__ m N^\osv'jx ^ n't aan libraries smithsonian~~institution NouniiiSNi_NviNosHiiiMS saiavaan librar 2 W — _ 2 V/y> TION NOlinilJLSNI NVINOSH1IWS S3IUVdan LIBRARIES SMITHSONIAN INSTITUTION NOlinill aan libraries Smithsonian institution NoiiniiiSNi nvinoshiiws saiyvaan librar s A x) CO jtion NoiiniiiSNi nvinoshiiws saiavaan libraries Smithsonian institution Nouniu X bs X CO O — \o, . - > X{Oiii52> C/) *2 (/) 1_ LI B RAR 2 , CO E!(#^ C ^ O __ X^OXa^i/ q ~ X^O-IICS^Z q X^Ojy DcJ jtion2 NonninsNi^NviNOSHims^sa i avaan^LiBRARi es2 Smithsonian^ institution 2 Nouniu “ - Z r " z Bail LIBRARIES SMITHSONIAN INSTITUTION NOIlfUllSNI NVINOSH1IWS SBIBVaa co x 2 xc*os£ix > -2 w- > C o '" 2 CO 2 CO 2 CO joshiiws saiavaan libraries Smithsonian institution NouniiiSNi_NviNOSHims saia to — CO — CO 2 \ co u M zTS^X ^ w X®5x w CO ^ w h ™ « » O 2 ’ O vjcyosv'jz ™ O ' — NxK -I 2 _j 2 _l 2 _J THSONIAN INSTITUTION NOliniliSNI NVIN0SH1IWS S3IHVaail LIBRARIES SMITHSONIAN INST gp .-ri’iTT.!d^Ts O y ~~ XC/’CBJ^^O/ r- U'«MMvy — m M*t££/ E2 m 'ii xocm^X m \«v£cy ^ m co _ CO X ± CO _ CO moshiiiais saiavaan libraries Smithsonian institution NouniiiSNi nvinoshihais saia CO 2 .... CO z; CO 2 CO &!2! - , . V- E ,« /<3^X E 5 xcojas^z 2 > 2 CO “2 COkZ CO rHSONlAN INSTITUTION NOliniliSNI NVIN0SH1IWS SaiBVaail LIBRARIES SMITHSONIAN INSTI =: co — ... co 2 co , CO * O pcy X^Ciis'jX o o 'C°«"nc y m 2 _J 2 * _l 2 _ joshii^s S3 iava a n libraries Smithsonian institution NouniiiSNi nvinoshiiws saia 2 I- 2 r~ 2 r- v 2 m \^os>y ;y rn in — in _ co = THSONIAN INSTITUTION NOliniliSNI NVINOSHilWS S3iavaail LIBRARIES SMITHSONIAN INSTI siosHims saiavaan libraries Smithsonian institution NouniiiSNi nvinoshiiws saib o 2 _l 2 THSONIAN INSTITUTION NOliniliSNI NVIN0SH1IJNS S3iavaail LIBRARIES SMITHSONIAN INSTI — — 2 r- z r~ o ~ o co ™ * * f\"i\ -rr Xa H- /XaI ’ ! /aTA T) /XK?I ' “ 0\ Li /.x/ - W&w » ^ m S "" ^ w m m ^ co £ co *■ £ co — co noshiiws saiavaan libraries Smithsonian institution NouniiiSNi nvinoshhws saia co 2 ... . CO 2 V- CO Z co ^ - //A'l 1 I ,v C/3 ^ On o r» Tt- . . ^ a- ; (N d >,*.G > G O c/3 » x . a w>£i p.'Sj ”o -a ti y > . VO • Cl oo L^s -0° . . ^ , o ^ a© t — Q- ^ do »3^ ‘d-e-S ^ *— < G __i 4_» O ^ w i— < to c w o a >> r- G >>.G G CJ .h (J U cfl (J +-* T3 C/3 X O rCi U( Lh 0) g c G C h fta >v O T3 ^ O G X) G l- > *D O ,0 oo G a p g(N X g d Q« M w 3 g X'S «d G2 o ^G G O •D (D 0) -S5-S 65 0,0 ON d 10 Ti--o ►» d G X G G! JC pG G G Gj c/3 D O Cl vo d - -O 2 Si a> , i S OO P 32 oo ^ ,,T _ 1 dSd ^ cd ^ *o .c a >> g w " o “ •si E 2 !sm| <3 <3 VO VO VO VO OV ON OO * W VO ^ t)2o 5 WU G . ►-» T3 U:g : to c „ o ^ C/3 ” CO E § o i o o h2 O Ph . VO ov • ^ OV < . o u • - G O «3 b - f-h y-y *+— ' G (Bi4i/icb 2> 5 su .Si *G *S £ £ o o QQ O J do' C/T C/3 E E G G G G « lh ^ U-< Ooi G5 G £ O o O vo 2 G QQ G\ vo VO av cv . >» +s i> .GJ > > 5 W P 24 PALAEONTOLOGY, VOLUME 14 formed by the deposition of an ellipsoidal or spherical wall some distance inside the motile stage envelope (or theca if hardened). This wall in fossil and Recent cysts is often seen to be constructed of two layers which we propose to call the endophragm and the periphragm. The outer layer or periphragm usually carries extensions either in the form of spines or as lists, which extend out to the position of the formal thecal wall and appear to have acted as supports during the period of cyst formation.’ Ectophragm is described (p. 1 5) thus : ‘In some cyst groups the processes may be connected distally by narrow solid rods (trabeculae); in others a thin membrane (ectophragm) may still per- sist between the distal ends. This ectophragm must have been laid down very close to the motile cell envelope.’ Endocoel and pericoel are described (p. 13) in this way: ‘. . . there is a third group, here called the cavate cysts, in which a space, or spaces of notable size, occurs between the periphragm and the endophragm. This space is here named the pericoel; it separates an inner body (capsule) formed by the endophragm from the outer cyst wall, the cavity of this body is called the endocoel.’ The terminology proposed by Downie and Sarjeant is not conducive to effective communication. Their definitions are too brief and the descriptive statements that accompany these definitions are restrictive, subjective and occasionally tend to convey more information than is warranted by the available evidence. Downie and Sarjeant (p. 10) state that periphragm and endophragm refer to those cysts bounded by a single, two-layered wall. The meanings of ‘wall’ and ‘layer’ here are not clear. It may be that the terms refer to such cysts as Spiniferites and Hystrichos- phaeridium where the two walls, or layers, are more or less continuously so closely appressed that they may collectively be considered to constitute a single two-layered wall. It is unlikely that the proposed terms are meant to apply to the walls of cysts like Deflandrea, Odontochitina, or Wallodinium, although this application is indirectly sug- gested in the definition of pericoel. These walls are distinct from each other and are commonly separated by a wide cavity or space. They cannot be considered as two layers of a single wall but are rather two distinct walls. If the authors intended these terms to refer to layers of a wall rather than to distinct walls, a new terminology is necessary to refer to walls. Alternatively, their terms may be considered to refer to distinct walls, rather than layers, regardless of the size of the cavity that separates them. If the proposed terminology is broadly interpreted to refer to all two-walled cysts, new terms will be required to designate the walls and cavities of single-walled cysts and of cysts with more than two walls. Three-walled cysts have recently been discovered (W. R. Evitt, personal communication 1968; also PI. 7, figs. 10 a, 11 a, 12 a). Wetzeliella ( Wetzeliella ) clathrata Eisenack, W. (W.) homomorpha var. quinquelata Williams and Downie, W. (IV.) coelothrypta Williams and Downie, W. ( W.) tenuavirgula var. crasso- ramosa Williams and Downie are possible further examples of cysts with three walls. Other cysts such as Netrelytron trinetron Sarjeant and Paranetrelytron Sarjeant may also be included in this category provided the cloak of adherent matter referred to by Sarjeant (19666) in his taxonomic descriptions is considered to be a wall. Cysts with more than three walls almost certainly will be discovered in the future. Each discovery of an additional wall will necessitate an additional terminology for that new group of cysts. To completely describe walls, cavities, and bodies of single-walled, two-walled, and three-walled cysts, without implying homologies, presently requires eighteen distinct terms. The addition of a four-walled cyst type would increase the total number RAYMOND L. COX: DINOFLAGELLATE CYST STRUCTURES 25 of necessary terms to thirty. The confusion that such a complex array of terms would engender could smother effective communication. Ectophragm is defined by Bownie and Sarjeant as a special type of membranous wall that rests on the tips of periphragm processes. Since the periphragm is defined as the outer of two walls, the ectophragm must be a third wall. However the term is not defined as a third wall nor do its authors clarify its usage in their published works. Other terms are used to denote structures similar to their ectophragm. Williams and Downie use ‘membrane’ in their description of Membranilarnacia (19 66b, p. 219), WetzelieUa ( WetzelieUa ) coelothrypta (1966a, pp. 185, 186) and Cyclonephelium divaricatum (19666, p. 244) and ‘periphragm’ in their description of Thalassiphorci (1966 b, p. 325). In their remarks on Chlamydophorella nyei Cookson and Eisenack, Davey et al. use ‘outer membrane’ (1966, p. 168). The terminology proposed by Downie and Sarjeant is not satisfactory for the designa- tion of walls and cavities. Unless we adopt a terminology that is not affected by changes resulting from new observations, we will have to retain the system proposed by these authors and continually readapt it to accommodate new information. The resulting patchwork terminology will be needlessly complex and obscure. Our need is for a terminology that is simple and objective, one that does not imply developmental simi- larity and does not need revision with each new discovery. The terms (wall, cavity, and body) should be retained as the basis of designates for these cyst structures. These terms are defined in a manner most appropriate to this study in the Random House Dictionary of the English Language (1966). Wall. 6. The outermost film or layer of structural material protecting, surrounding, and defining the physical limits of any object: the wall of a blood cell (p. 1606). Cavity. 2. Anat. a hollow space within the body (p. 236). Body. 1. The physical structure and material substance of an animal or plant, living or dead. 10. Geom. a figure having three dimensions of length, breadth and thickness (p. 165). Walls are considered in both two- and three-dimensional senses: In the two-dimen- sional sense, the surfaces (inner and outer) of the walls take on importance. Sculptural and structural elements arising from or indented into the surfaces and the patterns the elements make on the surfaces are among the most important of cyst features to be described. The wall is a three-dimensional structure in the sense that it has length, breadth, and thickness. In respect to dinoflagellate cysts, three dimensional aspects of walls should include thickness, pores, depressions, thin areas, thickenings, internal texture and wall continuity. A cyst body is formed by a wall having such a configuration that it encloses space. The space may be empty (e.g. PI. 7, figs. 1, 2, 4, 6) in which case it is a cavity, or it may be partially filled (e.g. PI. 7, figs. 3, 9, 10a, 12a), and consist of a cavity and an inner body. A wall and the enclosed space together constitute a body (e.g. PI. 7, figs. 3, 9, 10a, 106, 1 la, 116). The cyst body has a characteristic shape and volume. Specifically, the shape and dimensions of the body are distinct from those of the wall. For example, the shape of a cyst in dorsal-ventral view is the shape of the body, not of the wall. Wilson (1967, p. 477) referred to the rhomboidal outline of the periphragm when what he probably meant was the rhomboidal outline of the body delimited by the peri- phragm. Because a dinoflagellate cyst may have one, two, three, and possibly more 26 PALAEONTOLOGY, VOLUME 14 walls, each of which encloses space, it can consist of one, two, three, and possibly more bodies, one within another. Of significance in descriptions of bodies are the degree of dorsal-ventral flattening and the development of surface projections and any other factors that control their shape. The cavity of a single-walled cyst is the volume of empty space enclosed by the wall (PI. 7, figs. 1, 2, 4, 6). When two walls are present, one within the other, the inner cavity lies within the inner wall and the outer cavity lies between the two walls. This outer cavity is continuous when its bounding walls are not visibly in contact (PL 7, fig. 3) discontinuous when these walls are locally in contact (PI. 7, fig. 9) and only locally developed when the walls are in contact over a large proportion of the cyst (PI. 7, figs. l(k, llu) and within hollow processes (PI. 7, fig. la). The outer wall may completely enclose the outer cavity or only partially enclose it when discontinuities are present in that wall, for example, the outer wall of Litosphaeridium (PI. 7, fig. la) forms hollow processes that often are open at their tips. These openings constitute discontinuities in the outer wall. It may be argued that cavities are not structures in the strict sense of the term. However, since the cavities of dinoflagellate cysts can be described in a three-dimensional sense, similar to bodies, they are herein referred to as structures. Downie and Sarjeant (1966) have shown that such features of these cavities as their EXPLANATION OF PLATE 7 Photographs were made using a Geological Survey of Canada (GSC) Leitz Ortholux microscope and camera (number 65-59). A Leitz 546-nm interference contrast filter was used to increase contrast. Photographs were made on Kodak Plus-X panchromatic film. Fig. 1. Broomeci sp. sensu Alberti 1961, x 500; sample 57, depth 1 142' 7"-l 152' 7", slide PAL-57D, 33-8— 116-8, GSC type specimen 25611, Ashville Formation, Albian. Fig. 2. Deflandrea sp., ventral view, X500; sample 119, depth 1020'-1025', slide PAL-1 19L, 45-1— 119-6, GSC type specimen 25612, Vermilion River Formation, Boyne Member, Santonian. Fig. 3. Deflandrea sp., dorsal view, X500; sample 119, depth 1020'-1025', slide PAL-1 19L, 24-3- 111-9, GSC type specimen 25613, Vermilion River Formation, Boyne Member, Santonian. Fig. 4. Forma A, X 500; sample 58, depth 780'-787-5', slide PAL-58D, 36-3-124, GSC type specimen 25614, Vermilion River Formation, Morden Member, Turonian. Fig. 5. Chlamydophorella nyei Cookson and Eisenack; sample 56, depth 1192' 7"-l 202' 7", slide PAL- 56E, 1 5-7—1 15-5, GSC type specimen 25615, Ashville Formation, Albian. 5a, X500. 56, Apical region, X 750. Fig. 6. Dinogymnium sp., dorsal view, X500; sample 115, depth 915'-920/, slide PAL-1 15a, 29-8- 109-8, GSC type specimen 25616, Lea Park Formation, Campanian. Fig. 7. Litosphaeridium siphoniphorum (Cookson and Eisenack) Davey and Williams; sample 1, depth 929' 2"-937', slide PAL-1 a, 16-2-114-6, GSC type specimen 25617, Ashville Formation, Ceno- manian. la, x500. lb. Enlarged processes, x750. Fig. 8. Spiniferites sp., X500; sample 103, depth 1255'— 1260', slide PAL-103a, 40-7—1 19-5, GSC type specimen 25618, Ashville Formation, Albian. Fig. 9. Dingodinium sp., X500; sample 90, depth 1320-1325', slide PAL-90a, 39-2-117, GSC type specimen 25619, Ashville Formation, Albian. Figs. 10, 11. Forma B, dorsal view. 10a, 106, Sample 57, depth 1238' 2"-1245', slide PAL-57d, 25-5- 124-7, GSC type specimen 25620, Ashville Formation, Albian. 10a, x500. 106, Operculum and apex enlarged, X750. 11a, 116, Sample 55, depth 1142' 7"— 1 1 52' 7", slide PAL-55a, 20-124-4, GSC type specimen 23786, Ashville Formation, Albian. 11a, x500. 116, Enlarged apex, X750. Fig. 12. Forma C, ventral view; sample 692-3, 49'-58' above base of cliff, slide PAL-692-3a, 28-8- 111-1, GSC type specimen 25621, Late Cretaceous. 12a, X500. 126, Optical view of walls and processes, X750, 1 2c, Apical region, X750. Palaeontology, Vol. 14 PLATE 7 7*"' COX, Cretaceous dinoflagellate cysts RAYMOND L. COX: DINOFLAGELLATE CYST STRUCTURES 27 presence or absence, degree of development, shape, and symmetry of distribution (text- fig. 2c) are taxonomically useful. I propose to use wall, body, and cavity as the basic terms for all walls, bodies, and cavities in dinoflagellate cysts and to make clear the number and positional relation- ship of these structures in any one cyst by a simple system of numbers, as indicated in Table 2 (note that the numbering begins always with the innermost structures) : table 2. Proposed terminology for the designation of dinoflagellate cyst walls, bodies, and cavities For single-walled cysts: For double-walled cysts: For three-walled cysts: Wall 1 (i.e., the wall) Cavity 1 (i.e., the cavity) Body 1 (i.e., the body) Wall 1 (i.e., the inner wall) Wall 2 (i.e., the outer wall) Cavity 1 (i.e., the cavity within wall 1) Cavity 2 (i.e., the cavity between wall 1 and wall 2) Body 1 (i.e., the inner body) Body 2 (i.e., the outer body) Wall 1 (i.e., the inner wall) Wall 2 (i.e., the middle wall) Wall 3 (i.e., the outer wall) Cavity 1 (i.e., the cavity within wall 1) Cavity 2 (i.e., the cavity between wall 1 and wall 2) Cavity 3 (i.e., the cavity between wall 2 and wall 3) Body 1 (i.e., the inner body) Body 2 (i.e., the middle body) Body 3 (i.e., the outer body) The advantages of the proposed terminology are : 1. Simplicity: The terms wall, cavity, and body are simple and easily understood. Each designate is based on only one parameter that is normally easily observed: the spatial position of the structure relative to the centre of the cyst. An individual term should convey no more information than spatial position. 2. Consistency: For example, the innermost wall is always wall 1, regardless of its physical properties. 3. Symbolism: The use of numbers in orderly sequence quickly establishes a mental picture of the position of the structure. The numbers are easily verbalized and written. 4. Utility: The system is open-ended, new observations will not alter the basic concept of the designates which can be expanded to accommodate new information. For example, the outer wall of a four-walled cyst will be wall 4, and the outer wall of a cyst with n number of walls will be designated wall n. Alternative systems were considered before the proposed terminology was adopted. The designates inner, middle, and outer were rejected because a system formed using these terms would not be open-ended. The discovery of cysts with more than three walls would force another revision of such terminology. Various number and letter 28 PALAEONTOLOGY, VOLUME 14 combinations were tried. For example, terms for the inner, middle and outer walls of a three- walled cyst were designated respectively as wall 1 of 3, wall 2 of 3, and wall 3 of 3. Although it is open-ended and probably less prone to homologous interpreta- tions than any other system, this system was found to be awkward and confusing when used repeatedly in taxonomic descriptions and so was rejected. text-fig. 1. Single-walled cysts, a , Deflandrea sp., X c. 500, Plate 7, fig. 2; b, Broomea sp. sensu Alberti, 1961, xc. 500, Plate 7, fig. 1; c, Forma A, xc. 500, Plate 7, fig. 4; d, Dinogymnium sp., xc. 500, Plate 7, fig. 6. Examples of dinoflagellate cysts illustrating application of the proposed terminology are shown on Plate 7 and on text-figs. 1, 2, 3, and 4. Plate 7, figs. 1, 2, 4, and 6 and text-fig. 1 illustrate single-walled cysts. Plate 7, figs. 3, la, lb, 8, and 9 and text-fig. 2 illustrate cysts with two walls. An example of a three-walled cyst is given on Plate 7, figs. 10 a, 106, 11a, and 116 and on text-fig. 3. Plate 7, figs. 5a, 5b, 12 a, 12 b, and 12c and text-fig. 4 show examples of cysts where the number of distinct walls is so difficult to determine that until more, detailed studies are made, terminology for the structures cannot be regarded as final and any terms used must be accompanied by qualifying statements RAYMOND L. COX: DINOFLAGELLATE CYST STRUCTURES 29 Two specimens of Deflandrea sp., from the same lithologic sample, are illustrated on text-figs. 1 a and 2a. In text-fig. 1 a, the cyst consists of only one body (body 1). This body has a peridinioid outline. In text-fig. 2 a it consists of two bodies, an inner body (body 1) and an outer peridinioid body (body 2). Examples of the absence of such an inner body are common among peridinioid dinoflagellates. The reason, or reasons, Cavity 2 text- fig. 2. Two-walled cysts, a, Deflandrea sp., X c. 500, Plate 7, fig. 2; b, Litosphaeridium siphoniphorum (Cookson and Eisenack) Davey and Williams, x c. 500, Plate 7, fig. 7a; c, Dingodinium sp., X c. 500, Plate 7, fig. 9; d, Spiniferites sp., xc. 500, Plate 7, fig. 8. for such a phenomenon is unknown. It may be biological, palaeoecological, or dia- genetic or a combination of these factors. Because these cysts (text-figs. 1 a and 2ci) are similar in all other features, they are probably conspecific. Application of the proposed terminology to these cysts is not completely satisfactory. It is awkward to refer to two obviously homologous structures (i.e. the peridinioid bodies) using different designates. However, it is at this point that the decision must be made to use terminology in a purely objective sense: to record only what is observed. Furthermore, future studies of the presence or absence of a given body may reveal new palaeoecological, biological, 30 PALAEONTOLOGY, VOLUME 14 or diagenetic differences. Reference to both peridinioid bodies by the same designate may obscure the significance of such differences. Litosphaeridium siphoniphorum (Cookson and Eisenack) Davey and Williams (text- fig. 2b) is interpreted as having two walls and therefore two bodies and two cavities. The innermost wall outlines a subspherical body, body 1 . It is distinct only beneath the processes. Wall 2 arises as a distinct wall at the bases of the processes ; it forms the pro- cesses. Cavity 2 is discontinuous; it is clearly defined only within the processes. Body 2 may be said to be echinate; the spines being hollow, blunt, and open-ended. Whether such cysts as Hystrichosphaeridium , Oligosphaeridium, and Tanyosphaeridium also have two walls will be determined by further study. text-fig. 3. Three-walled cysts, a, b. Forma B, x c. 500, Plate 7, figs. 10a, 11 a respectively. Dingodinium sp. (text-fig. 2c) illustrates a discontinuous cavity that is asymmetrically disposed about an apical-antapical or polar axis. This feature appears constant for Dingodinium and therefore is of taxonomic value. Spiriferites sp. (text-fig. 2d) is interpreted as a two-walled cyst based on studies by Jux (1968) and on personal investigations. The inner wall bounds a subspherical body. The outer wall forms the sutural lists and the gonal and intergonal furcate spines. Body 2 is echinate while cavity 2 is discontinuous and best developed near the base of the lists. Text-figs. 3 a and 3 b illustrate two specimens referred to here as Forma B, a three- walled cyst. In text-fig. 3b and Plate 7, figs. 1 1 a and 1 1 b, the three walls are well defined at the apex of the cyst. The operculum of Forma B consists of la, 2a, 3a, 3", 4", and 5"; this series of plates forms the operculum in all three bodies. In text-fig. 3a, although the dorsal surface of the specimen is obscured by complex folding of walls from the ventrum, the operculum clearly illustrates the presence of three walls. A small cavity is developed by the separation of two walls at the antapex. Presently it is not possible to distinguish which walls have separated so the terminology the antapical region is left open pend- ing further studies. Text-fig. 4 is included to illustrate some unresolved problems that can only be resolved by ultrathin sections and detailed microscopic analysis such as the study by Jux (1968). Text-fig. 4 a, Chlamydophorella nyeii is labelled as a two-walled cyst. If the processes that arise from wall 1 can be shown to constitute a new wall, then C. nyeii will be desig- nated as a three-walled cyst. Text-fig. 4 b illustrates Forma C which resembles Forma B in its mode of archeophyle formation. Forma C is here labelled as a three-walled cyst. Wall Cavity 2 or 3 RAYMOND L. COX: DINOFLAGELLATE CYST STRUCTURES 31 However if the processes between wall 2 and wall 3 can be shown to constitute a distinct wall, then Forma C becomes a four-wall cyst. The terms that designate the walls, cavities and bodies of C. nyeii and Forma C are therefore regarded as provisional. The terms suggested here are only tools. They are intended to be applied only after one decides on the cyst-type (number of walls present) and on the position of the structure being identified relative to the cyst centre. The decision as to whether a given J J J text-fig. 4. Cysts illustrating difficulties in the application of terminology: a , Chlamydo- phorella nyeii Cookson and Eisenack, x c. 500, Plate 7, fig. 5 a ; b. Forma C, x c. 500, Plate 7, fig. 12(7. layer, or partial layer, is a wall or not must be made prior to application of the termin- ology. If subjectivity is involved in this decision, then an explanation for the decision must accompany the term. It is hoped that this discussion will be useful insofar as it draws attention to a problem. The simplicity, versatility and graphic nature of the proposed solution to that problem should be apparent once the problem is appreciated. However, no system is a panacea and the value of any system depends as much on how it is used as on how it is designed. Information about samples. All specimens illustrated on text-figs. 1, 2, 3, and 4 and on Plate 7 were recovered from shale samples of Cretaceous (Albian to Maestrichtian) age. Samples 1, 55, 56, 57, and 58 were obtained from the International Minerals and Chemical Co. k2 potash shaft (lsd. 7, seen. 27, twp. 19, rge. 32 W 1 Meridian), south-east Saskatchewan. Samples 90, 103, 115 and 119 were obtained from Alwinsal Potash of Canada Ltd. potash shaft (lsd. 4, seen. 28, twp. 33, rge. 23, W 2 Meridian), south Saskatchewan. Sample 692-3 is from the outcrops along the Horton River, Northwest Terri- tories, about 15 miles south of its mouth (lat. 69° 49', long. 126° 51'). Samples and slides are stored in the Geological Survey of Canada (GSC) type collection. GSC locality numbers for the samples are: sample 1 = C-5214, sample 55 = C-5223, sample 56 = C-5222, sample 57 = C-5221, sample 58 = 69318, sample 90 = C-5249, sample 103 = C-5246, sample 115 = C-5221, sample 119 = C-5234, sample 692-3 = C-5272. Acknowledgements. During the preparation of this paper valuable comments and criticisms were offered by W. R. Evitt of Stanford University, W. S. Hopkins of the Geological Survey of Canada, D. Wall of Woods Hole Oceanographic Institute, and G. Norris of the University of Toronto. Their help is greatly appreciated. 32 PALAEONTOLOGY, VOLUME 14 REFERENCES clarke, r. f. a. and verdier, j. p. 1967. An investigation of microplankton assemblages from the Chalk of the Isle of Wight, England. Verhandelingen koninklijke Ned. Akad. Wetenschappen, Natuurkunde, 24 (3), 1-96, pis. 1-17. cookson, i. c. and eisenack, a. 1958. Microplankton from Australian and New Guinea upper Meso- zoic sediments. Proc. Roy. Soc. Victoria, 74 (1), 19-79, pis. 1-12. 1962. Additional microplankton from Australian Cretaceous sediments. Micropaleontology, 8, 485-507, pis. 1-7. davey, r. j. 1969. Non-calcareous microplankton from the Cenomanian of England, Northern France and North America. Bull. Brit. Mas. Nat. History ( Geol .), Suppl. 17 (3), 103-80, pis. 1-11. downie, c., sarjeant, w. a. s., and williams, g. l. 1966. Fossil dinoflagellate cysts attributed to Baltisphaeridium, in Studies on Mesozoic and Cainozoic dinoflagellate cysts. Ibid. Suppl. 3, 157-75, pis. 2, 3, 8-11. downie, c. and sarjeant, w. a. s. 1966. The morphology, terminology and classification of fossil dinoflagellate cysts, in Studies on Mesozoic and Cainozoic dinoflagellate cysts. Ibid. Suppl. 3, 10-17. drugg, w. s. 1967. Palynology of the Upper Moreno Formation (late Cretaceous-Paleocene) Escarpado Canyon, California. Pa/aeontographica, 120B, 1-71, pis. 1-9. and loeblich, a. r. jr. 1967. Some Eocene and Oligocene phytoplankton from the Gulf Coast, U.S.A. Tulane Studies in Geology, 5, 181-94, pis. 1-3. evitt, w. r. 1961. Observations on the morphology of fossil dinoflagellates. Micropaleontology, 7, 385-420, pis. 1-9. - — - — ■ 1967. Dinoflagellate studies 11. The archeopyle. Stanford Univ. Publ., Geol. Sci. 10 (3), 1-83, pis. 1-11. and wall, d. 1968. Dinoflagellate Studies IV. Theca and Cyst of Recent Freshwater Peridinium limbatum (Stokes) Lemmermann. Ibid. 12 (2), 1-15, pis. 1-4. jux, u. 1968. Uber den feinbau der wandung bei Hystrichosphaeridium bentori Rossignol 1961. Palaeontographica, 123B, 147-52, taf. 31. manum, s. and cookson, i. c. 1964. Cretaceous microplankton in a sample from Graham Island, Arctic Canada, collected during the second ‘Fram’ — Expedition (1898-1902) with notes on micro- plankton from the Hassel Formation, Ellef Ringnes Island. Skrifter utgitt av det Norske Videnskaps- Akad. i Oslo 1, Mat.-Naturv. Klasse, Ny Serie, 17, 1-36, pis. 1-7. norris, g. 1965. Archeopyle structures in upper Jurassic dinoflagellates from southern England. New Zealand J. Geol. Geophys. 8, 792-806, 2 pis. pocock, s. a. J. 1962. Microfloral analysis and age determination of strata at the Jurassic-Cretaceous boundary in the western Canada plains. Palaeontographica, 111B, 1-95, pis. 1-15. sarjeant, w. a. s. 1966a. Dinoflagellate cysts with Gonyaulax- type tabulation, in Studies on Mesozoic and Cainozoic dinoflagellate cysts. Bull. Brit. Mus. Nat. History (Geol.), Suppl. 3, 107-56, pis. 13-16. 1966 b. Further dinoflagellate cysts from the Speeton Clay (lower Cretaceous), in Studies on Mesozoic and Cainozoic dinoflagellate cysts. Ibid. Suppl. 3, 199-214, pis. 21-3. singh, c. 1964. Microflora of the lower Cretaceous Mannville Group, east-central Alberta. Bull. Res. Council of Alberta, 15, 1-238, pis. 1-29. Stanley, e. a. 1965. Upper Cretaceous and Paleocene plant microfossils and Paleocene dinoflagellates and hystrichosphaerids from northwestern South Dakota. Bull. Am. Paleontol. 49 (222), 175-384, pis. 19-49. stein, j. (ed. in chief) 1966. The random house dictionary of the English language, the unabridged edition. New York. wall, d. and dale, b. 1968. Modern dinoflagellate cysts and evolution of the Peridiniales. Micro- paleontology, 14 (3), 265-304, pis. 1-4. williams, G. l. and downie, c. 1966a. Wetzeliella from the London Clay, in Studies on Mesozoic and Cainozoic dinoflagellate cysts. Bull. Brit. Mus. Nat. History (Geol.), Suppl. 3, 182-98, pis. 18-20. 19666. Further dinoflagellates from the London Clay, in Studies on Mesozoic and Caino- zoic dinoflagellate cysts. Ibid. Suppl. 3, 215-35, pis. 24-6. wilson, G. J. 1967a. Some new species of lower Tertiary dinoflagellates from McMurdo Sound, Antarctica. New Zealand J. Bot. 5, 57-83, 6 pis. RAYMOND L. COX: DINOFLAGELLATE CYST STRUCTURES 33 wilson, g. j. 19676. Some species of Wetzeliella Eisenack (Dinophyceae) from New Zealand Eocene and Paleocene strata. Ibid. 5, 469-97, 5 pis. 1968. Palynology of some lower Tertiary coal measures in the Waihao district, South Canter- bury, New Zealand. Ibid. 6, 56-62, 1 pi. RAYMOND L. COX Douglas College 332 Columbia Street, New Westminster, Revised typescript received 12 June 1970 British Columbia, Canada C 7895 D TAXONOMY OF DICOELOSIID BRACHIOPODS FROM THE ORDOVICIAN AND SILURIAN OF THE EAST BALTIC by M. RUBEL Abstract. The sequence of taxonomic procedure is considered to be : (1) a definition of the morphological basis, (2) a determination of the variability, (3) an examination of the evolutionary rates against the stratigraphic background, (4) a grouping directed towards the formation of rational taxa, and (5) the comparison of these taxa with existing taxa and the modification of these taxa. Any kind of numerical methods in palaeontology must also consider this procedure. These problems are discussed in relationship to the East Baltic dicoelosiids : Dicoelosia anticipata, D. aff. osloensis, D. osloensis, D. biloba, D. oklahomensis, Epitomyonia glypha of Ash- gillian to Ludlovian ages. Descriptions and occurrences of these species are given. The study of Dicoelosia biloba (L.) and related species (Wright 1968a) is an intriguing basis for a systematic study of material from the East Baltic. The phylogeny of Dicoelosia has been used as a basis for intercontinental correlation (Amsden 1968, text-fig. 21) and this aspect has also prompted the present study. The collection includes 92 well-preserved specimens of the family Dicoelosiidae Cloud 1948, from borehole cores in Latvia and Estonia and outcrops in Estonia. The identification or comparison of new specimens with described material is very much concerned with variability. The variability of brachiopod species may be demon- strated in several ways. Calculation of the morphological variability of each sample has been used here for a numerical appraisal. Theoretically, each sample must be taken from one local fossil population (Imbrie 1956). The samples used here have been taken from core intervals or from particular beds at outcrop. Observation suggests that each sample of Dicoelosia or Epitomyonia is from a homogeneous population. The samples may be arranged into groups by special techniques. The rank and name of each such group are obtained by comparison with type material of known taxa on the same morphological basis. In general the dicoelosiids are more closely associated with the graptolitic than the shelly facies and in most cases the samples can be correlated with a graptolite zone. The graptolite zonation used is that of R. EJlst (in Gailite et al. 1967) and D. Kaljo (personal communications). Acknowledgements. The material used in this work was assembled from the following collections: the large Latvian collection studied by M. Rybnikova (in Gailite et al. 1967), the Ordovician species from Estonia described by L. Hints (MS) and topotypes and species described by A. Wright (1968n). It is a pleasure to record the assistance received from L. Shtsherbakova during the study of Latvian brachiopods. K. Kajak and E. Kala kindly presented the material from Estonian borings. The correla- tion coefficients of ratios (Table 2) and distances between specimens (see below) were calculated at the Computation Center of the Estonian Academy of Sciences using programs made available by I. Petersen and M. Karolin. I am very thankful to R. Goldring (University of Reading) who has taken so much trouble in reading and correcting my manuscript. [Palaeontology, Vol. 14, Part 1, 1971, pp. 34-60, pis. 8-10.] M. RUBEL: TAXONOMY OF DICOELOSIID BRACHIOPODS 35 text-fig. 1. Location of borings and outcrops. MATERIAL The samples have been numbered consecutively S1; S2, etc. followed by the location and depth in the borehole or location of the outcrop, and the number of shells measured. The numbered geographical location and stratigraphic position of each sample are shown in text- figs. 1 and 2. These numbers are shown between brackets in the list below. A. Samples with measured specimens Si Ezere (0 1056-0 m 18 S2 (1) 1059-0 m 2 s3 (1) 1077-3 m 5 S4 (1) 1077-6-1077-7 m 8 S5 (1) 1078-95 m 5 S6 Mezciems (2) 331-2 m 1 S, Akniste (3) 542-5-542-7 m 1 S8 Staicele-4 (4) 280-6 m 1 s9 (4) 280-3 m 1 Sio (4) 279-7 m 1 Su (4) 276-6 m 4 Si2 (4) 276-0 m 2 Sl3 (4) 275-0 m 1 Si4 Pavilosta (5) 736-5 m 8 S« Kolka-54 (6) 400-9 m 3 Sl6 (6) 445-8-446-0 m 1 Si7 (6) 574-3 m 1 36 PALAEONTOLOGY, VOLUME 14 Sis Kolka-54 (6) 605-7 m 1 Sl9 Holdre (7) 348-8 m 2 S2„ (7) 304-9 m 1 s« (7) 304-1 m 1 s22 (7) 301-5 m 1 S23 (7) 295-5 m 1 S24 Kabala (8) 1 1 1-8-112 0 m 4 S25 Ohesaare (9) 372-95-373-0 m 1 S26 Ikla (10) 276-3 m 2 S27 (10) 277-0 m 1 S28 (10) 28 1 -0 m 1 S»9 (10) 286-0 m 1 S30 Ristikula (ID 160-9 m 1 S3I Parnu (12) 89-5 m 2 8>32 (12) 90-40-90-44 m 1 S33 (12) 91-68-91-72 m 4 S34 Latikiila (13) Material excavated from strata on the bottom of the river 2 S35 Saxby (14) Material derived from the upper 0-5 m of a small quarry 3 b. Samples with fragmentary preserved specimens S3G Moe (15) Material derived from the upper 0-5 m of a small quarry 2 S37 Aiamaa (16) 133-53-133-56 m 2 S38 Seliste (17) 334-1 m 1 S39 Haademeeste (18) 394-6 m 1 S40 (18) 390-9 m 1 S41 (18) 343-0 m 1 S42 (18) 213-7 m 2 S43 (18) 206-8 m 1 S44 Ikla (10) 482-0 m 2 S45 (10) 287-0 m 4 S46 Abja (19) 271-8 m 1 S47 Staicele-4 (4) 400-3 m 1 S48 (4) 345-0 m 1 S49 (4) 341-0 m 1 S50 (4) 281-5 m 1 S.1 (4) 279-0 m 1 S52 (4) 275-5 m 4 S53 Kolka-54 (6) 605-4 m 2 S54 (6) 604-3 m 1 S55 (6) 603-0 m 2 S56 (6) 461-0 m 2 S57 Druvas (20) 274-2 m (Gailite et al. 1967, P- 175) 0 S58 (20) 258-4 m (ibid.) 0 S59 Koinastu (21) Material from a small cliff 1 $60 Viesite (22) 626-3 m (Gailite et al. 1967, p. 175) 0 Sei Ristikula (ID 161-6 m 1 Sg2 (ID 160-8 m 1 ^63 (ID 154-2 m 1 $64 Pavilosta (5) 731-5 m 1 Se5 (5) 723-5 m 1 ^66 Ezere (1) 1052-0 m 3 ^67 Mezciems (2) 347-85 m (Gailite et al. 1967, p. 175) 0 ^68 Vohma (23) 192-0 m (Wright 1968a, p. 302) 0 M. RUBEL: TAXONOMY OF DICOELOSIID BRACHIOPODS 37 4* Pristiograptus ultimus Pristiograptus tumescens Lobograptus scamcus tleodiversograptus m/ssoni Monograptus testis Cgrtograpfus perneri Monograptus f/exi/is Monographs riccartonensis Cgrtograpfus murchisom Oktavites spiralis B/obosograpfus crispus Spirograpfus turncutatus Monographs sedgwicki Bem/rasfrifes oonvotutus Demirastrites triangutatus Pristiograptus cgphus Cgstograpfus vesicutosus Bicellograptus anceps Dicellograptus comptanatus Pteurograptus linearis (1) (5) (6) (9) (11) (12) (10) (13) (13) (21) (9) (20) (7) (19) (17) (8) (19) (15) (IE) (23) (3) (22) (2) 66 69,66 1-5 19 68 text-fig. 2. Distribution of samples according to locality numbers. The graptolitic zones follow R. Ulst (in Gailite et al. 1967, text-fig. 6) and modified by D. Kaljo (pers. comm.). The samples with numbers 1-5, 14, 64-66 are assigned to Dicoelosia oklahomensis ; 6-13, 15, 16, 26-28, 30-33, 50-52, 56, 61-63 to D. biloba; 29, 42, 43, 45 to D. sp. indet.; 17, 18, 20-23, 25, 34, 53-55, 59 to D. osloensis; 19, 38-41, 44, 46-49 to D. aff. osloensis; 24 to Epitomyonia glypha; 35-37 to D. anticipate!; 68 to D. transversa; and 57, 58, 60, 67 to D. spp. The specimens used in this study are preserved at the Geological Museum of the Estonian Academy of Sciences (Tallinn) and the All-Union Scientific Research-Institute of Marine Geology (Riga). Catalogue numbers are indicated with the initial letters \Br’ and ‘Br 30/’ respectively. The numerical data are stored at Tallinn. MORPHOLOGICAL BASIS Every morphological feature may be represented by a certain number of measure- ments. These make it possible to estimate the morphological variability numerically. Eighteen measurements on the shell (see text-fig. 3) are used in this study. The measure- ments are, in part, those used by Wright (1968a, b). The level of identification and other conclusions are governed by these measurements, and I consider that they are superior to any visual estimation. 38 PALAEONTOLOGY, VOLUME 14 The measurements taken are concerned with the shell shape. The ribbing, capillae, sulci, and cardinal extremities normally considered in descriptions of dicoelosiids are excluded from this inspection. ?,4J0’" 2 « text-fig. 3. Positions of measurements made on the material. At the same time most individual measurements express a growth stage of a shell. Comparisons of values obtained from very young specimens of one species with those from gerontic specimens of another taxon show differences in rate of growth rather than taxonomic position. Taxonomically of course they do differ. The simplest way to exclude the growth factor is to express the measurements as ratios, i.e. : 1 . Maximum length (x2) : maximum width (at) of pedicle valve. 2. Maximum length (x3) : maximum width (x1) of brachial valve. 3. Maximum length of pedicle valve (x2) : maximum length of brachial valve (x3). 4. Mid-line length (x4) : maximum length (x2) of pedicle valve. 5. Mid-line length (x4) : length along rectilinear rib as (x10'+x10")/2 of pedicle valve. 6. Width of interarea (x6): maximum width (x4). 7. Lobes width as (%+xu*)/2: lobes length as (x12'+x12»)/2 of pedicle valve. M. RUBEL: TAXONOMY OF DICOELOSIID BRACHIOPODS 39 8. ‘Lobes divergence’ (x9): length along rectilinear rib as (x10'+x10")/2 of pedicle valve. 9. Maximum thickness (x13) : maximum length (x2) of pedicle valve. 10. Distance 14-14 (xu) : maximum length (x2) of pedicle valve. 11. Distance 17-17 (x17): maximum distance 18-18 (x18). 12. Distance 16-16 (x16): distance 15-15 (x15). Note: if the brachial valve is convex or flat then x16 = 0, and if the brachial valve is convex then x15 = 0. It is well known that young specimens of different taxa are more similar than are the adults, and this feature is particularly clear with the present material. For this reason specimens with the pedicle valve less than 2-0 mm have been discarded, reducing the number of specimens studied numerically to 75. In order to simplify further calculation the ranges of all ratios are divided into ten classes, each of which is coded by the ordinal number 1 to 10. The class-intervals of each such ratio are summarized in Table 1. table 1. Class- intervals of ratios in the East Baltic collection of dicoelosiids Ratios *2/Xl xJxl XJX3 XJX 2 xJx 10 XJX1 Maximum 1-028 0-932 1-243 0-938 0-891 0-776 Minimum 0-643 0-559 0-949 0-637 0-575 0-406 Class-interval 0-039 0-039 0-031 0-031 0-033 0-038 Ratios xlllxl2 •Wwo XlslX2 xlilx 2 xislxn x1gIx15 Maximum 2-909 1-040 0-509 0-613 0-150 0-147 Minimum 0-891 0-536 0-194 0-336 0-025 0-000 Class-interval 0-202 0-052 0-032 0-029 0-014 0-015 The ratios studied throughout the collection have a certain degree of correlation between them. These coefficients are just the basis on which the weighting of their diagnostic values lies, and, more important, from which the operational features may be defined. Thus, the ratios with a high degree of correlation may be regarded as uni- directional factors or, simply, diagnostic features. The features so defined have an equal weighting in subsequent taxonomic procedures. The correlation between all pairs of coded ratios, X and Y, is computed by the estimator, r = cov X, T/(var X var Y)l,z. The statistically significant correlation between most ratios (Table 2) allows them to be regarded as a co-operative system in the whole collection. The maximum informa- tion of the multivariate system is obtained by arrangement of its variates into such a scheme where n variates are linked with n — 1 lines so that a sum of the coefficients of correlation along these lines is maximal (Vohandu 1964). The corresponding scheme for the ratios is given in text-fig. 4. It is used here for the selection of the most diagnostic ratios. They include the ratios x?jxx, x14/x2, x16/x15, xjxw, xjx3, .rjxy, x13/x2, and x18/.v17. Although these ratios are significantly correlated after their maximal correlation lines (with the exception of xislxn) they do it relatively in like manner, especially in relation to the ratios of high degree of correlation, e.g., the ratios x2/x1, xjx^ and x9/x10. Each ratio chosen may be regarded as representative of one feature. Only they are used as a morphological basis for further calculation. 40 PALAEONTOLOGY, VOLUME 14 M'«Doooor)ONfSt^O,tO < ^Door]»yn^^t-Ttr-rN|TtoO "5 OOOO^-^-hOOOOO £ 66666666 666^ III III H •— .vo — roin'00 O^OOn — rj-rtoooo „0"«n«N«o S-i OOOOOOOO-1* I I o o . .a 2 c3 N CQ C c3 PJ h^T)-MO\fNMO OOp^pp0 Oi ^ o O ri M i-' rn rn O * 666666^ ■2 ft, 2^ ”0 C o) S ■7-5 c^» O cr- o .6 c — .2? -+-* *00 c »h r£? > "'S m 1— 1 O 0\ 0\ OO O (N (N O rn O OOOO^ I I > OOM OnO O O ^ 't <0 tJ- O H 666-^ I I £ = + 1-000, ?7 = 3) in the Parnu boring, S20 — S21 — S23 — S22 (p = —0-129, 77 = 6) in the Holdre boring, and less regular series in the Staicele boring, Sio— S12 — Su — S9 and S8 — S13 (p = —0-067, n = 15). The degree of correlation is higher in series with larger samples. Some stratigraphically close samples are linked in order to give greater prominence to the evolution (Table 5). The linked samples are indicated, as for instance, S8+S9+S10 = S8^10. In the latter case the correlation between morphological and stratigraphic relationships is maximum. table 5. Sample distances between and within (framed) sample groups in the Staicele boring S S S 8-10 11 12, 13 $8-10 58-66 45-58 35-17 Sl2> 13 45-89 37-08 35-33 Depth in the core N (m) 3 280-6-279-7 4 276-7 3 276-0-275-0 Taxonomic problems arise because of the heterogeneity of linked samples. The linkage may increase the variability of linked samples and, therefore, decrease the possi- bilities of showing the degree of evolution prominently. On the other hand, if small samples are not linked no positive conclusions can be made. Therefore, in spite of the presumed evolution at the population level it is better to link some samples. The main evolutionary trend of the dicoelosiids (see Amsden 1968, text-fig. 21) can be seen in the continuously evolving sequences described above. Such unidirectional brachiopod lineages have been used at various levels of stratigraphic correlation as, for instance, in the Llandoverian with the genera Stricklandia, Eocoelia, and Leptostrophia (see Ziegler et a/. 1968). It is possible to classify the East Baltic collection through its main evolutionary trends. Table 6 demonstrates the evolution of features separately. There are on average at least two features changing regularly with time: the invagina- tion of shells (xjx10) decreases, whilst the brachial valves change from concave to convex (a16/x15), in stratigraphically younger specimens. These features are, of course, quite clear visually. M. RUBEL: TAXONOMY OF DICOELOSIID BRACHIOPODS 45 The corresponding distances between the sample groups (Table 7) increase according to their stratigraphic position, demonstrating the main trend. The amount of evolution is not surprising considering the length of time involved. There is one critical sample group, S8_13, which has one of its distances equal to its variability, namely, between the S8_13 and S26— 28, 30-33- That indicates the intermediate nature of the Upper Llandoverian dicoelosiids with those from the Wenlock in the collection (text-fig. 6). table 6. Averages and variances, s2 (in brackets), of the coded ratios after the sample groups in the collection Ratios XzlXl xnlX3 Xll X10 *6/*i xJ3/x2 xulx2 xi$/xn xielxis N Samples Sl-5, 14 7-30 (2-52) 3-88 (2-32) 5-03 (2-03) 3-42 (1-25) 3-91 (3-00) 3-09 5-45 (1-85) (4-32) 1-00 (0-00) 33 $26-28, 30-33 5-83 (3-46) 4-75 (E27) 4-00 (1 45) 4-83 (3 46) 4-33 (1-35) 4-17 4-92 (2-73) (1-35) 1-83 (2-36) 12 $8—13 6-30 (1-79) 4-50 (2-95) 3-60 (2-71) 3-20 (1-51) 3-20 (E51) 4-80 5-20 (4-18) (3-74) 3-40 (2-71) 10 $20—23 8-25 (1 00) 6-50 (0-33) 2-75 (2-92) 4-50 (1-67) 7-00 (2-00) 4-25 4-75 (0-92) (0-92) 6-75 (E58) 4 table 7. Sample distances between and within (framed) the sample groups in the collection S]-5, 14 $26-28, 30 -33 $8-13 $20-23 N Stratigraphy Si— 5, 14 33-98 40-62 48-47 83-48 33 Ludlovian $26-28, 30-33 34-61 42-18 66-19 12 Wenlockian $8-13 42-18 63-05 10 Upper Llandoverian 22-50 Middle Llandoverian TAXONOMIC GROUPING The ineffectiveness of existing clustering methods when applied to continuously evolving sequences of fossils by means of their pure morphology (Kaesler 1967) has become evident during the present study. It seems certain that the stratigraphic and ecological arrangements of the morphological variability add significant information (Westbroek 1967). The Groups 14, S26_28> 30-33, S8_13, and S20_23, may be regarded as representatives of one main evolving sequence. The known occurrences of each group are separated from each other by varying stratigraphic intervals. Therefore, they represent useful standards for taxonomy. In other words, the basic idea of classification of all samples appeared in a form according to Table 8 including the assignment of the ‘free’ samples to the standard groups. It may be done by the minimum distances of the ‘free’ samples but corrected finally by the estimation of the variability of new groups. In other words, the assignment of any ‘free’ sample to standard groups could be to decrease the variability of the new group or, at least, the increase of its variability must be minimal in relation to other possible linkage. The linkage must be ended on the critical level chosen. 46 PALAEONTOLOGY, VOLUME 14 O vo co co oo O O O O pf O O O 4 w ov vb vo vo — co inmr'icTO'.rororo (Noo-^ONr^-oocNr^ oo o ci 'S s fN 'O Ti OV IO vo vo o ov vo T3 C a C/5 Cl © o Q, £ c3 C/5 in co vo »0 in «/Y co co co JL> a ctf c/3 isiinvitfiviviviinviTSiinwisiviinisi M. RUBEL: TAXONOMY OF DICOELOS1ID BRACHIOPODS 47 ESTONIA LATVIA Kures- saare, K3a Paad/a. k2 Pools/ - kula , Kj Jaaga- rahu, J2 Jaani , Ji 0. oklahomensis I D biloba D sp in del #■ I Lud/o- v / a n VJ on lo- ck/an Adavere H Ra/kkula S3 0 os/oensist Juuru, Sj-2 g§ D aff os/oensis h Epifo myoma g/ypha Uan- d 0 ve- na n Porkum Ft E Pirgu, Tic -B. anhc/pata A sh- g/l- h an Vormsi. Tib "D. fransversa Caradoc. text-fig. 6. Distribution of taxa in terms of the Estonian stratigraphic scale. table 9. The assignments of the ‘free’ samples to the standard groups. 1, Standards. 2, Samples assigned by their minimal distances, within limits of each standard variability. 3, As 2, but within limits of the most numerous standard variability, 33-98. 4, Check of previous assignments by minimal increase of the standard variability after linkage of the indicated sample(s). 5, Final assignments by the minimal increase. 6, The closest samples by the minimal increase. In round and square brackets are indicated the minimal distances and the variabilities respectively 1 2 3 4 5 6 Si— 5, 11 [33-98] S6 [35-10] S29 [35-28] S26-28, [34-61] S15 (30-94) S15 [32-85] Sis 7 [33-58] S10 [35-08] 30-33 S7 [35-16] S„;7,i6 [33-67] S6 [36-79] §8-13 [42-18] S7 (32-20) Sv [40-37] S29 [44-04] $20-23 [22-50] S25 (20-75) Si, (27-75) S25 [21-80] $25, 18, 34, 17 S6 [39-89] S34 (30-75) S25, is [22-33] [31-67] S29 [42-13] S* .is .si [28-35] S19 [49-64] 48 PALAEONTOLOGY, VOLUME 14 Thus, the variability of the most numerous sample, Sl5 was 37-85. After assignments of the S2, S3, S4, S5, and S14 to it the variability of the new group, S4_5 14, decreased to 33-98. Both variability levels may be used in classification of the collection. The level 33-98 obtained by linkage of morphologically and stratigraphically close samples is critical in species determination. Such results obtained for this series are presented in Table 9 and appear to be very satisfactory. The three samples S19, S24, and S35 have too great distances between them- selves and from others, and must be considered as taxonomically independent. It is also noteworthy that the variabilities of the groups S4_5> 14, S26_28> 30_33, S8_13 are nearly equal to the distances between them. This is a sequence of relatively close standards. In conclusion, five or six groups satisfy taxonomically the requirements of ‘species’. Together with visual assignment of fragmentary preserved specimens (samples S36 to S68) the final classification of the collection is as follows: Group I: S,_5i 14, S64_66 Intermediate: S6 Group II: S26_28> 3o_33> S15, S7, S16, S56, S61_63 Intermediate: S8-13, S50_52 Intermediate: S29, S42, S43, S45 Group III: S20_23, S25, S18, S34, S17, S53_55, S59? Intermediate: S49, S38_44, S43_49, S44? Group IV : S24 Group V: S35, S36, S37 SYSTEMATIC PALAEONTOLOGY The preceding discussion of ‘shape taxonomy’ suggests its appropriateness in identi- fication. However, there is a greater variability in the morphology of all known species than in the material from the East Baltic. In calculation of the corresponding distances between the five groups (above) and the seven related species the rank scales are increased in both directions by means of the same class-intervals. The taxonomic relationships of the seven related species are shown in Table 10. Most species are represented by their type material. Unfortunately, no exact horizon or locality was ascribed to the type material of Dicoelosia biloba and D. verneuiliana (Wright 1968u). The same features are used in the construction of Table 1 1 as for the East Baltic collection so that direct comparisons of the sample distances can be taken for the follow- ing nomenclatorial conclusions. Family dicoelosiidae Cloud 1948 Genus dicoelosia King 1850 Dicoelosia anticipata Wright 1968 Plate 8, figs. 1-7 1968a Dicoelosia anticipata Wright, pp. 308-9, pi. 5, figs. 15-19. Description of topotypes. Pedicle valve from five-sixths to two-thirds as long as wide, mid-line length just five-sixths of maximum valve length. Valve thickness averages M. RUBEL: TAXONOMY OF DICOELOSIID BRACHIOPODS 49 o ri I © - C Q, o CJ o* X> 03 co SG s .2 8 "3 2 1 ° §. S T3 O C (D 03 Oh „ • >< 60 v * w ts : S 5 « »V 0 ex) to -cj ; cc cn ^ : — : a ft „ 5 <3 R ) 00 00 ■ vo fzr - r \j vo , ^ Cd 00 CO ON On a\ * ■ SS “ - - „ 'O r-( "p, fl d .£P.£t g-cSES' M3 — „T3 O O ' '•U H R *-J _ 42 2 4 J-H *-H C ✓ W- W c/D ) h CO £ joo^ . . . r~~ 5 O O 22o h e- &h _ , 3 g s s s 5 .5 5 _g , • : ~C> -Ci »C> -C> • o o o o O O -Cj -O -Q -O =>• **» j^» 5 M . . T 1 fefi v5 CO ^ ^ cC CD OB • • ^ rr-1 tr-1 co cn ^ 60 SO >/~) [2* bP 00 ^ — . [^ r- 7 7 5 6 600 6 6 looz* w PL, pH £ o Q - * &H CU <: .to .5 ^ § g ^ 3 3 ? 5j ^ ^ 1 •§■§■§■§ C3 © © -S .5 0\0\P>r^(St^m>ooO'tNoooom Cx, (Nt^^riOV'nmfNM'^ooM'nr' ^(Nmm^fNMcovorjrontM ■'tvO'tv^NtvO'tr^mmOvr'r' I R vO'-iM^'nr'r'iOrioo'TONOO I _ inNinnnfn-iMO'T'O'^ I ~ O't'om'O'too’too'tfnN I *-H — < ri CO r-H mt^-ir)ONmf^mOo _ 1 <0 _ Os O O on ^ 00 n o \t" to 00 CN (N »0 vo r- ^ 00 ^ 00 o 00 r~~. o ph VD 00 NO 1^ M ON ^ O On 9 ^ 22 2 H M ^OO Tt* ro rf Tf • O o 2? on to tJ- <5 cj O o < Os vo ' to P to ^ o vo O ,—1 ’troEl 00 *"< o o o o o vo p ’t O -^f On (N io ’t m ^ co ^ o on o r-'* m rr, NO a ?§ g 3 g E 3 S 3 E g £ g E 3 £ d a „-£ E £ E E s s £ £ E £ Is I S a 2 >< V & 'E 2 « ’5 >< a> cC *3 *x rx cd ‘a .n cd SwS % § 7?S s 72 § 2 72 S s c/?S M. RUBEL: TAXONOMY OF DICOELOSIID BRACHIOPODS 51 a little more than one-third of maximum length, moderately convex in lateral profile. Lobes broad, divergence of about 49-63°, gently convex in transverse profile and separated by well-developed sulcus originating at umbo. Hinge-line slightly more than half shell width; cardinal extremities obtuse, ears weakly developed. Sulcus defined by first costae fairly well developed, 0-6-14 mm wide at 2 mm growth stage. Ribbing well developed over whole shell surface, with 8-9 costae ; costellae commonly arising by bifurcation; capillae also developed. Ribs fairly angular, with 4-6 ribs per mm, recorded at 2 mm distance antero-laterally from brachial umbo in 1 , 3, 1 valves respectively. Commissure crenulated along whole length. Brachial valves concave, with slightly convex umbonal region forming part of over- all concavity of adult. Sulcus of umbonal region rapidly broadening and shallowing, becoming poorly defined anteriorly, 1 -5-2-2 mm wide at 2 mm growth stage. Brachial valve interior with feebly developed notothyrial platform; cardinal process with apparently bilobed myophore and shaft. Brachiophores s.s. plate-like, as swellings to ventral edge of brachiophores s.l. Cardinalia about half as long as wide and a quarter as long as valve. Adductor field situated anteriorly from shaft, distinctly impressed into valve floor; follicular eminences and embayments well developed. No clearly defined dorsal ridge in brachial valve interior. Measurements of type material (in mm) Length Width Br 4145 4 0 6 1 Br 4146 3-4 5-4 Material. The following samples are assigned to this species: S35, S36, and, doubtfully, S37. Discussion. The taxonomic distance of D. anticipata to other species (Table 11) is in every case sufficient for it to be regarded as an independent species. Sample S37 is repre- sented by too few specimens for firm assignment, though it is possible that it may belong to D. transversa Wright 1968 which was recorded from Estonia (Wright 1968u, p. 302). This is also likely since S68 = D. transversa occurs in almost contemporaneous strata. Facies association. The Baltoscandian Ashgillian is characterized by local reef develop- ments (Mannil 1966). Reef bodies are absent in the outcrops and borings where the species has been found, but many Ordovician dicoelosiids from Baltoscandia are closely associated with reef or reef flank facies. Dicoelosia aff. osloensis Wright 1968 Plate 8, figs. 18-25 Description. Pedicle valve about three-quarters as long as wide, with mid-line length about two-thirds of maximum valve length. Valve thickness ranges from one-fifth to three-tenths maximum length, moderately convex in lateral profile. Lobes narrow, diverging between 57° and 75°, gently convex in lateral profile, separated by well- developed rounded sulcus, 1-6 mm wide at 2 mm growth stage. Hinge-line averages about half shell width; cardinal extremities obtuse, slightly flattened. 52 PALAEONTOLOGY, VOLUME 14 Ribbing on lobes well developed, with six angular costae (in one well-preserved specimen). Costellae appear to arise by bifurcation. Commissure crenulation developed only at lobe margins. One submedian rib appears to be on the sulcus floor. Brachial valve concave with small convex umbonal region. Sulcus not deep, with flattened floor. Brachial valve interior poorly preserved (PI. 8, fig. 25). Valve surface generally smooth, follicular eminences and embayments well developed. Measurements of figured material (in mm) Length Width Br 3402 4-3 50 Br 30/301 2-3 3-4 Br 30/302 2-2 3-4 Material. The samples forming this group are: S19, S38_4i, S46_49. Sample S44 is assigned to it doubtfully. Discussion. Only the two relatively young specimens of sample S19 can be used for numerical comparison. Table 8 demonstrates that there is a greater similarity between sample S19 and the stratigraphically and geographically closer samples of groups 20-23, 25, 18, 34, 17 than with other samples. Table 1 1 shows that D. indenta is the most closely related species, particularly in the similar degree of divergence of the lobes and the brachial concavity. The distance with D. osloensis is greater than expected. However, it is appropriate to associate S19 with D. osloensis , especially since it and the unmeasured specimens of the group lack Ordovician-type ribbing on the sulci. The differences with D. osloensis are too great, both visually and numerically in shell shape, for the samples to be considered as conspecific with D. osloensis. It is possible that D. aff. osloensis includes dicoelosiids intermediate between the Ordovician species, D. indenta or D. transversa, and D. osloensis. Facies association. D. aff. osloensis is widely distributed in the C/orinda Community (see Ziegler 1965) characterized by the brachiopods Clorinda undata (Sow.), Meifodia ovalis (Williams), Skenidioides lewisi (Dav.), etc. The sediments are mainly calcareous siltstones. EXPLANATION OF PLATE 8 All specimens X 6. Figs. 1-7. Dicoelosia anticipata Wright. 1-5, Ventral, dorsal, posterior, anterior, lateral views of complete shell, Br 4145, from S35. 6, 7, Interior and exterior of brachial valve, Br 4146, from S33. Figs. 8-17. Epitomyonia glypha Wright. 8-12, Ventral, dorsal, anterior, posterior, lateral views of complete shell, Br 3400, from S24. 13, Dorsal view of complete shell, Br 3401, from S24. 14, 15, Exterior and interior of brachial valve, Br 3418, from S24. 16, 17, Exterior and interior of brachial valve, Br 3419, from S24. Figs. 18-25. Dicoelosia aff. osloensis Wright. 18, Ventral view of complete shell, Br 3402, from S41. 19-21, Ventral, dorsal, lateral views of complete shell, Br 30/301, from S19. 22-24, Ventral, dorsal, lateral views of complete shell, Br 30/302, from S19. 25, Interior of brachial valve, Br 3403, from S38. Figs. 26-31. Dicoelosia osloensis Wright. 26-28, Ventral, anterior, lateral views of complete shell, Br 3406, from S25 . 29-31, Ventral, dorsal, lateral views of complete shell, Br 3404, from S34. Palaeontology, Vol. 14 PLATE 8 RUBEL, Dicoelosiid brachiopods M. RUBEL: TAXONOMY OF DICOELOSIID BRACHIOPODS 53 Dicoelosia osloensis Wright 1968 Plate 8, figs. 26-31 ; Plate 9, figs. 1-14 1967 Dicoelosia biloba (L.), Rybnikova, p. 174, pi. 15, figs. 1. 1968a Dicoelosia osloensis Wright, pp. 309-11, pi. 5, figs. 6-11, pi. 6, figs. 1, 7-10. 1968 Dicoelosia verneuiliana (Beecher); Amsden, pi. 8, figs. 1. Description of material from the East Baltic. Pedicle valve about nine-tenths as long as wide, with mid-line length averaging seven-tenths (three-quarters to five-eighths) of maximum valve length. Lobes broad, with slightly narrowing anterior part, strongly arched in lateral profile, diverging between 40° and 48° (average 45°). Lateral profile convex with valve thickness about one-third of valve length. Sulcus broad, with flattened floor, averaging about 1-1 mm wide at 2 mm growth stage. Interarea curved, apsacline, between one-sixth to one-seventh as long as valve. Hinge-fine three-fifths to three- sevenths as wide as maximum width, cardinal extremities obtuse, slightly rounded. Ribbing well developed on lobes, rib density 5-7 ribs per mm recorded at 2 mm distance antero-laterally from dorsal umbo in 2, 2, 1 valves respectively. Capillae rare. Fobbing weakly developed, not branching on the floor of sulci. Brachial valve always gently concave in lateral profile, sulcus well defined, deep, originating at apically convex umbonal region. Transverse profile of lobes strongly arched to flattened. Brachial valve interior (in one gerontic specimen) possesses extremely long lobes for the species with bilobed myophore of cardinal process and long shaft; ridges well- developed along lobes (PI. 2, fig. 14); follicular eminences and embayments strongly developed. Measurements of figured specimens (in mm) Length Width Br 30/303 7-2 7-4 Br 30/39 41 4-6 Br 3407 3-5 3-8 Br 3406 3-8 3-9 Br 3405 3-2 3-6 Br 3404 3-1 3-8 Material. The species includes samples S20_23, Sj.75 S18, S25, , S34, S53_55 and, doubtfully, one deformed pedicle valve S59. Discussion. The topotypes of D. osloensis are poorly preserved. Nevertheless, the distance between samples S20_23 and the topotypes is less than between all other samples (Table 1 1). Of course, the variability of S20_23i 25i 18 34 17 (i.e. 31-67) does not formally identify the sample with D. osloensis. However, firstly, the variability is reduced by the low number of specimens in the topotype sample, and, secondly, no other association is at present possible, excepting D. ‘ verneuiliana ’. In this respect the use of the name D. verneuiliana arises. Amsden (1968) figured the dicoelosiids (see synonymy) from the Upper Visby Marls, distinguishing them clearly from those selected for the types of D. verneuiliana by Wright (1968a, pi. 7). The latter 54 PALAEONTOLOGY, VOLUME 14 were collected in the last century and ‘little more can be said categorically about the type material except that it came from the Visby Marls of N.W. Gotland’ (op. cit., p. 313). My specimens, more like D. os/oensis than other species, seem to be very close to Amsden’s specimens (see Table 11), which are therefore considered synonymous with D. os/oensis. The dicoelosiids identified by me as D. verneuiliana from the lecto- types seem to be distributed in stratigraphically younger beds than the specimens 1 consider synonymous with D. os/oensis. A sample in our collection of D. verneuiliana sensu Wright from the Hogklint Group (PI. 9, figs. 15-19), unfortunately labelled only as ‘probably’ from these beds, and the other specimens figured by Amsden (1968, pi. 13, fig. 10a) certainly obtained from the Hogklint Group, must be assigned to D. verneuiliana. Nevertheless, it appears certain that D. os/oensis and D. verneuiliana both occur in the Upper Visby Marls, though geographically isolated. D. os/oensis, as at present understood, is undoubtedly very variable, though strati- graphically limited. Some specimens may be considered as extreme variants and close to D. verneuiliana , as for instance, the brachial valve (PI. 9, fig. 14). Facies association. It is likely that the variation in D. os/oensis is connected with the relatively large range of sediment types in which it is found. The facies map of Gailite et al. (1967, text-fig. 11) shows that D. os/oensis occurs in at least two facies. In terms of the brachiopod communities (Ziegler 1965) it occurs in the graptolitic facies (Kolka boring), the Clorinda Community (the Holdre and Ohesaare? borings), and, probably the Costistricklandia Community (Latikiila and KSinastu outcrops). Dicoe/osia sp. indet. Plate 9, figs. 20-25 Four samples, S29, S45, S42, S43, from the boundary beds between the Llandoverian and Wenlockian cannot be readily associated with any other samples. The lowest distance of S29 from other samples is 41-00 (see Table 8) showing its resemblance with the standard series, S26_28i 30-33. The latter and related samples show features typical of D. biloba, i.e. the concave lateral margins which are absent in all four samples. How- ever, these samples are characterized by a convex brachial valve in lateral profile, a feature quite absent in D. os/oensis and related samples. The assignment of D. sp. indet. EXPLANATION OF PLATE 9 All specimens X 6. Figs. 1-14. Dicoe/osia osloensis Wright. 1-5, Ventral, dorsal, lateral, anterior, posterior views of complete shell, Br 30/39, from S22. 6-10, Ventral, dorsal, lateral, anterior, posterior views of com- plete shell, Br 3405, from S34. 11-13, Ventral, dorsal, lateral views of complete shell, Br 3407, from S17. 14, Interior of brachial valve, Br 30/303, from S23. Figs. 15-19. Dicoe/osia vernuiliana (Beecher). Ventral, dorsal, anterior, posterior, lateral views of complete shell, Br 3408, from Hogklint Group?, Gotland. Figs. 20-25. Dicoelosia sp. indet. 20-24, Ventral, dorsal, anterior, posterior, lateral views of complete shell, Br 3410, from S29. 25, Interior of brachial valve, Br 3409, from S43. Figs. 26-31. Dicoelosia biloba (L.). 26-30, Ventral, dorsal, lateral, anterior, posterior views of com- plete shell, Br 30/304, from Su. 31, Interior of brachial valve, Br 3414, from S15. Fig. 32. Dicoelosia oklahomensis Amsden. Interior of brachial valve, Br 30/311, from S4. Palaeontology, Vol. 14 PLATE 9 RUBEL, Dicoelosiid brachiopods M. RUBEL: TAXONOMY OF DICOELOSIID BRACHIOPODS 55 to D. osloensis is subjectively likely, but the distances of S29 with topotypes of D. os/o- ensis and D. ‘ verneuilicina ’ are too great, 139, 99, and 123 respectively. Dicoelosia bilobci (Linnaeus 1758) Plate 9, figs. 26-31 ; Plate 10, figs. 1-22 1968a Dicoelosia biloba (Linnaeus); Wright, pp. 291-6, pi. 1, figs. 1-17; pi. 2, figs. 1-10. 1968 Dicoelosia biloba (Linnaeus); Amsden, pi. 8, figs. 3; pi. 13, fig. 12a. Three stratigraphically separate groups of samples are included in D. biloba. The Llandoverian samples constitute the earliest representatives of the species. Description of the Upper Llandoverian samples (PI. 9, figs. 26-30; PL 10, figs. 1-5). Pedicle valve about four-fifths as long as wide, with mid-line length about three-quarters of maximum valve length (from four-fifths to two-thirds); fairly convex in lateral pro- file, with valve thickness about two-sevenths of maximum length. Lobes fairly broad, sometimes narrow, divergence ranges between 40° and 59° (average 48°). Hinge-line a little less than half shell width, cardinal extremities obtuse with small flattened ears. Interarea curved, apsacline. Sulcus deep, originating at umbo, 1-0 mm wide at 2 mm growth stage, without clear radial ornament. Brachial valve about three-quarters as long as wide, flatly to moderate convex in lateral profiles; sulcus originating at umbo rounded, shallower than ventral one. Ornamentation on lobes of costae and branching costellae. Rib density of about 4 ribs per mm recorded at 2 mm distance antero-laterally from dorsal umbo in one specimen. Measurements of figured material (in mm) Length Width Br 30/304 3-4 4-5 Br 30/305 3-8 4-6 Br 30/306 2-3 2-7 Br 30/307 3-4 3-8 Material. Samples S8_13, S50_52 are included in this group. Discussion. The main features which distinguish the species from other Llandoverian dicoelosiids are the flattened to convex brachial valve in lateral profile, and, so far as the present collection is concerned, the concave lateral margins in the posterior region of the shell. Formal comparison suggests affinities with D. bilobella and D. oklahomensis (see Table 1 1). However, samples S8_13 are quite distinct from other Llandoverian samples (Table 8). Previously mentioned samples have been assigned to D. osloensis and samples S8_i3 may be considered intermediate between D. osloensis and D. oklahomensis. D. biloba occupies this position in Europe and the samples are assigned to it although the numerical comparison is not completely adequate. Facies association. The described material occurs in the Clorinda Community, charac- terized by Clorinda sp., Skenidioides lewisi (Dav.), Meifodia ovalis (Williams), Cyrtia exporrecta (L.), Leangel/a scissa (Salter), etc. 56 PALAEONTOLOGY, VOLUME 14 Description of the Wenlockian samples (PL 9, fig. 31; PI. 10, figs. 6-17). Pedicle valve about four-fifths as long as wide, with mid-line length about three-quarters of maxi- mum valve length. Lateral profile strongly convex, valve thickness about one-third of maximum length. Lobes broad, divergence ranging between 38° and 58° (average 50°). Hinge-line averaging a little more than half shell width, cardinal extremities obtuse with small flattened ears. Interarea curved, apsacline. Sulcus deep and narrow, origin- ating at umbo, 0-8 mm wide at 2 mm growth stage, without clearly defined ornament. Brachial valve about three-quarters as long as wide, flatly to moderately convex in lateral profile; cardinal extremities flattened, lobes posteriorly arched. Sulcus originating umbonally, slightly wider than ventral sulcus, without radial ornament. Ornamentation on lobes of angular costae and costellae. Measurements of figured material (in mm) Length Width Br 3411 3-6 3-9 Br 3412 3-5 4-8 Br 30/308 3-0 4-0 Br 3415 3-3 3-6 Br 3416 2-9 3-7 Br 3417 2-7 3-3 Material. Samples S26-2s, 30-33* Sis* S7, S16, S56, S61_63. Discussion. The Wenlockian D. biloba described differs only slightly from the Llando- verian material. The described material has the least distances with D. bilobella and D. oklahomensis (Table 1 1). It must be noted that the distances between the post-Llandoverian dicoelosiids such as D. biloba , D. bilobella, and even D. oklahomensis, is too low (Table 10). But the type material of these species, two specimens of each measured from their printed photographs, does not allow a certain decision. Nevertheless, the lowest distances of D. bilobella with the East Baltic material just described suggest that D. bilobella is a younger synonym of D. biloba. Maybe these Wenlockian representatives of two dicoelosiid stocks, North American and European, differ only in shell size, the former being smaller (see also Amsden 1968, p. 34). If so, then the name biloba should be preferred for the East Baltic specimens under discussion. EXPLANATION OF PLATE 10 All specimens X 6. Figs. 1-22. Dicoelosia biloba (L.). 1-5, Ventral, dorsal, anterior, lateral, posterior views of complete shell, Br 30/305, from Sn. 6-8, Ventral, dorsal, lateral views of complete shell, Br 3411, from S33. 9-11, Ventral, dorsal, lateral views of complete shell, Br 30/308, from S16. 12-14, Ventral, dorsal, lateral views of complete shell, Br 3412, from S31. 15-17, Ventral, dorsal, lateral views of complete shell, Br 3413, from S15. 18-22, Ventral, dorsal, anterior, lateral, posterior views of complete shell, Br 30/306, from S6. Figs. 23-40. Dicoelosia oklahomensis Amsden. 23-25, Ventral, dorsal, lateral views of complete shell, Br 30/312, from S14. 26-30, Ventral, dorsal, anterior, posterior, lateral views of complete shell, Br 30/313, from S5. 31-35, Ventral, dorsal, lateral, posterior, anterior, views of complete shell, Br 30/41, from S4. 36-39, Ventral, dorsal, posterior, lateral views of complete shell, Br 30/40, from Sj. 40, Interior of pedicle valve, Br 30/42, from Sj. Palaeontology, Vol. 14 PLATE 10 RUBEL, Dicoelosiid brachiopods M. RUBEL: TAXONOMY OF DICOELOSIID BRACHIOPODS 57 Facies association. D. biloba is found in calcareous siltstones. It is associated with the brachiopods Skenidioides lexvisi (Dav.), Cyrtia e.xporrecta (L.), Resserella sp., Atrypa sp. This would indicate that D. biloba belongs to the otf-shore association. Material of doubtful assignation (PL 10, figs. 18-22). Sample S6, a single shell, Br 30/309, from the Llandoverian beds of the Mezciems boring is quite distinct morphologically (Table 8) and geographically (text-fig. 1). Further material is required before a proper assignation can be made. Dicoelosia oklahomensis Amsden 1951 Plate 9, fig. 32; Plate 10, figs. 23-40 1951 Dicoelosia oklahomensis Amsden, p. 77, pi. 15, figs. 1-7. 1967 Dicoelosia oklahomensis Amsden; Rybnikova, p. 175, pi. 14, figs. 7, 8. 1968 Dicoelosia oklahomensis Amsden; Amsden, pi. 8, fig. 4. Description of material from East Baltic. Pedicle valve about five-sixths as long as wide, with mid-line length about three-quarters of maximum length; lateral profile strongly convex, valve thickness about two-sevenths of maximum length. Lobes fairly broad, divergence varying between 32° and 53° with an average of 46°. Hinge-line about half shell width, cardinal extremities obtuse with very small ears. Interarea curved, apsacline, relatively long. Sulcus deep and narrow, originating at umbo, only slightly widening, without radial ornament. Ribbing on lobes of low costae and costellae, capillae common. Brachial valve four-fifths as long as wide, fairly convex in lateral profile, sulcus originating at umbo, slightly wider than ventral one, without ribs. Interarea flat, ana- cline, shorter than ventral one. Lobes strongly arched in transverse profile. Pedicle valve interior with smooth surface, muscle field only slightly raised with low median ridge extending to anterior margin. Follicular eminences and embayments strongly developed. Brachial valve interior with small cardinalia, cardinal process with bilobed myophore and low shaft; brachiophore processes extend for one-third of valve length. Adductor field not clearly defined, follicular eminences and embayments strongly developed. Measurements of figured material (in mm) Length Width Br 30/40 2-6 3-3 Br 30/41 31 3-1 Br 30/42 2-7 c. 3-5 Br 30/311 c. 2-2 2-7 Br 30/312 2-5 3-5 Br 30/313 3-1 3-4 Material. The standard group, 14, and the poorly preserved samples S64_66. Discussion. The well preserved and abundant material may be readily identified by the degree of the brachial valve convexity with D. oklahomensis from the same level of the Upper Silurian of North America. 58 PALAEONTOLOGY, VOLUME 14 But the numerical comparison (Table 11) indicates that the closest species for S4_5i 14 is D. bilobella , although D. oklahomensis has nearly the same average similarity. The maximum and minimum distances of the S4_5> 14 specimens in relation to the type material of D. oklahomensis and D. bilobella are both lower in the case of D. okla- homensis. The comparison of the described material by separate samples (Table 12) shows the greater similarity of the stratigraphically younger samples, S4, S2, S14, with D. okla- homensis than with D. bilobella. Thus, only the stratigraphically younger part of the sequence, i.e. S4 — S2 — S14, may be identified by ‘shape’ taxonomy with D. okla- homensis. The relatively greater similarity of the older part, i.e. S3 — S4 — S5, with D. bilobella than D. oklahomensis is due to the main evolutionary trend of dicoelosiids. In spite of that the whole sequence is named as oklahomensis. table 12. Sample distances between the type specimens of D. oklahomensis (DO), D. bilo- bella (DB) and the Ludlovian samples of the collection. The samples are arranged in order by their minimal similar lines Si S2 S] 4 S3 s4 s5 DO DB 46-73 5007 28-50 48-50 39-25 47-75 55-20 40-00 66-00 76-25 46-00 69-25 Facies association. D. oklahomensis occurs in silty limestones characterized by Eospirifer radiatus (Sow.), Cyrtia sp., Dalejina hybrida (Sow.), Gypidula sp., Brachyprion sp., Atrypa sp. Genus epitomyonia Wright 1968 Epitomyonia glypha Wright 1968 Plate 8, figs. 8-17 19686 Epitomyonia glypha Wright, pp. 128-38, pi. 1, figs. 1-16. Material. Two complete shells and two brachial valves in sample S24. Description. Pedicle valve four-fifths as long as wide, mid-fine length four-fifths of maximum valve length. Lateral profile evenly convex, valve thickness about half maximum length. Lobes broad, diverging 60° in one specimen and 62° in the other; moderately convex with flattened crests in transverse profile. Hinge-line about four- fifths shell width in one specimen, and about three-fourths in the other. Cardinal extremities obtuse with small flattened ears. Sulcus shallow, well defined by prominent fascicle of branching ribs, 0-9 mm wide at 2 mm growth stage. Ornamentation on lobes and sulci of angular costae, intercalated and branching costellae, and rare capillae in intercostal spaces; on cardinal extremities ribs less distinct. Rib density measured at 2 mm antero-lateral to umbo along crest of brachial lobe, 5 and 4 costae or costellae per mm respectively. Ribbing at the edges of sulcus somewhat more elevated. Commissure crenulated though less so towards ears. M. RUBEL: TAXONOMY OF DICOELOSIID BRACHIQPODS 59 Brachial valve gently concave in lateral profile, typically slightly convex umbonally. Prominent edge of brachial sulcus corresponds to flattened crest of ventral lobe, 1 -9 and 2-3 mm wide at 2 mm growth stage respectively. Sulcus of umbonal region rapidly broadening and shallowing, sometimes divided longitudinally by one prominent rib into two parts. Brachial valve interior typical of species; notothyrial platform not greatly thickened, cardinal process with bilobed myophore and shaft anteriorly; sockets narrow, bounded medianly by low ridges of brachiophores s.l. from which hook-like brachiophores s.s. arise. Median septum rises anterior to shaft and extends almost to shell margin. Adduc- tor field not clearly impressed, anteriorly elevated above valve floor. Follicular emi- nences and embayments strongly developed, orthid-like. Measurements of figured material (in mm) Length Width Br 3400 4-2 5-1 Br 3401 2-4 3-5 Discussion. The species differs from other dicoelosiids in its peculiar internal structure. The closest species is D. anticipata. This lacks such structures, and also differs in having a more transverse outline and greater invagination of the shell. Facies association. Sample S24 comes from close to the local boundary between the Silurian and the Ordovician in approximately 0-5 mm of calcareous siltstones, similar lithologically to the immediately overlying beds. The latter contain abundant brachio- pods of the Stricklandia Community; the underlying Ordovician beds were formed under regressive conditions, when bioherms were common (Mannil 1966). REFERENCES amsden, T. w. 1951. Brachiopods of the Henryhouse Formation (Silurian) of Oklahoma. J. Paleont. 25, 69-97, pi. 15-20. 1968. Articulate brachiopods of the St. Clair Limestone (Silurian), Arkansas, and the Clarita Formation (Silurian), Oklahoma. Ibid. 42, Suppl. to no. 3, part II of II, Paleont. Soc., Mem. 1. frey, t. and vohandu, L. 1967. A new method for the establishing of classificational units. Eesti NSV Tead. Akad. Toim. 15, Bioloogiline seer., 565-76 [in Estonian with English summary], gailite, l. k., rybnjkova, M. v., and ulst, r. z. 1967. Stratigrafia, fauna i uslovia obrazovania siluriy- skikh porod srednei Pribaltiki. Riga [in Russian]. imbrie, j. 1956. Biometrical methods in the study of invertebrate fossils. Bull. Am. Mus. nat. Hist. 108, 217-52. kaesler, r. l. 1967. Numerical taxonomy in invertebrate paleontology. In Essays in paleontology & stratigraphy. R. C. Moore commem. vol., Dep. Geol. Univ. Kansas. Spec. Publ. 2, 63-79. mannil, R. M. 1966. Evolution of the Baltic basin during the Ordovician. Tallin [in Russian with English summary] . Ppik, a. a. 1967. The Mindyallan Fauna of North-Western Queensland. Bull. Bur. Miner. Resour. Geol. Geophys. Aust. 74. sokal, r. r. and sneath, p. h. 1963. Principles of numerical taxonomy. San Francisco, London. vohandu, l. 1964. Ob issledovanii mnogopriznakovykh biologicheskikh skem. In Primenenie mate- maticheskikh metodov v biologii, 3. Leningrad [in Russian]. 60 PALAEONTOLOGY, VOLUME 14 westbroek, p. 1967. Morphological observations with systematic implications on some Palaeozoic Rhynchonellida from Europe, with special emphasis on the Uncinulidae. Leid. geol. Meded. 41, 1-82, pi. 1-14. wright, a. d. 1968a. The brachiopod Dicoelosia biloba (Linnaeus) and related species. Ark. Zoo 1. 20, 261-319, pi. 1-7. 19686. A new genus of dicoelosiid brachiopod from Dalarna. Ark. Zool. 22, 127-38, pi. 1. ziegler, a. m. 1965. Silurian marine communities and their environmental significance. Nature, Lond. 207, 270-2. cocks, l. r. M., and mckerrow, w. s. 1968. The Llandovery transgression of the Welsh Borderland. Palaeontology, 11, 736-82. M. RUBEL Institute of Geology Academy of Sciences of the Estonian S.S.R. Revised typescript received 17 June 1970 Tallinn, U. S.S.R. MUSCULAR MECHANICS AND THE ONTOGENY OF SWIMMING IN SCALLOPS by STEPHEN JAY GOULD Abstract. Swimming ability declines, and may disappear, during the ontogeny of scallops that swim well as juveniles. The mechanics of swimming at increased sizes provides two reasons for decline during isometric growth: (1) Scallops are much denser than water; the gravitational force scales as the cube of the length (L3) while all lifting forces that could balance it scale at smaller powers of L. (2) The maximum velocity that a scallop can generate is independent of its size ; yet larger scallops must move faster than small ones in order to swim at all (minimum take-off velocity scales as L°’s). Actual scallops undergo allometric changes in ontogeny that partly offset this loss in swimming ability. I measured these changes in shell shape, muscle size, and muscle position in the growth of three Recent and one Miocene pectinid species. (1 ) The relative width of three free-living species increased; this improves the shell’s aspect ratio and augments the lift-drag ratio. Cemented Hinnites becomes relatively longer, an unsurprising exception to the general trend. (2) The area of the quick muscle insertion increases relative to the area of the right valve. (3) The quick muscle insertion moves from a dorsal to a more central position; in concert, these last two trends produce a relative increase in the closing moment that the adductor can exert in clapping the valves. (4) The quick muscle insertion moves from a posterior to a more central position; this lengthens the muscle by bringing it to a more convex portion of the shell, thus increasing its mass and power reserve. The fundamental feature of bivalve design, enclosure of a soft-bodied, headless animal between two valves of density 2-7 g/cm3, would seem to preclude the idea of a swimming clam; yet this adaptation has evolved several times (Stanley, in press). It is not only our intrinsic fascination for peculiarity that motivates the study of unusual adaptations in designs evolved for other purposes; for these adaptations are experiments that test the limits of form just as manufacturers expose their products to extreme conditions before marketing them for ordinary ones. One swimmer, one rock-borer, or one cementer can instruct us more in the properties of bivalve design than many new shallow burrowers. And it is therefore no accident that some of our best works on the functional morphology of fossil invertebrates deal with uncoiling snails (Abel 1929), coralliform brachiopods (Rudwick 1961), or recumbent crinoids (Moore 1962). I argued previously that modern systematics and its species concept have provided palaeontology with a science of diversity; yet, for lack of a corresponding central idea, we have no science of form (Gould 1970). I believe that this idea could be stated as a criterion for judging the relative efficiency of structures by the mechanical analysis of organic design as Rudwick proposes in his notion of the paradigm (1961, 1964, 1968). And just as our time-honoured method of studying the present elucidated the concept that built a science of diversity, so also do we need a palaeontology of the present to develop our functional morphology into a science of form. This study of scallop swimming is presented here not because one fossil species is included in the data, but because it is a palaeontological problem, based on the mechanics of hard parts and organs recorded therein, that requires a knowledge of behaviour and physiology for a solution that can be applied to the past. Although some solenids, solemyids, and cardiids swim occasionally (Stanley, in press), this peculiar bivalve adaptation is best developed within the Pectinacea. I (Palaeontology, Vol. 14, Part 1, 1971, pp. 61-94.] 