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CO _ THSONIAN institution NOliniliSNI NVINOSHlIl^S S3iyvyaiT LIBRARIES SMITHSONIAN INSTITL ^ z: » CO z CO z , CO ^ ^ 2 ^ ? x^>vyci?x < § r'A 5: ^ ^ v'^ . Zi ^ ^ ...-. _ s >' 2 s MOSHiiLMs S3iyvaan libraries smithsonian institution NoiiniiiSNi nvinoshih^s'^sb i av \ ^ CO — CO — CO Palaeontology VOLUME 20-PART 3 AUGUST 1977 Published by The Palaeontological Association ■ London Price £9 THE PALAEONTOLOGICAL ASSOCIATION The Association publishes Palaeontology and Special Papers in Palaeontology. Details of member- ship and subscription rates may be found inside the back cover. PALAEONTOLOGY The journal Palaeontology is devoted to the publication of papers on all aspects of palaeontology. Review articles are particularly welcome, and short papers can often be published rapidly. A high standard of illustration is a feature of the journal. Four parts are published each year and are sent free to all members of the Association. 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 The Secretary, P.A. Publications Committee, Department of Geology, Sedgwick Museum, Downing Street, Cambridge, CB2 3EQ, England, who will supply detailed instructions for authors on request (these were published in Palaeontology, 15, pp. 676-681). SPECIAL PAPERS IN PALAEONTOLOGY This is a series of substantial separate works. Members may subscribe to the Series; alternatively, Ordinary and Student members only may obtain individual copies at reduced rates. The following Special Papers are available ; 1. (for 1967): Miospores in the Coal Seams of the Carboniferous of Great Britain, by a. h. v. smith and M. A. BUTTERWORTH. 324 pp., 72 text-figs., 27 plates. Price £8 (U.S. $16.00), post free. 2. 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Seven new species of the ostracod genus Hornibrookella are described and illustrated from the uppermost Maastrichtian and Palaeocene of eastern Saudi Arabia: Hornibrookella cyclifossata, H. cyclopea, H. cuspidata, H. divergens, H. episcelis, H. posterisella, and H. cjuinquecellulosa. They occur at earlier horizons than species of the genus described from Europe and Pakistan, A modification of the Liebau diagram has been adopted for the analysis of the ornament. The uppermost Maastrichtian is represented in Saudi Arabia by the Lina Member of the Aruma Formation (text-fig. 1 The Lina Member is separated from the under- lying Atj Member by a widespread disconformity, and is overlain by the Umm er Radhuma Formation of Palaeocene and lower Eocene age. The Lina Member consists, in the type locality, of yellow-brown dolomite and calcareous shale, olive shale, argillaceous dolomite, interbedded limestone, and dolomite. TEXT-FIG. 1. Outcrop map of Aruma (upper Cretaceous) and Umm er Radhuma (Palaeocene and lower Eocene) Formations and locations. From El-Khayal 1974, [Palaeontology, Vol. 20, Part 3, 1977, pp. 483-502, pis. 53-58.] A 484 PALAEONTOLOGY, VOLUME 20 The Umm er Radhuma Formation in the reference section is divided into two units, the upper consisting of calcarenitic limestone, aphanitic limestone, and dolomite; the lower of aphanitic limestone (Powers et al. 1966). Repository. All the figured material is deposited in the British Museum (Natural History), London. SPECIFIC DISCRIMINATION Liebau (1969, 1971, 1975a, 19756) and Benson (1972) have suggested methods for the analysis of the ornament in genera of the Trachyleberididae based on fossal patterns and pore conuli. I have found this approach of great value in discriminating species of the Trachyleberididae, although the position and distinction of the pore conuli may vary within one species. Modifications were suggested by Neale (1975). In the present study I have adopted Liebau’s system but extended it to include ventral and dorsal views. The system as applied to the type-species of Hornibrookella {H. anno (Lienenklaus); see Al-Furaih 1975) is shown in text-fig. 2. The anterior fossae are analysed in four series (A-D) which run parallel to the anterior margin. E surrounds the subcentral tubercle. K and V lie above and below E and are parallel TEXT-FIG. 2. Analysis of pattern of ornamentation in the type-species, Hornibrookella anna (Lienenklaus), u, b, left valve, u, lateral view. grouping of fossae, c, d, right valve, c, ventral view. d, dorsal view. AL-FURAIH: HORNIBROOKELLA 485 to the length of the shell; L, M, N, O, and P lie between K and V posterior to the subcentral tubercle; F, G, and H parallel the posterior margin. X covers the reticula- tion developed on the subcentral tubercle, and is particularly useful for specific discrimination. The ventral and dorsal development is indicated by Z and Y respec- tively. This analysis is applicable to all the new species described in the present paper. SYSTEMATIC DESCRIPTIONS Family trachyleberididae Sylvester-Bradley, 1948 Genus hornibrookella Moos, 1965 Type species. Cy there anna Lienenklaus, 1 894. Diagnosis. A genus of Trachyleberididae, with subrectangular carapace. Shell surface strongly reticulate with no median ridges, although some species may have sub- ordinate ribs. Dorsal and ventral ridges well marked. Eye and subcentral tubercles distinct. Hinge amphidont. Remarks. Moos (1965) proposed Hornibrookella as a subgenus of Quadracythere to accommodate species in which the uppermost adductor muscle scar is divided into two spots. I noticed in my work on H. anna (Lienenklaus) that these features of the muscle-scar pattern may vary within a single species; so the pattern should not, in my opinion, be used as the main criterion to distinguish Quadracythere from Horni- brookella (see Al-Furaih 1975). Quadracythere differs from Hornibrookella in being quadrate in outline; both genera are reticulate, but Hornibrookella does not develop the median longitudinal ridges evident in Quadracythere. Hornibrookella cyclifossata sp. nov. Plate 53, figs. 1,2; text-fig. 3 Derivation of name. Latin cyclifossata, with round holes. Material. Three hundred and thirty carapaces from El-Alat W-1. Type locality and horizon. El-Alat W-1, sample 1251—65 ft below the surface. Upper Palaeocene. Diagnosis. Surface reticulate with rounded fossae, the fossae of the second anterior row (B) oval shaped. Height almost equal throughout the carapace. Description. Surface coarsely and deeply reticulate with rounded fossae. Subcentral tubercle weakly developed, eye tubercle distinct. There is a distinct ventrolateral ridge and a short curved horn-like ridge at the posterodorsal corner. Normal pores form domes, free-standing in the solum of each reticulum and presumably terminate in sieve-plates, but these are obscured by recrystallization. Internal details unknown. Sexual dimorphism strongly marked, the males are longer than the females. Dimensions (/xm). Holotype, male carapace, OS 5244 Paratype, female carapace, OS 5245 Length 732 634 Height 415 415 Width 427 415 Distribution. Known from Palaeocene of Saudi Arabia. 