MIW : MAW, MAW: CD, CD: CL), and variability of dimensions (constant [CV < 10] or variable [CV > 10]) L. hemisepta (if present) (degree of development, shape, and positioning of superior and inferior hemisepta) M. uniformity of (constant [CV < 10] or variable [CV > 10]) and mean chamber lateral-wall budding-angle N. uniformity of (constant [CV < 10] or variable [CV > 10]) and mean chamber reverse-wall budding-angle O. heterozooecia (if present) (type [ovicells, parazooecia, cyclozooecia, caverns, microzooecia], size, and emplacement) P. description of three-dimensional shape . Skeletal microstructure A. granular layer 1. relative thickness (thin, intermediate, or thick), and degree of development 2. continuity with nodes, stylets, longitudinal striae, keels, peristomes, and apertural stylets, and ornamentation and features of dis- sepiments 3. relative thickness of reverse and lateral walls 4. astogenetic effects B. lamellar layer 1. relative thickness (thin, intermediate, or thick) and degree of development 2. astogenetic effects Table 8b.— Definitions and abbreviations of the 44 fenestellid and polyporid zooecial and zoarial characters measured in this study. Characters 6 and 19 are simple numbers; character 29, 41, and 42 are measured in °; all other characters are measured in mm. Exterior characters: 1. WB: branch width (not measured at branch bifurcation). 2. DBC: distance between branch centers (not measured at branch bifurcation). 3. WD: dissepiment width (measured parallel to branch growth direction). 4. LF: length of fenestrule opening (measured proximodistally). 5. WF: width of fenestrule opening (measured perpendicular to branch length). 6. AF: number of aperture openings per fenestrule length (mea- sured between dissepiment centers). 7. AL: aperture length (measured proximodistally). 8. AW: aperture width (measured perpendicular to length). 9. ADB: distance between aperture centers along branch. 10. AAB: distance between aperture centers across branch. 11. ABB: distance between aperture centers between branches. 12. DN: diameter of nodes along obverse branch surface. 13. DND: diameter of nodes on dissepiments. 14. SNB: distance between node centers along obverse branch sur- face. 15. WK: width of keel. 16. DSO: diameter of stylets on obverse surface. 17. SSO: spacing of stylets along obverse branch surface. 18. WP: width of peristome (measured at distal end of aperture). 19. SA: number of stylets surrounding aperture. 20. SAD: diameter of small stylets surrounding aperture. 21. RSL: diameter of macrostylets on reverse branch surface. 22. RSS: diameter of microstylets on reverse branch surface. 23. SSL: spacing of macrostylets along reverse branch surface. 24. SSS: spacing of microstylets along reverse branch surface. 25. LRM: reticulate meshwork spacing parallel to direction of branch growth. 26. WRM: reticulate meshwork spacing perpendicular to direction of branch growth. 27. WSC: spacing of whorls along central axis (spire). 28. DCA: maximum diameter of central axis. 29. ACA: angle between distal end of axis and axial whorl. 30. OL: ovicell length (measured proximodistally). 31. OW: ovicell width (measured perpendicular to ovicell length). Interior characters: 32. TRW: thickness of reverse-wall granular layer. 33. TLW: thickness of chamber lateral-wall granular layer. 34. FWT: thickness of front-wall (obverse-wall) laminated layer. 35. RWT: thickness of reverse-wall laminated layer. 36. CL: autozooecial chamber length (maximum dimension mea- sured down the middle of the chamber). 37. CD: autozooecial chamber depth (measured from obverse to reverse surface, perpendicular to chamber length). 38. MAW: maximum chamber width (measured across the branch). 39. MIW: minimum chamber width (measured across the branch). 40. VD: vestibule depth (where significant). 41. RA: chamber reverse-wall budding-angle (an acute angle). 42. LA: chamber lateral-wall budding-angle (angle between ap- erture opening and plane defined by center of branch surface. In species with more than two rows of zooecia, use LA-1 for adaxial zooecia and LA-2 for abaxial zooecia). 43. TB: thickness of branch (measured in obverse-reverse direc- tion). 44. WOT: maximum width of ovicell in mid tangential view. PREPARATION OF MANUSCRIPTS Palaeontographica Americana currently appears irregularly, on an average of about one monograph each year. 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