62 PALAEONTOLOGY, VOLUME 14 consider here only scallops that swim with the commissure plane at 0° to approximately 45° to horizontal; Limidae swim with the commissure plane vertical. Basically, a scallop swims with the thrust provided by water jets. These are produced by rapid, repeated cycles of ligamental extension and adductor contraction. This produces the charac- teristic ‘clapping’ of the valves. (The movement of fluids by adductor contraction also powers the ‘hydraulic machine’ of burrowing bivalves [Trueman 1966, p. 525] and the cleansing reactions that Yonge [1936] regards as precursors to swimming.) In addition, the scallop must avoid sinking by achieving hydraulic lift, by directing its motion partially upward to compensate for sinking between claps or by directing a separate water jet downwards as Buddenbrock (1911) believed and Stanley (in press) denies. In this work I am concerned almost entirely with the most neglected and most per- vasive aspect of mechanical problems — the effect of size or scale (reviews in Bonner 1952 and 1968, Cock 1966, Gould 1966, and Thompson 1942). The performance of virtually any machine will alter if it maintains its shape as size increases. The most familiar reason for this involves the different scaling of areas (L2) and volumes (L3). But other effects may be more important. Kinetic energy, for some problems, scales as L5; some amusing consequences are developed by Went (1968). From a mechanical point of view, an outstanding feature of organisms is that they must deal with such different balances of forces at various stages of their life-cycle. Thus, when compared with a man-made device, an organism not only must often use inferior materials (hence no wheeled organisms or really heavy fliers), but must also adapt to the varying require- ments of very different sizes. The literature is full of unassembled, undigested, and unassimilated data on the influence of size upon form and habits. In the absence of a theory to collate these observations, they stand as scattered bits of pure, and therefore unenlightening, informa- tion. One set of similar bits, in fact, inspired this project. Over and over again, it has been recorded that the large scallops of any swimming species swim rarely, poorly, or not at all (Yonge 1936 in general; Bayliss et al. 1930 for Pecten maximus; Verrill 1897 and Waller 1969 for Argopecten ir radians; Verrill 1897 and Caddy 1968 for Placopecten magellanicus; Fairbridge 1953 for Motorola meridionalis; Olsen 1955 for Equichlamys ); no-one has ever asked why. For such a change in habits, there are two possible types of explanation: 1. Large scallops do not swim because they need not. Large, heavy valves might pro- vide the protection from predators that active escape furnished for small scallops. 2. Large scallops do not swim because they cannot. (In either case, of course, the new and more sluggish habit of large scallops entails no loss of adaptation. In fact, large scallops use the same quick adductor contractions that had previously powered their swimming to ‘recess’ into self-formed depressions for protection; Baird 1958, p. 68; Waller 1969, pp. 16-17.) Whatever our a priori preference, we should, as a method of procedure, begin with (2) as a working hypothesis and seek a reason why large scallops might be unable to swim. Continuing failure would lead us to suspect (1), though not prove the point, while an initial assumption of (1) closes the matter prematurely, for the demonstration of no need says nothing of the original impetus for such adaptations as recessing and STEPHEN JAY GOULD: SWIMMING IN SCALLOPS 63 shell thickening. Since scallops are still with us, they have obviously accommodated themselves to any problems imposed by size. The problems of increased size are met by allometric growth (Gould 1966), i.e. by changes in shape that allow an organism to avoid the unfavourable aspects of geometric similarity in scaling. The empirical part of this study, therefore, is an attempt to define allometric patterns in important structures that can be detected in fossils, i.e. basic shell shape and muscular size and position. It is extraordinary how little work has been done on the basic description of allometry in scallops, not to mention its adaptive significance. Of the adductor musculature, Waller (1969, p. 22) writes: ‘Positional and dimensional changes of the adductor during growth have been poorly described. . . . The meaning of these changes in terms of function is unknown.’ Merrill (1961) records the movement of adductors in P/acopecten magellanicus from a posterior dorsal to a more central position. Waller (1969) found a similar shift in most members of the Argopecten gibbus stock and also noted a tendency for the muscles to increase in relative size. No one has given explicit consideration to the ontogeny of differences in relative size and movement between quick and slow portions of the adductor musculature. The only information here is Waller’s set of drawings for Argopecten comparilis from the Miocene of Florida (1969, p. 22). Ontogenetic allometry of musculature has been reported by Sandberg (1964) and Benson (1967) for ostracods and by Spjeldnaes (1957) for brachiopods, again without much consideration for adaptive significances. It is perhaps even more surprising that so little functional analysis has been offered for the obvious and easily quantified changes of basic shell form with growth. Thus, increase in relative shell width has been noted a number of times, but only recently did Stanley (in press) relate this to an improvement in aspect ratio. Aspect ratio is the basic parameter of shape in aerodynamics (see p. 87); all major texts in engineering give it prominent consideration in discussions on the motion of lifting bodies. The argument of this paper will therefore proceed as follows : 1. To show that there are physical reasons why large scallops would have greater difficulty in swimming than small ones; 2. To demonstrate that the major allometries of shell and muscle can all be inter- preted as providing some aid in meeting these difficulties. We often think that the adaptive significance of size-required allometry (Gould 1966, p. 588) lies in maintaining such properties as the surface to volume ratio. Often, however, when size places ever more stringent requirements upon given functions (increased wing loading for flight in birds, for example), large animals will possess designs of greater efficiency than those needed in smaller models. Rashevsky writes (1960, p. 273): ‘For larger animals, like birds, the profile of the wing must be made more perfect an aerodynamic profile than it needs to be for insects.’ And Bainbridge (1958) has noted, in fishes, the same improvements in muscles and body shape that characterize the growth of scallops. MATERIALS AND METHODS From collections of the Departments of Invertebrate Palaeontology and Molluscs at the Museum of Comparative Zoology, Harvard University, I selected five samples of four species that cover the range of pectinid swimming ability : 64 PALAEONTOLOGY, VOLUME 14 1. Placopecten magellanicus, Recent from Penobscot Bay, Maine. M.C.Z. No. 71965 (Molluscs); 30 right valves ranging from 0-3 to 131-4 g in weight. P. magellanicus is the common sea scallop of the western Atlantic and is considered to be an excellent swimmer (Stanley, in press, Caddy 1968). 2. P. magellanicus, Recent from 10 miles SE. of Block Island, Rhode Island. M.C.Z. No. 225815 (Molluscs); 19 right valves ranging from 0-4 to 123-8 g in weight. 3. Amusium balloti, Recent from Queensland. M.C.Z. Nos. 213682 and 213828 (Molluscs); 13 right valves ranging from 2-4 to 22-5 g in weight. I know of no actual observations, but every major feature of its design (pp. 79-81) marks Amusium as the most accomplished bivalve swimmer. 4. Hinnites multirugosus, Recent from San Diego Bay, California. M.C.Z. Nos. 70320, 87050 and 115251 (Molluscs); 8 right valves ranging from 0-4 to 176-5 g in weight. Young are byssally attached, swimming if dislodged ; permanent attachment by cementa- tion at dorso-ventral diameter of 2-2-4-2 cm (Yonge 1951). 5. Chlamys ( Lyropecten ) jeffersonius, Miocene, Yorktown Formation, Virginia. M.C.Z. No. 17498 (Invertebrate Palaeontology); 19 right valves ranging from 0-1 to 466-6 g in weight. I have no information for this common fossil, but species of Chlamys are either byssally attached throughout life or free living during part, or all, of growth. The adductor musculature of pectinids (and most clams) consists of two portions performing two functions. The more central, striate quick muscle (text-fig. 1) contracts rapidly but cannot hold the valves together for long; it produces the rapid, cleansing contractions of many clams and the ‘clapping’ of valves for swimming in pectinids. The posterior, smooth, slow muscle is not involved in swimming; it contracts slowly but holds the valves tightly shut for long periods with little expenditure of energy. The more common designation, ‘catch muscle’, refers to a theory of its action that is still under debate — to von Uexkull’s notion of a ‘molecular ratchet’ (Hoyle 1964, p. 333) that, once set, allows the muscle to remain in a state of tension without consuming energy. I prefer to speak of ‘slow muscle’, a descriptive term of undisputed application. Hill (1950, p. 227), moreover, has shown that the smooth adductor must be slow in order to maintain a state of contraction for long periods, for speed of shortening and economy in maintaining force are opposing properties of muscle. In this observation we are also provided with an explanation for the large size of quick v. slow muscle in swimming clams ; to provide power for continual, rapid clapping of the valves, the uneconomical quick muscle must be large. The impressions of these muscles are distinct on right valves, but fused on left valves; since the study of swimming requires their distinction, only right valves were used. The following measurements were made (text-fig. 1): 1. Basic shell dimensions: (a) Weight in grams. (b) Area of the right valve. The valve outlines were traced and measured with a compensating polar planimeter. Variation in valve convexity presents difficulties that will be considered later. (c) Antero-posterior width of shell (IJ of text-fig. 1). (d) Dorso-ventral length of shell (KL of text-fig. 1). STEPHEN JAY GOULD: SWIMMING IN SCALLOPS 65 2. Size of muscles : ( e ) Area of slow muscle insertion projected to plane of commissure. (/) Area of quick muscle insertion projected to plane of commissure. The scar peripheries were outlined in black and traced on to thin paper held tautly in the plane of commissure. Valve outlines were traced on the same sheet to produce drawings like text-fig. 1. Marceau (1936) made similar measures by drawing on glass placed upon the plane of commissure. A A' K text-fig. 1. Measures used in this study (see text for explanation). 3. Position of the muscles: (g and h) Position of quick and slow muscles in dorso-ventral axis. The shortest distances between the hinge line and the muscle measured parallel to KL (AB and A' B') and between the most ventral extension of the muscles and the tangent to point L (CD and CD') were measured. The ratios AB/CD and A'B'/C'D' define muscle posi- tions with respect to the dorso-ventral axis. (i and j) Position of quick and slow muscles in antero-posterior axis. By analogy with the method used in (g) and (h), the ratios EF/GH and E'F'/G'EE define the positions of quick and slow muscle, respectively, in the antero-posterior axis. SIZE AND SWIMMING IN SCALLOPS: A THEORETICAL ANALYSIS In this section, I present two reasons why large scallops should have more difficulty in swimming than small ones of the same shape. In presupposing geometric similarity (constant shape at all sizes) in this discussion, I purposely misrepresent actual scallops in order to detect the problems they alleviate by allometric growth. F C 7895 66 PALAEONTOLOGY, VOLUME 14 Forces on a swimming scallop A swimming scallop is subject to four major forces, two that impede its motion and two that aid it (text-fig. 2). 1. A drag force resists its horizontal motion. Drag is a compound force of three major components: frictional drag arising from surface stresses, form drag from normal pressures (these designated, collectively, as profile drag) and induced drag generated when lifting vortices lose connection with the shell at its lateral tips where their energy degrades as heat (Weis-Fogh 1961; Goldstein 1965). L ? G text-fig. 2. The forces acting on a swimming scallop. Lift (L) counteracts gravity (G), while thrust (T) overcomes drag (£>). Placopecten magellanicus; note the more convex upper valve, enabling the shell to function as a lifting hydrofoil. 2. A thrust force to overcome drag and propel the shell is generated by the expulsion of water jets at the anterior and posterior auricles. 3. The gravitational force, if not counteracted, limits forward motion by causing the scallop to sink to the bottom. Other pelagic molluscs avoid this problem with a fascinat- ing array of buoyancy mechanisms: gelatinous, low density tissues of pteropods and heteropods; floating (on mucus-coated air bubbles in Ianthina , on mucous floats in Peringia ulva ); low-density coelomic fluid in cranchid squids; and gas filled buoyancy chambers in many cephalopods (Denton 1964). But all scallops are much denser than the medium in which they swim (specific gravity of the shell is near 2-7, while the tissues are near sea water in density). For this analysis, it is imperative that we recognize the proper analogy: the swimming of scallops is comparable to flight, not to the normal STEPHEN JAY GOULD: SWIMMING IN SCALLOPS 67 swimming of neutrally buoyant pelagic animals. ‘How the fish or dolphin swims, and how the bird flies, are up to a certain point analogous problems. . . . But the bird is much heavier than the air, and the fish has much the same density as the water, so that the problem of keeping afloat or aloft is negligible in the one, and all-important in the other’ (D’Arcy Thompson 1942, p. 43). Hence, ‘swimming and flying have much in common, by flying involves an additional complication in that lift to overcome the gravitational pail must be produced as well as thrust to overcome the drag of the body moving through the fluid’ (Weis-Fogh and Jensen 1956, p. 418, italics in original). The rapid sinking of non-clapping scallops has often been recorded (Gutsell 1931, Moore and Marshall 1967, p. 77). 4. A lift force must be generated to balance the gravitational force and prevent sinking. Some scallops are designed as lifting aerofoils; their upper (left) valve exceeds the right in convexity and lift is achieved in the usual way, in accordance with Bernoulli’s Theorem. But most scallops are either equiconvex or have more convex lower (right) valves. This is apparently related to the common tendency for unattached scallops to recess in the substrate into self-excavated depressions. Greater right-valve convexity permits deeper recession and provides greater protection; 1 assume, with Waller (1969, p. 17), that it is disadvantageous for the plane of commissure to be far below the surface of the substrate. Verrill (1897) and Baird (1958) noted that this right convexity should impart a negative lift. If this seems to be a poor design for swimming, we are probably faced with a problem of conflicting demands upon form that result in compromises optimal for neither function. In fact, in a second solution to the problem of lift, such scallops swim with their planes of commissure inclined as much as 45° from the hori- zontal (Jackson 1890, p. 339; Gutsell 1931, p. 597; Stanley, in press). Although they fall between claps, the upward force provided by expelling water downwards as well as backwards is sufficient to prevent sinking. Some pteropods maintain themselves in the nekton with a similar propulsive rise and passive fall mechanism (Morton 1954; Kornicker 1959). Jeffries and Minton (1965) assumed a similar mode of locomotion in their model experiments on swimming in the Jurassic bivalve Bositra buchi. They concluded that Bositra could have maintained its swimming only if it were provided with a long fringe of tentacles as in modern limids. This conclusion points to a short- coming of the present work. In discussing the structures that generate the swimming jets, I have considered only the shell and musculature and have ignored the pallial curtain (inner mantle lobe) which is not recorded in fossils. This curtain, or velum, is certainly important. It forms a ‘valve’ (engineer’s, not conchologist’s) to prevent ventral expulsion of water when the valves close and may even create a water jet without adductor contraction by its withdrawal from beyond the ventral margin towards the hinge (Waller, personal communication). Stanley (in press) reports that many right- convex scallops are not long-distance swimmers but move primarily to escape from predators and unfavourable micro-environments. Some scallops may possess a third lifting mechanism if Buddenbrock (1911) is correct in claiming that, in addition to the posterior jets, water is expelled downwards at the anterior margin; the observation has not been repeated, and Stanley (in press) doubts that it is of much importance. To achieve equilibrium in swimming, therefore, a scallop must provide thrust to balance drag and lift to overcome gravity. 68 PALAEONTOLOGY, VOLUME 14 The sealing of forces on a swimming scallop How do these forces change as a scallop grows? I should begin with a disclaimer. The dimensional approach, although easy to apply in its simplest form, is rarely ade- quate for all complexities (see criticism of Weis-Fogh and Jensen 1956, p. 436, for insect flight). A scallop is not an experimental sphere, cylinder, or even an aerofoil (though P. magellanicus is close to one). It performs such odd tasks as swimming right into the turbulent eddies of its own clapping. We know neither the regimes of flow over its complex surface nor the potential effect of pressure differentials produced by its anterior ingestion of water. We have no information on its behaviour in relation to the primary way that aerofoils increase lift, that is by increasing the angle of attack (Weis-Fogh and Jensen 1956, p. 417; Jacobs 1963, p. 348; Thom and Swart 1940). Stanley (in press) has claimed that P. magellanicus swims with its plane of commissure horizontal (i.e. with an angle of attack = 0°); but the minutest changes in this property can increase lift enormously. Jacobs (1963, p. 348) reports a three-fold rise in lift coefficient for an increase of 0-2° in the angle of attack of his experimental aerofoil. 1 . Drag. The drag on a body is given by the equation where D is the drag, p the density of the medium, v the velocity, A a characteristic area and Cd the drag coefficient. The density of sea water is approximately constant. I shall argue on p. 72 that large scallops swim at the same speed as small ones. The area A might be measured as total surface area or frontal area (projected area in the direction of flow); in any event, it scales as L2 in our hypothetical series of scallops that increase in size without altering their shape. The drag coefficient, Cd, depends on the shape of the body and on Reynolds number (Alexander 1968, p. 215). Our shape is invariant, but Reynolds number, the dimensionless quantity that represents the ratio of inertial to viscous forces and specifies the flow regime past objects, is given by where Re is Reynolds number, v is velocity, / is length of the body in the direction of flow, and y is the kinematic viscosity of the medium (see Alexander 1968, pp. 209-78 on the interpretation and importance of Reynolds number). Since this discussion is based on scallops designed as lifting aerofoils, we shall use the Western Atlantic sea scallop Placopecten magellanicus as a model. Caddy (1968) reported that P. magellanicus swims at speeds ‘in excess of 67 cm/sec’ ; individuals greater than 10 cm in length rarely swim at all. Setting maximum velocity as 75 cm/s (constant throughout the size range — - see p. 72), entering the kinematic viscosity of water as 0-01 and taking the size range of swimming as 1 cm (freedom from juvenile byssal attachment) to 1 0 cm (adults cease to swim), the range of Reynolds number for this species is, from (2), 7500 to 75 000; or, being somewhat more generous, approximately 103 to 105. Now, a great number of experiments on bodies of various shapes (Alexander 1968, fig. 90, p. 216; Zeigler and Gill 1959, fig. on p. 5a; Goldstein 1965; Jacobs 1963) show that this is just the range of Re in which the drag coefficient tends to be invariant : ‘The drag coefficient is nearly constant for a body of given shape, moving in a given direction, at Reynolds numbers between about 103 and 105 (Alexander 1968, p. 217). Hence, in our range of Re and shell D = 1/2 p v2ACd 0) Re = vl/y (2) STEPHEN JAY GOULD: SWIMMING IN SCALLOPS 69 size, A is the only right-hand term of (1) that will change in a regular manner with increase in size. The drag force should therefore scale as L2. 2. Thrust. To balance drag and keep larger scallops swimming at equilibrium, thrust will have to scale as L 2 as well. But, let us ask a different question, for the problem is more one of endurance. How many times can a scallop clap before fatiguing; for how long can it supply a thrust force scaling as the square of length? In other words, what is the effect of size upon power output? Power is work (force x distance or cross- sectional area of muscle x length through which it contracts) per unit time. As an initial expectation we might assume that power should increase as the mass of musculature, i.e. as L3. But power can increase only so fast as oxygen is supplied to the muscles and the heat generated by their action is dissipated ; since both these processes are mediated by surfaces, power should scale as L 2 (Smith 1968, pp. 8-11, Hill 1950, pp. 218-19, Thompson 1942, p. 32). The argument, despite impressive support and supporters, is not without its weaknesses. Thompson (1942) points out that, for short spurts before too much heat accumulates or an oxygen debt is incurred, power should scale as L3. (We must then ask whether the swimming periods of some scallops are short and in this range, or short because muscles fatigue rapidly when clapping several times per second.) Due to some unusual metabolic properties insect wing muscle may never encounter a problem with oxygen supply. ‘Oxidative recovery processes have been speeded up to such rates that, on the average, they are completed within the duration of a single con- traction cycle. . . . All major enzyme systems must operate at least ten to thirty times faster than in human muscle’ (Weis-Fogh 1961, p. 291). There is no evidence for similar mechanisms in birds or bats, not to mention scallops (Weis-Fogh 1961, p. 292). Some fishes can increase the slope of their log oxygen consumption v. log weight curve in response to changing salinity and swimming speed (Farmer and Beamish 1969), but the slope does not reach 1 (scaling as L3). The only evidence I have found for oxygen con- sumption v. size in scallops (Montuori 1913) is presented as Table 1. Since oxygen consumption ratios are similar to weight2/3 ratios and smaller than straight weight ratios, scaling as L2 is implied. (The data, ironically, are from an author who attempted to disprove such scaling by counting the scallop data as exceptional.) In any event, the data are for resting metabolism and need have little to do with swimming. table 1. Oxygen consumption of resting metabolism in Pecten jacobeus and P. varius at two sizes (from Montuori, 1913) Absolute oxygen Ratio of Weight consumption in consumptions for Ratio of Ratio of Species (in g ) 2 h (in crm) two weights weights weights 2f3 P. jacobeus 620 1-026 4-48 7-75 3-92 800 0-229 P. varius 5-0 0-183 1-29 2-50 1-84 20 0-142 In summary, dimensional considerations lead to the conclusion that muscular power should scale as L2. Scaling at higher exponents of L may occur for short bursts or when special adaptations are present. It is unlikely that power could scale at exponents of L as high as 3 ; I shall assume in future discussion that power scales as L2. 70 PALAEONTOLOGY, VOLUME 14 3. Gravity. The gravitational force scales as weight, or L3. 4. Lift. The formula for lift is like that for drag Li = 1/2 p v2 AQ (3) where p and v (density of the medium and velocity) remain constant with size increase, the area A scales as L 2 and Cj (the lift coefficient) again depends on shape and Reynolds number but not in the same way as it does for drag. Here we encounter a difficulty not met in considering drag, for there is very little information on variation of Cj with Re in a scallop’s range, though there is no want of knowledge for aeroplanes. This lack of data has been decried by Weis-Fogh (1956a, p. 547) and Vogel (1967, p. 431). Gold- stein (1965, pp. 444-5) reports on an aerofoil at Re ranging from 5xl04 to 3xl05. C, rises with increase in Rc; the rise may be abrupt but it is always very small (maximum increase from 1-2 to 1-6 compared with very rapid increases of Q for tiny changes in the attack angle, p. 68). For various aerofoil shapes and turbulence in the medium, Millikan (1934) found virtually no relation between C, and Re at Re slightly above the scallop range. Thom and Swart (1940) studied the behaviour of an aerofoil at very low Re. C, is very high at Re = 1, but it declines rapidly, by Re = 10 it has stabilized and remains almost constant well into the scallop range, to the limits of their data at Re = 104. These patchy observations have led Jacobs (1963, p. 330) and Von Karman and Burgers (1963, p. 4) to state that aerofoil size may usually be neglected in calculating C,. ‘In most cases, Cj and Cd can be treated as approximately independent of the velocity and (for geometrically similar airfoils) of the dimensions of the airfoil, though actually they depend on the Reynolds number connected with the flow around it’ (Von Karman and Burgers 1963, p. 4). Hence, for geometrically similar aerofoils at a constant orienta- tion, lift will scale as L2. Swimming and size: the first argument There lies, in the previous section, an obvious problem for large scallops — the gravi- tational force that impedes their motion increases faster than any force that could balance gravity. There are some potential solutions to this dilemma. Most animals that swim or fly through a medium less dense than themselves manage to generate enough lift to balance their increasing weight. How is this done? We just argued that lift scales as L2, weight as L3. The ratio of lifting surface/body weight must decline with growth; this is the classic problem of increased ‘wing-loading’ in birds (Meunier 1959a, b; Holst and Kuchemann 1942; Gray 1968). The answer is that lift scales as L2 only under the restrictive conditions of constant shape and orientation; animals possess an impressive repertory of devices for increasing lift at greater rates. Sharks lack a swim bladder and many are denser than sea water (Bone and Roberts 1969); they have two lifting devices, one on each side of their centre of gravity; the heterocercal tail (Grove and Newell 1936; Affleck 1950) and pectoral fins shaped as aerofoils (Harris 1936; Alexander 1965). To obtain more lift they can increase the amplitude of tail-beat and raise the angle of attack of their pectoral fins. Insects regulate lift by changing the angle of wing attack (Nachtigall 1967), and by appropriate and complex wing twisting at various points of the stroke (Weis-Fogh 19566, Bennett 1970). STEPHEN JAY GOULD: SWIMMING IN SCALLOPS 71 Iii noting that desert locusts maintain a constant lift even when the incidence angle of their body is forcibly changed from 0 to 15°, Weis-Fogh (19566, p. 574) proposed ‘a lift-sensitive receptor system which controls the motor impulses’. Birds use such subtle mechanisms as a slotted wing (Brown 1963; Alexander 1968, p. 239) to increase the angle of attack at which stalling occurs; even so, large birds cannot hover as hummingbirds do, while gliding and thermal soaring on warm updrafts become very important to large albatrosses and buzzards (Alexander 1968, pp. 240-50; Pennycuick 1960). Which of these devices are available to scallops? Scallops have no flexibility and cannot bend their lifting surface. Their medium does not provide sufficient turbulence for gliding or riding on upwelling currents. I even doubt that they can use, to any great extent, the most common device for increasing lift: raising the angle of attack. For whereas sharks can incline their pectorals, birds and insects their wings, and still move forward horizontally, a scallop’s lifting surface is his entire outer covering. If this is inclined, the whole body must move in that direction and sacrifice part of its horizontal component (as do, indeed, the poorer swimmers among scallops that are not designed as aerofoils). Another way to increase lift is to increase velocity (equation 3). Moreover, increased velocity would also benefit non-lifting scallops that swim upward and sink between claps; for even though larger animals would sink more quickly than smaller ones, they might cover an equal horizontal distance in this shorter time by moving faster. I could find no data on sinking speed in scallops and therefore performed the following rough experiment. Double valves of Placopecten magellanicus and Amusium ballotti were selected to represent the available size range; each pair was held together by modelling clay equal to the weight of the valves. These were dropped, ten times each, in swimming position, through 35 cm of sea water. (Caddy 1968, reports that the largest, swimming P. magellanicus reach a height of 40 cm from the bottom.) The density of soft tissues probably does not differ much from that of the sea water that occupied the body space in this experiment; the shell, on the other hand, has a specific gravity near 2-7. Tamura (1929) reports an average tissue weight/total weight ratio of in Patinopecten yessoensis. I plotted the mean time for a 35-cm fall against the square root of length times height (text-fig. 3). I thought that the falling time might scale as L~l since the ratio of drag forces that resist sinking to gravitational forces that encourage it is L2/ZA The resistance to sinking provided by the plate-like valves is really quite impressive when you realize that it takes only 2 seconds for a quartz sphere ( p = 2-65) only IT 3 mm in diameter to fall 35 cm in fresh water (Zeigler and Gill 1959). In fact, the falling time decreases very rapidly at first and slowly thereafter because the drag on small, unstable scallops is sufficiently strong to cause them to rock back and forth while sinking, whereas large shells drop straight down. This is reflected in the larger standard deviations (actual standard deviations, not standardized coefficients of variation) for small scallops (vertical lines of text-fig. 3). Attractive as it seems as a mechanism for generating lift, increased velocity is not often attained by larger animals. Most authors agree that the maximum velocity of geometrically similar animals is largely independent of their size (Hill 1950, on cetaceans, Smith 1968, Thompson 1942). Some of the standard reasons are applicable to scallops and new ones can be developed to relate scallop swimming to this common argument. text-fig. 3. Time to fall 35 cm in sea water v. size in Amusium ballotti (upper curve) and Placopecten magellanicus (lower curve). Passive drop experiment on double valves. Each point is the mean time (10 trials) required for a single specimen. The vertical line through each point is the standard deviation of these 10 trials. 1. The scallop as a hydraulic pump. Let us assume that the forward velocity of a scallop is in constant proportion to the backward velocity of expelled water and demon- strate that this backward velocity is independent of size. The mass of water expelled should equal pAV where p is density and AV the change in scallop volume during a closing stroke. Then pAV = pvTA (4) where v is the velocity of the existing water, T the stroke time and A the cross-sectional area of the gap through which water is expelled. Now T is proportional to the con- traction time of the quick muscle. Since the contraction time of muscle is directly proportional to its length, T should scale as L. The slower speed of larger pumps and levers is recorded in the reduced pulse rate of large mammals (Smith 1968, Gould 1966), tail beat frequency of large fishes (Gray 1968) and wing-beat frequency of large insects (Chapman 1969, Reed et al. 1942, Weis-Fogh and Jensen 1956) and birds (Hill 1950, Rashevsky 1960). Therefore pAV V = U PTA IMJ (5) and velocity is independent of size. STEPHEN JAY GOULD: SWIMMING IN SCALLOPS 73 2. Scallop power (argument adapted from Smith 1968). The power exerted by a scallop is equal to (force x velocity). The force must balance the drag force which, from (1), and remembering that Cd is constant for Re in a scallop’s range, scales as L2v2; the power required is therefore LVxv or L2v3. Since the power available is L 2 (p. 69) L2 oc LV and v3oc L2 L2 = 1. (6) (7) Velocity, again, is independent of size. I conclude, therefore, that scallops probably cannot generate enough lift to balance increasing weight as they grow. Swimming and size: the second argument A second, and stronger, argument depends on our conclusion that maximum velocity is independent of size. D’Arcy Thompson (1942, p. 46) enunciated a ‘principle of neces- sary speed’ and explained it as follows (p. 41) (and here we must remember that the appropriate analogy for scallop swimming is flight, not the swimming of teleosts) : ‘In running, walking, or swimming, we consider the speed which an animal can attain. . . . But in flight there is a certain necessary speed — a speed (relative to air) which the bird must attain in order to maintain himself aloft, and which must increase as its size increases.’ The idea that minimum take-off velocity must scale as some positive power of L is an old one. Thompson (1942, p. 48) reminds us that it formed the basis for one of Borelli’s propositions in De motu animaliwn (1685): Est impossible ut homines propriis viribus artificiose volare possint. Propriis viribus (by their own strength) is the key. Large birds can glide (as did the pioneers of human aviation before adding motored power), scallops cannot. Gray (1968) presents a dimensional argument that is incorrect as a generalization, but valid within a scallop’s range. Since the lift force must balance weight in order to keep an object aloft, from (3) 1/2 p v3AC, = mg (8) and (9) 2_ mg] { clP a r where vm is the minimal velocity needed for take-off. Gray then errs in assuming that 2/ Ci is constant. Since Cj depends on Reynolds number, it is not independent of size; however, at Reynolds number in a scallop’s range, is approximately constant (p. 70). Therefore v,„ = k Moz /^ocL05 (10) and a scallop four times the length of another must swim twice as fast to get off the bottom. Since the maximum velocity of a scallop is independent of size (p. 72), if small scallops swim at anywhere near their maximum speed, large scallops will not be able to swim at all. In fact, large Placopecten magellanicus do execute quick contractions, but do not take off (Caddy 1968, p. 2131). Theoretical arguments aside, Thompson’s principle of necessary speed is validated by the swimming and flight behaviour of many animals that are heavier than their 74 PALAEONTOLOGY, VOLUME 14 enclosing medium. Large birds have difficulty rising from the ground and ‘must fly quickly or not at all’ (Thompson 1942, pp. 45-6); insects and hummingbirds can hover in almost stationary flight. The three largest elasmobranchs swim very slowly, in apparent contradiction to our principle; yet two of these have oily livers that provide neutral buoyancy, while the third, Mobula the ray, has an enormous lifting surface (Bone and Roberts 1969). Small bats and birds can take off directly from their perch; ‘condors and the larger fruit bats take to the heights so that they may plunge fully into open air’ (Breder 1930, p. 115). Adult flying fish (Cypselurinae) ‘taxi’ before a flight, accelerating on the speedboat principle by driving the caudal fin through water while the body encounters less drag in moving through the rarer medium of air. Yet young flying fish do not taxi before their flights (Hubbs 1933, p. 603). Hubbs attributed this difference in behaviour to recapitulation in the evolution of flight (primitive flying fish, he believed, merely leap out of water with no preliminary manoeuvre). It seems quite clear, however, that behavioural differences in the flight of young and old cypselurids are size- required adaptations for commensurate efficiency in motion, not the signposts of an antiquated rule of phylogeny. Young horseshoe crabs ‘swim briskly up and down, skimming about on their backs’ (Packard 1871, p. 500). Yet Clarke and Ruedemann (1912, p. 73) describe the almost comic performance of a large limulid which, in trying to take off, climbed a rock, fell into the water and landed on its tail spine. There are, in summary, two major reasons why scallops that do not change their shape during growth will experience continually greater difficulties in swimming as they increase in size. (I note that size increase causes a scallop to cease swimming not once, but twice during its ontogeny. We have just documented the loss at large sizes. But the prodissoconch swims by the beating of velar cilia (Gutsell 1931) and the insuf- ficiency of ciliary locomotion at large sizes is a classic example of surface/volume problems (Gould 1966, p. 638), the cilia number increases as the external surface; the weight they must support as volume). 1 . The gravitational force scales as ZA All forces that could balance it, in principle, scale at smaller powers of L. 2. Maximum velocity is independent of size; yet larger scallops must move faster than small ones in order to swim at all. ALLOMETRY AND SWIMMING IN SCALLOPS: AN EMPIRICAL ANALYSIS If swimming becomes continually more difficult as scallops increase in size, we can expect that growth will be accompanied by allometric changes, selected to alleviate these difficulties. (Since large scallops do not swim, solutions are not complete; but any favourable allometry will slow down the rate at which swimming ability is lost and pro- long the range of swimming to larger sizes. Scallops may retain the ability to swim until they are large enough for defence against predators that could only be evaded by flight at smaller sizes. The more massive valves and greater absolute muscle force of large scallops will afford protection [see Hancock 1965, on the relation of muscle size to star- fish predation in Mytilus]). On pp. 63-5 I discussed the species that were studied and defined the measures that were made. Table 2 presents some summary statistics calculated from these data. The STEPHEN JAY GOULD: SWIMMING IN SCALLOPS 75 a o C ON 'T do C/3 II O *-p~ .E S) ■2 15 ■£ ^ ‘2 T3 O v. * ?. ©* > s ^ O co o3 > *-• C -C c .SP -H >H g 55 5 n 2 7 3 ** OO CO p g S £ -a | § 8 o UO O SO ^ o E ° c c £ o C '£ 00 c3 03 13 J- H S^t c 2 tp ? V • a Q > g.lj* qS H ^ 3? S ■< a c §, 3 5 to w o ^-> to Co jfc • <3 OZ ^ OO 73 O) S U 53 fS2 in O t"- ^ 't O r- 6 6 6 oc r- m Os — os ’t O VO 6 6 6 — in m M in h Tf O so 6 6 6 oo oo it* so oo in id* r-~ no on id* on "t m o\ «n on on n m ^ •^t ‘ co 6 6 6 ON > bo 5 e W NU CT) d, c If x. c3 2 'c/5 HH c3 ^ Qj o S CQ <3 w .5/ cn 5 76 PALAEONTOLOGY, VOLUME 14 first eight columns include regression parameters (least squares y on x), three lines for each column (y-intercept, slope, and correlation coefficient in that order). For this linear model, , , /11X y = ax+b (11) allometry is measured by the y-intercept; y increases faster than x if the y-intercept is negative, vice versa if positive. The ratio of increments y/x per unit x is constant during growth, but since these increments are being added to an initial shape of different pro- portions, total shape changes during growth (Gould 1968, p. 84; Waller 1969, pp. 23-5). The single exception is column 3, where quick muscle area is plotted against shell weight. Here the increments cannot be constant, since y scales near L1 2 and x near L3. Here we use a power function log y = a (log x) -f- log b (12) and we are interested in the slope. Allometry is measured by change in the ratio of incre- ments, and we look for variation from the ideal slope of 2/3 to detect departure from geometric similarity. We have still another concern when ratios, rather than raw measures, are plotted against a linear dimension. Here (as in columns 5-8) our test for allometry is any sig- nificant correlation coefficient or slope 0. (Ratios are dimensionless parameters of shape and must remain constant during growth if geometric similarity is to be main- tained. Any significant correlation of a ratio with a linear measure indicates allometry.) Allometric trends and interspecific variation I shall first describe the allometric changes and then present interpretations for each as improvements in swimming design that partly offset the detrimental effects of increasing size. With the initial descriptions, I shall also discuss interspecific differences and their relation to varying modes of life. (Interspecific differences are shown in Table 2 in columns 9-14; entries are predicted values for given variables at common size-standards for large scallops still well within the swimming range of P/acopecten magellanicus — columns 9-12 at right valve area = 60 cm2; columns 13-14 at length = 8-9 cm.) 1. Basic dimensions. We see, from y-intercept values of column 4, that width/length ratios increase in all species except the cemented Hinnites multirugosus. Increasing rela- tive width, I shall argue on p. 87, provides advantages in swimming. It has been noted before in free-living scallops. It was the most consistent of Waller’s ‘size-correlated morphological trends’ (1969, p. 24); relative width increased during the ontogeny of all 56 samples of various species of the Argopecten gibbus stock. Yonge (1951, p. 409) recognized the correlation of this trend with mode of life when he stated, of the family Pectinidae, that ‘only in those that lose all attachment ... is the anteroposterior diameter the greater’. Hinnites multirugosus begins its post-larval life conventionally as a byssally attached juvenile. It is, at this stage, capable of swimming movements when dislodged. But at a dorso-ventral diameter of 2-2-4-2 cm it cements permanently to the substrate (Yonge 1951). Thereafter it undergoes progressive elongation rather than widening, an unsurprising exception for a scallop in this oyster-like role. Pedum spondyloideum. STEPHEN JAY GOULD: SWIMMING IN SCALLOPS 77 another sedentary pectinid, also becomes more elongated as it grows (Yonge 19676). Text-fig. 4 plots the width/length ratio against size in all five samples. 2. Size of the quick muscle. In column 1 (Table 2), we see that the area of quick muscle insertion increases faster than the area of the entire valve during ontogeny in all samples. The relationship, as shown in text-fig. 5, seems to convey the odd impression that non-swimming Hinnites has a larger quick muscle at any standardized stage of LENGTH text-fig. 4. Width/length ratio of the right valve plotted against length (in inches). Based on predicted values from the width v. length regressions of Table 2. Letters as follows: J - Chlamys jeffersonius', P = Placopecten magellanicus; A = Amusium ballot ti; H = Hin- nites multirugosus. Relative width increases during the ontogeny of all species but the cemented Hinnites. Increased relative width aids swimming by augmenting the shell’s aspect ratio. growth than the accomplished swimmer Placopecten magellanicus. However, this results only from the use of area as a size standard. If we plot quick muscle area against shell weight (text-fig. 6 and Table 2, column 3), this anomaly is resolved. Amusium , our best swimmer, bears the greatest quick muscle area per unit weight at any weight. But now the two Placopecten samples are not only closer together, but also lie near Amusium ’s line, while non-swimming Hinnites and fossil Chlamys jeffersonius are further removed to a region of high weight per unit muscle area. Since Hinnites cements by the right valve, its quick muscle, in executing cleansing contractions, need only move the lighter left valve. A massive right valve therefore imposes no mechanical penalties and offers undoubted aid for stability and protection. Hinnites lies close to Amusium in text-fig. 5b because it has the most convex right valve among our species; this produces a mis- leading high value for quick muscle area in relation to valve area projected to the plane of commissure. The line for Chlamys jeffersonius in text-fig. 6 is peculiar in one respect. It passes from an area occupied by good swimmers early in its ontogeny, finally to cross the Hinnites line at large sizes. Although this unusual scallop lacks close living relatives and has not yielded palaeoecological data to reveal its mode of life, I feel confident that the ontogeny of its swimming behaviour can be deciphered from this mechanical analysis. Young C. jeffersonius are very light, yet the shell thickens during ontogeny at a rate approached, to my knowledge, by no living scallop. Despite its coarse ribbing I suspect that the 78 PALAEONTOLOGY VOLUME 14 young could swim, not only because their valves were so light, but especially because the width/length ratio increases with growth (pp. 76 and 87). Yet the remarkable shell thickening that places this species second only to the abalone as a favoured object for text-fig. 5. Muscle areas v. total area of the right valve; based on calculated slopes and intercept of Table 2 (in cm2). A: slow muscle area. B: quick muscle area. Letters as in text-fig. 4. shell ash-trays surely precludes swimming at large sizes ; C. jeffersonius could generate neither the velocity to raise its adult shell nor the lift to keep it aloft. The adults must have rested free on the bottom, stable by the sheer weight of their valves and protected both by this weight and by the strength of their massive slow muscle (see next para- graph). STEPHEN JAY GOULD: SWIMMING IN SCALLOPS 79 300 100 30 10 3. Size of the slow muscle. Text-fig. 5 clearly distinguishes the good swimmers from Himiites and C. jeffersonius by the small size of their slow muscle. Since Placopecten and Amusium respond to predators by flight (photographs in Rees 1957), they need not maintain the slow muscle strength that sedentary scallops require. (Kim 1969, found that starfish could open Patinopecten yes- soensis more quickly than they opened a variety of cemented and slow-moving forms. J He claims that Patinopecten is, nonetheless, H comparatively difficult prey because valve movements tend to drive the starfish ofif. This is surely not the major reason. The scallop was firmly attached to a wood plate in this experiment; Kim’s kymograph merely re- corded the quick muscle contractions of the scallop’s escape reaction.) The slow muscle of C. jeffersonius is parti- cularly massive (text-fig. 7), even on the small specimens that were, if my previous conten- tion is correct, capable of swimming. This poses no problem, for there are two ways for an adult to produce a structure that need be relatively large only late in ontogeny. The structure will either grow with marked positive allometry (which may impose a heavy metabolic load and markedly increase variation at large sizes), or it can be rela- tively large to begin with and grow at normal rates. German writers on allometry refer to this second mode as Vorbereitungswachstum (or preparatory growth) and cite such obvious examples as the fully developed wings of nestling birds (Kramer 1959). In such cases, the functional significance of features at small sizes can only be determined by study- ing the mechanics and behaviour of adults. Amusium' s very small slow muscle (text-fig. 7) may provide an example of material compensation in Rensch’s sense (1960, pp. 179-91), and offers further testimony to this animal’s presumed abilities as a swimmer. No one, it seems, has reported on the actual behaviour of Amusium; yet the anatomical and structural evidence is strong, despite the fact that Amusium is not an aerofoil because its lower valve is the more convex. (i) The remarkably small convexity of the valves, reduced, as Yonge (1936, p. 78) states, to a minimum raises the fineness ratio chord (= width) /maximum thickness to its highest value among scallops. In hydrodynamics the fineness ratio is second in importance only to the aspect ratio (p. 87) as a measure of efficiency in aerofoils; the drag coefficient rises markedly as relative thickness of an aerofoil increases. H- X o LD 3 3 QUICK 10 20 MUSCLE AREA text-fig. 6. Weight (in g) v. quick muscle area (cm2) on logarithmic coordinates. Letters as in text-fig. 4. 80 PALAEONTOLOGY, VOLUME 14 (ii) The extreme lightness of the valves reduces the gravitational force, thereby reduc- ing the speed of sinking (text-fig. 3) and specifying a minimum velocity for take-off smaller than that of any other scallop at any comparable size. Most scallops increase the relative thickness of their valves as they grow, Amusium does not. It is, in fact, the only one of our four species in which the log quick area v. log weight regression main- tains a slope greater than the predicted 2/3 for isometry (k = 0-820). Amusium possesses an extraordinary adaptation for sufficient strength in the presence of such lightness; it has interna 1 ribs that allow the outer surface to remain smooth. The emphasis on light- ness extends to shell micro-architecture: ‘Where these [internal] ribs are covered by text-fig. 7. Valve outlines, quick and slow muscle scar traces of actual specimens. Left: Amusium ballotti. Right: Chlamys jeffersonius. Specimens in correct relative proportions to each other. Actual width of A. ballotti = 10 cm. the crossed-lamellar inner layer, there is a reciprocal thickness variation, so that the relief of the central part of the shell is greatly reduced’ (Taylor, Kennedy, and Hall 1969, p. 94). (iii) I have already alluded to the uncommon smoothness of the valves. This surely reduces turbulence, as does the absence of a byssal notch and very small size of the auricles. There is another intrinsic reason why Amusium needs to be smooth. The higher the fineness ratio of an object, the greater the percentage contribution of skin-friction drag to its total drag (Goldstein 1965, p. 425). By being smooth Amusium minimizes the most important component of its drag. (iv) Considerations of flow provide other evidences of good swimming design. The point of maximum convexity is more anterior than in most other scallops. The gradual posterior taper from this point helps prevent separation of the flow. In addition, the postero-lateral edges of the upper (left) valve are turned upwards. With an axis of maximal convexity running down the centre of the valve, this upbowing at the edges produces two lateral channels that should direct the flow and prevent separation. (v) The large quick muscle and small slow muscle have already been discussed. (vi) Waller (1969, p. 21) mentions that while the slow muscle is inserted normal to the valves, the quick muscle is quite oblique. This lengthens the quick muscle and increases its capacity for performing work (cross-sectional area x length). STEPHEN JAY GOULD: SWIMMING IN SCALLOPS 81 (vii) Yonge (19676, p. 315) reports the ‘circumstantial evidence’ of Pelseneer who showed that the right posterior pedal retractor is large in byssally attached scallops and small in unattached forms. It is absent in Amusium. 4. Movement of the quick muscle ; movement in the dorso-ventral axis. Text-figure 8 a and^column 5 of Table 2 show that the quick muscle moves to a progressively more ventral position during the ontogeny of all samples. (I shall resolve, on p. 89, the SHELL LENGTH TEXT-FIG. 8 ( a ) LLi o * CL O §3 OC LU I c n O CL i o on LU 1 — z < SHELL WIDTH TEXT-FIG. 8 ( b ) text-fig. 8. (a) Dorso-ventral position of the quick muscle (AB/CD of text-fig. 1) v. shell length (in). Relative motion is dorsal to central in all species, (b) Antero-posterior position of the quick muscle (EF/GH of text-fig. 1) v. shell width (in). Relative motion is posterior to central in all species. apparent anomaly that this motion is greatest in cemented Hinnites.) This motion has been noted before, by Waller (1969) and, particularly, by Merrill (1961, pp. 12-13) who claims that, in Placopecten magellanicus, the adductor moves to a more ventral position until the shell reaches a length of about 50 mm. Thereafter, the position of the adductor is said to be stable. Thus, for Merrill, there are two distinct phases in ontogeny, one of motion and one of stability. I should like to point out that this appearance is illusory and that both supposed phases are the consequences of a single process. During allometric growth on the linear model (equation 11), the rate of change in y/x must decrease as size increases. This occurs because such allometry consists of adding C 7895 g 82 PALAEONTOLOGY, VOLUME 14 increments of unvarying y/x to an initial shape of different proportions. As the initial shape becomes a progressively smaller part of the whole, y/x of the whole approaches the constant incremental y/x and the rate of change in shape diminishes. Now, text-fig. 9 shows that the linear model applies in a quite precise and unvarying fashion throughout growth. The regression line of text-fig. 9 was computed simply by connecting points for my largest scallop and that for the 5-mm shell figured by Merrill 1961, p. 14 (and Q O text-fig. 9. Distance from ventral border of quick muscle to ventral border of the shell v. shell length in Placopecten magellanicus from Penobscot Bay (in mm). far smaller than any I could measure). My measured points are well distributed with small variance about this line for CD v. shell length (text-fig. 1) y = 0-478*+ 1 -28 (13) and the positive y intercept indicates that the muscle approaches the ventral border as growth proceeds. The diminishing rate of change in y/x that this equation yields is plotted directly as text-fig. 10. Text-fig. 11 then shows, for theoretical scallops conform- ing to this equation, how the appearance of stability at large sizes arises (the rate of change between 60 and 120 mm is quite slow). Finally, the plot for our ratio measure of dorso-ventral position (AB/CD of text-fig. 1) v. size (text-fig. 12) shows that, while the rate of movement does indeed diminish beyond Merrill’s 50 mm, its direction never changes. Of 8 scallops that equal or exceed 0-6 for this measure, 5 are larger than 125 mm in length; (there are only 6 shells in the > 125 mm category). Given the wide variation in this measure, the qualitative impression of two growth phases is almost unavoidable. Movement in the antero-posterior axis: column 7 of Table 2 and text-fig. 8 b show that, in all samples, the quick muscle moves from a posterior to a more central position during growth. I have separated the dorso-ventral from this antero-posterior com- ponent because I believe that the adaptive significances of the two are different STEPHEN JAY GOULD: SWIMMING IN SCALLOPS 83 (pp. 87-91). Of course, they represent a single vector in growth — a single motion from a dorso-posterior to more ventral and central position. 5. Movement of the slow muscle: columns 6 and 8 of Table 2 and text-fig. 13. It would seem, at first glance, that movement of the slow muscle follows no clear pattern. Its dorso-ventral motion, for example, is dorsad in two samples, ventrad in three (with SHELL LENGTH text-fig. 10. y/x of text-fig. 9 v. shell length (in mm). Calculated from the regression fine of text-fig. 9 to show the originally rapid and subsequently slow allometric change of this ratio. text-fig. 11. Theoretical scallops drawn to same scale. Shell length (in mm) given in figures above each drawing. The sizes and positions of the quick muscle correspond to calculations of text-fig. 9 and show that allometric changes are very rapid at small sizes and very slow later in growth. the two Placopecten samples showing opposite tendencies). However, when the slopes of these regressions are ranked and compared with those for quick muscle motion (Table 3) we see that, in each case, there is correspondence between the two sets. Apart from the higher slope for slow muscle than for quick muscle in dorso-ventral motion of Amusium and the insignificant reversal in magnitude between slow muscle slopes of C. jeffersonius and Penobscot Bay P. magellanicus for antero-posterior motion, the ranking of slow muscle slopes is the same as for quick muscle. However, for each motion, the average slow muscle slope is less than the average for quick muscles. Thus, for slow muscles, the ranking includes zero and there is reversal of direction, whereas all quick muscle slopes are in the same direction for each motion. Thus, the slow muscle tends to move less than the quick muscle, but at least part of its motion is correlated with that of the quick muscle. We have here, I suspect, a case of mechanical correlation 84 PALAEONTOLOGY, VOLUME 14 in which slow muscle is pulled by the motion of its neighbour (the two, as diners can testify, do form a single, edible entity) or by the extension of this bordering growth field. If the goal of ‘morphological integration’ is to separate and explain the various, often opposing, determinants of form (Olson and Miller 1959; Gould and Garwood 1969), then we acquire useful information in identifying a component of slow muscle position that is correlated with, and perhaps controlled by, quick muscle motion. Q O CQ < - 7 z O co -6 O Q_ LU .4 > o CO CC O Q .3 12 3 4 5 SHELL LENGTH text-fig. 12. Dorso-ventral position of quick muscle (AB/CD of text-fig. 1) v. shell length (in inches) for Placopecten magellanicus from Penobscot Bay. Relative ventral movement continues throughout growth. The net effect of these motions is that the slow muscle seems to slip around the quick muscle from a ventral-central to a more dorsal-posterior position during growth (text- fig. 14). Actually, this effect is produced primarily by ventral-central, quick muscle motion relative to a more stable slow muscle. Hypotheses for allometric trends I can imagine three major categories of explanation for these allometric tendencies: 1. A developmental hypothesis that does not posit specific, functional explanations for observed changes of shape; the single muscle of pectinids is, morphologically, the posterior adductor (Jackson 1890, Marceau 1936, p. 941). As Jackson (1890, p. 342) suspected and Gutsell (1931) demonstrated, larval pectinids have two adductors, situated near the dorsal hinge axis as in orthodox dimyarians. Hence, enlargement of the one muscle that remains and its motion from an original dorsal-posterior position to a more ventral and central one need represent no more than one part of an onto- genetic reorganization that converts a dimyarian clam to one in which the body is more DORSO-VENTRAL POSITION- SLOW MUSCLE STEPHEN JAY GOULD: SWIMMING IN SCALLOPS 85 SHELL LENGTH SHELL LENGTH TEXT-FIG. 13 (d) TEXT-FIG. 13 (6) text-fig. 13. ( a ) Dorso-ventral position of the slow muscle (A'B'/C'D' of text-fig. 1) v. shell length (in). Letters as in text-fig. 4. ( b ) Antero-posterior position of the slow muscle (E'F'/G'H' of text-fig. 1) v. shell width (in). Lines in these and similar figures calculated from the regressions of Table 2. table 3. Correlation of slow and quick muscle motions (figures are slopes of regression lines) Case 1 . Dorso-ventral motion D-V motion of D-V motion of quick muscle v. slow muscle v. Species shell length shell length Hinnites multirugosus 0145 0-106 Amusium ballotti 0055 0-063 Placopecten magellanicus 0040 0-013 (Penobscot Bay) Chlamys jejfersonius 0-018 - 0-021 P. magellanicus (Block Is.) 0017 - 0-051 Case 2. Antero-posterior motion A-P motion of A-P motion of quick muscle v. slow muscle v. Species shell width shell width Hinnites multirugosus - 0-157 - 0-070 Chlamys jeffersonius - 0-115 - 0-003 Placopecten magellanicus - 0-062 - 0-015 (Penobscot Bay) Amusium ballotti - 0-041 0-043 P. magellanicus (Block Is.) - 0-008 0-059 86 PALAEONTOLOGY, VOLUME 14 symmetrically distributed about a more central muscle. Here there would be no need to maintain a specific, mechanical explanation for an isolated component of muscular allometry. 2. A functional hypothesis that does not explain allometric trends as adaptations to the problems of increased size. Here, we begin by admitting that the postero-dorsal placement of the larval muscle does not suit the changing functional requirements of later ontogeny. But we do not frame explanations in terms of size and its mechanical consequences, i.e. the adaptation would be advantageous at any size; the delay in its appearance simply relates to the time required for a gradual reorganization of larval text-fig. 14. Valve outlines and muscle scar impressions for three actual specimens of Placopecten magellanicus drawn to the same scale. Actual shell lengths (left to right) are 145, 71, and 25 mm. Quick muscle scars of the two smaller shells are superposed upon the largest shell to indicate the muscle’s change of position. Allometry of shell shape is also well displayed by this series. proportions. A more central quick muscle, for example, would provide a better distri- bution of stresses on the hinge and periphery. A postero-dorsal position, near the posterior auricle, might impede the circulation of water on this side and lead to eccen- tricity of swimming as more water was expelled from the antero-lateral margin. For slow muscle a central position offers protection from predators that concentrate their attacks ‘at the periphery of the valves where the shell is thinnest’ (Waller 1969, p. 19). A very dorsal muscle leaves the whole ventral margin poorly defended as the force needed to open the valves will be some inverse function of the ratio C'D'/A'B' (text-fig. 1). 3. A functional hypothesis that relates allometric trends to size increase by explaining them as the mechanical requirements imposed by size itself. In this case, the gradual progression of a trend through ontogeny is not seen as a sign of constant improvement, but as a graded response to a mechanical problem that becomes increasingly more severe as the scallop grows. I have no doubt that all these hypotheses contribute to the complex explanation of allometry in scallops. By discussing only the third in the following section, I am not suggesting that others do not apply, but only that each allometric trend does provide advantages for swimming that larger scallops require. STEPHEN JAY GOULD: SWIMMING IN SCALLOPS 87 Allometric trends and size increase Previous discussion showed that increased size will make swimming more difficult for scallops. This discussion contained one important departure from reality. It assumed an invariant shape with growth, whereas allometry is not only common in scallops, but is also the usual way in which animals overcome the mechanical problems of increased size. 1. Basic dimensions of the shell. I mentioned that lift and drag coefficients depended both on Reynolds number and on shape. For hydrodynamic considerations, the most important measure of shape is the ‘aspect ratio’, the quotient of the span of an aerofoil (maximum length perpendicular to direction of motion) divided by its chord (parallel to motion — Dryden, Murnaghan, and Bateman 1956, p. 75). This corresponds to the width/ length ratio of scallops, a measure that increases during the ontogeny of all species, with the obvious exception of cemented Hinnites. As aspect ratio improves, the lift/drag ratio increases (Weis-Fogh 1961, p. 284) and flight becomes easier. ‘Lifting power not only depends on area but has a linear factor besides, such that a long narrow wing is more stable and effective both for speedy and for soaring flight than a short and broad one of equal area’ (Thompson 1942, p. 961). D’Arcy Thompson then (p. 964) shows an ideal bird, constructed to make the leading edges of the wings as long as possible and to produce a continuous curve with no sharp corners. The result (text-fig. 15) is a very fine picture of the ventral margin of a scallop. Stanley (in press) has related the greater relative width of free-living v. byssate scallops to aspect ratio. 2 and 3. Size of the quick muscle and its dorso-ventral movement. Lest the coupling of these two trends seem peculiar, consider the mechanics of motion in scallops. At first thought we might seek an explanation for decreased swimming at increased sizes in the idea that muscular strength increases as L2 and weight as ZA Galileo’s argument for the relatively thick legs of large terrestrial animals would then apply, by analogy, to the swimming of scallops. But muscular strength alone is not the appropriate measure; a scallop claps its valves by exerting a force to counteract the opening moment of the ligament (Trueman 1953). This force is measured not by the strength, but by the moment exerted by the quick muscle in rotating the valves towards each other about the hinge. This moment is measured by the muscular force (its cross-sectional area) times its distance from the point of rotation (linear distance from this point, approximately the centre of the muscle insertion, to the hinge). For an isometric size series, this moment will scale as L3 and offset the increasing weight. (It is only for this reason that most clams can exhibit so little muscular allometry and still maintain their strength to move, burrow, and bore at large sizes — see Thomas, in press, on Glycymeris .) Both text-fig. 15. D’Arcy Thompson’s idealized bird. Note the resem- blance of the leading edge of the wing to a scallop’s ventral margin (its leading edge). PALAEONTOLOGY, VOLUME 14 the size of the quick muscle and its position in the dorso-ventral axis determine its moment, hence their combination in this discussion. In an elegant series of experiments, Trueman (1953) actually measured the closing moment of the ligament in eviscerated scallops with intact ligaments. This measure, then, is not the actual moment exerted by the adductors to close the valves, but rather the minimal moment needed to close them against the opposing force exerted by the ligament. Trueman found (1953, p. 455) that this closing moment scales as L3. Now, if allometric growth causes the muscles to increase in relative size and move to a more ventral position, then the actual moment exerted by the quick muscle will scale at a power of L greater than 3. If this improved moment allowed the valves to adduct with continually greater relative effect during growth, then large scallops might generate higher velocities than smaller ones and partly overcome both difficulties discussed on p. 74. I measured the actual moment of each specimen as the product of quick cross-sectional area times the distance from the centre of this muscle to the hinge. I plotted these values against shell weight and obtained the following regressions: Placopecten magellanicus, Penobscot Bay y = 0-590X1 02 (14) where, in all formulae, y is moment and x is weight. Placopecten magellanicus, Block Island y = 0-336X1 19 (15) Amusium ballot ti y = 0-8 18a1 17 (16) Hinnites multirugosus y = 0T13.V1 22 (17) Chlamys jejfersonius y = 0-655x°'89 (18) Amusium continues to stand out as the best swimmer. Its rate of increase for moment is essentially the same as that for two other samples, but its y-intercept is so much greater than the others that its total moment far exceeds that of all other samples at any comparable size. (For these cases, the value x = 1 g [at which the y-intercept is calculated] lies within the range of measured data, and the actual value of the y-intercept may be meaningful as a measure of initial tendency. This is not usually the case; see White and Gould 1965.) Hinnites , on the other hand, has a slope equal to that of two swimming samples, but its y-intercept is low and its total moment smaller than that of all swimmers at sizes in our measured range. The two Placopecten samples behave differently: the Penobscot Bay sample does not improve its relative moment with growth, while the Block Island sample does. Shell weight at comparable valve areas is a good deal lower in the Penobscot Bay sample than in the Block Island sample (48-6 g v. 64T g at the large area of 120 cm2). This weight differential might control the generally smaller muscle sizes (both quick and slow) in Penobscot Bay scallops (Table 2, columns 9 and 10) and their smaller rate of relative increase in moment. Perhaps scallops can exert a direct influence upon muscle sizes and positions via developmental feedback (Warburton 1955) from shell weight. C. jejfersonius, as expected, is the only sample that exhibits a relative decrease in moment with growth. The enormous thickening of STEPHEN JAY GOULD: SWIMMING IN SCALLOPS 89 the valves in growth causes weight to increase at a rate that cannot possibly be met by changes in the size and position of muscles. This provides yet another piece of evidence for concluding that C.jeffersonius lost its ability to swim when the valves thickened (p. 78). If we isolate the two components of moment, we encounter some anomalies that need resolution. If we consider muscle size relative to weight, then relative increase appears only in our best swimmer, Amusium (Table 2, column 3). Relative muscle size is virtually constant for the two samples of Placopecten and decreases for Hinnites and, especially, for C. jeffersonius. Since cemented Hinnites must move only its left valve and since the rate at which left valve weight increases is slower than that for right valves, the slope of log quick area v. log left valve weight might well exceed 2/3. But why should a non-swimmer show relative increase in muscle size? And does this not invalidate a claim that such relative increase therefore provides benefits to swimmers? The answer to both questions is no, because sedentary and cemented scallops also depend upon quick muscle contractions, though for functions other than swimming. Yonge (1936, p. 95) has called sediment ‘the supreme danger to which all sedentary animals with ciliary feeding mechanisms are exposed’. He assumes that large quick muscles arose first as adaptations in sedentary forms for rapid and powerful cleansing contractions that would expel pseudofaeces and free the mantle cavity of sediment. In mud-dwelling Glossus, quick muscle is twice as large as slow muscle. But Chama lives in clear, intertidal or shallow water; it must stay tightly closed during exposure to air and has a larger slow than quick muscle (Yonge 1967a). Quick muscle is very well developed in Placuna (life on muddy bottoms) and Anomia (close application to rocks and consequent exposure to sediment, Yonge, 1936). Kauffman (1969, p. 178) attributes the large quick muscle of Ostrea to ‘the ability of the animal to clean the mantle cavity and shell of sediment by rapid and forceful closure of the valves’. Yonge (1953, p. 460) says the same of Hinnites'. ‘The danger of sediment accumulating in the cup-shaped lower valve is countered by the great development of the striated section of the adductor.’ Moreover, Caddy (1968, p. 2131) reports that large, non-swimming P. magellanicus use quick muscle contractions to recess into the sub- strate by blowing sand away from the margins of the shell. In fact, Yonge (1967h, p. 320) views these adaptations for quick contraction in sedentary forms as necessary precursors to the evolution of swimming: ‘The capacity for swimming (i.e. movement with the free edges of the valves foremost) is due largely to prior possession of adapta- tions concerned with effective cleansing of the mantle cavity, notably enlargement of the quick muscle and ejection of water (with pseudofaeces) dorsally at either end of the hinge.’ It might be more appropriate, however, to consider muscle size relative to valve area since quick contractions supply thrust to overcome drag that increases as area rather than as weight (p. 68). Quick muscle area increases faster than valve area in all samples (Table 2, column 1). In Hinnites, this probably reflects only the increasing valve convexity, but it may record an advantage in swimming for other species. For the second component of dorso-ventral motion, all samples show ventral dis- placement (Table 2, column 5, and text-fig. 8). A serious potential difficulty exists in the observation that this displacement is greatest in rate and magnitude for cemented Hinnites. This presents no problem for two reasons. First, we just maintained that Hinnites also depends upon quick contraction, but for cleansing rather than for swimming. 90 PALAEONTOLOGY, VOLUME 14 But secondly, and more important, this high rate is an artifact. In Hinnites and Pedum, sedentary scallops that live in crevices, Yonge (1951, 19676) has demonstrated that the hinge line itself moves far ventral during ontogeny. In 1951 he viewed this motion as a response to the constraints of rock surfaces in crevices : If the hinge originally lay in the narrow part of a widening crevice, the valves of larger animals would be unable to open unless the hinge migrated to a wider area. Now (19676, p. 321), since he has noted this ventral migration in cemented bivalves that do not inhabit crevices, Yonge views it as ‘an inevitable consequence of cementation; only in this way can the animal increase in width dorsally during growth’. In my measures, AB (text-fig. 1) for Hinnites is the distance from the original dorsal border to the quick muscle. It is spuriously high since it includes the entire component of hinge migration as well as the actual muscle migration. Finally, we might ask why the muscle does not move further towards the ventral border, since the moment would increase with each increment. Trueman (1967, pp. 473-4) has probably provided the answer in stating: ‘If the adductor muscles were situated further from the hinge axis the mechanical advantage gained would greatly reduce the figure of muscular strength needed for adduction, but proximity to the axis ensures rapid adduction of the valves. The closer the adductor is to the hinge axis, the less the muscle will have to contract to close the shell and, provided that it shortens at a constant rate, the more rapid will adduction be.’ Another reason for this limitation in ventral motion has been provided by Thayer (in press). Thayer demonstrates that increasing obliquity of quick muscle insertion allows for more rapid adduction of the valves. Now, the quick muscle of swimming mono- myarians is always inclined with its right insertion nearer the hinge than is the left insertion. Since the left insertion does not move ventrally as rapidly as the right, the total dorso-ventral obliquity decreases during growth. If ventral movement of the right insertion were greater, the advantages gained by increasing moment might be offset by the detriment of decreased dorso-ventral obliquity. As with Raup’s ammonoids (1967), selection can optimize no one mechanical factor since there are conflicting demands upon form. The ‘best’ solution is a compromise among these factors. Moments have occasionally been considered in studies on the functional morphology of muscles in fossil groups. Jaanusson and Neuhaus (1963) have identified several solutions evolved by brachiopods for the problem of placing diductor muscles so that their force attains its largest possible moment. Adamczak (1968, p. 25) notes that Devonian leperditiid ostracods either have a large adductor field situated dorsal to the mid-height of the valves or a smaller one situated ventral to it. I suggest that this might represent two ways of attaining a similar, required moment. 4. Antero-posterior motion of quick muscle. The movement of quick muscle from a posterior to a more central position in each sample entails no improvement in moment, since distance to the hinge does not change. This motion does, however, bring the quick muscle into an ever more convex part of the shell, thereby increasing its relative length. Although this lengthening does not raise muscular strength (= cross-sectional area), it does increase the mass of the muscle and hence its power reserve. Another proposal was advanced by Marceau (1936) who claimed that motion of the quick muscle to a more STEPHEN JAY GOULD: SWIMMING IN SCALLOPS 91 central position brings it into closer alignment with the internal ligament, so that it may oppose the ligament’s opening stress with a maximum strain. Thus, each allometric trend proceeds in a direction that provides better design for swimming and counteracts the difficulties of increasing size. This cannot be a complete explanation. Swimming ability is lost at large sizes. Moreover, with the rate of allometry constantly decreasing as size increases, less and less compensation is provided as the problems of size become more and more severe. I am intrigued with the idea (though I doubt its truth) that, for some genetic or developmental reason, growth might be con- strained as linear, thereby limiting the potential for allometric compensation. In any case, our attempts to explain adaptation suffer when we ignore the mechanical pro- perties of form and the insights of engineering. Scallops, among other things, are swim- ming machines of imperfect design. This design improves as the intrinsic process of growth imposes continually greater challenges upon its operation. Acknowledgements. To my friends in other fields, who helped me through arguments (and furnished some) and who gave me access to literature and libraries in occult is locis, I am especially grateful: Drs. P. Kleban, G. Oertel, A. Shapiro, R. Siever. I apologize for what I have not understood properly. Many biologists offered their aid and welcome scepticism: R. McN. Alexander, W. Bock, C. Harrisson, G. Mayer, R. Thomas, S. Vogel, T. Waller. K. Boss kindly lent specimens from the M.C.Z. collection of living molluscs; J. Trey and K. Winston-Hevelin helped with measurements while H. Holland and C. Jones prepared the illustrations. Supported in part by a grant from the Clark Fund, Harvard University. REFERENCES abel, o. 1929. Palaobiologie und Stcimmesgeschichte. Gustav Fischer Verlag, Jena, 423 pp. adamczak, F. 1968. Paleocopa and Platycopa from Middle Devonian rocks in the Holy Cross Moun- tains, Poland. Stockholm Contr. Geol. 17, 1-109. affleck, R. J. 1950. Some points in the function, development and evolution of the tail in fishes. Proc. Zool. Soc. London, 120, 349-68. Alexander, r. mcn. 1965. The lift produced by the heterocercal tails of Selachii. J. exp. Biol. 43, 131-8. 1966. Rubber-like properties of the inner hinge-ligament of Pectinidae. J. exp. Biol. 44, 119-30. 1968. Animal mechanics. Univ. Wash. Press, Seattle, 346 pp. bainbridge, r. 1958. The speed of swimming of fish as related to size and to the frequency and ampli- tude of the tail beat. J. exp. Biol. 35, 109-33. baird, r. H. 1958. On the swimming behaviour of scallops ( Pecten maximus L.). Proc. Malacol. Soc. London, 33, 67-71. bayliss, l. e., boyland, e., and Ritchie, a. d. 1930. The adductor mechanism of Pecten. Proc. Roy. Soc. London, 106, 363-76. bennett, L. 1970. Insect flight: lift and rate of change of incidence. Science, 167, 177-9. benson, r. h. 1967. Muscle-scar patterns of Pleistocene (Kansan) ostracodes in C. Teichert and E. L. Yochelson (eds.). Essays in paleontology and stratigraphy. Univ. Kansas Press, Lawrence, 211-41. bone, q. and Roberts, b. l. 1969. The density of elasmobranchs. J. mar. biol. Assoc. U.K. 49, 913-37. bonner, J. t. 1952. Morphogenesis: an essay on development. Princeton Univ. Press, Princeton, 296 pp. 1968. Size change in development and evolution; in Paleobiological aspects of growth and development, a symposium. Paleont. Soc., Mem. 2 (J. Paleont. 42 (5), suppl.), 1-15. breder, c. m., jr. 1930. On the structural specialization of flying fishes from the standpoint of aero- dynamics. Copeia, 114-21. brown, r. h. J. 1963. The flight of birds. Biol. Rev. 38, 460-89. 92 PALAEONTOLOGY, VOLUME 14 buddenbrock, w. v. 1911. Untersuchungen Liber die Schwimmbewegungen und die Statocysten der Gattung Pecten. Sitz. Heidelberger Akad. fViss. 28, 1-24. caddy, j. f. 1968. Underwater observations on scallop ( Placopecten magellanicus) behavior and drag efficiency. /. Fish. Res. Bd. Canada, 25, 2123-41. chapman, r. F. 1969. The insects: structure and function. American Elsevier, New York, 819 pp. clarke, J. m. and ruedemann, r. 1912. The Eurypterida of New York. Mem. N.Y. State Mas. 14 (1). 439 pp. cock, a. g. 1966. Genetical aspects of metrical growth and form in animals. Quart. Rev. Biol. 41, 131-90. denton, e. J. 1964. The buoyancy of marine mollusks. In wilbur, k. m. and yonge, c. m. (eds.), Physi- ology of mollusca, vol. i. Academic Press, New York, 425-34. dryden, H. L., murnaghan, F. d., and bateman, h. 1956. Hydrodynamics. Dover, New York. 634 pp. fairbridge, w. s. 1953. A population study of the Tasmanian ‘commercial’ scallop Notovola meridion- als (Tate) (Lamellibranchia, Pectinidae). Aust. J. Mar. Freshwater Res. 4, 1-40. farmer, g. j. and beamish, F. w. h. 1969. Oxygen consumption of Tilapia nilotica in relation to swim- ming speed and salinity. J. Fish. Res. Bd. Canada, 26, 2807—21 . goldstein, s., et cd. 1965. Modern developments in fluid dynamics, vol. ii. Dover (reprint of 1938 edn.). New York, 331-702. gould, s. J. 1966. Allometry and size in ontogeny and phylogeny. Biol. Rev. 41, 587-640. 1968. Ontogeny and the explanation of form: an allometric analysis; in macurda, d. b. (ed.), Paleobiological aspects of growth and development, a symposium. Paleont. Soc., Mem. 2 (/. Paleont. 42 (5), suppl.), 81-98. 1970. Evolutionary paleontology and the science of form. Earth Sci. Rev. 6, 77-119. -and garwood, r. a. 1969. Levels of integration in mammalian dentitions: an analysis of correlations in Nesophontes micrus (Insectivora) and Oryzomys couesi (Rodentia). Evolution, 23, 276-300. gray, j. 1968. Animal locomotion. Weidenfeld and Nicholson, 479 pp. grove, a. J. and Newell, g. e. 1936. A mechanical investigation into the effectual action of the caudal fin of some aquatic chordates. Ann. Mag. Nat. Hist. 17, 280-90. gutsell, J. s. 1931. Natural history of the bay scallop. Bull. U.S. Bur. Fish. 46, 569-632. Hancock, d. a. 1965. Adductor muscle size in Danish and British mussels and its relation to starfish predation. Ophelia, 2, 253-67. Harris, J. e. 1936. The role of the fins in the equilibrium of the swimming fish. I. Wind tunnel tests on a model of Mustelus canis (Mitchell). J. exp. Biol. 13, 476-93. hill, a. v. 1950. The dimensions of animals and their muscular dynamics. Sci. Prog. 38, 209-30. holst, E. von and kuchemann, d. 1942. Biological and aerodynamical problems of animal flight. J. Roy. Aeronaut. Soc. 46, 39-56. hoyle, g. 1964. Muscle and neuromuscular physiology. In wilbur, k. m. and yonge, c. m. (eds.). Physiology of mollusca, vol. i. Academic Press, New York, 313-51. hubbs, c. l. 1933. Observations on the flight of fishes, with a statistical study of the flight of the Cypselurinae and remarks on the evolution of the flight of fishes. Pap. Mich. Acad. Sci. Arts Letters, 17, 575-611. jaanusson, v. and neuhaus, h. 1963. Mechanism of the diductor muscle in articulate brachiopods. Stockholm Contr. Geol. 13, 1-8. jackson, r. t. 1890. Phylogeny of the Pelecypoda. The Aviculidae and their allies. Mem. Boston Soc. Nat. Hist. 4, 277-400. Jacobs, e. 1963. Experimental methods — wind tunnels. Part 2. In durand, w. f. (ed.), Aerodynamic theory, vol. iii. Dover (reprint of 1935 edn.). New York, 319-50. Jeffries, R. p. s. and minton, p. 1965. The mode of life of two Jurassic species of ‘Posidonia’ (Bivalvia). Palaeontology, 8, 156-85. karman, th. von and burgers, j. m. 1963. General aerodynamic theory — perfect fluids. In durand, w. f. (ed.), Aerodynamic theory, vol. ii. Dover (reprint of 1935 edn.), New York. kauffman, e. G. 1969. Form, function and evolution. In cox, L. r. et al. (eds.). Treatise on invertebrate paleontology. Part N, Mollusca 6, Bivalvia, 129-205. University of Kansas. STEPHEN JAY GOULD: SWIMMING IN SCALLOPS 93 kim, y. s. 1969. An observation on the opening bivalve mollusks (sic) by starfish, Asterias amurensis. Bull. Fcic. Fish. Hokkaido Univ. 20, 60-3. kornicker, l. s. 1959. Observations on the behavior of the pterpod Creseis acicula Rang. Bull. mar. Sci. 9, 331-6. kramer, g. 1959. Die funktionelle Beurteilung von Vorgangen relativen Wachstums. Zool. Anz. 162, 243-66. marceau, F. 1936. Sur quelques proprietes speciales des muscles adducteurs des mollusques acephales en rapport avec leur disposition et leur structure. Mem. Mus. roy. d'Hist. Nat. Beige 3, 941-75. Merrill, a. s. 1961. Shell morphology in the larval and postlarval stages of the sea scallop, Placopecten magellanicus (Gmelin). Bull. Mus. Comp. Zool. 125, 3-20. meunier, k. 1959 a. Die Allometrie des Vogelfliigels. Z. wiss. Zool. 161, 444-82. 