486 PALAEONTOLOGY, VOLUME 20 Affinities and differences. The present species shows some affinity to H. quinque- ceUidosa sp. nov. but is longer, height almost equal throughout the carapace. H. posterisella sp. nov. has well-developed subcentral tubercle. H. cyclifossata differs from H. episcelis in details of ornamentation and the latter has a well-developed caudal process. TEXT-FIG. 3. Analysis of pattern of ornamentation in Hornibrookella cyclifossata sp. nov. a-d, male left side of complete carapace, a, lateral view, b, grouping of fossae, c, dorsal view, d, ventral view. Hornibrookella cyclopea sp. nov. Plate 54, figs. 1-4; text-fig. 4 Derivation of name. Greek cyclopea, circle-eyed. Material. Forty-eight carapaces, 6 right valves, and 10 left valves from El-Alat W-1. Six carapaces, 1 right valve, and 1 left valve from Abqaiq W-69. Type locality and horizon. El-Alat W-1, sample 1827—34 ft below the surface. Lower Palaeocene. EXPLANATION OF PLATE 53 Stereoscopic paired photographs. Eigs. 1, 2. Hornibrookella cyclifossata sp. nov. El-Alat W-1, sample 1251—65 ft below the surface. 1 , paratype, female carapace, OS 5245. External lateral view from left, x 1 04. 2, holotype, male carapace, OS 5244. External lateral view from left, x 90. Eigs. 3,4. Hornibrookella cuspidata sp. nov. El-Alat W-1, sample 1251— 65 ft below the surface. 3, paratype, female carapace, OS 5266. External lateral view from right, x 99. 4, holotype, male carapace, OS 5265. External view from right, x 82. PLATE 53 AL-FURAIH, Honiihrookella cyclifossata and H. cuspidata 488 PALAEONTOLOGY, VOLUME 20 Diagnosis. A species of the genus Hornibrookella with subrectangular carapace, moderately elongate. Dorsal and ventral margins converging slightly towards the posterior. Highest point of carapace in region of eye tubercle. Description. Surface strongly reticulate. Domed normal pore canals quite distinct, rather large, one in each reticule. Radial pore canals not very well preserved but appear to be simple. Duplicature of moderate width. Selvage prominent submarginal in the left valve. The muscle scars are hard to distinguish, due to preservation, but appear to be typical for the genus. Hinge holamphidont. Sexual dimorphism rather marked ; the females are shorter than the males. TEXT-FIG. 4. Analysis of pattern of ornamentation in Hornibrookella cyclopea sp. nov. a-d, female left valve. a, lateral view, b, grouping of fossae, c, dorsal view, d, ventral view. EXPLANATION OF PLATE 54 Stereoscopic paired photographs. Figs. 1-4. Hornibrookella cyclopea sp. nov. El-AlatW-1, sample 1827— 34 ft below the surface. 1,4, holotype, male carapace, OS 5246. 1 , external lateral view from right, x 76 ; 4, details of ornament showing domed pore canals x 532. 2, paratype, male left valve, OS 5248. External lateral view, x75. 3, paratype, female left valve, OS 5247. Internal lateral view, x 83. PLATE 54 la lb 2a 2h AL-FURAIH, Hornihrookella cyclopea 490 PALAEONTOLOGY, VOLUME 20 Dimensions (;um). Length Height Width Holotype, male carapace, OS 5246 854 488 463 Paratype, female left valve, OS 5247 780 488 Paratype, male left valve, OS 5248 866 512 Distribution. Known from the uppermost Cretaceous and lower Palaeocene of Saudi Arabia. Affinities and differences. The reticular pattern somewhat resembles H. quinquecellulosa but shape is very different, with greatest height in different position, and H. qninque- ceUidosa is more quadrate in lateral outline. H. episcelis sp. nov. is also similar but differs in details of the ornament, and has a better-developed ventrolateral ridge, which expands posteriorly into an ala-like extension. Hornibrookella cuspidata sp. nov. Plate 53, figs. 3, 4; text-fig. 5 Derivation of name. Latin, pointed. Material. Two carapaces from El-Alat W-1, sample 1251—65 ft. Type locality and horizon. El-Alat W-1, sample 1251—65 ft below the surface. Upper Palaeocene. Diagnosis. A species of Hornibrookella with carapace thick-shelled, distinct caudal process. Surface reticulate with thick muri. TEXT-FIG. 5. Analysis of pattern of ornamentation in Hornibrookella cuspidata sp. nov. a-d, male left side of complete carapace, a, lateral view, b, grouping of fossae, c, dorsal view, d, ventral view. AL-FURAIH: HO RNIBROOKELLA 491 Dimensions (i-im). Holotype, male carapace, OS 5265 Paratype, female carapace, OS 5266 Length 781 634 Distribution. Known from the upper Palaeocene of Saudi Arabia. Height 432 366 Width 415 366 Affinities arid differences. This species bears some resemblance to H. arcana (Lubimova and Guha) (see Siddiqui 1971) from the Eocene of Kutch, India but differs in details of ornamentation, further, dorsal margin in H. arcana has a well-marked concavity behind the anterior cardinal angle. Remarks. Only two specimens of this species have been found in El-Alat W-1, sample 1251—65 ft. Hornibrookella divergens sp. nov. Plate 55, figs. 1-4; text-fig. 6 Derivation of name. Latin, divergens. divergent, with reference to the ornament in the posterior half. Material. Fifty-three carapaces, 5 right valves, and 5 left valves from El-Alat W-1. Two carapaces from Abqaiq W-69. Type locality and horizon. El-Alat W-1, sample 1827 — 34 ft below the surface. Lower Palaeocene. TEXT-FIG. 6. Analysis of pattern of ornamentation in Hornibrookella divergens sp. nov. a-d, male left valve, a, lateral view. b. grouping of fossae, c, dorsal view, d, ventral view. 492 