19596. Die Grossenabhangigkeit der Korperform bei Vogeln. Z. wiss. Zool. 162, 328-55. millikan, c. b. 1934. Further experiments on the variation of the maximum-lift coefficient with turbulence and Reynolds Number. Trans. Am. Soc. Mech. Eng. 56, 815-18. montuori, a. 1913. Les processus oxydatifs chez les animaux marins en rapport avec la loi de super- ficie. Arch. ital. Biol. 59, 213-34. moore, j. k. and marshall, n. 1967. An analysis of the movements of bay scallops Aequipecten irradians in a shallow estuary. Proc. Nat. Shellfish. Ass. 57, 77-82. moore, r. c. 1962. Revision of Calceocrinidae. Univ. Kansas Paleont. Contr. Echinodermata 4, 1-40. morton, J. e. 1954. The biology of Limacina retroversa. J. Mar. Biol. Ass. U.K. 33, 297-312. nachtigall, w. 1967. Aerodynamische Messungen am Tragfliigelsystem segelnder Schmetterlinge. Z. vergl. Physiol. 54, 210-31. olsen, a. M. 1955. Underwater studies on the Tasmanian commercial scallop, Notovola meridionalis (Tate) (Lamellibranchia : Pectinidae). Aust. J. Mar. Freshwater Res. 6, 392-409. olson, e. c. and miller, r. l. 1959. Morphological integration. Univ. of Chicago Press, Chicago, 317 pp. Packard, a. s. 1871. The embryology of Limulus Polyphemus. An:. Nat. 4, 498-502. pennycuick, c. j. 1960. Gliding flight of the fulmar petrel. J. exp. Biol. 37, 330-38. rashevsky, n. 1960. Mathematical biophysics, vol. ii. Dover, New York, 462 pp. raup, d. m. 1967. Geometric analysis of shell coiling: coiling in ammonoids. J. Paleont. 41, 43-65. reed, s. c., williams, c. m., and chadwick, l. e. 1942. Frequency of wing-beat as a character for separating species, races and geographic varieties of Drosophila. Genetics, 27, 349-61. rees, w. J. 1957. The living scallop. In cox, i. (ed.), The scallop. Shell Transport and Trading Co. Ltd., London, 17-32. rensch, b. 1960. Evolution above the species level. Columbia Univ. Press, New York, 419 pp. rudwick, m. J. s. 1961. The feeding mechanism of the Permian brachiopod Prorichthofenia. Palaeon- tology, 3, 450-71. 1964. The inference of function from structure in fossils. Brit. J. Phil. Sci. 15, 27-40. 1968. Some analytic methods in the study of ontogeny in fossils with accretionary skeletons; in Paleobiological aspects of growth and development, a symposium. Paleont. Soc. Mem. 2 (J. Paleont. 42 (5) suppl.), 35-49. sandberg, p. 1964. The ostracod genus Cyprideis in the Americas. Stockholm Contr. Geol. 12, 1-178. smith, j. m. 1968. Mathematical ideas in biology. Univ. Press, Cambridge, 152 pp. spjeldnaes, n. 1957. The Middle Ordovician of the Oslo Region, Norway. 8. Brachiopods of the sub- order Strophomenida. Norsk Geol. Tids. 37, 1-214. Stanley, s. m. (in press). Relation of shell form to life habits in the Bivalvia (Mollusca). Mem. Geol. Soc. Am. tamura, t. 1929. The power of the adductor muscle of the oyster, Ostraea circumpicta Pils. Science Rep. Tohoku Imp. Univ. Ser. 4 Biol. 4, 259-79. taylor, j. d., Kennedy, w. j., and hall, a. 1969. The shell structure and mineralogy of the Bivalvia. Introduction, Nuculacea— ' Trigoniacea. Bull. Brit. Mus. (Nat. Hist.) Zool. Suppl. 3, 125 pp., 29 pi. thayer, c. w. (in press). Adaptive features of swimming monomyarian bivalves. Posti/la, Peabody Mus. Nat. Hist. Yale Univ. thom, a. and swart, p. 1940. The forces on an airfoil at very low speeds. J. roy. Aeronaut. Soc. 44, 761-70. Thompson, d. w. 1942. On growth and form. Cambridge Univ. Press, Cambridge, 1 1 16 pp. 94 PALAEONTOLOGY, VOLUME 14 trueman, e. r. 1953. Observations on certain mechanical properties of the ligament of Pecten. J. exp . Biol. 30, 453-67. ■ 1966. Bivalve mollusks: fluid dynamics of burrowing. Science, 152, 423-5. 1967. The dynamics of burrowing in Ensis (Bivalvia). Proc. roy. Soc. London, 166, 459-76. verrill, a. e. 1897. A study of the family Pectinidae, with a revision of the genera and subgenera. Trans. Conn. Acad. Arts Sci. 10, 41-95. vogel, s. 1967. Flight in Drosophila. III. Aerodynamic characteristics of fly wings and wing models. J. exp. Biol. 46, 431-43. waller, t. r. 1969. The evolution of the Argopecten gibbus stock (Mollusca: Bivalvia), with emphasis on the Tertiary and Quaternary species of Eastern North America. Paleont. Soc., Mem. 3 (J. Paleont. 43 (5), suppl.), 125 pp. warburton, f. e. 1955. Feedback in development and its evolutionary significance. Amer. Nat. 89,, 129-40. weis-fogh, t. 1956a. Biology and physics of locust flight. II. Flight performance of the desert locust (Schistocerca gregaria). Phil. Trans, roy. Soc. London, 239, 459-510. 1956ft. Biology and physics of locust flight. IV. Notes on the sensory mechanisms in locust flight. Ibid. 239, 553-84. 1961. Power in flapping flight. In ramsay, j. a. and wigglesworth, v. b. (eds.). The cell and the organism. Essays presented to Sir James Gray. Cambridge Univ. Press, Cambridge, 283-300. and jensen, m. 1956. Biology and physics of locust flight. I. Phil. Trans, roy. Soc. London, 239, 415-58. went, F. w. 1968. The size of man. Am. Sci. 56, 400-13. white, j. f. and gould, s. J. 1965. Interpretation of the coefficient in the allometric equation. Am. Nat. 99, 5-18. yonge, c. M. 1936. The evolution of the swimming habit in the Lamellibranchia. Mem. Mas. roy . d'Hist. Nat. Beige, 3, 77-100. 1951. Studies on Pacific Coast mollusks. III. Observations on Hinnites multirugosus (Gale). Univ. Cal. Publ. Zool. 55, 409-20. 1953. The monomyarian condition in the Lamellibranchia. Trans, roy. Soc. Edinburgh, 52, 443-78. — — 1967a. Form, habit and evolution in the Chamidae (Bivalvia) with reference to conditions in the rudists (Hippuritacea). Phil. Trans, roy. Soc. London, 252, 49-105. 1967ft. Observations on Pedum spondyloideum (Chemnitz) Gmelin, a scallop associated with reef-building corals. Proc. Malac. Soc. London, 37, 311-23. zeigler, J. M. and gill, B. 1959. Tables and graphs for the settling velocity of quartz in water, above the range of Stokes' Law. Reference No. 59-36 W.H.O.I., 13 pp. STEPHEN JAY GOULD Museum of Comparative Zoology Harvard University Cambridge, Mass. 02138 U.S.A. Typescript received 20 April 1970 AN ENDOPUNCTATE RHYNCHONELLID BRACHIOPOD FROM THE VISEAN OF BELGIUM AND BRITAIN by C. H. C. BRUNTON Abstract. The punctate rbynchonellid Terebratula trilatera de Koninck is proposed as the type species of a new genus, Tretorhynchia. Specimens are described from Visean rocks of Belgium, the United Kingdom, and from Ireland; their shell structure and intraspecific variation are discussed. During 1969 two specimens of a rhynchonellid brachiopod came to my attention from Visean rocks of Derbyshire; the first as a museum inquiry, the second from Dr. G. A. Cooper, of the United States National Museum, with whom I had collected specimens at Treak Cliff some months previously. These specimens were unusual in their apparent punctation. Dr. Cooper remarked (in litt. 1969) that his specimen was not Rhynchopora , up till now the only well-known punctate rhynchonellid genus described, and he kindly agreed to let me use his specimen and describe the species. Acknowledgements. I wish to thank the following for their assistance in lending material: Dr. G. A. Cooper, Washington; Mr. M. Mitchell of the Institute of Geological Sciences, Leeds; Mr. C. E. Palmer of the Glasgow Museum; Dr. W. D. I. Rolfe of the Hunterian Museum, Glasgow; and Dr. P. Sartenaer of the Brussels Museum, Belgium. My thanks are also due to my assistant, Mr. A. Rissone, for technical work, and the Museum’s Photographic Studio and Electron Microscope Unit for help in the production of the plates. Classification and terminology follows the Brachiopoda Treatise (Williams et al. 1965). A search of the material in the British Museum (Natural History) yielded twenty- eight specimens, which are considered to be conspecific, from the Lower Carboniferous of the British Isles, in addition to the ten lent by Dr. Cooper, and the ten lent by the Institute of Geological Sciences, Leeds. Many of these were labelled as Rhynchonella trilatera (de Koninck). This species was described by de Koninck (1843, p. 292) from the Lower Carboniferous of Vise, Belgium, and is represented in the Natural History Museum by eight specimens from Belgium, five of which are from de Koninck’s collec- tion and two of these still bear the thin blue paper labels given to them by de Koninck himself. One of de Koninck’s specimens (B. 12642), now in the Davidson Collection, is accompanied by a label in Davidson’s writing, which reads: ‘ Rhvneh . trilatera. de Kon. Carb. Limestone Vise, Belgium. Sent to me by De Koninck as his type and for com- parison with English specimens’ (PI. 11, figs. 5, 6). These fifty-six specimens form the basis of this study which aims at deciding the relationships of the British specimens with R. trilatera (de Koninck) from Belgium, elucidating the nature of the apparent puncta- tion of the shell, and deciding upon the taxonomic position of the British and Belgian specimens. To assist in this study portions of shell and complete specimens have been studied both optically and by scanning electron microscope (PI. 11, figs. 7-14). All fifty-four [Palaeontology, Vol. 14, Part 1, 1971, pp. 95-106, pis. 11-12.] 96 PALAEONTOLOGY, VOLUME 14 specimens in which the brachial valve is complete (commonly the tip of the pedicle valve umbo is broken), have been measured and counts of ribbing on the brachial valves noted. This data has been plotted graphically and, where the number of specimens has allowed, it has been treated statistically in order to investigate variation between the Belgian, British, and Irish specimens (Tables 1-3). Finally, two specimens have been sectioned serially in order to discover the internal hinge and crural structures (text- figs. 1-12), using a lathe grinder (Hendry, Rowell, and Stanley 1963). Relationships between the British and Belgian specimens De Koninck (1843, p. 292, pi. 14, figs, la-d) described Terebratula trilatera from the Carboniferous Limestone of Vise as rare. He stressed the resemblance in shape to an isosceles triangle and stated that his species had 18-22 angular ribs. In these charac- teristics, and other respects, his description is adequate for most of the British material. However, he made no comment as to the nature of the shell substance and the relative dimensions cited, as well as those of the figured specimen, differ from those typical of British specimens in being longer than wide and thicker relative to length. Later, in 1887, de Koninck redescribed his species giving dimensions which accord closely with those of the specimens from Britain ; the length and width being given as equal and the thickness as 64% of these dimensions. Fortunately the situation is relieved further by having four well-authenticated specimens named trilatera by de Koninck and a fifth almost certainly from his collection. In all known respects these specimens match with the British material and the two groups of specimens are considered to be conspecific. Unfortunately, the number of specimens available from Belgium is insufficient to test for significance in difference between their growth axes and those obtainable from British specimens. Graphical plotting suggests that there would be no significant difference (text-figs. 13-15). Shell structure In assembling the material studied an important criterion was the apparent shell punctation. This feature, previously noted by Dr. Cooper and myself, has given impetus to the investigation and, together with its outline, makes Terebratula trilatera an easy species to recognize. From low-power optical inspection, at x30, it is clear that the shell substance is patterned by minute outwardly projecting protuberances evenly spaced throughout the secondary shell layer with a frequency of from 150 to 180 per mm2. Rarely, on exfoliated shell near the inner surface of the valve, the protuberances are dark at the centre, as if filled with fine sediment. After ultrasonic cleaning minute pores can be distinguished penetrating these structures. At magnifications of from one to two thousand, using a scanning electron microscope, it is clear that the fibres of the secondary shell layer are bent outwards around a central hole (PL 11, figs. 8, 10, 13), just as in living punctate brachiopods, and that the shell substance of this species can be described as endopunctate. It is possible to find patches of well differentiated non-fibrous outer primary layer (PI. 11, figs. 9, 10), as in living brachiopods, on only a few specimens. In such areas the punctae are difficult to distinguish owing to the fact that they terminate close to the junction between the primary and secondary shell layers. This is unlike living punctate brachiopods in which the punctae extend well into the primary layer and C. H. C. BRUNTON: AN ENDOPUNCTATE RHYNCHONELLID BRACHIOPOD 97 are capped by thin ‘canopies’ of primary shell through which the ‘brush’ extended (Owen and Williams 1969). It has not been possible to distinguish canals, which might have accommodated the ‘brush’, within the primary layer above the punctae of T. trilatera, and this adds to the difficulty of recognizing punctae where primary shell is preserved. Commonly sediment within the punctae and slight recrystallization of the surrounding shell obscures the punctal cavity. However, inspection of cellulose acetate peels taken from various layers of the shell of T. trilatera and the punctate terebratulide Dielasma, from similar Visean lithologies, provides convincing evidence of both having shells with similarly concentrated punctae and associated features of shell micro- structure. Thus, we now know that the specimens may be assigned to de Koninck’s species trilatera and that this species is endopunctate. The remaining problem is its taxonomic position. Presently the only well-known punctate genus of the Rhynchonellida is Rhynchopora, erected by W. King in 1865 when describing the punctate shell Terebratula geinitziana de Verneuil from Permian rocks of Russia. This genus is characterized by its dorsibiconvexity and by having a strong fold and sulcus in the brachial and pedicle valves respectively; the anterior commissure is strongly folded by a linguiform extension of the pedicle valve. These features contrast with T. trilatera and led Dr. Cooper to remark that the Treak Cliff specimens in his collection could not be assigned to Rhynchopora. Muir-Wood (1955, p. 74) discussed the genus, pointing out that the species assigned are widely distributed throughout Carboniferous and Permian rocks and that they ‘belong to more than one genus’. Drot (1964) described a new Famennian species, from Morocco as Rhynchopora ? morini, which seems to be punctate but differs from Rhyncho- pora geinitiziana in details of external morphology. The small endopunctate species Rhynchopora youngii Davidson (1880, p. 286) has a strongly folded commissure and ribs that do not arise from the umbones; it was reported, in Davidson, from Upper Visean and Lower Namurian rocks of the Dairy area, Ayrshire. This species is quite unlike T. trilatera and although it also differs from the type species of Rhynchopora in its ribbing, it is related more closely to that genus than to Tretorhynchia, the new genus erected herein. It appears to be a rare species, only being known to the author by ten specimens in the Young Collection (seven in the Hunterian Museum, Glasgow, and three, figured by Davidson, in the Glasgow Art Gallery and Museum). Two other reportedly punctate species of Rhynchopora from Lower Carboniferous, Visean, rocks are R. deltoidea Reed (1954, p. 188) and R. longa Afanas’yeva (1969, p. 62); the former from the Lower Limestone Group of east Scotland and the latter from the Onon River, Transbaykalia S.S.R. Both species are longer than wide and sulcate, and appear reasonably to have been assigned to Rhynchopora. A poorly understood genus, which might be punctate, is Paryphorhynchopora Simorin (1956, p. 245), based upon Pugnoides korsakpaica Nalivkin 1937, from Tournaisian strata in north-east Kazakhstan, U. S.S.R. Nalivkin made no mention of a punctate structure, but Simorin wrote of the valves being covered by rows of minute, closely spaced, slightly elongate pores giving the impression of fine radial striations like those of Paryphorhynchus Weller 1914 (= Paraphorhynchus Weller 1905). Simorin briefly com- pared his genus with Rhynchopora, saying that the shape and arrangement of the pores differs. Unfortunately, neither the illustrations of Simorin nor of Nalivkin are good H C 7893 98 PALAEONTOLOGY, VOLUME 14 enough to be sure of recognizing punctation. However, it seems likely that the rows of fine pores described may be no more than surface ornamentation, as in Porostictia Cooper (1955), based upon the Upper Devonian species Paraphorhynchus perchaensis Stainbrook 1947 from New Mexico; in this species, the ‘pores’ are surface elongate pits which do not penetrate the shell. Thus, in the absence of full information on Parypho- rhynchopora, it is impossible to know if some Devonian and Lower Carboniferous seemingly punctate species should be assigned to this genus or not. However, whatever the true nature of the shell of Paryphorhynchopora the external morphology is quite unlike that of de Koninck’s species and it seems necessary, therefore, to erect a new genus based upon T. trilatera de Koninck. Dunbar and Condra (1932, p. 295) argued that the North American Pennsylvanian species they assigned to Rhynchopora indicated that this genus should be placed in the Terebratulida, perhaps within the Centronellidae. Sections of their specimens reveal a posteriorly perforated hinge plate covering a cavity between it and the septalium. These structures, the punctation, and the vertically disposed blade-like brachial supports led Dunbar and Condra to exclude their material from the Rhynchonellida. The internal structures of the American species Rhynchopora hamburgensis Weller and R. pustulosa (White) described by Dunbar and Condra, and R. magnicosta Mather, described by Weller in 1914 as rhynchonellid, differ from those of T. trilatera, whose cardinalia is not unlike that of some terebratulids such as the Permian genus Yochelsonia. Punctation of the brachiopod shell has evolved and been lost from various brachio- pod stocks during Phanerozoic time and it does not seem too unlikely that the Rhyncho- poridae should be the sole punctate family of rhynchonellids. Furthermore, as is shown herein, the punctation of T. trilatera differs in detail from that normal for Terebratulida. There is no evidence as yet for the brachiophore supports being in the form of a loop, as in the Terebratulida. Order rhynchonellida Kuhn 1 949 Superfamily rhynchoporacea Muir-Wood 1955 Family rhynchoporidae Muir-Wood 1955 Genus tretorhynchia nov. Type species. Terebratula trilatera de Koninck 1843. Diagnosis. Rhynchoporidae approximating an equilateral triangle in outline, with bi- convex lateral profile and lacking fold in anterior commissure. Typically 18-22 persistent costae. Septalium and strong socket ridges; dental plates delicate and close to sides of valve. Range. Lower Carboniferous, middle to upper Visean. Discussion. At present only the type species is assigned to this genus. In outline and profile it is similar to some tetracamerids, but differs in lacking either a folded margin or complex dental plates, and in being endopunctate. Pseudowellerella is similar in its persistent costae and approaches a triangular outline, but it is sulcate, has truncated antero-lateral corners and is impunctate. The generic name is derived from ‘tretos' — a Greek word meaning perforated — combined with the root of Rhynchonel/a. C. H. C. BRUNTON: AN ENDOPUNCTATE RHYNCHO NELLI D BRACHIOPOD 99 Tretorhynchia trilatera (de Koninck) Plates 11 and 12 1843 Terebratula trilatera de Koninck, p. 292, pi. 14, figs. la-d. 1861 Rhynchonella ? trilatera (de Koninck); Davidson, p. 109, pi. 24, figs. 23-6. ?1 861 Rhynchonella pleurodon Phillips; Davidson, pi. 23, fig. 10a. 1887 Rhynchonella trilatera (de Koninck); de Koninck, p. 50, pi. 16, figs. 68-83. Diagnosis. Outline approximating an equilateral triangle, with rounded antero-lateral margins and pointed umbones. Postero-lateral flanks flattened; lateral profile variable but mean thickness approximately five-eighths mean width. Both valves slightly sulcate posteriorly. Anterior commissure not folded. Commonly 18-22 strong angular costae on brachial valves, normally seven in 4 mm at 4 mm from dorsal umbo. Pedicle valve with median rib. Brachial valve interior with short low median septum supporting septalium and with deep crura. Pedicle valve with short thin dental plates. Shell sub- stance normal but finely endopunctate. Type specimen. I am told by Dr. Vandercammen (in litt. November 1969), of the Institut Royal des Sciences Naturelles, Belgium, that his institution has no type specimens of T. trilatera de Koninck, nor specimens that can be said with any certainty to have been figured by de Koninck in 1843. The Brussels museum does, however, have five specimens figured by de Koninck in 1887, and Dr. Sartenaer has been kind enough to lend me three of them from which to choose the type. The type specimen here chosen is no. I.G. 27386 (PI. 11, figs. 1—4), figured by de Koninck in 1887, pi. 16, figs. 69-75; it cannot be designated as lectotype because it is not demonstrably one upon which de Koninck based his description in 1843. This specimen is unusually wide compared to its length, but in other respects is like the majority of specimens studied. Some endopunctate shell material is preserved and dental plates are visible within the ventral umbo. Other material. In the British Museum of Natural History: four specimens from the de Koninck Collection from Visean rocks of Belgium; four specimens from the Visean (B2) of the Treak Cliff, Castleton area, Derbyshire; eight from the Visean of Wetton, Staffordshire ; four specimens from the Visean of Anglesey; four specimens from Bolland, and three from Settle, Yorkshire, probably also Visean; four specimens from Lower Carboniferous rocks of the Cork area, Ireland. Lent by the Institute of Geological Sciences, Leeds: four specimens from the Visean (B2) of the Treak Cliff area; two from Castleton; one from Narrowdale, Derbyshire; three from Alstonfield, Derbyshire (referred to by Davidson 1861 and forming the basis of his illustrations on pi. 24, fig. 26); all these from Visean rocks. Lent by the Smithsonian Institution, Washington: ten specimens from the Visean (B2) of Treak Cliff, Derbyshire. Description. The species is markedly triangular in outline with maximum width occurring at about three-quarters of the length of the shell. Mean width slightly exceeds mean length in the Belgian and British specimens. The anterior margin may be straight or slighly convex or concave medianly. The variable thickness correlates more closely with length than with width (Table 1). The flanks are flattened, but posteriorly the com- missure protrudes at a rudimentary hinge line (PI. 12, fig. 9). The brachial valve median sulcation follows the line of the median septum (PI. 11, fig. 5) and on this valve 18-22 persistent costae are commonly developed; these widen anteriorly but they diminish in size laterally. On pedicle valves there is a median costa; on brachial valves a pair of submedian costae so that the total number of dorsal costae is commonly an even number 100 PALAEONTOLOGY, VOLUME 14 (Table 2). On only two specimens subequal branching of costae on the brachial valves led to the development of costellae nearly equal in size to the parent costae. Naturally, on the pedicle valve a corresponding intercalation of a costella occurred. The pedicle valve interior has short thin dental plates which do not continue anteriorly as ridges on the floor of the valve. The teeth are large, extending dorso-medianly for about two- thirds of the valve width (at that particular distance from the umbo; text-fig. 4). The brachial valve interior has a median septum, about 2 mm long, which posteriorly forms a septalium by fusion with short crural plates. Crura are distally narrow but deep and table 1. Statistics of length (!) and width (w) of brachial valves, and shell thickness (th) of T. trilatera specimens from the United Kingdom, Belgium and Ireland. The arithmetic coefficients of correlation (r) are given for parameters where the number of specimens is sufficient United Kingdom Belgium Ireland 1 (var.) = 8-99 (2-725) 6-81 (3-630) 8-28 (1-325) w (var.) = 9-48 (3-221) 7-43 (1-646) 6-90 (0-865) tTi (var.) = 5-82 (2-254) 4-52 (2-720) 4-64 (0-832) r for l/w = 0-848 r for l/th = 0-769 r for with = 0-674 n = 43 6 5 arise from the anterior ends of the large inner socket ridges (text-fig. 16). In the sectioned specimens the anterior tips of the crura may be broken, so their length may have been greater than indicated by the serial sections. Discussion. The species is distinctive in many respects. Internally, the articulation is unusually strongly developed (perhaps a characteristic linked with the lack of com- missural folding which normally, in rhynchonellaceans, assists in the fit of one valve with another) so that large inner socket ridges are present. The crura appear to extend EXPLANATION OF PLATE 11 Tretorhynchia trilatera (de Koninck), Lower Carboniferous, Visean. Figs. 1-4. Ventral, dorsal, anterior ( x 2-6) and posterior (x 3-8) views of the type specimen from Vise, Belgium, De Koninck Collection, IRSN, no. I.G. 2738b. Figs. 5, 6. Dorsal (x 5) and posterior (x 20) views of an internal cast from Vise, Belgium, showing the positions of the dental plates and cardinalia. B 12642. Figs. 7-14. ‘Stereoscan’ scanning electron micrographs of specimens coated with gold. 7. Composite ventro-lateral view of a young specimen from Llanfair, Anglesey, showing the shell ornamentation at x 10. BB 58456. 8-12. Details of the shell structure as illustrated by the I.G.S., Leeds, specimen no. 55 from Alstonfield, Derbyshire (see PI. 12, figs. 8, 9). The outer surface of the specimen is to- wards the top of each figure. Figs. 8-10 illustrate the junction of the primary to secondary shell, and the distribution of punctae within the secondary shell x 300. Figs. 11, 12 detail punctae well within the secondary layer and at their distal ends, close to the inner surface of the primary layer, where they become capped by shell, x 600. Figs. 13, 14. Details of the punctae in the specimen shown on fig. 7 in which some recrystallization of the shell has occurred. However, flexure of the secondary fibres around the punctae can be distinguished, x 1000. IRSN = Institut Royal des Sciences Naturelles, Brussels. Palaeontology, Vol. 14 PLATE 11 BRUNTON, Carboniferous endopunctate rhynchonellid C. H. C. BRUNTON: AN ENDOPUNCTATE RHYNCHONELLID BRACHIOPOD 101 1 mm. text-figs. 1-12. Transverse serial-sections through T. trilatera (IGS, Leeds specimen RS 3750 from B2 reef limestones, Odin Fissure, north end of Treak Cliff, Derbyshire) showing the internal structures. Much of the external shell substance was missing prior to sectioning. Distances from the brachial valve umbo are given in mm. from the anterior end of these ridges making it impossible to differentiate either the outer hinge plates from inner socket ridges or the crural bases from the inner hinge plates, which fuse medianly on to the median septum. Owing to a shortage of material only two specimens were serially sectioned and the pedicle valve umbones were missing. No cardinal process has been recognized in section, and from the internal mould (PI. 11, fig. 6) this structure was not developed. In comparing the external morphology of the specimens from Belgium, the United Kingdom, and Ireland it is clear that the Irish specimens from the Cork district differ 102 PALAEONTOLOGY, VOLUME 14 table 2. The total number of ribs counted on 54 brachial valves of T. trilatera from the United Kingdom, Belgium, and Ireland Ribs 16 17 18 19 20 21 22 23 24 U n i ted K ingdom 4 2 13 4 10 l 6 0 3 43 Bel g iu m 0 0 2 0 3 0 1 0 0 6 1 reland 2 0 1 1 1 0 0 0 0 5 6 2 16 5 14 1 7 0 3 54 table 3. The number of ribs counted in a width of 4 mm at a distance of 4 mm from the dorsal umbones of T. trilatera from the United Kingdom, Belgium, and Ireland R ibs 6 7 8 9 10 United Kingdom 10 18 9 3 2 42 Belgium i 1 2 0 1 5 Ireland i 1 1 0 2 5 12 20 12 3 5 52 EXPLANATION OF PLATE 12 Tretorhynchia trilatera (de Koninck), Lower Carboniferous. Figs. 1-4. Dorsal, lateral (x3 0) ventral and anterior (x2-7) views of a typically shaped specimen (in dimensions close to those given by de Koninck in 1887) from Wetton, Staffordshire. Davidson Collection. BB 58455. Figs. 5-7. Lateral, dorsal and ventral views ( x 2-5) of a specimen from Alstonfield, Derbyshire, referred to by Davidson (1861) and almost certainly used in his figures of pi. 24. GSL 54. Figs. 8, 9. Anterior and dorsal views ( x 2-7) of a second specimen from Alstonfield, Derbyshire and figured by Davidson (1861, pi. 24, figs. 26). GSL 55. The above two specimens illustrate the short but relatively fat variants of the species. Specimen 55 has an unusually wide hinge line. Figs. 10-12. Dorsal, ventral and lateral views (x3-5) of a specimen from Little Island, Co. Cork, Eire. J. Wright Collection. BB 58457. Figs. 13-15. Dorsal, ventral and lateral views (x 3-5) of an elongate, fat specimen from Little Island, Co. Cork. J. Wright Collection. BB 58458. Figs. 16-18. Dorsal, ventral and lateral views (X2-7) of a broad, thin specimen from Bolland, York- shire. Gilbertson Collection. BB 58461. Figs. 19, 20. Dorsal and ventral views (x 2-5) of a thin specimen from the north end of Treak Cliff, Castleton, Derbyshire. Collected Cooper and Brunton. USNM, Washington. Figs. 21, 22. Dorsal and ventral views (x2-5) of a thick specimen collected with that illustrated in figs. 19, 20. USNM, Washington. Figs. 23-25. Dorsal, ventral and lateral views (x6) of a young specimen from Settle, Yorkshire. Growth lines and shell ornamentation are distinguishable. Davidson Collection. BB 58459. Figs. 26, 27. Dorsal and ventral views ( x 4) of a larger specimen from Settle. Davidson Collection. BB 58460. GSL — Geological Survey, Leeds. USNM — United States National Museum. All other specimens in British Museum (Natural History). Palaeontology , Vol. 14 PLATE 12 23 24 25 27 BRUNTON, Carboniferous endopunctate rhynchonellid C. H. C. BRUNTON: AN ENDOPUNCTATE RHYNCHONELLID BRACHIOPOD 103 from the rest. The Irish specimens (PI. 12, figs. 10-15) are consistently longer than wide and tend to be thicker relative to their width than specimens from the other two regions. Although the rocks from which these specimens were collected are gently folded their shape variation is not entirely the result of tectonic deformation. Measurements of the Cork specimens plot out in positions within the scatter of measurements for all speci- mens, with the exception of length/width measurements (text-fig. 13). With only five 15 ■ 14 - 13 - 12 - 1 i - 10 - 9 • f 8 ' “D * 7 • 6 - 5 ’ 4 - 3 - 2 - 1 ■ 0 - -1 U K spec imens only. o = 108 b- -o-22 -I L I I -I t I 1 I .. — i 1 I 2 3 4 5 6 7 8 9 10 111213 length (mm) text-fig. 13. Arithmetic plots of length and width measurements of 54 brachial valves of T. trilatera. Specimens from the United Kingdom, • ; from Belgium, o ; from Ireland, x ; de Koninck 1887, t- a = growth ratio by reduced major axis of Kermack and Haldane, 1950; b = initial shape (Kermack 1954), i.e. the position at which the axis (a) intersects one of the coordinates. complete specimens available from Cork it is impossible to make valid comparisons and the indications of a smaller total number of ribs, and of more ribs per 4 mm width (Tables 2, 3), probably correlates with the narrowness of these shells. Inspection of broken pedicle valve umbones on two specimens suggests that the dental plates may be slightly more strongly developed in the Cork specimens than in those from elsewhere. However, until more material is available I consider the elongate Cork specimens as no more than a subspecific variant of T. trilatera ; a shape variant that is approached by 104 PALAEONTOLOGY, VOLUME 14 text-fig. 14. Arithmetic plots of brachial valve length and shell thickness of 54 specimens’of T. trilatera. Symbols as in text-fig. 13. 10 8 6 4 2 0 hr, —i ... -T 1_ ,-4-. A ■ » 1— -4 i- j ■■ 1- 2 4 6 8 10 12 14 width text-fig. 15. Arithmetic plots of valve width and shell thickness of 54 specimens of T. trilatera. Symbols as in text-fig. 13. C. H. C. BRUNTON: AN ENDOPUNCTATE RHYNCHONELLID BRACHIOPOD 105 a few specimens from the other localities (PI. 12, figs. 21, 22). It is noteworthy that from whatever locality specimens were collected, those that are more elongate tend to be thicker than specimens of the more usual dimensions, thus retaining ‘body’ cavities of a similar volume. A feature common to many Upper Palaeozoic, and some Mesozoic Rhynchonellida, and seen in this species from each of the three areas, is a wide variation in thickness. ms text-fig. 16. Reconstruction of the cardinalia of T. trilatera, based upon serial sections, as viewed postero-dorsally. c = crus; isr = inner socket ridge; ms = median septum; s = socket. text-fig. 17. Camera-lucida drawings of dorsal and lateral views of four specimens of T. tri- latera from the north end of Treak Cliff, Derbyshire, illustrating variation in thickness within pairs of specimens of the same length. From no locality except Treak CHIT are there sufficient specimens to demonstrate popula- tion variation in regard to this characteristic. Of twelve Treak Cliff specimens collected together it is easy to set aside three in which the relative thickness is markedly less than that of the remaining nine specimens; in other respects all twelve seem identical (text- fig. 17). (Unpublished work of the author on Visean rhynchonellids from a single block of reef limestone from Co. Fermanagh, N. Ireland, shows that in a sample of 85 speci- mens 49 were ‘thick’ and 36 ‘thin’. The growth axes of length plotted against thickness for these groups gave a highly significant difference — p < 0-001.) It is tempting to speculate upon the possibility of this being an example of sexual dimorphism ! In his redescription of the species in 1887 de Koninck includes a set of measurements which fall close to the growth axes for the plots of length/width, length/thickness, and width/thickness for all the specimens studied. His illustrations too, seem more repre- sentative of the species than those of 1843. 106 PALAEONTOLOGY, VOLUME 14 Conclusions. About fifty specimens of an endopunctate rhynchonellid collected from the Visean of Belgium and the British Isles have been studied and assigned to de Koninck’s species Terebratula trilatera. As no congeneric taxon is known a new genus, Tretorhynchia, is described based upon T. trilatera. The articulation is unusually strong and, in common with some other Rhynchonellida, the thickness of this species, relative to its other external dimensions, is very variable. REFERENCES afanas’yeva, g. a. 1969. Carboniferous brachiopods from eastern Transbaykalia. Paleont. J. 3 (2), 200-6, pi. 9. [Translation of Paleont. Zh. 1969, no. 2, 58-65.] cooper, G. A. 1955. New genera of middle Paleozoic Brachiopods. /. Paleont. 29, 45-63, pis. 11-14. davidson, t. 1861. British Carboniferous Brachiopoda. Palaeontogr. Soc. [Monogr.] 2 (5), 31-120, pis. 17-26. 1880. Supplement to the British Carboniferous Brachiopoda. Ibid. 5, 249-313, pis. 30-7. drot, j. 1964. Rhynchonelloidea et Spiriferoidea Siluro-Devoniens du Maroc Pre-Saharien. Notes Mems. Serv. Mines Carte geol. Maroc, 178, 1-237, pis. 1-24. dunbar, c. o. and condra, g. e. 1932. Brachiopoda of the Pennsylvanian system in Nebraska. Bull. Nebraska Geol. Surv. ser. 2, 5, 1-377, pis. 1-44. hendry, r. d., rowell, a. J., and Stanley, j. w. 1963. A rapid parallel grinding machine for serial sectioning of fossils. Palaeontology, 6, 145-7, pi. 20. king, w. 1865. Remarks on the histology of two specimens of Rhynchopora geinitziana de Verneuil, from near the river Oukhta, province of Archangel. Ann. Mag. nat. Hist., Lond. [3], 16, 124-8. de koninck, l. 1842-4. Description des Animaux Fossiles. 2 vols., 1-650, pis. A-H+l-55. Liege. 1887. Faune du calcaire Carbonifere de la Belgique. Ann. Mus. r. Hist. nat. Beige. 14, 1-154, pis. 1-37. muir-wood, H. M. 1955. A history of the classification of the phylum Brachiopoda, 1-124, 12 text-figs. British Museum (Nat. Hist.) London. nalivkin, d. v. 1937. Brachiopods of the Upper and Middle Devonian and Lower Carboniferous of Northeast Kazakhstan. Trudy, tsent. nauchno-issled. geologo-razv. Inst. Moscow, 99, 1-200, pis. 1-39 (Russian and English). Owen, G. and williams, a. 1969. The caecum of articulate Brachiopoda. Proc. R. Soc. B172, 187-201, figs. 1-26. reed, f. r. c. 1954. Lower Carboniferous brachiopods from Scotland. Proc. Leeds phil. lit. Soc. (Sci. Section) 6 (3), 180-90, pis. 1-3. simorin, a. M. 1956. Stratigraphy and brachiopods of the Karaganda basin. Trudy Inst. geol. Akad. Nauk. Kazakh. SSR. 1-300, pis. A+l-27 (in Russian). stainbrook, m. a. 1947. Brachiopoda of the Percha Shale of New Mexico and Arizona. J. Paleont. 21, 297-328, pis. 44-47. weller, s. 1914. The Mississippian Brachiopoda of the Mississippi Valley Basin. Mon. Illinois State Geol. Surv. 1, 1-508, pis. 1-83. williams, a. et al. 1965. Treatise on invertebrate paleontology, moore, r. c. (ed.). Part H. Brachiopoda. 2 vols. xxxi+927 pp., Kansas. C. H. C. BRUNTON Department of Palaeontology British Museum (Natural History) London, S.W. 7 Typescript received 24 March 1970 WRINKLE-LAYER STRUCTURES IN JURASSIC AMMONITES by JOHN RALPH SENIOR Abstract. Wrinkle-layer structures are recorded from Jurassic graphoceratid ammonites. They are compared with similar structures in Palaeozoic ammonoids. There are in the geological literature many reports of shell surface structures in the ammonoids, some of which refer to the characteristic wrinkle-layer structure in the Palaeozoic forms; these have been reviewed recently by House (1970). Among such reports are two records in Jurassic ammonites: Ammonites amoltheus Schlotheim. (Amaltheus margaritatus [de Montfort].) Quenstedt 1846, p. 61. Ammonites turneri J. Sowerby. ( Euasteroceras turneri [J. Sowerby].) Quenstedt 1858, p. 96. Barrande (1877, pp. 1182-9) reviewed these examples, concluding that the structures were the result of ventral spiral ornament on the ostracum in both cases; although the recent review by Walliser (1970) indicates that the shell structure as illustrated in Amaltheus margaritatus may be a form of wrinkle-layer structure. Other than the example figured by Walliser (1970, pi. 4, fig. 5) these reports have not been confirmed in the intervening century, and this has led to the mistaken assumption that wrinkle-layer structures are entirely absent from Jurassic (and Cretaceous) ammo- nites; it is significant that Arkell and others, in the ammonoid volume of the Treatise on Invertebrate Paleontology (Moore 1957), failed to mention wrinkle-layer structures in connection with Mesozoic ammonoids, especially as the structure is well displayed in the Triassic forms (Mojsisovics 1893). During a study of a Bajocian ammonite family, the Graphoceratidae, over 60 indi- vidual ammonites, both macroconchs and microconchs referred to in future as [M] and [m] respectively, have been mechanically dissected in order to help determine their ontogenies. It was found that most of these specimens showed a thin shell layer, up to 0-75 mm thick at 13 mm diameter, superimposed on the dorsal ostracum of the pre- vious whorl, and a few showed a similar layer to be at least locally present in an interior ventral position (text-fig. 1). The positioning of these shell layers in the Graphoceratidae appears to correspond exactly with that of the dorsal and ventral wrinkle-layers (Runzelschicht and Ritzensteifen respectively) in the Palaeozoic goniatites. WRINKLE-LAYER STRUCTURES IN PALAEOZOIC AMMONOIDS The term wrinkle-layer was first brought into English usage by Foord and Crick (1897, p. xx), to explain finely striate or ridged surface textures found not infrequently on goniatite shells. These structures, which are known in the literature under various names (reviewed by House 1970), are first seen fairly early in the goniatite ontogeny (about 5 mm diameter), and are more or less continuously present until the adult [Palaeontology, Vol. 14, Part 1, 1971, pp. 107-13, pis. 13-14.] 108 PALAEONTOLOGY, VOLUME 14 body-chamber. The surface ornament of these layers is fairly distinctive, consisting of closely spaced continuous fine striae or ridges, usually well oriented into radial or spiral patterns (or a combination of both), producing a wrinkle-like surface texture. The form and extent of the wrinkle-layer has been shown by House to vary from group to group in the Palaeozoic ammonoids. text-fig. 1. Diagram showing the indicated continuity between the dorsal and ventral wrinkle-layer structure, based on a specimen of Staufenia sinon (Bayle) [MJ, Schwabischen Alb, south-west Germany. WRINKLE-LAYER STRUCTURES IN THE GR APHOCER ATID AE In the Graphoceratidae dorsal wrinkle-layer structures with surface ornament appear early in the ammonite ontogeny, and have been observed at diameters less than 2 mm at about one and a half volutions, shortly after the nepionic constriction, which occurs at approximately 0-90 mm diameter (c. 360° forward of the prosuture). At this early stage the surface of the shell layer has a moderately strong pustulate ornament, which forms a sub-spiral or sub-radial pattern, the former being the more common type (PI. 14, figs. 1-5). After approximately 40 mm diameter the surface ornament of the dorsal layer is seen to fade gradually, leaving a thin, fairly uniform, undulating layer with growth lines, seen in some specimens to continue to the adult body-chamber (PI. 13, figs. 1-3 and text-fig. 2). It seems likely that the occurrence of dorsal wrinkle- layer structures at larger diameters (over 60 mm diameter) should be quite common and the probable reason for their apparent rarity (Table 1) is the difficulty of recognizing a thin largely unornamented layer, which could easily be destroyed or overlooked when the ammonite is examined. Ventral wrinkle-layer structures in the Graphoceratidae are more seldom seen and are rather specialized in ornament type. It appears from the many medial sections taken J. R. SENIOR: WRINKLE-LAYER STRUCTURES IN AMMONITES 109 from different species in the Graphoceratidae that this ventral layer is probably con- tinuous with the dorsal layer (see text-fig. 1), but is largely unornamented except in the immediate venter area, where spiral and radial ornament is seen, usually as negative impression on the internal mould (PI. 13, figs. 4 and 5). This localized ventral ornament is very pronounced and continuous except immediately orad of each septum; the reason table 1. Showing the distribution of wrinkle- layer structures at present known in the Graphocera- tidae. Dimensions in millimetres Graphoceras v-scriptum (S. Buckman) M Dorsal wrinkle- layer X Diameters observed 4-20 Ventral wrinkle- layer Diameters observed m X 3-50 — — G. concavum (J. Sowerby) M X 3-85 — — m X 410 — — G. impolita (S. Buckman) M X 3-36-1 1-37 — — Brasilia bradfordensis (S. Buckman) M X 4-25 — — B. baylii (S. Buckman) M X 3-41 — — m 7 6-37 — — Ludwigia gigantea (S. Buckman) M 7 10-27 — — L. murchisonae (J. Sowerby) M X 3-00 — — m — — — — L. Itaugi Douville M X 1-30 X 3600 m 7 10-25 — — L. sp. nov. nr X 2-18 — — Leioceras comptum comptum M X 6-24 — — (Reinecke) m X 2-25 — — L. comptum bifidatum (S. Buckman) M X 4-37-13-30 — — m X 3-50 — — L. uncinatum (S. Buckman) M X 2-70-3-46 — — m X 1-45-8-77 X 15-60 L. opalinoides (Mayer) M X 3-72 — — m — — — — L. opalinum (Reinecke) M X 3-25-108-00 — — m — ■ — — — L. costosum (Quenstedt) M X 3-62 — 600 m — — — — L. lineatum (S. Buckman) M X 5-10-24-95 X 65-00 m X 2-88 X 9-33 Staufenia staufensis (Oppel) M X 7-20 X 30-70-170-00 S. sinon (Bayle) M X 1-85-6-27 X 57-75 m X 3-17 — — for this seems obscure. It may be the result of interference by the mural portion of each septum, or of additional effects, such as shell dissolution by cameral fluids during life; though the former seems the more plausible, since the ‘etching’ is localized in effect. The ornament of the ventral wrinkle-layer structure appears to be more persistent throughout conch development and has been seen to diameters of 140 mm, but does not appear until the second or third whorls (at approximately 9 mm diameter), coinciding with keel development. 110 PALAEONTOLOGY, VOLUME 14 Ventral wrinkle-layer structures, as described above should not be confused with the secondary ostracum features — connellen of Holder (1958, p. 22), which form indentations in the ostracum of the keel. Two pattern types have so far been discerned in the ornament of the dorsal shell layer in the Graphoceratidae; the first, typified by Graphoceras impolita (S. Buckman) [M], consisting of semicircular, flat-topped, pustules (PL 14, figs. 3 and 4); the pustules in the second being elliptical and rounded in shape, as in Leioceras uncinatum (S. Buckman) [m] (PI. 14, figs. 1 and 2). The distribution of known wrinkle-layer structures in the Graphoceratidae at the present time is indicated in Table 1. These shell structures in the Graphoceratidae, when compared with those seen in Palaeozoic and Triassic ammonoids, show some differences, particularly in the type of surface ornament. The lack of definite organization in the discontinuous pustulate ornament of the Jurassic ammonites, described here, contrasts with the stronger organization (usually near radiate or prorsiradiate, and to a lesser extent spiral) of the continuous characteristic elevations (‘wrinkles’) associated with the Palaeozoic and early Mesozoic ammonoids (excepting, for example, House, pi. B, fig. 2). Although there are these superficial differences in surface ornament, the shell layer seen in these Jurassic ammonites appears to be equivalent to the goniatite wrinkle-layer, certainly both appear to have been deposited in a similar manner and position and probably had the same EXPLANATION OF PLATE 13 Figs. 1-3. Leioceras opalinum (Reinecke) [M], 1, 2, an almost complete specimen from Burton Brad- stock, Dorset, showing the position of formation of the dorsal wrinkle-layer, adoral of the aperture. Walton Collection, SM J51394. 3, another specimen with a partly broken aperture, showing dorsal wrinkle-layer position on the posterior part of the body-chamber. S. Buckman collection, SM J6358; figured by Buckman (1888, p. 35, pi. 13, figs. 1, 2) as Lioceras opalinum (Reinecke), and later described by the same author (1899, p. xlv) as a syntype of Cypholioceras opaliniforme S. Buckman. Specimen from Harefield Hill, Gloucestershire, lxl; 2x3; 3x1. Figs. 4, 5. Leioceras lineatum (S. Buckman) [m]. Ornament of the ventral wrinkle-layer, on whorl section at diameters of c. 25 mm and 33-70 mm respectively. HU 121 .J. 1 . Both X 3. Fig. 6. Graphoceras concavum (J. Sowerby) [m]. Internal mould, showing the impression of the dorsal wrinkle-layer ornament, of the whorl previous. HU 121. J. 2. x28. EXPLANATION OF PLATE 14 Figs. 1, 2. Leioceras uncinatum (S. Buckman) [m]. Scanning electron micrographs showing the semi- spiral ornament on an isolated fragment of the dorsal wrinkle-layer, removed at 2-67 mm diameter. 1 , a complete fragment of the layer, the venter being situated midway, running parallel to the upper edge. 2, an enlargement of part of the ornament. Specimen from the Scissum bed, Burton Cliff, Dorset. HU 121.J.3. 1 x60; 2x 115. Figs. 3, 4. Graphoceras impolita (S. Buckman) [M]. Dorsal wrinkle-layer surface ornament, at 3-36 mm diameter, showing a sub-radial pattern of truncated pustulae, enlarged in the scanning electron micrograph of fig. 3. Concavum Zone, Horn Park, Beaminster, Dorset. HU 121. J. 4. 3x110; 4x30. Fig. 5. Staufenia sinon (Bayle) [M], Dorsal wrinkle-layer ornament at 1-87 mm diameter. Scheffhau, Bonndorf, Schwabischen Alb, south-west Germany. HU 121. J. 5. xc. 25. Figs. 6, 7. Nautilus pompilius Linne i Palaeontology, Vol. 14 PLATE 17 CALLOMON, Macroceplialites Palaeontology, Vol. 14 PLATE 18 CALLOMON, Macro cep ha I i tes J. H. CALLOMON: MACROCEPHALITES 127 ( g ) Macrocephalites mantararanus Boehm 1912, p. 159, pi. xxxv, fig. 3 a, b (East Indies, Sula Islands). (h) Macrocephalites verus Buckman 1922, pis. cccxxxivA, b (Swabia). (/) Macrocephalites triangularis Spath 1928, p. 180, pi. xxi, fig. la, b (Cutch, India). O') Macrocephalites sakondriensis Basse and Perrodon 1951, p. 22, pi. i, fig. la, b (Madagascar). The fonnosus-madagascctriensis group seems very close, and where Spath referred to the former as ‘the Indian equivalent of M. macrocephalus’’ one could equally well call Zittel’s specimen the European equivalent of M.fonnosus. It is perhaps significant that M. formosus occurs in the lowest beds in Cutch. Inflated forms like the neotype of Schlotheim’s species have not been described from India or Madagascar, and until both the variability and stratigraphy of the group to which Zittel’s specimen belongs are better known and shown to be closely similar to those of M. formosus, it is perhaps best to continue to apply Indo-Malgach names to European forms with caution. Quenstedt’s name compressus was at least six times preoccupied and the alternative (Holder 1958) of ascribing the name to Blake ((e), 1905), is pre-empted in this case by H. Douville’s renaming Quenstedt’s species Amm. jacquoti in 1878, ( d ), a name rescued from the status of nomen oblitum by Arkell in 1954 (p. 117). (Dr. Wiedmann has kindly searched the collections at Tubingen and informs me that Quenstedt’s specimen of 1849 appears to be lost.) So the oldest independent valid name for European forms appears to be M. cannizzaroi (Gemmellaro) (c). However, if the figure is accurate, this may be an unusually small form, septate to only 72 mm with uncoiling of the umbilical seam starting at 90 mm, although it seems without doubt a macroconch. The name to be used for Zittel’s specimen depends therefore on the purpose to be achieved, and the view of specific variability an author is prepared to take. As member of a biospecies, it is probably a variant of M. macrocephalus (Schlotheim 1813). As member of a compressed conventional morphospecies, it can for general purposes of citation be ascribed to M. cannizzaroi (Gemmellaro 1870), but the closest match purely morphologically is with M. madagascariensis Lemoine 1911. Lastly this leaves entirely the question of which macroconch ‘species’ goes with which microconch, should it be desired to unite dimorphic pairs under the same specific name. The solution to this problem is still in a rudimentary stage. Macrocephalites tumidus (Reinecke 1818) Plate 18, figs. 2 a-c, 3a-c Nautilus tumidus Reinecke 1818, p. 74, figs. 47-48. Schlotheim, in his second work (1820), quoted Ammonites tumidus Reinecke in the synonymy of his Amm. macrocephalus. All authors in recent times are agreed that the two species are distinct, but the precise interpretation of Reinecke’s species has been almost as uncertain as that of Schlotheim’s. Systematic. Whereas we have Schlotheim’s original specimens but do not know pre- cisely from where they came, the origin of Reinecke’s material, which is apparently lost, is well known. Large numbers of topotypes from Upper Franconia are to be found in the collections. However, they consist almost exclusively of pyritized nuclei rarely more 128 PALAEONTOLOGY, VOLUME 14 than 50 mm in diameter, and even if one such specimen were chosen as neotype, the uncertainties would persist as precise taxonomy today depends heavily on the characters of the complete adult including the body-chamber. Examination of topotypes shows that they encompass a range of forms from com- pressed (thickness 50% of diameter) to extremely inflated (thickness 95%), finely to moderately coarsely ribbed. Two typical specimens intermediate in this range are figured here for convenience. Compared as a whole with Macrocephalites of the macro- cephalus-subcompressus group, they show consistent differences, however, in being more evolute (umbilicus 20-25%), having rounded umbilical walls to give elliptical whorl- sections, and strong primary ribbing which persists and descends into the umbilicus. To divide them into separate species would be quite artificial, and because of their incompleteness comparison with other species from elsewhere based on complete adults must always remain largely speculative. It is not even possible to diagnose their status as macro- or microconchs, and the Franconian specimens have thus been variously ascribed to subgenera Indocephalites (by Jeannet) or Pleurocepha/ites (by Spath and Arkell). Spath (1928, pp. 171, 185) concluded that the best match of the Franconian material is with Pleurocephalites folliformis Buckman, of which he figured a nucleus (pi. xxxvi, fig. 6a, b ), and spp. from the Kellaways Clay, lower Calloviense Zone, of Wiltshire. The best solution to the problem will be to stabilize this interpretation by finding a topotype from Uetzing with some body-chamber resembling the English forms as closely as possible, taking it to pieces to show inner whorls resembling Reinecke’s figure as closely as possible, and making it neotype. Synonymy. Even though consisting only of nuclei, the Franconian forms themselves have been described under several names. (In the following list the figures at the end in brackets give the maximum diameter of the nucleus and its whorl-thickness in per cent respectively). (a) M. tumidus (Reinecke 1818) „ „ Kuhn 1939, pi. iii, fig. 12 „ „ here, pi. 18, fig. 3a-c „ „ „ pi. 18, fig. 2a-c 1(b) M. platystonms (Reinecke 1818) „ „ Jeannet 1955, pi. xxii, fig. 5 M. aff. platystonms Spath 1928, pi. xxxvi, fig. 4 pi. xxxvii, fig. 10 (c) M. perseverans (Model MS.) Kuhn 1939, pi. iii, fig. 7a, b „ „ (Model MS.) Jeannet 1955, pi. xxv, fig. 4 (lectotype) (d) M. sphaericus (Greif MS.) Jeannet 1955, pi. xiv, fig. 2 (holotype) „ „ „ „ „ „ pk xvii, fig. 5 (e) M. franconicus (Rollier MS.) Jeannet 1955, pi. xiv, figs. 3, 4 (syntypes) (/) M. intermedius (Greif MS.) Jeannet 1955, pi. xxv, figs. 1, 2 (holotype) M. pila Jeannet 1955 (non Nikitin), pi. xx, fig. 5 M. herveyi Kuhn 1939 (non Sowerby), pi. iii, fig. 4, 4a (32: 74) (37: 76) (29: 75) (43: 79) (23: 80) (32: 87) (50: 87) (41: 95) (39: 95) (19: 70) (51: 57) (31: 76) (49: 71) The interpretation of Nautilus platystomus Reinecke is in doubt for the same reasons as that of M. tumidus. Most authors have considered it to be an inflated Macrocephalites of the tumidus group, although the possibility cannot be ruled out that it may have been a Kheraiceras. The name M. perseverans appears to have been coined by Model, but first validly published by Kuhn. Fie designated no type and the text makes it clear that there were several specimens. The type series therefore presumably included all speci- J. H. CALLOMON: MACRO CEP HALITES 129 mens thus labelled by Model. Another of these was figured by Jeannet labelled ‘Holo- typus’, apparently unaware of Kuhn’s publication. Jeannet’s 1955 specimen is thus lectotype of Kuhn's 1939 species. It is difficult to see any significant differences between M. sphaericus Jeannet and M. perseverans Kuhn as defined by the types, although other specimens attributed to these species by Jeannet may well be distinct. Other names of species from elsewhere that may be synonymous are numerous. They include Ammonites macrocephalus rotundas Quenstedt 1849, but rotundas is preoccupied almost as often as compressus ; and the three species ascribed to the genus P/atvsto- maceras by Corroy (1932). Stratigraphical horizon. The stratigraphy of the region around Uetzing and Staffelberg in northern Franconia is well summarized by Arkell (1956, p. 118). The ‘Goldschnecken’ all come from the Uetzinger-Schichten, pyritic Oxford Clay, resting on a basal marly ironshot Macrocephalus-bed with phosphatized ammonites. The Goldschnecken include the supporting fauna of the Calloviense and Jason Zones, including Siga/oceras eno- datum, but further subzonal division of the beds appears to be not possible. The proximity of the thin clay outcrop to that of the thick overlying White Jura has to be borne in mind: it may have disturbed and attenuated the clays by cambering. The specimens of M. tumidus could therefore come from a level as low as, but not lower than, the Koenigi Subzone of the Calloviense Zone, which yields Pleurocephalites in England; or as high as the Enodatum Subzone, which yielded the forms at Herznach in Aargau that Jeannet compared with them. They need not therefore be all strictly of the same age. Acknowledgements. I thank Drs. H. Jaeger, Berlin, and W. Barthel, Munich, for the loan of speci- mens in their care, and Drs. A. Zeiss, Erlangen, and M. K. Howarth, London, for a number of helpful discussions. REFERENCES ammon, L. von, 1875. Die Jura-Ablagerungen zwischen Regensburg und Passau. Abh. zool.-min. Ver. Regensburg, 10, 1-200, pis. 1-4. anon, 1832. Systematisches Verzeichniss der Petrefacten-Sammlung des verstorbenen wirklichen Geheim- Raths Freiherrn von Schlotheim. Gotha. arkell, w. J. 1933. The Jurassic System in Great Britain, Oxford. 1951. Proposed designation, under the plenary powers, of the type species of the genus ‘Macro- cephalites’ Zittel, 1884, and of the type specimen of ‘Ammonites macrocephalus’ Schlotheim, 1813 (Class Cephalopoda, order Ammonoidea). Bull. Zool. Nomencl. 2, 170-2. 1954. Three complete sections of the Cornbrash. Proc. Geol. Assoc. 65, 115-20. 1956. Jurassic geology of the world. Edinburgh and London: Oliver & Boyd. • 1957. In Treatise on Invertebrate Paleontology , moore, r. c. (ed.). Part L. Mollusca 6: Cephalopoda, Ammonoidea. Univ. of Kansas Press. baier, f. j. 1757. Joannis Jacobi Baieri Monumenta Rerum Petrificatarum Praecipia Orictographiae Noricae. Nuremburg. basse, e. and perrodon, m. 1951. Macrocephalitides du sud-ouest de Madagascar. Mem. Soc. geol. France, mem. 65, 1-100, pis. 1-6. BLAKE, J. f. 1905. A monograph of the fauna of the Cornbrash. Mem. Palaeontogr. Soc. London. Part I, 1-100, pis. 1-9. boehm, G. 1912. Beitrage zur Geologie von Niederlandish-Indien. 1. Abteilung. Die Sudkiisten der Sula-Inseln Taliabu und Mangoli. 4. Abschnitt. Unteres Callovien. Palaeontograpliica, Suppl.-Bd. 4, no. 4, 121-79, pis. 32-44. buckman, s. s. 1922. Type ammonites, vol. iv. London. K C 7895 130 PALAEONTOLOGY, VOLUME 14 callomon, j. h. 1959. The Ammonite Zones of the Middle Jurassic Beds of East Greenland. Geol. Mag. 96, 503-13, pis. 17, 18. 1964. Notes on the Callovian and Oxfordian Stages. Compt. rend. Colloque Jurassique, Luxem- bourg 1962. Mem. Inst, grand-ducal. Sect. Sci. nat. phys. math. 269-91. Luxembourg. corroy, G. 1932. Le Callovien de la bordure orientale du Bassin de Paris. Mem. Carte geol. France, 1-337, pis. 1-29. dorn, p. 1939. Stratigraphisch-palaogeographische Untersuchungen im mittleren and oberen Dogger der Frankenalb. Neues Jb. Min. etc., Beil.-Bd. 82B, 161-314. douglas, J. a. and arkell, w. j. 1928. The stratigraphical distribution of the Cornbrash. I. The South-Western area. Quart. J. Geol. Soc. Loud. 84, 117-78, pis. 9-12. douville, h. 1878. Note sur le bathonien des environs de Toul et de Neufchateau. Bull. Soc. geol. France (3), 6, 568-77. gemmellaro, g. g. 1870. Studi paleontologici sulla fauna del calcare a Terebratula janitor del nord di Sicilia. Parte I. 1-56, pis. 1-12. Palermo. (Also published in part in Giorn. Sci. nat. econ. Palermo, 6, 237-52, 1870.) gerstlauer, g. 1940. Geologische Untersuchungen im Ries. Das Gebiet des Blattes Ottingen. Mitt. Reichsstelle f. Bodenforsch., Zweigst. Miinchen, Hft. 35, 1-71, map. holder, h. 1958. Vorschlage fur die Behandlung von F. A. Quenstedt’s Nomenclatur. Paldont. Z. 32, 18-23. International code of zoological nomenclature, 2nd edn., 1964. Int. Trust. Zool. Nomencl., London. jeannet, a. 1955. Die Macrocephaliten des Callovien von Herznach (Aargau). Eclog. geol. Helv. 47, 223-67, pis. 13-27. kuhn, o. 1939. Die Ammoniten des frankischen Calloviums. Nova Acta Leopoldina, n.f. 6, 451-532, pis. 1 (48)— 1 0(57). lemoine, p. 1910-11. Ammonites du jurassique superieur du cercle d’Analalava (Madagascar). Ann. Paleont. 5, 137-68 (1-32), pis. 16-21 (1-5), 1910; 6, 45-64 (33-52), pis. 6-8 (6-8), 1911. oppel, a. 1857. Die Juraformation Englands, Frankreichs und des siidwestlichen Deutschlands. Lief. 6-9, 439-694. Stuttgart. quenstedt, f. a. 1849. Petrefactenkunde Deutschlands. Bd. I, Cephalopoden. Lief. 2, 105-84 (1846); Atlas zu den Cephalopoden (1849). Tubingen. 1886-8. Die Ammoniten des schwabischen Jura. 2. Band. Der Braune Jura. Lief. 13, 609-72, pis. 73-79 (1886); 3. Band. Der Weisse Jura. Lief. 20-21, 1017-1140, pis. 116-26 (1888). reinecke, J. c. M. 1818. Maris protogaei Nautilos et Argonautas vulgo Cornua Ammonis in Agro Co- burgico et vicino reperiundos. Coburg. schlotheim, e. f. von, 1813. Beit rage zur Naturgeschichte der Versteinerungen in geognostischer Hinsicht. In Leonhard, C. G.: Taschenbuch fur die gesamte Mineralogie, 7, 3. 1820. Die Petrefactenkunde auf ihrem jetzigen Standpunkte durch die Beschreibung einer Sammlung versteinerte und fossiler Uberreste des Thier- und Pflanzenreichs der Vorwelt erlautert. Gotha. sowerby, J. de c. 1840. Appendix to Grant: Memoir to Illustrate a Geological Map of Kutch. Trans. Geol. Soc. London (2), 5, 327-9, pis. 21-23. spath, l. f. 1928. Revision of the Jurassic Cephalopod Fauna of Kachh (Cutch). Palaeont. Indica, N.s. 9, Mem. 2, parts II, III, 73-278, pis. 8^-7. zittel, K. A. 1884. Hanclbuch der Palaeontologie. I. Abt. Palaeozoologie. 2. Band. Mollusca und Arthropoda. Miinchen and Leipzig. J. H. CALLOMON Department of Chemistry University College London Gower Street, London, W.C. 1 Final typescript received 28 June 1970 A PROBLEM OF FAUNAL REPLACEMENT ON PERMO-TRIASSIC CONTINENTS by PAMELA LAMPLUGH ROBINSON Twelfth Annual Address, delivered 5 March 1969 Abstract. The faunal replacement of the mammal-like reptiles or theropsids by the non-mammal -like reptiles or sauropsids (archosaurs and lepidosaurs) during Triassic times, is discussed. The basic physiological characters of the modern descendants of these two reptilian groups are reviewed and contrasted. It is now known that these characters have considerable, and differing, adaptive properties and affect the broad distribution of each of the two groups in the general environments of the modern world. The environments of the Upper Permian, the time when the theropsid reptiles were at their peak in importance, are contrasted with those of the Upper Triassic, when the sauropsids had largely replaced the theropsids. It is shown that there is a correlation between the number of genera representing theropsids and sauropsids, and relative abundance of certain types of environments in the Upper Triassic and Upper Permian. It is suggested that the correlative link is to be sought in certain basic physiological characters which distinguish the theropsids from the sauropsids, and affect the ease with which they adapt to certain environments. Palaeomagnetic evidence for successive geological periods shows that most of the world’s continents have tended to migrate northward across the parallels of latitude, as well as drifting apart. The relative size of land- masses, and the changing incidence of latitudes on these, have progressively changed the abundance of certain types of environment, as reflected by rock-type, in successive geological periods, offering opportunities for deployment, through their basic physiological characters, of first one major group of tetrapods, and then another. ‘Problems of Triassic Vertebrates’, a title suggested by the Council for this Address, is tactfully broad and generous in scope. So broad that choice is difficult, and prompts one to think about kinds of problems of Triassic vertebrates, as a preliminary, and an aid, in making a choice of a problem for discussion. The first array of problems, which come to mind, are those connected with the evolutionary events of the Period, and of the preceding Permian Period. For during these two Periods reptiles became the dominant members of the land faunas of the world, and underwent a major adaptive radiation, producing the stocks from which the mammals and birds were derived (text-fig. 1). During the Permian the mammal-like reptiles became numerous and varied, and by the end of the Triassic some had pro- gressed through all the major evolutionary changes which culminated in mammalian structure. The two most important groups of non-mammal-like (or sauropsid) reptiles, the subclasses Archosauria and Lepidosauria, originated late in the Permian, and had their first major radiation during the Triassic. The Triassic Archosauria include certain kinds of reptiles, of the order Thecodontia, which were restricted to the Period, and which represent an early adaptive radiation of archosaurs. But, in addition to the Thecodontia, Triassic Archosauria include the earliest crocodiles, and also the first members of the two orders of dinosaurs, Saurischia and Ornithischia, which were to be the most prominent, varied, and numerous members of the world’s land faunas for the whole of the rest of the Mesozoic, a time interval of more than 100 million years. From some stock of ornithischians the birds were derived during Jurassic times. The Lepidosauria, originating in the late Permian as a small and inconspicuous order of [PalaeontoJogy, Vol. 14, Part 1, 1971, pp. 131-53.] 132 PALAEONTOLOGY, VOLUME 14 'SAUROPSIDS' j 'THEROPSIDS' text-fig. 1. A ‘family tree’ showing the general relationships of those reptiles, and their descendants, which are here termed ‘theropsids’ and ‘sauropsids’. reptiles, the Eosuchia, were also represented, in the Triassic, by two orders of reptiles still in existence today, the beak-headed Rhynchocephalia, and the earliest lizards (Squamata). The snakes (Squamata) evolved later, from some stock of lizards at present unknown, and are first found in the Cretaceous. Apart from the snakes, all the main kinds of non-aerial terrestrial reptiles had appeared by the end of the Triassic, and so had the earliest mammals. There are so many fascinating problems connected with the evolution, relationships, and structural adaptations of Triassic reptiles, that it would seem that one need look no further for a subject for discussion, indeed choice of subject already presents for- midable difficulties. Yet these problems are basically similar to most of those posed by P. L. ROBINSON: TRIASSIC CONTINENTAL FAUNAS 133 vertebrates of any geological period from the Ordovician onwards. Their importance depends on their setting within the general framework of ideas which were first formu- lated in the nineteenth century, ideas concerning the evolution of animals and plants, and which were capable of demonstration from the fossil record. And the demonstration and solution of problems in the evolution of vertebrates has depended on a methodology, comparative anatomy, and embryology, which, though having its beginnings in classical times, was elaborated chiefly in the late eighteenth and nineteenth centuries. A second set of problems concerns the use of vertebrate fossils in the stratigraphy of the continental facies of the Triassic. These problems are becoming increasingly important in the Gondwanaland continents, and in parts of Laurasia, such as China, the U.S.S.R., and North America. But, although the types of fossils used may be unfamiliar, Triassic vertebrates are sometimes abundant enough to allow subdivisions of the Triassic rock sequence and to provide the means of mapping formations across country; the type of stratigraphic problem is familiar, and the geological principles involved are well established. There are two other kinds of problems which are well illustrated by Triassic verte- brates. One concerns their distribution in space, their geographical distribution during the Triassic. This kind of problem can be linked with geological topics of current interest, such as continental drift. The second kind of problem is concerned with the distribution of vertebrates in time, with changes or replacements of faunas. Vertebrate faunal replacement occurred in the sequence of faunas of several of the geological systems, and is little understood. The faunal replacement illustrated by the sequence of Permian and Triassic vertebrate faunas is particularly striking, and affected stocks of major evolutionary importance. Because no satisfactory explanation of it has so far been offered, and even the methodology for doing so is not immediately apparent, this problem presents a special challenge. It will first be described, and then discussed, as the subject of this Address. THE RISE AND DECLINE OF THE MAMMAL-LIKE REPTILES The degree to which certain lithologies become abundant only in certain geological systems almost causes one to lose faith in the principle of uniformitarianism. The Triassic, more than most geological systems, contains abundant continental sediments which are widely distributed in both hemispheres of the world, and the Permian System runs the Triassic a close second in this respect. So there is an excellent record of terrestrial vertebrates, particularly of reptiles, in the rocks of the Triassic and Permian, and this allows recognition of a problem of faunal change. To appreciate this problem it is convenient to consider Triassic reptiles in two main groups or taxa. The mammal-like reptiles can be grouped as a taxon of ‘theropsids’. The two important subclasses of non-mammal-like reptiles, the Archosauria and Lepidosauria, may be considered together as a second taxon, the ‘sauropsids’ (text- fig. 1). If one compares the number of genera of each taxon which have been discovered in the three main subdivisions of the Permian, and those of the Triassic, a remarkable contrast becomes evident (text-fig. 2). The theropsids, which first appeared in the late Carboniferous, became more abundant in number of genera during the Permian, 134 PALAEONTOLOGY, VOLUME 14 reaching their acme during the Upper Permian; thereafter they dwindled rapidly until they had become relatively rare in the Upper Triassic. The sauropsids first appeared in the Upper Permian, and in the Middle and Upper Triassic increased rapidly in number of genera, precisely at the time when the number of theropsid genera was declining. THEROPSIDS SAUROPSIDS Upper Triassic Middle Triassic Lower Triassic Upper Permian Middle Permian Lower Permian (Pennsylvanian) text-fig. 2. Numbers of genera of theropsids and sauropsids found in the subdivisions of the Permian and Triassic Systems. (Source: Romer 1966.) There is no doubt that some bias is introduced into this picture by accidents of collect- ing. To be aware of this one need only compare the total number of genera of both taxa from the Lower Triassic with the total from the Upper Triassic. But that this bias does not obscure or falsify the main peculiarity of the distribution of genera can be seen by comparing the total of both taxa for the Upper Permian with the total for the Upper Triassic. The totals are large in each System subdivision, yet the relative im- portance of the two major taxa of reptiles has been completely reversed by Upper Triassic times. In the Upper Permian the theropsids are the abundant members of the world’s terrestrial faunas, but by Upper Triassic times the theropsids are relatively rare and the sauropsids have become dominant. The advanced theropsids, or early mammals, continued to be rare until the beginning of the Tertiary. The methodology for tackling this problem is not readily apparent. If it were the case, for example, that the carnivorous theropsids of the Permian were replaced by carni- vorous sauropsids during the Triassic one could turn to the methods of comparative anatomy in an attempt to discover those ways in which the sauropsids were superior, structurally, for a carnivorous role in Upper Triassic times. But during the Upper Permian the theropsids were filling all the usual roles of omnivore, carnivore, and herbivore, while by Upper Triassic times these roles were being filled by sauropsids. Moreover by Upper Triassic times the theropsids were, in structure, at their most advanced from the evolutionary point of view, being close to, or having just attained, mammalian status. Nor is it easy to invoke some peculiarity of geographical or facies P. L. ROBINSON: TRIASSIC CONTINENTAL FAUNAS 135 distribution to explain the problem. Excellent faunas of Upper Permian theropsids are known from localities as far apart as the U.S.S.R. and South Africa, while Upper Triassic sauropsid faunas are known from nearly all the world’s continents. The faunas of reptiles of both taxa come chiefly from flood-plain, lacustrine, and deltaic sediments, the fluviatile facies of the Permian and Triassic. When there is no established methodology for tackling a problem, it remains simply to wait, until clues emerge which provide an insight into some of the factors responsible, and allow suggestions to be made about possible causes. While it is certain that no one factor can alone have been responsible for the sweeping faunal change which occurred during Triassic times, some clues have presented themselves which seem to indicate some of the possible factors and causes, and these clues will now be reviewed in the order in which they emerged. A COMPARISON OF TWO FISSURE FAUNAS FROM BRITAIN The first clue to the problem emerges when one compares two faunas of a rather special kind which are found in Britain in some of the counties round the Bristol Channel. These are faunas obtained from fissures but it is not yet generally recognized that there are really two such faunas, distinct in age, in faunal composition, and in environmental background. The earlier of the two faunas is Upper Norian in age (Robinson 1957). At this time Britain still formed part of a North Atlantic continent, lying to the north of the Tethyan sea, and in western Britain some of the Hercynian fold- structures still projected above the adjacent lowlands as hilly regions. The hills were mainly built of Carboniferous Limestone, and their drainage was mostly underground, by systems of caverns and passages developed along joints and bedding planes by solution of the limestone. Some of the caverns were extensive, about 50 ft across, and they gradually silted up as the watertable rose in the region towards the end of Norian times, just prior to the invasion of the area by the Rhaetic seas. By Upper Triassic times the hill regions were semi-arid, and were gradually being buried in their own waste, an insolation scree of angular or sub-angular limestone debris. Vegetation cover was poor, and evaporite deposits were forming in the adjacent lowlands. The fissure sediments were swept into the underground watercourses by intermittent and rather violent rain- storms, which scoured debris from a wide area of hill-surface and sent much of it down the drain of the nearest watercourse system. This sometimes effected a rather impressive concentration of animal bones, for the fauna preserved in the Upper Norian fissure fillings consists, not of cave-dwellers, but of vertebrates living on the hill-surface near to the entrance of the watercourse. The fauna thus consists of hill-dwellers, rather than lowland forms, and its members are moderate to small in size. The composition of the fauna is interesting; there are no amphibians, no semi-aquatic reptiles, and no therop- sids; the fauna consists entirely of sauropsid reptiles and one small cotylosaur (procolo- phonid). The absence of theropsids is real, for in the tons of Upper Norian fissure sediments which have been examined under a binocular microscope to date, not even a single tooth of a theropsid has ever been found. The second fissure fauna is probably mainly Liassic in age. All the fissure localities of this age are found on the small islands which remained above water after the invasion of Britain by the Rhaeto-Liassic seas, and are well exemplified by the Glamorgan area 136 PALAEONTOLOGY, VOLUME 14 (text-fig. 3). The fauna is found in sediments which usually occur in rather narrow slot- like fissures. These slots represent an immature system of solution phenomena which began to develop in the joints and bedding planes of those small areas of Carboniferous Limestone which still remained above water after the Rhaetic marine invasion had drowned the older landscape and its drainage system. The Welsh islands were sub- merged later in the Liassic, before most of their drainage solution channels could attain North Cornelly NO Nottage LIAS oLaleston NORMAL "V COVER ; '■•••• '?ew£l; ’ > - ISLAHq: ! NORMAL Wel5h Lias , j>£t.Dorat'5 NORMAL LIAS 4 a N.DS: j & Bonvilston NORMAL LIAS 1 FORMAL L/AS THE ST. BRIDE'S ISLAND Submerged during bucklandi times Possible outline of island at the end of angulata times. : ' -;3 Existing outcrops of on-shore deposits (Sutton store facies) of angulata age. Approximate sea-ward limit of on-shore deposits (Sutton stone) of angulata age. THE COWBRIDGE ISLANDS Submerged at the end of planorbis times Possible outline of island towards the end of planorbis times. [H Existing outcrops of on-shore deposits (Sutton stone facies) of planorbis age. Approximate seo-ward limit of on-shone .deposits (Sutton stone) of planorbis age. | Slot fissures A Underground water- course fissures text-fig. 3. The Liassic palaeogeography of Glamorgan showing the sites of the fissures. The ‘underground watercourse’ fissures marked by triangles are those mature and cavernous types of late Norian age, and demonstrably covered by the seas of Lower Liassic times (normal Lias). The ‘slot fissures’ are an immature system of underground watercourses, all of which occur on the St. Bride’s Island, which was not submerged until bucklandi times (Lower Lias). The Cowbridge Islands were submerged a little earlier in the Lower Liassic than that of St. Bride’s. the maturity and size of the older Triassic system. Just before submergence sedimenta- tion, rather than solution, became the dominant process in these fissures. The sediments are sometimes red, but often green, yellow, or dark grey, and they often contain very abundant plant remains. During Liassic times it is probable that these small Glamorgan islands lay at about 15° of latitude, as do the Lesser Antilles and the Marianas today. Their climate was evidently more equable, and with a better rainfall and more abundant vegetation, than the conditions found over the late Norian landscape. The Liassic fissure fauna consists of sauropsids, probably mainly small lizards, but also of therop- sids, of several kinds, and well represented by abundant bones, teeth, and jaws. Probably these theropsids, or their ancestors, dwelt along the north shores of European Tethys during the Upper Triassic and were driven northward by the advance of the Rhaetic seas to become marooned on the Liassic islands of Britain. P. L. ROBINSON: TRIASSIC CONTINENTAL FAUNAS 137 The first clue is thus a contrast in faunas, and of the environments in which they lived. The theropsids are found only in the more genial environment of the small islands of the early Liassic, they are not found in the more stringent environment which existed in late Norian times in the same area, when it was an interior continental region. BASIC PHYSIOLOGY AND ADAPTATION TO ENVIRONMENT A second clue to the problem of early Mesozoic faunal replacement can be found by considering certain physiological characters of the living descendants of the Upper Triassic theropsids and sauropsids. These living descendants are separated by a very long time interval from their forebears of the late Palaeozoic and early Mesozoic, and table 1. Comparison of metabolic rates Ccillkg/24 h Caljm2l24 lx Rattlesnake (ectotherm) 7-7 91 Rabbit (endotherm) 44-8 619 Woodchuck (endotherm — can hibernate) 28-7 418 so it may be thought that physiological characters can hardly have any bearing on a problem so remote in time from the present. However, as will be shown, in certain basic features the physiology of the descendants of these two taxa differ markedly from one another, and within each taxon these features are common to all or nearly all. These differences must therefore have arisen at an early date, and each taxon thereafter have pursued a separate path in physiological evolution and adaptation. The modern descendants of the theropsids are, of course, the mammals ; those of the sauropsids are, chiefly, the lizards and snakes on the one hand, and the birds on the other. The croco- dilians have been semi-aquatic in habits since Lower Jurassic times, and this has had very considerable effects on their physiology. They can no longer be regarded as truly terrestrial vertebrates physiologically, and will not be considered in this general review. Lizards and snakes (Squamata) are represented today by about 6000 species; they are the typical sauropsids or ‘reptiles’ of the present scene. They are not very closely related in ancestry to birds, for birds are descendants of the archosaurian sauropsids, while the modern Squamata are descended from lepidosaurian sauropsids. Yet some of the basic physiological characters of birds are so similar to those of squamates that physi- ologists, comparing the two groups, tend to refer to birds as ‘feathered reptiles’. For present purposes therefore birds may be regarded as ‘sauropsids’. The first important generalization, which is basic to an understanding of the physio- logical adaptations of mammals, birds and reptiles, is that mammals and birds have a much higher basal metabolic rate (B.M.R.) than do reptiles of the same weight and active at similar temperatures. Some early figures by Benedict (quoted in Prosser and Brown 1961) still illustrate this sufficiently well by comparing a reptile, a non-hibernat- ing mammal (rabbit) and a mammal capable of hibernation (woodchuck), each 2-5 kg in weight and with body temperatures of 37 °C (Table 1). There are advantages and disadvantages biologically in maintaining relatively high metabolic rates. Disadvantages are that these animals must eat more frequently par- ticularly if they are relatively small, i.e. with a large body surface relative to body weight. 