PALAEONTOLOGY, VOLUME 20 Diagnosis. Shell surface reticulate with subordinate ribs arranged in radial pattern, clearly seen in posterior half. Carapace subrectangular with a gently convex dorsal margin. The ventral ridge is weaker in the posterior part. Description. Sexual dimorphism rather marked, the females are shorter and higher than the males. Small marginal denticles often apparent on posterior and anterior margins. Denticles may be absent, depending on state of preservation. Eye tubercle distinct but low. Ventrolateral ridge well developed but weak in the posterior part. Duplicature of moderate width with subperipheral selvage. Inner margin and line of concrescence coincide. Radial pore canals simple, more or less straight. Muscle scars consist of subvertical row of four adductors, situated on the posterior margin of the muscle-scar pit, with two frontal scars. The upper frontal scar circular, the lower one reniform. Hinge holamphidont. Dimensions (fim). Length Height Width Holotype, female right valve, OS 5249 756 427 Paratype, male left valve, OS 5250 829 463 Paratype, female carapace, OS 5251 793 451 463 Paratype, male left valve, OS 5252 805 439 Distribution. Known from the uppermost Cretaceous and lower Palaeocene of Saudi Arabia. Affinities and differences. H. divergens is unlikely to be confused with any other species. It shows some resemblance to the type species of Hornibrookella in the out- line; although H. anna has a sharp posterior cardinal angle and the dorsal margin in H. divergens has a clear concavity behind the eye tubercle, clearly seen in the left valve. Hornibrookella episcelis sp. nov. Plate 56, figs. 1-4, text-fig. 7 Derivation of name. Greek, epi+scelis, rib, with reference to the rudimentary ribs. Material. Thirty-four carapaces, 9 right valves, and 5 felt valves from El-Alat W-1. Thirty-nine carapaces, 9 right valves, and 15 left valves from Abqaiq W-69. Type locality and horizon. El-Alat W-1, sample 1816 — 22 ft below the surface. Lower Palaeocene. Diagnosis. Carapace with distinct caudal process. Surface reticulate with a tendency towards the development of ribs. Description. Duplicature of moderate width with subperipheral selvage. Inner margin and line of concrescence coincide. Muscle scars not very well displayed but seem to EXPLANATION OF PLATE 55 Stereoscopic paired photographs. Figs. 1-4. Hornibrookella divergens sp. nov. El-Alat W-1, sample 1827— 34 ft below the surface. 1, holotype, female right valve, OS 5249. External lateral view, x86. 2, 3, paratype, male left valve, OS 5250; 2, external lateral view, x78; 3, internal lateral view, x80. 4, paratype, female carapace, OS 5251. Dorsal view, x 85. PLATE 55 AL-FURAIH, Hornihrookella divergens 494 PALAEONTOLOGY, VOLUME 20 be four adductors and two frontal scars. Normal pore canals simple. Hinge holamphidont. Right valve hinge with highly projecting tooth, anteromedian socket opening into posteromedian groove, posterior reniform tooth, the left valve comple- mentary. Sexual dimorphism distinct, the females wider and higher than the males. Dimensions (/xm). Length Height Width Holotype, female carapace, OS 5253 805 500 451 Paratype, female right valve, OS 5254 780 439 Paratype, male carapace, OS 5255 768 415 341 Distribution. Known so far from the uppermost Cretaceous and lower Palaeocene of Saudi Arabia. A fftnities and differences. This species is similar to H. posterisella but differs in having a more pronounced caudal process, the rudiments of longitudinal ribs and in details of the reticulation. Internally, it has wider duplicature. H. quinquecellulosa sp. nov. has a different lateral outline, less well developed subcentral tubercle, and deeper reticulation. TEXT-FIG. 7. Analysis of pattern of ornamentation in Hornibrookella episcelis sp. nov. a-d, male left valve. a, lateral view, b, grouping of fossae, c, dorsal view, d, ventral view. EXPLANATION OF PLATE 56 Stereoscopic paired photographs. Figs. 1-4. Hornibrookella episcelis nov. El-Alat W-1, sample 1816—22 ft below the surface. 1,4, paratype, female right valve, OS 5254. 1 , external lateral view, x 83 ; 4, internal lateral view, x 83. 2, 3, holotype, female carapace, OS 5253; 2, external lateral view from left, x80; 3, ventral view, x81. PLATE 56 AL-FURAIH, Hornihrookella episcelis 496 PALAEONTOLOGY, VOLUME 20 Hornibrookella posterisella sp. nov. Plate 57, figs. 1-4; text-fig. 8 Derivation of name. Latin, sella, saddle, with reference to the posterior saddle. Material. Three hundred and sixty carapaces, 95 right valves, and 114 left valves from Abqaiq W-69. Ninety-nine carapaces, 20 right valves, and 15 left valves from El-Alat W-1. Type locality and horizon. Abqaiq W-69, sample 1780—90 ft below the surface. Lower Palaeocene. Diagnosis. A strongly reticulate species of Hornibrookella in which the posterior cardinal process joins with the posterodorsal ridge to form a triangular and horizontal posterior saddle. Anterior and posterior cardinal angles distinct. Anterior margin rounded with a slight anterodorsal concavity particularly in the left valve. Sexual dimorphism pronounced. TEXT-FIG. 8. Analysis of pattern of ornamentation in Hornibrookella posterisella sp. nov. a-c, female left valve, a, lateral view, b, grouping of fossae, c, dorsal view, d, female ventral view of right valve. EXPLANATION OF PLATE 57 Stereoscopic paired photographs. Figs. 1-4. Hornibrookella posterisella sp. nov. Abqaiq W-69, sample 1780—90 ft below the surface. 1, paratype, male carapace, OS 5260. External lateral view from right, x71. 2, holotype, female left valve, OS 5256. External lateral view, x 77. 3, 4, paratype, female right valve, OS 5259. 