138 PALAEONTOLOGY, VOLUME 14 The heightened metabolism puts more ‘pressure’ on many organs of the body such as the excretory organs, especially the kidneys. The increase in excretory activity is, at least potentially, expensive in terms of the animal’s water economy. Squamates and birds excrete waste nitrogen from protein metabolism as uric acid; mammals excrete it as urea, a basic difference between living theropsids and sauropsids. Urea is soluble, and requires much more water for its excretion than uric acid. However, mammals have evolved a special segment of the tubule of the kidney, the loop of Henle, which reabsorbs much of the water required for pressure filtration of the urea from the blood capillaries through the kidney capsule and into the kidney tubule. The evolution of this loop has allowed mammals to conserve much of the body water which would otherwise be ex- pended in urea excretion. Even at their most efficient, however, mammals cannot rival birds in economy of excretory water. Molecule for molecule, twice as much nitrogen can be excreted in the form of uric acid as compared with urea, and even the most economic mammalian excretion expends more than ten times as much water in getting rid of urea wastes, compared with uric acid excretion in birds (Dawson and Bartholomew 1968). Uric acid, a relatively insoluble substance, thus provides the most effective means of disposing of waste nitrogen when water conservation is important, and is the method used by the living sauropsids, birds, and squamates. Advantages of a high basal metabolic rate include the possibility of maintaining a relatively high and constant internal body temperature, i.e. the condition known as endothermy. This allows the body’s biochemical reactions to be run at optimum and relatively constant rates. The relatively constant and highly efficient inner environment permits the development of a large brain and well-co-ordinated nervous and sensory system, introducing learning and choice as important adaptational mechanisms, well shown in a great variety of ways by the endothermic mammals and birds. The mechanisms for regulating body temperature are similar in birds and mammals, even though they must have evolved independently in the two groups. These mechan- isms are controlled augmentation of body heat, as required, by increasing metabolic rate, and control of heat loss, as required, by varying the conductance of the body. Control of heat loss, in both birds and mammals, depends on having an outer body layer and covering whose conductance and insulation properties can be varied, and on being able to transfer unwanted body heat into a capacious heat sink, namely, an environ- ment which is at a temperature significantly below that of the body core. The range of body core temperatures shown by mammals and birds may therefore affect their capacity to use the environment as a heat sink, or to insulate themselves from its cooling effects. The normal range of preferred, or eccritic body temperature for the major taxa of living tetrapods is given in Table 2 below, though mammals capable of hibernation have been omitted, as they are often not fully endothermic. Evidently body core temperatures of mammals are significantly below those of birds. This means that in the hotter environments of the world mammals adapt with greater difficulty. Ambient temperatures may more readily rise above body core temperatures so that heat tends more continually to flow the wrong way, into the body, and unwanted heat can be got rid of only by evaporating water (panting or sweating). This is an ‘expensive’ method of keeping cool, except as a temporary measure, in hot climates where water may be short. Just how expensive it may be can be gauged from human performance; for men doing hard physical work in saturated atmospheres at 35-5 °C P. L. ROBINSON: TRIASSIC CONTINENTAL FAUNAS 139 sweat at rates up to 4-2 litres per hour, yet the total volume of water in a man’s blood is about 4 litres (Gordon 1968). Of course some modern mammals have adapted to hot arid conditions, some desert rodents do not sweat, have evolved methods of reducing respiratory water loss, and can live without drinking water. But of those mammals which have adapted to desert life many (though not all) have done so by the ‘artful dodger’ method, as far as temperature regulation is concerned. They spend the day in burrows dug down to the cooler and moister substratum and emerge in the evening to feed. (Sources: Bartholomew 1968, Bartholomew and Dawson 1968, Dawson and Bartholomew 1968, Mayhew 1968.) Though the rather low body core temperatures of mammals mean that, generally speaking, they adapt with difficulty to the hotter environments, they adapt rather more easily to the colder climates than do birds, with their higher core temperatures. The fact that the difference between core and ambient temperatures is smaller in mammals means that less metabolic work, and less food, is necessary to maintain core temperatures. In cold climates, too, control of heat loss requires only the intensification of the mechan- isms already evolved to regulate conductance by the outer shell of the body and its covering. The modern sauropsid reptiles, lizards and snakes, are ectotherms. They derive from the sun, directly or indirectly, most of the heat required to maintain the body tempera- ture at which they perform their daily activities. While active they may maintain a remarkably constant body core temperature, and do so chiefly by a pattern of behaviour. They gain body heat, when required, by basking either in the sun or in a warm part of their environment. They lose body heat when necessary, by running to the nearest local heat sink — a patch of shade, a crevice, or a burrow. Control of body posture, of heart- beat rate, panting, and exploitation of the degree of thermal variety of the environment, are used as aids in maintaining body temperatures at the preferred level, and for damp- ing the oscillations of body temperature which would result from a simple on-off use of heater and heat sink in the environment. When inactive, the body temperature of most lizards and snakes drops to a level close to that of the ambient temperature. Ectothermy has its disadvantages, for the inner environment is optimum only when the animal is active. It also has its advantages, for the animal needs much less food than an endotherm to maintain itself. It has been calculated that, if there were a lizard as large as a man, the man would require about forty times as much food as the lizard just to maintain basal metabolic rate. As Bartholomew (1968) has remarked, though endotherms are more independent of environmental temperature than are ectotherms, they pay a high price table 2. Temperature data on modern tetrapods Taxon Normal range of eccritic body Highest tolerated body temperature (°C) temperature (°C) amphibia (terrestrial) SQUAMATA BIRDS mammals (endotherms only) 0-35 37-6 ( Microhyla olivacea ) 18-44 47-0 ( Dipsosaurus dorsalis ) 39-43 45 0 (birds of several orders) 35-39 140 PALAEONTOLOGY, VOLUME 14 for this independence in terms of metabolic cost of living, for about 80-90% of their oxidative energy is used to maintain thermal homaeostasis. Modern lizards and snakes show a wide range of preferred or eccritic body tempera- tures (Table 2), and some show astonishingly high values which would be lethal to any mammal, and are close to the values at which proteins and enzymes are denatured. Modern squamates are uricotelic, and this, and the methods of body temperature main- tenance and regulation, means that they adapt well to the hot arid climates, but cannot adapt to the frigid environments. table 3. Some physiological characters of ‘theropsids’ (mammals) and ‘sauropsids’ (birds and squamates) Uricotelic Ureotelic BIRDS SQUAMATES Higher eccritic temperatures MAMMALS Lower eccritic temperatures Higher B.M.R.s, typically endothermic, larger brains. Lower B.M.R.s, typically ectothermic, smaller brains. The basic differences in certain physiological characters of mammals, birds, and squamates are shown in Table 3 above. Mammals and birds have independently evolved endothermy, which gives them some independence from environmental temperatures, a relatively constant and optimum inner environment and hence better sensory and central nervous systems. Mammals and sauropsids differ from one another in two respects ; mammals are ureotelic whereas sauropsids are uricotelic, and sauropsids have achieved higher values of eccritic temperatures than mammals. The adaptive value of these basic physiological characters of mammals, birds, and squamates is well shown by their relative numbers in the more extreme environments, deserts on the one hand and frigid climates on the other (text-fig. 4). Squamates, particularly lizards, are the Distribution of tetrapods in certain environments Present Day AMPHIBIA SAUROPSIDS BIRDS MAMMALS And and semi- ari d Monsoon and savanna Moist warm equable Warm temperate Cool te mperate Arctic — Upper Triassic AMPHIBIA SAUROPSIDS THEROPSIDS Arid and se mi - arid Monsoon and savanna Moist warm equable — — - text-fig. 4. The distribution of tetrapods in certain environments at the present day, and in the Upper Triassic. P. L. ROBINSON: TRIASSIC CONTINENTAL FAUNAS 141 most numerous, in species and individuals, of the inhabitants of deserts, with birds next most numerous, and then mammals. Mammals have adapted best to the cold climates, some birds have done so, but squamates are absent. ENVIRONMENTS OF THE PERMO-TRI ASSIC It is highly unlikely that theropsids were endothermic in Permo-Triassic times. As will be mentioned later, it is probable that this physiological character evolved in late Mesozoic and early Tertiary times, for it was during the early Tertiary that a general enlargement of the brain occurred in the evolution of many mammalian stocks. Birds also probably evolved endothermy in post-Jurassic times for the three known specimens of Upper Jurassic birds show that at this time birds had relatively small brains and were gliding fliers incapable of flapping flight. The theropsids and sauropsids of the Permo- Triassic were probably all ectothermic. The differences between modern theropsids and sauropsids in certain physiological characters, such as method of nitrogen excretion, and the upper range of preferred body core temperatures, are distinctive for all the modern members of the two taxa as defined and discussed here. So it seems probable that these features evolved early in the history of the two taxa, and must be regarded as basic physiological characters which have dis- tinguished each taxon for a long time. These characters are sufficiently different in their adaptive properties to suggest that they may have evolved against rather different environmental backgrounds and perhaps at rather different times in the history of the two taxa. Does this throw any light on the problem of the faunal replacement of theropsids and sauropsids during the Triassic? Is it possible to suggest that at the beginning of the Triassic, a stock of early sauropsids, living in the varied and often more difficult environ- ment of hill ranges, with a patchy water supply, greater exposure to sun, and greater scarcity of food, evolved the basic physiological adaptations which have characterized them ever since? That, armed with these new adaptations, they gradually invaded the lowland regions (from which come the greater part of the continental fossil record), where they had a selective advantage over the theropsids, whose physiological adapta- tions were, at that time, much poorer. This suggestion may contain some truth, but it is much too crude. It is as though one imagined the sauropsids descending from their Triassic hills inspired by some ruthless policy which spelt extinction for theropsids. But the Triassic theropsids were not ‘second-class citizens’. They had had an extraordinarily successful history during the Permian, and they were to achieve even more spectacular successes in the Tertiary. Bearing in mind the basic physiological differences between the modern representatives of the two taxa, one may examine the general environments of the world’s lands during the acme of each taxon, the Upper Triassic and the Upper Permian, to see whether this throws any further light on the problem. The maps for the Upper Triassic (text-fig. 5, p. 152) show the world’s continents reassembled in their pre-drift positions, on two equal area projections: the normal (and more familiar) Mollweide, and an oblique Mollweide which gives good representation of polar regions (see notes on projections given with the maps). Two supercontinents, a northern Laurasia and a southern Gondwanaland, are distinguishable, but are 142 PALAEONTOLOGY, VOLUME 14 connected together at their western ends, while diverging eastwards on either side of the Tethyan Gulf and Ocean. The idea for this assembly is from Tuzo Wilson (1963), who made it in the light of work done on the mid-oceanic ridges, and ideas regarding the significance of these ridges for the break-up of the fragments which now form the world’s continents. Wilson’s assembly has been modified here to include other lines of evidence on its character, such as that of Bullard et al. (1965) on the fit of the Trans- atlantic Continents, and palaeomagnetic evidence (especially Irving 1964). The re- assembly of the continents was carried out on a globe 19 inches in diameter, and though they are not shown on the maps because of the small scale on which these are reproduced, the continental shelves were allowed for and used in making the reconstruction. It was found that the reassembly given here for the Upper Triassic satisfied and fitted all the major lines of evidence used, and which are mentioned in the notes included with the captions for the maps. The distribution of certain kinds of Upper Triassic sediments have been roughly indicated; coals, red-beds (with a qualifying letter showing, where known, whether they are fluviatile, lacustrine, or deltaic), aeolian deposits (which some- times succeed red-beds) and the two localities at which palaeowind directions have been obtained from these deposits and evaporites (gypsum, anhydrite, and salts). It is assumed here that red-beds which are associated with fluviatile deposits often indicate heavy seasonal rainfall followed by a dry season (Van Houten 1961, 1964). The pre-drift assembly of the world’s continents has been projected in the latitude positions for the Upper Triassic, and this at once invites proper consideration of the climate of the time. To do this adequately, and discuss the effects of the supercontinents on such important features as the intertropical convergence, interior continental pres- sure centres, and the oceanic ‘horse latitude’ high pressure centres, is beyond the scope of the present study and must be considered in another paper. Only brief comments, in very general terms, can be made here. However, in considering the distribution of the warmer climates of Upper Triassic times the lack of polar ice-caps has to be borne in mind. In an ice-free world fairly hot climates would probably extend into quite high latitudes, up to about 50°, with temperate conditions at the poles. The Upper Triassic equator more or less bisects the Tethyan Gulf, and the two great supercontinents are disposed rather symmetrically on either side of it. This suggests the possibility of an interesting aspect of the general climate of Upper Triassic times, by analogy with the profound effects, on modern climates, of the enormous landmass of Eurasia. The influence of the Asiatic landmass in causing monsoon conditions is well- known, though the causes are not quite so simple as usually indicated in many text- books, which usually quote an explanation which really originated from Halley in 1686. But though surface air conditions are now known to be partly reinforced and partly modified by conditions aloft (Pedelaborde 1963), it remains a fact that the large Asiatic landmass profoundly affects the air at many levels, and during summer sucks in surface air from all sides. Wherever this summer air has travelled over warm seas it is drawn towards Asia as the rain-bearing winds of the summer monsoon. In winter the opposite surface conditions occur. The great cold of the central and northern parts of the Asiatic landmass builds up a surface high-pressure centre, which is reinforced above by ad- vectance of cold air from the Arctic. So surface winds blow outwards from Asia during winter, and are therefore dry. In many of the middle and lower latitude marginal regions of Asia, including much of Peninsular India, there is a dry season which may last for P. L. ROBINSON: TRIASSIC CONTINENTAL FAUNAS 143 six months or more with a rainfall of only a few per cent of the annual total, in strong seasonal contrast to the high rainfall of the summer months. It is not impossible that each of the two great supercontinents of Upper Triassic times may have created monsoon conditions, though the less frigid climates of the polar regions have to be borne in mind. Winds reaching the middle and lower latitude eastern portions of Laurasia and Gondwanaland, in their respective summer seasons, may well have brought monsoon-type seasonal rains to each of these areas, local topography permitting. From each supercontinent, in their respective winter seasons, winds may have blown outwards, and have brought a dry hot season to the marginal areas of middle and lower latitudes. The conditions in the central and western parts of these two great landmasses would be rather different from those in the east, generally rather drier because most summer-season winds would have travelled over landmasses. Even here, in the centre and west, some areas would receive rain through the presence of local areas of sea, as might parts of the western selvedge of the supercontinents through onshore winds (see palaeowind direction for western North America). These suggestions seem to be in accord with the general distribution of certain Upper Triassic lithologies which were entered on the maps (text-fig. 5) after the continents had been re-assembled on independent evidence. Evaporites occur chiefly in two climatic regions. They are found in the contemporary tropics, approximately between the Upper Triassic latitudes of 25° N. and 25° S., in the central and western parts of the supercontinents. The Tethyan Gulf and its environs, lying in low latitudes, and landlocked by the great supercontinents, seems to have behaved like a giant evaporating pan wherever there were suitable bays or other local physiographical conditions. The other evaporite occurrences, in Africa and South-east Asia, lie at about 40° of Upper Triassic latitude, and so can be regarded as contemporary ‘horse latitude’ arid zones. Aeolian deposits occur chiefly in the interior of the two supercontinents, and in Gondwanaland with its more continental polar regions, up to quite high latitudes. Red-beds occur chiefly in two zones; either in the intertropical zone (approximately 25° N.-25° S.), or in middle latitudes, especially in Gondwanaland, and not too distant from western seas and ocean, or from the Tethyan Ocean (and its Madagascan Gulf). Coals occur mainly in the eastern, peninsular parts of the two supercontinents, in middle to high latitudes, where temperatures may have been more moderate, and rainfall less strictly seasonal under the stormier influence of the belt of westerlies and polar easterlies. Of the four lithologies discussed above, three are suggestive of climates with at least a seasonal drought. In considering the general environments available to land-dwelling vertebrates in Upper Triassic times the scale and generality of the world-map (text-fig. 5) should not be forgotten. It should not be imagined that the central and western parts of the two supercontinents were one vast monotonous desert of evaporites and windblown sand. Between these more arid areas were better-watered regions with a seasonal rainfall at least, as is shown by the details of the sedimentary record of the Upper Triassic of North America and Europe for example. But the map suggests that, except in the high lati- tudes of the eastern regions, environments with at least a seasonal drought were wide- spread over the lands of the Upper Triassic world. If, early in the Triassic, the sauropsids had evolved their basic physiological characters of uricotelism and well-controlled ecto- thermy, with a range of body core temperatures which in some extended to high values, 144 PALAEONTOLOGY, VOLUME 14 then they would have been well adapted to the environments generally prevailing over the lands of Upper Triassic times. It may be objected that some of the world’s most famous salt deposits occur in Permian rocks, at a time when theropsids were widespread and abundant. But though Permian salt deposits are thick and economically important, evaporites, including gypsum, are more restricted in time and space during the Permian than during the Upper Triassic. They are also restricted in distribution during the Upper Carboniferous (Pennsylvanian), the period during which the theropsids originated. During Pennsyl- vanian times evaporites are known chiefly from the Amazon (Manaus) basin, from the Paradox basin of Colorado-Utah and some adjoining areas, from the Sverdrup basin of Arctic Canada, from East Greenland and Spitzbergen, and from very restricted areas of central and eastern U.S.S.R. Pennsylvanian coals are widely distributed in the central parts of Laurasia, from eastern North America to the Donetz basin and beyond. In the lower Permian (Sakmarian-Artinskian) evaporites are known chiefly from Peru, per- haps from the Amazon (Manaus) basin, from parts of the Mid-Continent region of North America, from very restricted areas of North Europe (Rotliegendes), and from one or two very small areas of central U.S.S.R. In Gondwanaland glacial conditions covered very large parts of the supercontinent, and were followed by equally widespread coal formation. The Middle Permian (Kungurian-Ufimian) evaporites occur only in Laurasia, chiefly in three regions; in North America in the Mid-Continent, Lusk, and Williston basins, in North Europe in the Zechstein basin (Poland to Greenland), and in the Ural-Caspian and Aral-Black Sea region. There are no evaporites in Gondwana- land, coal formation continued to be widespread there, and red-beds are rare. The Upper Permian was the heyday of the theropsids, so a map has been prepared depicting the pre-drift assembly of continents in approximately the correct Permian latitudes, and showing the general distribution of the same kinds of rock types as those given for the Upper Triassic (text-fig. 6, see p. 152). Evaporites are very restricted in occurrence, in Laurasia only, chiefly in the Mid-Continent and Mexican basin of North America and in the Zechstein basin of North Europe. The general distribution of certain rock-facies, and their broad climatic implications, are as interesting for the Upper Permian as for the Upper Triassic. They seem to demonstrate the combined effects of latitude position, and size of land surface of the two supercontinents, as in the Upper Triassic. But in the Upper Permian the equator lies further north, and the two supercontinents are not quite so symmetrically disposed about it as in Upper Triassic times. In the Upper Permian Laurasia extends from low to high latitudes, whereas the land areas of Gondwanaland lie chiefly outside the inter- tropical zone in middle and high latitudes. This correlates with the restriction of evaporites to low latitude regions, and hence to Laurasia, and their occurrence, through the influence of continentality, in the central and western parts of that supercontinent. Red-beds are widespread in the intertropical zone of the central and western parts of Laurasia; they also have a restricted distribution in Gondwanaland, occurring in middle latitudes and mainly in the west (South America), not too far from western seas and ocean. Red-beds may occur as subordinate facies in Upper Permian fluviatile sediments in certain other parts of Gondwanaland, such as the central parts of the Indian Penin- sula (Robinson 1970). Coals occur in the middle and high latitudes of the eastern, more ‘peninsular’ regions of both supercontinents. P. L. ROBINSON: TRIASSIC CONTINENTAL FAUNAS 145 A comparison of the two maps shows clearly that rock-facies suggestive of semi-arid or arid conditions, or of seasonal drought, are much more restricted in distribution in the Upper Permian. The greater part of the land areas of Gondwanaland, nearly the whole of Asia, and the north-west part of North America, lay in middle to high lati- tudes. The Upper Permian world was free of glaciation, and its middle and high latitudes presumably enjoyed moderately hot to warm temperatures. The rock facies found in these latitudes suggest moderately, or even very well watered environments. FAUNA AND ENVIRONMENT IN THREE UPPER TRTASSIC LOCALITIES The general environments prevalent over the greater part of the lands of Upper Permian times would obviously have suited the basic physiological adaptations found in modern theropsids. That these conditions suited the late Palaeozoic theropsids is sug- gested by the very large number of genera (text-fig. 2) found in continental rocks of this age. Theropsids were rare in the Upper Triassic, sauropsids were abundant, and at this time environments with at least a seasonal drought were widespread over the world’s land areas. But these comparisons are of very generalized information, of total number of genera in each taxon, and of broad environmental conditions, for the whole world, at two different intervals of time. To test the implications of these generalized com- parisons more particular and detailed information is needed, of actual faunas and environments at known localities, supplied by fossiliferous formations of known age. To make this test three localities have been chosen, each of which contains a rock forma- tion and vertebrate fauna of Upper Triassic age. The three localities are situated in widely separated regions of the world, and though their fossiliferous formations all pro- vide evidence of continental conditions, each represents a different type of continental environment. The first is the Maleri formation of the Deccan of India, the second the Lossiemouth-Findrassie formation of Elgin in eastern Scotland and the third the Ischigualasto formation of western Argentina. The Maleri is a red-bed formation, and is chiefly built of three lithologies: thick, bright red, silty clays; poorly sorted, trough cross-bedded, whitish sandstones; and pale green, trough cross-bedded rocks consisting of small, rounded, roughly sorted pellets of lime in a sparse silty matrix. There are several kinds of red-beds (Van Houten 1961), but those lying on the world’s cratons can be roughly divided into two groups: well- sorted sediments associated with evaporites, and poorly sorted sediments containing evidence of fluviatile deposition. The Maleri red-beds belong to the second category, and are the sediments of a river flood-plain situated in the interior of the Indian craton. The presence of abundant iron oxide suggests that there was a hot dry season, with oxidizing conditions either favouring the formation of the iron oxides, or allowing their preservation if brought in from source areas in the hinterland. A fairly high degree of chemical mobilization in source rocks, producing the abundant iron, would require moderately high temperatures in adjoining source areas during the wet season. The peculiar lime-pellet rocks probably also indicate alternate wet and dry seasons in a fairly hot climate of monsoon type (Robinson 1964). Poorly preserved fossil wood is locally abundant in the formation, but no other plant remains are preserved as macrofossils. Shell banks of unionids occur locally in the red clays and pellet rocks (Kutty 1969). C 7895 L 146 PALAEONTOLOGY, VOLUME 14 The vertebrate fauna is listed below. Maleri formation : vertebrate fauna Fishes Ceratodus subholostean pleuracanth Amphibia metoposaur Reptiles phytosaur rhynchosaur aetosaur saurischian* (* Personal communication, from recent discoveries, by T. S. Kutty.) Evidently the Maleri formation represents a monsoon-type climate, with fairly high year-round temperatures, and a dry season alternating with a season of abundant rain- fall. That this was well-watered country, at least seasonally, is suggested by the locally abundant unionids, and by the presence of three aquatic and two semi-aquatic members of the vertebrate fauna. Probably these members of the Maleri fauna passed through the dry season in the more permanent bodies of water in the region, such as the deeper pools along watercourses. The reptiles of the Maleri fauna are all sauropsids, theropsids are completely absent. The well-known vertebrate faunas of the continental Upper Triassic of North America are not dissimilar in composition to that of the Maleri formation, and sauropsid reptiles are abundant while theropsids are absent. The red-beds in which most of the North American Upper Triassic vertebrate faunas are found probably represent environments of deposition most of which were not dissimilar to that of the Maleri. The Lossiemouth and Findrassie sandstones of Elgin, in eastern Scotland, represent a different kind of environment from that of the Maleri formation. The sandstones are mainly aeolian deposits, but they are closely associated, at the base, with fluviatile sedi- ments (Peacock et al. 1968). Probably this was a terrain of watercourses with very dry interchannel areas. As the water-courses shifted position on their flood-plain, their older sites and deposits were overwhelmed by the sand dunes of the semi-arid inter- channel regions. These sand-dunes, blown by winds from the south, buried a sample of the local fauna which lived either near to the river banks, or in the drier interchannel regions. There are no aquatic or semi-aquatic members of the Elgin fauna, and also no theropsids. The Elgin fauna consists of sauropsids, and a procolophonid reptile. Walker (1961, 1964) has made some interesting suggestions about the adaptational characters of some of the members of the Elgin reptile fauna. An armoured aetosaur (thecodont) probably lived close to the river banks, grubbing up vegetation, roots, and small invertebrates with its spatulate snout, and it may have carried a store of fat in its broad-based tail, to tide it over seasonal scarcity, much as in some desert lizards of today. The rhynchosaur may also have lived not far from the river banks, for it may have been a digger too, using its beaked snout and spatulate forked lower jaw and Aquatic Semi-aquatic Terrestrial P. L. ROBINSON: TRIASSIC CONTINENTAL FAUNAS 147 perhaps also its claws, or it may have grubbed up molluscs from the river (Chatterjee 1969). Two members of the fauna which probably lived, at least partly, in the dry sandy interchannel areas are Scleromochlus and Ornithosuchus. The small Scleromochlus has been likened to a jerboa rat, the structure of its hind limbs suggesting jumping habits similar to those of certain modern rodents or marsupials which have become adapted to a leaping progression in sandy arid areas. Ornithosuchus ( Dasygnathus ) was a large saurischian carnivore, reaching a length of about 12 ft and standing about 5 ft high. Its huge skull, 18 in long, was armed with blade-like serrated teeth up to 2-5 in long, and this powerful reptile was at least partially bipedal. The Ischigualasto formation of western Argentina is buff-coloured, greenish, or drab, and some of its sediments contain a considerable admixture of tuff'. Parts of it are cross- bedded, possibly river channel deposits, but the greater part of it seemed, on brief acquaintance, to consist of extremely well-bedded layers of wide lateral extent, suggestive of lake-bottom deposits. Certain horizons contain abundant and well-preserved plant remains. The fossil vertebrates are often present as associated skeletons or skulls, little disturbed, and are present in abundance in some parts of the formation. The environ- ment of deposition of the Ischigualasto formation has not yet received detailed study. Cursory examination of the sediments suggests that this was a region with more sus- tained rainfall in Upper Triassic times, lacking the dry season of the Maleri environ- ment. The Ischigualasto formation must have lain almost at the western margin of the Gondwana supercontinent, in middle latitudes. Perhaps this was a region of on-shore winds, which brought a more sustained rainfall from the western seas, and sometimes heavy falls of ash from volcanoes immediately to the west, along the Andean geosyn- cline, to a series of lakes surrounded by abundant vegetation and a rich and varied fauna of vertebrates. The composition of the fauna is interesting. Sauropsids are well represented by a rhynchosaur, saurischian and ornithischian dinosaurs, a sphenosuchid crocodilian, and other reptiles. But several genera of theropsids are also found abun- dantly in the Ischigualasto formation, and represent stocks which had been more wide- spread on the world’s land areas in earlier Triassic times. Knowledge of environments of deposition of fossiliferous continental formations of Upper Triassic age is still very inadequate in many cases. However, text-fig. 4 attempts to show the distribution of the major tetrapod vertebrate taxa of Upper Triassic times in the three environments just discussed, for all localities, as far as this is possible. The three environments have been designated arid and semi-arid (e.g. the Lossiemouth- Findrassie sandstones of Elgin, and the Upper Norian fissure deposits of the Bristol Channel area), monsoon and savannah (e.g. the Maleri formation of the Indian Deccan— monsoon), and moist warm equable (e.g. the Ischigualasto formation of western Argen- tina). In some red-bed localities, probably representing monsoon and fluviatile con- ditions, theropsids do occur, usually as minor elements of the faunas (e.g. the upper part of the red beds of the Stormberg Series of southern Africa). Theropsids have there- fore been represented as occasionally present in the monsoon-savannah environment in text-fig. 4, but as occurring mainly in formations representing more equable con- ditions with a less seasonal rainfall. Amphibia occur in both monsoon and equable environments but are absent from the more arid regions. Sauropsids occur in all three environments. It is interesting to compare the distribution of these taxa with that of their modern representatives in these environments (text-fig. 4). 148 PALAEONTOLOGY, VOLUME 14 BASIC PHYSIOLOGICAL CHARACTERS AND ENVIRONMENTAL CHANGE There is a growing awareness amongst ecologists of the nature of the links between environment and physiological adaptation in modern reptiles, birds and mammals (e.g. Brown 1968). Enough work has now been done on all three groups for one to try to discern some of the basic physiological adaptations which characterize the three groups, as has been attempted here. Some important physiological aspects such as salt balance and the regulation of the ionic composition of the body fluids have had to be omitted, partly for the sake of brevity, partly because more work is needed before any generalizations can safely be made. For the Permo-Triassic one can discern a correlation between the relative number of genera of the two major taxa of reptiles and the types of environment which were widespread over the world’s land areas. This correlation is supported by the examination of some particular faunas from specific localities. It seems reasonable to suggest that the correlation is due to different basic physiological characters in the two taxa. These differences relate particularly to the range of body core temperatures preferred in the two taxa, whether or not they were endothermic, and to the degree of conservation of body water allowed by their method of excreting nitrogen. The wide distribution of more equable conditions of temperature and rainfall present on much of the land surface of Upper Permian times obviously suited contemporary theropsids. It is unlikely that the theropsids were endothermic at this time, but it is probable that they had the same preferences as modern forms for a range of body temperature which did not extend to such high values as those found in modern sauropsids. It is probable that the basic physiological characters of the sauropsids, as still shown by their modern descendants, evolved as this taxon differentiated early in the Triassic. These physiological characters, of uricotelism, and the ability by some to adopt higher eccritic temperatures, allowed the Triassic sauropsids to adapt to environments with high year-round temperatures, and at least a seasonal drought. Such environments gradually increased in frequency on the world’s lands during the Triassic, in the middle and low latitudes, and became especially widespread in Upper Triassic times. Some of the labyrinthodont amphibians, such as metoposaurs and capitosaurs, were able to adapt themselves to the monsoon environments of the Upper Triassic. Probably they did so in the manner of the modern Australian lungfish, which lives in Queensland’s monsoon environment. This lungfish, unlike its contemporary relatives in Africa and South America, does not aestivate, but spends the dry season lurking in the larger and more permanent pools of the shrunken Murray River. The Upper Triassic labyrintho- donts were too large to aestivate, and probably adopted the same method of enduring the dry season of Upper Triassic monsoon environments. During their Permo-Triassic history the theropsids had rather rarely evolved semi-aquatic forms, perhaps only certain pelycosaurs and dicynodonts. This suggests that the theropsids had adapted very well, as truly terrestrial vertebrates, to the less stringent environments which were widespread over the later Permian and early Triassic continents, but it closed to them the method of coping with a dry season adopted by the labyrinthodont amphibia. A few very advanced theropsids (‘near-mammals’ and ‘only-just-mammals’) are found P. L. ROBINSON: TRIASSIC CONTINENTAL FAUNAS 149 in the environments more generally suited to sauropsids, in the late Triassic red-beds of South Africa, for example, where they occur with a fauna or archosaurs. Most of them are small forms, and, like their modern counterparts, were probably able to find, or make, microhabitats with microclimates which were tolerable for their physiological range during the more stringent seasons and times of day. Except the tritylodonts, these very advanced theropsids are rare in the red-bed facies of the Upper Triassic, as those interested in the early evolution of mammals are regretfully aware. We know rather little of the later Mesozoic history of theropsids. This history, and also its sequel, the emergence of the theropsids from their Mesozoic eclipse in late Cretaceous and early Tertiary times, require separate discussion for adequate docu- mentation. But though this later chapter of tetrapod history lies outside the scope of the present theme, the Triassic and Permian, certain aspects are not irrelevant to some of the main points discussed above. For brevity, these aspects can only be touched on in a tentative way, and discussion must be restricted to the northern hemisphere. The Jurassic theropsids of Europe, known chiefly from the fissure fillings of the Liassic islands of Glamorgan and the Somersetshire Mendips, also from near shore deposits close to contemporary islands at Stonesfield, and from the Kimmeridgian coal measures of Portugal, are all very small forms. The environment of the Liassic islands has already been discussed, and probably that of the Stonesfield ones was not dissimilar, though by Upper Jurassic times the Stonesfield islands would have lain at about 20° N. latitude. The coal-measures of Portugal are suggestive of humid conditions, Kuehne (1968) has described the environment of deposition as a swamp, and the region would be at about 10-15° N. in Upper Jurassic times. All three environments are suggestive of equable and rather humid climates. The kind of world which confronted the theropsids in the early Tertiary of the northern hemisphere was one in which the palaeo-equator was situated about 10° N. of its present position. North America had begun to drift away from Eurasia and the North Atlantic was in being. In Eurasia the north shore of Tethys took an undulatory course approximately between the 30th and 40th parallels of early Tertiary northern latitudes. The terrestrial part of Eurasia thus lay mainly in middle and high latitudes. In North America an enlarged Gulf of Mexico extended north into the present Missis- sippi basin, about as far north as the 35th parallel of north latitude of early Tertiary times. This enlarged Gulf was flanked on the west and north-west by a lowland tropical to subtropical savannah of broad-leaved evergreen plants (Johnson 1968). In both northern hemisphere continents, therefore, the hotter low-latitude regions were largely covered by sea, and the two main landmasses were mainly situated in middle and high latitudes. Palaeobotanists have suggested that mild climates extended into quite high latitudes (e.g. Alaska and Greenland) at this time. In the early Tertiary therefore, environmental conditions were generally very different from those of the Upper Triassic, and more similar to those of the southern hemisphere and Asia in Upper Permian times. Climates with less seasonal drought and milder temperatures than those prevalent in the Upper Triassic were widespread over the land areas of the early Tertiary northern hemisphere. These environments, by analogy with the situation in the Upper Permian, should have suited the basic physiological characters of the theropsids. In fact, the theropsids began a spectacular radiation in the early Tertiary, evolving structural 150 PALAEONTOLOGY, VOLUME 14 adaptations fitting them for various ecological roles in the environments offered by the main landmasses of the northern hemisphere. During the late Palaeocene and Eocene there occurred, in many stocks of theropsids, a gradual enlargement of the brain, to sizes comparable with those inherited by their later Tertiary and Quaternary representatives. In a few stocks, such as primates, increase in relative size of the brain continued later, through late Cainozoic times. It is reasonable to suppose that general increase in brain size would proceed hand in hand with improvement of the basic physiological characters of theropsids, and that these included endothermy, with increase in basal metabolic rate and evolution of better thermo-regulatory mechanisms, and improvement in methods of nitrogen excretion and maintenance of electrolyte balance. Possibly cool nights or cool seasons may have been important factors in selection for improvement of thermo-regulatory mechanisms. CONCLUSIONS Had the problem chosen for this Address been one of phylogeny or structural adaptation of the Triassic terrestrial vertebrates, a much more solid array of facts could have been presented, facts produced by a method which has won wide acceptance over a long history of research. For the method of comparative anatomy is fairly old as a scientific discipline, so that today we have a considerable accumulation of data on which to build current researches, and the method will always be the backbone of research in vertebrate palaeontology. But there are moments of depression in which one feels that the only dynamic left in this method is that of an isolating mechanism. Too exclusive a preoccupation with comparative anatomy can bring increasing isolation from other disciplines, from geology and zoology, which ought surely to be regarded as the parent sciences of vertebrate palaeontology. I am also uneasily aware that, in studying only the anatomy of Triassic vertebrates I am allowing a great deal of the evolution of these forms to go on, as it were, behind my back. For what lies in front of me, as material for research by the methods of com- parative anatomy, is, as a rule, just the bare bones on the laboratory bench. And though, because I had an excellent teacher — -Professor D. M. S. Watson, F.R.S.— I have learned to extract quite a lot of data from the bare bones, I think that the number of evolutionary problems which can be solved by such data, and the method which produces it, is limited. I believe that no amount of research on bare bones will solve the kind of problem presented by the rather wholesale and sweeping faunal change which affected the major stocks of Triassic reptiles. To try to solve this problem I have turned from the bare bones on the laboratory bench to the sediments in which they are found, and through this to the study of environment. Yet it must be acknowledged that information on types of terrestrial environments, as obtained from the study of continental environment sediments, is still poor. The study of environment requires that some note be taken of palaeolatitudes and contemporary pole positions, and data on these is still scarce. Palaeolatitudes and pole positions have implications which require a study of the hypothesis of continental drift. The distribution of continent and ocean, and of palaeolatitude, at particular periods of time require some general knowledge of meteorology, for both factors profoundly affect the broad distribution of climate in the world. None of this knowledge of environ- P. L. ROBINSON: TRIASSIC CONTINENTAL FAUNAS 151 merits, whether general or particular, can help to solve problems in the evolution of terrestrial vertebrates unless some knowledge of the physiological adaptations of modern representatives is sought, and this knowledge is still in its infancy, though rapidly expanding. The paucity of data in many of these branches of the earth sciences and zoology, and their collective range, sufficiently indicate some of the hazards of this approach. To these is added the danger of too rigid interpretation of some of the data, such as the physiological adaptations of the major taxa. There will always be exceptional genera, as there are at the present day. Perhaps, in the Upper Triassic, tritylodonts were also somewhat exceptional amongst theropsids, as they are not uncommon in some of the late Triassic red-beds, and though not large forms, they are not very small either. Any tendency to sit in judgement on the physiological ‘status’ of taxa of vertebrates, because of a decline in their importance at certain periods of time, may also be unwise. The major vertebrate taxa are not ‘second-class citizens’ but are best regarded simply as groups of terrestrial vertebrates which possess differing arrays of basic physiological characters. These characters are subject to evolutionary change, and they interact with environment. A major factor in determining general environmental conditions is climate, which also changes. Since mid-Mesozoic times the continents have drifted apart, but the palaeomagnetic data suggests that there has also been a general migration northward of most of the world’s continents. As the continents migrated slowly northward across the parallels of latitude, first one set of environmental conditions, and then another, became wide- spread over the world. These changing environmental distributions offered scope for the basic physiological characters of first one major taxon and then another. The degree to which certain lithologies become widespread only in certain geological systems has already been remarked. The tectonic factor, influencing the degree to which continents are emergent or submerged, governs the distribution of the two major environments, marine and terrestrial, and also governs local relief, and hence certain aspects of sedimentation. But climate also profoundly influences sedimentation on the continents and their shallow seas. Hence the changing incidence of latitude and land- mass, and the size of the latter, are important factors, and have affected the distribution of lithologies and their relative abundance at different periods. Being ourselves terrestrial animals we can investigate and comprehend the terrestrial environments more easily than those of the seas. The Permian and Triassic, with their abundance of terrestrial lithologies, offer excellent scope for such investigations, and have a fine sequence of terrestrial vertebrate faunas. This is another reason for choosing, as the subject for this Address, a problem of Triassic vertebrates which, I believe, requires us to relate terrestrial vertebrate faunas to their continental environments. APPENDIX NOTES ON THE MAPS Projections. The problem was to obtain good representation of a very large landmass sprawling from pole to pole, and in which south polar regions contained important elements of this landmass. Inter- rupted projections were not considered as they usually interrupt meridionally. Hence continuous world projections remained and two of these are most commonly used in discussions of continental drift. Both are equal area world maps, one is Mollweide’s projection, the other Hammer’s (sometimes 152 PALAEONTOLOGY, VOLUME 14 known as Aitoff’s), the latter being most often used (though it is occasionally referred to as Moll- weide’s). Both give poor representation of polar areas, as do all other variants of the oval world maps such as Denoyer’s semi-elliptical, Sanson’s sinusoidal, etc., and also the circular Van der Grinten. Transverse projections of these maps simply shift the poor representation or distortion to some of the ‘lateral’ meridional areas. Of the oblique equal area projections Breisemeister’s and Bartholomew’s suffer from the disadvantage of having two south (or north) polar areas and poor representation of the south polar regions. One oblique projection was found to serve very well for pre-drift assemblies, that of Fairgrieve (Close 1929). Fairgrieve’s is an oblique case of Mollweide’s equal area projection, in which the great circle of the two 90° meridians is retained but, as it were, tilted on one side so that the poles are centred on the old 45° parallels. The principal meridian and the equator are similar curves but inverted in respect of each other, and both pass through the centre of the bounding ellipse. It will be seen from the accompanying maps that this projection gives good representation of pre- drift continental assemblies except close to the northern half of the 90° E. meridian, and close to the southern half of the 90° W. meridian. Polar representation is better than in the normal Mollweide projection. The latter has, however, also been given, because it is more familiar, and can be used for comparison with other maps of pre-drift assemblies. Most of the latter are on Hammer’s projection, which has curved latitude lines, except the equator, and hence gives very slightly less distortion of polar areas than Mollweide’s. In projecting the pre-drift assembly on to the graticules the latitude lines are known, at least for some continents, but meridians are arbitrary. The great circle of the two 90° meridians of the graticule has been emphasized, on the oblique projection, to serve as a reference-frame for comparing the two maps. Upper Triassic and Upper Permian. Assembly of continents. Most of the more recent assemblies of continents to pre-drift positions have been made from the viewpoint of some particular line of evidence: the fit of continental shelves and upper slopes, palaeomagnetic data for a particular rock formation and continent, mid-oceanic ridges, or special geological features. All four lines of evidence were used in making an assembly for the Upper Triassic, and the data married together remarkably well. The north polar position is 50° N., 150° E., on the present globe and the 80° S. parallel runs through the southern tip of Tasmania (Irving 1964, table 6.2, figures 6.9 and 9.40). An assembly for the Upper Permian should differ in detail from that for the Upper Triassic, to depict major geological events and features of Upper Permian times. However, owing to shortage of time, the Upper Triassic assembly has been used for the Upper Permian, with a north polar position of 45° N. and 165° E. on the present globe. Inevitably the marriage of all data is not quite so good as for the Upper Triassic, e.g. latitude lines are correct for the east coast of North America, but not quite correct for the west coast, and Australia is about 10° of latitude too far north. It is hoped to make a better reconstruction for the Permian in a later paper, which will give a better synthesis of the evidence, especially for that portion of Gondwanaland which lies in Upper Permian high latitudes. Map data sources. Evaporites: Borchert and Muir 1964, Hepple 1969, Kent 1965, Lefond 1969, Lotze 1957, 1964. Palaeowinds: Poole 1964, Opdyke 1961. Other data from standard texts, especially the Lexicon Stratigraphique. REFERENCES Bartholomew, g. a. 1968. Body temperature and energy metabolism. In Gordon, m. s., Animal function: principles and adaptations. Macmillan. and dawson, w. r. 1968. Temperature regulation in desert mammals. In brown, g. w. (ed.), Desert biology. Academic Press. borchert, h. and muir, r. o. 1964. Salt deposits. Van Nostrand. brown, G. w. (ed.). 1968. Desert biology. Academic Press. bullard, e., everett, J. e., and gilbert smith, a. 1965. The fit of the continents round the Atlantic. Phil. Trans. Roy. Soc. Lond. A258, 41-51. chatterjee, s. 1969. Rhynchosaurs in time and space. Proc. geol. Soc. Lond. 1658, 203-8. close, c. 1929. An oblique Mollweide projection of the sphere. Geogr. Jl., 73, 251-3. text-fig. 5. Maps of world palaeogeography in the Upper Triassic, the continents in their correct positions of palaeolatitude (meridians arbitrary), showing the distribution of certain rock types. Lower map on a normal Mollweide projection graticule, upper map on an oblique Mollweide projection graticule. Arrow = wind direction; stipple = major seas, full black = evapo- rites; a = aeolian, c = coals, d = deltaic, f = fluviatile, l = lacustrine, r = red beds. text-fig. 6. Maps of world palaeogeography in the Upper Permian (Kazanian-Tartarian), in approximate positions of palaeo- latitude (meridians arbitrary), showing the distribution of certain rock types. Lower map on a normal Mollweide projection graticule, upper map on an oblique Mollweide projection graticule. Arrow = wind direction; stipple = major seas, full black = evaporites; a = aeolian, c = coals, d = deltaic, f = fluviatile, l = lacustrine, r = red beds. P. L. ROBINSON: TRIASSIC CONTINENTAL FAUNAS 153 dawson, w. r. and Bartholomew, g. a. 1968. Temperature regulation and water economy of desert birds. In brown, g. w. (ed.), Desert biology. Academic Press. Gordon, m. s. 1968. Water and solute metabolism. In Gordon, m. s., Animal function: principles and adaptations. Macmillan. halley, e. 1686. An historical account of trade-winds and monsoons with an attempt to assign the physical cause of the said winds. Phil. Trans. Roy. Soc. Lond. 16, 153-68. hepple, p. (ed.). 1969. The exploration for petroleum in Europe and N. Africa. Inst. Petrol. London. houten, F. b. van. 1961. Climatic significance of red beds. In nairn, a. e. m. (ed.), Descriptive palaeo- climatology. Interscience. 1964. Origin of red beds — some unsolved problems. In nairn, a. e. m. (ed.), Problems of palaeo- climatology . Interscience, Wiley. irving, E. 1964. Palaeomagnetism. Wiley. Johnson, a. w. 1968. The evolution of desert vegetation in western North America. In brown, g. w. (ed.), Desert biology. Academic Press. kent, p. e. 1965. An evaporite basin in Southern Tanzania. In Salt basins around Africa. Inst. Petrol. Lond., 41-54. kuehne, w. g. 1968. Contribuigao para a fauna do Kimeridgiano da Mina de Lignito Guimarata (Leiria, Portugal) I Parte History of Discovery, etc. Mem. Serv. geol. Portugal, 14, (n.s.), 7-20. kutty, t. s. 1969. Some contributions to the Upper Gondwana Formations of the Pranhita-Godavari Valley, Central India. Jl geol. Soc. India, 10, 33—48. lefond, s. j. 1969. Handbook of world salt resources. Plenum Press, N.Y. lotze, f. 1957. Steinsalz und kalisalze, 2nd edn., vol. 1. Gebr. Borntraeger, Berlin. 1964. The distribution of evaporites in space and time. In nairn, a. e. m. (ed.), Problems in palaeo climatology . Interscience . mayhew, w. w. 1968. Biology of desert amphibians and reptiles. In brown, g. w. (ed.). Desert biology. Academic Press. opdyke, n. d. 1961. The Palaeoclimatological significance of desert sandstone. In nairn, a. e. m. (ed.), Descriptive palaeoclimatology. Interscience. pedelaborde, p. 1963. The Monsoon. Methuen. poole, F. G. 1964. Palaeowinds in the western United States. In nairn, a. e. m. (ed.), Problems in palaeoclimatology. Interscience. prosser, c. l. and brown, f. a. 1961. Comparative animal physiology. Saunders. robinson, p. l. 1957. The Mesozoic fissures of the Bristol Channel area and their vertebrate faunas. Jl ( zool .) Linn. Soc. 43 (291) 260. 1964. Climates ancient and modern. In Essays presented to P. C. Mahalanobis F.R.S. Eka Press and Pergamon Press. — — 1970 (1967). The Indian Gondwana Formations — a review I.U.G.S. Reviews prepared for the first Symposium on Gondwana Stratigraphy, Mar del Plata Argentina, 1967. 1971 (in press). Upper Triassic vertebrates and continental drift. romer, a. s. 1966. Vertebrate palaeontology, 3rd edn. Univ. Chicago Press. walker, a. d. 1961. Triassic reptiles from the Elgin area: Stagonolepis Dasygnathus and their allies. Phil. Trans. Roy. Soc. Lond. B244, 103-204. 1964. Triassic reptiles from the Elgin area: Ornithosuchus and the origin of carnosaurs. Phil. Trans. Roy. Soc. Lond. B248, 53-134. wilson, J. t. 1963. Continental Drift. Sci. Amer. 209, 86-100. PAMELA L. ROBINSON Department of Zoology University College Gower Street London, W.C. 1 Typescript received 30 June 1970 A SYSTEM FOR THE STORAGE, RETRIEVAL AND ANALYSIS OF NUMERICAL DATA IN PALAEONTOLOGY by IAN E. PENN Abstract. A statistical and data-management system (known as ASCOP) and a data-processing service are described. These meet present needs in the handling, storage and retrieval, and analysis of numerical data. The system is available, without cost to university users in the U.K. and to government departments at cost, since it is installed at the Atlas Laboratory, Chilton, Didcot, Berks. The use of numerical data in palaeontology has given rise to three principal problems which are capable of immediate solution. After numerical data have been collected palaeontological activity is of two kinds. On the one hand time must be spent on routine mathematical work while, on the other, time has to be spent on scientific thought. Probably much unnecessary time is spent on the former and it is likely that increasingly complex calculations will aggravate this situation. Although electronic computing has speeded laborious calculation, much time has also been wasted by different palaeontologists repeating the programming efforts of their colleagues. It is thought that the life expectation of a piece of work in palaeontology is about 20-40 years (Craig 1969, p. 317) and it would appear that the most stable part of a work is its ‘raw’ data. While museums store the specimens concerned and professional publications store the thought involved there is as yet no agreed store for the numerical information. A third problem, that of choosing which statistical technique to use, involves scientific thought about which there may be no objective basis of agreement. Different statistical procedures may be considered relevant or irrelevant to similar situations by different palaeontologists. There is a need to accommodate legitimate differences of scientific opinion so as to simplify the problem of choice. Furthermore, new techniques should be made widely available as quickly as possible and not be the preserve of those who happen to possess an appropriate bit of computational hardware. A computing system known as ASCOP (A Statistical Computing Procedure), has been designed specifically to cope with management of data and statistical calculations. Because it is installed at the Atlas Computer Laboratory, Chilton, Didcot, Berks., it is widely available to those with no experience of or even access to electronic data- processing equipment. It is free of charge to university users in the U.K. : and to govern- ment departments at cost. The facility and service is sufficiently flexible to cope with the varied numerical needs of U.K. palaeontologists. APPLICATION OF ASCOP Three main approaches to statistical computation on electronic computers (text- fig. 1) have been applied in palaeontology. In the first, the package of complete programs [Palaeontology, Vol. 14, Part 1, 1971, pp. 154-8. I. E. PENN: HANDLING NUMERICAL DATA 155 b. c. \ DATA / \±2j SYSTEM (ASCOP) DATA ORGANISED BY USER SYSTEM ALREADY WRITTEN text-fig. 1 . To illustrate the three solutions in statistical computation by an example involving comparison of two different sets of data: (a) by a package of complete programs, (b) by a collection of sub-routines, (c) by a statistical system. (text-fig. la), the user needs no programming knowledge but, assuming he can obtain and run the appropriate programs, he must know how each program will accept his data and organize his data compatibly. In the second, a collection of sub-routines enables a programmer to use a single piece of program in a number of places in his 156 PALAEONTOLOGY, VOLUME 14 program or even in different programs without having to rewrite it on each occasion. Given the services of a programmer, it is possible to integrate a package of sub-routines (text-fig. 1 b) to perform many complex analyses. For the third, the statistical system approach (text-fig. lc), no programming knowledge is required. Emphasis is placed on simplicity of presentation of the user’s problem. Complex analyses, involving many stages, may be performed without the intervention of the user. In addition the user has available the expertise of the professional programmers who maintain the system. Since the statistical system approach involves by far the least amount of non- palaeontological effort it must obviously be recommended to palaeontologists. Full details of ASCOP, the particular system advocated here, are contained in the ASCOP User Manual (Cooper 1969u). It is possible by paraphrasing some of its con- tents here to give an indication of the ability of ASCOP to deal with palaeontological problems. Data handling (Manual sections 4, 5, 6, 7 and 15). The Atlas Laboratory will process data presented on cards, paper tape, or magnetic tape provided these can be ‘read’ by its machine. Longhand notation is also accepted provided it is legible. As far as palaeon- tologists are concerned data recorded by the most complex of automatic methods is just as acceptable as data recorded on sheets of foolscap. The basic form of ASCOP input is that of the conventional table arranged in rows and columns (i.e. the data matrix) in which the columns are termed variables and the rows are values of the variables (points); ASCOP terminology is given in parentheses. The variables are referred to by English letters, words, or combination of letters and numbers, supplied by the user while the points are numbered consecutively or carry numerical labels supplied by the user. Provision is made for missing data and for replicated variables (e.g. different values of the same variable for the same point per- haps obtained from successive measurements). Finally, in addition to ‘raw’ data, constant terms (coefficients), series of constant terms (parameters), and statistics such as the correlation or the variance-covariance matrices can be read directly. Reference by means of the variable name and point label enables easy access to individual items and results in convenient organization and reorganization of data matrices. Thus matrices can be added to, or taken from, or combined with other matrices or with newly created ones whose content depends on the results of previous analyses. It is possible, from a single record of the data, to program and experiment with a complete numerical analysis without ever rearranging the original data by hand. Routine handling is done automatically and the time of the palaeontologist is spent almost entirely in designing ‘experiments’ with his data. Data storage and retrieval (Manual section 14). The problem here is no different in kind from the data-handling problem mentioned in the preceding section. Storage time is simply longer. Using ASCOP, data can be stored on magnetic tape for any length of time. It is possible then for an individual who may be remote from computing facilities to build up his personal data bank. It is anticipated that widespread use of this facility would ease the demand for publication space. Reference could be made to the particular tape and an individual sufficiently interested in the content of a paper could have, on request, a print-out of the entire data on which it is based. He may even perform his own analysis of the data before receiving a print-out. I. E. PENN: HANDLING NUMERICAL DATA 157 Data analysis (Manual sections 8, 11, 12, 13, 16, 17, 18, 20 and 21). Arithmetic opera- tions such as the calculation of ratios, percentages and frequencies may be carried out and items may be plotted on any desired scale as histograms, scatter diagrams, or arranged as geographical and stratigraphical distributions. Discontinuous variates can be treated by tabulation and associated tests of significance carried out, while continuous variates can be treated by any of a variety of techniques ranging from simple univariate analysis to component, factor and discriminant analysis. A list of some of the statistical operations available at the moment is in the Appendix to this paper. Provision has been made in ASCOP for the writing of new sub-routines so that it is possible for the analysis section to be kept abreast of new developments in palaeonto- logical statistical techniques: for example, the reduced major axis regression technique was inserted as a new sub-routine to accommodate palaeontological users. Were it used sufficiently frequently then it would be incorporated in the main body of the system. SUMMARY AND CONCLUSIONS The statistical system described is at present available and is adequate to meet present palaeontological needs in the handling, long-term storage and retrieval, and analysis of numerical data. The principal advantages to an individual using ASCOP are as follows: 1. Time is saved on the mechanical operations of statistical calculation and data handling. 2. There is access to powerful computational techniques as well as to a data store. 3. No previous knowledge of computing or local access to automatic data preparation techniques is required. 4. The entire service operates free of charge to U.K. university users and to government departments at cost. The facilities and service described here are available at the present moment to any British palaeontologist. Were all to use them and each build up his personal data bank then there would be de facto a national data bank for numerical data in palaeontology. This could be used as a backing to formal publication. ASCOP, however, provides more than the ability to store data, it provides a range of statistical analyses. Use by all would facilitate a standardization of statistical technique but would also remain flexible enough for each to pursue his own method of analysis. If numerical description becomes an integral part of palaeontological description it is envisaged that a system such as ASCOP would be integrated with a data bank dealing with other aspects of palaeontology. In the meantime it is for those who feel the need for such facilities to use them now; in due course a numerical bank of national proportions should emerge. Acknowledgements . The writer acknowledges the help given by the staff of the Atlas Computer Labora- tory at Chilton, Didcot, Berks. He is especially indebted to B. E. Cooper, the author of the ASCOP system. Dr. W. D. I. Rolfe, Hunterian Museum, University of Glasgow gave valuable advice and encouragement. This paper is published by permission of the Director of the Institute of Geological Sciences. 158 PALAEONTOLOGY, VOLUME 14 APPENDIX The following is a list of the statistical operations of common palaeontological application which ASCOP currently (1970) performs: Univariate analysis of each variable minimum value maximum value mean variance standard deviation skewness kurtosis fitting of a normal distribution chi-squared test of normality certain analyses of variance Bivariate and multivariate analyses of any combination of variables correlation and variance-covariance matrices simple regression multiple regression components analysis factor analysis discriminant analysis REFERENCES cooper, b. e. 1967. ASCOP — a statistical computing procedure. // R. statist. Soc. Series C (Applied Statistics), 16 (2), 100-10. 1969a. ASCOP User Manual. Available from the National Computing Centre, Quay House, Quay Street, Manchester 3, England. 19696. In milton, R. c. and nelder, j. a. (eds.), The continuing development of a statistical system in Statistical Computation, 295-315. Academic Press. craig, G. Y. 1969. Communication in geology. Scott. J. Geol. 5 (4), 305-21. IAN E. PENN Department of Palaeontology Institute of Geological Sciences Exhibition Road London, S.W. 7 Typescript received 6 June 1970 SOME TRILOBITES FROM THE SILURIAN/DEVONIAN BOUNDARY BEDS OF CZECHOSLOVAKIA by IVO CHLUPAC Abstract. Some new or stratigraphically especially important trilobites from the Uppermost Silurian (Prldolian) and the Lowest Devonian (Lochkovian) of Bohemia are described. Tropidocare gen. nov. and Prantlia ( Tetinia ) subgen. nov. are newly erected, and new species described are: Tropidocare index sp. nov., Wolayella ranuncula sp. nov., Scharyia nympha sp. nov. and Ceratocephala lochkoviana sp. nov. The description of some species significant for the definition of the Silurian/Devonian boundary, i.e. Prantlia ( Tetinia ) minuta Pribyl et Vanek 1962 and Warburgella ( Podolites ) rugulosa rugosa (Boucek 1934), are completed. In the latter species, particular attention is directed to the individual variability of the sculpture and the changes during ontogeny. The diagnosis of Warburgella ( Podolites ) Balashova 1968 is discussed, and the species Prionopeltis striatus troilus Hawle et Corda 1847, characteristic of the Uppermost Silurian of Bohemia, has been restituted. On the occasion of recent investigations of the Silurian/Devonian boundary beds in the classical area of the Barrandian in central Bohemia, a new rich trilobite material was found; it not only contributes to a more accurate knowledge of the species already well known, but has also yielded some new ones. The present paper contains the descriptions of these several trilobites, especially those which are stratigraphically or otherwise noteworthy. The pertinent localities are described in detail and the general evaluation of the bio- stratigraphical significance of the fauna from boundary beds is given in another paper presented at the same time (Chlupac et al. 1970), to which the reader is referred. The terminology in the descriptions of the fauna has been used according to the Treatise on Invertebrate Paleontology, Part O, Arthropoda I (1959); some further commonly accepted abbreviations have also been employed : L = lateral glabellar lobes, PF = pleural furrows, IPF = interpleural furrows, the greek symbols a-m = bends of facial suture (in the same sense as, for instance, in G. K. B. Alberti 1969), abax. = abaxially, adax. = adaxially. The material studied is deposited in the collections of the Geological Survey of Czechoslovakia, Prague (the specimens are designated by the symbol ICh before the inventory number). A further comparative material is to be found in the collections of the National Museum, Prague (abbreviated NM). Acknowledgements. The author thanks Dr. H. Alberti of the University of Gottingen, Dr. G. K. B. Alberti of the University of Hamberg, Dr. R. Horny of the National Museum, Prague, Dr. E. Vogel of the Central Geological Institute, Berlin, for having made available the comparative material ; also Dr. J. Kriz of the Geological Survey, Prague, for the gift of the material collected by him, and Mr. P. Lukes for his help in field collecting. SYSTEMATIC PALAEONTOLOGY Family proetidae salter 1 864 Subfamily proetidellinae Flupe 1953 Genus tropidocare gen. nov. [Palaeontology, Vol. 14, Part 1, 1971, pp. 159-77, pis. 19-24.] 160 PALAEONTOLOGY, VOLUME 14 Type species. Tropidocare index sp. nov. Derivation of name. From the related genus Tropidocoryphe. Diagnosis. Cephalon resembling that of Tropidocoryphe, with subtrapezoidal glabella, 3 pairs of glabellar furrows of which deeply incised Sx completely separates the basal lobes. Preglabellar field long with narrow tropidium, anterior border narrow, without wall-like vaulting. Palpebral lobes strongly abax. curved, of medium size. Occipital ring not tapering laterally with indistinctly separated occipital lobes. Pygidium of Proetidellinae-like character with a narrow axis, richly segmented, and with prominent ribs on the lobes. PF and IPF sharp, both bands of the ribs well and equally developed. Border very narrow. Remarks. The characteristic feature of the genus is the Tropidocoryphe- like cephalon and the Proetidellinae-like pygidium having equally developed the anterior and posterior bands of the ribs. The configuration of the carapace of Tropidocare furnishes evidence that the subfamilies Tropidocoryphinae and Proetidellinae are closely related and that connecting links may exist between them. As the first representatives of the subfamily Tropidocoryphinae appear later than those of Proetidellinae, it is possible to conclude that Tropidocoryphinae separated from Proetidellinae, and that just the genus Tropido- care could represent one of the connecting links between them. On the other hand, it cannot, however, be excluded that the subfamily Proetidellinae, as conceived in the Treatise on Invertebrate Paleontology, is an artificial taxonomical unit to which various proetid trilobites, not related to each other, are assigned. At any rate, Tropidocare belongs to phylogenetically noteworthy trilobites. Prantlia Pribyl 1946 shows a certain analogy, but it differs in the configuration of the frontal part of cranidium, lacks a tropidium and has a (sag.) longer pygidium inflated in another way, with a broader border. Occurrence. See the type species. Tropidocare index sp. nov. Plate 19, figs. 1-11, text-fig. 1 Holotype. Cranidium (ICh 3067) figured on Plate 19, fig. 2. Type locality. Klonk near Suchomasty. Horizon. Lower part of the Lochkov Formation, Monograptus uniformis Zone. Early Lower Devonian (Lower Lochkovian). Material. Eighteen cranidia, 21 free cheeks, 35 pygidia preserved as external moulds and their counter- parts. Description. Cranidium analogous to that of Tropidocoryphe. Glabella subtrapezoidal, of moderate convexity, in the anterior half strongly tapering, anteriorly rounded, bounded by sharp and deep dorsal furrows. Three pairs of glabellar furrows: the posterior (S^ deep, simply bent, less incised at the occipital furrow, but completely separating the basal lobe which shows a prominent convexity of its own. The median furrows (S2) I. CHLUPAC: SILURIAN/DEVONIAN TRILOBITES 161 shorter than Sx but well discernible as a line directed obliquely backwards. The anterior furrows (S3) short, developed as a short notch in the anterior third of the glabella (easily seen especially on internal moulds). Preglabellar field long sag. (approx. \ of the length of glabella) with a well-developed narrow tropidium. Frontal part of cranidium anteriorly markedly concave, anterior border not-differentiated, without wall-like vaulting, only moderately upraised. Occipital furrow sharp, laterally (posterior to Lx) widened and connected with the dorsal furrow. Occipital ring not tapering laterally with indistinctly separated occipital lobes; median tubercle small. a b text-fig. 1 a-b. Tropidocare index sp. nov., cranidium: a, dorsal view; b, lateral view from the left, x 10. Fixed cheeks in the anterior part moderately convex, sloping antero-laterally. Palpe- bral lobe of medium size, strongly curved abax., inflated, with a shallow palpebral furrow. The posterior part of the fixed cheeks triangular, strongly widened abax., posterior border narrow. Facial sutures: anterior branch (/3-y) long, diverging at an angle of 20-25° to the sag. axis, |8 rounded, y at a short, almost equal distance from dorsal furrows as e; a>, in a longitudinal projection lies considerably further from the sag. axis than ft. Free cheeks show a moderately convex genal field with a narrow tropidium which dies out postero-laterally. The border furrow is represented by a broad depression, lateral border gently upraised. Genal spine of medium length, rapidly tapering distally, with a marked longitudinal furrow which extending from the genal angle continues on to the spine. The posterior border broadening abax., separated by a sharp posterior border furrow. Doublure concave with parallel lines. Pygidium semicircular, richly segmented. Axis narrow, strongly arched tr., very slowly tapering backwards, composed of ten complete rings (+ articulating half-ring and terminal piece). In the antero-lateral part of each ring a pit-like appendifer. Post- axial ridge narrow but distinct, continuing onto the border. Dorsal furrows deep. Pygidial lobes inflated, near the border region abruptly sloping to the border. On the lobes, 5-6 sharply separated complete ribs broadening abax. The ribs are separated by sharp narrow PF which in their whole course maintain the same breadth and depth. M C 7895 162 PALAEONTOLOGY, VOLUME 14 IPF also sharp during their whole course, however, less incised than PF, dividing the ribs into almost equally broad bands (the posterior bands near the border region broadened). Border furrow weak, border very narrow, flat. Pygidial doublure narrow, concave, with parallel lines. Sculpture. Not whitened, the surface of the carapace seems to be smooth, and only after whitening it shows very fine granulation on the glabella, occipital ring, and pygidial axis; marks of ridges indicate genal caeca; in addition, on the genal field, punctation is also discernible (for instance, ICh 3165). Measurements (in mm) Length of Length of Breadth of Cranidium cranidium glabella glabella ICh 3067 4-5 30 2-2 ICh 3068 3-2 2-0 1-7 ICh 3069 40 2-7 20 ICh 3070 41 2-6 2-1 Pygidium Length Breadth ICh 3072 4-0 (6-8) ICh 3073 30 6-5 ICh 3074 3-9 7-0 ICh 3075 40 (70) Remarks. As mentioned in the discussion of the genus, the characteristic feature is the analogy with Tropidocoryphe as to the configuration of cranidium, and typically proetidellid-like pygidium. The cranidia examined belong, no doubt, to the pygidia, as at the type locality, Klonk, in a 20-25-cm thick bed (No. 95: Chlupac et al. 1970) a confusion with another trilobite is excluded, any other analogous trilobites being absent there; in addition, the cranidia and pygidia also correspond to each other as to their frequency and size, and with regard to the fact that occasionally both were found lying close to each other on the same bedding plane. In the bed 95 at Klonk, in addition to the specimens of normal size, remains of young individuals have also been encountered. The smallest pygidium found measured 1-5 mm in length and 3-00 mm in max. width (ICh 3078). Compared with the remains of adult specimens, this pygidium is flatter with deeper incised PF and wider border. Another pygidium (ICh 3077) 2-0 mm long and 3-8-4-0 mm broad already very closely resembles the adult specimens from which it differs in a somewhat wider border only. There is only one trilobite from the Lochkovian, so far described, which displays a certain similarity, i.e. Tropidocoryphe ? heteroelyta (Barrande 1872) which is known EXPLANATION OF PLATE 19 Figs. 1-11. Tropidocare index sp. nov. Lower Lochkovian, Klonk (figs. 1-9, 11), Karlstejn (fig. 10). 1, Cranidium (ICh 3069), Xll-5. 2, Cranidium, holotype (ICh 3067), xlO. 3, Cranidium (ICh 3068), x 13. 4, Cranidium (ICh 3070), x 11. 5, Pygidium (ICh 3072), x8. 6, Right free cheek (ICh 3076), x 8. 7, Left free cheek (ICh 3071), x 10. 8, Left free cheek (ICh 3079), x9. 9, Pygidium (ICh 3073), x8. 10, Pygidium (ICh 3074), x8. 11, Pygidium (ICh 3075), x8. Figs. 12-13. Woiayella ranuncula sp. nov. Upper Lochkovian, Kosor. 12, Cranidium (ICh 3273), x 13. 13, Negative counterpart of cranidium (ICh 3269), x 12. Palaeontology, Vol. 14 PLATE 19 CHLUPAC, Silurian/Devonian trilobites I. CHLUPAC: SILURIAN/DEVONIAN TRILOBITES 163 from the find of a single pygidium. This pygidium, however, has the anterior and posterior bands of ribs developed in the anterior three ribs only, furthermore, the axis is substantially shorter and the general configuration much more resembles Tropido- coryphe. Occurrence. All the occurrences so far known belong to the Lower Lochkovian, Monograptus uniformis Zone. In addition to the locality Klonk near Suchomasty where Tropidocare index sp. nov. occurs fairly abundantly in the bed 95 (black-grey fine-grained limestone) together with Ceratocephala loclikoviana sp. nov., further finds come from the locality Karlstejn- Budnanska skala rocks, the Koukolova hora Hill (the quarry below the summit) and Lejskov near Zdice (for detail of localities, see Chlupac et al. 1970). Genus prantlia Pribyl 1946 Type species. Proetus longulus Hawle et Corda 1847. Subgenus prantlia (tetinia) subgen. nov. Type species. Prantlia minuta Pribyl et Vanek 1962. Derivation of name. From the locality Tetln near Beroun, where the type species commonly occurs. Diagnosis. Glabella longly subtrapezoidal, blunt anteriorly. The posterior glabellar furrow Sx completely separates the basal lobes, S2 short and shallow, S3 scarcely per- ceptible. In the frontal area, parallel shallow axial furrows continue forward to the border furrow, defining a low preglabellar lobate tract. Border furrow sharp, deeply incised laterally, bent in a connecting line with the dorsal furrows, shallowed and con- spicuously arcuate anterior to the frontal lobe. Anterior border flat, broad (sag.). Pygidium similar to that of Prantlia but shorter, with conspicuously inflated lobes and a lesser number of axial rings (10) and ribs (4-6). Remarks. The most characteristic feature of P. ( Tetinia ) is the configuration of frontal area of cranidium. Prantlia ( Prantlia ) Pribyl 1946 differs especially in long (sag.) con- cave preglabellar field, ill-defined border furrow, narrow upraised border, subconical shape of glabella, three distinct pairs of glabellar furrows (S2 substantially longer, S3 well perceptible) and in prominent occipital lobes. It should be noted that the draw- ing of Prantlia longula published by Pribyl (1946, pi. 1, fig. 12) according to a figure taken over from Novak’s unpublished manuscript and reprinted in the Treatise (1959, fig. 3016) is idealized. A good figure of the same specimen according to which the draw- ing was made (NM 55/67) was presented by Horny and Bastl (1970); see also Plate 20, figs. 10-11. Warburgella Reed 1931 is distinguished especially by the frontal area with distinct tropidium. The punctation of carapace of P. ( Tetinia ) may be of some importance, but with regard to the single species of P. ( Tetinia ) so far known it could be hardly regarded as a diagnostic feature of subgeneric value. Occurrence. See the type species. 