3, muscle scars, x410; 4, internal lateral view, x82. PLATE 57 AL-FURAIH, Honiihrookella posterisella 498 PALAEONTOLOGY, VOLUME 20 Description. Strongly dimorphic, the males are longer than the females. Anterior margin finely denticulate, posterior margin with larger denticles. Normal pore canals of two kinds: intramural, badly preserved and difficult to determine and domed pores, free-standing in the solum of each reticulum, and presumably terminating in sieve-plates as in Mutilus retiformis Ruggieri and Sylvester-Bradley, 1973, but now obscured by recrystallization. Radial pore canals not well displayed due to the form of preservation and calcification, but appear to be simple. Duplicature of moderate width, selvage peripheral in left valve but bordered by flange in right valve. Right valve with well-developed flange groove, particularly on the venter. Muscle scars are in a vertical row of four elongate adductor and two frontal scars. The upper frontal scar more or less circular in holamphidont. outline, the lower one reniform Dimensions (/xm). Length Height Width Holotype, female left valve, OS 5256 854 512 Paratype, male carapace, OS 5257 951 519 537 Paratype, female carapace, OS 5258 878 537 488 Paratype, female right valve, OS 5259 781 476 Paratype, male carapace, OS 5260 915 488 463 Distribution. Known from the uppermost Cretaeeous and lower Palaeocene of Saudi Arabia. Affinities and differences. This species differs from H. quinquecellulosa sp. nov. and H. cyclopea sp. nov. in shape and having well-marked anterior and posterior cardinal angles. H. posterisella closely resembles H. bilamellosa (Marliere) {Bradleya bila- mellosa Marliere, 1958), but differs in having a distinct hinge-ear in the left valve, a straight ventral margin and the anterior margin, in lateral view with a slight antero- dorsal concavity in front of the hinge-ear. Hornibrookella quinquecellulosa sp. nov. Plate 58, figs. 1-4; text-fig. 9 Derivation of name. Latin, quinquecellulosa, ‘with five-fold cells’; with reference to shape of fossae. Material. One hundred and thirty-four carapaces, 40 right valves, and 31 left valves from El-Alat W-1. Seven carapaces from Abqaiq W-69. Type locality and horizon. El-Alat W-1, sample 1865—75 ft below the surface. Lower Palaeocene. Diagnosis. Carapace subquadrate, with coarse reticulation, with pentagonal fossae. Dorsal margin convex due to the arched posterodorsal ridge. Greatest height passes just behind the subcentral tubercle. EXPLANATION OF PLATE 58 Stereoscopic paired photographs. Pigs. 1-4. Hornibrookella quinquecellulosa sp. nov. El-Alat W-1, sample 1865 — 75 ft below the surface. 1, paratype, female carapace, OS 5263. External lateral view from right, x99. 2, holotype, male left valve, OS 5261. External lateral view, x 77. 3, paratype, male left valve, OS 5264. Internal lateral view, X 82. 4, paratype, male right valve, OS 5262. Internal view, x 78. PLATE 58 la 3a 3b 2a 2b 4a 4b AL-FURAIH, Hornihrookella quinqiieceUulosa 500 PALAEONTOLOGY, VOLUME 20 Description. Sexual dimorphism rather marked, presumed females shorter, higher, and wider than presumed males. Normal pore canals domed. Duplicature of moderate width. Selvage prominent in both valves, submarginal in left valve, in outer third of duplicature in right valve. Vestibule narrow. Muscle scars not very well displayed due to preservation but appear to be typical for the genus. Hinge holamphidont. Dimensions (,um). Holotype, male left valve, OS 5261 Paratype, male right valve, OS 5262 Paratype, female carapace, OS 5263 Paratype, male left valve, OS 5264 Length Height Width 829 561 829 561 659 439 415 780 512 Distribution. Known from the uppermost Cretaceous and lower Palaeocene of Saudi Arabia. A ffinities and differences. This species differs from other species in this paper in being more quadrate and having pentagonal fossae. TEXT-FIG. 9. Analysis of pattern of ornamentation in Hornibrookella quinquecellulosa sp. nov. a-d, female left valve, u, lateral view. 6, grouping of fossae, c, dorsal view, d, ventral view. AL-FURAIH: HORNIBROOKELLA 501 DISCUSSION Moos originally established Hornibrookella as a subgenus for Quadracy there. It has since been raised to generic status (Al-Furaih 1975). The following species are believed to be European representatives of the genus: Hornibrookella anna (Lienenklaus): Lower Oligocene H. bilamellosa {MdirWero): Danian Montian H. confluens (Reuss) : Upper Oligocene H. macropora (Bosquet) : Oligocene Pliocene H. partimglabra (Moos) : Lower Oligocene H. valirenkarnpi (Moos): Lower Oligocene The following have been described from Pakistan and India: H. arcana (Lubimova and Guha): Middle Eocene H. directa (Siddiqui): H. platybomus (Siddiqui) : H. subcpiadra (Siddiqui): H. sp. A. (Siddiqui): The Arabian species here described show close similarity with these forms, but occur at earlier horizons. This would indicate that the origin of the genus Horni- brookella occurred in the Arabian area. Lower Eocene Upper Palaeocene Upper Eocene Lower Eocene Acknowledgements. I thank Professor P. C. Sylvester-Bradley for his supervision, helpful suggestions, and constant encouragement throughout this work, and Professor A. A. El-Khayal who kindly placed his collection at my disposal. I am also grateful to Dr. R. H. Bate, British Museum (Natural History), who gave me access to comparative material kept under his care. Thanks are due to Dr. B. Moos and Dr. G. Deroo for providing comparative material. I also thank Dr. David J. Siveter for making valuable suggestions and Mr. G. McTurk for taking the stereoscan photographs. My appreciation to the Arabian American Oil Company for providing the well samples and to Dr. R. Alexander, Mr. D. Cameron, and Dr. M . Kerdany for their kind help in providing valuable information. The work was financed by Riyadh University. REFERENCES AL-FURAIH, ALi A. F. 1975. On Hornibrookella anna (Lienenklaus). A Stereo-Atlas of Ostracod Shells, 2 (3), 21U214. BENSON, R. H. 1972. The Bradleya problem, with descriptions of two new psychospheric ostracode genera, Agrenocythere and Poseidonamiciis (Ostracoda: Crustacea). Smithson. Contr. Paleobiol. 12, 138 pp., 38 pis., 67 figs., 4 tables. EL-KHAYAL, A. A. 1974. Foramiuiferal biostratigraphy of the Umm er Radhuma Formation (Palaeocene- Lower Eocene) of Eastern Saudi Arabia. Bull. Fac. Sci. Riyadh Univ. 6, 195-214, 5 figs. HORNiBROOK, N. DE B. 1952. Tertiary and Recent Marine Ostracoda of New Zealand. Their origin, affinities, and distribution. Palaeont. Bull. Wellington, 18, 1-82, pis. 1-18, 4 text-figs. LiEBAU, A. 1969. Homologisierende Korrelationen von Trachyleberididen-Ornamenten (Ostracoda, Cytheracea). Neues Jb. Geol. Paldont. Mh. 7, 390-402, 4 figs. 1971. Homologe Skulpturmuster bei Trachyleberididen und verwandten Ostrakoden. Diss. Techn. Univ. Berlin, 1 18 pp., 32 figs. 1975u. Comment on suprageneric taxa of the Trachyleberididae. S.n. (Ostracoda, Cytheracea). Neues Jh. Geol. Paldont. Ahh. 148, 3, 353-379, 3 figs. 19756. The left-right variation of the Ostracode ornament. Bull. Am. Paleont., 65, pp. 78-86, 1 pi., 5 text-figs. 502 PALAEONTOLOGY, VOLUME 20 LiENENKLAUS, E. 1894. Monographic der Ostrakoden des nordwestdeutschen Tertiars. Z. dt. geol. Ges. 46, 158-268, pis. 13-18. LUBIMOVA, p. s., GUHA, D. K. and MOHAN, H. 1960. Ostracoda of Jurassic and Tertiary deposits from Kutch and Rajasthan (Jaisalmer), India. Bull. geol. Min. Metall. Soc. India, 22, 1-60, pis. 1-4. MARLiERE, R. 1958. Ostracodcs du Monfien de Mons et resultats de leur etude. Man. soc. beige Geol. no. 5, 53 pp., pis. 1-6. MOOS, B. 1965. Die Ostracoden-Fauna des Unteroligozans von Bunde (Bl. Flerford-west, 3817) und einige verwandte jiingere Arten (Ostr., Crust.) 1. Quadracytbere (Hornibrookella) n. subg., Pokornyella, Hemicythere, Hermanites. Geol. Jber. 82, 593-630, pis. 34-39. NEALE, J. w. 1975. The Ostracod fauna from the Santonian Chalk (Upper Cretaceous) of Gingin, Western Australia. Spec. Pap. Palaeontol. 16, 1-81, 17 text-figs., pis. 1-22. POWERS, R. w. et al. 1966. Geology of the Arabian Peninsula (Sedimentary Geology of Saudi Arabia). Prof. Pap. U.S. geol. Surv. 560-D, pp. 1-147. RUGGiERi, G. and SYLVESTER-BRADLEY, p. c. 1973. On Miitllus retlformls (Terquem). A Stereo-Atlas of Ostracod Shells, 1 (2), 109-116. siDDiQUi, Q. A. 1971. Early Tertiary Ostracoda of the Family Trachyleberididae from West Pakistan. Bull. Br. Mus. Nat. hist. (Geol.) Suppl. 9, 1-98, pis. 42. SYLVESTER-BRADLEY, p. c. 1948. The Ostracodc genus Cythereis. J. Paleont. 22, 192-191 . and BENSON, r. h. 1971. Terminology for surface features in ornate Ostracodes. Lethaia, 4, 249-286, 48 figs. Typescript received 21 January 1976 Revised typescript received 5 July 1976 ALI A. F. AL-FURAIH Department of Geology University of Riyadh Riyadh Saudi Arabia THE EVOLUTIONARY INTERPRETATION OF THE FORAMINIFERIDA A REN O BU LI M IN A, GAVELINELLA, AND HEDBERGELLA IN THE ALBIAN OF NORTH-WEST EUROPE by R. J. PRICE Abstract. Arenohulimina macfadyeni Cushman is suggested as the parent stock from which A. chapnumi Cushman arose, probably around the Middle-Upper Albian boundary. A. chapmani gave rise to A. frankei Cushman in the varicosum Subzone, which in turn gave rise to A. truncata (Reuss) in the aiiritus Subzone. A. sahulosa (Chapman) also appears in the auritus Subzone. A . frankei, not A . sahulosa, is suggested as the parent stock from which Flourensina intermedia Ten Dam evolved in the upper Stoliczkaia dispar Zone, whilst the extinction of A. chapmani at this level is followed by the appearance of A. advena (Cushman). The variations in test morphology of Gavelinella intermedia (Berthelin) are discussed. This species is suggested as the parent from which G. rudis (Reuss) and G. cf. haltica Brotzen arose in the Middle Albian. Both G. cenomanica (Brotzen) and G. haltica Brotzen arose from G. intermedia in the varicosum Subzone and 5. dispar Zone respectively. Hedhergella infracretacea (Glaessner) is suggested as the primitive Lower Cretaceous species from which H. delrioensis (Carsey) and H. planispira (Tappan) arose probably in the Aptian. Their intergradation in the Lower Albian is discussed. H. infracretacea, which became extinct around the rostratum-perinflatum Subzone boundary, possibly gave rise to H. hrittonensis Loeblich and Tappan in the auritus Subzone. The area defined as north-west Europe is outlined below with reference to the geographical extent of the Albian sediments studied. Sample localities visited and collected are shown on text-fig. 1. Geographically the area is defined here as southern England (the Weald and Devon to Bedfordshire outcrop), northern and central Erance (the Boulonnais, Pays de Bray, Pays de Caux, and Paris Basin), the Netherlands, and north-west Germany (the Eower Saxony Basin and Hils). Also included on text-fig. 1 are the subsurface sections examined from the Netherlands by Euchs and Stradner (1967), and Ten Dam (1950) at Delft and Winterswyk respectively; together with the Schoonebeek section, samples from which were made available to the writer by the Shell Petroleum Company (N.A.M.). Finally, the numerous subsurface sections examined from the Hanover area are shown on text-fig. 2. These were made available to the writer during a visit to the Bundesanstalt fiir Geowissenschaften und Rohstoffe. Thus an almost complete, composite sequence of Albian sediments was studied with the exception of three subzones within the Lower Albian, namely milletioides (acuticostata), regularis, and kitcliini Subzones, which were not exposed during sample collection or penetrated during subsurface investigation. Table 1 is included to show the complete ammonite zonal and subzonal scheme referred to within the text. The extremely good ammonite stratigraphical control during sample collection enabled species ranges to be defined, largely for the first time, to subzonal level over a wide geographical area, and together with population percentage variation was used to show horizons of acme and extinction. The subzonal ranges of species are [Palaeontology, Vol. 20, Part 3, 1977, pp. 503-527, pis. 59-61.] 