164 PALAEONTOLOGY, VOLUME 14 Prantlia ( Tetinia ) minuta Pribyl et Vanek 1962 Plate 20, figs. 1-9, Plate 24, fig. 9; text-fig. 2 a 1962 Prantlia minuta Pribyl et Vanek; pp. 26-30, pi. 1, figs. 1-5, text-fig. 1. Material. More than 120 selected cranidia, 150 pygidia, a great number of free cheeks, and 5 hypo- stomes mostly well preserved in limestones. a b text-fig. 2. Comparison of cranidia of Prantlia ( Tetinia ) minuta Pr. et V. (a), and Prantlia {Prantlia) longula (H. et C.) (b). Dorsal view, about X 15. Remarks. On the basis of a recently found rich material, the description presented by Pribyl and Vanek (1962) can be completed. On the carapace surface two lateral glabellar furrows (Sl5 S2) are clearly discernible: sharp, completely delimiting Lx, S2 much shorter. S3 mentioned by Pribyl and Vanek in most specimens not perceptible. The occipital lobes ill-defined, their separation marked by broadening of occipital furrow only. If well preserved, cranidium and free cheeks display a distinct sculpture: fine punctation, on basal lobes and on the occipital ring combined with scale-like ridges. A marked rather deep punctation to reticulation can be seen on the anterior part of EXPLANATION OF PLATE 20 Figs. 1-9. Prantlia {Tetinia) minuta Pribyl et Vanek, 1962; Uppermost Pridolian. 1, Cranidium (ICh 3313); Tetin, x 10. 2, Cranidium (ICh 3315); Tetin, x 10. 3, Cranidium (ICh 3314); Holyne, x 10. 4, Cranidium and left free cheek (ICh 3310); Svaty Jan, x 10. 5, Cranidium of a large specimen (ICh 3312); Srbsko, X9-5. 6, Hypostome (ICh 3307); Nova Ves, xl2. 7, Pygidium (ICh 3305); Holyne, X 9. 8, Pygidium (ICh 3306); Holyne, x 12. 9, Pygidium of a large specimen (ICh 3303); Tetin, X 9. Figs. 10-11. Prantlia {Prantlia) longula (Hawle et Corda 1847). Kopanina Formation, Reporyje. 10, Pygidium (ICh 3316), X 10. 11, Cranidium (UUG p. 12258), X 12. Palaeontology, Vol. 14 PLATE 20 CHLUPAC, Silurian/Devonian trilobites I. CHLUPAC: SILURIAN/DEVONIAN TRILOBITES 165 fixed cheeks and the genal field of free cheeks. The anterior border proper pitted finely and regularly. Pygidial axis composed of 10 complete rings (plus terminal piece). In adult speci- mens of normal size, 6 ribs are usually developed on the lobes; between the last dis- cernible rib and the axis there is a certain space; PF and TPF on the surface of carapace of adult specimens are shallow, the relief of the lobes being therefore not sharp. Hypostome: anterior lobe oval, only in the abax. part separated by a weak median furrow from the broader (tr.) posterior lobe. The border region extends anterolaterally into broad short anterior wings; lateral wings rounded, very conspicuous posterior wings prolonged into sharp points. Border region, on the whole, flat. During recent collecting, remains of young specimens were found. Even the smallest cranidia encountered, measuring 1 -5-2-0 mm in length do not substantially differ in any way from the specimens of normal size. The smallest pygidia found, 1-0-1 -5 mm in length (sag.) and of a max. breadth 2-0-2-7 mm are in general broader than those of the adult specimens; their pleural lobes are flatter, their PF and IPF are sharper, the border furrow is deeper and the border is somewhat broader and flatter. Measurements. The smallest cranidium found is 1-5 mm in length (sag.), the largest 4 8 mm. The smallest pygidium is 10 mm long, breadth being 2 0 mm; the length of the largest pygidium is 5 mm, its breadth being 7-5 mm. Occurrence. P. ( T .) minuta characterizes an important horizon of small thickness (not exceeding 3 m) at the Pridolian/Lochkovian boundary in the Barrandian Area, closely underlying the Warburgella rugulosa rugosa Horizon. However, its occurrence is restricted to a purely carbonate facies that is locally very abundant at the pertinent level. Localities: Nova Ves near Praha, Holyne (north-east of Opatrilka), Reporyje (quarries ‘Na pozarech), environs of Svaty Jan pod Skalou and further localities as Morina, Srbsko, Tetin, etc. (Chlupac et a/. 1970). Genus warburgella Reed 1931 Type species. Asaphus stokesi Murchison 1839. Remarks. Emended diagnosis and discussion of this genus was presented by Ormiston (1967). Within the framework of the above genus Balashova (1968) has recently separated the subgenus Warburgella ( Podolites ) Bal., which, however, in most of the diagnostic features given by Balashova (1968, p. 102) agrees with the nominate subgenus (see redescription of the type species W. stokesi by Whittard 1938), i.e. breadth of pre- glabellar field, configuration of the border, course of tropidium, sharp incision of S1? size of palpebral lobes, configuration of occipital ring, narrow pygidial axis, and short postaxial ridge. The value of some further diagnostic features given by Balashova is questionable as they are either individually variable (sculpture) or varying during the ontogenic development, sometimes also influenced by the state of preservation (sharp- ness of the border line, etc.). Of the characteristics which can be regarded, although with reserve, as really diagnostic for W. ( Podolites ), there remains only the presence of a transverse ridge posterior to the anterior border furrow (before tropidium) and 166 PALAEONTOLOGY, VOLUME 14 a lower number (8) of thoracic segments; the latter feature, however, should be still more thoroughly verified by more finds of complete carapaces of adult specimens. Occurrence. Lower Silurian (or even Ashgillian) to early Lower Devonian. Europe (Podolia, Barrandian area, the Rheinishes Schiefergebirge, Poland), North Africa (Morocco), North America (Canadian Arctic). Warburgella ( Podo/ites ) rugulosa rugosa (Boucek 1934) Plate 21, figs. 1-14 1934 Cyphoproetus rugosus Boucek; pp. 2-3, pi. 1, figs. 7-10. 1963 Warburgella rugulosa (Alth 1874) rugosa (Boucek 1934); G. Alberti, pp. 157-8, pi. 15, figs. 1-6; pi. 16, figs. 1—4; text-fig. lb (here earlier synonymy). 1968 Warburgella ( Podolites ) rugulosa: Balashova, pp. 102-3, pi. 2, figs. 15-23. 1968 Warburgella ( Podolites ) rugosa rugosa: Balashova, p. 104, pi. 2, figs. 10-14. 1969 Warburgella rugulosa maura: G. Alberti, pp. 353-6, pi. 32, figs. 1-11; pi. 33, figs. 5-13; pi. 43, fig. 17; text-fig. 42, 43 bx.z. (here further synonymy). Material. About 300 selected cranidia and more than 200 pygidia, a great number of isolated free cheeks and several hypostomes (all well preserved as external or internal moulds in limestones). Remarks. The recently found material permits the study in greater detail of the indi- vidual variability as well as the changes during the ontogeny. In the first place, sculp- ture appears to be the most variable feature. Even in individuals of the same size and from the same stratigraphic horizon, variability of sculpture, especially marked on glabella, can be observed; some specimens display close-set, rather long curved ridges (cf. PI. 21, fig. 5), or other specimens are frequently found which show rather short and interrupted coarse ridges more widely spaced from each other (PI. 21, fig. 7 and also specimens figured by Alberti 1963, pi. 15, figs. 1-3); others have still sparser ridges which especially in the anterior part of glabella gradually die out (PI. 21, fig. 4); some show fine, densely crowded short ridges (PI. 21, fig. 3) and a sculpture resembling that of the specimens figured by Alberti (1969, pi. 32, figs. 1-11) from Morocco and designated as W. rugulosa maura Alberti. Finally, in the new material, specimens were also found, the ridges of which are very weak resembling in sculpture the cranidia of W. cf. baltica Alberti figured by Alberti (1963, pi. 15, figs. 10-11) from the Baltic Silurian. As on glabella, also on pygidium, especially on pygidial ribs, the size and density of granules EXPLANATION OF PLATE 21 Figs. 1-14. Warburgella ( Podolites ) rugulosa rugosa (Boucek 1934); Lower Lochkovian. 1, Cranidium of the youngest specimen found (ICh 3286); Radotin Valley, X 30. 2, Pygidium of a young speci- men (ICh 3285); Radotin Valley, x25. 3, Cranidium (ICh 3287); Karlstejn, Xl5. 4, Cranidium (ICh 3295); Svaty Jan, x 14-5. 5, Cranidium (ICh 3294); Holyne, X 14. 6, Cranidium (ICh 3290); Koukolova Hora, x 14. 7, Cranidium of a large specimen (ICh 3281); Karlik, X 12. 8, Hypostome (ICh 3293); Srbsko, x 11. 9, Left free cheek (ICh 3282); Karlik, X 11. 10, Pygidium (ICh 3279), slightly compressed; Karlstejn, X 10. 11, Pygidium (ICh 3280); Lejskov, xll. 12, Pygidium (ICh 3278); Koukolova Hora, xll. 13, Pygidium of a large specimen (ICh 3277); Srbsko, x 10. Palaeontology, Vol. 14 PLATE 21 CHLUPAC, Silurian/Devonian trilobites I. CHLUPAC: SILURIAN/DEVONIAN TRILOBITES 167 markedly varies (cf. PI. 21, figs. 10-13); the cranidia with fairly coarse sculpture belong to pygidia with rather marked granulation, and inversely. As the whole material was collected in the sections which had been studied in detail, its assignment to the same stratigraphic horizon is indubitably correct and it is evident that the variations of sculpture do not depend on the stratigraphic level of the occur- rence. At a certain locality and especially in a definite lithological type of rocks, speci- mens frequently prevail which show a certain type of sculpture (in the facies of dark platy limestone individuals with a coarser sculpture predominate, while in light organo- detrital limestones specimens with sparser or finer sculpture occur). However, at the same locality and in the same bed, specimens showing various deviations of sculpture can often also be found. From the mode of occurrence it may be concluded that the sculpture was evidently influenced in the first place by purely local microfacies con- ditions and that this variability is of individual character and depends on ecological conditions. In addition, certain changes in the sculpture can also be established during the post-larval ontogenic development (the younger specimens usually display a more close-set and finer sculpture); these variations, however, are less conspicuous. Considering the results of the above observations it can be stated that the erection of subspecies within the species Warburgella rugu/osa (Alth) on the basis of minor varia- tions of sculpture only, does not appear as fully justified. On the other hand, variability of sculpture also has certain limits: for instance, none of the specimens found in the Barrandian Basin agrees in its sculpture with those described as Warburgella rugu/osa rhenana Alberti from the Rhineland or with W. rugu/osa canadensis Ormiston from the Canadian Arctic which both evidently represent true subspecies. The recently found material makes a study of ontogeny possible. The smallest cranidia found (ICh 3284, 3286) 0-7-1 -0 mm in length, compared with adult specimens, have substantially narrower and longer glabella with sharp Sx and S2 but with a weak tropidium and a transverse ridge posterior to the anterior border furrow (PI. 21, fig. 1). In cranidia measuring T6-T8 mm in length (e.g. ICh 3288), glabella is still relatively long, but the tropidium and the transverse ridge are already more prominent. During further development (cranidia 2-5-3-0 mm long (sag.) (PI. 21, figs. 3-6)), glabella broadens, especially in the posterior part, assuming thus the characteristic usual shape, and the development proceeds in the way described by Alberti (1969, pp. 355-6). The specimens of this stage of growth mostly prevail in number. In specimens of larger size (length of cranidium 4-6 mm) the difference between the anterior and posterior parts of glabella diminishes, the glabella becoming rather subquadrate in outline (cf. PI. 21, fig. 7). Striking variations can be observed on pygidia during the ontogenic development. The smallest pygidia found 0-5-0-8 mm in length (PI. 21, fig. 2) show a strikingly sharp relief, deep incised PF, 6-7 prominent ribs on the lobes and a markedly differentiated border; IPF of the anterior ribs, are characteristically abax. bent backwards in crescentic form, continue on to the border (typical larval feature of proetids). Pygidia 1 -5-2-0 mm long are distinguished by a major breadth (ratio length to breadth = about 1:2), flatter lobes, less incised PF and IPF and a smaller number of ribs (5-6) on the lobes (PI. 21, figs. 10-12). Pygidia of this size are most frequent and correspond to cranidia 2-3 mm long. In major pygidia, of lengths exceeding 2-5 mm, a tendency towards prolongation of the pygidium and continuing shallowing and reduction of PF and IPF 168 PALAEONTOLOGY, VOLUME 14 in the posterior parts of the pygidial lobes can be observed, so that only 2-3 complete anterior ribs are prominent, IPF being only very weak (see PI. 21, fig. 13). From the above notes it follows that in evaluating the diagnostic features within Warburgel/a rugulosa (Alth) it is necessary to proceed with considerable caution and to use specimens derived from various environments and of different stages of onto- genic development. In this connection the distinguishing of W. ( P .) rugulosa rugulosa (Alth) and W. ( P .) rugulosa rugosa (Bouc.) on the basis of diagnostic features given by Balashova (1968) appears as not fully justified and insufficient for an objective dif- ferentiation. However, as the problem of the types of the nominate subspecies W. (P.) rugulosa rugulosa (Alth) has not yet been definitively solved (the original material being lost?), the present author retains, for the sake of objectiveness, the designation W. ( P .) rugulosa rugosa (Boucek) for the material from the Barrandian area, pointing out that a possible identity with the nominate subspecies (cf. Alberti 1969) could be proved only after the establishment of the lectotype or neotype of the nominate subspecies. Occurrence in the Barrandian. Warburgel/a (P.) rugulosa rugosa (Bouc.) forms a sig- nificant horizon in the early Lower Devonian (Lower Lochkovian), approximately corresponding to the Monograptus uniformis Zone. The above species was found at practically all localities where the Silurian/Devonian boundary was studied in detail: Karlstejn-Budnanska skala (type locality), Klonk near Suchomasty, Certovy Schody, Lejskov, Koukolova hora, Tetin, Kosov, Srbsko, various localities in the environs of Svaty Jan pod Skalou, Lodenice-Branzovy, Reporyje, Holyne, Nova Ves, Praha- Podoli, Cerna rokle gorge below Barrandov, localities in the Radotin valley, Vonoklasy, Karlik, and others (Chlupac et al. 1970). It is important that W. ( P .) rugulosa rugosa (Boucek) is abundant at the same level in the facies of dark platy limestones as well as in organodetrital facies, so that it is one of the most suitable fossils for correlation in the boundary interval. Subfamily prionopeltinae Pribyl 1946 Genus prionopeltis Hawle et Corda 1 847 Type species. Phaeton archiaci Barrande 1846. Prionopeltis striatus troilus Hawle et Corda 1847 Plate 22, figs. 1-6; Plate 23, figs. 7-10; text-fig. 3a, b 1847 Prionopeltis troilus Hawle et Corda, p. 124. Lectotype. Cranidium with free cheek (NM 361/67). Type locality. Kolednik near Beroun. Horizon. Lower part of the Pridoli Formation, Upper Silurian. Diagnosis. Subspecies of P. striatus differing from the nominate subspecies in a shorter concave preglabellar field, the anterior part of fixed cheeks with convexity of their own, interrupted in the median part only anterior to the frontal lobe of the glabella (in P. striatus striatus the preglabellar field is flat and fuses completely with the anterior part of fixed cheeks), wider and deeper border furrow and the sculpture on glabella where, I. CHLUPAC: SILURIAN/DEVONIAN TRILOBITES 169 in addition to small ridges, granules are also present (in the nominate subspecies ridges only). Remarks. Although Hawle’s and Corda’s (1847) description is not adequate, the lectotype of P. troilus H. et C. differs from P. striatus striatus H. et C. from the Kopanina Formation and, on the contrary, agrees with the abundant representative of Prionopeltis frequently found in the Pridoli Formation. The lithological character of the rock in which the lectotype has been preserved, furnishes evidence that the assignment to the Pfidolian is correct. A close relationship to P. striatus striatus (Barr.) is of course in- dubitable, the differences being of subspecific rank only; P. striatus troilus is incon- testably a direct descendant of the nominate subspecies. text-fig. 3. Comparison of cranidia: a-b, Prionopeltis striatus troilus H. et C. (a, dorsal view; b, lateral view from the left), c-d, Prionopeltis striatus striatus H. et C. (c, dorsal view; d, lateral view from the left), x 1 1. On the recently found material some changes during the post-larval ontogenic development can be traced : the young specimens (e.g. ICh 3264, 3260) have a somewhat longer glabella, deeper glabellar furrows and a shorter preglabellar field (PI. 22, figs. 1 , 6). Of other subspecies, P. striatus praecedens (Boucek 1934) is distinguished by a long (sag.) preglabellar field, more convex pygidial lobes with shorter marginal spines. P. striatus incisus Kegel 1928 from the Upper Silurian of the Harz Mts. also shows a longer preglabellar field and pygidium with a narrower axis, broader lobes with ribs less curved backwards, and by longer and narrower marginal spines. Occurrence. Pridoli Formation; especially abundant in the lower part ( Monograptus ultimus Zone), particularly in purely carbonate (organodetrital) facies. Localities: Kosov and Jarov near Beroun (in the earlier collections these localities were both covered by the term Dlouha hora or Kolednik), Zadni Kopanina (the south-western wall of the quarry Horni Dezortuv lorn, occurrence together with Scharyia nympha sp. nov.), Srbsko-Na Brici, Lodenice-Bubovice (ancient small quarries at the road), fteporyje, etc. 170 PALAEONTOLOGY, VOLUME 14 Subfamily tropidocoryphinae Pribyl 1946 Genus wolayella Erben 1966 Type species. Wolayella wolayae Erben 1966. Wolayella ranuncula sp. nov. Plate 19, figs. 12, 13; Plate 22, fig. 9; text-fig. 4 Derivation of name. From the Latin ranuncula, small frog. Holotype. Cranidium (ICh 3270) figured on Plate 22, fig. 9. Type locality. Kosor, quarry in Cerna rokle. Horizon. Upper part of the Lochkov Formation, early Lower Devonian (Upper Lochkovian). Material. Seven cranidia preserved in limestone. Description. Cranidium distinguished by a strong convexity, short glabella and long pre- glabellar field. Glabella roundedly subtrapezoidal in outline, anteriorly broadly rounded, gently arched. Its length (sag.) equals the maximum breadth at the occipital furrow. Dorsal furrows run around glabella in abaxially convex arches, showing a weak adax. bend in the anterior third only. Weakly impressed glabellar furrows: Sx indicates the separation of the basal lobe which has a slight convexity of its own, very weak S2 appears in the anterior third of the glabella. Owing to the gentler arch- ing of lateral lobes and L2, the fronto- median part of glabella is more prominent, and consequently, the glabella becomes roof-like with a weak longitudinal keel in the axis. Occipital furrow sharp, less im- pressed in the proximity of dorsal furrows. Occipital ring moderately arched with a small median tubercle and indistinctly separated occipital lobes. Preglabellar field long text-fig. 4. Wolayella ranuncula sp. nov., crani- dium: a, dorsal view; b, lateral view from the left, xll. EXPLANATION OF PLATE 22 Figs. 1-6. Prionopeltis striatus troilus Hawle et Corda 1847; Pridoli Formation, Kosov (figs. 1-3, 5-6), Zadni Kopanina (fig. 4). 1, Cranidium of a younger specimen (ICh 3260); Kosov, x 10. 2, Crani- dium of a specimen of normal size (ICh 3263); Kosov, x 10. 3, Cranidium of a larger specimen (ICh 3262); Kosov, x 10-5. 4, Cranidium of a large specimen (ICh 3265); Zadni Kopanina, x 10-5. 5, Cranidium (ICh 3261); Kosov, X 10-5. 6, Two cranidia and left free cheek of young specimens (ICh 3264); Kosov, xl2. Figs. 7-8. Prionopeltis striatus striatus Hawle et Corda 1847; Kopanina Formation, Jarov. 7, Crani- dium of a smaller specimen (ICh 3318), xll. 8, Cranidium of a larger specimen (ICh 3317), xll. Fig. 9. Wolayella ranuncula sp. nov.; Upper Lochkovian, Kosor. Cranidium, holotype (ICh 3270), X 11. Palaeontology, Vol. 14 PLATE 22 CHLUPAC, Silurian/Devonian trilobites I. CHLUPAC: SILURIAN/DEVONIAN TRILOBITES 171 (sag.), its length = two-thirds of the length of glabella, having convexity of its own sloping anteriorly. The anterior border furrow broad and incised, anterior border narrow, wall-like, upraised, with one or two weak parallel lines. Facial sutures: anterior branch long, divergent at an angle of 20° to the sag. axis, narrowly rounded, y and e at a certain, almost equal distance from the dorsal furrows. Palpebral lobe long {exsag.), narrow, only slightly curved abax. Sculpture on glabella, occipital ring, and preglabellar field, fine scale-like ridges mostly parallel to the anterior margin of cranidium. On glabella, the ridges on the fronto- median part form anteriorly curved arches, on the lateral lobes, they run rather trans- versely. In the site of the assumed tropidium on the preglabellar field, some of the ridges are more prominent, but the tropidium proper is not developed as a continuous line (e.g. ICh 3270, ICh 3271). Measurements (in mm) Cranidium (ICh 3270) — Holotype: length 4-5; length of glabella 2 0; maximum breadth of glabella 2-0. Cranidium (ICh 3273) — Paratype 3-8; 1-8; 1-8. Remarks. The assignment to Wolayella Erben is based especially on the shape of glabella, the course of dorsal furrows and configuration of preglabellar field and pal- pebral lobes. Our species differs from W. wolayae Erben 1966 and W. maura Alberti 1966 in the vaulting of glabella (particularly signs of Sx and S2 and the keel-like con- vexity of frontomedian part), longer preglabellar field without any pronounced tro- pidium and in a much finer ridge sculpture. A long similarly inflated preglabellar field can be observed in the single cranidium described by Pribyl (1966) as Unguliproetus globosus Prib., which, however, has a considerably convex and oval glabella without visible glabellar furrows, a weak anterior border furrow and a broader border. From the Lochkovian, a single pygidium of tropidocoryphid character was described by Barrande (1872) as Proetus heteroclytus Barr, (see remarks to Tropidocare index sp. nov.), later it was tentatively assigned to Tropidocoryphe Novak, but Alberti (1969, p. 326) has recently excluded it from this genus. As from the Upper Lochkovian no other tropidocoryphid trilobite has so far been known, it could be assumed that the pygidium described by Barrande could be conspecific with Wolayella ranuncula sp. nov. This possibility has not so far been supported by any find of pygidia of Wolayella ; therefore, for the sake of objectivity, the cranidia at the present state of knowledge are to be designated by a separate name. Occurrence. W. ranuncula sp. nov. has so far been known from the Radotin and Kosor facies of the Upper Lochkovian ( Monograptus hercynicus Zone), from the localities Kosor (ancient quarries in the north-western slope of the gorge Cerna rokle) and Velka Chuchle-Pfidoli (sections described by Chlupac 1953). Subfamily scharyiinae Osmolska 1957 Genus scharyia Pribyl 1946 Type species. Proetus micropygus Hawle et Corda 1847. 172 PALAEONTOLOGY, VOLUME 14 Scharyia nympha sp. nov. Plate 23, figs. 1-6; text-fig. 5 Derivation of name. From the Latin nympha , goddess of spring. Holotype. Cranidium (ICh 3237) figured on Plate 23, fig. 2. Type locality. Zadni Kopanina, Barrandian Basin. Horizon. Lower part of the Pridoli Formation, Upper Silurian. Material. Ten selected cranidia, 30 pygidia, several free cheeks preserved in limestones. Description. Glabella conical, tapering anteriorly, narrowly rounded anteriorly; con- vexity of glabella sag. moderate, tr. steeper. Of glabellar furrows, only Sx in the posterior third of glabella weakly impressed. Dorsal furrows sharp, converging anteriorly, markedly deepening in the posterior part and before the frontal lobe. In the anterior i of glabella they are gently curved adax.— this appears as constriction of the foremost part of glabella. Occipital furrow deep, uniformly incised during its whole course. Occipital ring moderately tapering laterally, highly arched, with prominent median tubercle near the posterior margin. Preglabellar field sag. long (§ of the length of glabella), sloping anteriorly. Anterior border furrow sharp and narrow during its whole course. Anterior border narrow, gently wall-like upraised, with one or two parallel lines near the anterior margin. Anterior part of fixed cheeks falling antero-laterally, broad (tr.). Palpebral lobe large, strongly curved abax., separated from the remaining part of the fixed cheeks by a furrow, more incised backwards, parallel to sag. axis. The posterior part of fixed cheek not preserved. Facial suture: Anterior branch con- siderably divergent (at an angle of approx. 35° to sag. axis), /? narrowly rounded, y fairly distant from dorsal furrows, e at a lesser, nevertheless considerable, distance. Surface of cranidium, except for the anterior border, carries prominent tubercles of unequal size and individually variable spacing (cf. difference between cranidium figured on PL 23, fig. 1, and that in fig. 2). In some specimens, the strikingly larger granules on glabella are arranged into longitudinal rows. A conspicuous row of granules rims the palpebral lobe. The free cheeks show a relatively broad inflated genal field, deep anterior and posterior border furrows and a markedly separated lateral border. Genal spines rather short, with a longitudinal depression. Eyes large, convex (visual surface not preserved). On genal field sparse prominent granules. Pygidium half-elliptical in outline with an arched axis rapidly tapering backwards, composed of 7-8 complete rings (plus articulation half-ring). The axis terminates at a considerable distance from the posterior margin, running out into a postaxial ridge EXPLANATION OF PLATE 23 Figs. 1-6. Scharyia nympha sp. nov.; Lower Pridolian, Zadni Kopanina. 1, Cranidium (ICh 3236), x25. 2, Cranidium, holotype (ICh 3237), x 22. 3, Cranidium (ICh 3209), x23. 4, Pygidium (ICh 3231), x24. 5, Pygidium (ICh 3234), x 18. 6, Pygidium (ICh 3232), x33. Figs. 7-10. Prionopeltis striatus troilus Hawle et Corda 1847; Lower Pridolian, Kosov (figs. 7, 9-10), Reporyje (fig. 8). 7, Pygidium (ICh 3259), xll. 8, Pygidium (ICh 3268), xll. 9, Pygidia and uncomplete cranidium (ICh 3264), x9. 10, Pygidium of a young specimen (ICh 3258), xll. Palaeontology, Vol. 14 PLATE 23 CHLUPAC, Silurian/Devonian trilobites I. CHLUPAC: SILURIAN/DEVONIAN TRILOBITES 173 rapidly tapering backwards. Ring furrows deep and wide. On the rings, prominent granules are developed, of which the larger, in the lateral parts of the rings, are arranged into 2-3 rows on both sides of the axis. Pygidial lobes fall relatively steeply towards the border, carrying 5-6 ribs separated by sharp PF. 1PF almost equally incised as PF, divide the ribs in their whole course into two bands, in the anterior ribs the anterior band being broader than posterior. On the ribs, prominent granules of unequal size text- fig. 5. Scharyia nympha sp. nov.: a, cranidium, dorsal view; b, cranidium, lateral view from the left; c, pygidium, dorsal view; d, pygidium, lateral view from the right. All figures x 30. are developed. The major of them, similarly as those on the axis, are arranged into longitudinal rows; analogous sparse granules also occur on the border. Border furrow weak, represented by a depression in which PF and IPF die out. The border relatively narrow, distinctly differentiated from the lobes, weakly wall-like upraised. Measurements (in mm) Length of cranidium Length of glabella Cranidium (ICh 3237) 1-7 0-8 Cranidium (ICh 3236) 1-5 0-7 Cranidium (ICh 3209) 1-9 10 Pygidium (ICh 3231) length 1-5 maximum breadth 2-4 (approx.) Pygidium (ICh 3235) 1-2 2-2 174 PALAEONTOLOGY, VOLUME 14 Remarks and relations. Scharyia micropyga micropyga (Hawle et Corda 1 847) from the lower part of the Kopanina Formation differs especially in the glabella more con- spicuously tapering anteriorly with well-visible glabellar furrows and a much finer uniform granulation of carapace. The pygidium is broader, its axis tapering more rapidly backwards, reaching more closely to the posterior margin, its PF and IPF are less impressed, its border furrow is deeper, and the sparser granules on the carapace are smaller in size, or even are absent on some specimens. The early Lower Devonian Scharyia august a Pribyl 1966 from the Lochkovian has a broader glabella rapidly tapering anteriorly with well-perceptible glabellar furrows (Si deeply incised) and finer granulation. The pygidial axis has more rings (8-9), lateral lobes show a stronger con- vexity of their own, ribs are less arched, PF and IPF are substantially less incised, the surface of the pygidial carapace is almost smooth. The younger Lower Devonian Scharyia vesca Pribyl 1966 from the Pragian agrees with our species in coarsely granulated cranidium, its glabella, however, is broader and the anterior border furrow unsharp (the only one known cranidium of this species is otherwise preserved as a negative only, not permitting a comparison in details); the pygidium of Sch. vesca has an axis of 9 rings, tapering more rapidly backwards, broader border furrow and quite sporadic large granules. Sch. brevispinosa Pribyl 1967 from the boundary beds between the Lower and Middle Devonian has a lesser number of ribs on pygidial lobes, broader border and a denticulate posterior margin. Occurrence. Scharyia nympha sp. nov. is abundant in the basal part of the Pridoli Formation ( Monograptus ultimas Zone) at the locality Zadni Kopanina (the southern wall of the so-called Upper Dezort’s quarry). It is concentrated in the beds of grey, granular, finely organodetrital limestones with a rich trilobite fauna, especially Priono- peltis striatus troilus H. et C., and the very abundant index graptolite Monograptus ultimas Per. It is probable that the described species also occurs in the Upper Pridolian {Monograptus transgrediens Zone); locality Lodenice-Bubovice and Karlstejn (yard of the house no. 132 on the left bank of the river Berounka). Family odontopleuridae Burmeister 1843 Subfamily miraspidinae Richter et Richter 1917 Genus ceratocephala Warder 1838 Type species. Ceratocephala goniata Warder 1838. Ceratocephala lochkoviana sp. nov. Plate 24, figs. 1-8; text-fig. 6 1886 Acidaspis vesiculosa : Novak, pp. 17 and 21. 1962 Ceratocephala (C.) vesiculosa'. Pribyl et Vanek, p. 44. Derivation of name. Name derived from the Lochkovian Stage. Holotype. Pygidium (ICh 3184) figures on Plate 24, fig. 8. Type locality. Klonk near Suchomasty. Horizon. Lower part of the Lochkov Formation ( Monograptus uniformis Zone), early Lower Devonian. Material. Forty cephala, 14 pygidia, some thoracic segments and one hypostome preserved in limestone. I. CHLUPAC: SILURIAN/DEVONIAN TRILOBITES 175 Distinction. Carapace agrees in the main features with C. vesiculosa (Beyr.) the descrip- tion of which was given by Bruton (1968). The differing features are as follows: median glabellar lobe is somewhat narrower and less convex (tr.), S2 is more markedly incised, and wider than Sl5 dorsal furrows are indicated by a weak but discernible depression, so that glabellar lobes do not fuse with fixed cheeks as completely as in C. vesiculosa. text-fig. 6. Comparison of pygidia : a, Ceratocephala verneuiti (Barrande) ; b, Ceratocephala lochkovianci sp. nov. ; c, Ceratocephala vesiculosa (Beyr.). Dorsal views, about x4. In C. lochkoviana, granulation of cephalon varies; in addition to the specimens with close-set and prominent granulation resembling that of C. vesiculosa e.g. ICh 3183, ICh 3186, and ICh 3208 (PL 24, figs. 4, 5), there occur in the same beds specimens with substantially finer granulation where rather large granules are only sparsely disseminated e.g. ICh 3185, 3187 (PI. 24, fig. 2). Between these two extremes, in the same layer, transitional types also exist e.g. ICh 3185 (PI. 24, fig. 1) which furnish evidence that the variability is individual, appearing within the same species. The pygidia of C. lochkoviana substantially differ from those of C. vesiculosa ; they are distinguished by much narrower spines and finer ‘barb-like’ spinules, terminal axial ring distinctly separated from the median spine, and by finer granulation. The pygidium of C. lochkoviana in addition to median spine, also carries on both sides three spines of which the second is the longest, corresponding in breadth to the median one, the 176 PALAEONTOLOGY, VOLUME 14 third, outer spine, being strikingly smaller and shorter, but nevertheless longer than that in C. vesiculosa. Hypostome analogous to that of C. verneuili (Barrande), being, however, longer (sag.). Remarks. In addition to C. vesiculosa (Beyr.) our species is closely related to the older C. verneuili (Barrande 1946) from the Kopanina Formation. The cephalons of C. loch- koviana differ from this species particularly in their coarser variable granulation and, in some cases, in a more prominently curved Sx. Pygidium of C. lochkoviana is dis- tinguished by a fairly shorter third (outer) lateral spine and longer (sag.) terminal axial ring, flatter lateral lobes and less uniform granulation (in C. lochkoviana, a regular row of granules rims the anterior margin). The differences are shown in text-fig. 6. Summarizing it can be stated that C. lochkoviana represents a certain connecting link between the older C. verneuili (Barr.) and the younger C. vesiculosa ; this leads to the conclusion that C. verneuili — C. lochkoviana — C. vesiculosa form a direct phylogenic line to which the Wenlockian C. barrandei (Fletcher in Salter 1853)=C. rara (Barrande 1872) with a greater number of pygidial spines (9) may also belong. It should be noted that the differences in the individual species are more pronounced on pygidia, the cranidia, however, being very similar to each other. The finds of pygidia being not frequent, the above fact can cause difficulties in identification. Occurrence. C. lochkoviana sp. nov. occurs in various facies of the Lochkovian, its typical representatives derive from the Radotin and Kosor facies where they appear only rarely. However, the type locality, Klonk near Suchomasty, is an exception. There, C. lochkoviana is relatively abundant in the bed 95, in the upper part of the Monograptus uniformis Zone, occurring together with Tropidocare index sp. nov. Of further localities in the Lower Lochkovian, the following should be mentioned: Karlstejn-Budhanska skala, Karlik, Reporyje, Nova Ves near Butovice, Holyne, Koukolova hora, etc. (Chlupac 1970). In the Upper Lochkovian, finds have been made especially in the Cerna rokle gorge near Kosor, from where no pygidium has so far been recognized, so that the specific identity, although very probable, has not yet been unequivocally proved. REFERENCES alberti, g. k. b. 1963. Zur Kenntnis rheinisch-herzynischen Mischfaunen (Trilobiten) im Unterdevon. Mitt. Geol. Staatsinst. Hamburg, 32, 148-59, pis. 15-16. 1969. Trilobiten des jtingeren Siluriums sowie des Unter- und Mitteldevons. I. Abh. Senckenbg. Naturf. Ges. 520, 1-692, pis. 1-52. balashova, e. a. 1968. Trilobity skalskogo i borscovskogo gorizontov Podolii. In: Silurijsko-devon- skaja fauna Podolii, 95-123, pis. 1-3. EXPLANATION OF PLATE 24 Figs. 1-8. Ceratocephala lochkoviana sp. nov.; Lower Lochkovian, Klonk (figs. 1-2, 4-8), Upper Lochkovian, Kosor (fig. 3). 1, Cranidium (ICh 3185), x3. 2, Cranidium (ICh 3187), x3. 3, Cranidium (ICh 3207), x2-5. 4, Cranidium (ICh 3186), x3. 5, Cranidium (ICh 3183), x4. 6, Hypostome (ICh 3182), x8. 7, Pygidium (ICh 3188), x5. 8, Pygidium, holotype (ICh 3184), x4. Fig. 9. Prantlia (Tetinia) minuta Pribyl et Vanek 1962; pygidium (ICh 3304); Uppermost Pfidolian, Holyne, x9. Palaeontology, Vol. 14 PLATE 24 CHLUPAC, Silurian/Devonian trilobites 177 I. CHLUPAC: SILURIAN/DEVONIAN TRILOBITES barrande, J. 1852. Systeme Silurien du centre de la Boheme, I Trilobites. Prague and Paris. boucek, b. 1934. Prispevek k poznani trilobitu ceskeho gotlandu (II). Rozpr. Ces. Akad. 44, 34, 1-7, pi. 1. bruton, d. l. 1968. A revision of the Odontopleuridae (Trilobita) from the Palaeozoic of Bohemia. Skr. Norske Vidensk. Akad. 25, 1-73, pis. 1-11. chlupac, i. 1953. Stratigraficka studie o hranicnich vrstvach mezi silurem a devonem ve strednich Cechach. Sbor. Ustr Ust. geol. 20, odd. geol. 277-380, pis. 1-5. et al. 1970 (in press). The Silurian-Devonian boundary in the Barrandian Area of Czechoslovakia. Bull. Canad. Petrol, geol. erben, h. k. 1966. fiber die Tropidocoryphinae (Tril.)-Liefg. I. N. Jb. Geol. Palaont. Abb. 125, 170- 211, pis. 19-21. hawle, i. and corda, a. j. c. 1847. Prodrom einer Monographie der bohmischen Trilobiten. Abb. kgl. bohm. Ges. \ Viss. 5, 1-176, pis. 1-7. horny, r. and bastl, f. 1970 (in press). Type specimens of fossils in the National Museum Prague. I. Trilobita. Mus. of Nat. Hist. Prague. kegel, w. 1928. fiber obersilurische Trilobiten aus dem Harz und dem Rheinischen Schiefergebirge. Jb. Preuss. geol. Landesanst. 48, 616-47, pis. 31-32. moore, r. c. (ed.). 1959. Treatise on invertebrate paleontology. Part O, Arthropoda-1 . Geol. Soc. Am. and Univ. Kansas Press. novak, o. 1886. Zur Kenntnis der Fauna der Etage F-fx in der palaozoischen Schichtengruppe Bohmens. Sitz.-Ber. bohm. Ges. Wiss, 1886, 1-26, pis. 1-2. ormiston, a. r. 1967. Lower and Middle Devonian Trilobites of the Canadian Arctic Islands. Geol. Surv. Canada Bull. 153, 1-148, pis. 1-17. pribyl, a. 1946. Prispevek k poznani ceskych Proetidu (Trilobitae). Rozpr. Ces. Akad. 55, 10, 1-37, pis. 1-4. 1966. Proetidni trilobiti z novych sberu v ceskem siluru a devonu. II. Cas. Nar. mus. 135, 1, 49-54, pi. 1. 1967. Die Gattung Scharyia Pribyl, 1946 (Trilobita) und ihre Vertreter aus dem bohmischen Silur und Devon. Spis. big. geol. Dm2. 28, 3, 285-301. and vanek, j. 1962. Trilobitova fauna ceskeho svrchniho siluru (budnanu a lochkovu) a jeji biostratigraficky vyznam. Sbor. Nar. mus. 18B, 2, 25-46, pis. 1-4. whittard, w. f. 1938. The upper Valentian trilobite fauna of Shropshire. Ann. Mag. Nat. hist. 1 1 ser., 1, 85-140, pis. 2-5. IVO CHLUPAC Ustredni ustav geologicky Malostranske nam. 19 Typescript received 18 June 1970 Praha 1, C.S.S.R. O 7895 N POLYPORA STENOSTOMA : A CARBONIFEROUS BRYOZOAN WITH CHEILOSTOM ATOUS FEATURES by R. TAVENER-SMITH Abstract. The morphology of Polypora stenostoma sp. nov., a fenestrate cryptostome from the Visean, is described and discussed. Unusual zooecial features suggest that the frontal surface was substantially uncalcified during the active life of a zooid. It is probable that the soft external coverings on this side were depressed by retraction of the vestibular extensor muscles. The consequent decrease in zooidal volume and increase in body fluid pressure would have facilitated extrusion of the tentacles, as in modern anascan cheilostomes. It is there- fore likely that the mechanism for lophophore extrusion now regarded as characteristic of, and peculiar to, the Anasca was also present in a much earlier cryptostome stock. In bryozoa the extrusion of tentacles, a vital function in these animals, is effected by different means in different groups. The mechanism is always fundamentally the same, however, in that a reduction of bodily volume by muscular contraction causes an increase of body fluid pressure, which promotes the extrusion of the lophophore by hydraulic means. In the order Cheilostomata, which ranges from the Cretaceous to the present day, the basic arrangement is that of muscles acting on a frontal membrane, as seen in the suborder Anasca. Although this pattern, and that of the compensation sac which stems from it, are generally accepted as peculiar to the Cheilostomata (Bassler 1953, pp. G147, 149) the frontal morphology of a new species of Polypora from Visean limestone (Dx) at Carrick Lough, County Fermanagh, Ireland, suggests the presence of an essentially similar mechanism in a much earlier stock. In the following paragraphs the new species is described, and the significance of the unusual frontal characteristics examined. SYSTEMATIC DESCRIPTION Order cryptostomata Vine 1883 Family fenestellidae King 1850 Genus polypora M’Coy 1844 Emended diagnosis. Planar, funnel, or cup-shaped fenestrate expansions of radiating, straight, or gently sinuous branches connected by regularly disposed, transverse dis- sepiments. Branches bear three or more rows of zooecial apertures on one side only; dissepiments are sterile. Obverse of branch smooth or with low, longitudinal ridges separating rows of apertures. Ridges may bear low nodes. Reverse smooth, or longi- tudinally striate, with or without nodes. Type species. P. dendroides M’Coy 1844. Tournaisian, Ireland. [Palaeontology, Vol. 14, Part 1, 1971, pp. 178-87, pi. 25.] R. TAVENER-SMITH: CARBONIFEROUS BRYOZOAN 179 Polypora stenostoma sp. nov. Plate 25, figs. 1-10 Type specimens. Holotype: Specimen PD 4858 in the British Museum (Natural History) collection, London. Paratypes: Specimens PD 4859 to PD 4864 in the same collection. Type locality. Limited exposures along the south shores of Carrick Lough, two miles north-west of Derrygonelly village, County Fermanagh, Northern Ireland. Material. The following description is based on examination of thirty-three small zoarial fragments. The largest measured 17x15 mm. Measurements. For every variable listed, twelve measurements were taken from each of fifteen zoarial fragments. Specimen means were then calculated, and the following statistics derived by the method suggested in Tavener-Smith (1966/;, pp. 421-2). The dimensions recorded are illustrated in text-fig. 1. Standard Coejf. of Range Mean deviation variation Fenestrule length 1 -60-2-20 1-86 0-163 8-76 Fenestrule width 0-90-1 -20 1-053 0-089 8-47 Inter-apertural distance (within one row) 0-25-0-32 0-295 0-016 5-51 Inter-apertural distance (measured diagonally) 0-20-0-25 0-235 0-015 6-49 Branch width 0-37-0-50 0-417 0-034 8-16 Zooidal ap. width 0-07-0-10 0-085 0-009 10-88 Dissepiment width 0-25-0-35 0-302 0-030 9-87 Micrometric formula 8— 1 2/4— 6//1 5—1 8 Diagnosis. Polypora with cup-shaped zoarium consisting of strong branches and short, stout dissepiments bound- ing oval or elliptical fenestrules. There are mostly three rows of elongate, slit-like apertures per branch. No carinal nodes. Dimensions of a sample are as stated above. Description. The proximal parts of colonies are cup- shaped (PI. 25, fig. 4), with zooecial apertures on the inner side of the meshwork. Complete structures were probably erect, foliaceous, cup-shaped expansions about 5 cm high. Branches are relatively stout, with a slightly sinuous growth habit (PI. 25, fig. 1). There is no median ridge on the obverse, nor are carinal nodes present. One row of apertures follows the mid-line and is flanked by a row on either side. Although three rows of apertures per branch are commonest, the number may increase to four or five at bifurcations, and diminish to two im- mediately thereafter. Branch widths show correspond- ing adjustment, increasing to as much as 0-7 mm at the point of division, then sharply decreasing to about O text-fig 1. Polypora stenostoma : dimensional measurements, a, fenestrule length; b, fenestrule width; c, interapertural distance (within a row); d, inter-apertural distance (diagonally); e, branch width; /, dissepiment width; g, zooidal aperture width. 35 mm. The reverse is broadly 180 PALAEONTOLOGY, VOLUME 14 rounded (PI. 25, fig. 3) and may be thickly encrusted with secondary skeletal material. Cross-sections of branches are approximately circular. Dissepiments are short, stout, and roughly circular in transverse section. They are slightly depressed below branch level on both sides, though in the proximal region secondary accretions may render the underside more or less flush with branch surfaces. Fenestrules are mostly imperfect oval or elliptical shapes, though they may be rect- angular with rounded extremities. This species is characterized by the presence on the frontal side of each zooecium of an elongate opening extending for much of the chamber length, but narrower than the chamber width. This opening is slightly wider and more rounded at its distal end (where the lophophore was extruded) so that the over-all shape may be described as spatulate (PI. 25, figs. 1, 7). In some cases the proximal part of the opening is narrowed to a slit, while in others this slit is partly closed so that the proximal extremity is isolated as a separate, secondary or accessory aperture, about half the size of the main one (PI. 25, figs. 8, 9). The last condition results in an alternation of larger and smaller openings in a single row, each pair relating to a single zooecium. In some specimens many of the larger or zooidal apertures (so called to distinguish them from the smaller ones) show prominent collar- like peristomes (PL 25, figs. 1, 7) while in others they are sealed by calcite laminae or completely obscured by secondary calcification (PI. 25, fig. 10). Zooecial chambers are compact structures with an elongate-hexagonal plan, enabling them to fit closely together in three rows within a branch. There are from four to seven chambers along the side of a fenestrule, though the number is most commonly five, and less commonly six. Average dimensions of six chambers were: length, 0-35 mm; width, 0T5 mm; height, 0T7 mm. The form, as described above, cannot be assigned to any of the Carboniferous Polypora described by M’Coy from Ireland, nor is there a satisfactory correspondence with any other known species in the genus. It is therefore necessary to introduce a new name for these specimens, and P. stenostoma (oTev6oTopos= narrow-mouthed) is proposed for the purpose. DISCUSSION The peculiarly shaped frontal openings distinguishing this species merit special atten- tion and it is evident that they may have been formed in one of several ways. First, they EXPLANATION OF PLATE 25 Figs. 1-10. Polypora stenostoma sp. nov. 1, Obverse of holotype showing elongate frontal openings and localized areas of heavy secondary encrustation, PD 4858, X 10. 2, Scanning electron micro- graph showing a zooecial aperture of near-maximum size (lower left); one with a proximal slit (upper right) and two with notched outlines (centre and upper left). Small dark patch below notched aperture at upper left denotes position of almost sealed accessory aperture, PD 5312, X 130. 3, Reverse of holotype, PD 4858, x 10. 4, Cup-like proximal part of a colony attached to obverse of an Hemitrypa hibernica fragment, PD 4864, x6. 5, Scanning electron micrograph showing a late stage zooecial aperture with notched outline. Note that the notches persist into the zooecium as grooves, PD 5312, x280. 6, Obverse of zoarial meshwork showing frontal openings with proximal slits, PD 4860, X21. 7, Scanning electron micrograph showing a zooecial aperture at near-maximum size, PD 5312, x250. 8, Scanning electron micrograph showing the stage at which closure of the proximal slit has led to the formation of an accessory aperture, PD 5312, x 285. 9, Scanning electron micrograph showing constriction of the proximal slit by lateral growth, PD 5312, X 245. 10, Scanning electron micrograph of an example in which separation of zooidal and accessory apertures has been achieved, PD 5312, x210. Palaeontology, Vol. 14 PLATE 25 TAVENER-SMITH, Carboniferous bryozoan R. TAVENER-SMITH: CARBONIFEROUS BRYOZOAN 181 could have resulted from the enlargement of normal zooecial apertures by accidental breakage or abrasion. This presupposes that the present openings were of secondary origin and therefore of no relevance to the life of a colony. Secondly, it is possible that the original condition was that in which larger and smaller apertures alternated in a single zooecial row, and that breakage or abrasion led in many cases to the union of pairs, thus forming elongate openings. If so, it might be thought that during life the smaller apertures gave access to brood chambers, or some kind of kenozooid. Thirdly, it may be that the elongate openings were primary structures communicating directly with the zooecium. Taking these possibilities serially: the first fails to constitute a satisfactory explanation. Shape variation between frontal openings, though present, is not great, and there is no sign of mechanical breakage or abrasion. Nor is it likely that the smaller openings, where such are seen, gave access to keno- zooids, for none of these is present. Finally, the absence of brood chambers makes it improbable that the subsidiary apertures were ooeciopores. Elimination of these possibilities in- creases the likelihood that the frontal open- ings communicated directly, and along all their length, with zooecial chambers. This is confirmed by transverse sections which show complete structural continuity between frontal surfaces flanking the opening and the lateral walls of zooecial chambers (text-fig. 2). Where the frontal opening is constricted into two parts, a section through the smaller, proximal, one showed an identical pattern. In outlining the characteristics of the frontal surface three conditions were mentioned. These were, first, the presence of an elongate opening, slightly wider and more rounded distally. Second, cases where the proximal part of the opening is reduced to a slit. Third, replacement of the slit by a small accessory aperture, quite separate from that of the main zooidal orifice. The second condition predominates in the specimens examined (hence the specific name), though the third is also common. The first condition is restricted to the distal parts of the largest fragments, while the third is associated with areas of heaviest secondary encrustation. These tend also to be the most proximal parts, but are not always so, for the progress of secondary calcification was by no means uni- form. Study of the specimens strongly suggests that these three conditions are related stages in a continuum of change ; that the first was characteristic of the younger parts of colonies, and that the other two reflect to an increasing degree the effects of declining vigour. Observation indicates the following sequence: Stage 1. This is envisaged as the condition applicable to normally functioning zooids (text-fig. 3a). The frontal opening is at maximum size, approximating in dimensions to text-fig. 2. Polypora stenostoma : transverse section across branch; drawn from a cellulose acetate peel, a.ap., accessory aperture; o.s.sk., outer secondary skeleton; p.rim, peristome rim; p.sk., primary skeleton; rev.s., reverse surface; sk.r., skeletal rod; z.ap., zooecial aperture; z.ch., zooecial chamber. 182 PALAEONTOLOGY, VOLUME 14 the length and width of the zooecial front. The peristome is a low, arcuate ridge confined to the distal side of the apertural region. Stage 2. With increasing age there appear signs of encroachment by the colonial secondary skeleton. The frontal opening is constricted laterally and, proximal to the zooidal orifice, it is commonly reduced to an elongate slit. The peristome is more strongly developed, and its arc extended (text-fig. 3b). Rounded notches visible on the inner margin of the peristome at this stage probably indicate positions occupied by extended tentacles. Constant extrusion and retraction of these appear to have kept the grooves open, but secondary substance accumulated between them. z.ap. te. n. C. D. text-fig. 3. Polypora stenostoma : plan views showing stages in the reduction of the frontal opening, a.ap., accessory aperture; p.rim, peristome rim; pr.s., proximal slit; te.n., tentacular notch; z.ap., zooidal aperture. Stage 3. Further constriction of the elongate slit led to its closure except at the proximal end, where an accessory aperture formed. With the closure of the slit extremi- ties of the arcuate peristomial ridge united and continued secondary accretion resulted in the formation of a high, circular collar around the aperture (text-fig. 3c-d). Up to eight symmetrically placed notches are visible on the inner margin of the peristome at this stage. Similar features have been reported by other authors in several fenestellid genera and species. In the writer’s opinion the notched, scalloped, or denticulate appear- ance is an ontogenetic effect without taxonomic significance. Stage 4. Continued secondary deposition brought about progressive diminution in the size of the accessory aperture, and its eventual occlusion (text-fig. 3 d, e). At this stage the zooidal orifice itself is, in most cases, already significantly reduced, and its subsequent closure and sealing by secondary laminae soon followed. Stage 5. In the most proximal parts of colonies further skeletal secretion from the exterior eventually led to the complete obliteration of the original frontal structures. A smooth calcite surface resulted, so that the obverse of a branch is indistinguishable from the underside. The reason for the presence of the enlarged frontal opening in P. stenostoma is a matter for conjecture but it is reasonably certain, considering the mode of formation of the fenestellid skeleton (Tavener-Smith 1969) that, except at the zooidal orifice, the opening was covered during life by the soft external mantle of the colony. The presence of the opening must, in fact, have been due to initial calcification in only marginal parts R. TAVENER-SMITH: CARBONIFEROUS BRYOZOAN 183 of the frontal surface. Nevertheless, with the onset of senility the frontal wall progres- sively encroached upon and eventually sealed the opening. It is natural to inquire why the closure was so long delayed and why, during the active life of a zooid, the opening remained unencumbered by secondary skeletal accretions. text-fig. 4. Polypora stenostoma: diagrammatic transverse sections of a zooid to show stages in the calcification of the frontal opening, a. The condition in a vigorously functioning zooid. b. Formation of the proximal slit by lateral encroachment of outer secondary tissue, c. Sealing of the frontal opening, d, Late stage thickening of the frontal secondary skeleton. fr.s., frontal surface; h.coel., hypostegal coelom; i.s.sk., inner secondary skeleton; lon.w., longitudinal wall; man.ep., epithelia of external mantle; o.s.sk., outer secondary skeleton; p.sk., primary skeleton; per., periostracum; rev.s., reverse surface; sk.r., skeletal rod; z.ep., zooidal epithelium. In the Fenestellidae it is inferred (Tavener-Smith 1969, pp. 290-300) that the frontal zooecial wall was deposited partly by the zooidal epithelium, but mainly by the inner mantle epithelium. During early developmental stages it is likely that these layers faced one another close beneath the outer mantle epithelium and colonial periostracum (1969, text-fig. 4a-d). In order to account for the uncalcified frontal opening in P. stenostoma it must be supposed that either the secretory epithelia were absent; or that, though A B 7 c D 184 PALAEONTOLOGY, VOLUME 14 present, they remained non-secretory during the active life of a zooid. The first alterna- tive is unlikely, and the second demands an explanation for the apparent lack of secretory activity. It is possible that the reason for the latter was simply movement. Within the Fenestellidae there is ample evidence that recurrent movement inhibited the deposition of calcite from normally secretory epithelia. For example, in parts of Archimedes and Lyropora colonies it is clear that regular movement of the tentacles prevented the formation of secondary material above the aperture, though massive deposits covered the rest of the frontal surface. The formation of peristomial notches (as in the present species) illustrates the same tendency. If it is true that regular move- ment may inhibit calcification, it would seem logical to suppose that a cessation of movement might permit a resumption of secretory activity. It is therefore possible that in P. stenostoma sustained movement, commencing before the onset of primary calcifi- cation in the frontal region, prevented wall formation there until a late ontogenetic stage when, due to declining vigour, the movement became retarded. Calcification then resumed its normal course so that secondary skeletal material encroached upon and eventually sealed the frontal zooecial opening (text-fig. 4a-d). Deposition of this kind would have been from the middle epithelial layer (inner side of the external mantle) and therefore of colonial origin. The secretory vigour of this colonial tissue would not have been affected by the declining activity of individual zooids and, on the contrary, observations suggest that physiological controls promoted a high rate of external secondary deposition on the frontal surfaces of moribund zooids so that these became thickly coated and eventually sealed. In P. stenostoma the presence of prominent peri- stomial collars indicates that accelerated secondary deposition preceded the death of a zooid, and not the reverse. If regular movement was responsible for the failure to form a complete frontal wall in this species, it is pertinent to inquire into the nature of the movement, and the reason why it did not lead to similar results in other Polypora. Movements affecting the soft frontal tissues are most likely to have been connected with the extrusion and retraction of the lophophore. Such movements would, with advancing age and declining vigour, become sluggish, and it seems likely that this permitted a recrudescence of calcification around the frontal opening which led to its eventual elimination. The distinctive frontal morphology of this species differs from that of other Polypora, and appears to be unique in the Fenestellidae. It may well have arisen as a result of some genetic accident. A malfunction of physiological co-ordinating mechanisms may, for example, have caused the polypide to become operational prior to the formation of the primary frontal wall instead of immediately afterwards. Movement associated with protrusion and retraction of the lophophore may then have inhibited calcification except in the more static peripheral parts of the frontal area. At this point it is relevant to consider whether a musculature basically of fenestellid type would, in its operation, have been likely to cause movement of the soft frontal tissues. Although nothing is certainly known of the soft parts of these extinct organisms, deductive reasoning suggests an affirmative answer. This bryozoan group had affinities with the Cyclostomata, and with certain of the Trepostomata also (Bassler 1953, p. G116; Tavener-Smith 1966r/, p. 196). Indeed, stratigraphic and phylogenetic con- siderations suggest that these orders of Palaeozoic bryozoa derived from a common ancestral stock. In attempting to visualize the apparatus for lophophore extrusion in the R. TAVENER-SMITH: CARBONIFEROUS BRYOZOAN 185 Fenestellidae one cannot, therefore, do better than take as a model Borg’s (1926, pp. 241-4) account of corresponding arrangements in modern cyclostomes, the only surviving representatives of these groups. In doing so it must be recalled that typical fenestellid zooecia differ from those of the Cyclostomata in important respects, notably in having roughly box, as opposed to tubular, shapes and in the presence of a frontal rather than a terminal aperture. These differences become less absolute on closer examination for within the Fenestellidae, and even within Fenestella itself, there is a great diversity of zooecial shape, and though most chambers are box-like, some are sac- or pear-shaped and a few are tubular. It seems possible that tubular zooecia, perhaps derived from phylloporinid predecessors and well seen in early forms such as Archaeo- fenestella Miller, in general gave way to shorter and more compact shapes. These changes must have been accompanied by a migration of the aperture from a distal to a frontal position, in the same way as has been postulated for the Cheilostomata by Silen (1944, pp. 18-24). It is therefore reasonable to suppose that the apertural region of a box-like fenestellid zooecium corresponds morphologically with the distal surface of a tubular cyclostomatous one. This is important in deducing the arrangement of the musculature concerned with lophophore movement. In the Cyclostomata muscular effort in lophophore extrusion is directed towards opening the vestibule. To this end the radially arranged extensor muscles, which are attached proximally to the epithelial lining of the tubular zooecium (Borg 1926, p. 189, fig. 1), are inserted at their distal ends not only along the vestibular walls, but also on to the adjacent distal surface of the zooid (text-fig. 5a). This pattern of musculature, efficient in promoting lophophore extrusion in a tubular zooecium, must have undergone some modification and rearrangement in order to ensure continued efficient functioning as the more compact chamber shapes of the Fenestellidae emerged. But it is likely that the basic pattern remained unchanged, for in the fenestellids muscular effort must still have been directed towards opening the vestibule and, as Silen has pointed out (1944, p. 44), the position of muscle insertions is a conservative anatomical feature. Supposing the system to have retained the over-all characteristics of that in the Cyclostomata, but making due allowance for changes in zooecial morphology, it seems reasonable to con- clude that the arrangement in orthodox fenestellid zooids was similar to that suggested in text-fig. 5b. In P. stenostoma, a form in which the frontal surface was only periphally calcified, it is difficult to see how contraction of muscles of this pattern could have been effected without depressing the soft frontal covers (text-fig. 5c-d). This would have contributed to a diminution in zooidal volume, a rise in body fluid pressure, and the consequent extrusion of the lophophore. It therefore seems likely that there was, in this Palaeozoic species, a mechanism for polypide movement essentially similar to that now regarded as peculiar to, and characteristic of, much later cheilostomes of the sub-order Anasca. It is worth noting that, whereas in the Cyclostomata (and by inference in orthodox cryptostomes also) muscular effort in lophophore extrusion is directed towards expan- sion of the vestibule, and in anascan cheilostomes towards depressing the frontal membrane, in P. stenostoma an hybrid situation probably existed. In that species it seems that a cyclostome-like musculature, acting mainly on vestibular walls and in the presence of a soft frontal surface, caused as an ancillary effect the depression of the frontal cover, thus aiding extrusion of the tentacles. It seems relevant to recall that Borg (1926, p. 231) 186 PALAEONTOLOGY, VOLUME 14 considered the vestibular extensor muscles of cyclostomes and the parietal muscles of cheilostomes (which, in the Anasca, depress the frontal surface) to be homologous. Considering further the matter of structural parallels with the Cheilostomata another, and rather obvious, possibility needs examination, namely that the subsidiary aperture of P. stenostoma may be equivalent to the similarly situated ascopore of certain cheilo- stome genera, such as Microporella. This resemblance must, however, be dismissed as text-fig. 5. Arrangement and operation of vestibular extensor muscles, a, In a typical member of the cyclostomata (after Borg 1926, p. 189, fig. 1). b, Suggested arrangement in a fenestellid. c, Inferred arrangement in Polypora stenostoma (muscles relaxed), d, The same, with muscles contracted, c.w., calcareous wall; coel., coelom; e.man., external mantle; ep., epithelium; ext.mu., extensor muscles; extr.te., extruded tentacles; fr.s., frontal surface; h. coel., hypostegal coelom; i.s.sk., inner secondary skeleton; lo., lophophore; man.ep., mantle epithelia; o.s.sk., outer secondary skeleton; per., periostracum; p.sk., primary skeleton; s.fr.s., soft frontal surface; sk.r., skeletal rod; t.or., terminal orifice; te., tentacle; te.sh., tentacular sheath; tr.w., transverse wall; z.ep., zooidal epithelium. superficial and unimportant, for the accessory aperture of the former represents only a late ontogenetic stage of skeletal development, and was not present in vigorously functioning zooids. The ascopore, on the other hand, is a permanent zooecial feature. Also, the presence of an ascopore implies the presence of an ascus (compensation sac), and there is no reason to believe that such structures existed in P. stenostoma. Mor- phology of the groups concerned suggests that the compensation sac is a specialized modification of a soft frontal surface that was evolved by cheilostomes of the sub-order Ascophora from a more simple condition now seen in the Anasca. Thus, there seems to be no justification for comparing anatomical arrangements in P. stenostoma with those of the Ascophora, but comparison with the Anasca reveals a number of points in common. R. TAVENER-SMITH: CARBONIFEROUS BRYOZOAN 187 Some authors (e.g. Ulrich 1890, p. 333; Bassler 1911, p. 112) have regarded the Cryptostomata as Palaeozoic forerunners of later cheilostomatous bryozoans, and in P. stenostoma the architectural similarity is undoubtedly marked. The presence of erect branches with multiple rows of zooecia, box-like chambers and uncalcified parts of the frontal surface are strongly reminiscent of many anascan genera. But these features, and even the presence of an extrusion mechanism of anascan type, do not necessarily indicate a direct phylogenetic relationship with any part of the Cheilostomata. In a comparatively small group Like the bryozoa the potential morphological range must be genetically limited, and in a vigorously developing stock the emergent pattern of diversity may already, at an early stage, have covered many of the available possibilities, including some which later reappeared as major themes. In the present case the precocious appearance of an anascan-like extrusion mechanism in P. stenostoma apparently exerted no significant influence on cryptostome evolution, and the order became extinct early in the Triassic. It was not until the mid-Cretaceous that anascan cheilostomes with a similar extrusion mechanism appeared, and the long interval devoid of a relevant fossil record presents a serious obstacle to suggestions that the Cheilostomata sprang from cryptostome ancestors. It is more likely, on both morphological and stratigraphic grounds, that early anascan cheilostomes developed from a ctenostome-like stock (Silen 1944). Nevertheless, though the possibility of a simple phylogenetic relationship can be discounted, the probable occurrence of an extrusion mechanism of anascan type in a late Palaeozoic fenestellid species suggests an interesting case of repetitive evolution where none was previously suspected. REFERENCES bassler, r. s. 1911. The early paleozoic bryozoa of the Baltic Provinces. Bull. U.S. Nat. Mus. 77, xxi+382 pp. 1953. Bryozoa. moore, r. c. (ed.), Treatise on invertebrate paleontology. Part G, xiii+253 pp. Kansas. borg, f. 1926. Studies on Recent cyclostomatous bryozoa. Zcol. Bidr. Upps. 10, 181-507. silen, l. 1944. Origin and development of the cheilo-ctenostomatous stem of bryozoa. Ibid. 22, 2-59. tavener-smith, r. 1966a. Ovicells in fenestrate cryptostomes of Visean age. J. Paleont. 40, 190-8. 1966 b. The micrometric formula and the classification of fenestrate cryptosomes. Palaeontology , 9, 413-25. 1969. Skeletal structure and growth in the Fenestellidae (Bryozoa). Ibid. 12, 281-309. ulrich, e. o. 1890. Paleozoic bryozoa. III. geol. Surv. 8, 283-688. R. TAVENER-SMITH Department of Geology The Queen’s University Belfast, BT7 INN Typescript received 20 May 1970 Northern Ireland TRISTICHOGRAPTUS , A TRISERIAL G RAPTOLITE FROM THE LOWER ORDOVICIAN OF SPITSBERGEN by R. A. FORTEY Abstract. The structure and development of Tristichograptus [formerly Trigonograptus ] ensiformis (J. Hall) is described, from relief material, from the Lower Ordovician Valhallfonna Formation, Spitsbergen. It is the only known triserial graptolite, but appears ‘biserial’ when flattened. The relation of Tristichograptus to Phyllo- graptus, Tetragraptus, and biserial graptolites is discussed. For many years the genus Tristichograptus Jackson and Bulman has been known under the name of Trigonograptus, principally from the species T. ensiformis Hall, of wide distribution in the Lower Ordovician. It has recently become apparent that the type specimen of the type species of Trigonograptus, T. lanceolatus, comprises two stipes of a Didymograptus lying side by side (Jackson and Bulman 1970). The distinctive T. ensiformis obviously merits generic recognition and the new name Tristichograptus was proposed by Jackson and Bulman with T. ensiformis as the type species. Although widely known from flattened specimens, the structure of this form has hitherto remained obscure. Recently collected material from the Valhallfonna Forma- tion, Northern Ny Friesland, Spitsbergen (Vallance and Fortey 1968) contains speci- mens preserved in full relief, which have enabled the structure of T. ensiformis to be elucidated. The graptolite occurs between 147 m and 157 m above the base of the formation in a dark, impure limestone; it is only abundant in one thin limestone bed at 147 m and the specimens figured in this paper all come from this horizon. T. ensi- formis is associated with numerous trilobites of the families Olenidae ( Triarthrus , Hypermecaspis, and cf. Parabolinella), Endymioniidae ( Endymionia ), and Komaspidae ( Carolinites ); conodonts, chitinozoa, scolecodonts, and rare inarticulate brachiopods were also obtained on dissolving the rock. Most of the graptolite material is heavily carbonized and disintegrates when the matrix is dissolved. Certain irregular patches of the rock are silicified and this seems to have protected the graptolite periderm from further diagenetic changes. When this siliceous rock is dissolved in hydrofluoric acid, all traces of carbonate having been removed in dilute acetic acid, large pieces of the rhabdosome could be obtained, sometimes quite clear, or easily cleared. SYSTEMATIC DESCRIPTION Family dichograptidae Lapworth 1873 Genus tristichograptus Jackson and Bulman 1970 Tristichograptus ensiformis (J. Hall) Plates 26-29 1858 Graptolithus ensiformis Hall, p. 133. [Palaeontology, Vol. 14, Part 1, 1971, pp. 188-199, pis. 26-29.] R. A. FORTEY: TRISTICHOGRAPTUS 189 Material (numbers refer to the Sedgwick Museum, Cambridge catalogue). Complete growth series: SM A70588-94, 70598; isolated distal fragments: SM A70595, 70586-7; specimens in relief on the rock: SM A70582-5; other material: more than 100 isolated proximal and distal fragments. Horizon and locality. Lower Ordovician, Valhallfonna Formation, Lower limestone division, 147 m above base, N. Ny Friesland, Vestspitsbergen. Description. The rliabdosome is triserial, scandent, lanceolate, tapering gently proxi- mally, more rapidly distally (text-figs. 1-3). There is no nema after the first four or five thecae of each series have been developed. The three series of thecae are set at 120° text-fig. 1. Reconstruction of complete rhabdosome. x4. a. Apertural view. b. Lateral view. c. With one series removed to show typical appearance of flattened material. Compare PL 29, fig. 3 a. to one another, and the cross-section of the stipe is a rounded triangle (text-fig. 2a) the apices of the triangle being formed by the apertural lips of the thecae. The width of the stipe (that is, the side of the cross-sectional triangle) gradually increases up to about 3-4 mm at th. 11, though the mature width is somewhat variable. The length of the rhabdosome rarely exceeds 20 mm. In the mature parts of the stipe the thecae are spaced 10-12 in 10 mm, 11 being usual, but are more closely spaced proximally, the first 3 mm of each series enclosing 5 thecae. The thecae are inclined at 40-50°, slightly less proximally. They are short and broad with a maximum transverse width of T25 mm and have downwardly deflected lips 0-5 mm in length. Thecal overlap is 0-5-0-6. In profile the apertural margin is gently undulate. The thecae in the mature stipe are connected with succeeding thecae in the a b c 190 PALAEONTOLOGY, VOLUME 14 same series by transversely elliptical foramina with thickened margins, 0-6 mm long diameter and 0-2 mm wide. The growing end of the mature rhabdosome is arranged in a clockwise spiral of thecae, that is, each thecae to the left is displaced upwards one third of the interthecal spacing. The contact of one series of thecae with the others is along an apparent median septum, which forms the perpendicular bisectrix of the cross sectional triangle (text-fig. 2a): it is thus triradiate with the three walls set at 120° to one another. Each series retains a complete, dorsal peridermal wall, so that the septum is composed of a double layer of periderm. Because of this any one series of thecae may easily be detached from the other two. text-fig. 2. Derivation of an apparently biserial from the triserial rhabdosome, partly sche- matic. a. Part of mature rhabdosome. b. The same, with third series broken off along the median septum, to give an apparently biserial rhabdosome. Note alternating arrangement of the traces of the interthecal septa of the remaining two series, c. Dorsal view of specimen derived as b. X 12-5. SM A70599. When one series of thecae are separated along the ‘median septum’, which generally happens when rock containing relief material is broken, the resulting appearance of the rhabdosome is identical to that of previously published figures of T. ensiformis (see text-fig. 2b; PL 29, figs. 2, 3; text-fig. lc). In this case only the two surfaces of the ‘median septum’ set at 120° can be seen with the traces of the interthecal septa of the two remaining series of the upper surface. The interthecal septa are alternate, displaced about one third the interthecal distance on either side of the ‘axis’, corresponding to the spiral order of the thecae of the rhabdosome. The apertures are not visible in this aspect, and so an apparently biserial graptolite is seen with a nearly straight sided margin. All material of T. ensiformis known hitherto is flattened, and it is important to con- sider how flattening can reduce the three stiped graptolite to a ‘biserial’ appearance. The rhabdosome would usually come to rest on the sediment surface on one of its three sides. This results in the third thecal series pointing vertically (text-fig. 2a). The principal plane of weakness then lies along the plane of the ‘median septum’, the rhabdo- some splitting along this nearly horizontal plane more easily than around the projecting thecae (text-fig. 2b, c; PL 29, fig. 3). Flattening opens out the median septum from 120° to 1 80°. The lower two series of thecal apertures are directed downwards and obscured by the ‘median septum’, and the third series also cannot be seen as it is pointing upwards into the rock containing the counterpart. The collapse of the thecal margins of the R. A. FORTEY: TRIST1CH0GRAPTUS 191 bottom two series of thecae results in the almost straight sided ‘edge’ of the flattened Tristichogr optus. Thus Tristichograptus ensiformis as seen when flattened is, in fact, merely part of the ‘median septum’, with the traces of the interthecal septa of the bottom two series only, forming the two series of the apparently biserial rhabdosome. This mode of preservation carries with it the implication that tristichograptids with different apertural characteristics could give similar compressions. text-fig. 3. Three aspects of a small mature rhabdosome. x25. a. Series a apertural view. b. Series b apertural view. c. Series c apertural view. This specimen was broken on transference to glycerine. SMA70588 represents the similar stage of growth. Elies and Wood (1908) seem to have come some way towards an understanding of the arrangement of the thecae when they commented that the ‘two stipes’ may have been arranged at right angles, ‘rather like a Phyllograptus with only two of the stipes de- veloped’. One of their figured specimens shows a prominent ‘virgellar spine’: this could be developed simply from the compression of that aspect in which the sicula, th. I1 and th. I2 lie in the same plane (text-fig. 3c). Discussion. Published measurements of Tristichograptus ensiformis (Table 1) are in general agreement with those obtained from the Spitsbergen material (based on 30 specimens). Both ‘width’ and length are highly variable; those specimens with greater width are also much longer than the Spitsbergen material (e.g. Ruedemann 1947) and such differences merely seem to reflect continued growth rather than specific differences. The thecal spacing varies from 9 to 12 in 10 mm, the majority have a mature spacing of 11 in 10 mm; the Spitsbergen material agrees well. The inclination of the thecae to the ‘axis’ is also close to previously described examples. It seems reasonable to conclude that, in so far as the measurements made on flattened Tristichograptus reflect the characters of the whole rhabdosome, the described material does represent a single species. There is little variation in the shape of the thecae of isolated material; some speci- mens have slightly narrower thecae proximally than others (text-fig. 5). One remarkable 192 PALAEONTOLOGY, VOLUME 14 pathological fragment (PI. 28, fig. 2) has the thecae arranged in a T-shape, like three series of a Phyllograptus \ distally it degenerates into an irregular cluster of 5 relatively small thecae. In spite of its bizarre appearance the shape of the thecae leave no doubt that this is an abnormal Tristichograptus. TABLE 1 Proximal Distal Max. Max. no. of no. of Angle of length ‘ width ’ thecae thecae inclination Author {nun) {mm) 10 mm 10 mm of thecae Hall 1865 60 4 11 50 Hopkinson and Lapworth 1875 8 2 12 Nicholson 1890 15 3 Elies 1898 38 4-76 11 9-10 45 Elies and Wood 1908 50 5 9-11 50 Harris 1924 5 11 45 Ruedemann 1947 80 7 11 45 Mu and Lee 1958 35 4 12 10 30-50 „ „ ,, (var. minor) 16 2-4 14 9-10 Berry 1960 50 3 9-11 45 Obut and Sobolevskaya 1964 18 4 10-11 50-55 Yao 1965 40 4 11 30-50 Fortey (this paper) 21 4 12-16 10-12 40-50 The genus Pseudotrigonograptus Mu and Lee (1958) compares closely with Tristicho- graptus in stipe width, thecal spacing and form of ‘thecae’ (i.e. the median septum with the traces of interthecal septa). Mu and Lee believed that this form had four stipes like Phyllograptus , but with thecae in adjacent rows in contact along their length as in Tristichograptus. To judge from the illustrations of relief material of Pseudotrigono- graptus (Mu and Lee 1958), and from the fact that Trigonograptus ensiformis is recorded from the same beds, there seems little reason to doubt that Pseudotrigonograptus is synonymous with Tristichograptus. Mu and Zhan (1966) reached the same conclusion, but believed Trigonograptus itself to be a quadriserial, Phyl/ograptus-likQ form. Development (Pis. 26-28). A number of nearly clear growth stages were obtained from which the proximal and development could be deduced. The prosicula is 0-25-0-3 mm EXPLANATION OF PLATE 26 Proximal end development of Tristichograptus ensiformis. X 50. Fig. 1. Prosicula and early metasicula. SM A70598. Fig. 2. Sicula and initial bud, showing origin of th. I1 on prosicula. SM A70589. Fig. 3 a. Mature sicula and first theca showing origin of th. I2. SM A70590. 3b. Thecal diagram. Fig. 4a. Growth stage showing origin of th. 21. SM A70591. 4b. Thecal diagram. Fig. 5a. Growth stage showing origin of th. 22. SM A70592. 5b. Thecal diagram. All figures in b apertural aspect, fo = foramen; s = sicula. EXPLANATION OF PLATE 27 Proximal end development of Tristichograptus ensiformis, X 50. SM A70593. Growth stage showing origin of th. 31a and th. 31b. Fig. la. Series b apertural aspect, lb. Thecal diagram. Fig. 2a. Series a apertural aspect. 