504 PALAEONTOLOGY, VOLUME 20 given only from those samples studied personally. Where other workers have recorded older or younger occurrences note is made of this. The sudden diversification of foraminiferid species, and their rapid evolution is a product of the Upper Albian only. This high diversity is particularly marked within the S. dispar Zone, which was an horizon of rapid radiation of species whose ancestors range from the Lower and Middle Albian. Their radiation at this level is probably related to environmental changes in the Upper Albian as discussed by the writer (in press (a)). Thus the S. dispar Zone illustrates examples of evolutionary develop- ment which have aided both stratigraphical zonation, especially in the Upper Albian, together with the opportunity to study the morphological variation of species to subzonal level. In all cases the morphological changes in test outline have been used to establish an evolutionary sequence with note made of microspheric and megalo- spheric generations as discussed by other workers. However, the exact stratigraphical position of species within the uppermost S. dispar Zone cannot always be correlated with ammonite subzone, as the macro-fauna at this level is sometimes very rare. Also samples were often obtained from borehole sections without ammonite control. TEXT-FIG. 1. Sample localities and outcrop of the Albian strata in north-west Europe. PRICE; ALBIAN FO R A M I N I FE R I D A 505 Nevertheless, the very useful stratigraphical index foraminifera within the S. dispar Zone have enabled the writer to establish a refined zonation scheme for this horizon (in press {b)). The percentage abundance of individual species within the foraminiferal assemblage is shown on text-fig. 3. All other figures are referable to this. The methods and calcula- tions used in assemblage analyses have been discussed by the writer elsewhere (1975). All the illustrated specimens have been deposited in the collections of the Depart- ment of Geology (Micropalaeontology), University College, London, and bear the numbers given in the explanations of the plates. TEXT-FIG. 2. Borehole localities studied in the Lower Saxony Basin (north-west Germany). 506 PALAEONTOLOGY, VOLUME 20 TABLE 1. Zonal and subzonal ammonite scheme for the Albian hoplitinid faunal province in north-west Europe. Stoliczkaia dispar 4. Mortoniceras (Dwnovarites) perinflatum 5. Mortoniceras (Mortoniceras) rostratum 3. Upper Albian < . Mortoniceras (Mortoniceras) inflatum Callihoplites auritus Hysteroceras varicosum Hysteroceras orbignyi Dipoloceras cristatum Euhoplites lautus 2. Middle Albian J Euhoplites loricatus , Hoplites (Hoplites) dentatus ( Anahoplites daviesi j Euhoplites nitidus 1 Euhoplites meandrinus Mojsisovicsia subdelaruei Dimorphoplites niobe Anahoplites intermedins ( Hoplites (Hoplites) spathi < Lyelliceras lyelli ( Hoplites (Isohoplites) eodentatus 1. Lower Albian ' Douvilleiceras mammillatum 6. North-west Germany Protohoplites (Hemisonneratia) puzosianus Otohoplites raulinianus Cleoniceras ( Cleoniceras) fioridum Sonneratia kitchini Southern England Leymeriella (Leymeriella) tardefurcata Leymeriella (Leymeriella) regidaris = L. (L.) regular is Leymeriella acuticostata = Hypacanthoplites milletioides Proleymeriella schrammeni = Eranhamia farnhamenisis Zonal and subzonal scheme discussed by: 1. Casey 1961 ; 2. Owen 1971a; 3. Owen 1971ft; 4. Owen 1975, Vraconian; 5. Owen 1975 formerly Arrhaphoceras suhstuderi\ 6. Owen, pers. comm. SYSTEMATIC DESCRIPTIONS AND EVOLUTIONARY INTERPRETATION The classification used is that of Loeblich and Tappan (1964) with their later amend- ments (1974). An abridged synonymy, which in the writer’s opinion affords easiest reference and best illustration for each species discussed is listed below. A complete systematic description of individual species is not given. This may be found in the relevant literature listed within the references, and from original descriptions as found in the synonymy lists. It is only the morphological lineages and evolutionary relationships of the species that are relevant to this discussion. Also the problems of new generic status are considered in the appropriate sections below. Following the synonymy list, the evolutionary interpretation is discussed. PRICE: ALBIAN FORAMINIFERIDA 507 SUB- STAGE AMMONITE ZONE AMMONITE SUBZONE No Macrofouna! Equivalent Stoticzkaia z < (D _l dispar Mortoniceras (Durnovarites) perinflatum Mortoniceras ( Mortoniceras ) rostratum JPPER Callihoplites auritus Mortoniceros (Mortoniceras) inflotum Hystoceras varicosum Hystoceras orbignyi Dipoloceras cristatum Euhop/itas Anohoph'tes daviesi z /outus Euhophtes nit/dus < Euhop/ites meondrinus (O < u EuhopHtes hricatus Mojsisovicsio subdelaruei' DimorphopUtes niobe -J o AnahopHtes intermed/us 0 1 HopHtes (HopHtes) dentatus Hophtes (HopHtes) spothi Lye/Hceras lyelli Hop/ites(lsofKp/ites)e* o o c: cj e & ■8 I A cf. obUquo] Large V'V'W overlapping last chamber ^ Short form; rounded or pointed Coarsely to P™"'™"'' finely arenaceous |/T intermedia\ Large over- lapping last chamber A.sobu/o^ Very coarsely arenaceous Sub-quadrate cross-section i; coorsely ^arenaceous Triangulate tapering (perinflatum) 1/4. frankei\ Finely arenaceous DTI Rounded crosssection^j^ (voricosum - rostra turn) |/4. truncatol Large overlapping lost chamber |/4.c/>qo/7?(7/?/| Rapidly tapering proximally Coarsely arenaceous I A.. I L_ ? 7 __ Population % values I > 60 40-60 20-40 5 - 20 1 - 5 0.1 - 1.0 Rapidly tapering viOT Finely W arenaceous Elongated ^ tapering form (interme1 Rounded periphery s Rounded periphery IG. rudis\ Depressed sutures involute, biumbilicote RouLed periphery ?--? — ?-- Cs .y § o § o G. (xnomonica Distinct spiral ridge Sharp to rounded periphery \G. intermedia] Depressed Smajl sutures umbilici Sharp to rounded periphery Symbols and ‘/.values as FIG. 3 ^ intergradational G intermedia var. A boss Mostly sharp periphery, sometimes rounded TEXT-FIG. 4. Evolutionary interpretation of the genus Gavelinella in the Albian of north-west Europe. 