2b. Thecal diagram, fo = foramen; s = sicula. Palaeontology, Vol. 14 PLATE 26 FORTEY, Ordovician triserial graptolite Palaeontology, Vol. 14 PLATE 27 FORTEY, Ordovician triserial graptolite R. A. FORTEY: TRISTICHOGRAPTUS 193 long with a hollow nema 0-05-0-1 mm long; there are 7 or 8 longitudinal lines (PI. 26, figs. 1, 2). The distal margin of the prosicula seems to have a slightly thickened rim. The mature sicula attains a length of 1 -6—1 -9 mm; it curves slightly distally and is pro- duced ventrally into a long, narrow spatulate lip up to 0-5 mm long (PI. 26, fig. 3). The aperture is circular, 0-30 mm in diameter. The initial bud (PI. 26, fig. 2) appears about two thirds of the way down the prosicula from a ventral, circular, resorption foramen. It is developed when the metasicula is only 0-15 mm long; thereafter the first theca grows down the ventral side of the sicula until almost on a level with the sicular aperture, when it is flexed sharply away from the sicula lip to form an angle of 45-60° with the ventral side of the sicula. The lip of th. I1 is not usually so pronounced as that of the sicula, 0-3 mm long. It is noteworthy that the growth-lines on the sicula and first theca are relatively densely spaced compared with those of the thecae that follow; moreover the sicula and th. I1 become secondarily thickened at a very early stage so that the growth- lines soon become difficult to discern. The second thecae, th. I2, originates from a fora- men 0-35 mm high, half-way down th. I1, grows ventrodorsally across the sicula to point in the opposite direction to th. I1 (PI. 26, figs. 3, 4). The circular aperture with a prominent lip is similar to that of th. I1. The sicula, th. I1 and th. I2 and their apertural lips lie in the same plane, and the lips project below the rest of the stipe: there is as yet no tendency for the thecae to become scandent. The development becomes complex subsequently, and it is difficult to refer the suc- ceeding thecae to the conventional scheme of thecal nomenclature. The three series have been named a, b, and c, and these are recognized as follows : series c is that series which is most closely aligned with th. I2; series b is that series which is most closely aligned with th. I1; series a is that series which is not aligned either with th. I1 or th. I2. When the rhabdosome comes to rest on one of its three sides one of these three series points upwards. The three aspects of a small mature stipe are shown in text-fig. 3. A foramen is produced very near to the base of th. I2, to give rise to th. 21 (PI. 26, fig. 4). This theca develops into the first evidence of the triserial arrangement, growing across the dorsal side of th. I1 (PI. 26, fig. 5) to form the basal theca of series a. A second foramen in th. I2 gives rise to th. a (series c) shortly afterwards; this theca continues to grow almost in line with th. I2 for some time. Thus th. I2 is dicalycal, and establishes the first thecae in series c and a. Th. x is remarkable in that it does not give rise to any of the succeeding thecae. The first theca of series b, th. 22, originates near the proximal end of th. 21 (PI. 26, fig. 5). The basic triserial pattern of the rhabdosome has now been established, but a peculiar feature of the subsequent development is that the second thecae of series a and c are not derived directly from the preceding thecae in the same series. Th. 22 thus forms the base from which the rest of the rhabdosome develops. The following three thecae originate in quick succession as follows; in b apertural aspect (PI. 27, fig. 1) a right lateral foramen in th. 22 gives rise to th. 3 xa (PI. 27, fig. 2); th. 3 xb originates via a dorsal foramen also in th. 22 (PI. 27, fig. 1); shortly afterwards th. 4lc is derived from th. 3 (the foramen showing this is illustrated in c apertural aspect in PL 28, fig. 1). Th. 3 also gives rise to the succeeding theca in the same series, th. 4 1b. Th. 22 and th. 3 xb are thus both dicalycal. The sicula is not centrally placed throughout this development, but is closer to series c than to series a or b, that is away from the side in which the branching is taking place (PL 27, figs. 1, 2). The triserial arrangement that characterizes the mature stipe has now been established, O 7896 o 194 PALAEONTOLOGY, VOLUME 14 and series a, b, and c remain separate; th. 4xc gives rise to th. 5 xc, etc., th. 3 xb to th. 4 xb, 5 xb, etc., th. 3 xa to th. 4xa, 5xa, etc. No evidence of a nema has been seen above the level of about th. 5. The interthecal septum where it has been observed is a single unit formed by the dorsal wall of the lower of two thecae in contact (for example, that between th. x and th. 4 xc, PI. 28, fig. 1). The thecae change in form gradually over the proximal part of the stipe, having progressively less circular, more transversely elliptical apertures (text- fig. 3, PI. 29, fig. 4) of increasing diameters, and the thecal lips becoming proportionately shorter. The first four thecae are not precisely aligned with those in the distal part of the rhabdosome (PI. 29, fig. 5). The rhabdosome becomes thickened with cortical tissue progressively upwards from th. I2. The development is shown diagrammatically in text-fig. 6. Accessory foramina. When the rhabdosome is dissected or fortuitously broken, addi- tional foramina have been observed in apparently constant positions. They are smaller than the normal foramina, sub-circular, with a slightly thickened rim. One dissected specimen is shown in text-fig. 4, from which parts of the external walls were removed using fine forceps to reveal the internal structure. The accessory foramen between th. x and th. 4xc is formed in the dorsal wall of th. x in such a position that it could not have given rise to th. 4xc. Growth-lines on th. x are truncated by the foramen, and it must, therefore, have been formed by resorption, in a manner analogous to the primary resorption foramen, but unlike the foramina involved in the development described previously. Similar foramina are developed between th. 22 and th. x, and between th. 3 xb and th. 4 xa. Their development is apparently constant and in the same positions; we have seen three examples of that between th. 22 and th. x, two of that between th. x and th. 4xc, but only one of that between th. 3 xb and th. 4xa. It remains a possibility that they may be found in other positions. Probably the only comparable structure known is the foramen produced between EXPLANATION OF PLATE 28 Fig. 1 a. Growth stage of Tristichograptus ensiformis, X50. SM A70594. Series c apertural aspect, showing origin of th. 4 xc. 1 b. Thecal diagram, fo = foramen; s = sicula. Fig. 2. Pathological specimen, X 25. SM A70595. EXPLANATION OF PLATE 29 Tristichograptus ensiformis. Fig. 1. Isolated distal fragment, x6. SM A70587. Fig. 2. Specimen with third series partly broken out, but visible in the proximal part of the rhabdo- some. X 6. SM A70585. Fig. 3 a. Nearly complete rhabdosome with third series broken out to show the typical appearance of Tristichograptus as known from flattened material. X 6. SM A70583. Fig. 3b. Distal fragment, third series only, the other two series having broken out along median septum. x6. SMA 70584. Fig. 4. Isolated small, complete rhabdosome. Series a apertural aspect, x 15. SM A70588. Fig. 5. Isolated near-proximal fragment, X 10. SM A70586. Fig. 6. Distal fragment, lateral view, x6. SM A70582. Figs. 1, 4, 5, photographed beneath glycerine; in Figs. 2, 3, 6, the specimen was whitened with ammonium chloride. Palaeontology, Vol. 14 PLATE 28 tM p fhS’o fh4 c th 3 b to3 b -* 4 c m2 th 2' FORTEY, Ordovician triserial graptolite Palaeontology, Vol. 14 PLATE 29 6 FORTEY, Ordovician triserial graptolite R. A. FORTEY: TRIS TICHOGRAP TUS 195 bitheca and autotheca in some dendroid graptolites (e.g. Bulman and Rickards 1966). There is some indication in the accessory foramen between th. x and th. 4 1c of a later infilling of the foramen. No foramina have been found between series above th. 5, a point approximately coincident with the top of the nema and the start of the median septum. Affinities. There can be no doubt that Tristichograptus belongs within the Dichograp- tidae in its present definition. The dicalycal th. I2 indicates the Isograptid mode of development ( gibberulus stage) ( Bulman 1936a). The origin of th. I1 on the prosicula text-fig. 4. Specimen dissected to show accessory foramina. X 50. SM A70596. fo. acc. = accessory foramen. is a feature found in several dichograptids, but also in Corynoides (Kozlowski 1953). The origin of th. I2 low on th. ll is an unusual feature which distinguishes Tristicho- graptus from Isograptus and its allies ( Oneograptus , Cardiograptus) in which brandling occurs rapidly very near the proximal end. A low origin of th. I2 has, however, been remarked on Tetragraptus bigsbyi (see Bulman 1955, p. V58, Skevington 1965, p. 14). The ‘blind’ theca, th. a*, originating from th. I2, has its only analogue in Oneograptus (Bulman 19366) which has a theca produced from th. I1 which does not give rise to any subsequent thecae, but as mentioned above any direct relationship between Tristicho- graptus and Oneograptus is unlikely. Tristichograptus occurs after the appearance of Phyllograptus and generally as a con- temporary of the earliest biserial graptolites. It seems hypothetically possible to regard 196 PALAEONTOLOGY, VOLUME 14 Tristichograptus as derived from Phyllograptus by a loss of one series, and a biserial rhabdosome from Tristichograptus by the loss of another series. The development of Phyllograptus is still not well known, and the only form studied from isolated material, P. angustifolius (Bulman 1936u), is a Scandinavian species outside the known geo- graphical distribution of Tristichograptus. However, P. angustifolius does share with Tristichograptus an isograptid development, the lack of a nema in the mature parts of the stipe, and some similarity of thecal and stipe form. It may also be significant that the pathological Tristichograptus (PI. 28, fig. 2) resembles Phyllograptus in its cruciform arrangement of thecae. Phyllograptus typus and P. anna (Ruedemann 1947) exhibit a ‘sicular spine’ com- parable to that seen in some flattened Tristichograptus specimens, and interpreted as the compression of the sicula lip; this might provide some small intimation that similar proximal ends to Tristichograptus might be found among the phyllograptids. Bulman (1936u) has noted the probability of a polyphyletic derivation of Phyllograptus from several reclined tetragraptids, and it is not possible to be certain of the relation of Tristichograptus to Phyllograptus until more proximal end developments of the latter are known. There is no similarity between the proximal end of Tristichograptus and that of Diplograptidae (Bulman, 1955, p. V59). G/ossograptus and Cryptograptus (Whitting- ton and Rickards 1969) have a more primitive (dichograptid) development than Tristi- chograptus, based on a dicalycal th. I1. There can be little doubt that Tristichograptus is not directly related to either the Glossograptidae or Diplograptidae as so far known, and would therefore be a most improbable intermediate between quadriserial and biserial graptolites. A continuation of the reduction of the internal periderm at the proximal end produced by the secondary foramina, might result in a cryptoseptate condition as in Lasiograptus harknessi (see Rickards and Bulman 1965), though the th 4 'a th 5'a text-fig. 5. Proximal end (series c apertural aspect) with slightly narrower thecae than usual, X 15. SM A70597. text-fig. 6. Diagrammatic development of Tristichograptus ensiformis, th. I2, th. 22, and th. 3 1b are dicalycal. R. A. FORTEY: TRISTICHOGRAPTUS 197 diplograptid proximal end development of the Lasiograptidae again makes any phyletic link with Tristichograptus unlikely. Tristichograptus probably shows the closest relationship to Tetragraptus bigsbyi (see Bulman 1955, p. V58) sharing with that species the isograptid development, the origin of th. I1 on the prosicula, and the origin of th. I2 low on th. I1. In T. bigsbyi , however, th. I1 becomes horizontal or reclined distally, and no direct phyletic link between C D text-fig. 7. Hypothetical evolutionary series deriving Tristichograptus from a Tetragraptus bigsbyi type ancestor, a. Generalized Tetragraptus with bigsbyi type development (modified after Bulman, 1955). b. Production of three branched Tetragraptus by loss of th. 2 2a. Termin- ology of thecae changed to that of Tristichograptus. c. Rearrangement of theca without further change to produce a scandent form. d. Derivation of th. 4 V from th. 3 1b rather from th. x to give Tristichograptus development as in text-fig. 6. T. bigsbyi and Tristichograptus is proposed. In all probability Tristichograptus was derived from some other Tetragraptus with a bigsbyi- like development either via Phyl/o- graptus or possibly directly from a tetragraptid in which the stipes were reduced to three, a well-known tendency among Tetragraptus species (e.g. Bulman and Cooper 1969). The derivation of th. 4xc from th. 3 xb rather than from th. in our material is one of the most curious features of the development of Tristichograptus. If derived from any known dichograptid, it seems probable that this mode of origin of series c was secondarily 198 PALAEONTOLOGY, VOLUME 14 acquired after a suppression of a series arising directly from th. x. Discovery of Tristicho- graptus with th. x giving rise to series c might be expected. A hypothetical series deriving Tristichograptus from a T. bigsbyi- like ancestor is given in text-fig. 7. Age and associated fauna. The associated graptolites include: Kinnegraptus sp. ; Didymo- graptus formosus Bulman; D. cf. hirundo Salter; Didymograptus sp. nov. ; Tetragraptus sp. ; Isograptus cf. manubriatus (T. S. Hall); Isograptus caduceus var. Didymograptus formosus is known from rocks of hirundo age from Sweden (Bulman 1936«, Skevington 1965). Kinnegraptus is recorded from Sweden (Skoglund 1961), and also from Norway (Bulman and Cowie 1962) in the Lower Didymograptus Shales in the transition beds between 3bS (zone of Phyllograptus angustifolius elongatus ) and 3 be (D. hirundo zone). Both these occurrences indicate an hirundo age or very near for the present fauna. Tristichograptus itself, together with Isograptus manubriatus, are charac- teristic of the Yapeenian in Australia (Harris and Thomas 1938) and of zones 8-9 of Berry (1960) in Texas. Dewey, Rickards and Skevington, (1970) in a recent paper, point out the provinciality of Lower Ordovician graptolite faunas, but were able, based on a Lower Ordovician fauna from Western Ireland, to correlate the Yapeenian (about Berry zone 8) with the hirundo zone of the standard British succession. It is therefore of interest to note that the admixture of ‘Pacific’ ( Tristichograptus , I. cf manubriatus ) forms with Baltic ( Kinnegraptus , D. formosus) forms in the Spitsbergen section, together with a species very close to D. hirundo, provides independent evidence for their correla- tion. A high Arenig, probably hirundo age is thus indicated for the Spitsbergen fauna. Conclusions 1. Tristichograptus [formerly Trigonograptus] ensiformis (J. Hall) is the only known triserial graptolite. 2. It belongs within the family Dichograptidae, having a basically isograptid develop- ment (th. I2 dicalycal). Its subsequent development is complex. 3. The typical flattened appearance of Tristochograptus is apparently biserial, with no sign of thecal apertures. This appearance is produced by breakage along the median septum of the triserial form. 4. In Spitsbergen Tristichograptus occurs with an assemblage of graptolites indicative of a late Arenig (probably hirundo zone) age. Acknowledgements. The author is indebted to the experience and advice of Professor O. M. B. Bulman and Dr. R. B. Rickards throughout the preparation of this paper. Miss J. B. Archer gave invaluable assistance in the preparation of the material, and Dr. P. D. Lane with the photography. The work was undertaken during the tenure of a N.E.R.C. research grant. REFERENCES berry, w. b. n. 1960. Graptolites of the Marathon region, West Texas. Univ. of Texas. Bureau of Eco- nomic Geology, Pub. no. 6005. 179, pi. 20. bulman, o. m. b. 1936<7. On the graptolites prepared by Holm. Part VII. The graptolite fauna of the Lower Orthoceras Limestone of Halludden, Oland, and its bearing on the evolution of the Lower Ordovician graptolites. Ark. Zool. 28A (17), 1-107, 4 pis. R. A. FORTEY: TRISTICHOGRAPTUS 199 bulman, o. m. b. 19366. The structure of Oncograptus T. S. Hall. Geol. Mag. 73, 271-8. 1955. Graptolithina, in moore, r. c. (ed.). Treatise on invertebrate palaeontology, part Y, Geol. Soc. Am. and Univ. Kansas Press. and cooper, r. a. 1969. On the supposed occurrence of Triograptus in New Zealand. Trans. R. Soc. N.Z. Geology, 6 (6), 213-18. and cowie, c. m. 1962. On the occurrence of Kinnegraptus (Skoglund) in Norway. Norsk. Geol. Tiddskr. 42, 253-60, pi. 1. and rickards, r. b. 1966. A revision of Wiman’s dendroid and tuboid graptolites. Bull. geol. Instn Univ. Upsala , 43 (6), 72 pp. dewey, J. F., rickards, r. b., and skevington, d. 1970. New light on the age of Dalradian deformation and metamorphism in western Ireland. Norsk. Geol. Tiddskr. 50, 19-44. elles, g. l. 1898. The graptolite fauna of the Skiddaw Slates. Q. Jl geol. Soc. Lond. 54, 523-4, fig. 34. and wood, e. m. r. 1908. Monograph of the British Graptolites. Palaeontogr. Soc. ( Monogr .), Pt. 7, 273-358, pi. 3. hall, J. 1858. Report on Canadian graptolites. Geol. Surv. Canada. Rept. Progr. for 1857. Montreal. 1865. Figures and descriptions of Canadian organic remains. Decade II. Graptolites of the Quebec Group. Canada Geol. Survey, p. 151. Harris, w. J. 1924. Victorian graptolites, new series, Pt. 1. Proc. R. Soc. Viet, (n.s.), 36, 92-106. and thomas, d. e. 1938. A revised classification and correlation of the Ordovician graptolite beds of Victoria. Victoria Dept, of Mines, Min. geol. J. 1 (3), 62-73. hopkinson, J. and lapworth, c. 1875. Descriptions of the graptolites of the Arenig and Llandeilo rocks of St. David's. Q. Jl geol. Soc. Lond. 31, 631-72. JACKSON, d. e. and BULMAN, o. m. b., 1970. On the generic name Trigonograptus Nicholson, 1869. Proc. geol. Soc. Lond. 1663, 107-9. kozlowski, r. 1953. Badania nad nowym gatunkiem z rod zaju Corynoides (Graptolithina). Acta geol. pol. 13 (2), 193-209. mu, A. T. and lee, c. k. 1958. Scandent graptolites from the Ningku shale of the Kiangshan-Changshan area. Western Chekiang. Acta, palaeont. sin. 6 (4), 391-427. and zhan, s. g. 1966. On the probable development and systematic position of Glossograptus. Scientia sinica, 15 (1), 92-8, pi. I. nicholson, h. o. 1890. Note on the occurrence of Trigonograptus ensiformis Hall, sp., and of a variety of Didymograptus v-fractus, Salter, in the Skiddaw Slates. Geol. Mag. [3], 7, 340-4. obut, a. m. and sobolevskaya, r. f. 1964. Ordovician graptolites of Taymir. Akad. Nauk SSR Otdl. Inst. Geol. Geofiz. Minist-Geol. SSR, Nauchno-Issledov. Inst. Geol. Arktiki., 1-92. rickards, r. b. and bulman, o. m. b. 1965. The development of Lasiograptus harknessi (Nicholson 1867). Palaeontology, 8, 272-80. ruedemann, r. 1947. Graptolites of North America. Mem. geol. Soc. Am. 19. skevington, d. 1965. Graptolites from the Ontikan Limestones (Ordovician) of Oland, Sweden. II. Graptoloidea and Graptovermida. Bull. geol. Inst. Univ. Upsala, 43 (3), 1-74. skoglund, r. 1961. Kinnegraptus, a new graptolite genus from the lower Didymograptus shales of Vastergotland, central Sweden. Ibid. 40, 389-400, pi. 1. vallance, g. and fortey, r. a. 1968. Ordovician succession in North Spitsbergen. Proc. geol. Soc. Lond. 1648, 91-7. Whittington, h. b. and rickards, R. b. 1969. Development of Glossograptus and Skiagraptus, Ordo- vician graptoloids from Newfoundland. J. Paleont. 43, 800-17. yao, l. c. 1965. Some lower Ordovician scandent Axonolipous graptoloids from the Tzishui valley, Hurian. Acta, palaeont. sin. 13 (1), 107-15, pi. 1. r. a. fortey British Museum (Natural History) Cromwell Road London, S.W.7 Typescript received 16 May 1970 THE PALAEONTOLOGICAL ASSOCIATION PALAEONTOLOGY The journal Palaeontology is devoted to the publication of papers (preferably illus- trated) on all aspects of palaeontology and stratigraphical palaeontology. Four parts at least are published each year and are sent free to all members of the Association. Members who join for 1971 will receive Volume 14, parts 1 to 4. All back numbers are still in print and may be ordered from B. H. Blackwell, Broad Street, Oxford, England, at £5 per part (post free). A complete set, Volumes 1-13, consists of 51 parts and costs £255. SPECIAL PAPERS IN PALAEONTOLOGY This is a series of substantial separate works published by the Association. The sub- scription rate is £6 (U.S. $16.00) for Institute Members and £3 (U.S. $8.00) for Ordinary and Student Members. Subscriptions and orders by members of the Asso- ciation should be placed through the Membership Treasurer, Dr. A. J. Lloyd, Depart- ment of Geology, University College, Gower Street, London, W.C. 1, England. The following Special Papers are available. Members may obtain them at reduced rates through the Membership Treasurer. Non-members may obtain them from B. H. Blackwell, Broad Street, Oxford, England, at the prices indicated. Special Paper No. 1 (for 1967): Miospores in the Coal Seams of the Carboni- ferous of Great Britain, by A. H. V. Smith and M. A. Butterworth. 324 pp., 72 text-figs., 27 plates. Price £8 (U.S. $22.00), post free. Special Paper No. 2 (for 1968): Evolution of the Shell Structure of Articulate Brachiopods, by A. Williams. 55 pp., 27 text-figs., 24 plates. Price £5 (U.S. $13.00). Special Paper No. 3 (for 1968): Upper Maestriceitian Radiolaria of California, by Helen P. Foreman. 82 pp., 8 plates. Price £3 (U.S. $8.00). Special Paper No. 4 (for 1969): Lower Turonian Ammonites from Israel, by R. Freund and M. Raab. 83 pp., 15 text-figs., 10 plates. Price £3 (U.S. $8.00). Special Paper No. 5 (for 1969): Chitinozoa from the Ordovician Viola and Fernvale Limestones of the Arbuckle Mountains, Oklahoma, by W. A. M. Jenkins. 44 pp., 10 text-figs., 9 plates. Price £2 (U.S. $5.00). Special Paper No. 6 (for 1969): Ammonoidea from the Mata Series (Santonian- Maastrichtian) of New Zealand, by R. A. Henderson. 82 pp., 13 text-figs., 15 plates. Price £3 (U.S. $8.00). Special Paper No. 7 (for 1970): Shell Structure of the Craniacea and other Calcareous Inarticulate Brachiopoda, by A. Williams and A. D. Wright. 51 pp., 17 text-figs., 15 plates. Price £1-50 (U.S. $4.00). SUBMISSION OF PAPERS Typescripts on all aspects of palaeontology and stratigraphical palaeontology are invited. They should conform in style to those already published in this journal, and should be sent to Mr. N. F. Hughes, Department of Geology, Sedgwick Museum, Downing Street, Cambridge, England, who will supply detailed instructions for authors on request (these are published in Palaeontology, 10, pp. 707-12). VOLUME 14 • PART 1 CONTENTS A Devonian lycopod stem with well-preserved cortical tissues. By h. n. Andrews, C. B. READ, and S. H. mamay 1 Alleynodictyon, a new Ordovician stromatoporoid from New South Wales. By b. d. WEBBY 10 Preservation! history of ceratite shells. By A. seilacher 16 Dinoflagellate cyst structures : walls, cavities, and bodies. By r. l. cox 22 Taxonomy of dicoelosiid brachiopods from the Ordovician and Silurian of the east Baltic. By M. rubel 34 Muscular mechanics and the ontogeny of swimming in scallops. By s. J. gould 61 .An endopunctate rhynchonellid brachiopod from the Visean of Belgium and Britain. By c. h. c. brunton 95 Wrinkle-layer structures in Jurassic ammonites. By J. r. senior 107 On the type species of Macrocephalites Zittel 1884 and the type specimen of Ammonites macrocephalus Schlotheim 1813. By J. h. callomon 114 A problem of faunal replacement on Permo-Triassic continents. By Pamela l. ROBINSON 131 A system for the storage, retrieval, and analysis of numerical data in palaeontology. By i. E. PENN 154 Some trilobites from the Silurian-Devonian boundary beds of Czechoslovakia. By i. chlupaC 159 Polypora steno stoma: a Carboniferous bryozoan with cheilostomatous features. By R. TAVENER-SMITH 178 Tristichograptus, a triserial graptolite from the Lower Ordovician of Spitsbergen. By R. A. FORTEY 188 PRINTED IN GREAT BRITAIN AT THE UNIVERSITY PRESS, OXFORD BY VIVIAN RIDLER, PRINTER TO THE UNIVERSITY VOLUME 14 • PART 2 Palaeontology JULY 1971 PUBLISHED BY THE PALAEONTOLOGICAL ASSOCIATION LONDON Price £5 THE PALAEONTOLOGICAL ASSOCIATION The Association was founded in 1957 to further the study of palaeontology. It holds meetings and demonstrations, and publishes the quarterly journal Palaeontology and Special Papers in Palaeontology. Membership is open to individuals, institutions, libraries, etc., on payment of the appropriate subscription: Institute membership ..... £10-00 (U.S. $26.00) Ordinary membership £5-00 (U.S. $13.00) Student membership £3-00 (U.S. $8.00) There is no admission fee. Institute membership is only available by direct appli- cation, not through agents. Student members are persons receiving full-time instruc- tion at educational institutions recognized by the Council; on first applying for membership, they should obtain an application form from the Membership Treasurer. All subscriptions are due each January, and should be sent to the Membership Treasurer, Dr. A. J. Lloyd, Department of Geology, University College, Gower Street, London, W.C. 1, England. COUNCIL 1971-2 President: Dr. W. S. McKerrow, Department of Geology, Oxford Vice-Presiden ts : Professor M. R. House, The University, Kingston upon Hull, Y orkshire Dr. Gwyn Thomas, Department of Geology, Imperial College, London, W.C. 7 Treasurer: Dr. J. M. Hancock, Department of Geology, King’s College, London, W.C. 2 Membership Treasurer: Dr. A. J. Lloyd, Department of Geology, University College, Gower Street, London, W.C. 1 Secretary: Dr. W. D. I. Rolfe, Hunterian Museum, The University, Glasgow, W. 2 Editors Mr. N. F. Hughes, Sedgwick Museum, Cambridge Dr. Isles Strachan, Department of Geology, The University, Birmingham 15 Dr. R. Goldring, Department of Geology, The University, Reading, Berks. Dr. J. D. Hudson, Department of Geology, The University, Leicester Dr. D. J. Gobbett, Sedgwick Museum, Cambridge Other members of Council Dr. E. N. K. Clarkson, Edinburgh Dr. L. R. M. Cocks, London Dr. R. H. Cummings, Abergele Dr. W. J. Kennedy, Oxford Mr. M. Mitchell, Leeds Dr. Marjorie D. Muir, London Dr. B. Owens, Leeds Dr. W. H. C. Ramsbottom, Leeds Dr. Pamela L. Robinson, London Dr. E. P. F. Rose, London Dr. C. T. Scrutton, Newcastle Dr. V. G. Walmsley, Swansea Dr. A. D. Wright, Belfast Dr. Julia Hubbard, London ( co-opted ) Overseas Representatives Australia : Professor Dorothy Hill, Department of Geology, University of Queensland, Brisbane Canada: Dr. D. J. McLaren, Institute of Sedimentary and Petroleum Geology, 3303- 33rd Street NW., Calgary, Alberta India: Professor M. R. Sahni, 98 The Mall, Lucknow (U.P.), India New Zealand: Dr. C. A. Fleming, New Zealand Geological Survey, P.O. Box 368, Lower Hutt West Indies and Central America: Mr. John B. Saunders, Geological Laboratory, Texaco Trinidad, Inc., Pointe-a-Pierre, Trinidad, West Indies Western U.S. A. : Professor J. Wyatt Durham, Department of Paleontology, Univer- sity of California, Berkeley 4, California Eastern U.S.A. : Professor J. W. Wells, Department of Geology, Cornell University, Ithaca, New York © The Palaeontological Association, 1971 PALAEONTOLOGY, Vol. 14, Part 1 In the paper by I. Chlupac (page 175), figs, a and b of text-fig. 6 were inadvertently inverted and the captions reversed. A correct version of the figure is given below: text-fig. 6. Comparison of pygidia: a, Ceratocephala verneuili (Barrande) ; b, Ceratocephala lochkoviana sp. nov. ; c, Ceratocephala vesiculosa (Beyr.). Dorsal views, about x4. to be inserted in Palaeontology 14, 2 CUTICLE ULTRASTRUCTURE OF A JURASSIC CRUSTACEAN ( ERYMA STRICKLAND1 ) by A. c. Neville and c. w. berg Abstract. The cuticle of well-preserved pieces of the fossil lobster Eryma stricklandi from the Oxford Clay yields information on its ultrastructure when compared with cuticle of the closely related living crayfish, Astacus fiuviatilis. In both species the pore canals which traverse the laminated layers of the cuticle are large enough to be analysed in the light microscope. In sections cut almost tangential to the surface both species show the pore canals crescentic in section and with the crescents arranged to form a repeating pattern of rows of con- centric parabolae. From living material previously investigated by electron microscopy and from model building, it is clear that this pattern arises from oblique sections of fields of pore canals which are tubes with elliptical cross- section and which twist regularly and in unison about their axes. This twisting is caused by the architecture of the surrounding chitin microfibrils which are arranged in parallel layers. Each layer is set at a slight angle to the preceding one so as to form a progressively rotating structure known as a helicoid. We deduce that the cuticle in Eryma is also helicoidal, and that this system evolved in arthropod cuticle at least as early as the Jurassic. Published photographs of sections of fossil arthropod cuticles do not permit any deductions as to their ultrastructure, beyond saying that they are laminated (e.g. the trilobites, Phacops accipitrinus in Rome 1936, and various trinucleids in Stormer 1930). Cuticles of Silurian Crustacea show laminae and pore canals (Rolfe 1962). By analysis of the pore canals in living material, we are now able to deduce the architec- ture of the surrounding chitin microfibrils (Neville, Thomas, and Zelazny 1969), and these results have been confirmed in the electron microscope (Neville and Luke 1969a, b). In this paper we use this method to gain information about ultrastructure in the cuticle of a fossil lobster ( Eryma stricklandi ) from the Oxford Clay. We have made use of the very large pore canals typically found in Crustacea, permitting their analysis in the light microscope, and have been fortunate in finding fossil material in which the matrix through which the pore canals run is remarkably well preserved. This is probably aided by the marked insolubility of most cuticular components. For comparison with the cuticle of Eryma we have used the living freshwater crayfish, Astacus fiuviatilis. Both species are classified in the infra-order Astacidea Latreille 1803. Material and Methods. Fragments of the exoskeleton of Eryma stricklandi were collected from the Oxford Clay (Jurassic) from a gravel pit on Standlake Common, near Witney, Oxfordshire. The region worked on was the cuticle of the propodite segment of a cheliped limb (PI. 30, fig. 1). Results were compared with the cuticle of the same region from a living freshwater crayfish ( Astacus fiuviatilis). Fossil cuticle was either chipped off the infilling matrix of calcite and iron pyrites or sectioned in situ. Some pieces were ground flat on one face, deliberately made slightly oblique to the cuticle surface to reveal the patterns in the photographs. The flat faces were glued to a glass microscope slide with Lakeside 70 glue and ground by hand using fine grade corundum powder until thin enough sections were obtained. Other pieces were sectioned vertically to the cuticle surface. [Palaeontology, Vol. 14, Part 2, 1971, pp. 201-5, pis. 30-32.] C 7998 P 202 PALAEONTOLOGY, VOLUME 14 For comparison, decalcified pieces of Astacus cuticle were softened in 70% ethanol and sections cut by hand with fresh razor blades at a glancing angle to the surface. Sections were examined in Zeiss polarizing and phase-contrast microscopes. Results. Sections cut vertical to the cuticle surface are compared for Astacus (PI. 31, fig. 1) and the fossil Eryma (PI. 31, fig. 2). The wide lamellation of the endocuticle (deposited after the moult) is clear in both cases, but the finer lamellation in the exocu- ticle (deposited before the moult) is visible only in Astacus. text-fig. 1 . Diagram of the parabolic pattern formed by obliquely sectioning a field of twisted ribbon pore canals, twisting in phase as described in the text. The pore canals in Eryma stricklandi are infilled with calcite. Optical indicatrices are shown in some of the canals. Pore canals, which in Crustacea are responsible for transporting the calcium car- bonate used in post-moult stiffening from the underlying epidermal cells (Travis 1963), appear as lines running vertically to the cuticle surface and hence also to the lamellae. In Plate 30, fig. 2, of Eryma, the pore canals are especially large and clear between crossed polaroids, being filled with birefringent calcite (negative with respect to pore canal length). It is significant that the pore canals appear sinuous and that the curves are in register with the lamellae. The most informative sections are those which are cut almost tangentially to the cuticle surface. Both in Astacus endocuticle (PL 32, fig. 1) and Eryma endocuticle (PI. 32, fig. 2), the obliquely sectioned pore canals form parabolic patterns. Each canal has a crescentic cross-section and in the case of the calcite-filled fossil pore canals the crescents are positively birefringent along their greatest dimension (text-fig. 1). NEVILLE AND BERG: JURASSIC CRUSTACEAN CUTICLE 203 Discussion. Parabolic patterns like those in Plate 32, figs. 1 and 2, were first drawn for lobster ( Homarus ) cuticle by Drach (1939), but an interpretation was not available until recently (Neville, Thomas, and Zelazny 1969). We deduced from model building and sectioning that each pore canal consists of a tube which is elliptical in cross-section, and which is regularly twisted about its longitudinal axis so as to form a twisted ribbon. Such a twisted ribbon has since been photographed in spider cuticle (Barth 1970). A whole field of pore canals twist in register with each other. Sections cut obliquely to text-fig. 2. Diagram showing the origin of a parabolic pattern (in black) of pore canals, arising on an oblique plane of section (stippled), cut through a field of canals which twist in unison. Reconstructed from an electron micrograph of Astacus cuticle. the pore canal axes then show parabolic patterns of the type drawn in text-fig. 1, and as seen in Plate 32, figs. 1 and 2. The origin of this pattern is illustrated in text-fig. 2. Such parabolic patterns of pore canals give information about the ultrastructure of the surrounding cuticle. Arthropod cuticles consists of chitin microfibrils (diameter 50 A) embedded in a protein matrix to form a fibreglass-like system (Neville 1970). The microfibrils are oriented in parallel sheets with the direction of orientation in successive sheets progressively rotating to form a helicoidal stack (Bouligand 1965, Neville and Luke 1969 b). It is this rotation which causes the pore canals to twist at the same pitch. Consequently, we deduce from Plate 32, fig. 2, that the cuticle in Eryma stricklandi was also helicoidal. This also explains the lamellae seen in vertical sections with polarized light (PI. 30, fig. 2, and PI. 31, fig. 2) since birefringence due to the microfibrils will be alternately maximal and minimal for each 90° rotation of the helicoid (i.e. microfibrils 204 PALAEONTOLOGY, VOLUME 14 lying in the plane of section or perpendicular to it respectively). Also, the twisted ribbon structure for pore canals explains the sinusoidal appearance in register with the lamellae seen in Plate 30, fig. 2. It seems as if the helicoidal type of architecture, which we have seen in all present day arthropod cuticles examined so far, evolved at least as early as the Jurassic period. We are eager to pursue this in earlier fossil arthropods, especially in suitably preserved Trilobites. Acknowledgements. We thank Professor J. W. S. Pringle, F.R.S. for reading the typescript, and the Agricultural Research Council for full financial support. REFERENCES barth, f. g. 1970. Die Feinstruktur des Spinneninteguments. II. Die raumliche Anordnung der Mikrofasern in der lamellierten Cuticula und ihre Beziehung zur Gestalt der Porenkanale ( Cupien - nius salei Keys., adult, hautungsfern, Tarsus). Z. Zellforsch. 104, 87-106. bouligand, y. 1965. Sur une architecture torsadee repandue dans de nombreuses cuticules d’arthro- podes. C.r. hebd. Seanc. Acad. Sci., Paris, 261, 3665-8. drach, p. 1939. Mue et cycle d’intermue chez les Crustaces Decapodes. Ann. inst, oceanog. Paris (n.s.), 19, 103-391. Neville, A. c. 1970. Cuticle ultrastructure in relation to the whole insect. In Insect Ultrastructure, Roy. Ent. Soc. Symp. 5 (ed. A. c. neville). Oxford: Blackwells. and luke, b. m. 1969a. Molecular architecture of adult locust cuticle at the electron microscope level. Tissue & Cell, 1, 355-66. 1969 b. A two-system model for chitin-protein complexes in insect cuticles. Ibid. 1, 689-707. thomas, m. g., and zelazny, b. 1969. Pore canal shape related to molecular architecture of arthropod cuticle. Ibid. 1, 183-200. rolfe, w. d. i. 1962. The cuticle of some middle Silurian ceratiocaridid Crustacea from Scotland. Palaeontology, 5, 30-51. rome, d. r. 1936. Note sur la microstructure de l’appareil tegumentaire de Phacops (JPh.) accipitrinus maretiolensis R. & E. Richter. Bull. Mus. Hist. nat. Belg. 12 (31), 1-7. explanation of plate 30 Fig. 1 . Propodite segment of cheliped of Eryma stricklandi, x 1 1 ; Oxford Clay. Fig. 2. Photomicrograph of section cut vertical to surface of cuticle of Eryma stricklandi between crossed polaroids showing lamellation and pore canals with sinuous shape (arrowed) in phase with the lamellae, x 500. explanation of plate 31 Fig. 1. Photomicrograph of section cut vertical to surface of cuticle of living Astacus fluviatilis viewed between crossed polaroids, X 300. Fig. 2. Photomicrograph of section cut vertical to surface of cuticle of Eryma stricklandi viewed between crossed polaroids, x 800. Exo, exocuticle ; endo, endocuticle. explanation of plate 32 Fig. 1. Photomicrograph of section cut almost tangential to surface of cuticle of living Astacus fluviatilis, viewed in phase contrast; the pore canal sections, seen here in the endocuticle, form a parabolic pattern, x 2500. Fig. 2. Photomicrograph of section cut almost tangential to surface of fossil cuticle of Eryma stricklandi, viewed between crossed polaroids and compensated by a first order red plate ; the pore canals again form a parabolic pattern, x 1000. Palaeontology, Vol. 14 PLATE 30 NEVILLE and BERG, Jurassic crustacean cuticle Palaeontology, Vol. 14 PLATE 31 NEVILLE and BERG, Jurassic crustacean cuticle Palaeontology, Vol. 14 PLATE 32 NEVILLE and BERG, Jurassic crustacean cuticle NEVILLE AND BERG: JURASSIC CRUSTACEAN CUTICLE 205 ST0RMER, l. 1930. Scandinavian Trinucleidae, with special reference to Norwegian species and varieties. Norske Vidensk. Akad. Oslo, I, Mat. Naturv. Kl. 4, 1-111. travis, d. f. 1963. Structural features of mineralization from tissue to macromolecular levels of organization in the Decapod Crustacea. Ann. N.Y. Acad. Sci. 109, 177-245. A. C. NEVILLE C. W. BERG ARC Unit of Insect Physiology Oxford University Department of Zoology Typescript received 22 June 1970 South Parks Road, Oxford A NEW XIPHOSURAN GENUS FROM LOWER CRETACEOUS FRESHWATER SEDIMENTS AT KOONWARRA, VICTORIA, AUSTRALIA by e. f. riek and Edmund d. gill Abstract. An excellently preserved xiphosuran, representing a new genus, Victalimulus, is preserved in fresh- water strata with fish, insects, and plants from Koonwarra, Victoria. The new genus is similar both to the living Limulus and to the Mesozoic Mesolimulus. Both fossil genera are referred to the Limulidae. The preserved speci- men is considered to be a mature adult that migrated from the sea in order to breed in fresh water. Xiphosura are rarely preserved as fossils, so this well-preserved specimen from Koon- warra is an important addition to the history of this marine group. The appendages are preserved, although it is sometimes difficult to distinguish details because of super- imposed impressions of other structures from both dorsal and ventral surfaces. The outlines of the overlapping lamellate opisthosomal appendages, with their hair fringes, are distinguishable through the more heavily sclerotized operculum. The apex of the opisthosomal axis is missing except for a part of the left apical lobe. A small fragment of the caudal style is preserved. The specimen P22410-3 in the National Museum of Victoria, Melbourne, is from a road cutting on the South Gippsland Highway, at a point where road, railway, and river are close together, 1-5 miles east of Koonwarra, South Gippsland, Victoria. The specimen is preserved as clear impressions in siltstone. The fossil was found by James McQueen when working over a load of siltstone taken home for breaking up in search of fossils. Later, his reject material and the site were examined in the hope of finding the missing parts of the fossil, but without success. Geology. Over 9000 ft of sediments were accumulated in the South Gippsland Basin. They consist of felspathic sandstones and siltstones, with occasional conglomerates and some thin bands of black coal. A soil horizon with silicified stumps in position of growth was observed in the Cape Patterson area exposed on a shore platform, but the formation is essentially a lacustrine one. No marine beds are known. The great thick- ness of sediments proves rapid subsidence, so it is not surprising to find slump structures, and evidence of subaqueous slides. Plant fossils (Carrol 1962) are common but others are rare. Before the present site was discovered, the only animals known from the basin were a dinosaur (represented by a claw), a lungfish (represented by a Ceratodus tooth plate), and a few indefinite fragments. Palaeoecology. The xiphosuran is preserved in siltstone together with abundant plants, fish, phyllopod Crustacea (conchostracans and anostracans), and an aquatic insectan fauna in such unusual circumstances as to ensure excellent preservation. The insect fauna consists mainly of the nymphs of Ephemeroptera (mayflies), Plecoptera (stone- flies), and Odonata (dragonflies and damsel-flies), and the larvae of nematocerous [Palaeontology, Vol. 14, Part 2, 1971, pp. 206-10, pi. 33.] RIEK AND GILL: LOWER CRETACEOUS XIPHOSURAN 207 Diptera (midges) and Coleoptera (beetles). This particular assemblage of immature insects could only occur in an uncontaminated freshwater habitat. The presence of a limulid in this environment suggests that it had migrated there for breeding; if so, it was mature. Such characters of Victalimulus mcqueeni that appear to be juvenile as compared with living limulids are therefore regarded as adult characters of the species. CLASSIFICATION Victalimulus clarifies much of the probable structure of Mesolimulus and other Meso- zoic Limulacea. This, combined with the interpretation of the structure of Austrolimulus fetched (Riek 1968) from the Triassic of Australia, necessitates the relegation of the genera of the Mesolimulidae to one or other of the families Palaeolimulidae and Limulidae. Class MEROSTOMATA Subclass XIPHOSURA Superfamily limulacea Family limulidae Limulidae auct. Mesolimulidae Stormer 1952 (in part) Diagnosis of family. Opisthosoma consolidated; segmentation and axial furrows of dorsal shield indistinct although indicated at least by apodemes. Ophthalmic ridges not meeting in front of cardiac lobe. Genal spines moderately to strongly produced, directed postero-laterally, posteriorly, or with their apices converging. Jurassic to present. Included genera. Limulus (Quaternary), Tachypleus (Quaternary and Tertiary), Carcino- scorpius (Quaternary), Mesolimulus (Jurassic), Psammolimulus (Triassic), Victalimulus gen. nov. (Cretaceous). Discussion of genera. Stormer (1952) established the family Mesolimulidae for three fossil genera from the Mesozoic which he considered showed more affinity to living Limulidae than to Paleolimulus (Paleolimulidae). The structure of all three genera is imperfectly known but at least one of the included genera does not conform with the definition of the family, and, in addition, this definition differs only slightly from that of the Limulidae. Limulitella has the body form of Paleolimulus ; indications that the ophthalmic ridges meet in front; genal spines laterally directed; distinct longitudinal axial furrows; relatively wide operculum ; and narrow flat marginal zone to the doublure of the opis- thosoma. The apparent absence of a free apical opisthosomal segment and transverse segmentation of the axis are probably due to inadequate preservation. The genus is transferred to the Paleolimulidae. When its structure is more adequately known, it may prove to be a synonym of Paleolimulus. Psammolimulus has a very large genal spine, directed posteriorly, and a reduced opisthosoma that ends in a pair of spine-like projections. The free lobe apparently extends laterally beyond the main body of the opisthosoma. Although the lateral margins of the opisthosoma are not lobed there are short, stout, moveable spines. The 208 PALAEONTOLOGY, VOLUME 14 genus was compared with Austrolimulus by Riek (1968). However, the reconstruction of Psammolimulus by Meischner (1962) shows a distinctly different form of the genal spines and of the posterior region of the opisthosoma. Psammolimulus is a very distinct genus although in basic structure it is similar to Limulus, with all segments of the opisthosoma fused and without indications of the sutures. It is transferred to the Limulidae. The structure of Mesolimulus is moderately well known. It appears to differ from living limulids in the development of more clearly defined axial furrows on the opistho- soma and shorter genal spines. These are attributes of juvenile living limulids. Some of the other observed differences may be due to the manner of preservation. The differences are so slight that Mesolimulus is considered to warrant only generic recognition. Mesolimulus is therefore transferred to the Limulidae. Stormer’s (1952) diagnosis of the Mesolimulidae depends on their possession of a smaller range in size, less prolongation of genal angles, more distinct axial furrows, and of more anterior placement of the first pair of marginal opisthosomal spines than in the Limulidae, but these are only quantitative differences (as against qualitative ones) that we consider inadequate for the definition of a family. We do not agree that the position of the first pair of marginal spines is a valid difference. Victalimulus, the new genus described from the Lower Cretaceous of Koonwarra, is intermediate in some characters between Mesolimulus and the living Limulidae, but in other characters this is not so. Separate generic status is considered warranted. The genus is referred to the Limulidae and compared with Limulus and Tachypleus. Genus Victalimulus gen. nov. Type species. Victalimulus mcqueeni sp. nov. Diagnosis of genus. Limulid combining characters of Mesolimulus and Limulus , resemb- ling Tachypleus and Limulus but with an opisthosomal doublure that evenly expands anteriorly whereas at least in Limulus the margins are parallel; lateral processes of opisthosoma long and tapering regularly; and genal lobes tapering regularly to apex. Cardiac lobe of prosoma with a median crest bearing three protuberances or spines. Axial furrows bordering the cardiac lobe converging and almost meeting anteriorly. Ophthalmic ridge defined for a moderate distance anterior to the eye, and not converging strongly anteriorly. Outer margin of genal spine parallel to median axis of body. Opisthosoma with strongly convex margins; free lobe distinct. Axial furrows indicated by six pairs of relatively deep pits (apodemes) extended antero-mesally as distinct grooves. Marginal spines long, directed posteriorly. Prosoma with relatively wide, flat doublure that evenly widens anteriorly. Structure of appendages imperfectly known but comparable with Limulus. EXPLANATION OF PLATE 33 Figs. 1-5. Holotype of Victalimulus mcqueeni. 1, P22410; slightly less than natural size. 2, P22411-12; reversed lighting, slightly less than natural size. 3, Detail of apodemes on opis- thosoma; c. x2. 4, Hair fringes on opisthosomal appendages ; c. x 3. 5, Opisthosomal spines; c. X 2. Palaeontology, Vol. 14 PLATE 33 RIEK and GILL, Lower Cretaceous xiphosuran RIEK AND GILL: LOWER CRETACEOUS XIPHOSURAN 209 Victalimulus mcqueeni sp. nov. Plate 33 Holotype. Nat. Mus. Viet. P22410-3. Description of holotype. As for the genus but with the following details: length along mid-line to opisthosomal apex, 8-7 cm (estimated because apex not complete); length of prosoma along mid-line, 5-0 cm; ditto to line joining ends of genal spines, 7-0 cm; width at bases of genal spines, 8-5 cm; greatest width of opisthosoma, 5-8 cm. As preserved, the specimen is slightly convex; the carapace was originally thin and vaulted. Cardiac lobe of prosoma with median crest bearing three protuberances or spines, the posterior two being better defined (as preserved) than the anterior one. The anterior one was pressed forward during the flattening involved during fossilization, and so its less conspicuous nature is probably due to its position rather than indefiniteness in the original carapace. In specimens of Limulus available to us, these spines are very well defined in juveniles, but are indistinct in adults. The left genal angle of the prosoma is preserved. It tapers regularly to a sharp point. The internal margin of the genal lobe is comparable with that in Tachypleus gigas and notably less curved than in the living Limulus polyphemus. The doublure of the prosoma widens evenly when followed anteriorly, whereas in Limulus the margins of the doublure are parallel until the inner edge begins to turn posteriorly. The outer margin of the doublure is displaced in the fossil from the outer margin of the prosoma over the mid-section of the right side, showing a weakness at this junction similar to that in the living Limulus. On the margins of the opisthosoma, the lobes are relatively long (of the order of 7-0 mm) and in outline almost bilaterally symmetrical. The intercalated spines are distinctly shorter, c. 4 mm, whereas in Limulus polyphemus the lobes are asymmetric in outline (the anterior being significantly longer than the posterior) and the spines are much longer than the lobes at all stages of growth. In L. polyphemus the width of the spine base is about as wide as the lobe base in the anterior part of the opisthosoma, whereas in Victalimulus mcqueeni the spine bases are of the order of half the diameter of the lobe bases. The spines are crested, and possess flattened borders lateral to the crests, whereas in L. polyphemus, they are broadly, moderately, and evenly convex with linear lateral borders, i.e. they are not crested. The free lobe at the anterior left corner of the opisthosoma is preserved but partially obscured by the last (non-chelate) leg. It apparently extends beyond the hidden first lobe. On fragment P22413 is the left apical spine or lobe of the opisthosoma; it shows that the spine is terminally sharp, and both longer and much more laterally directed than in L. polyphemus. The axis of the opisthosoma carries three median spines similar to the anterior and posterior spines on the axis of L. polyphemus, but with an additional spine. In L. polyphemus there are three spines, the most posterior being that on the apex, which area is not preserved in the fossil species. In addition to the other two, there is present an extra smaller spine on the segment anterior to the middle spine of Limulus. The axes of the apodemes are directed obliquely to the mid-line, rather than aligned as they are in Limulus. In Victalimulus the raised margin of the inner edge of the opisthosomal doublure is not completely preserved although the portion preserved indicates that the margin 210 PALAEONTOLOGY, VOLUME 14 is rounded and subparallel to the lateral margin whereas in Limulus this inner margin has straight lateral margins that each form a reasonably well-defined angle with the caudal margin. The fragment of caudal spine (P22413) is similar to that in Limulus in being crested and having tapering margins, but it is too small for any significant comparison. The apex of the left posterior appendage of the prosoma is preserved. Two subequal apical spines are present. They are about the same length as the interlobal spines of the opisthosoma (4 mm), and are sharply crested. The flattened digging spines reached the apex of the terminal segment. Only indications of the more anterior appendages are to be seen, but the chela of one of the more posterior walking legs on the left side is clearly preserved. The spinose gnathobase of the second pair of appendages is distinct on both sides. The very long marginal hair fringes of some of the overlapping foliaceous abdominal appendages are preserved on the left side. Remarks. The specific name is in honour of James McQueen of Korumburra who found the fossil and presented it to the National Museum of Victoria. We are indebted to Mr. L. F. Costermans for recognizing the value of this fossil and advising James McQueen to take it to the National Museum. The photographs were prepared by Mr. John Green, Canberra. REFERENCES carrol, E. J. 1962. Mesozoic fossil insects from Koonwarra, South Gippsland, Victoria. Aust. J. Sci. 25, 264-5. meischner, K.-D. 1962. Neue Funde von Psammolimulus gottingensis (Merostomata, Xiphosura) aus dem Mittleren Buntsandstein von Gottingen. Palaont. Zeitschr (H. Schmidt-Festband), 185-93. riek, e. f. 1968. Re-examination of two arthropod species from the Triassic of Brookvale, New South Wales. Rec. Aust. Mus. 27, 313-21. stormer, L. 1952. Phylogeny and taxonomy of fossil horse-shoe crabs. J. Paleont. 26, 630-9. E. F. RIEK CSIRO Division of Entomology P.O. Box 109, Canberra City A.C.T., 2601 Australia Typescript received 23 June 1970 EDMUND D. GILL National Museum of Victoria THE PRESUMED HEADS OF HOMOPTERA (INSECTA) IN THE AUSTRALIAN UPPER PERMIAN by E. F. RIEK Abstract. Two fossil insects, Permocephalus knighti Evans and Permocapitus globulus Evans, from the Upper Permian of Belmont, were considered to be Homoptera by Evans. The portions figured as heads are shown to be mesonota. Their form, when considered with the metanotum and other preserved body structures, indicates that they were parts of endopterygote insects. They are compared with Recent Pamphiliidae (Hymenoptera : Symphyta) on the basal rudiments of venation, head shape, and development of the ovipositor, but not formally referred to the Hymenoptera because of lack of knowledge of more than the basal wing venation. Evans (1943a, b ) described the supposed heads of several specimens of Upper Permian insects from Belmont, Australia, under the names Permocephalus knighti Evans and Permocapitus globulus Evans. Line drawings were given of the ‘heads’ of all six speci- mens, and in the earlier of the two papers an excellent photograph was provided (Evans 1957). The photograph of the holotype of Permocephalus knighti Evans 1943a (PI. 34, fig. 1) shows clearly the body of an insect from which the head and pronotum, and apex of the abdomen are missing. The large mesonotum, smaller metanotum, and basal seven segments of the abdomen and portion of the female genitalia are distinct. The structure of the metathorax is similar to that of the mesothorax except that the prescutum is reduced. The segments of the abdomen are short and broad. The enlarged tegula is defined and the postero-lateral lobe of the pronotum is visible in front of the tegula. In the holotype of Permocapitus globulus (PI. 34, fig. 2) the head, prothorax, and fore legs are preserved anterior to the presumed head figured by Evans. Evans (1957) gave a reconstruction of the head (= mesonotum) of Permocephalus knighti. This reconstruction (text-fig. 1b) is based mainly on the specimens referred to Permocephalus knighti but the eyes were added from Permocapitus globulus. He indic- ated that although in the earlier two papers he had regarded these structures as the heads of Homoptera and had referred them to the Protopsyllidiidae on their small size and the fact that species of that family were abundant in the strata, in the 1957 paper he regarded their structure as ‘so different from what the head of the proto- psyllidiid might be supposed to have been like’ that he considered he may have been in error in regarding them as heads and that ‘they might be the impressions of parts of the thorax of small adult insects’. However he ‘failed to identify them as thoracic structures and so, for the time being, . . . assumed that they are the heads of small Homoptera’. He listed those structures which are undoubtedly preserved in the fossils. These included the outline of the ‘head’ apart from the eyes; the two V-shaped sutures; and the two sclerites lying between the arms of the inverted V. The other structures, including eyes, antennae, and lobes of the clypeus, were inferred to a considerable extent through regarding the structures as heads. Contrary to Evans’s conclusions, I consider that each of the structures figured by him [Palaeontology, Vol. 14, Part 2, 1971, pp. 211-21, pis. 34-35.] 212 PALAEONTOLOGY, VOLUME 14 text-fig. 1a, b, d-g. Permocephalus knighti Evans, a, ‘Head’ of holotype; Australian Museum no. 39865 (from Evans 1943a). b. Reconstruction of head (from Evans 1957). d-g, from Evans 19436. d, Australian Museum no. 39967. e, no. 39944. f, no. 40449. g, no. 39945, listed in literature as no. 33945. c, Permocapitus globulus Evans, holotype (from Evans 19436); Australian Museum no. 40078. represents a thoracic segment of a small insect, and that they can be compared with similar structures in the thorax of Recent Neuroptera, Raphidioptera, and a few primitive Hymenoptera, and to a lesser extent other endopterygote insects. In size they are com- parable with a thoracic segment of most Chrysopidae and Hemerobiidae or with small species of Symphyta (Hymenoptera). They can also be compared with mesonota of some E. F. RIEK: AUSTRALIAN PERMIAN HOMOPTERA 213 exopterygote groups such as Psyllidae (Hemiptera) and Psocoptera but there is less similarity than with the endopterygote orders. Evans considered that two species (and genera) were represented in the material he studied but he gave no indication of those attributes which he considered diagnostic of Permocephalus, nor did he compare the two species. No two specimens are identical and the basis for generic separation is not evident either in the specimens or from his illustrations, reproduced here (text-fig. 1a, c-g). The differences are considered due to orientation and to distortion during fossilization. The most outstanding attribute of all these thoracic structures is the large, distinctly produced scutellum with a de- pressed area over its basal portion that gives the appearance of a transverse groove in the basal half of the scutellum. DESCRIPTION OF FOSSILS At least three of the six specimens are female : the holotype of both species and no. 39945 (PI. 34, figs. 1-3 ; text-fig. 2 a-d). The other three specimens lack the apex of the abdomen. The head is partly preserved only in the holotype of Permocapitus globulus and no. 39944. The bases of the wings are present in no. 39944 (PI. 35, figs. 1, 2) and indistinctly preserved in no. 39967. The subequal basal two segments of the hind tarsus are clearly preserved in no. 39967 : the tarsus was apparently 5-segmented (PI. 34, fig. 4 ; text-fig. 2d). The legs are of moderate length and the femora slightly expanded. The abdomen is short and broad, wide at base (sessile); segment 1 has, apparently, a strong oblique groove close to the base although this may represent a more heavily sclerotized basal portion of the segment. The abdomen has a distinct pleural doublure and the sternites are deeply impressed. The ovipositor is stout and straight: it arises on a level with the caudal margin of tergite 7. The apex of the ovipositor is not preserved in any specimen so that its relative length remains unknown, although it was almost certainly short (PI. 34, figs. 2, 3). The head is imperfectly preserved but the right eye and lateral margin of the head are distinct in no. 39944 (PI. 35, figs. 1, 2). The head has been damaged in the holotype of Permocapitus globulus (no. 40078) (PI. 34, fig. 2; text-fig. 2b) in the process of mechani- cally exposing this portion of the fossil but it bears a broad median zone that widens anteriorly, apparently in the region of the eye. The distinct, very short pronotum is divided by a longitudinal groove in no. 39944. The displaced prothorax is preserved in the holotype of Permocapitus globulus although its form is indefinite and confused with the fore coxae. The mesonotum has a strong, more or less transverse ridge about the middle of its length. The metanotum is only slightly more than half as long as the mesonotum and, although of similar form, its prescutum is smaller : antero-laterally it is raised and separated from the median zone by a short, deep, oblique groove. In no. 39944 the basal structure of both fore and hind wing is preserved on the right side and the basal half of the hind wing on the left side of the body (PI. 35, figs. 1, 2). The wings are partly folded. Only the costal margin and the stem of R are defined in the fore wing. R is distinctly swollen at base and there are indications of some basal axillaries. The costal margin of the hind wing is not sharply defined due to the overlying vein R. The first distinct vein is M+CuA which is preserved to just beyond the separation of text-fig. 2. Diagrams for comparison with figures on Plate 34. a, no. 39865; compare with fig. 1. b, no. 40078; compare with fig. 2. c, no. 39945; compare with fig. 3. d, no. 39967; compare with fig. 4. E. F. RIEK: AUSTRALIAN PERMIAN HOMOPTERA 215 M and CuA. The basal portions of the first two anal veins diverge strongly at first but then they converge slightly. Cross veins are not indicated. DORSAL THORAX OF SOME ENDOPTERYGOTE ORDERS FOR COMPARISON WITH THE FOSSIL SPECIES Although there is the same basic thoracic structure in Mecoptera, Megaloptera, Raphidioptera, Neuroptera, and primitive Hymenoptera, the orders with which the fossils can be most closely compared, there are differences in proportions between the various components that are diagnostic of Recent representatives of each order. There is little difference in structure between mesothorax and metathorax in Mecoptera, Megaloptera, Raphidioptera, and Neuroptera although the metathorax is often some- what smaller and has a smaller prescutum than the mesothorax whereas there is not only a marked contrast in structure between these two thoracic segments but the meta- thorax is also very much smaller than the mesothorax in most primitive Hymenoptera. The mesonotum of most Mecoptera does not vary to any marked extent from the basic type that is present in Choristci australis (text-fig. 3a). The scutellum is clearly defined but the division between prescutum and scutum is indistinct. The scutellum is short and broad, rounded at base and truncate at apex. The prescutum is convex and without a median longitudinal sulcus. This form of the mesonotum occurs in all families with the exception of Bittacidae and Boreidae. The Boreidae have a very specialized structure in all probability correlated with reduction or absence of wings. In Bittacidae (text-fig. 3b) the mesonotum is elongate, each parapsis (lateral scutum) is produced anteriorly into a partly separated, large, rounded, bulbous projection bordering the prescutum which in consequence is more distinctly defined than in the other families. Also, the scutellum is slightly more tapered anteriorly in Bittacidae than in the other families. Megaloptera all have a form of the mesonotum similar to that which occurs in Archichauliod.es gut tif erus (text-fig. 3d). The mesothorax and metathorax are closely similar in size. The thorax of Raphidioptera is similar to that of Megaloptera, although the scutellum is slightly produced at apex. There is a wide range in thoracic structures in the Hymenoptera but the mesonotum of Xyelidae (text-fig. 3e) and Pamphiliidae (PI. 35, figs. 3, 4) has a generalized form comparable with that of Mecoptera and Megaloptera. Neuroptera (text-figs. 3c, 3f, 4 a-h) show variation not only in the form of the mesono- tum but also in the relationship between mesothorax and metathorax. These two thoracic segments are subequal in the more generalized species but the metathorax is often smaller in the more advanced species. This difference is usually only of moderate proportions but the metathorax is distinctly reduced in Nemopteridae and the few other species in which the hind wing is reduced. Although there is considerable variation in development of the mesonotum there is also a similarity between all Neuroptera that enables easy recognition of this order. In general, Myrmeleontoidea (Myrmeleontidae, Ascalaphidae, Stilbopterygidae, Nemopteridae, Nymphidae) (text-fig. 3c) form a distinct group that can be distinguished on the form of the scutellum. This is large, with convex upper surface, rounded at base and truncate at apex. There is no depressed area over its basal portion or this is both minute and situated anterior to the rounded base, and there is usually a shallow transverse 216 PALAEONTOLOGY, VOLUME 14 groove close to the apex, but the groove is sometimes absent (Stilbopterygidae) or situated about the middle of the scutellum (Ascalaphidae). Nymphidae (text-fig. 3f) differ from other Myrmeleontoidea as regards thoracic structure and the mesonotum is similar to that which occurs in Osmyloidea and Hemerobioidea. Each of the non-myrmeleontoid families also, with few exceptions, can be recognized on the distinctive characteristics of its dorsal thorax. The one attribute they have in common that distinguishes them from the Myrmeleontoidea, with the exception of Nymphidae, is a depressed area at the base of the scutellum. This area rarely extends beyond the middle of the scutellum. Coniopterygoidea (Coniopterygidae) have a short, very broad mesonotum with small prescutum. Mantispoidea (Mantispidae, Berothidae, Sisyridae) have a relatively long scutum (text-fig. 4e) and the two parapsides (lateral scutum) are usually separated by a deep, median, longitudinal sulcus (Berothidae and Sisyridae). In most Mantispidae there is a deep pit in a position corresponding to the anterior end of the groove that occurs in Berothidae and Sisyridae. In a few Mantis- pidae (Platymantispinae) the pit is absent. The scutellum is usually produced at apex but it is truncate in most Mantispidae and only very slightly produced in the others. The prescutum is distinctly wider than the scutellum and the grooves separating the prescutum from the scutum are almost transverse. The grooves are very deep in Bero- thidae and most Mantispidae but they are indistinct in Sisyridae and some Mantispidae. The prescutum is produced antero-laterally in most Mantispidae. Hemerobioidea (Hemerobiidae, Chrysopidae, and Psychopsidae) and Osmyloidea (Ithonidae, Dilaridae, Polystoechotidae, Osmylidae, Neurorthidae) are less easily characterized than are Mantispoidea. They usually have a distinct, but short, transverse ridge at meson on the scutum (Hemerobiidae and Chrysopidae) (text-fig. 4f, g) or when it is absent (Psychop- sidae) (text-fig. 4h) the scutellum is distinctly larger than the prescutum. Such a ridge occurs also in Myrmeleontoidea, Mantispoidea, and a few Osmyloidea though it is broken at meson when the two parapsides are separated by a deep median longitudinal sulcus (Berothidae and Sisyridae). The scutellum is usually strongly produced at apex in Hemerobiidae (text-fig. 4g) and Psychopsidae (text-fig. 4h) and to a lesser extent in Chrysopidae (text-fig. 4f). The prescutum is broad though it does not always appear so through varying development of the scutellum. It is longer than the scutellum in Hemerobiidae, relatively shorter in Chrysopidae and relatively quite short in Psychop- sidae in which the scutellum is very large. In Osmyloidea the transverse ridge of the scutum is often absent (Ithonidae: text-fig. 4b) though there is a faint to distinct ridge in some Osmylidae (text-fig. 4c), Polystoechotidae (text-fig. 4d) and Dilaridae (text-fig. 4a). The scutellum is usually only slightly produced at apex but it is distinctly produced in Osmylidae (text-fig. 4c), Neurorthidae and Polystoechotes (text-fig. 4d). The depressed area at the base of the scutellum extends beyond the middle in Ithonidae (text-fig. 4b) and almost so in Polystoechotidae (text-fig. 4d). EXPLANATION OF PLATE 34 Fig. 1. Permocephalus knighti, holotype; no. 39865, c. X 14. Figs. 2-4. Permocapitus globulus, c. X 14. 2, Holotype; no. 40078. 3, no. 39945. 4, no. 39967. EXPLANATION OF PLATE 35 Figs. 1-2. Permocapitus globulus. 1, Specimen 39944; c. Xl5. 2, Drawing of same specimen. Figs. 3-4. Pamphilius sp. 3, Diagram, dorsal thorax. 4, Dorsal view with wing bases; c. X 8. Palaeontology, Vol. 14 PLATE 34 RIEK, Australian Permian Homoptera Palaeontology, Vol. 14 PLATE 35 3 4 RIEK, Permian and recent Homoptera E. F. RIEK: AUSTRALIAN PERMIAN HOMOPTERA 217 text-fig. 3. Mesonota of Recent insects, a, Chorista australis (Mecoptera: Choristidae). b, Harpobittacus australis (Mecoptera: Bittacidae). c, Acanthaclisis sp. (Neuroptera: Myrmeleontidae). d, Archichauliodes guttiferus (Megaloptera : Corydalidae). e, Macrn- Macroxyela sp. (Hymenoptera : Xyelidae). f, Nymphes sp. (Neuroptera: Nymphidae). C 7998 Q 218 PALAEONTOLOGY, VOLUME 14 text-fig. 4. Mesonota of Recent insects, a, Dilar sp. (Neuroptera : Dilaridae). b, Varnia sp. (Neuroptera: Ithonidae). c, Stenosmylus sp. (Neuroptera: Osmylidae). d, Polystoechotes sp. (Neuroptera: Poly- stoechotidae). e, Spermophorella sp. (Neuroptera: Berothidac). f, Chrysopa sp. (Neuroptera: Chryso- pidae). G, Psychobiella sp. (Neuroptera : Hemerobiidae). h, Psychopsis sp. (Neuroptera : Psychopsidae). E. F. RIEK: AUSTRALIAN PERMIAN HOMOPTERA 219 DISCUSSION The fossil species has a short wide scutum, and the large scutellum is produced at apex and has a depressed basal area that does not extend beyond the middle of the scutellum. On this combination of attributes it can be compared with Neuroptera (many Osmyloidea, many Hemerobioidea, and with primitive Myrmeleontoidea). The similarity is closest to Osmylidae (text-fig. 4c), Chrysopidae (text-fig. 4f), and Nym- phidae (text-fig. 3f). Each of these families is placed in a different superfamily of the Neuroptera and each is, in most respects, one of the most generalized families within its superfamily, so in all probability this form of thoracic structure is the most primitive type within the Neuroptera, and possibly of all endopterygote orders. The presence of an ovipositor and its structure suggests relationship to some Recent Neuroptera (Dilaridae and platymantispine Mantispidae), Raphidioptera, and sym- phytan Hymenoptera. The ovipositor usually exceeds the length of the abdomen in Neuroptera and Raphidioptera whereas it is unusual for it to be exserted to a marked extent in Symphyta, although the structure is stout and conspicuous in ventral view of the abdomen. The ovipositor of the fossil species is apparently comparable with that of Recent Symphyta. The head, apparently almost as long as wide, was produced postero-laterally so that it was more or less rectangular, had large, laterally placed, ovoid eyes, and a post-ocular region that was about as long as the eye. This type of head resembles that of many Symphyta, especially Pamphiliidae and most Tenthredinoidea, and differs from that of most other Endopterygota. The general pattern of the admittedly very incomplete venation is more comparable with that which occurs in primitive Hymenoptera (Symphyta) than in other endo- pterygote orders. On the reduced condition of the venation, the species can be compared with Hemiptera and Psocoptera but these orders are excluded on thoracic structure. The structure of the anterior portion of the metanotum suggests that cenchri may have been developed mesad of the oblique groove (text-fig. 2a) : cenchri occur only in the majority of symphytan Hymenoptera. The fact that the body structure is well preserved is indicative of a heavily sclerotized cuticle, which is of more usual occurrence in Hymenoptera than in other endoptery- gote orders. The known structure of this Upper Permian species can be compared more closely with that of Triassoxvela striata Rasnitsyn 1964 (Hymenoptera: Symphyta), from the Triassic of central Asia, than with other known Palaeozoic and early Mesozoic insects. The two species differ, however, in the shape of the mesonotum: the scutellum is distinctly produced at the apex in Permocephalus whereas it is not produced to any marked extent in TriassoxyeJa which resembles Recent Xyelidae. The Upper Permian species is considered to be more plesiomorphic in this attribute than the Triassic one. The known morphology can also be compared with that of several Jurassic Symphyta, especially Xyelidae (Rasnitsyn 1968) and Anaxyelidae (Martynov 1925). The endopterygote orders Mecoptera, Neuroptera, Megaloptera, Trichoptera, and Coleoptera are recorded from the same horizon as the fossils under discussion and there is evidence that Diptera were also present (Riek 1953, 1970). Recognizable remains of Hymenoptera, Raphidioptera, Lepidoptera, and Strepsiptera have not been recorded. 220 PALAEONTOLOGY, VOLUME 14 Most endopterygote orders represented in the same horizon, by wings alone, can be excluded from consideration because their thoracic structure is specialized. Coleoptera have a metanotum at least as large as the mesonotum. Trichoptera and Diptera have a greatly enlarged, elongated mesonotum that is also usually very different in form from the metanotum. Mecoptera all have a short, wide mesoscutellum. Megaloptera, which are only doubtfully recorded, and Raphidioptera, which have not been recognized in the horizon, also would be excluded on the structure of other parts of the body: Megaloptera have a large pronotum and Raphidioptera a long one. The Neuroptera, some of which have a thoracic structure comparable with that of the fossil species, are represented in the same horizon by wing fragments of primitive types that have a dense venation and numerous cross veins whereas the fossil species under discussion has a greatly reduced venation. Highly evolved Neuroptera with reduced venation, comparable with that of Chrysopidae, Mantispidae, and Sisyridae, are unknown as early as the Upper Permian. Unfortunately the body structure of Permian Neuroptera is not known so that comparisons can only be made with Recent species. Thus, the fossils under discussion cannot be placed with certainty in any of the orders recorded from the same horizon, although, of the recorded orders, they approach most closely to the Neuroptera. The heavily sclerotized cuticle, shape of the head, structure of the dorsal thorax and relative development of mesonotum and metanotum, and the pattern of the very reduced basal venation, indicate that the specimens are almost certainly the bodies of primitive Hymenoptera. With respect to extant species, they can be compared most closely with Pamphiliidae from which they differ in the more generalized structure of the thorax, and in the relatively larger metathorax. Although they resemble generalized extant Neuroptera in the structure of the thorax they differ noticeably in the other mentioned attributes. Permocephahts knight i Evans 1943u is not formally referred to the order Hymenoptera mainly because of the emphasis placed on venation in the allocation of early insects to definitive orders. It would also be the earliest record of the order and, as such, there should be no doubt as to its correct assignment. However, the order Hymenoptera was undoubtedly established at least before the end of the Permian because there is no doubt that Symphyta that can be referred to families with extant species were present in the Lower Triassic, and, as such, show no close relationship to other endopterygote orders. Acknowledgements. Sincere appreciation is extended to Mr. R. H. Ewins and Miss Sybil Curtis for preparation of the line illustrations and to Mr. C. Lourandos for the photographs. REFERENCES evans, j. w. 1943n. Two interesting Upper Permian Homoptera from New South Wales. Trans. R. Soc. S. Aust. 67, 7-9. 19436. Upper Permian Homoptera from New South Wales. Rec. Aust. Mus. 21, 180-98. 1957. Some aspects of the morphology and interrelationships of extinct and recent Homoptera. Trans. R. ent. Soc. Lond. 109, 275-94. martynov, a. v. 1925. To the knowledge of fossil insects from Jurassic beds in Turkestan. 3. Hym- enoptera, Mecoptera. Bull. Acad. Sci. Leningrad, 19, 753-62. E. F. RIEK: AUSTRALIAN PERMIAN HOMOPTERA 221 rasnitsyn, a. p. 1964. New Triassic Hymenoptera of Central Asia. Paleont. Zh. 1964 (1), 88-96. 1968. New Mesozoic sawflies (Hymenoptera, Symphyta). In (rohdendorf, b. b., ed.) Jurassic Insects of Karatau. Nauka, Moscow (In Russian). riek, e. f. 1953. Fossil mecopteroid insects from the Upper Permian of New South Wales. Rec. Aust. Mus. 23, 55-87. 1970. Fossil history. In Insects of Australia, 168-86. Melbourne. e. f. riek CSIRO Division of Entomology P.O. Box 109, Canberra City Typescript received 14 July 1970 A.C.T., 2601 Australia SOME PERMIAN TRILOBITES FROM ■ EASTERN AUSTRALIA by robin e„ wass and maxwell r. banks Abstract. A new genus of proetid trilobite, Doublatia, occurs in the Permian of eastern Australia. It is repre- sented by the type species, Doublatia inflat a gen. et sp. nov., in the Artinskian Branxton Formation of New South Wales and by two species, D. pyriforme sp. nov. and Doublatia sp., in slightly older beds, the Enstone Park Lime- stone in north-eastern Tasmania. The new genus is more closely related to Ditomopyge than to other proetids. Two pygidial forms not referable to Doublatia also occur in the Permian of eastern Australia. The Permian faunas of eastern Australia have been studied since the early nineteenth century, many detailed collections have been made and from them monographs on various groups have resulted. During the past decade there have been many studies of a revisionary nature but trilobites have received little attention because they are rare and their remains fragmentary. Whereas Teichert (1944) has described Ditomopyge meridionals and D. sp. from Western Australian Permian strata, the only trilobite named specifically from the eastern Australian Permian is ‘'Griffithides'’ dubius Etheridge (1872, p. 338, pi. 18, fig. 7), described and figured from a single pygidium and thorax joined to a damaged cranidium from the ‘Don River, Queensland’ in strata then stated to be of Carboniferous age. The inferred number of thoracic segments was within the range 10-12. Jack and Etheridge Jr. (1892, pi. 7, fig. 12) refigured this specimen, referring its horizon to the Permo-Carboniferous Gympie Beds; they located the Don River (p. 215) as a tributary of the Dawson River and not as might have been supposed the Don River, near Bowen. They erroneously referred the species dubius to the genus Phillipsia from evidence derived from trilobites they believed to be conspecific in the Star Beds of the Great Star River, Queensland, and another unspecified horizon in the Rockhampton area. Mitchell (1918) restricted the name dubius to the Etheridge (1872) type specimen which he was unable to locate and redescribed the Jack and Etheridge Jr. (1892) material as P. stanvellensis Mitchell and P. rockhamptonensis Mitchell. Ele also trans- ferred Etheridge Jr.’s (1892) P. dubia from New South Wales to P. elongata Mitchell. All these species are of Carboniferous age and will not be considered further. Voisey (1939, p. 401; 1950, p. 67) recorded ‘ Phillipsia ’ from the Permian of the Manning-Macleay province, north of Newcastle, New South Wales; they are indeter- minate fragmentary pygidia, AM F38 133-4, and were probably collected from the Cedar Party Limestone. Banks (1962, p. 207) records rare trilobites from Permian strata at Elephant Pass and Ray’s Hill, near St. Mary’s in north-eastern Tasmania. The specimens described herein come from the following localities shown in text- fig. 1. They are: 1. In a quarry, 1 mile west-north-west of Mulbring, 16 miles west of Newcastle, New South Wales, at 475336 Cessnock 1:63,360 military map: Fenestella Shale, Branxton Formation. [Palaeontology, Vol. 14, Part 2, 1971, pp. 222-41, pis. 36-37.1 WASS AND BANKS: PERMIAN TRILOBITES FROM EASTERN AUSTRALIA 223 2. In the creek bed, Sawpit Gully, 1-9 miles east of ‘Boorook’, New South Wales, at 374426 Drake 1 : 63,360 military map: Cataract River Formation. 3. Above (2) and separated from it by a thin pyroclastic flow. 4. At Elephant Pass, 60468689 State Grid, on the Tasman Highway, Tasmania: upper Gray Formation or basal Berriedale Limestone-Enstone Park Limestone correlate (McNeil, 1965). 5. At Ray’s Hill, near St. Mary’s, 60068807 State Grid, Tasmania: basal beds of the Enstone Park Limestone. Trilobites from Elephant Pass and Ray’s Hill were not found in situ. Stratigraphic horizons for these localities have been deduced using palaeontological and petrological similarities. Stratigraphic units discussed are shown in Table 1. Further information is available in Banks (1962) and Runnegar (1967, 1969). ASSOCIATED FAUNAS The fauna associated with Doublatia inflata gen. et sp. nov. near Mulbring includes Anidanthus solitus (Waterhouse), Ingelarella branxtonensis (Etheridge), Strophalosia cf. clarkei (Etheridge), Fletcherithyris parkesi Campbell, brachiopod cf. Notospirifer, Deltopecten squamuliferus (Morris), Pleurikodonta sp., Atomodesma ( Aphanaia ) sp., Myonia cf. cornigata Fletcher, Stutchburia costata (Morris), Stenopora crinita ? Lonsdale, Protoretepora ampla (Lonsdale), Fenestella bituberculata Crockford, and blastoid fragments, indicative of the Ulladulla fauna (Runnegar 1969). The Fenestella Shale stratigraphically above strata containing Neocrimitesmeridionalis (Teichert and Fletcher) is considered to be middle to upper Artinskian in age, agreeing with Runnegar’s inter- pretation. Associated with the Sawpit Gully specimens is a definite Fauna IV assemblage listed by Runnegar (1970). Its probable age is early Upper Permian although there is little published information on this assessment. The Elephant Pass trilobite occurs in a fine-grained dark yellowish-orange (10YR 6/6) dense siltstone (UT 55297) which also contains Euryphyllum sp., Stenopora spp., Streblascopora marmionensis (Bretnall), fenestellids, Strophalosia sp. nov., S. preovalis Maxwell, Anidanthus springsurensis (Booker), Cancrinella farleyensis (Etheridge and Dun), Taeniotliaerus subquadratus (Morris), Terrakea sp., Spirigerella sp., ‘ SpirifeF tasmaniensis (Morris), Grantonia hobartensis Brown, Ingelarella sp., Notospirifer darwini (Morris), Spiriferellina australis Maxwell, Fletcherithyris farleyensis Campbell, F. reidi Campbell, Aviculopecten tenuicollis (Dana), A. fittoni (Morris), and Streblo- cliondria sp. nov. Taeniotliaerus subquadratus occurs in a thin zone about the middle of the Berriedale Limestone; Cancrinella farleyensis occurs above T. subquadratus in the Berriedale Limestone or Grange Mudstone at Mt. Nassau. Thus correlation with the Berriedale Limestone is established. Index species and other characteristic fossils enable the fauna to be identified as Fauna II (Runnegar 1969), thus suggesting correla- tion with the Farley or Greta Formations or possibly the lowest part of the Branxton Formation, New South Wales, an interval considered by Runnegar (1969, p. 88) to span the Sakmarian-Artinskian boundary. text-fig. 1. Map of eastern Australia showing localities of trilobites discussed. WASS AND BANKS: PERMIAN TRILOBITES FROM EASTERN AUSTRALIA 225 The Ray’s Hill trilobite fragments occur in blocks of greyish-orange (10YR 7/4) or pale greyish-orange (10YR 8/3) friable and decalcified silty limestone. The fauna in the same block as the holotype of Doublatia pyriforme gen. et sp. nov. includes Calcitornella stephensi Howchin, Frondicularia aulax Crespin, Stenopora spp., Streblas- copora marmionensis, fenestellids, Schuchertella sp., Spirigerella sp. nov., Licharewia sp., Pterospirifer sp., ‘ Spirifef tasmaniensis, Grantonia bobartensis, Ingelarella cf. angulata table 1. Stratigraphic table for portion of the eastern Australian Permian succession; based primarily on information in Runnegar (1969) and McNeil (1965). Hunter Valley Northern Eastern Australia Hobart Mt. Elephant Russian New South Wales New South Wales Permian Faunas Tasmania Tasmania Stages Tomago Cataract River Mulbring Muree Gilgurry IV Branxton III; U Greta Drake Farley Rutherford Girard II Cygnet Kazanian Ferntree Ferntree Malbina Risdon-Malbina Kungurian correlate — Grange Berriedale Berriedale- Enstone Park correlate Artinskian Nassau Gray Mersey Mt. Elephant Sakmarian Campbell, I. ? ingelarensis Campbell, Notospirifer darwini, Spiriferellma australis, Fletcherithyris reidi, Pentvispira cf. elegans (Fletcher), Pseudomyalina sp., ? Atomodesma sp., Streblochondria sp. nov., and ? Astartila sp., as well as numerous worm castings, ostracodes, and crinoid columnals. Other specimens containing fragments assigned to D. pyriforme include, in addition, Euryphyllum sp., Protoretepora ampla and Aviculo- pecten tenuicollis. The fauna in the block containing Doublatia sp. includes Stenopora sp., Polypora sp., Fenestella sp., Strophalosia sp. nov., Terrakea sp., Spiriferellina sp., Peruvispira sp., and a myalinid. The associated fauna at Ray’s Hill also has charac- teristic Fauna II species, suggesting approximate correlation with the Elephant Pass horizon. Therefore, the occurrences of trilobites in the Permian of Tasmania is likely to be a little older than the beds containing D. inflat a, the Fenestella Shale, in New South Wales. Acknowledgements. It is a pleasure to acknowledge the continual guidance of Dr. K. S. W. Campbell, Australian National University, Canberra. Dr. R. E. Grant, United States National Museum, Washing- ton, compared the holotype of Doublatia inflata with specimens available in the U.S.A. and perused literature unavailable in Australia. For assistance in obtaining information on specimens, their local- ities and associated faunas, we thank Drs. J. S. Jell and J. D. Armstrong, Mr. F. S. Colliver and Mr. P. Telford of the University of Queensland, and the Director of the Australian Museum, Sydney. We wish to thank Mrs. M. R. Banks for assistance with typing and technical aspects and Mr. G. Z. Foldvary for photography. 226 PALAEONTOLOGY, VOLUME 14 One of us (R. E. W.) acknowledges facilities made available by the British Museum (Natural History) during a visit to London. Financial support received from an Eleanor Sophia Wood Travelling Fellow- ship and University of Sydney Research Grants is gratefully acknowledged. Specimens from the University of Queensland were collected by Banks, Dr. B. N. Runnegar, and P. Telford. Tasmanian specimens were collected by Banks, together with W. D. Palfreyman, J. B. Jago, and R. F. McShane. Abbreviations used throughout the text are: AM — Australian Museum Collection, Sydney; SUP — Sydney University Palaeontological Collection, Department of Geology and Geophysics, University of Sydney; UQ — Department of Geology Collection, University of Queensland, Brisbane; UT — Department of Geology Collection, University of Tasmania, Hobart. SYSTEMATIC DESCRIPTIONS Class TRILOBITA Order ptychopariida Suborder illaenina Superfamily proetacea Family proetidae The Carboniferous and Permian trilobites have been grouped in different ways by different authors over the last twenty years (compare Hupe 1953, Moore, 1959, Hahn and Hahn, 1967). Hahn and Hahn (1967) and Hessler (1963) suppressed Phillipsiidae as a family name and treated genera formerly placed therein as members of subfamilies of the Proetidae. This treatment will be followed here. Subfamily griffithidinae Hupe 1953 emend. Hahn and Hahn 1967 Characterized by the forward extension of the frontal lobe of the glabella, the up- wardly inflated glabella and the development of a median preoccipital lobe. The new genus, Doublatia, clearly falls within this subfamily as emended by Hahn and Hahn. Hahn and Hahn (1967) recognized three groups within this subfamily and brief diagnoses of each group compiled from their text (mainly pp. 343, 345) and figs. 4 and 5 follow: Griffithid.es group : cephalon more-or-less triangular in outline, glabella highly inflated, furrows 2p and 3p lacking, generally 13 or fewer rings in pygidial axis (except Exochops, 16). Cyphinoides group: cephalon rounded in outline, glabellar furrow 2p always and 3p usually present; generally 11 or fewer rings in pygidial axis. Paladin group: cephalon rounded in outline, glabellar furrows 2p and 3p present; 13 or more rings in pygidial axis. The placing of Doublatia within one of these groups is difficult and will be dealt with later. Morphology used in the following discussion is used in the sense adopted in Moore (1959), except for points on the facial suture, for which see Hupe (1953, p. 48). In the descriptions, long or length refer to the measurements parallel to the axial line and wide or width refer to measurements transverse to the axial line. WASS AND BANKS: PERMIAN TRILOBITES FROM EASTERN AUSTRALIA 227 Genus doublatia gen. nov. Type species. Doublatia inflata gen. et sp. nov. Diagnosis. Cephalon semicircular to parabolic in outline with narrow border; glabella strongly inflated anteriorly; glabellar furrows 2p and 3p weakly developed, lateral preoccipital lobes and occipital ring strongly developed, median preoccipital lobe developed; palpebral region opposite posterior half of the glabella; well-developed marginal crest on free cheeks; genal spines short; thorax of ? nine or ? ten seg- ments; pygidium with axis extending only two-thirds of the pygidial length and with small number, eight or nine, axial rings, a postaxial ridge, and fewer pleurae than axial rings; no pygidial border; wide pygidial doublure; surface finely granulose. Discussion. It is a combination of morphological features that enables this species to be placed in a new generic category. These are : the narrow border on the cephalon which is extended posteriorly to form a short, flat genal spine, the swollen glabella, the absence of a border on the pygidium, the pygidial pleurae which are clearly visible on the posterior region of the pygidium, and the wide pygidial doublure. Doublatia inflata gen. et sp. nov. Plate 36, figs. 1-4 Material. One nearly complete specimen and pygidium. Holotype. SUP 12929a, b, from near Mulbring, N.S.W. Diagnosis. Doublatia with semicircular cephalic outline, almost circular main glabella lobe and nine axial rings and eight pleurae in the pygidium. Description. Greatest dimensions 26-2 mm long and 20-0 mm wide. Outline of the crani- dium semicircular to semi-elliptical; in plan it is waisted adjacent to the palpebral lobes. The posterior margin is very slightly convex anteriorly. The glabella is slightly waisted and increases in width posteriorly from the anterior margin to the lateral pre- occipital lobes. Posterior to this point it decreases in width. The glabella border furrow is deep with the greatest depth at its mid-width. It is U-shaped antero-laterally and semi- elliptical anteriorly. It possesses a sharp, upturned border which is round and, from what is preserved, increases gradually in height from the anterior portion of the glabella. The anterior border furrow is TO mm (sag.) and T6 mm (exsag.), measured normal to the periphery. The furrow begins to shallow opposite the eye and opposite the posterior glabellar margin it is almost unrecognizable. The median preoccipital glabellar furrow is very shallow and gently convex anteriorly. It joins the lateral preoccipital lobes at their mid-length. The greatest convexity of the median preoccipital lobe is in the central portion. This lobe is depressed below the anterior region of the glabella but elevated above the occipital ring. The occipital furrow which is convex anteriorly does not vary greatly in depth; it appears deeper laterally due to the bulbous nature of the lateral pre- occipital lobes. Shape of the occipital ring is difficult to determine due to preservation but is close to a semi-ellipse with only very slight curvature posteriorly. Lateral preoccipital lobes are very bulbous and are more coarsely ornamented than the rest of the glabella. 228 PALAEONTOLOGY, VOLUME 14 Furrows surrounding the lobes are deepest anteriorly. The frontal glabellar lobe is inflated as shown by the great convexity of the anterior and antero-lateral margins. Its central portion is relatively flat and the convexity adjacent to the lateral preoccipital lobes is not as great as in the anterior and antero-lateral regions. The antero-lateral outline of the librigenae is gently curved. Along the facial suture, a is situated lateral to the forward projection of the axial furrow, in the sub-marginal furrow just inside the marginal crest. The anterior limbs /3-y are sigmoidal and slightly convergent posteriorly. Point y is situated close to the axial furrow in front of the junc- tion of lp with the axial furrow. The palpebral lobe is a semi-ellipse, the long axis of which is directed antero-axially. Point 8 is situated posteriorly on the palpebral lobe, approximately opposite the mid-length of the lateral preoccipital lobe. Point e lies a little outside the axial furrow and approximately opposite the transglabellar, pre- occipital furrow. From e the facial suture runs postero-laterally at about 10° to the axial line for a short distance before turning laterally through about 135°. From this turning point it continues straight to the posterior margin which it meets at an angle of about 20°. The area of greatest convexity on the librigenae is the most antero-lateral region. The genal spine extends to about the second or third thoracic segment and slopes on both sides from a low ridge which bisects the spine. The ridge runs axially parallel to the posterior margin of the cephalon until reaching the facial suture where it changes curvature posterior to the palpebral lobe. There is a marked depression adjacent to the posterior end of the facial suture. Essentially, the librigenae rise gradually towards the periphery and then slope sharply in most regions to the lateral border. Nine or ten thoracic segments are present. The axis expands to the seventh or eighth axial ring where it is approximately one-third the thoracic width ; posteriorly it narrows. The greatest height of the axis is at the sixth or seventh ring, where it is elevated above the pleurae; at the most posterior ring, axis and pleurae are on a similar elevation. The greatest height of the axial rings is along their mid-width. Interaxial furrows are concave anteriorly. The junction between pleurae is normal to the axis until the fulcral lobe is reached approximately one-quarter of the distance along the pleural length. The inter- pleural furrow then curves posteriorly, being gently concave anteriorly. The same applies for most of the pleural furrows. In one or two cases, however, they are gently concave anteriorly and converge towards the interpleural furrows. Lateral extremities of pleurae become more posteriorly directed near the pygidial junction. The greatest height of pleurae is approximately at their mid-width adjacent to the fulcral lobe. The pygidium is semicircular in outline. There is no border. The axis, containing nine rings, extends only two-thirds of its length. The posterior end of the axis is very steep and is extended as a faint postaxial ridge. The axis narrows from 6-0 mm at the thoracic junction to 2-9 mm at the junction of the seventh and eighth axial rings. The height of the axis decreases posteriorly to the junction of the seventh and eighth rings EXPLANATION OF PLATE 36 Figs. 1-4. Doublatia inflata gen. et sp. nov. 1, holotype, SUP 12929a, x3. 2, SUP 12929b, X3. 3, SUP 12929a, before removal of part of pygidium, X 5. 4, SUP 12929a, after removal of part of pygidium to reveal free cheek and facial suture, x 5. Fig. 5. Pygidium indet., Type A. UQ F44458, X 4. Fig. 6. Pygidium indet., Type B. UQ F44457, X4. Palaeontology, Vol. 14 PLATE 36 WASS and BANKS, Doublatia gen. nov, WASS AND BANKS: PERMIAN TRILOBITES FROM EASTERN AUSTRALIA 229 and then increases slightly to the ninth ring. The greatest convexity is at the mid-point of all axial rings. The posterior side of the interaxial furrow is very steep and the anterior side slopes sharply to the ring. Adjacent and parallel to the axial furrow on rings one to six, and possibly seven, is a furrow which results in the formation of a small tubercle at the ends of these rings. There are seven well-defined pleurae with an eighth poorly defined. The pleural length decreases posteriorly. The greatest height of pleurae is anteriorly. Interpleural furrows between anterior pleurae curve most in a posterior direction and the sixth pleura approximately parallels the axis. Interpleural furrows are deeper than pleural furrows; the pleural furrow separates two regions of convexity in the pleurae with the posterior part always having the greater convexity. All furrows are well defined except for some in the posterior region. The doublure is wide, extending at least as far as the posterior culmination of the axis. It is ornamented by many fine ‘semiconcentric’ grooves. Doublatia pyriforme gen. et sp. nov. Plate 37, figs. 1-12, 14, 15; text-fig. 2 Material. The material on which this description is based consists of two cranidia, five free cheeks, other cephalic fragments, thoracic fragments, four complete pygidia, and two partial pygidia. One pygidium includes both the internal and external moulds and two other pygidia and one of the free cheeks are partly decorticated to reveal part of the doublure. Only UT 55297 is from Elephant Pass; all other specimens are from Ray’s Hill, Tasmania. Holotype. UT 90142, a cranidium from Ray’s Hill. Paratypes. UT 90113, 90144, 90155, free cheeks; UT 90094u, b, 90115, 90121, pygidia; all from Ray’s Hill. Diagnosis. Doublatia with pyriform main glabellar lobe, short genal spine, eight axial rings and seven pleurae in the pygidium. Description. The holotype cranidium (a partly decalcified original skeleton, PI. 37, figs. 1, 2, 4) is 6-5 mm long and 5-0 mm wide from and about 7-0 mm from (subscript refers to the side of the animal, left or right, on which point occurs). The anterior border (c^-ar) is arcuate in plan and subtends an angle of about 95° at the centre of curvature (approximately the centre point of the glabella). The facial suture rises steeply and obliquely abaxially to /3 on the crest of the marginal ridge whence it passes as a straight line to y at the waist of the cranidium just over half the distance from anterior to posterior of the cranidium. The line /3-y makes an angle of about 30° with the axial line. The distance from y, to yr is about 3-4 mm. The facial suture at y has a small radius of curvature. From y to e the suture describes a semi-elliptical path with a major diameter of about 1-5 mm. Point 8 is situated about 4-0 mm behind the anterior margin and about 2-8 mm from the axis. Points y and e are both close to the axial furrow and approximately equidistant from the axial line. From e the suture passes backwards for a short distance and then posteriorly and laterally to co. The line er-o)r is about 45 ° to the axis. The line a^-cur is about 5-8 mm from the anterior margin. The posterior margin of the cranidium is crossbow shaped in plan with the convexity to the posterior. The anterior border, horizontal in front view (PI. 37, fig. 2), is turned up sharply to form a rounded ridge about 0-3 mm across. Behind this is a deep, narrow, rather angular, 230 PALAEONTOLOGY, VOLUME 14 preglabellar border furrow which expands laterally to form the anterior part of the fixigenae. The glabella is also waisted, the narrowest portion being at the intersection of the preoccipital (lp) and the axial furrows and a little posterior of y. At its narrowest point the glabella is about 3-0 mm wide. From this waist the glabella widens in a gentle curve around the preoccipital lobes. The glabella is about 4-6 mm long. The main (frontal) lobe of the glabella is pyriform, the posterior margins being defined by deep text-fig. 2. Reconstructions of Doublatia pyriforme sp. nov., X 5. A, dorsal view of cephalon with partially decorticated free cheek to show connective suture and part of the doublure, b, dorsal view of pygidium with decorticated left pleural area showing doublure, c, hypothetical reconstruction of front view of cephalon showing inflated glabella, high palpebral lobes, and inferred position of free cheeks; doublure shown as dotted line, d, cephalon viewed from the right side, e, section of several pygidial pleurae as seen from the right-hand side. IPF = interpleural furrows. PF = pleural furrows. preoccipital furrows (lp) which converge posteriorly from the waist of the glabella towards the axis and make an angle of about 50° with the axis. Slight shearing (top and front to the left) has made accurate measurement of the convexity of the glabella diffi- cult. The highest point is situated half-way along the glabella and the glabella is distinctly EXPLANATION OF PLATE 37 All numbers refer to the UT Collection; all specimens except 55297 a, b, come from Ray’s Hill. Figs. 1-12. Doublatia pyriforme sp. nov. 1, Holotype cranidium from the right side, 90142, x5. 2, Holotype cranidium from the front, X 5. 3, Left free cheek, 90113, X 5. 4, Dorsal view of internal mould of holotype cranidium, X 5. 5, Partly decorticated left free cheek (reverse printed), 90155, X5. 6, 7, Internal mould and rubber cast of external mould of pygidium, 55297a, b, x5. 8, Left free cheek, internal mould, 90144, x5. 9, Rubber cast of external mould of pygidium, 90094a, X 5. 10, Partly decorticated pygidium, 900946, X 5. 11, Partly decorticated pygidium viewed from left hand side to show profile, 900946, X 5. 12, Dorsal view of large cranidium, 90153, X 5. Fig. 13. Doublatia sp., dorsal view of external mould of cranidium, 90143, XlO. Figs. 14-15. Doublatia pyriforme sp. nov. 14, Large left freecheek, 90161, X 3. 15, Partly decorticated left free cheek (reverse printed) showing connective suture, terrace lines and genal spine, 90155, x 8. Palaeontology, Vol. 14 PLATE 37 WASS and BANKS, Australian Permian trilobites WASS AND BANKS: PERMIAN TRILOBITES FROM EASTERN AUSTRALIA 231 but rather uniformly convex upwards (text-fig. 2 d; PI. 37, fig. 1). The frontal lobe is either unsegmented or may show two short, faint, lateral furrows directed posteriorly and axially and rising close to the waist. Shearing and preservation preclude a definite statement on this point. The frontal lobe is terminated posteriorly by a shallow trans- glabellar preoccipital furrow joining the most axial points on lp, and approximately in the line ej-er. The preoccipital segment is broken by two shallow grooves, posterior branches of Ip parallel to the axis, into a more-or-less rectangular median preoccipital lobe (about 0-05 mm long and 0T5 mm wide) and two lateral preoccipital lobes which are almost trapezoidal. Before shearing and the accidents of preservation, collection, and preparation these were probably quite bulbous (PI. 37, fig. 13). The occipital furrow is straight from the lateral edge of the cranidium to the axial furrow where it curves gently posteriorly to outline the lateral preoccipital lobes and then continues in a straight line across the axis. The occipital furrow is deep and is asymmetrical in sagittal section, (PI. 37, fig. 1, text-fig. 2d), the anterior slope being very steep, the posterior gently curved and rising on to the almost flat occipital ring. The partially decorticated free cheek (UT 90155) shows that before reaching the axis the facial suture passes onto the ventral surface at a position corresponding approximately to the forward projection of the axial furrow (PI. 37, figs. 5, 15). At the anterior margin the suture turns axially at about 90 ° to the margin and runs for a short distance before turning abaxially at about 100 ° to become a connective suture and join the inner edge of the doublure. Five free cheeks occur in the same type of matrix as the cranidium, are of similar size and show a facial suture which matches that of the cranidium. The closest match in size occurs in specimen UT 90144 which is 3-6 mm long and 4-2 mm wide (these and other measurements are tabulated as Table 2). The outer margin is evenly curved and the axial and posterior margins almost perpendicular to each other so that the free cheeks approximate one quadrant of an ellipse. The free cheek has considerable relief. The posterior margin is straight or at most very gently curved. The lateral border is marked by a high, sharply rounded crest (up to 0-6 mm wide) which persists almost to the point of the genal spine but declines sharply near the spine. A rounded ridge rises rapidly from near the genal spine and runs just inside the occipital border, reaching a culmination about half-way from the spine to the facial suture, before descending towards the dorsal furrow. A broad shallow furrow lies inside the marginal ridge both laterally and posteriorly and the occipital part of this deepens to a pit just outside the facial suture. The palpebral lobe rises steeply from the sub-marginal and occipital furrows. The genal spine is a short, rather blunt posterolateral prolongation of the genal angle. Partial decortication of one free cheek (UT 90155) revealed the doublure marked by terrace lines (PI. 37, fig. 15) and showed that the inner edge of the doublure lay under the axis of the broad, shallow sub-marginal furrow, at least anteriorly. The cross-section of the free cheek shows a narrow, high, rounded marginal ridge, a broad shallow furrow, and the steeply rising slopes of the palpebral lobes (text-fig. 2c, d). Combining the shapes of the cranidium and free cheeks suggests that the cephalon was arched transversely, the free cheeks probably lying at a considerable angle to the horizontal during life (text-fig. 2c). It was probably approximately parabolic in plan with the genal angles projecting downwards and backwards as short, blunt spines (text-fig. 2d). A distinctive feature is the high ridge or crest which borders the cephalon except at the genal angles and along the axial part of the occipital ring. 232 PALAEONTOLOGY, VOLUME 14 Isolated fragments of cephala and thorax show clearly the finely granulose surface of the trilobite. The isolated thoracic segments suggest that the axis was wide and the pleural regions rather narrow. Fragments of the pleurae (e.g. UT 90159) suggest a width (6-5 mm) about double the length (3-2 mm) and the shape in outline of a parallel- ogram. The pleural furrow is directed towards the postero-lateral corner in most specimens but is almost parallel to the posterior margin in others. In crushed external moulds it is represented by a high, sharply crested, oblique ridge. Several pygidia occur in the same type of matrix as the holotype cranidium. They have axes of approximately the same width as that of the cranidium and have the same type of ornament. On the basis of mutual and exclusive association, axis width, and ornament the pygidia (Table 2b, less UT 55297) are considered as belonging to the same species as the cranidium. The anterior and posterior margin of the pygidia are both arcuate in plan, the radius of curvature of the anterior (8-2 mm in UT 90094a) being greater than that of the posterior (6-5 mm in UT 90094a). The anterior margin is smooth across the axis. From the axial furrows the front margin of the pleural articulating half-segments runs forward to a point situated about a quarter of the distance from the axial furrow to the lateral margin. From this point the border of the half-ring continues in a gentle curve to the antero-lateral point of the articulating facet whence it runs almost parallel to the axis and posterolaterally to the widest point of the pygidium. The pygidia are about 0-5 to 0-6 times as long as they are wide (Table 2b). The axis is widest anteriorly and its maximum width varies from about 0-32 to 0-43 of the maximum width of the pygidium. The axis tapers very gently backwards (axial furrows at 12-16° approximately to the axial line) to about the seventh ring posterior to which it narrows rapidly and slopes down to a low postaxial ridge. The axis is 0-66 to 0-77 of the length of the pygidium. In sagittal section the top of the axis is horizontal (PI. 37, fig. 11) or slopes gently down and back from the anterior ring. In transverse section the axial rings, except the terminal one, are not uniformly curved but tend to rise steeply from the axial furrows, flatten out, or even fall a little before arching evenly over the axial line. In effect there are two furrows within the axis, parallel and close to the axial furrows and these produce a faint tubercle at the pleural ends of each axial ring. The axis contains eight rings in addition to the anterior articulating half-ring. The rings appear to be or to have been (prior to slight deformation) uniformly curved in sagittal section and to be separated by sharp furrows. The pleural regions are very nearly uniformly convex upwards (Type A of Weller 1937, p. 342) and the axis rises only a little above the projection of the curve of the pleural regions. There is no border. Segmentation of the pleural region does not match that of the axis. There are only seven pleurae on each side in addition to the postaxial ridge. The pleurae decrease successively and gradually in height from anterior to pos- terior. They consist of two sections of different heights and convexities separated from one another by pleural furrows. The anterior part is low and very gently convex up- wards, whereas the posterior is high and more convex (text-fig. 2c). The interpleural furrows are rather more distinct than the pleural, due to slightly greater depth but both sets of furrows become shallower and therefore more indistinct posteriorly. The interpleural furrows meet the axial furrows at approximately the same point as do the inter-ring furrows on the axis and the pleural furrows meet the axial furrow at points WASS AND BANKS: PERMIAN TRILOBITES FROM EASTERN AUSTRALIA 233 approximately half-way along each axial ring. The interpleural furrows are gently convex antero-laterally, the convexity decreasing from anterior to posterior within the pleural field and the anterior angle between the axial line and the interpleural furrows increasing from just over 90° for the most anterior segment to just over 1 80 for the seventh. The interpleural and pleural furrows are almost parallel (or concentric). Several specimens show that the surface was finely granulose. table 2. Cephalic and pygidial measurements of Doublatia inflata sp. nov., D. pyriforme sp. nov., and D. sp. A. CEPHALIC MEASUREMENTS (i) Glabella, in front of transglabellar, preoccipital furrow L W L/W D. inflata (SUP 12929a) 6-5 7-5 0-87 D. pyriforme (UT 90142) 4-1 3-2 1-28 D. pyriforme (UT 90153) > 9-3 5-0 > 1-86 Doublatia sp. (UT 90143) > 5-4 5 0 > 1-08 (ii) Free cheeks L W L/W D. inflata (SUP 12929a) 11-0 7-7 1-43 D. pyriforme (UT 90161) 7-8 6-2 1-25 D. pyriforme (UT 90113, 90144, 90155, 90284) Range > 3-2-5-0 3-0-4-4 >107-1-25 L measured exsagitally, W transversely B. PYGIDIUM Lp Wp La Wa LpjWp La/Wa D. inflata (SUP 12929a) 9 0 19-4 6 0 6-5 0 46 0-92 D. pyriforme (UT 90094a, b, 90121, 90230-1, 55297) Range 3-1-7 0 5-6-12 4 == 24-4-6 2-3-4 0 0-52-0-65 ^ 1-0-12 Lp/La Wp I Wa 1 50 3-0 — 1-3-1-5 2-3-3 1 All measurements in millimetres. L = length, W = width, Lp = length of pygidium, La = length of axis, Wp = width of pygidium, Wa = width of axis. The internal moulds show that the doublure was wide. Anteriorly it extended from the outer margin about halfway to the axial furrow and it maintained this width throughout so that in the plane of symmetry it extended forward to the posterior end of the axis. It is prominently marked by numerous fine concentric grooves (terrace lines). The dimensions and relative proportions of the pygidium of D. pyriforme are shown in Table 2b which includes those of D. inflata for comparison. Other material. Other material probably of the same species includes a rather larger partial cranidium (UT 90153) from the same type of matrix at Ray’s Hill, a larger free cheek (UT 90161) and the pygidium (UT 55297) from Elephant Pass. The cranidium is an internal mould of the part of the dorsal surface of the glabella and fixed cheeks. It has been sheared, the length of the preserved part being 9-3 mm, the width 5-0 mm. The anterior border comes to an obtuse point just to the right of the axis but this may be due to shearing. The border is marked by a high, rounded ridge only 2-0 mm across. R C 7998 234 PALAEONTOLOGY, VOLUME 14 The preglabellar furrow is similar to that in the holotype and expands in the same way to a fixed cheek, the preserved portions of which have the same shape as the holotype. The frontal lobe of the glabella is pyriform and strongly convex upwards, the highest point being about 6 mm behind the anterior border and almost 2 mm above the general level of the base of the glabella. The anterior part of the glabella has been partly crushed. Although this partial cranidium is approximately twice the size of the holotype, the frontal lobe of the glabella is pyriform and on this basis it is included in D. pyriforme. The proportions of the frontal lobe are even further from those of D. inflata than they are from D. pyriforme. Another large specimen is the free cheek (UT 90161) preserved as an internal mould. The specimen has a length to width ratio very close to that of other specimens assigned to D. pyriforme and very different from that of D. inflata. There is a narrow (04 mm) ridge around the lateral margin which is lower (only 0-5 mm high) than in smaller specimens but similarly decreases in height near the genal angle. The occipital ring is similar to that in the smaller specimens, in that it rises to a culmination about half-way between the genal angle and the posterior limit of the facial suture. The occipital furrow shallows towards the genal angle. A broad shallow furrow lies inside the marginal ridge and the cheek rises steeply from this to the palpebral lobe. The top of the palpebral lobe is about 1-8 mm above the plane of the lateral margin of the free cheek. The facial suture has a similar shape in plan to those of the smaller specimens. Although the pygidium from Elephant Pass (UT 55297, PI. 37, figs. 6, 7) comes from a different place and lithology, it shows the same characters as the pygidia from Ray’s Hill and is placed in the same species. Discussion. The Tasmanian species is generally only about half the size of that from Mulbring. The cephalic outline which has to be reconstructed in both species described here, is semicircular in D. inflata and in D. pyriforme is a parabola approximating to the curve y = x2/4-5, where y, x are Cartesian co-ordinates in millimetres of a point on the outline relative to the front of the cephalon as origin and the long axis of the cephalon as the y axis. The cranidium of D. pyriforme is proportionally longer (L:W = T5) than that from Mulbring (L:W = 1T4). Both have a glabella waisted just in front of the preoccipital lobes but in D. inflata the frontal lobe is almost circular as against pyriform in D. pyriforme, the depth of the waist indentation is less in D. inflata, and the lateral preoccipital lobes are more circular in D. inflata than in D. pyriforme. The occipital region is similar in both. The preglabellar furrow is narrower and the border more upturned and higher than in D. inflata. In addition the border ridge is higher and the submarginal lateral furrow wider and deeper than in D. inflata. Shape of the facial suture is very similar but fl-y is straight in D. pyriforme, sigmoidal in D. inflata. The ornament is similar in both. Thoracic segments are similar in shape as far as can be judged. The pygidium of D. pyriforme is about the same shape (but half the size) as that of D. inflata and the relative proportions of length and width of axis and pygidium show approximately the same range (Table 2b). D. pyriforme does, however, differ from D. inflata in that it has eight axial and seven pleural segments as against nine and eight respectively in D. inflata. The difference in segmentation may be specific or related to a stage in holaspid development. In this latter case all the Tasmanian pygidia would represent the one holaspid stage, being earlier than that represented by the Mulbring WASS AND BANKS: PERMIAN TRILOBITES FROM EASTERN AUSTRALIA 235 specimens (cf. Weller 1937). While this is possible, it is rather unlikely that the only specimens collected belong to the same, and not final, holaspid stage. It is more likely that this difference is specific. The angle made by the axial furrows with the axial line is a little higher (18°) in D. inflata than in D. pyriforme (12-16°). Doublatia sp. Plate 37, fig. 13 A third cranidium (UT 90143) was found as an almost complete external mould in white silicified limestone at Ray’s Hill. The preglabellar region and the fixed cheek on one side are missing. Description. The glabella is 3-7 mm long and a little over 4 mm wide, and it is waisted as in D. pyriforme. The frontal lobe, although incomplete anteriorly, appears to be almost circular and is highly inflated, the highest point lying on the axis about 2-0 mm in front of the preoccipital furrow and at least 0-9 mm above the base of the glabella. The left-hand side of the frontal lobe shows two faint but distinct furrows arising at equal intervals of about 0-3 mm in front of the preoccipital furrow and extending inwards and backwards to about two-thirds of the way to the axis. The more posterior of these parallels the preoccipital furrow, the more anterior being more directly trans- verse. The preoccipital furrows run towards the axis making an angle of about 60° with it before turning back almost parallel to the axis to meet the occipital furrow. A shallow indistinct furrow joins these furrows to delineate a third, almost rectangular, median preoccipital lobe. The lateral preoccipital lobes are trigonal to trapezoidal. The occipital furrow is deep and more-or-less symmetrical in sagittal section. The occipital furrow is laterally straight but inside the dorsal furrow curves sigmoidally forward from each side. The occipital ring is very convex in both sagittal and transverse section, producing an almost bulbous appearance. The posterior margin is disrupted but appears to have been gently convex backwards. The high, arcuate palpebral lobe is preserved on the left hand side. The facial suture appears to be slightly divergent anteriorly (y-/3) and curves smoothly at the front towards the axial line (/ 3 towards a). Behind the palpebral lobe it diverges at about 60° to the axial line to just in front of the occipital ring; at this point it flattens to 45° to the axial line at which angle it meets the occipital ring which it crosses at about 75° to the axis. The pleural part of the occipital ring is still rising where it is cut by the facial suture. The whole surface of the cranidium is both coarsely and finely granulose. Discussion. This cranidium is considered to belong to Doublatia on the basis of similar waisting of the glabella, glabellar segmentation, and ornamentation. The frontal lobe of the glabella is almost circular, more similar to D. inflata than to D. pyriforme (Table 2a ( i)), but the lateral preoccipital lobes are closer in shape to those of D. pyriforme than those of D. inflata. The frontal limb of the facial suture (y-/3) is sigmoidally curved as in D. inflata. The occipital region differs only a little from D. pyriforme in sagittal section. It is likely that this specimen represents a new species or perhaps is D. inflata but it is not complete enough to allow proper decision. 236 PALAEONTOLOGY, VOLUME 14 Generic affinities of Doublatia Relationships within the Griffithidinae have recently been considered by Hahn and Hahn (1967) who used cephalic outline, degree of glabella inflation, presence of furrows 2p and 3p in the glabella, and the degree of segmentation of the axis of the pygidium as the main criteria linking genera into groups as outlined earlier. Some doubts must be expressed about the validity of these features in showing phylogenetic relationship. Cephalic outline varies considerably within a genus. In Ditomopyge decurtata (Gheyselinck) and D.fatmii Grant (both illustrated by Grant 1966, pi. 13) the outline is parabolic but the equations of the parabolae in the two species are different. D. scitula (Meek and Worthen) (Weller in Moore 1959, p. 0403, fig. 307, 5a) had an almost semicircular cephalic outline whereas D. meridionals Teichert had an outline which was probably trigonal. The type species of Doublatia had an outline which was probably almost semicircular but the other species assigned here to the genus had an outline which was parabolic. It might be expected that similarity in cephalic outline would have been selected in separate lineages as an adaptation to similar habitats. Both Cypliinoides and Eocyphiniwn (Reed 1942, pis. 8, 9) have glabellar inflation at least as great as some of the Griffithides group, for example, Permoproetus, although probably not as great as Neoproetus and Kathwaia. On the whole the degree of glabellar inflation seems to support the grouping adopted by Hahn and Hahn. Glabellar segmentation, reflecting some locomotory or alimentary structures of the soft anatomy might be expected to be more conservative than cephalic outline, at least, and therefore be a better criterion for establishing relationships. Hahn and Hahn (1967) considered that the median preoccipital lobe developed independently, presum- ably as parallel evolutionary regressions to some early Ordovician or Cambrian precursor of the Proetidae, in at least three lineages, Kaskia-Ditomopyge, Thigriffides to the Cypliinoides group, and Bollandia-Permoproetus. They further postulated redevelopment of glabellar furrows in front of lp in the Paladin-Kaskia-Ditomopyge-Anisopyge lineage, in the Thigriffides-Cyphinoides group lineage and in the Bollandia-Paraphillipsia lineage. Suppression of Ip and 2p glabellar furrows in Griffitliidella doris (Hall) leading through Bollandia to Neoproetus and Kathwaia might suggest, on the other hand, that such suppression could also affect the other groups. However, the over-all trend was towards increasing segmentation leading to the formation of a median preoccipital lobe and as many as three other pairs of glabellar furrows as in Anisopyge. In neither the Griffithides nor the Paladin group did rectilinear evolution of this feature occur, judging from the text and figures of Hahn and Hahn. In the Griffithides group Permo- proetus developed a median preoccipital lobe from ancestors without one and in the Paladin group Kaskia, lacking 3p, intervened between forms with this pair of furrows. The lineage suggested by Hessler (1965, pp. 258-9) in the Cummingellinae, i.e. Mosclio- glossis-Cummingella-Richterella-Ameura, demonstrates gradually increasing suppres- sion of glabellar furrows from anterior to posterior. It would be superficially simpler to group all genera with lp forked or with a median preoccipital lobe and postulate derivation by increase in strength, length, and number of glabellar furrows from a genus in the Lower Devonian with unforked lp and some furrows in front of lp. Such a derivation might proceed through a species like Schizoproetus celechovicensis (Smycka) or Cyrtosymbole escoti (Koenen) to Eocyphinium and Cypliinoides or a similar genus WASS AND BANKS: PERMIAN TRILOBITES FROM EASTERN AUSTRALIA 237 and on to genera with a median preoccipital lobe and one or more furrows in front of lp. Hupe (1953) made almost such a grouping in erecting the Ditomopyginae. However, this rectilinear increase in glabellar furrowing is not without exception, and reversal of trend would have to be postulated to accommodate Permoproetus and Paraphillipsia at least. Another potentially useful taxonomic character is the glabellar outline which helps to characterize the Phillipsinae and Cummingellinae and to connect such genera as Moschoglossis and Ameura (Messier 1965, pp. 258-9). Gradual lateral and forward expansion of the anterior lobe of the glabella and progressive suppression of glabellar furrows from anterior to posterior as shown by this lineage, may, if continued, have led to Paraphillipsia. The authors have attempted to construct a phylogenetic system based on conservation of glabellar shape or on modification of glabellar shape by anterior or later expansion but with no retrogression and taking particular note of the position of the waist or waists. However, this scheme also contains anomalies such as one species of Ditomopyge having only one waist at 2p and related therefore to Cyphinoides and Eocyphinium whereas others may have a second, smaller waist about midway along the length of the lateral preoccipital lobes, suggesting relationship to Kaskia. Another anomaly in such a scheme is the placement of species of Griffithides in two lineages, one with waists at the mid-length of the lateral preoccipital lobe and Ip ( G . longiceps Portlock), the other waists at lp and within the frontal lobe in front of lp ( G . ( Meta - phillipsia ) seminiferus (Phillips)). Yet another trend used in classification is increase in segmentation of the axis of the pygidium. However, no phylogenetic scheme yet published, nor the one mentioned earlier as having been tried by the authors, maintains this as a rectilinear trend in all lineages. It would appear that the Proetidae, or at least the genera grouped by Hahn and Hahn (1967) as Griffithidinae, were subject to mosaic and reversible evolution, leading to difficulty in establishment of clear phylogenetic lines. Such lines may emerge when more intermediate forms are described especially from the Upper Devonian, Upper Carboniferous, and Lower Permian and make possible tracing, through small steps, evolutionary and migratory patterns. It is likely, from what is already known of the derivation of eastern Australian Permian fossils generally (Teichert 1951), that the pre- cursor of Doublatia was a Carboniferous form from eastern Australia or perhaps an earlier Permian form from Western Australia. At the present stage of knowledge and in view of the likelihood of mosaic evolution within the Griffithidinae, all that can usefully be done to establish the generic relation- ship of Doublatia is to compare it feature by feature with other genera and so assess the genus to which it is most similar. Such an assessment may reveal a real phylogenetic relationship or a distantly related genus at about the same stage in a number of evolu- tionary trends. Little is to be gained by comparisons of the cephalic outlines of the Doublatia species. The glabella has a single waist at lp, as have Neoproetus, Kathwaia, Paladin, Bollandia, and some species of Ditomopyge. The waist is about as narrow as in Paladin, Bollandia, and Ditomopyge but not as narrow as in Neoproetus or Kathwaia. Some species of Dito- mopyge have a second waist, as mentioned earlier, but there is no sign of this in Doublatia. The widest part of the glabella in Doublatia is across the preoccipital lobes. 238 PALAEONTOLOGY, VOLUME 14 Bollandia and Paraphillipsia are the only other griffithidines (and Paraphillipsia may be a cummingelline) to show this and it may be considered a primitive feature. Other genera such as Ditomopyge, Exochops, Neoproetus, and Permoproetus approach this condition but of these only Ditomopyge and Neoproetus have similar waisting to Douhla- tia. In both these genera the frontal part of the glabella is as wide as or slightly wider than the posterior. In this feature Doublatia shows more resemblance to some of the earlier members of other superfamilies than to most other griffithidines. Of those genera with similar waisting only Ditomopyge is at all like Doublatia in possessing a median preoccipital lobe and glabellar furrows 2p and 3p. The degree of inflation of the frontal lobe of the glabella of D. pyriforme is comparable with that in some Ditomo- pyge species and Timor aspis whereas that of D. inflata is more comparable with that of Neoproetus indicus Tesch but less than that in Kaskia. The degree of forward expansion of the glabella is most similar to that of some species of Ditomopyge, for example, D. sylveuse Weber, D. fatmii, and some specimens of D. meridionals from the Lower Permian of Western Australia which had a frontal brim (Teichert 1944). Microphillipsia shows about the same degree of forward development of the glabella. There is con- siderable resemblance of the front part of the cephalon of D. pyriforme with the frag- ment figured as ? Conophillipsia by Campbell and Engel (1963, pi. 8, fig. 4) from the Tournaisian of New South Wales. The occipital ring is close in shape to that of Ditomopyge sp. (Teichert, 1944) from the Lower Permian Fossil Cliff Limestone of Western Australia, of Neoproetus indicus and 'Griffith ides' trigonoceps Gheyselinck from Timor. Comparison of the shape of the facial suture of Doublatia with that of other proetids shows that the palpebral lobe is situated comparatively far back on the cranidium (y approximately opposite 2p, e approximately opposite the transglabellar, preoccipital furrow). The position compares most closely with that in Kathwaia, Permoproetus, and Ditomopyge. The frontal limbs (y-ff) are slightly more divergent than in Kathwaia and much more divergent than in Permoproetus and notably straight, both features seen also in Weania goldringi Campbell and Engel 1963. In shape of this limb Doublatia is closest to Kathwaia but shows similarities also to some Lower Carboniferous genera (e.g. Weania and Metaphillipsia ) and lesser similarities to Paladin and Ditomopyge. The posterior limbs (e-a>) are similar in plan to those of Kathwaia with lesser resemblances to those of Ditomopyge, Metaphillipsia, Ameura and a number of other genera. The connective sutures are long and divergent, different in both respects from those of Proetus cuvieri (Struve in Moore 1959, p. 0385, fig. 292) and P. boliemicus (Hupe 1953, p. 51, fig. 5 d) and in their divergence they differ from those of Carbonocoryphe binde- manni (Struve in Moore 1959, p. 0393, fig. 299, 6a). The free cheeks of Doublatia pyriforme show a marked resemblance to those assigned by Campbell and Engel (1963, pi. 6, figs. 10-13) to Weania goldringi especially in the angular nature of the wide divergence and straightness of y-ff and the shape of the genal spine but W. goldringi is closer to D. inflata in flatness. The genal spines in Doublatia are short and most closely resemble those of Neoproetus in both length and in the structure of the border and adjacent furrow in the immediate vicinity of the genal angle. There are lesser resemblances to Eocyphinium, Bollandia, Weania goldringi, Microphillipsia, and Timoraspis breviceps (Gheyselinck) in these respects. In the majority of cranidial characters, then, Doublatia is closest to Ditomopyge and WASS AND BANKS: PERMIAN TRILOBITES FROM EASTERN AUSTRALIA 239 derivation from an early Ditomopyge species, in which the glabella did not reach the anterior margin of the cephalon and was rather narrow anteriorly, might be suggested. From such an ancestor DoubJatia could have evolved by slight weakening of the anterior fork of lp and by shortening of the genal spine. A collateral relationship with Neoproetus and Kathwaia is suggested by the similar waisting of the glabella, similar position of the palpebral lobe, similar genal spine ( Neoproetus only), and somewhat similar ornament. Another genus with fairly close collateral relationship is Microphillipsia, as shown by similarity in glabellar extension, shape, and segmentation, and in the development of the genal spine. Although the cephalon of DoubJatia is essentially that of a Ditomopyge with a short genal spine, the pygidium is very different from that of Ditomopyge. The pygidium of DoubJatia is strikingly reminiscent of some cornuproetines ( PribyJia , Cornuproetus), some cyrtosymbolines ( CyrtosymboJe , Calybole, WariboJe, and Weania) and some tro- pidocoryphines ( Decoroproetus ). With these it agrees in many, but not all, of the following characters — outline, shortness of axis, lack of border, small number of segments, presence of pleural as well as interpleural furrows, presence of postaxial ridge. In almost all the characters listed and in the width of the doublure it is remarkably close to the pygidia assigned by Campbell and Engel (1963, pi. 6, figs. 1-4) to Weania goldringi from the Tournaisian of New South Wales. The outline, transverse profile, segmentation, presence of interpleural furrows and a postaxial ridge are similar to those in Kathwaia but the anterior part of each pleura was much more convex in Kathwaia than in DoubJatia. The pygidium of DoubJatia also shows many similarities to that of Griffithidella doris (Messier 1965, pi. 37, figs. 1, 5, 6). The conservatism of the pygidial structure of DoubJatia is reflected in its very close similarity to Weania from the Tournais- ian and similarity to Devonian genera especially PribyJia. Thus DoubJatia had a cephalon moderately advanced in terms of glabellar expansion and inflation compared to many other proetids but not as advanced as many others. Development of lobation of the glabella was at an intermediate evolutionary stage and several genera had more lobes. The free cheek was advanced in terms of length of the genal spine. The most primitive feature was the pygidium. DoubJatia was at about the same general stage of evolution as some Ditomopyge species but has a more primitive pygidium than any species of Ditomopyge. Thus it may be phylogenetically related to a primitive Ditomopyge from which it developed mainly by shortening of the genal spine or perhaps also by retrogressive shortening of the pygidium associated with reduction in number of pygidial segments and loss of border. Alternatively it may have arisen independently from another stock with cephalic changes parallel to Dito- mopyge. From general considerations of the nature of Upper Carboniferous and Permian faunas in eastern Australia (Campbell 1961; Teichert 1951) it is likely that DoubJatia arose either from Lower Carboniferous Eastern Australian stock, protected by a barrier, probably climatic, from competition in the Upper Carboniferous with stock migrating from outside Australia, or from Lower Permian Western Australian stock which migrated around the continental block of Australia late in the Lower Permian. The similarity of the front end of the cranidium of ? Conophillipsia to that of DoubJatia pyrifonne and the similarity of the free cheeks and pygidia assigned to Weania goldringi to those of DoubJatia support the possibility of a long eastern Australian history for 240 PALAEONTOLOGY, VOLUME 14 Doublatia. On the other hand, derivation from Ditomopyge described by Teichert (1944) from the Fossil Cliff Formation, Western Australia, cannot be rejected as the cranidia are rather similar and the age relationships are those required for such a derivation. Trilobites are generally represented in the Permian of eastern Australia by isolated pygidia. The following descriptions are of two common forms of pygidia found in this region. Pygidium indet., Type A Plate 36, fig. 5 Description. The specimen, UQ F44458, is a pygidium. There are at least seven axial rings and eight pleurae with the latter being parallel to the axis at the posterior extremity. The pygidial axis is very pointed posteriorly and extends for three-quarters of the pygidial length. At the anterior end the axis occupies about one-third of the pygidial width. It increases in height until about the fourth axial segment and then slopes gradually to the posterior extremity. An extremely narrow pygidial border is present resulting in a change of slope along the ends of the pleurae. Locality. The specimen was found in Sawpit Gully (Locality 2). Three other specimens, UQ F58160- 1 from this locality and 58306 from Locality 3 appear to be closely related to the specimen described above. Pygidium indet., Type B Plate 36, fig. 6 Description. The specimen, UQ F44457, is also a pygidium. At least ten axial rings are preserved with small tubercles developed at the junction of the axial rings and pleurae. The axis is about one-third the pygidial width at the anterior end but it gradually decreases in width posteriorly. The posterior extremity of the axis, at three- quarters of the pygidial length, is rounded. Locality. The specimen was found in Sawpit Gully (Locality 2). Another specimen, UQ 58305, is similar to UQ F 44457 and was found at Locality 3. REFERENCES banks, M. R. 1962. Permian System. In The Geology of Tasmania, eds. A. H. Spry and M. R. Banks. /. geol. Soc. Aust., 9, 189-215. Campbell, k. s. w. 1961. Carboniferous Fossils from the Kuttung Rocks of New South Wales. Palaeontology , 4, 428-74. and engel, b. a. 1963. The Faunas of the Tournaisian Tulcumba Sandstone and its members in the Werrie and Belvue Synclines, New South Wales. J. geol. Soc. Aust. 10, 55-122. etheridge, r. 1872. Appendix I to A. Daintree, Notes on the Geology of the colony of Queensland. Q. Jl geol. Soc. Lond. 28, 317-50. etheridge, R. jr. 1892. A Monograph of the Carboniferous and Permo-Carboniferous Invertebrata of New South Wales. Part II. Mem. geol. Surv. N.S. W., Palaeont., 5 (2). grant, r. E. 1966. Late Permian trilobites from the Salt Range, West Pakistan. Palaeontology, 9, 64-73. WASS AND BANKS: PERMIAN TR1LOBITES FROM EASTERN AUSTRALIA 241 hahn, g. and hahn, r. 1967. Zur Phylogenie der Proetidae (Trilobita) des Karbons und Perms. Zool. Beitr. (n.f.) 13, 303-49, 5 Abb. hessler, r. r. 1963. Lower Mississippian Trilobites of the Family Proetidae in the United States. Part I. J. Paleont. 37, 543-63. 1965. Lower Mississippian Trilobites of the Family Proetidae in the United States. Part II. Ibid. 39, 248-64. hupe, p. 1953. Trilobites. Traite de Paleont ologie. Ill, 44-246. Masson et Cie, Paris. jack, r. and etheridge, r. jr. 1892. The Geology and Palaeontology of Queensland and New Guinea . Brisbane. 2 vols. mcneil, r. d. 1965. The Geology of the Mt. Elephant-Piccaninny Point area, Tasmania. Pap. Proc. R. Soc. Tasm. 99, 27-49. mitchell, J. 1918. The Carboniferous Trilobites of Australia. Proc. Linn. Soc. N.S.W. 43, 437-94. moore, r. c. (ed.). 1959. Treatise on Invertebrate Paleontology. Part 0. Geol. Soc. Am. and Univ. Kansas Press, Lawrence. reed, f. r. c. 1942. Some new Carboniferous Trilobites. Ann. Mag. nat. Hist. (11), 9, 649-72. runnegar, b. n. 1967. Desmodont Bivalves from the Permian of eastern Australia. Bull. Bur. Min. Re sour. A list. 96. 1969. The Permian faunal succession in eastern Australia in Proceedings of Specialists’ Meetings held at Canberra, 25-31 May 1968 (ed. D. A. Brown). Spec. Publ. geol. Soc. Aust. 2, 73-98. 1970. Permian faunas from northern New South Wales and the connection between the Sydney and Bowen Basins. J. geol. Soc. Aust. 16, 697-710. teichert, c. 1944. Permian trilobites from Western Australia. J. Paleont. 18, 455-63. 1951. The marine Permian faunas of Western Australia. Paleont. Z. 24, 76-90. voisey, a. h. 1939. The geology of the Lower Manning District of New South Wales. Proc. Linn. Soc. N.S. W. 64, 394-407. 1950. The Permian Rocks of the Manning-Macleay Province, New South Wales. J. Proc. R. Soc. N.S. W. 84, 64-7. weller, j. m. 1937. Evolutionary tendencies in American Carboniferous Trilobites. J. Paleont. 11, 337-46. ROBIN E. WASS Department of Geology and Geophysics University of Sydney, 2006 New South Wales Australia MAXWELL R. BANKS Department of Geology University of Tasmania Box 252c, G.P.O. Hobart, 7001 Typescript received 1 May 1970 Australia FUNCTIONAL MORPHOLOGY OF SOME FOSSIL PALAEOTAXODONT BIVALVE HINGES AS A GUIDE TO ORIENTATION by j. d. bradshaw and Margaret a. bradshaw Abstract. The dentition of some Lower Palaeozoic palaeotaxodontid bivalves is analysed; it is argued that variation in tooth form on the dental plate has a simple, direct relationship to the position of the hinge axis. In cases where the position of the hinge axis can be determined, the site of the ligament and the region of maxi- mum opening of the valves may also be inferred. The ligament is taken to be posterior, and the region of maxi- mum opening is regarded as anterior. A number of palaeotaxodontids are examined in the light of these suggestions. In the absence of a pallial sinus, orientation of fossil palaeotaxodontid bivalves becomes a matter of subjective choice. Furthermore, the initial decision as to the orientation colours all subsequent descriptions of the taxon in question. Various attempts have been made to overcome this problem, most commonly by reference to the morphology and orientation of surviving palaeotaxodontids, i.e. members of Nuculidae and Nuculanidae. Reference to the external ligament, invariably posterior in living forms, may also be made, but recognition of this feature is difficult where fossil material consists entirely of internal and external moulds. Such preservation is the rule rather than the exception in Lower Palaeozoic rocks. Driscoll (1964) has maintained that the position of accessory muscle scars in fossil palaeotaxodontid bivalves can be used to determine their orientation; but the success of this method also depends on good preservation, and often proves ineffective where correlation of the scars with those of modern forms is difficult. Since the forms being considered in this paper are Palaeozoic, anything from 300 to 500 million years may have elapsed since their fossilization, and hence such analogies with living taxa are at best tenuous. The use of a single morphological feature to determine the true orientation of fossil palaeotaxodontid bivalves would seem unreliable, and the use of several features might provide a sounder basis for determination. It is the purpose of this paper to suggest the use of the dentition, in conjunction with the pattern of musculature, etc., as a primary means of orientation of fossil palaeotaxodonts. However, it should be stressed that the use of the dentition is only suitable when the teeth along the dental plate show variation in both shape and size. The morphology of the dentition Marked variations in the shape and size of teeth along a single palaeotaxodont hinge were first observed in a well-preserved Ordovician (Llandeilo) fauna from Finistere, France (Bradshaw 1970). Further work shows similar variations in specimens from the Lower Devonian of New Zealand. In the Ordovician forms the dental plate is constructed of two main sections, one on either side of the umbo, and usually arranged at an angle to each other. The dentition [Palaeontology, Vol. 14, Part 2, 1971, pp. 242-9.] BRADSHAW AND BRADSHAW: FOSSIL PALAEOTAXODONT BIVALVE HINGES 243 may either bridge the junction of these sections continuously, or the two sections may abut against each other discontinuously. The two dental sections bear teeth that are different in both shape and size, one section having large chevron-shaped teeth (later argued to be anterior), the other much lower ridge-like teeth (later argued to be pos- terior) (text-fig. 1). 5mm text-fig. 1 . Detail of the hinge region of a right valve Pmeleda costae to show the different character of the teeth on each side of the umbo. Specimen 0.1, Middle Ordovician, Finistere. The larger teeth show a marked increase and decrease in size, with highest teeth near the centre of the row. Each tooth has a strong groove on the side facing away from the umbo, and the chevron is directed towards the junction of the two dental sections. When viewed along the axis of the dental section the teeth are not symmetrical, but are curved, with the ventral edge convex and the dorsal edge concave, the groove following this curvature (text-figs. 2, 3). This curvature of the tooth is in a plane which is not perpendicular to the axis of the dental section in which the tooth lies. The teeth on the other dental section have either a low symmetrical chevron form, or an angulated shape with a ventral limb so much longer than the dorsal that the tooth appears ridge- like. Such ridge-like teeth can sometimes be seen to pass gradually to more symmetrical teeth along a single dental section (text-fig. 3). The mechanics of valve opening (a) Theoretical. A general account of the mechanics of hinging of the bivalve shell can be found in Trueman (1964). In palaeotaxodontids with an angulated dentition composed of two distinct dental sections, such as the genera discussed here, the hinge 244 PALAEONTOLOGY, VOLUME 14 axis, i.e. the theoretical axis about which the valves rotate during opening, must correspond to one or other of the dental sections, or else lie somewhere between them (text-fig. 4). text-fig. 2. Left valve of Praeleda showing the curvature of the long anterior teeth. A A — anterior adductor muscle scar. A — anterior accessory muscle scar. Specimen A.20, Middle Ordovician, Finistere. text-fig. 3. The posterior dental section of Tancrediopsis ezquerrae, with the outline of the anterior dental section indicated. Unlike Praeleda the teeth of this genus are more similar in size and shape along the dental plate. Those to the posterior reach the same height as those to the anterior but are more numerous (see text-fig. 4b for entire dental plate). The teeth of the posterior section grade from a large curved chevron-shape distally, to low ridges close to the umbo. The low ridges suggest proximity to the hinge axis and the external ligament is thought to coincide with this part of the dental section. Specimen A.9, Middle Ordovician, Finistere. Where the hinge axis coincides with one dental section, the function and movement pattern, and consequently the appearance of the two series of teeth, will be quite different. During opening all teeth will move along curved paths centred on the hinge axis. The further a tooth is from the hinge axis the greater will be the influence of the arcuate movement path on tooth form. It is suggested that teeth near the hinge axis would be either low and rounded or ridge-like and set at right angles to the axis. Teeth distal to the axis would be much higher, so that their tips might remain engaged during maximum opening, and would be conspicuously arcuate about the axis, with curved faces or edges, BRADSHAW AND BRADSHAW: FOSSIL PALAEOTAXODONT BIVALVE HINGES 245 depending on their exact orientation. The two blade-like limbs of a chevron tooth would have curved faces and an arcuate junction, all concave towards the hinge axis. ( b ) Examples. The predicted pattern corresponds well with that found in many palaeo- taxodontids. The long arcuate teeth of Praeleda (text-figs. 1, 2) could not have been situated near the hinge axis, since any type of pivotal action would have fractured them, unless the corresponding sockets were much larger. There is no evidence to suggest this, the teeth and sockets appearing identical in size. A. PRAELEDA text-fig. 4. Diagrammatic representation of a, Praeleda, b, Tancrediopsis, and c, Nuculana (all left valves) to show the variation in dentition and its relationship to the inferred hinge axis. If it is accepted that the valves were most widely separated along the dental section bearing the highest teeth, then it follows that there could have been no external ligament above this section, and that the ligament must have been either concentrated near the umbo, or, more probably, dorsal to the shorter-toothed dental section. Genera (e.g. Tancrediopsis, text-fig. 4b) in which the hinge axis coincides with neither dental section, show intermediate characters, with different tooth types on the same dental section. Genera (e.g. Nuculana, text-fig. 4c) in which the dental sections were equally displaced from the hinge axis have two symmetrical rows of teeth on either side of the umbo. The position of the ligament may be also inferred from the disposition of the surfaces of each dental section to the commissural plane. In text-fig. 1 the plane of the section bearing the largest teeth is parallel with that of the commissural plane, whereas that of the narrower section is at an angle to it. The two sections merge below 246 PALAEONTOLOGY, VOLUME 14 the umbo. This difference appears directly related to the functioning of a ligament immediately above the narrower dental section. It will be obvious that when the valves are closed the surfaces of the wider dental section will be parallel and closely applied. By contrast, those of the narrower sections will be dorsally divergent. The relative positions of these two surfaces will ensure that the ligament is under tension (text-fig. 5). text-fig. 5. Schematic sections through Praeleda to show the differing relative positions of the anterior and posterior dental sections when the valves are A, closed and b, open. When the valves are closed the posterior dental sections are dorsally divergent and the anterior ones parallel. When the valves are open the posterior dental sections become parallel and the anterior ones dorsally convergent. The vertical lines are the lines of section. L — ligament. With relaxation of the adductor muscles and opening of the valves the tension in the ligament is reduced. The ligament decreases in width and the surfaces of the narrower dental section become parallel so that the entire surface is engaged. At the same time the surfaces of the wider dental sections become dorsally convergent. Fossil examples Cardiolaria beirensis is an Ordovician bivalve with a well-differentiated dentition (Bradshaw 1970, text-figs. 2, 3, 4). The largest teeth, which are curved and chevron in shape, are situated on the shorter side of the valve, suggesting that this genus has a ‘normal’ orientation. This assumption is further reinforced by the musculature of Cardiolaria beirensis. The anterior scars are deeply impressed, the adductor muscle being strengthened posteriorly by a sturdy myophoric plate. The three adjacent accessory muscle scars are analogous with the anterior protractors and anterior retractor muscles of the modern Acila divaricata and confirm that the shorter side of Cardiolaria is anterior. The anterior teeth are fewer than those on the longer posterior section which are chevron to ridge-like in form and smaller in size. BRADSHAW AND BRADSHAW: FOSSIL PALAEOTAXODONT BIVALVE HINGES 247 Praeleda costae and PraeJeda ciae are Ordovician bivalves with well-differentiated dentitions. In this genus large, strongly curved teeth are found on the extended side of the valve and low ridge-like teeth on the shorter side, suggesting a ‘reversed’ orientation (Bradshaw 1970, text-figs. 7-12). Deceptrix carinata from the Lower Devonian of Germany has a dentition very similar to that of Praeleda costae (see McAlester 1968, pi. 6, figs. 1-10), although its general shape is more symmetrical. In both these genera the hinge axis is suggested as corres- ponding to a major portion of the posterior dental section (text-fig. 4a). Tancrediopsis ezquerrae is an Ordovician species in which, although the two sections are of unequal length, both contain large chevron teeth at their distal ends, grading into low teeth towards the umbo (text-fig. 3). It is suggested that the hinge axis no longer coincides with one dental section as in Praeleda, but is removed to a position parallel to a line between the adductor muscle scars (text-fig. 4b). The abrupt change in tooth character in the ‘anterior’ section (Bradshaw 1970, text-fig. 5) results from the rapid convergence of this section with the hinge axis; and conversely, the slow change in the ‘posterior’ teeth indicates a less strong convergence of this section. Lines between teeth of similar geometry would parallel the hinge axis. Comparison with the geometry of other forms suggests that the longer side is posterior. In some ways this species could be thought of as approaching the geometry of Nuculana. In Nuculanella sp. of the New Zealand Lower Devonian the dental sections are equal in size and the teeth on them similar in number. Both series of teeth are chevron-shaped and curved, and the dental plate is interrupted by an internal ligament that would require a hinge axis almost equally displaced from each dental section. In Culunana sp. of the New Zealand Lower Devonian an internal ligament is clearly visible, but unlike Nuculanella sp. the dentition is well differentiated into two uneven series, although the smaller-sized teeth are not as low or ridge-like as those seen in either Praeleda or Deceptrix. Culunana sp. may well represent an evolutionary stage half- way between forms with a truly external ligament and differentiated teeth (e.g. Praeleda and Deceptrix) and those with a truly internal one and a uniform dentition (e.g. Nucufa, Nuculana, and possibly Nuculanella). Anthraconeilo taffiana, a Carboniferous bivalve well illustrated in McAlester 1968, pis. 18, 19, possesses a distinct pallial sinus indicating that the genus has a normal orientation. The longer, posterior side of the dental plate is straight and bears many regular teeth, distinctly chevron at the distal end of the series, but more assymetrical and ridge-like towards the umbo, showing similarity to the posterior series of Cardio- laria beirensis. The short, anterior dental section is wide and bears a few, large teeth that show rapid increase and decrease in size (see especially pi. 18, fig. 1). Paratype D, an articulated internal mould (pi. 18, fig. 2) clearly shows a curved profile to the anterior teeth. The geometry of the dentition independently suggests a normal orientation, with a hinge axis coincident with the lower teeth of the posterior section, and an external ligament immediately dorsal to them. General conclusions By reference to the burrowing action of modern palaeotaxodonts the authors suggest that the largest teeth on a differentiated dental plate of a fossil palaeotaxodont are most likely to be situated on the anterior dental section. 248 PALAEONTOLOGY, VOLUME 14 Observations by Yonge (1939) show Nucula to be a shallow burro wer, resting with the anterior margin of the shell parallel with the sediment surface, and being covered by approximately 1 mm of sediment when buried. He describes in detail the action of burrowing by Nucula nucleus (Linne). After first being extended ventrally into the sedi- ment, the closed foot is moved anteriorly and outwards. The two halves of the sole then open out widely to anchor in the sediment, and by the contraction of the pedal retractors the animal is pulled down and forwards. The foot is finally withdrawn between the text-fig. 6. Interpretive reconstruction of the opened valves of a Praeleda- type bivalve to show how a hinge axis coincident with the low ridge-like teeth would give rise to a large opening at the inferred anterior, and would require large teeth along that side. The anterior adductor muscle — AA, and the accessory muscles — A, are shown, together with the possible position of the extended foot. anterior margins of the shell after which the soles come together once more. It is significant to note that a large amount of anterior opening between the two valves is necessary to allow the large, extended nuculoid foot to be withdrawn into the shell. When resting and feeding below the surface only a small anterior and posterior opening is necessary to allow a slow current to pass through the mantle cavity. As already indicated, the large curved chevron teeth of many palaeotaxodont bivalves suggest a relatively large degree of opening between the dental sections that bear them. It seems probable that this opening was necessary to accommodate the protrusion and retraction of a large active foot similar to that of modern forms (text-fig. 6), but that the opisthodetic ligament required a different type of dentition to that of Nucula. Summary 1. Marked variations in size and shape of the teeth are visible on the hinge plates of Palaeozoic palaeotaxodontids, but have not been observed in modern forms. In this differentiated dentition the anterior dental section bears large, well-shaped, curved BRADSHAW AND BRADSHAW: FOSSIL PALAEOTAXODONT BIVALVE HINGES 249 chevron teeth, whereas the posterior section possesses low rounded teeth, chevron to ridge-like in form. 2. The curvature of the large teeth is centred on a projection of the part of the adjacent dental section that bears the lower teeth, and this line is considered to be the hinge axis. 3. In detail the shape of the teeth is governed by their orientation and position with respect to hinge axis. In order for the valves to open, those adjacent to the hinge axis must be low or ridge-like. Those furthest from it must be long and curved. 4. Forms with an internal ligament possess teeth that are more uniform in shape and size since the hinge axis is more symmetrically placed to the dental sections than is the case with an external ligament. 5. By reference to modern active palaeotaxodonts, the degree of opening suggested by the long curved teeth is considered to be anterior, necessitated by the size of the foot during retraction. This suggestion is supported by reference to the musculature and pallial lines of some palaeozoic palaeotaxodonts. Acknowledgements. The writers are indebted to Dr. R. M. Carter (University of Otago) for comments which significantly improved the paper. REFERENCES bradshaw, m. A. 1970. The dentition and musculature of some Middle Ordovician (Llandeilo) bivalves from Finistere, France. Palaeontology, 13, 623—45. driscoll, e. g. 1964. Accessory muscle scars, an aid to protobranch orientation. /. Paleont. 38, 61-6, pi. 16. mcalester, a. L. 1968. Type species of Paleozoic Nuculoid bivalve genera. Mem. Geol. soc. Am. 105. 143 pp., 36 pi. trueman, E. r. 1964. Adaptive morphology in palaeoecological interpretation. Pp. 45-74. In Approaches to Paleontology, ed. imbrie, j. and Newell, n., Wiley, New York. yonge, c. m. 1939. The Protobranchiate mollusca; a functional interpretation of their structure and evolution. Phil. Trans. R. S. Ser. B. 230, (566), 79-147. JOHN D. BRADSHAW MARGARET A. BRADSHAW Department of Geology University of Canterbury Christchurch Typescript received 23 June 1970 New Zealand C 7998 S REVISION OF ARENIG BIVALVIA FROM RAMSEY ISLAND, PEMBROKESHIRE by R. M. CARTER Abstract. Stratigraphically important Lower Ordovician (Arenig) bivalves from Ramsey Island, Pembroke- shire, are redescribed and illustrated. The two new genera and twelve new species of Hicks (1873) are reduced to the following five species: Praenucula menapiensis (Hicks), ‘ Praearca ' cambriensis (Hicks), ? Cyrtodonta oboloidea (Hicks), Glyptarca primaeva Hicks, and Actinodonta ramseyensis (Hicks). The genus Davidia is treated as a synonym of Actinodonta Phillips 1848. Although the earliest known bivalve has been described from strata of Middle Cambrian age in Spain (Vogel 1962), it is not until beds of Lower Ordovician age that bivalve faunas with any degree of diversity are found. Our knowledge of most of these faunas is still most inadequately based on their original, generally very old and idealis- tically illustrated, descriptions. In Europe three localities of Arenig age that are of particular interest are those of Bussaco in Portugal (Ribeiro and Sharpe 1853), where the fauna includes ribeirioids, Redonia, several species of ‘ Ctenodonta ’, and small ‘ Modioiopsis' ; of the Gres Armoricain of Normandy, from which Barrois (1891) described species of ‘Ctenodonta1 , Actinodonta, Lyrodesma, and Redonia that have recently been re-examined by Babin (1966); and of Ramsey Island, Pembrokeshire, from where H icks (1873) described twelve species of bivalve that were placed in the genera Ctenodonta, Modiolopsis, Palaearca, Davidia (nov.), and Glyptarca (nov.). (Two of Hicks’s species were originally published in Salter’s Cambridge Catalogue (1873). One, Ctenodonta rotunda Salter, is a nomen nudum; the other, Ctenodonta elongata Salter, has been referred to the Commission for designation as a nomen oblitum.) It is with the latter, apparently rich, bivalve fauna that this short paper is concerned. Originally I had hoped to re-collect sufficient material to enable a thorough revision of the fauna and modernization of the systematics. Through the kindness of Dr. D. E. B. Bates of Aberystwyth, two days were spent collecting on Ramsey Island from Hicks’s original locality in the Ogof Hen Formation (see Bates 1969, for a measured section) at Bay Ogof Hen. This short trip was only sufficient to establish that fossil preservation is generally poor, and hence that considerable time would be needed for the collection of a comprehensive topotypic suite of bivalves. Examination of the extant type material, variously lodged in the British Museum (Natural History), the Manchester Museum, the Sedgwick Museum, Cambridge, and the Institute of Geological Sciences, London, has established that much of Hicks’s original material is unable to be placed in a family, let alone a species, and that most of it should never have been named. However, in view of Hicks’s description of two new genera in this fauna, it was felt that even a brief description of the type material, together with re-illustration, would be of some value. [Palaeontology, Vol. 14, Part 2, 1971, pp. 250-61, pis. 38-39.] R. M. CARTER: ARENIG BIVALVIA 251 The fauna is described in systematic order, but to facilitate retrieval of information on any of Hicks’s original ‘species’, a synopsis of results is provided below, based on Hicks’s original faunal list. Hicks 1873 This paper (R) = restrict to type specimen Ctenodonta menapiensis Hicks (= Ctenodonta rotunda Salter 1873 nom. nud.) Ctenodonta cambriensis Hicks (R) (= Ctenodonta elongata Salter 1873 nom. oblit.) Palaearca hopkinsoni Hicks (R) Palaearca oboloidea Hicks (R) Glyptarca primaeva Hicks Glyptarca lobleyi Hicks (R) Davidia ornata Hicks (R) Davidia plana Hicks (R) Modio/opsis ramseyensis Hicks Modiolopsis solvensis Hicks Modiolopsis cambriensis Hicks Modiolopsis liomfrayi Hicks = Praenucula menapiensis (Salter) = ‘ Praearca ’ cambriensis (Hicks) ? = ? Cyrtodonta oboloidea (Hicks) ? = Cyrtodonta oboloidea (Hicks) = Glyptarca primaeva (Hicks) ? = ? Cyrtodonta oboloidea (Hicks) = Actinodonta ramseyensis (Hicks) ? = Actinodonta ramseyensis (Hicks) = Actinodonta ramseyensis (Hicks) = ‘ Praearca ’ cambriensis (Hicks) = Actinodonta ramseyensis (Hicks) = Actinodonta ramseyensis (Hicks) In the descriptions and plate captions, relevant museum collections are referred to as follows: SM — -Sedgwick Museum, Cambridge; IGS — Institute of Geological Sciences, London; BM — -British Museum (Natural History), London; MM — Manchester Univer- sity Museum, Manchester. Systematic groupings at the suprageneric level follow Cox and Newell, in Moore (1969). SYSTEMATIC DESCRIPTIONS Class bivalvia Linne 1758 Subclass palaeotaxodonta Korobkov 1954 Order nuculoidea Morton 1963 Superfamily nuculacea Gray 1824 Family praenuculidea McAlester 1969 Genus praenucula Pfab 1934 Type species ( original designation). Praenucula dispar expansa Pfab 1934. Praenucula menapiensis (Hicks 1873) Plate 38, figs. 1, 2 1873 Ctenodonta elongata Salter {nom. oblit.), p. 24 and figure. 1873 Ctenodonta menapiensis Hicks 1873, p. 47, pi. 5, figs. 6, 7. 1873 Ctenodonta rotunda Hicks; Hicks, p. 47. 1930 Ctenodonta menapiensis Hicks; Pringle, p. 12. Types. The holotype of elongata cannot be located in the collections of the Sedgwick Museum. Lectotype of menapiensis (here designated), the specimen figured by Hicks as plate 5, fig. 6, currently held in the Institute of Geological Sciences, London (reg. no. 23234, acc. no. 1/77). One other syntype. 252 PALAEONTOLOGY, VOLUME 14 the specimen figured as plate 5, fig. 7, was supposed to have been deposited in Hicks’s own collection, part of which is now in the Sedgwick Museum, and part in the Manchester University Museum. This specimen cannot be located. Precis of original description. Ovate, beaks prominent and pointed, placed nearer to the anterior margin ; surface with concentric growth-lines, fimbriated along ventral margins ; shell extremities rounded; muscle scars strong; teeth prominent. Revised description. This description is based on the few available topotypes, together with the lectotype. It is based on the assumption that the species has its umbones nearer the posterior end of the shell. Shell small (about 5 mm long and 3 mm high), with inconspicuous umbo placed at about posterior quarter. A prominent hinge plate carries the strong chevron taxodont dentition; because of this plate internal moulds carry sharp, conspicuous ‘umbones’. Preservation is not good enough to enable any accessory muscle scars to be discerned. The two adductors are both relatively well marked; the anterior is slightly larger, but the posterior is more deeply incised, especially dorsally. Internal valve margins smooth (not fimbriated); shell fairly thick. External valve surface with concentric growth-lines only. The lectotype demonstrates the dentition clearly; there are about seven taxodont teeth, the more posterior being markedly chevron-shaped. Topotype A44318 (text-fig. 1) shows four chevron teeth posterior to the umbo, two plain lamellar teeth under the umbo, and then an anterior series becoming increasingly chevroned (eleven more altogether). Posteriorly the teeth increase in size, and the ventral part of the chevron becomes the predominant half. Discussion. Although elongata Salter has strict priority over menapiensis Hicks, elongata has not been used in the literature since its introduction, and has been referred to the Commission for official designation as a nomen oblitum under Article 23 b of the Code. Of the presently described genera of palaeotaxodontids, Praenucula appears to repre- sent the most suitable location for menapiensis (see McAlester 1968, pi. 8, figs. 3-9). Further material from Ramsey Island may even result in the merging of menapiensis with Praenucula expansa, type species of the genus; the two forms appear almost indistinguishable in so far as one can judge from plates alone. EXPLANATION OF PLATE 38 Figs. 1-17. 1, Ctenodonta menapiensis Hicks. Lectotype (IGS 23234), x6: an internal mould. 2, C. menapiensis Hicks, latex rubber cast of lectotype, X 3. 3, Syntype of C. cambriensis Hicks (MM 10042), X 3. Probably Glyptarca. 4, C. cambriensis Hicks, latex rubber cast of syntype (MM 10042). 5, Ctenodonta cambriensis Hicks. Latex rubber cast of lectotype, X 3. (Also Glyptarca primaeva Hicks in upper right-hand corner.) 6, C. cambriensis Hicks. Lectotype (MM 10042), x3: an internal mould. 7, Palaearca oboloidea Hicks, holotype (SM A16743), X 3. 8, Glyptarca primaeva Hicks, latex rubber cast of lectotype (SM A16708-11, lectotype arrowed), X 3. 9, 12, G. primaeva Hicks, latex rubber cast of respectively the outside and inside of syntype (MM L10043). 10, G. primaeva Hicks, syntype (SM A1 670-7), x3. 11, Glyptarca lobleyi Hicks, holotype (IGS 24198), x3. 13, G. primaeva Hicks, syntype (MM L10043) (internal moulds only), X 3. 14, G. primaeva Hicks, syntype (IGS 24200), x3. 15, Modiolopsis solvensis Hicks, lectotype (IGS 22065), X 3. 16, Davidia plana Hicks, holotype (MM L10021), X 3. 17, M. solvensis, Hicks, latex rubber cast of lectotype, x 3. See text, p. 251, for revised taxonomy of Hicks’ species. Palaeontology, Vol. 14 PLATE 38 16 17 CARTER, Arenig Bivalvia R. M. CARTER: ARENIG BIVALVIA 253 text-fig. 1. Outline sketches of dentition of topotype Praenucula menapiensis ; all approx. X 5. (a) left valve, SM A44318; ( b ) right valve, SM A44308; (c) left valve, SM A44307. Genus praearca Neumayr 1891 Type species. Area? kosoviensis Barrande 1881. ‘ Praearca ’ cambriensis (Hicks 1873) Plate 38, figs. 3, 4, 5, 6 1873 Ctenodonta rotunda Salter (nom. mid.), p. 24. 1873 Ctenodonta cambriensis Hicks, p. 47, pi. 5, figs. 8, 9„ 1873 Ctenodonta e/ongata Hicks; Hicks, p. 47. 1873 Modiolopsis solvensis Hicks, p. 50, pi. 5, figs. 18, 19. 1930 Ctenodonta cambriensis Hicks; Pringle, p. 12. 1930 Modiolopsis solvensis Hicks; Pringle, p. 12. Types. Lectotype (here designated), the specimen figured by Hicks as plate 5, fig. 9, currently held in the Manchester Museum (reg. no. 10042, attica 8). One other syntype, also held in the Manchester Museum under the same registration number, is extremely badly preserved and almost certainly of a different species. Precis of original description. Ovate, nearly equilateral with sub-median umbones; regularly convex with strong growth-lines; muscle scars moderately impressed; teeth not as prominent as in C. menapiensis. Revised description ( based on the lectotype). Shell small (8 mm long and 4 mm high), and of ‘symmetrical-nuculanid’ shape. Umbones sub-central, not prominent. With narrow hinge plate running the length of the dorsal shell-edge; this plate carries an extremely faint impression of taxodont dentition. Sub-equal adductor muscle scars 254 PALAEONTOLOGY, VOLUME 14 can doubtfully be observed beneath the ends of the hinge plate. Ventral shell margins not denticulate. Modiolopsis solvensis Hicks; Plate 38, figs. 15, 17. Types. Lectotype (here designated), the specimen figured by Hicks as plate 5, fig. 18, currently held in the Institute of Geological Sciences (cat. no. 22065, accession no. 1/72). The other original syntype, that of plate 5, fig. 19, is missing. Precis of original description. Rhomboid, small, with a short anterior end and a longer posterior end. With strong anterior and posterior ridges stretching from the umbo to the margins. Hinge-line long and straight, muscle scars large and distinct. Revised description ( based on the lectotype ). The lectotype is the internal mould of the right valve of a small bivalve (length 10 mm, height 3-5 mm). Umbo is sub-central, distorted so as to look more anteriorly placed. There is a moderately wide hinge plate, but no hinge teeth are preserved. Ventral margins evenly rounded, with a narrow marginal shelf. Discussion. The name rotunda Salter would have priority over eambriensis Hicks, but as it was not originally accompanied by either figure or description (i.e. without an indication in terms of the Code, Article 12), rotunda may be treated as a nomen nudum. The preservation of the lectotype of eambriensis is barely sufficient for familial diagnosis, and placement in Praearca is an act of faith rather than of reason. However, the faintly discernible taxodont dentition together with the central umbo and contin- uously curved hinge plate makes this a ‘best guess’. Ctenodonta, or a new genus, are two other possible placements, and the possibility also exists that eambriensis is a distorted specimen of Praenucula menapiensis. Other shells on the same block as the lectotype of eambriensis (mainly Glyptarea) are uniformly compressed in a direction corresponding to dorso-ventral on the lectotype. It seems unlikely that the posteriorly placed beak of menapiensis could have been transformed into the sub-central beak of the lectotype of eambriensis by such a stress direction. Also, the lack of markedly impressed muscle scars encourages one to believe that eambriensis is distinct from menapiensis. (It is, however, probably correct to interpret the type of Modiolopsis solvensis Hicks as a distorted specimen of eambriensis.) Thus it appears probable that eambriensis is indeed a second species of ctenodontid in the Ramsey Island fauna. There appears to be no similarly symmetrical form in the fauna of the Gres Armoricain (Barrois 1891, Babin 1966); one might hope that ‘ Leda ’ escosurae Sharpe of the Bussaco fauna prove to be a senior synonym (this seems unlikely in view of its posterior carina). Otherwise the name eambriensis is best confined to the lectotype only, pending the discovery of better-preserved topotypes. Subclass pteriomorpha Beurlen 1944 Order arcoida Stolickzka 1871 Superfamily cyrtondontacea Ulrich 1894 Family cyrtodontidae Ulrich 1894 ? Genus cyrtodonta Billings 1858 Type species ( subsequent designation, Williams and Breger 1916). Cyrtodonta ritgosa Billings 1858. R. M. CARTER: ARENIG BIVALVIA 255 ? Cyrtodonta oboloidea (Hicks 1873) Plate 38, fig. 7 1873 Palaearca oboloidea Hicks, p. 48, pi. 5, fig. 10. ? 