518 PALAEONTOLOGY, VOLUME 20 ‘star-like’ pattern to the sutures on its ventral side, a eharaeteristic of Lingulo- gavelinella', but it also has an umbilicus, this feature being absent in that genus. It ranges throughout the Albian whereas Lingulogavelinella is endemic to the Paris Basin in Lower Albian times and was not found by the writer below the raulinianus Subzone. It is possible that G. tormarpensis is the ancestral species from which the Lingulogavelinella plexus evolved, although this suggestion is only tentative and requires the further investigation of pre-Albian sediments. G. intermedia, which ranges throughout the Albian, is suggested as the parent stock from which other Albian species arose. In the Lower Albian it is abundant in beds of raulinianus to eodentatus Subzonal age. At these horizons and throughout the Middle Albian, it is the single most abundant benthic species. In the puzosianus Subzone the form G. intermedia var. A (nov. com.) is found in association with it. Morphologically both G. intermedia and G. intermedia var. A are extremely similar, except that in certain specimens of the latter a distinct boss is developed on its spiral side. However, both forms are completely intergradational. Khan (1950) adopts the name Anomalina complanata var. reussi to differentiate G. intermedia var. A from G. intermedia. However, the writer agrees with the suggestion of Malapris (1965) in that it is merely a variety of G. intermedia and does not warrant a new specific name. She also errects the new subgenus Berthelina whilst placing A. complanata (Reuss) and A. intermedia Berthelin in synonymy. The significance of subgeneric erection is discussed by Malapris (1965), but is not considered here. Thus G. intermedia var. A is only given variety status which serves as an observation that high boss develop- ment on the spiral side of the species frequently occurs. In any Albian population, however, total gradation may be found. This is particularly well illustrated in the Lower and Middle Albian where from the puzosianus Subzone onwards both forms are very common. Within the upper auritiis Subzone G. intermedia decreases in abundance. Further confusion within the literature has also arisen because G. intermedia var. A has been placed in synonymy of G. bertlielini (Keller, 1935) as described by Ten Dam (1950), Michael (1966), and Fuchs, in Fuchs and Stradner (1967). However, G. bertlielini is of Cenomanian and Turonian age as illustrated by Keller (1935) and Gawor-Biedowa (1972) respectively, and discussed by Hart (oral comm.), who all correctly refer back to the quite different species originally termed Anomalina bertlielini by Keller (1935). The possible difference between these species was also tentatively suggested by Ellis and Messina (1951). During the spat hi Subzone, the first appearance of G. rudis is recorded. This species is suggested as ancestor to G. baltica, as discussed below. However, its evolutionary relationship with G. intermedia is not clear. The rounded periphery of G. rudis and its involute form is in marked contrast to the sharp periphery and evolute appearance of G. intermedia. Within the subdelaruei Subzone a form similar to G. baltica is found, although very rarely. It has been named here G. cf. baltica. In the writer’s opinion the form identified as G. (G.) baltica by Gawor-Biedowa (1972) in the Upper Albian in Poland is this form. Its common occurrence at this level is recorded by Gawor-Biedowa and the writer. The species possesses raised sutures in the initial part of the last whorl and is biumbilicate. Both umbilici are wide and deep. The former whorls are often. PRICE; ALBIAN FORAMINIFERIDA 519 but not always, visible on the spiral side of this predominantly evolute, planispiral form. However, it does not possess raised sutures in the distal portion of its last whorl, or the very wide last whorl of the involute G. haltica. It probably evolved from G. intermedia rather than G. rudis, and possibly merits a new species name. Within the basal varieosurn Subzone, the distinct species G. eenomanica appears, although recorded by Hart (1973a) as ranging from the cristatum Subzone. It closely resembles G. intermedia in outline, from which it probably evolved. However, it possesses a clearly visible spiral ridge. It is common from the auritus Subzone onwards. However, Hart (pers. comm.) now suggests that G. cenomaniea s.s. is a Cenomanian species, with which the writer disagrees. During the perinflatum Subzone, G. baltiea appears, probably arising from G. rudis which disappears in the upper S. dispar Zone. The globular last chamber of G. baltiea is a feature of the species which serves to relate it to G. rudis or possibly G. cf. baltiea in the Upper Albian. The extension of the stratigraphical range of G. baltiea down- wards into the upper S. dispar Zone is proposed here. It was originally recorded by Brotzen (1942) in the Cenomanian. However, both Hart (1973/j) and Malapris and Jannin (1967) have tentatively recorded it within the Upper Albian. HEDBERGELLA Suborder rotaliina Delage and Herouard, 1896 Superfamily globigerinacea Carpenter, Parker, and Jones, 1862 Family hedbergellinae Loeblich and Tappan, 1974 (emend. Rotaliporidae Sigal 1958) Subfamily hedbergellinae Loeblich and Tappan, 1961 Genus hedbergella Bronnimann and Brown, 1958 Hedbergella brittonensis Loeblich and Tappan Plate 61 , figs. 1 -3 1961 Hedbergella brittonensis Loeblich and Tappan, pp. 274-275, pi. 4, figs. 1-8. 1967 Hedbergella brittonensis Loeblich and Tappan; Fuchs (in Fuchs and Stradner), p. 331, pi. 18, fig. Ifl-C. 1972 Hedbergella brittonensis Loeblich and Tappan; Gawor-Biedowa, pp. 67-68, pi. 7, figs. 1, 2(a-c). Hedbergella delrioensis (Carsey) Plate 61, figs. 4-6 1926 Globigerina cretacea d’Orbigny var. delrioensis Carsey, p. 43. 1959 Praeglobtnmcana (Hedbergella) delrioensis (Carsey); Banner and Blow, p. 8. 1961 Hedbergella delrioensis (Carsey); Loeblich and Tappan, p. 275, pi. 2, figs. 11-13. 1972 Hedbergella infracretacea (non Glaessner); Gawor-Biedowa, pp. 69-70, pi. 6, fig. 8o-c. 1973 Hedbergella infracretacea (non Glaessner); Damotte and Magneiz-Jannin, p. 40, pi. 4, figs. 26-30. 1974 Hedbergella delrioensis (Carsey); Longoria, pp. 54-55, pi. 10, figs. 7-9; pi. 26, fig. 11. Hedbergella infracretacea (Glaessner) Plate 61, figs. 7-9 1890 Globigerina cretacea non d'Orbigny; Burrows, Sherborn, and Bailey, p. 566, pi. 11, fig. 18. 1937 Globigerina infracretacea Glaessner, p. 28, text-fig. 1. 520 PALAEONTOLOGY, VOLUME 20 1962 Globigerina infracretacea Glaessner; Bartenstein and Bettenstaedt, pp. 280-281, pi. 39, fig. 15(7, b. 1966 /n/'racre?acefl (Glaessner); Glaessner, pi. l,figs. 1-3. 1967 Hedbergella infracretacea (Glaessner); Fuchs (in Fuchs and Stradner), p. 331, pi. 17, fig. 13fl-c. non 1972 Hedbergella infracretacea (Glaessner); Gawor-Biedowa, pp. 69-70, pi. 6, fig. 8u-c. 1973 Hedbergella infracretacea (Glaessner); Damotte and Magniez-Jannin, p. 40, pi. 4, figs. 31-34. 1974 Hedbergella delrioensis (non Carsey); Longoria, pp. 54-55, pi. 10, figs. 1-6, 10-12. 