1873 Palaearca hopkinsoni Hicks, p. 48, pi. 5, fig. 11. ? 1873 Glyptarca lobleyi Hicks, p. 48, pi. 5, fig. 5. 1930 Palaearca oboloidea Hicks; Pringle, p. 12. ? 1930 Glyptarca lobleyi Hicks; Pringle, p. 12. ? 1930 Palaearca hopkinsoni Hicks; Pringle, p. 12. Types. Holotype, the specimen figured by Hicks as plate 5, fig. 10, currently held in the Sedgwick Museum (A16743). Precis of original description. Shell almost as long as high, flattened posteriorly, more inflated dorsally. Beak sub-central, nearer anterior end, overhanging cardinal margin; surface with strong growth-lines. Revised description ( based on holotype). Shell of pteriiform shape, with straight, long dorsal margin and expanded lobate posterior wing; 9 mm high (measured at right angles to the hinge line), 8 mm wide, moderately inflated. Anterior margin sharply truncated, with umbo situated at the anterior end of the dorsal margin. Though there is clearly a straight dorsal margin, there is no sign of any dentition. The holotype carries a well-marked growth pause at a shell height of about 5 mm. Palaearca hopkinsoni Hicks Types. Holotype (the only specimen of this species figured by Hicks, pi. 5, fig. 11) was not located during this study. Hicks attributed it to ‘Mr. Hopkinson’s collection’. This collection was formerly in the St. Albans City Museum, but was later donated to the Institute of Geological Sciences, London. Neither of these two museums is able to trace this specimen. Precis of original description. Oval, about J in long, and just over half as wide. Beak closer to anterior end; with two muscle-scars. Glyptarca lobleyi Hicks; Plate 38, fig. 11. Types. Holotype, the specimen figured by Hicks as plate 5, fig. 5, currently held in the Institute of Geological Sciences (cat. no. 24198, accession no. 1/74). Precis of original description. Largish shell (about in long, | in wide) with a wide posterior end, and a narrow hinge-margin. Inflated, with a prominent beak; with a marked sulcus ventrally. Revised description ( based on the holotype). Shell 12 mm high, 10 mm wide; extremely distorted. There is a suggestion of multiple teeth at the anterior end of the hinge line, supporting a tentative guess that the shell is perhaps cyrtodontid; placement as a cyrtodontid is also supported by the markedly overhanging umbo, which suggests a strong hinge plate. Discussion. The holotype of oboloidea (an internal mould and the only specimen that can be referred to the species with certainty) does not appear to be badly distorted, and the shape is certainly characteristic of the cyrtodontids, but in the absence of definitive cyrtodont dentition such judgement must at best be subjective. Palaearca hopkinsoni Hicks and Glyptarca lobleyi Hicks are themselves so badly preserved that they can only 256 PALAEONTOLOGY, VOLUME 14 doubtfully be included in the synonomy of oboloidea. Until better preserved material is collected, the names of all three species are best restricted to the types. Subclass palaeoheterodonta Newell 1965 Order modiomorphoida Newell 1969 Superfamily cycloconchacea, Ulrich 1884 Family cycloconchidae Ulrich 1884 Genus actinodonta Phillips 1848 Type species ( monotypy ). Actinodonta cuneata Phillips. Actinodonta ramseyensis (Flicks 1873) Plate 39, fig. 3 1873 Modiolopsis ramseyensis Hicks, p. 49, pi. 5, fig. 14. 1873 Modiolopsis homfrayi Hicks, p. 49, pi. 5, figs. 16, 17. 1873 Modiolopsis cambriensis Hicks, p. 50, pi. 5, fig. 20. 71873 Davidia ornata Hicks; p. 49, pi. 5, fig. 12. 71873 Davidia plana Hicks; p. 49, pi. 5, fig. 13. 1930 Modiolopsis ramseyensis Hicks; Pringle, p. 12. 1930 Modiolopsis homfrayi Hicks; Pringle, p. 12. 1930 Modiolopsis cambriensis Hicks; Pringle, p. 12. 71930 Davidia ornata Hicks; Pringle, p. 12. 71930 Davidia plana Hicks; Pringle, p. 12. Types. Holotype, the specimen figured by Hicks as plate 5, fig. 14 (this paper, PI. 39, fig. 3), currently held in the Manchester Museum (L10041). The other figured specimen (pi. 5, fig. 15) was only doubt- fully referred to this species by Hicks, and is now missing. Precis of original description. Ovate, strongly inflated along the dorsal margins. Anterior end short and obtusely rounded; posterior long and pointed. Beak incurved. Revised description. The holotype is a right valve about 28 mm long, 9 mm high, and with the umbo situated 5 mm from the anterior end. The umbo overhangs the dorsal margins (implying a hinge plate), and there is a long postero-lateral tooth sub-parallel to the shell edge. Posterior end tapering, but broken; anterior end fairly sharply rounded, with a faint trace of an anterior adductor scar. Valve margins smooth. Davidia ornata Hicks; Plate 39, fig. 5. Types. Holotype, the specimen figured by Hicks as plate 5, fig. 12 (this paper, PI. 39, fig. 5), currently held in the Institute of Geological Sciences (cat. no. 24197). explanation of plate 39 ( pars', see also p. 264) Fig. 1, Modiolopsis homfrayi Hicks, latex rubber cast of lectotype (IGS 22063), X3. 2, Modiolop- sis cambriensis Hicks, holotype (IGS 22062), X 3. 3, Modiolopsis ramseyensis Hicks, holotype (MM L10041), x3. 4, M. homfrayi Hicks, syntype (SM A16750), x3. 5, Davidia ornata Hicks, holotype (IGS 24197), X3. See text, p. 251, for revised taxonomy of Hicks’ species. Palaeontology, Vol. 14 PLATE 39 CARTER, Arenig Bivalvia GUPTA and WEBSTER, Stephanocrinus angulatus R. M. CARTER: ARENIG BIVALVIA 257 Precis of original description. Ovate, with raised beak and strong anterior and posterior ridges extending from the beak. Surface with strong growth lines; posterior flank with transverse striae converging obliquely from margin to umbo. Hinge-line straight. Revised description (based on holotype). The holotype is the internal mould of the posterior half of a fairly large ? left valve of a bivalve. Shell lengthened by distortion, umbo missing. Apparently with a long thin postero-lateral tooth parallel to the dorsal borders. The radial striae, if present, are extremely obscure. Davidia plana Hicks; Plate 38, fig. 16. Types. Holotype, the specimen figured by Hicks as plate 5, fig. 14 (this paper, PI. 38, fig. 16), currently held in Manchester Museum (L10021). Precis of original description. Ovate, with abruptly rounded extremities. Beak incurved, growth-lines not strongly marked. Revised description ( based on the holotype). The holotype is a flattened pair of opposing valves of a moderate-sized bivalve {not two primarily superimposed left valves as figured by Hicks), the right valve very obscure. The left valve is about 1 7 mm long and 8 mm high. Though somewhat distorted, the shell does have a triangular shape due to the sub-central umbones and the angled dorsal margins. There are probably lateral teeth sub-parallel to the shell edge on either side of the umbo. Modiolopsis homfrayi Hicks; Plate 39, figs. 1, 4. Types. Lectotype (here designated), the specimen figured by Hicks as plate 5, fig. 16 (this paper, PI. 39, fig. 1), currently held in the Institute of Geological Sciences (cat. no. 22063, accession no. 1/71). A further syntype, that of plate 5, fig. 17, is in the Sedgwick Museum (A16750; PI. 39, fig. 21). Precis of original description. Ovate, greatly elongated. With a short rounded anterior extremity. There is a moderately strong posterior ridge from the umbo to the margins; hinge-line long and straight. Revised description {based on the lectotype). The lectotype is one of the best-preserved specimens of all Hicks’s original syntypes. It is a slightly crushed and perhaps laterally a little attenuated, external mould of the dorsal regions of a fairly large bivalved shell (27 mm long, c. 6 mm high, umbo 6 mm from the anterior end). The posterior end is produced into a very sharply rounded extremity; anteriorly the shell is more broadly rounded. Umbones are situated close to the hinge, not prominent. Dorsal margins on either side of the umbones are straight, meeting under the umbones at an angle of c. 170 °. Teeth not clearly visible. Posterior to the umbones for about 6 mm is a well-defined raised structure on the valve edge that might be either a broken lateral tooth, or a ligament support of some type. It is separated from the main disc of the shell by a marked groove, and carries on its vertical surface a socket for a long thin lateral tooth from the right valve. The structure seems to be broken, and probably extended further posteriorly. Modiolopsis cambriensis Hicks; Plate 39, fig. 2. Types. Holotype, the specimen figured by Hicks as plate 5, fig. 20 (this paper, PI. 39, fig. 2), currently held in the Institute of Geological Sciences (cat. no. 22062, accession no. 1 /70). Precis of original description. Nearly oval, with equally rounded extremities. Beak moderately con- spicuous, nearer anterior end, with a ridge running to the posterior end of the shell. Revised description { based on the holotype). Badly preserved steinkern of ? actinodontid type shell, 20 mm long, 7 mm high, with umbones 6 mm from the anterior end. Anterior end broadly rounded; shell tapering posteriorly, with some suggestion of a long postero-lateral tooth. 258 PALAEONTOLOGY, VOLUME 14 Discussion. In the absence of external moulds, and particularly of further details of the dentition of the type, it is impossible to be sure of the placement of ramseyensis. How- ever, the postero-lateral tooth, the general shape of the shell, and the situation of the umbo all suggest actinodontid affinities, and on the present material ramseyensis could be indistinguishable from Actinodonta cuneata Phillips. A further factor influencing placement of the species in Actinodonta is the presence of an undoubted actinodontid hinge fragment in topotype material collected in 1966. Other possible generic locations include Modiolopsis or W/iiteavesia. Syntype A16750 (PI. 39, fig. 21) of Modiolopsis homfrayi Hicks is not well-enough preserved to be positively identifiable, but is probably a different species. The lectotype itself is best treated as a synonym of Actinodonta ramseyensis (Hicks). Hicks cited the main difference between homfrayi and ramseyensis as being the relatively more evenly rounded posterior end of the former. Yet on his only certainly identified ramseyensis (L 10041), the posterior end is broken off! Davidia plana Hicks and Modiolopsis cambriensis Hicks are so badly preserved that they can only doubtfully be referred to the synonomy of ramseyensis. Superfamily modiomorphacea Miller 1877 Family modiomorphidae Miller 1877 Genus glyptarca Hicks 1873 Type species {page preference, here designated). Glyptarca primaeva Hicks 1873. Precis of original generic diagnosis. Beak nearer anterior end, prominent and overhanging the hinge line. Two diverging ridges extend from the umbo to the ventral margin, thus enclosing a triangular sulcus. Anterior adductor scar more impressed than posterior. Thick narrow hinge plate with three teeth in front of umbo. Surface marked with lines of growth. Glyptarca primaeva Hicks 1873 Plate 38, figs. 8-10, 12-14 1873 Glyptarca primaeva Hicks, p. 48, pi. 5, figs. 1-4. 1930 Glyptarca primaeva Hicks; Pringle, p. 12. Types. Lectotype (here designated), the central specimen on the block figured by Hicks as plate 5, fig. 3 a (this paper, PL 38, fig. 8), currently held in the Sedgwick Museum (A1 6708-11). Other syntypes extant include the specimens of fig. 2 (IGS 24200), 3 (SM A16706-7) and 4 (MM L10043). The speci- men of Hicks’s plate 5, fig. 1, is missing. Precis of original description. Pear-shaped, \ in long and about | in wide. Anterior end short, posterior long and tapering, beak prominent. Ventral margin with marked sulcus. Muscle-scars well marked. Revised description. This is one of the few species in the Ramsey Island fauna that is present in sufficient numbers to allow a reasonably accurate description to be made; it is in fact the dominant animal in the bivalve rich layers of the Ogof Hen Formation. As it is the type species of Glyptarca, this relative commonness is particularly fortunate. R. M. CARTER: ARENIG BIVALVIA 259 The shell is small, and externally somewhat dumb-bell-shaped owing to the ventral sulcus; an average specimen measures about 5 mm long and 2-3 mm high; the shell is quite strongly inflated. Umbones broad, situated just anterior of the centre of the dorsal margin; assumed to be prosogryous. A well-marked dorsal inflection of the ventral margin results in the presence of conspicuous sulcus throughout adult life. External markings restricted to extremely subdued concentric growth lines. Internally, the valve margins are planar, and there are two sub-equal adductor muscle scars, the anterior more conspicuous. The dentition of the right valve consists of a long lamellar posterior tooth parallel to the dorsal margins, and a group of cardinal teeth under the umbones. Discussion. This is a distinctive genus, and one that unfortunately appears to have been omitted from the recently published bivalve volumes of the Treatise on Invertebrate Paleontology (Moore 1969). Byssodesma Isberg 1934 (Upper Ordovician, Sweden) and Colpomya Ulrich 1894 (Middle Qrdovician-Silurian, North America) are possible subjective junior synonyms of Glyptarca. Validity o/Davidia Hicks 1873. Type species (subsequent designation, Newell in Moore 1969, p. 820) Davidia ornata Hicks. Newell (in Moore 1969) has recently accepted Davidia as a valid genus and included it in the family Grammysiidae. In setting up the genus, Hicks (1873, p. 49) stated: ‘The sub-central umbo, equal extremities, and almost triangular shape of the shell are important characters, and sufficient to stamp it a new genus.’ The holotype is generically indeterminable, but probably a fragment of the posterior end of one of Hicks’s ‘ Modiolopsis ’ species, i.e. an actinodontid. The specimen is certainly not a suitable basis for continuing to recognize the genus Davidia. The policy followed here is to restrict the name to the type specimen, which is then treated as a synonym of Actinodonta ramseyensis (Hicks). SUMMARY AND CONCLUSIONS It is unfortunate that the preservation of the Ramsey Island fauna is, in most cases, too poor to allow accurate systematic placement. However, it is certain that some of Hicks’s names are synonyms, and that others are of no present use except as they apply to the type specimens. Hicks originally recognized twelve species of bivalve, placed in five genera two of them new ( Glyptarca , Davidia). It is suggested that the fauna in fact comprises the following five species : Praenucula menapiensis (Hicks) ‘ Praearca’’ cambriensis (Hicks) ? Cyrtodonta oboloidea (Hicks) Glyptarca primaeva (Hicks) Actinodonta ramseyensis (Hicks). In spite of the poor preservation, rendering accurate taxonomic work impossible, this fauna is one of particular interest because of its low stratigraphic position. The over-all 260 PALAEONTOLOGY, VOLUME 14 Ramsey Island fauna is one of the most diverse early Ordovician faunas known, con- taining brachiopods, trilobites, and gastropods, as well as the first recorded crinoids (Bates 1968) and one of the earliest asterozoans (Spencer 1950). Different communities of animals appear at different levels in the section, with brachiopod and trilobite domin- ated (numerically) assemblages the most common. The richest bivalve community, dominated by Glyptarca, occurs in silty mudstones some 40-43 ft above the base of the section (see Bates 1969). Other bivalves, particularly Praenucula, are present in subor- dinate numbers, trilobite fragments are relatively common, and orthides are rare. Further up the section, bivalves occur as subordinate members of an orthide brachiopod community (silty mudstone) and a gastropod/crinoid community (shale). Thus, the Ramsey Island faunas are of considerable importance in that they document the ecologic integration of bivalves into some of the earliest known diverse invertebrate faunal assemblages. Furthermore, the common presence of double-valved shells, coupled with the numerical abundance and the general lack of signs of transport or environmental damage, indicate that many of the Ramsey Island fossils represent life assemblage conditions. These important faunas would amply repay further careful ecological investigation. Acknowledgements. I am particularly grateful to Dr. D. E. B. Bates of the University of Wales, Aberystwyth, for initially suggesting this revision be undertaken, and for showing me the Ramsey Island fauna in the field; thanks are also due to Dr. Bates, and Associate-Professor J. D. Campbell, for checking the manuscript and suggesting improvements, and to Dr. C. Babin for advice on some aspects of the systematics. For access to, and the loan of, collections in their care, I am indebted to Dr. R. M. C. Eagar, Mr. S. Ware, Miss N. Armstrong, Mr. A. G. Brighton, Mr. J. M. Edmonds, and Dr. D. A. Bassett. The work was carried out during the tenure of a Commonwealth Scholarship, awarded by the British Council, and this financial support is gratefully acknowledged. Thanks are also due to the Cambridge Philosophical Society for a travel grant enabling me to study the classic collections of Lower Palaeozoic Bivalvia held in the Narodni Museum, Prague. REFERENCES babin, c. 1966. Mollusques Bivalves et Cephalopodes du Paleozoique Armoricain. Brest, 471 pp. barrois, c. 1891. Memoire sur la faune du gres armoricain. Ann. Soc. Geol. Nord. 19, 134-237. bates, d. e. b. 1968. On ‘ Dendrocrinus ’ cambriensis Hicks, the earliest known crinoid. Palaeontology 11,406-9. 1969. Some early Arenig brachiopods and trilobites from Wales. Bull. Brit. Mus. Nat. Hist. 18 (1), 28 pp. hicks, h. 1873. On the Tremadoc rocks in the neighbourhood of St. David’s, South Wales, and their fossil contents. Q. J. Geol. Soc. Lond. 29, 39-52. mcalester, a. L. 1968. Type species of Paleozoic Nuculoid Bivalve Genera. Mem. Geol. Soc. Am. 105, 143 pp. moore, R. c. (ed.) 1969. Treatise on Invertebrate Paleontology, Part N, Mollusca 6, Bivalvia. Geol. Soc. Am. and Univ. Kansas Press. pringle, J. 1930. The geology of Ramsey Island, Pembrokeshire. Proc. Geol. Ass. Lond. 41, 1-31. ribiero, c. and sharpe, d. 1853. On the Carboniferous and Silurian Formations of the neighbourhood of Bussaco in Portugal. Proc. Geol. Soc. Lond. 9, 135-61. salter, J. w. 1873. A Catalogue of the Collection of Cambrian and Silurian Fossils contained in the Geological Museum of the University of Cambridge. Cambridge. R. M. CARTER: ARENIG BIVALVIA 261 spencer, w. k. 1950. Asterozoa and the study of Palaeozoic faunas. Geol. Mag. 87, 393-408. vogel, k. 1962. Muscheln mit Schlosszahnen aus dem Spanischen Kambrium und ihre Bedeutung fur die Evolution der Lamellibranchiaten. Verl. Akad. Wissensch., Ab. Math. Naturw. 4, 197-244. R. M. CARTER Department of Geology University of Otago Dunedin Final typescript received 12 October 1970 New Zealand STEPHANOCRINUS ANGULATUS CONRAD (CRINOIDEA) FROM THE SILURIAN OF KASHMIR by v. J. gupta and G. d. Webster Abstract. The crinoid Stephanocrinus angulatus Conrad is reported from the lower part of the Naubug Beds of Kashmir. This represents the first record of Stephanocrinus from Asia and corroborates a Silurian age for the lower part of the Naubug Beds. Stephanocrinus angulatus Conrad has been recognized for many years as a Middle Silurian index fossil in North America. Discovery of this crinoid in Kashmir, in strata of Late Silurian age, significantly extends its known palaeogeographic and geologic range. The Palaeozoic section east of Islamabad (Anantnag), Kashmir is moderately well exposed in the flanks of a north-west plunging anticline (text-fig. 1). Silurian fossils have previously been reported from the Harpatnar and Naubug Beds. The Harpatnar Beds contain graptolites of an early to middle Ludlow age (Berry and Gupta 1966). A diverse fauna including brachiopods, trilobites, nautiloids (Reed 1912), crinoids (Sahni and Gupta 1965), fishes, conodonts, and corals (Gupta 1969u) have been found in the sandy calcareous shales of the upper part of the Naubug Beds. In addition, Gupta recently found five dorsal cups of Stephanocrinus angulatus Conrad in the lower part of the Naubug Beds. This diverse fauna suggests a Late Silurian-Early Devonian age for the upper part of the Naubug Beds (Gupta 1969 b). The Naubug Beds are conformably overlain by the Muth Quartzite which has yielded brachiopods, corals, trilobites, pelecypods, and fishes of early Middle Devonian age (Gupta 1969c). SYSTEMATIC PALAEONTOLOGY Phylum echin odermat a Subphylum crinozoa Matsumoto 1929 Class crinoidea J. S. Miller 1821 Order coronata Jaekel 1921 Family stephanocrinidae Wachsmuth and Springer 1887 Genus stephanocrinus Conrad 1842 Stephanocrinus angulatus Conrad 1842 1891 Stephanocrinus obpyramidalis S. A. Miller, p. 634, pi. 6, fig. 6. ? 1892 Stephanocrinus cornetti S. A. Miller, p. 12, pi. 2, figs. 10-12. 1915 Stephanocrinus angulatus Conrad; Bassler, p. 1187 (see this reference for lengthy syno- nomy prior to 1915). 1926 Stephanocrinus angulatus Conrad; Springer, p. 139, pi. 31, figs. 13-16. 1961 Stephanocrinus angulatus Conrad; Fay, p. 236, pi. 1. 1962 Stephanocrinus angulatus Conrad; Fay, p. 206, pi. 35, text fig. 1. [Palaeontology, Vol. 14, Part 2, 1971, 262-5, pi. 39.] GUPTA AND WEBSTER: STEPHANOCRINUS ANGULATUS CONRAD (CRINOIDEA) 263 text-fig. 1. Detailed geological map of the Naubug Valley area, showing the position of the fossil localities in the Naubug Beds. Inset map shows the generalized geology of the Vale of Kashmir and the location of the Naubug Valley area, east of Islamabad (Anantnag) with reference to the Indian subcontinent. 264 PALAEONTOLOGY, VOLUME 14 Description. An adequate description of Stephanocrinus angulatus was given by Hall (1852, p. 212) and significant morphological data were added by Fay (1961, p. 236; 1962, p. 206). Therefore only a brief description of the Naubug specimens is given for comparison purposes. Dorsal cup elongate pyriform, base triangular, stem impression round. Basals 3, radials 5, interradials 5, no other plates preserved. Ornamentation twofold, coarse sharp oblique ridges extending from base of cup to summit plane and fine transverse ridges and grooves from base of cup to tips of coronal processes. Measurements of three specimens are given in Table 1. table 1. Measurements in millimetres of Stephanocrinus angulatus Conrad from the Naubug Beds of Kashmir. Specimen Width number Height max. min. av. HI W ratio F 1310 141 90 7-4 8-2 1-72 F 1311 14 8 8-6 6-7 7-65 1-94 F 1312 13-7 8-7 6-8 7-75 1-77 Comments. A review of the illustrated specimens of Stephanocrinus angulatus revealed that the species is quite variable in proportions. Height to width ratios range from 1-5 to 3. There is also some variation in the prominence of the coarse linear ridges which are always present. The fine transverse ridges and grooves are sometimes masked by matrix material. S. obpyramidalis S. A. Miller is thought to be a slightly abraided specimen of S. angulatus. S. cornetti S. A. Miller is questionably considered a very elongate form of S. angulatus. In North America the range of Stephanocrinus angulatus is middle through upper Niagaran or approximately equivalent to the Wenlockian and lower Ludlovian of the British standard section. Ranges of all other species of Stephanocrinus are within this same span from North America. Bather (1900, pp. 96, 145) has also recorded the genus from the Silurian of England. The Naubug specimens of S. angulatus are the first reported from Asia and can be no older than early or middle Ludlow age because graptolites of that age have been found in the underlying Harpatnar Beds. The strati- graphic position and associated fauna of the lower part of the Naubug Beds suggests a middle or late Ludlow age thus slightly extending the recognized range of S. angulatus. Material. All specimens are deposited in the Museum of the Geology Department, Panjab University, Chandigarh, India, and bear the catalogue numbers PUGD F 1310-14. Three of these are illustrated in Plate 39. Figure 9 is a line sketch made by Gupta and the other specimens were coated with ammonium chloride before photographing. EXPLANATION OF PLATE 39 (pars) (see opposite p. 256) Stephanocrinus angulatus Conrad. Figs. 6-8, specimen PUGD FI 311, A ray, B ray, and oral views, x2; 9, specimen PUGD FI 3 12, line sketch of lateral view, x3; 10-12, specimen PUGD FI 310, oral, A ray, and C-D interray views, x2. All specimens from the lower part of the Naubug Beds, Kashmir. GUPTA AND WEBSTER: STEPHANOCRINUS ANGULATUS CONRAD (CRINOIDEA) 265 Locality. All specimens are from the upper part of a 100-ft thick succession of thinly bedded blue-grey to rusty calcareous sandy shales in the lower part of the Naubug Beds, which are poorly exposed above the west bank of the Naubug River on Bumtung Ridge, approximately one mile north of the village of Naubug, Kashmir, India. Co-ordinates of the fossil locality are longitude 33° 40' 30" N and latitude 75° 23' 00" E. REFERENCES bassler, r. s. 1915. Bibliographic index of American Ordovician and Silurian fossils. U.S.Nat.Mus. Bull. 92. 1521 pp. bather, f. a. 1900. In A Treatise on Zoology, ed. lankester, e. ray. Part III. The Echinoderma. London. berry, w. b. n. and gupta, v. j. 1966. Monograptids from the Kashmir Himalayas. /. Paleont. 40, 1338-44, pi. 167. fay, r. o. 1961. The type species of Stephanocrinus Conrad. Okla. Geol. Notes, 21, 236-8, pi. I. 1962. Ventral structures of Stephanocrinus angulatus Conrad. /. Paleont. 36, 206-10, pi. 35. gupta, v. j. 1969a. Lower Palaeozoic stratigraphy of the area southeast of Srinagar. Panjab Univ. Res. Bull. N.s. 20, 1—13. 1969 b. Silurian-Devonian boundary in the Kashmir Himalayas. Bull. Geol. Soc. India, 6, 26-7. 1969c. The stratigraphy of the Muth Quartzite of the Himalayas. J. Geol. Soc. India, 10, 88-94, 2 text-figs. hall, J. 1852. Natural History of New York. Paleontology, pt. 6, vol. 2. 362 pp., 85 pi. miller, s. A. 1891 (advance publication). 17th Ann. Rept. Geol. Surv. Indiana. 705 pp., 20 pi. 1892 (advance publication). 18th Ann. Rept. Geol. Surv. Indiana. 365 pp., 12 pi. reed, f. r. c. 1912. Silurian fossils from Kashmir. Rec. Geol. Surv. India, 42, 16-33, pi. IX. sahni, M. R. and gupta, v. J. 1965. Silurian crinoids from the Kashmir Himalayas. Panjab Univ. Res. Bull. N.s. 16, 247-8, 1 text-fig. springer, F. 1926. American Silurian crinoids. Smithsonian Inst. Pub. 2871, 239 pp., 33 pi. v. J. GUPTA Panjab University Chandigarh India G. D. WEBSTER Washington State University Pullman Typescript received 26 June 1970 Washington, U.S.A. C 7988 T SOME BAJOCIAN AMMONITES FROM WESTERN SCOTLAND by N. MORTON Abstract. In western Scotland Bajocian ammonites occur in the Bearreraig Sandstone of Skye and Raasay. In the Humphriesianum Zone (Lower Bajocian) the fauna includes Stephanocerataceae and rare Haplocerata- ceae ( Lissoceras ) and Oppeliaceae ( Oppelia ). The Stephanocerataceae are represented by one family Stephano- ceratidae, divided into two subfamilies on the basis of type of dimorphism — Stephanoceratinae (including Otoitinae) and Sphaeroceratinae. In Skye the Stephanoceratinae are represented mainly by the genus Stephano- ceras, with the macroconch (subgenus Stephanoceras ) much more abundant than the microconch (subgenus Normannites). Teloceras also occurs, but is rare. The Sphaeroceratinae, represented by Chondroceras, are also rare. In the Upper Bajocian the Perisphinctaceae are represented by species of Garantiana from the Subfurcatum Zone. The Bearreraig Sandstone is the thickest known development of the Aalenian and Bajocian in Britain. The stratigraphy has already been described (Morton 1965, 1969). The Lower Bajocian is mainly composed of sandstones, cross-bedded in southern Skye (Strathaird) and Raasay, but in northern Skye (Trotternish) normal-bedded and ammonitiferous. The Upper Bajocian is shale or clay over most of the area, but passing into sandstone in northern Trotternish. The purpose of this paper is to describe the ammonite fauna of the Bajocian, excluding the Sonniniidae which will be discussed later. The zones and subzones of the Bajocian Stage are summarized in Table 1. The arrangement of those in the lowermost Bajocian (Sowerbyi Zone) is provisional, but does not alfect the present discussion (see also Torrens 1969, p. 302). As used here Lower Bajocian is synonymous with Middle Bajocian of traditional British usage. The recogni- tion of a separate Aalenian Stage in accordance with the recommendations of the 1967 Luxembourg Jurassic Colloquium leaves a Bajocian Stage divided into two parts — Upper Bajocian as before, and Lower Bajocian, formerly called Middle Bajocian. STRATIGRAPHY Lower Bajocian. With the exception of the Sonniniidae the ammonites of the Lower Bajocian were all found in Trotternish, north-east Skye, at three localities in the Upper Sandstones (Morton and Hudson 1964, p. 532 = Rigg Sandstone of Anderson and Dunham 1966, p. 12). From south to north these are: 1 . Torvaig (NG 502444) : In the basal bed of the Upper Sandstones (see Morton 1965, pp. 197-8) there occur Stephanoceras ( Stephanoceras ) nodosum (Quenstedt), S. (S.) aff. nodosum and aff. macrum (Quenstedt), ? Chondroceras evolvescens (Waagen) and Lissoceras oolithicum (d’Orbigny). 2. Bearreraig: Ammonites were found mainly at two localities in the Upper Sandstones. In the pipe- line cutting (NG 515524) Stephanoceras ( Stephanoceras ) pyritosum (Quenstedt), S. (S.) aff. triplex Weisert, S. ( Normannites ) sp. were found in situ approximately 30 m above the base, and 4 m higher a single specimen of Teloceras ( Teloceras ) blagdeni (J. Sowerby). On the north side of Bearreraig Bay, [Palaeontology, Vol. 14, Part 2, 1971, pp. 266-93, pis. 40-51.] N. MORTON: BAJOCIAN AMMONITES 267 table 1. Zones and Subzones of the Bajocian Stage. Substages Zones Subzones Bomfordi Upper Parkinsoni Parkinsoni Bajocian Truelli Garantiana Subfurcatum Humphriesianum Lower Bajocian Sowerbyi Blagdeni Humphriesianum Sauzei Laeviuscula Trigonalis Discites at Rudha Sughar (NG 518537), ammonites were found in loose blocks from the lower part (approxi- mately 30 m) of the Upper Sandstones: Stephanoceras ( Stephanoceras ) mutabile (Quenstedt), S. ( S .) aff. brodiaei (J. Sowerby), S. (S.) nodosum (Quenstedt), S. (S.) aff. nodosum and aff. macrum (Quenstedt) (intermediate), S. (S'.) alf. triplex Weisert, S. ( S .) pyritosum (Quenstedt), S. ( Normannites ) ? orbignyi (Buckman), Oppelia ( Oppelia ) ? subradiata (J. de C. Sowerby). The blocks from the Upper Sandstones can easily be distinguished from those of the underlying Massive Sandstone (see Morton 1969, p. D28), but more detailed stratigraphy is not possible and even the distinctive purplish-weathering matrix of some specimens could not be traced in the outcrops further south. 3. Rigg (NG 521566): The lower part of the Upper Sandstones is exposed on the shore to the north and south of Rigg waterfall. The base of the Upper Sandstones is below sea level, but probably not more than 5-10 m below the lowest exposed bed, so that the ammonites come from approximately the same part of the Upper Sandstones as those at Rudha Sughar. The succession is summarized in text-fig. 1, together with data from Bearreraig and Torvaig. Two specimens from Rigg in the collection of the Geological Survey, Edinburgh are S. (S.) pyritosum (Quenstedt) and Chondroceras evolvescens (Waagen). These faunas all belong to the Humphriesianum Zone, and it appears that the base of the zone in Trotternish coincides with the base of the Upper Sandstones. It is marked faunally by the incoming of Stephanoceras. The earliest species of Stephanoceras in Skye is S. ( S .) nodosum (Quenstedt), but in other areas this and related species (‘ Skirro - ceras ’), occur earlier, in the Sowerbyi Zone (Sauzei Subzone). The single specimen of Teloceras ( T .) blagdeni (J. Sowerby) at Bearreraig, above most of the Stephanoceras , suggests that it may be possible to recognize the Blagdeni Subzone. Upper Bajocian. Over most of the area the Upper Bajocian is marked by the sudden incoming of clay or shale sedimentation, the Garantiana Clay. In north Trotternish the Garantiana Clay passes into sandstone and it becomes difficult to define the boundary between the Bearreraig Sandstone and the overlying Great Estuarine Series, other than at the top of the highest bed containing marine fossils (Hudson 1969). 268 PALAEONTOLOGY, VOLUME 14 SECTION L. ool i t h icum O. (o.) subrad iata S. (s.) mutabi le S. (s.) aff. brodiaei S. (s.) nodosum S. s. sp. aff. nodosum aff. macrum S.(s.)af r. triplex S. (s.) py r i tosum S. (n.) ? orbignyi S.(n.)? densum T. (t.) blagden i C. evol vescens SUBZONES BEARRE R A IG LOOSE BLOCKS X X X X X X X X (Humphriesianum Zone) meters above base a S Blagdeni Subzone — ? — ? — ? — Humphri esianum Subzone j J * •k on X *1 UJ 2 ■ Zi 1 o s X X X X X LU Q_ CL O ? QC o o f— O 4 X X X X text-fig. 1. Ammonite succession in the Upper Sandstones (Humphriesianum Zone) of Trottemish, Skye. N MORTON: BAJOCIAN AMMONITES 269 Ammonites were found in the Garantiana Clay in the cliffs above Prince Charles’s Cave, Trotter- nish — Garantiana ( G .) filicosta Bentz — and at Capach, Strathaird — G. (G.) ? baculata (Quenstedt) and G. (G.) filicosta Bentz. Ammonites from Storab’s Grave, Isle of Raasay, were identified by Buckman (in Lee 1920), and the revised identifications are: Spec. no. Buckman’ s identification Revised identification GSE 2888 Strenoceras bifurcatum G. (G.) filicosta GSE 2889 Strenoceras subfurcatum G. (G.) ? baculata GSE 2921-2 Garantiana coronata? G. (G.) ? baculata GSE 2925 Garantiana alticosta? ? Strenoceras sp. GSE 2926 Garantiana alticosta? Garantiana sp. indet. GSE 2927 ? Garantiana subgaranti G. (G.) filicosta GSE 2928 ? Garantiana subgaranti G. (G.) filicosta GSE 2929 Strenoceras minimum G. (G.) sp. GSE 2930 Strenoceras minimum G. (G.) sp. The specimens from Raasay were identified by Buckman (in Lee 1920, p. 47) as indicating the presence of both the Subfurcatum and Garantiana Zones. However, both G. (G.) baculata (Quenst.) and G. (G.) filicosta Bentz come from the Subfurcatum Zone (Bentz 1928, Buckman 1925, Hahn 1966, Pavia and Sturani 1968, Westermann 1967), so that only the Subfurcatum Zone is proved in the Garantiana Clay. The Garantiana Clay passes up into the Basal Oil Shale and the White Sandstone of the Great Estuarine Series, which may also be of Upper Bajocian age (see Hudson 1962), but are not of normal marine facies and do not contain ammonites. Dimensions. The dimensions given for the specimens are as follows : D. Diameter of specimen (H, O, S, P). Wh. Whorl height (H, O, S, P). Wb. Whorl breadth (H, O, S, P). Ud. Diameter of umbilicus (H, O, S, P). PI. Length of primary rib, from umbilical seam to tubercle or point of furcation (S, P). Pn. Number of primary ribs in the last whorl, or part of whorl (S, P). Pd. Distance between primary ribs at mid-whorl position, at part of whorl where D., etc., were measured (S, P). SI. Length of secondary rib, from tubercle or point of furcation to mid- venter (S, P). Sn. Number of secondary ribs in the last whorl or part of whorl (O, P). Tn. Number of tubercles in the last whorl. Where possible this has been measured at half-whorl intervals, along with the umbilical diameter (the only size measurement which can be made directly on inner whorls), such specimens are indicated with an asterisk (S). Td. Distance between tubercles, at point where D., etc., were measured (S). Tp. Position of tubercles: (A/Bx 100, where A is the distance from the tubercle to the umbilical seam, and B the height of the whorl, both measured along a line through the centre of the umbilicus) (S). The letters in brackets indicate to which of the superfamilies the measurement is appropriate: H — Haplocerataceae, O — Oppeliaceae, S — Stephanocerataceae, P — Perisphinctaceae. The dimensions are given in millimetres and are also expressed as percentages of the diameter. In cases where the dimension given is approximate, it is indicated by being preceded by ‘ c .’ (circa). SYSTEMATIC DESCRIPTIONS Superfamily haplocerataceae Zittel 1884 Arkell (1957) combined the haploceratids and oppeliids in one superfamily, but they should probably be regarded as distinct superfamilies (Callomon in litt., Dec. 1969). 270 PALAEONTOLOGY, VOLUME 14 The Haplocerataceae are rare in the Bajocian of western Scotland, only one specimen having been found in Trotternish. Family haploceratidae Zittel 1884 Genus lissoceras Bayle 1879 Type species. Ammonites psilodiscus Schloenbach 1865, by original designation. Includes. Lissoceratoides Spath 1923. Lissoceras oolithicum (d’Orbigny) Plate 40, figs. 1-2 1845 Ammonites oolithicus d'Orbigny, p. 383, pi. 126, figs. 1-4. 1923 Lissoceras oolithicum d’Orbigny; Fallot and Blanchet, pp. 141-2. 1927 Lissoceras oolithicum d’Orbigny; Roman and Petouraud, p. 48, pi. 5, figs. 12-14. 1937 Lissoceras oolithicum d’Orbigny; Gillet, p. 110. Material. One specimen — HMS 26350. Dimensions. D. Wh. Wb. Ud. HMS 26350 30-5 16-2(53) 94(31) 6-0(20) Description. Involute, moderately compressed; smooth except for faint growth-lines especially where the shell is preserved and on outer half of whorl sides on body chamber; venter rounded and unkeeled; suture line moderately complex, with second lateral saddle at least as large as first lateral saddle. Discussion. The specimen is a typical smooth Lissoceras. It is smoother than the Sowerbyi Zone L. semicostulatum Buckman, and appears to be identical with the common L. oolithicum (d’Orbigny). Most records of this species are from the Upper Bajocian, with the exception of Gillet (1937), who recorded it from the Sauzei Subzone. Locality. Humphriesianum Zone; basal bed of Upper Sandstones, Torvaig, Trotternish, Skye. EXPLANATION OF PLATE 40 All figures natural size. Figs. 1, 2, Lissoceras oolithicum (d’Orbigny); HMS 26350, Humphriesianum Zone, basal bed of Upper Sandstones, Torvaig, Trotternish, Skye. 3, Oppelia ( Oppelia ) ? subradiata (J. de C. Sowerby); HMS 26351, Humphriesianum Zone, loose block of Upper Sandstones, Rudha Sughar, Bearreraig, Trotternish, Skye. 4, Oppelia ( Oppelia ) ? subradiata (J. de C. Sowerby); HMS 26352, Humphrie- sianum Zone, lower part of Upper Sandstones, shore just north of Rigg waterfall, Trotternish, Skye. 5, 7, Stephanoceras ( Stephanoceras ) mutabile (Quenstedt); HMS 26353, Humphriesianum Zone, loose block of Upper Sandstones, Rudha Sughar, Bearreraig, Trotternish, Skye. 6, 9, Stephanoceras ( Stephanoceras ) mutabile (Quenstedt); HMS 26354, Humphriesianum Zone, lower part of Upper Sandstones, shore just south of Rigg waterfall, Trotternish, Skye. 8, 10, Stephanoceras {Stephanoceras) mutabile (Quenstedt); HMS 26356/1, Humphriesianum Zone, lower part of Upper Sandstones, shore just north of Rigg waterfall, Trotternish, Skye. Palaeontology, Vol. 14 PLATE 40 MORTON, Bajocian ammonites N. MORTON: BAJOCIAN AMMONITES 271 Superfamily oppeliaceae Bonarelli 1894 Family oppeliidae Bonarelli 1894 The Oppeliaceae are represented by rare Oppelia in the Humphriesianum Zone in Trotternish. The dimorphism of Lower Bajocian Oppeliidae is not entirely clear, but the microconch Oecotraustes Waagen 1869, monographed by Stephanov (1966), ranges down into Lower Bajocian (cf. Arkell 1957, p. L276) and appears to be the microconch of Oppelia. Genus oppelia Waagen 1869 Macroconch subgenus Oppelia Waagen 1869 Type species. Ammonites subradiatus J. de C. Sowerby 1823, subsequent designation by H. Douville 1884 (ICZN Opinion 324, see Arkell 1957, p. L275). A later designation by Buckman (1920) of A. subradiatus Waagen (non Sowerby) (= O. lectotypa Buckman 1924) is invalid. Oppelia ( Oppelia ) ? subradiata (J. de C. Sowerby) Plate 40, figs. 3-4 1823 Ammonites subradiatus J. de C. Sowerby, p. 23, pi. 421, fig. 2. 1909 Ammonites subradiatus J. de C. Sowerby; Buckman and Secretary, pi. 6, fig. 3 a-b. 1951 (1951-9) Oppelia ( Oppelia ) subradiata (J. de C. Sowerby); Arkell, pp. 50-1, text-fig. 11. Material. Two crushed specimens — HMS 26351, HMS 26352. Dimensions. D. Wh. Wb. Ud. Sn. HMS 26351 37-9 20-5(54) 4-1(11) 5-2(14) 31 H wh. HMS 26352 37-8 20-6(55) - 4-8(13) - Description. Involute, flattened by post-depositional compaction; no primary ribs visible so that inner half of whorls appears smooth ; outer half with close fine secondary ribs which curve forwards onto the edge of the venter; venter (visible on HMS 26351) narrow, smooth except for faint suggestion of a keel locally; suture (partially visible on HMS 26351) moderately complex with second lateral saddle almost as large as first lateral saddle. Discussion. The poor preservation, especially the crushing, makes certain identification almost impossible, but the specimens seem to be very close to the typical O. (O.) subradiata (J. de C. Sowerby) figured by Arkell (1951-9). The holotype of the species comes from the Sauzei Subzone (Arkell 1951, p. 50, 1957, p. L275), whereas Roman (1938, p. 157) and other authors indicate Upper Bajocian (Garantiana Zone). Localities. Humphriesianum Zone; HMS 26351 from loose block of the Upper Sandstones, Rudha Sughar Bearreraig; HMS 26352 from lower part of Upper Sandstones, shore below Rigg. Both localities in Trotternish, Skye. 272 PALAEONTOLOGY, VOLUME 14 Superfamily stephanocerataceae Neumayr 1875 Arkell (1957, pp. L287-308), Schindewolf (1965, pp. 137-238) and Krimholz, Sasonov and Kamiseva-Elpatevskaja (1958, pp. 75-9) differ in their grouping of Middle and Upper Jurassic ammonites, but in the Bajocian distinction between Stephanocerataceae and Perisphinctaceae is clear. The classification of Bajocian stephanoceratids by Arkell (1957) is in need of revision, partly because of recent work on sexual dimorphism (Callomon 1963, Makowski 1963, Westermann 1964). Difficulties arise in deciding which dimorphs belong together and the procedure followed here mostly follows Callomon (1963, pp. 47-51) and Wester- mann (1964, pp. 40-4) in using macroconch/microconch subgenera (cf. Makowski 1963 and Cope 1967). For further discussion of the problem in general see Westermann (1969). Arkell (1957) grouped north-west European genera into Otoitidae (Mascke 1907), Stephanoceratidae (Neumayr 1875), and Sphaeroceratidae (Buckman 1920). However, the otoitid Normannites is probably the microconch of Stephanoceras, and the Sphaero- ceratidae and Otoitidae are similarly intertwined (Westermann 1964). 1 see no reason to recognize more than the one family Stephanoceratidae. Family stephanoceratidae Neumayr 1875 Includes. Stepheoceratidae Buckman 1898, Otoitidae Mascke 1907, Stemmatoceratidae Mascke 1907, Sphaeroceratidae Buckman 1920, Normannitinae Westermann 1954, Cadomitinae Westermann 1964. As now revised the Stephanoceratidae includes a great variety of forms, generally with sharp ribbing which passes over the venter without interruption, and is usually differentiated into primary and secondary ribs. At the point of furcation tubercles are frequently developed. The suture is complex (see also Westermann 1967). Dimorphism is striking and there may be considerable differences in size between the macroconchs and the microconchs. There are two main types of dimorphism, as described by Westermann (1964). In one type there is not only a difference in size between the macroconch and microconch, but whereas the macroconch has a collared and lipped aperture (e.g. Stephanoceras, Docidoceras and Stemmatoceras), the micro- conch aperture has lappets (e.g. Otoites, Normannites, and Polyplectites). In the second type of dimorphism the main difference between the macroconchs and microconchs is one of size, the aperture in both being collared and lipped (e.g. Sphaeroceras, Chon- droceras). The difference in type of dimorphism might be used as a basis for dividing the Stephanoceratidae into two subfamilies — Stephanoceratinae (including Westermann’s 1964 Otoitinae) and Sphaeroceratinae (cf. later Stephanocerataceae, e.g. Bathonian Tulitidae — Enay 1959). Subfamily stephanoceratinae Neumayr 1875 Includes. Stepheoceratidae Buckman 1898, Stemmatoceratidae Mascke 1907, Otoitidae Mascke 1907 (pars), Normannitinae Westermann 1954, Cadomitinae Westermann 1964. Description. As for family; strongly dimorphic with the macroconchs having collared and lipped aperture and much larger than the microconchs, which have lappets. N. MORTON: BAJOCIAN AMMONITES 273 Genus stephanoceras Waagen 1869 Macroconch subgenus Stephanoceras Waagen 1869 Type species. Ammonites Humphriesianus J. de C. Sowerby 1825, subsequent designation by Buckman 1898 (ICZN Opinion 324, see Arkell 1957, p. L289). Includes. Stepheoceras Buckman 1898 (obj.), Skirroceras Mascke 1907, Grahamites Kilian and Reboul 1909, Stephoceras Rollier 1911 (obj.), KciUistephamis, Rhytostephanus, Oecostephanus, Skolekostephanus Buckman 1921, Mollistephanus, ? Kumatostephanus Buckman 1922, Kreterostephanus, ? Phaulostephanus Buckman 1927, ? Gibbistephanus Buckman 1928, Dolichoecus, Bayleia, Freycinetia, Brodiaei, Romania Roche 1939. Discussion. The nomenclatural history of the genus Stephanoceras and the problem of the type species were discussed by Spath (1944). Many genera created by Buckman (1909-30), Mascke (1907) and others may be regarded as synonyms, see also Weisert (1932) and Spath (1936). French authors (e.g. Gillet 1937, Roman and Petouraud 1927, Fallot and Blanchet 1923) tended to use the generic name Cadomites (Munier-Chalmas 1892) in an extended sense to include the older Stephanoceras, while Roche (1939, pp. 167-217) also created a series of sections (subgenera) without any regard whatever for the older generic names of Buckman and Mascke which must take priority as senior synonyms (see also Spath 1944). Stephanoceras ( Stephanoceras ) mutabile (Quenstedt) Plate 40, figs. 5-10 1886 Ammonites Humphriesianus mutabilis Quenstedt, p. 537, pi. 66, fig. 5. 1932 Stephanoceras mutabile Quenstedt emend. Weisert; Weisert, pp. 153-5, pi. 17, fig. 6. 1938 Stephanoceras mutabile Quenstedt; Schmidtill and Krumbeck, pp. 340-1, pi. 11, fig. 3, pi. 14, figs. 6-7. 1939 Cadomites mutabilis Quenstedt; Roche, p. 201. Material. Nine specimens, mostly rather fragmentary — HMS 26353; HMS 26354; HMS 26355/1; HMS 26355/2; HMS 26356/1; HMS 26356/2; HMS 26356/3; HMS 26357. Dimensions. D. Wh. Wb. Ud. PL SI. Td. Tp. Tn. HMS 26353 79-0 24-4(31) c. 23-0(29) 32-8 (42) 11-4 (14) 22-0 (28) 6-2(8) 43-8 21* HMS 26354 55-0 19-5 (35) 21-9 (40) 8-1 (15) 14-5(30) 4-8 (9) 43-8 21* HMS 26355/2 — 25-5 17-2 — 12-2 22-0 c. 12 0 44-0 — HMS 26356/1 990 32-0 (32) 41-0 (41) 9-5 (10) c. 23-0 (23) 7-0(7) 32 1 33 HMS 26356/3 40-9 14-4 (35) 15-9(39) 6-5 (16) 12-0 (29) 3-0(7) 34-6 c. 28 Spec. no. HMS 26353: Tn. 27 24 22 20 19 Ud. 33-9 24-3 17-0 12-7 10-2 Spec. no. HMS 26354: Tn. 21 20 19 18 Ud. 21-9 16-6 13-0 9-4 274 PALAEONTOLOGY, VOLUME 14 Description. Evolute; small but prominent tubercles situated below the mid- whorl position; primary ribs strongly developed and sharp, slightly rursiradiate to rectiradiate, curved, bending forwards and fading only slightly towards the umbilical seam; secon- dary ribs not very strong but sharp, prorsiradiate, curving backwards on the venter; from each tubercle there are two or more, usually three, secondary ribs, with some- times an extra rib intercalated between the tubercles. The number of tubercles per whorl increases gradually with increasing size, from 18 at Ud. 9-4 mm in HMS 26354 to 0 10 20 30 40 50 60 Ud.(mm) text-fig. 2. Number of tubercles per whorl (Tn.) plotted against diameter of umbilicus (Ud.) for Stephanoceras ( Stephanoceras ) mutcibile (Quenstedt) (A), and S. ( S .) aff. brodiaei (Sowerby) (B). 33 at Ud. 41-0 mm in HMS 26356/1. This is also seen in the ontogenetic development of HMS 26353 and HMS 26354 (text-fig. 2 a). HMS 26353 is septate and has only a small part of the body chamber preserved; the other specimens do not show any sutures. HMS 26356/1 is pathological, showing local disturbance of the ornament for 1-5 cm just below the mid-whorl position. It is interesting to note that the injury did not cause permanent disfigurement of the shell, because the ornament returns to normal after less than one quarter of a whorl (cf. Guex 1967). Discussion. The specimens are very similar in style of ornament (including Tn.) to S. (S.) humphriesianum (Sow.), but differ in being more involute. The relative size of the umbilicus, and the style of the ornament are similar to S. ( S .) brodiaei (Sow.), but the Skye specimens have more numerous tubercles per whorl (Tn.). S. ( S .) plagium (Buck.), S. ( S .) kreter (Buck.) and S. ( S .) plicatum (Quenst.) are more evolute, while S. ( S .) umbilicum (Quenst.) appears to have the tubercles situated higher on the whorl sides. The specimens are closest to S. (S.) mutabile (Quenst.), although not all have quite as N. MORTON: BAJOCIAN AMMONITES 275 many tubercles per whorl (see text-fig. 2). Quenstedt (1886) figured only a ventral view (pi. 66, fig. 5), but a side view of the holotype was figured by Weisert (1932, pi. 17, fig. 6). In Swabia S. ( S .) mutabile (Quenst.) comes from the Humphriesianum-Schichten, the middle part of Dogger 8, that is Humphriesianum Zone and Subzone (Weisert 1932, p. 185; Hahn 1966, p. 29, pi. 4). In the Basses-Alpes it is recorded from the same level by Pavia and Sturani (1968, p. 312). Localities. Humphriesianum Zone; HMS 26353 from loose block of the Upper Sandstones, Rudha Sughar, Bearreraig; HMS 26354 and HMS 26355/1-2 from lower part of Upper Sandstones, shore just south of Rigg waterfall; HMS 26356/1-3 from 5 m. higher, just north of Rigg waterfall: HMS 26357 from lower part of Upper Sandstones at Leac Treshnish, Trotternish, Skye. Stephanoceras ( Stephanoceras ) aff. brodiaei (J. Sowerby) Plate 41, figs. 1-2 1832 Ammonites Brodiaei, J. Sowerby, p. 71, pi. 351. 1908 Ammonites Brodiaei J. Sowerby; Buckman and Secretary, pi. 5, fig. 1 ; pi. 7, fig. 3. 1923 Cadomites Brodiaei Sowerby; Fallot and Blanchet, p. 148, pi. 4, figs. 2-3; pi. 10, figs. 8-9; pi. 13, fig. 2. 1937 Cadomites Brodiaei Sowerby; Gillet, pp. 80-1, fig. 61. ? 1938 Stephanoceras ( Stepheoceras ) cf. brodiaei S. Buck.; Schmidtill and Krumbeck, p. 334, pi. 12, fig. 4. 1939 Cadomites brodiaei Sowerby; Roche, p. 196. 1951 Stephanoceras brodiaei Sowerby; Maubeuge, pp. 54-5, pi. 5, fig. 2, pi. 12, fig. 1. Material. Four specimens— HMS 15362; SMJ 57726; SMJ 57727; Call.J77. Dimensions. D. Wh. Wb. Ud. PI. SI. Td. Tp. Tn. HMS 15362 107-7 c. 29-0 (27) c. 48-0 (44) c. 52-0 (48) 19-0(18) 28-0 (26) 13-0(12) 51-9 22 Cal!.J77 110-0 35-6 (32) c. 47-5 (43) 48-5 (44) 18-5 (17) 39-0 (35) 13-0(12) 48-5 20* SMJ 57726 90-6 29-3 (32) 40-0 (44) 41-0(45) c. 15-0(17) 28-0 (31) 12-5 (14) 46-4 19 max. c. 104 SMJ 57727 107-0 34-7 (32) c . 47-0 (44) 48-3 (45) 24-0 (22) 35-0 (33) 13-0(12) 52-2 c. 21 Spec. no. Call.J77. Tn. 20 19 19 18 17 17 Ud. 48-5 34-5 26-7 200 15-7 11-5 Description. Evolute; very strong tubercles, rather blunt on outer whorls but large and pointed on inner whorls, and situated on mid-whorl position; primary ribs rather weak, straight and approximately rectiradiate, fading and almost disappearing before reaching umbilical seam ; secondary ribs not strongly developed, very slightly prorsiradiate and with slight backwards curvature on venter; from each tubercle there are usually three secondary ribs, with an extra secondary rib intercalated between the tubercles. The number of tubercles per whorl increases gradually from 17 at Ud. 1T5 mm to 20 at Ud. 48-5 mm in Call.J77, and 22 at Ud. 52-0 mm in HMS 15362 (text-fig. 2b). The specimens do not show sutures except Call.J77 which shows part of three sutures at one place. All four specimens show signs of having been eroded on one side. 276 PALAEONTOLOGY, VOLUME 14 Discussion. Of the species of the humphriesianum group, S. (S.) humphriesianum (Sower- by), S. (-S’.) mutabile (Quenst.), S'. (S'.) umbilicum (Quenst.), and S. ( S .) kreter (Buck.) have more tubercles per whorl than these specimens. S. (S.) brodiaei (Sow.), S'. (S.) plication (Quenst.) and S. (S.) plagium (Buck.) have approximately the same number of tubercles per whorl, but plagium is too evolute, and plicatum has the tubercles situated too low on the whorl sides. The specimens are most similar to S. (S’.) brodiaei (Sowerby), but differ in being slightly more evolute (Ud. 44-48% of D. compared with 39% in the holotype figured by Buckman and Secretary 1909), and in having the tubercles situated slightly higher on the whorl sides (Tp. = 46-52 compared with 43 in the holotype). The two specimens from the Sedgwick Museum were identified as Stephanoceras aff. brodiaei (J. Sow.) by W. J. Arkell in 1951. The precise locality and horizon of the holotype of S. ( S .) brodiaei (J. Sowerby) is uncertain, but Roche (1939, p. 196) suggested the lower part of the Humphriesianum Zone. Locality. Humphriesianum Zone ; loose blocks of the Upper Sandstones, Rudha Sughar, Bearreraig. Three of the specimens have a purple colour on parts of the surface, the fourth (HMS 15362) is not so strongly coloured. Possibly they come from one particular bed in the Upper Sandstones. Stephanoceras ( Stephanoceras ) nodosum (Quenstedt) Plates 42-45 1858 Ammonites Humphriesianus nodosus Quenstedt, p. 399, pi. 54, fig. 4. 1886 Ammonites Humphriesianus nodosus Quenstedt, p. 532, pi. 65, fig. 17. 1932 Stephanoceras nodosum Quenstedt emend. Weisert; Weisert, pp. 136-8, pi. 15, figs. 1-2. 1938 Stephanoceras nodosum Quenstedt; Schmidtill and Krumbeck, pp. 327-8, pi. 14, fig. 5. 1939 Cadomites nodosus Quenstedt; Roche, p. 187, fig. 5. 1951 Stephanoceras nodosum and aff. nodosum Quenstedt; Maubeuge, pp. 57-60, pi. 6, figs. 5-6; pi. 10, fig. 6; pi. 11, fig. 3. Material. Fourteen specimens, some fragmentary — HMS 15359/1,3; HMS 15360/1-2; HMS 26360/1-2; HMS 26361/1-2; HMS 26362/1-3; SMJ 57728; SMJ 57735; Call.J473; Call.J474. Dimensions. D. Wh. Wb. Ud. PL SI. Td. Tp. Tn. HMS 15359/1 229 59-0 (26) 71-0 (31) 122-0 (53) 29-0(13) 61-0 (27) 23 0 (10) 43-9 26* HMS 15360/1 — 65-8 — — 33-0 61-0 23-0 39-4 — HMS 15360/2 — 65-2 51-0 — 33-0 57-0 22-0 38-7 — Call.J473 c. 164 44-0 (27) ■ — c. 79-0 (48) 21-0(13) 39-0 (24) 14-0 (9) 41-5 c. 25 HMS 26360/1 c. 263 79-0 (30) 85-0 (32) 123-0 (47) 39-0(15) 78-0 (30) 23-0 (9) 31-5 c. 24* HMS 26361/1 c. 192 43-0 (22) c. 32-0(17) c. 1110 (58) 28-0 (19) 37-0 (19) 16-0 (8) 47-6 27 HMS 26362/1 192 48-0 (25) 56-0 (29) 103-0 (54) 29-0(15) 46-0 (24) 14-0 (7) 44-0 29* HMS 26362/2 235 57-0 (24) — 127-0 (54) 25-0(11) c. 45-0(19) 18-0 (8) 34-5 31* HMS 26362/3 173 49-6 (29) 40-2 (23) 86-7 (50) 22-0 (13) 41 0 (24) 17-0 (10) 40-5 25 SMJ 57728 115 31-6(27) — 56-4 (49) 15-0 (13) 34-0 (30) 11-0 (10) 38-7 c. 26 SMJ 57735 c. 275 54-0 (20) c. 60-0 (22) c. 160 (58) 32-0 (12) 54-0 (20) 25-0 (9) 41-8 c. 32 EXPLANATION OF PLATE 41 Figs. 1, 2, Stephanoceras ( Stephanoceras ) aff. brodiaei (J. Sowerby); Call.J77, Humphriesianum Zone, loose block of Upper Sandstones, Rudha Sughar, Bearreraig, Trotternish, Skye. X 1. 3, Stephano- ceras ( Stephanoceras ) aff. nodosum (Quenstedt) and aff. macrum (Quenstedt); HMS 15359/2, Humphriesianum Zone, basal bed of Upper Sandstones, Torvaig, Trotternish, Skye. x0-72. Palaeontology, Vol. 14 PLATE 41 MORTON, Bajocian ammonites N. MORTON: BAJOCIAN AMMONITES 277 Spec. no. HMS 15359/1: Tn. 26 23 22 22 21 19 18 17 16 Ud. 130 98 72 54 38 29 20 14 12 Spec. no. HMS 26360/1 : Tn. c. 24 — 23 22 21 21 19 Ud. 123 — 35 25 18 13 c. 10 Spec. no. HMS 26362/1 : Tn. 29 28 27 25 Ud. 103 86 50-4 36-6 Spec. no. HMS 26362/2: Tn. 31 29 25 24 22 19 17 16 Ud. 126 92-2 68 48 35-3 24-5 17-2 130 Description. Evolute ; large strong tubercles situated just below the mid- whorl position ; primary ribs moderately strong, rursiradiate and slightly curved, fading towards umbilical seam; secondary ribs also moderately strong, very slightly prorsiradiate or rectiradiate, practically straight, and uninterrupted on venter; from each tubercle there are normally three secondary ribs, sometimes with an extra secondary rib inter- calated between the tubercles. The number of tubercles per whorl increases gradually with increasing size (text-fig. 3a), for example, from 16 at Ud. 13-0 mm to 31 at Ud. 126 mm in HMS 26362/2, from 16 at Ud. 12-0 mm to 26 at Ud. 130 mm in HMS 15359/1. Three of the specimens show sutures: HMS 26360/1 has half a whorl of body chamber preserved; HMS 15359/1 has approximately two-thirds of a whorl of body chamber and begins to show an increase in the relative umbilical diameter, but is also incomplete ; HMS 26362/1 is complete, having the peristome partially preserved, and shows just over three-quarters of a whorl of body chamber. There is an increase in the relative umbilical diameter in just over the last half-whorl, and modification of the ornament in the last eighth-whorl associated with which there is a slight constriction followed by an expansion of the whorl, then a second constriction and a further expansion to the peristome. Discussion. The style of the ornament of these specimens is typical of the macrum group. The typical species, however, S. (S'.) macrum (Quenstedt), S. (S.) freycineti (Bayle), and S. (S.) leptogyrale (Buckman) are more evolute and have more numerous tubercles per whorl. The specimens are closest to S. (S.) nodosum (Quenstedt), which has a relatively narrower umbilicus than the other species but similar style of ornament. There are specimens intermediate between nodosum and macrum (see below). The holotype of S. (S.) nodosum (Quenstedt) come from the Dogger 8 of Swabia (Quenstedt 1886, p. 532), while Weisert (1932, p. 185) indicated lower and middle Dogger (Giganteus-Thone and untere Humphriesi-Schichten). It was interpreted as coming from the Sauzei Subzone by Roche (1939, p. 187), but Hahn (1966) includes both beds in the Humphriesianum Zone. It would appear that S. (S.) nodosum (Quenst.) may be younger than S. (S.) macrum (Quenst.) (cf. Weisert 1932, p. 185), which is recorded mainly from the Sauzei Subzone (e.g. Westermann 1967, p. 105). Pavia and Sturani (1968, pp. 311-12) record S. ( S .) nodosum (Quenst.) from the Sauzei Subzone and lower part of the Humphriesianum Zone in the Basses-Alpes. 278 PALAEONTOLOGY, VOLUME 14 Localities. Humphriesianum Zone; (1) HMS 15359/1, 3 from the basal bed of the Upper Sandstones, Torvaig; (2) HMS 15360/1-2, HMS 26360/1-2, HMS 26361/1-2, SMJ 57728, SMJ 57735, and Call. J473-4 from loose blocks of the Upper Sandstones, Rudha Sughar, Bearreraig; (3) HMS 26362/1-3 from the lower part of the Upper Sandstones, shore just south of Rigg waterfall. All localities are in Trotternish, Skye. text-fig. 3. Number of tubercles per whorl (Tn.) plotted against diameter of umbilicus (Ud.) for Stephanoceras ( Stephanoceras ) nodosum (Quenstedt) and Stephanoceras ( Normannites ) ? orbignyi (Buckman) (A), and S. (S.) aff. nodosum and aff. macrum (Quenstedt) (B). Data from figured speci- mens of S. ( S .) nodosum and S. ( S .) macrum are also shown for comparison. Stephanoceras ( Stephanoceras ) aff. nodosum (Quenstedt) and aff. macrum (Quenstedt) Plate 41, fig. 3 aff. 1886 Ammonites Humphriesianus macer Quenstedt, p. 528, pi. 65, fig. 11 (non fig. 10). Ammonites Humphriesianus nodosus Quenstedt, p. 532, pi. 65, fig. 17.’ EXPLANATION OF PLATE 42 Fig. 1. Stephanoceras ( Stephanoceras ) nodosum (Quenstedt); FIMS 15359/1, Humphriesianum Zone, basal bed of Upper Sandstones, Torvaig, Trotternish, Skye, x 0-82. EXPLANATION OF PLATE 43 Fig. 1. Stephanoceras ( Stephanoceras ) nodosum (Quenstedt); HMS 26362/1, Humphriesianum Zone, lower part of Upper Sandstones, shore just south of Rigg waterfall, Trotternish, Skye, x 0-88. EXPLANATION OF PLATE 44 Fig. 1. Stephanoceras ( Stephanoceras ) nodosum (Quenstedt); HMS 15359/1, ventral view of Plate 42, fig. 1. X TO. 2. Stephanoceras ( Stephanoceras ) nodosum (Quenstedt); HMS 26362/1, ventral view of Plate 43, fig. 1 . x 1 -0. Palaeontology, Vol. 14 PLATE 42 MORTON, Bajocian ammonites ■n Palaeontology, Vol. 14 PLATE 43 MORTON, Bajocian ammonites Palaeontology, Vol. 14 PLATE 44 MORTON, Bajocian ammonites N. MORTON: BAJOCIAN AMMONITES 279 Material. Two specimens — HMS 15359/2; HMS 26363. Dimensions. D. Wh. Wb. Ud. PI. SI. Td. Tp. Tn. HMS 15359/2 c. , 195 48 1 (25) 53 0 (27) c. 118 (61) 240 (12) 430 (22) 120 (6) 38-3 c. 40* HMS 26363 244 52 0 (21) c. 65 0(27) c. 148 (61) 300 (12) 530 (22) 190 (8) 38 9 35* Spec. no. HMS 15359/2: Tn. c . 40 c. 29 26 24 22 20 18 17 Ud. c. 118 92 •5 66-2 500 34-4 250 18 •7 14 •4 Spec. no. HMS 26363: Tn. 35 33 Ud. c. 148 124 Discussion. The two specimens are very similar to the specimens described above as S. (S.) nodosum (Quenstedt) especially in style of ornament, for example the number of tubercles per whorl (text-fig. 3b). They differ only in the relative size of the umbilicus, which is just over 60% of the diameter compared with 48-58%. Previously figured specimens of nodosum have relative Ud. 51-6 (holotype, Quenstedt 1886, pi. 65, fig. 17) and 52-4 (Weisert 1932, p. 15, fig. 1), while specimens of macrum have relative Ud. 61-7 (Weisert 1932, p. 15, fig. 3), 62 T (Weisert 1932, pi. 15, fig. 5), and 66 (Buckman 1921, pi. 248). There is, however, obviously every gradation between these two species as indicated by these specimens and the specimens described above under S. ( S .) nodosum (Quenstedt). (See also Weisert 1932, p. 138 ) Localities. Humphriesianum Zone; HMS 15359/2 from basal bed of Upper Sandstones, Torvaig; HMS 26363 from loose block of Upper Sandstones, Rudha Sughar, Bearreraig, Trotternish, Skye. Stephanocercts ( Stephanocevas ) aff. triplex Weisert Plate 46, figs. 1, 2; Plate 47, figs. 1, 2 1932 Stephanoceras triplex Mascke emend. Weisert; Weisert, pp. 152-3, pi. 16, fig. 1. 1939 Cadomites triplex Mascke; Roche, p. 195. Material. Six specimens, rather fragmentary — HMS 15358/2; HMS 26364; HMS 26365; HMS 26366; HMS 26367 ; SMJ 57736. Dimensions. D. Wh. Wb. Ud. PL SI. Td. Tp. Tn. HMS 26365 c. 234 59 0 (25) 28-4 (12) c. 130 (56) 22 0 (9) 50-0(21) 13-0 (6) 27-9 c. 45 SMJ 57736 c. 228 61-0 (27) c. 38 0(17) c. 113 (50) 25-0(11) 57-0 (25) 16 0 (7) 28-8 c. 31 Description. Evolute; tubercles situated well below the mid-whorl position, small and not very prominent compared with the ribbing; primary ribs very strong, rursiradiate, slightly curved, especially near umbilical seam; secondary ribs very strong, slightly prorsiradiate to rectiradiate with slight backwards curvature over the venter; from each tubercle there are generally two secondary ribs, sometimes three and rarely one. 280 PALAEONTOLOGY, VOLUME 14 with one extra secondary rib intercalated between the tubercles. The number of tubercles per whorl is c. 31 at Ud. c. 113 mm in SMJ 57736 and c. 45 at Ud. c. 130 mm in HMS 26365. It is rather difficult to compare these approximate figures with those for the much smaller specimen figured by Weisert (text-fig. 4a). None of the specimens shows sutures. text-fig. 4. Number of tubercles per whorl (Tn.) plotted against diameter of umbilicus (Ud.) for Stephanoceras ( Stephanoceras ) aff. triplex Weisert (A), and A. (5.) pyritosum (Quenstedt) (B). Discussion. The strong ribbing associated with the comparatively insignificant tubercles is typical of species like zieteni, and the specimens may be related to this species. S. (S.) zieteni (Quenst.) and S. ( S .) kalus (Buck.) are both more evolute and have more numerous tubercles per whorl, while S. ( S .) subzieteni Schmidtill and Krumbeck is more evolute. The specimens are most similar to S. (S.) triplex Weisert, but they differ from this and the other species in having the tubercles situated relatively lower on the whorl sides. This, however, may be an apparent effect due to partial crushing. According to Weisert (1932, p. 185) the species S. (5.) triplex comes from the upper Humphriesi-Schichten, middle Dogger 8 of Swabia, i.e. Humphriesianum Zone. Localities. Humphriesianum Zone; HMS 15358/2 from approx. 30 m. above base of Upper Sand- stones, pipeline cutting at Bearreraig; HMS 26364 and SMJ 57736 from loose blocks of the Upper Sandstones, Rudha Sughar, Bearreraig; HMS 26366, HMS 26365, and HMS 26367 from the lower part of Upper Sandstones, shore just north of Rigg waterfall, Trotternish, Skye. EXPLANATION OF PLATE 45 Fig. 1. Stephanoceras ( Stephanoceras ) nodosum (Quenstedt); HMS 26362/2, Humphriesianum Zone, lower part of Upper Sandstones, shore just south of Rigg waterfall, Trotternish, Skye, x 0-79. Palaeontology, Vol. 14 PLATE 45 MORTON, Bajocian ammonites N. MORTON: BAJOCIAN AMMONITES 281 Stephanoceras ( Stephanoceras ) pyritosum (Quenstedt) Plate 47, figs. 3, 4; Plates 48, 49; Plate 50, figs. 1, 2 1886 Ammonites Humphriesianus pyritosus Quenstedt, pp. 536-7, pi. 66, fig. 4. 1934 Stepheoceras (Norma unites) pyritosum Quenstedt; Kakhadze, p. 134, pi. 5, fig. 1. 71938 Stephanoceras aff. pyritosum Quenstedt; Schmidtill and Krumbeck, p. 337, pi. 14, fig. 10. 1951 Stephanoceras pyritosum Quenstedt; Maubeuge, p. 56, pi. 11, fig. 2. Material. Five specimens— HMS 15357; SMJ 57729; SMJ 57730; SMJ 57733; GSEV 1559c; Call.J472. Dimensions. D. Wh. Wb. Ud. PL Si. Td. Tp. Tn. SMJ 57729 154 47-0(31) — 68-0(44) [14-0 (9) c. 45 0(9) 8-0(5) 28-6 37* SMJ 57730 124 41-5(33) 22-3(18) 51-6(42) 4-0(11) 38-0(31) 5-5(4) 26-8 44 SMJ 57733 248 66-0(27) 70-0(28) 127-0(51) 35-0(14) 70-0(28) 13-0(5) 30-8 43* GSEV 1559c 93 0 32-4(35) 25-8(28) 39-7(43) 12-0(13) c. 29-0(31) 6-0(6) 29-0 31 Call.J472 74-3 29-7(40) 23-0(31) 27-3 (37) 13-5(18) 26-0(35) 5-0(7) 39-3 32 Spec. no. SMJ 57729: Tn. 37 35 Ud. 68 0 51-7 Spec. no. SMJ 57733: Tn. 43 39 35 31 27 Ud. 127 99 67 48 33 Description. Evolute; small, not very prominent tubercles situated well below the mid- whorl position; primary ribs strong, becoming sharp in some, slightly rursiradiate, with pronounced forward curvature towards umbilical seam, fading only at umbilical shoulder and usually almost reaching umbilical seam; secondary ribs close, moderately strong, sharp, slightly prorsiradiate but curving backwards to become approximately rectiradiate on venter; from each tubercle there are two, sometimes three secondary ribs, with one extra secondary rib intercalated between the tubercles. The number of tubercles per whorl increases from 27 at Ud. 33 mm to 43 at Ud. 127 mm in SMJ 57733, and this and the other specimens are comparable with the type (Quenstedt, pi. 66, fig. 4), with the exception of SMJ 57730 which, although the style of the ornament is similar, has a relatively greater number of tubercles per whorl than the other specimens (text-fig. 4b). Only SMJ 57733 shows sutures and it has just over one whorl of body chamber. The peristome is partially preserved and there is an increase in the relative diameter of the umbilicus, but no modification of the ornament (cf. S. (S'.) nodosum described above). Discussion. The style of the ornament of the specimens is typical of species similar to S. (S.) scalare. A number of closely ribbed species of Stephanoceras have been described, particularly by Schmidtill and Krumbeck (1938) from Franconia, S. Germany, and many of these are probably synonyms. Most of these species are more finely ribbed than the Skye specimens. S. ( S .) scalare (Mascke figd. Weisert) and S. (S.) rhytum (Buckman) C 7998 u 282 PALAEONTOLOGY, VOLUME 14 are similar in the style of the ornamentation but differ in having more numerous tubercles per whorl. The same appears to be the case for the fragment figured by Quen- stedt as A. H. plicatissimum, although the specimen figured by Weisert (1932, pi. 16, fig. 5) under the same name may be more similar. The specimens from Skye are closest to S. (S'.) pyritosum (Quenstedt), a name which appears to have been neglected by most authors. The holotype of S. (S.) pyritosum (Quenstedt) comes from Dogger 8 of Swabia (Quenstedt 1886, p. 536), presumably from the Humphriesianum Zone. Localities. Humphriesianum Zone; HMS 15357 from approx. 30 m above the base of the Upper Sand- stones, pipeline cutting at Bearreraig; SMJ 57729-33 and Call.J472 from loose blocks of the Upper Sandstones, Rudha Sughar, Bearreraig; GSEV 15559c from the lower part of the Upper Sandstones, shore just south of Rigg waterfall, Trotternish, Skye. Microconch subgenus Nonnannites Munier-Chalmas 1892 Type species. Nonnannites orbignyi Buckman 1908 (ICZN Opinion 309, see Arkell 1957, p. L289). Includes. Epalxites Mascke 1907, Masckeites Buckman 1920, Parailites, Gerzenites, Germanites Wester- mann 1954, Germanoides Westermann 1956. The status of Itinsaites (McLearn 1927), with synonyms Kanastephanus (McLearn 1929) and Platystomites (Westermann 1954) is less certain. It was regarded by Arkell (1957, p. L289) as a synonym of Nonnannites, but by Westermann (1964, p. 68) as the micro- conch of Teioceras. Discussion. Apart from the differences in size and in the nature of the aperture, Nonnan- nites is very similar to Stephanoceras, but at this stage it is difficult to suggest any pairs of species. The number of stephanoceratid microconchs which have been found in Skye is remarkably small compared with the number of macroconchs. This may be partly due to collection failure, but is probably also a reflection of the original composition of the fauna. This problem of differing macroconch: microconch ratios has been discussed by Makowski (1963) and Callomon (1963). Stephanoceras ( Nonnannites ) ? orbignyi (S. Buckman) Plate 51, figs. 1, 2 1845 Ammonites Braikenridgii d’Orbigny, pi. 135 (non Sowerby). 1927 Normannites orbignyi S. Buckman, pi. 734. 1939 Nonnannites orbignyi Buckman; Roche, pp. 219-20, pi. 1, figs. 3-4. 1954 Normannites ( Normannites ) orbignyi S. Buckman + subspp. ; Westermann, pp. 135-52, pi. 5, figs. 3-4; pi. 6, figs. 1, 3-5; pi. 7, figs. 1-5; pi. 8, fig. 1. Material. Two specimens and four fragments — HMS 26370/1-2; HMS 26371 ; Call. J469; Call.J470; Call.J471. Dimensions. D. Wh. Wb. Ud. Pi. SI. Td. Tb. Tn. Call.J471 50-5 16-8(33) 22-3 (44) 18-1(36) 8-2(16) 17-5(35) 6-0(12) 46-1 c. 18 CalI.J470 20- 1 6-9(34) 12-7(63) 8-3(41) 3-4(17) 7-0(35) 2-6(13) 42-9 c. 20 N. MORTON: BAJOCIAN AMMONITES 283 Description. Evolute; strong prominent tubercles situated below the mid-whorl position; primary ribs fairly strongly developed, approximately rectiradiate, only very slightly curved, fading towards umbilical seam; secondary ribs strongly developed, sharp, approximately rectiradiate and straight on venter; from each tubercle there are usually three secondary ribs with one extra secondary rib sometimes intercalated between the tubercles. Call.J471 has only the body chamber and last septum preserved, and also has large lappets. There are between two-thirds and three-quarters of a whorl of body chamber (excluding lappets), and there is no modification of the ornament near the aperture. Discussion. The style of the ornament, particularly the strong tubercles and secondary ribbing, is very similar to that of S. (N.) orbignyi (Buckman), but the specimens are not sufficiently well preserved to allow a definite identification with that species. Comparison with the macroconch species from Skye described above shows the specimens to be very similar to S. (S.) nodosum (Quenstedt), not only in general style of ornament but also in number of tubercles per whorl at comparable sizes (expressed as Ud.) (text-fig. 3a). S. (N.) orbignyi (Buckman) comes from the Humphriesianum Zone ( Epalxites hemera) in Dorset (Buckman 1927). Localities. Humphriesianum Zone; Call.J469-71 from loose blocks of the Upper Sandstones, Rudha Sughar, Bearreraig, one specimen showing a distinctive purplish colour (see p. 76); HMS 26370/1-2 from lower part of Upper Sandstones, shore north of Rigg waterfall; HMS 26371 from lower part of Upper Sandstones, Leac Treshnish, Trotternish, Skye. Stephanoceras ( Normannites ) Idensum (S. Buckman) Plate 51, fig. 3 1920 Masckeites densus S. Buckman, pi. 152. 1954 Masckeites densus Buckman; Westermann, pp. 332-4. Material. Two poorly preserved specimens, one fragment, mostly at least partly distorted — HMS 26372/ 1-2; HMS 26373. Dimensions. D. Wh. Wb. Ud. PI. SI. Td. Tp. Tn. HMS 26372/1 max. 56-5 20-9 (37) 314 (56) 20-4 (36) 6-3 (11) c. 18-6(35) c. 4-0(7) — c. 23 min. HMS 267373 22-8 26-5 91 (40) 1 1 0(42) — 8-7(38) 100(38) 3-2(12) c. 8-0(30) c. 2 0 (8) 34-5 30 Description. Evolute; tubercles weakly developed, situated well below mid-whorl position (allowance being made for distortion) ; primary ribs prorsiradiate, curving to become approximately rectiradiate towards umbilical margin and also fading slightly in that direction ; secondary ribs close and sharp, also not strongly developed, approxi- mately rectiradiate and only very slightly curved on venter; from each tubercle there 284 PALAEONTOLOGY, VOLUME 14 are either two or three secondary ribs, often with an extra secondary rib intercalated between the tubercles. None of the specimens is complete or shows sutures. Discussion. The style of the ornament in the specimens is much finer than in the previous species, and is very similar to that of Buckman’s Type Ammonites species Masckeites densus. However, the specimens are not sufficiently well preserved to allow definite identification with that species. When compared with the macroconch species from Skye the specimens are perhaps most similar to S. (S.) pyritosum (Quenstedt). The holotype of S. (TV.) den sum (Buckman) was figured by Buckman (1920) as from ‘Bajocian post-sauzei / Masckeites /’ , i.e. Humphriesianum Zone, of Dorset. Locality. Humphriesianum Zone; lower part of Upper Sandstones, shore just south of Rigg waterfall, Trotternish, Skye. Genus teloceras Mascke 1907 Macroconch subgenus Teloceras Mascke 1907 Type species. Ammonites Blagdeni J. Sowerby 1818, original designation by Mascke (1907, p. 23). Includes. Blagdenia Roche 1939 (objective synonym). Discussion. In Skye, only one specimen of Teloceras has been found, at Bearreraig, but this may be due to the inaccessibility of the outcrops rather than to any other factors. According to Westermann (1964, p. 68) the microconch of Teloceras is Itinsaites (McLearn 1927), with synonyms Kanastephanus (McLearn 1929) and Platystomites (Westermann 1954). Teloceras ( Teloceras ) blagdeni (J. Sowerby) Plate 50, fig. 3 1818 Ammonites Blagdeni J. Sowerby, p. 231, pi. 201. 1908 Ammonites Blagdeni J. Sowerby; Buckman and Secretary, pi. 2; pi. 3, fig. 1. 1932 Teloceras Blagdeni Sowerby sp. emend. Weisert; Weisert, pp. 168-72, pi. 18, fig. 2. 1937 Cadomites Blagdeni Sowerby (non d'Orbigny); Gillet, p. 83, pi. 5, figs. 9-9 a. 1939 Cadomites Blagdeni Sowerby; Roche, pp. 213-14. 1943 Cadomites Blagdeni Sowerby; Roche, pp. 17-18. 1957 Teloceras blagdeni (Sowerby); Arkell, fig. 342: 5 a-b. Material. One highly distorted specimen — HMS 26374. Dimensions. D. Wh. Wb. Ud. PI. SI. Td. Tn. max. HMS 26374 min. c. 250 c. 70 c. 70 (28) 23 (33) c. 150(60) 135(193) 125 (50) 33 (47) 35(14) c. 85 (34) 12(5) c. 13/| wh. The relative Wh. and Ud. closely approximate the original dimensions. Description. Evolute; whorl section trapezohedral, width much greater than height; large tubercles situated at the angle between the whorl sides and the broad almost flat N. MORTON: BAJOCIAN AMMONITES 285 venter; primary ribs broad and blunt, slightly rursiradiate, straight, fading towards umbilical seam; from each tubercle there are normally three secondary ribs which curve backwards slightly across the venter. Discussion. In a comparison of the specimen with described species allowance must be made for the distortion, however, in the relative size of the umbilicus, style of ornamen- tation, and number of tubercles per whorl the specimen is very similar to T. ( T .) blagdeni (J. Sowerby). This species is typical of the upper part of the Humphriesianum Zone, the Blagdeni Subzone (e.g. Westermann 1967, pp. 149-50). Locality. Humphriesianum Zone, Blagdeni Subzone; 34 m above base of Upper Sandstones, pipe- line cutting, Bearreraig, Trotternish, Skye. Subfamily sphaeroceratinae Buckman 1920 Mainly involute sphaerocones, some with occluded umbilicus, but with the last whorl contracted so that the umbilicus becomes more open. In some the coiling is elliptical. The Sphaeroceratinae are similar to the Stephanoceratinae in having generally sharp ribbing differentiated into primary and secondary ribs which pass over the venter, but rarely are tubercles developed at the point of furcation. There is marked dimor- phism, but the microconchs differ from the macroconchs mainly in size, both having a collared and lipped aperture. The arrangement of the genera in the Sphaeroceratinae by Arkell (1957) was modified by Westermann (1964) to take account of sexual dimorphism. In the taxonomic arrange- ment of Westermann the dimorphism varies from being infraspecific to subgeneric distinction of the dimorphs. Genus chondroceras Mascke 1907 Type species. Ammonites gervi/lii J. Sowerby 1817, original designation by Mascke 1907, p. 24. Includes. Defonticeras, Saxitoniceras McLearn 1927, Schmidtoceras Westermann 19566, ? Praetulites Westermann 1956u. Discussion. The most extensive discussion of Chondroceras is by Westermann (19566), which was published after the Treatise (Arkell 1957) was in press (see also Arkell \951a). Westermann (19566 and 1964) recognized as subgenera of Chondroceras Chondroceras (s.s.), and also Defonticeras and Saxitoniceras created by McLearn (1927) for Canadian species, and two new subgenera Schmidtoceras and Praetulites (Westermann 1956u). With the possible exception of Praetulites the differences between these subgenera and Chondroceras (s.s.) are not sufficient to justify their separation (see also Arkell 1957; Imlay 1964, 1967). According to Westermann (1964, p. 54) dimorphism within the genus Chondroceras can be regarded, from the taxonomic point of view, as infraspecific. 286 PALAEONTOLOGY, VOLUME 14 Chondroceras evolvescens (Waagen) Plate 51, figs. 4-7 1867 Ammonites evolvescens, Waagen, p. 604, pi. 1, fig. 7. 1923 Chondroceras wrighti Buckman, pi. 415. 19566 Chondroceras ( Chondroceras ) evolvescens (Waagen); Westermann, pp. 55-8, pi. 1, figs. 7-8; pi. 2, figs. 1-2. 19566 Chondroceras ( Chondroceras ) wrighti Buckman with subspp. wrighti and minor n. subspp. ; Westermann, pp. 58-61, pi. 2, figs. 3-4; pi. 3, figs. 1-3. 1964 Chondroceras ( Chondroceras ) evolvescens (Waagen); Westermann, p. 54. Material. Two specimens — HMS 26375 and GSEV 1539c — and one doubtful specimen — HMS 15363 Dimensions. D. Wh. Wh. Ud. PL SI. Pd. Pn. HMS 26375 400 17-7(44) 17-4(44) 10-7(27) 7-5(19) 16-2(41) 2-6(7) 30/1 Wh. GSEV 1539c 33-2 c. 13-8(42) — 9-3 (28) — — — 16/J Wh. HMS 15363 29-6 12-0(41) — 8-1 (28) — — — — Description. Involute; body chamber contracts slightly near the aperture so that there is a slight increase in the relative size of the umbilicus; umbilical edge fairly sharp, becoming vertical; venter broad and rounded; ribbing moderately sharp, close (30 primary ribs in the last whorl); primary ribs prorsiradiate, curving forwards slightly towards middle of whorl sides, fading towards umbilical seam, mostly trifurcate but some bifurcate; secondary ribs close, not strongly developed, prorsiradiate but curving backwards slightly across the venter; body chamber approximately one whorl, aperture (partially visible on HMS 26375) contracted and collared. Discussion. In the relative size of the umbilicus and the style of the ribbing the specimens are similar to C. gerviUii (Sowerby), C. evolvescens (Waagen) and C. wrighti Buckman. EXPLANATION OF PLATE 46 Figs. 1, 2. Stephanoceras ( Stephanoceras ) aff. triplex Weisert; SMJ 57736, Humphriesianum Zone, loose block of Upper Sandstones, Rudha Sughar, Trotternish, Skye, x 1-0. All figures natural size. EXPLANATION OF PLATE 47 Figs. 1, 2. Stephanoceras ( Stephanoceras ) aff. triplex Weisert; HMS 26365, Humphriesianum Zone, lower part of Upper Sandstones, shore just north of Rigg waterfall, Trotternish, Skye. 3, 4. Stephanoceras ( Stephanoceras ) pyritosum (Quenstedt); Call.J472, Humphriesianum Zone, loose block of Upper Sandstones, Rudha Sughar, Bearreraig, Trotternish, Skye. EXPLANATION OF PLATE 48 Fig. 1. Stephanoceras ( Stephanoceras ) pyritosum (Quenstedt); SMJ 57733, Humphriesianum Zone, loose block of Upper Sandstones, Rudha Sughar, Bearreraig, Trotternish, Skye, x 0-82. EXPLANATION OF PLATE 49 Fig. 1. Stephanoceras ( Stephanoceras ) pyritosum (Quenstedt); SMJ 57729, Humphriesianum Zone, loose block of Upper Sandstones, Rudha Sughar, Bearreraig, Trotternish, Skye, x TO. Palaeontology, Vol. 14 PLATE 46 MORTON, Bajocian ammonites Palaeontology, Vol. 14 PLATE 47 2 MORTON, Bajocian ammonites Palaeontology, Vol. 14 PLATE 48 MORTON, Bajocian ammonites •■•'A Palaeontology, Vol. 14 PLATE 49 MORTON, Bajocian ammonites N. MORTON: BAJOCIAN AMMONITES 287 Other species differ in one or both of these characters. C. gervillii (Sowerby), however, has slightly closer ribbing (34-40 in the last whorl compared with 30 in HMS 26375). C. wrighti Buckman is very similar to C. evolvescens (Waagen) and is almost certainly a junior synonym (see also Westermann 1964, p. 54), and the specimens from Skye compare very closely with C. evolvescens (Waagen) (holotype figured by Westermann 19566, pi. 1, figs. 1 a-c). The species comes from the Humphriesianum Zone (Buckman 1923; Pavia and Sturani 1968, p. 312; Westermann 19566, 1964). Localities. Humphriesianum Zone; HMS 26375 and GSEV 1539 2 W' > 2 '\W — . _ M 2 CO A' Z w -- z ^ RIES SMITHSONIAN INSTITUTION NOIlfUllSNI _ NVINOSHillNS S3l0VH8n LIBRARIES SMITHSONI co — co -, \ c o — to LI1SNI NVIN0SH1II/MS SSIdVdSIl LIBRARIES SMITHSONIAN INSTITUTION NOIlfUllSNI NVINOSHU RIES SMITHSONIAN INSTITUTION NOIlfUllSNI NVINOSHIIWS SBIBVdail LIBRARIES SMITHSON 2 ,v CO 2 < 2 . < 2 CO LI1SNI NVINOSHU INS S3iavaail LIBRARIES SMITHSONIAN INSTITUTION NOIlfUllSNI NVINOSH1I co ~ co r; co n a: fy'y. ^ O O 5 0 \R I E S2 SMITHSON IAN-1 1 NSTITUTION" NOIlfUllSNI “‘nVINOSHIIWS S3iyvaailLIBRARI ES^ SMITHSON ^ i I 1 » ||% I £ co £ co £ co £ LI1SNI NVINOSH1IIAIS S 3 I M V U a II LIBRARIES SMITHSONIAN INSTITUTION NOIlfUllSNI NVINOSHU 2 ^O ^ 2 CO z CO 2 o X M/m/- 9 NW% o x W44w. - co J&JP?: co vl|. co 2 ^towosv*^' CO 2 CO 2 co 2 CO ^ R I E S SMITHSONIAN INSTITUTION NOIiniliSNI_NVINOSHlllNS S3IHVaai1 LIBRARIES SMITHSON (/) c/) _ — ^ \ co _______ (/) 1I1SNI NVINOSHU WS SBIdVaail LIBRARIES SMITHSONIAN INSTITUTION NOIlfUllSNI NVINOSHU Z r- 2 r- Z * 73 > > XI is2z rn ^ co XQims^X rn x; m co \ £ co £ co \RIES SMITHSONIAN INSTITUTION NOIlfUllSNI NVIN0SH1IINS S3IHVH8n LIBRARIES SMITHSON . co ^ co 2 co z w — . „A 2 .< 2 . < % -C 2 £ ..A./ -A* *2 Xc X /P^ o X . O co N co co x O ■S/'/X £ > n^ju^£/ 2 ^ > 2 CO k Z CO 2 CO illSN I NVIN0SH1IIAIS S3ldVaan LIBRARIES SMITHSONIAN INSTITUTION NOIlfUllSNI NVINOSHU _____ — ^ , co CO ^ ^ -SX 1\ 1 * (i§^k I * 1 (&^k i I V co pi I- _ (n -

/ 5 'V “ o Z _) Z -I Z _) 2 iTitution NouniiiSNi nvinoshiiws S3iavaan LIBRARIES SMITHSONIAN_INSTITUTION _NOIin z r~ z i ava a n l z < w#' m > co ‘ ‘ ' ’ m co CO — co £ co BRARIES SMITHSONIAN INSTITUTION NOlinillSNI NVINOSH1IIA1S S3iavaaiT LIBR CO z » CO z co z , £ % E /jggjjK - v ITITUTION NOlinillSNI NVINOSHIIWS S3iavaail LIBRARIES SMITHSONIAN INSTITUTION N0I1H c H O c o “■ o Z _j Z _) avaan libraries Smithsonian institution NouniiiSNi nvinoshiiims saiavaan libr z r~ _ z r- . z r- 03 33 > 33 co — co £ co z co TITUTION NOIlfUliSNI NVINOSHIIINS S3iavaan LIBRARIES SMITHSONIAN INSTITUTION NOIlf > -w- 5 > ml CO z CO * Z co i/lBRARIES SMITHSONIAN INSTITUTION NOlinillSNI NVINOSHIIWS S3iavaa \ ^ y to Z co co