1974 Hedbergella infracretacea (Glaessner); Longoria, pp. 59-60, pi. 13, fig. 9. Hedbergella planispira (Tappan) Plate 61, figs. 10-12 1940 Globigerina planispira Tappan, p. 122, pi. 19, fig. 12. 1957 Praeglobtnmcana planispira (Tappan); Bolli, Loeblich, and Tappan, p. 40, pi. 9, fig. 3. 1961 Hedbergella planispira (Tappan); Loeblich and Tappan, pp. 267-268, pi. 5, figs. 4-11. 1974 Hedbergella planispira (Tappan); Longoria, pp. 64-65, pi. 11, figs. 4-6; pi. 23, figs. 1-7, 17-18; pi. 24, fig. 10. A general feature in the development of this genus throughout the Albian is the gradual size increase in all species within successively younger beds. Text-fig. 5 shows the suggested evolutionary interpretation for the genus. The first occurrence of Hedbergella within the Albian was recorded in the raulinianus Subzone. Its appearance here is, however, probably environmentally controlled as both H. delrioensis and H. infracretacea occur in older beds as recorded by other workers and discussed below. The greatest problem in establishing an early hedbergellid evolutionary sequence has been the tendency to group forms into a single species, namely H. {Globigerina) infracretacea (Glaessner). From the synonymy list given above, it is the writer’s opinion that this ‘species’ also includes H. delrioensis. Bartenstein and Bettendstaedt (1962) figure H. infracretacea s.s. as ranging from the Lower Barremian, but they do not record H. delrioensis the Lower Cretaceous. Damotte and Magneiz-Jannin (1973) have recorded H. infracretacea in the Lower Aptian of the Aube, France. However, in the writer’s opinion, their figured specimens include both H. infracretacea and H. delrioensis. Both these species have been considered possibly synonymous by Loeblich and Tappan (1961), but they state that the typically small H. infracretacea has not been examined by them. Glaessner (1966, p. 181) in reply states that his subsequent study suggested that H. infracretacea is distinguishable by small size, moderately elevated rather than depressed early coil, and absence of a large spatulate lip which flares slightly at its umbilical end, the presence of such features being characteristic of H. delrioensis. Glaessner further states that Hofker’s study (1961) suggests the possibility of evolutionary trends which would link H. infracretacea with younger and more advanced forms, some of which may possess the characters of H. delrioensis', and also that H. infracretacea may therefore be given the status of a chronosubspecies of H. delrioensis rather than that of a species. However, he adds that the placing of H. infracretacea in synonymy of H. delrioensis which was done by Maslakova (1963) without qualifications or stated reasons cannot be accepted. PRICE: ALBIAN FORAMINIFERIDA 521 SUB- STAGE AMMONITE ZONE AMMONITE SUBZONE No Macrofauna/ Equivalent StoHczkaia z < (Q _J dispar Mortoniceras (Durnovarites) perinflatum Mortoniceras (Mortoniceras) rostratum JPPER Callihoplites auritus Mortoniceras (Mortoniceras) inftatum Hystoceras varicosum Hystoceras orbignyi Dipo/oceras cristatum EuhopHtes AnahopHtes daviesi z /autus EuhopHtes nit id us < Euhophtes meandr/nus (D .J EuhopHtas toricatus Mojsisovicsio subde/on/ei < U Dimorphop/ites niobe 1 o Anahop/ites intermedius o 5 HopHtes (Hop/ites) dentatus Hophtes (Hop/ites) spatbi LyeHiceras lyelli Hop/ites (/sohop/ites) eodentaCus Protohop/ites (Hemison- -nerat/d) puzosianus LOWER ALBIAN DouviHeiceras mammiHatum Otohop/ites rou/inianus C/eoniceras(C) f/or/dum LeymerieHo fL.) tardefurcatQ Pro/eymariet/o /Farn/)omia t sc/>rammen/y fjrnhomensis EVOLUTIONARY INTERPRETATION \H. drittonensis\ very hlgh-spired I Two or three whorls I finely hispid, overlapping last chamber very coarsely hispid ? 7 ?. Strongly oven lapping, finely ^ ?. hispid lost chamber—. one-and-oJialf to two whorls Hispid, high-spired t C> I I 1 I o \H.infracretacea\ i b " I .5 Small, finely hispid form ; strongly overlapping lost chamber 5: high- spired Large form. coarsely hispid last chamber finely hispid low-spired H. de/rioensis I Q. 5: Small, finely- hispld form; low trochospire SIZE INCREASE (ALL SPECIES) THROUGH ALBIAN TIME Symbols and % values as for FIG. 3 i — *■ intergnsdationgl I ^vz-lyelli fjxTENSiON into lr.cretaceo'us Rnely hispid throughout H D/anispira TEXT-FIG. 5. Evolutionary interpretation of the genus Hedbergella in the Albian of north-west Europe. 522 PALAEONTOLOGY, VOLUME 20 Finally, Longoria (1974) states that \ . H. infracretacea (Glaessner) has served as a “waste basket” name for almost thirty-five years and nearly every Lower Cretaceous species of unknown affinity has been referred to this species . . with which the writer agrees. However, the writer’s interpretation of H. infracretacea and H. delrioensis appears to be at variance with that of Longoria (1974) and is discussed below. Within the Lower Albian both species are intergradational, although distinct end members can still be recognized. The following observations are put forward as further evidence for differentiation of the two species. Throughout the Lower Albian, H. infracretacea is extremely small and has a finely hispid test except for the last chamber which is not hispid. A feature of the species at this level is the very fine hispidity on the chambers being more markedly developed on its spiral side, a feature well illustrated by use of the S.E.M. (PI. 61, figs. 7, 8). Also the last two chambers in the final whorl are of the same size and the species has a very high trochospire. Throughout the Middle and particularly in the Upper Albian it progressively increases in size with hispidity now developed on the ventral surface of the chambers also, except for the last chamber which in all specimens is incurved towards the umbilicus and remains non-hispid (PI. 61, fig. 9). In comparison with H. infracretacea. Lower to Middle Albian forms of H. delrioensis have a low trochospire and the ultimate chamber is more inflated than the penultimate, while fine hispidity is equal on all chambers and sides of chambers (PI. 61, figs. 4, 5). In Upper Albian specimens the height of the spire often varies but is characteristically a low trochospire with the last chamber appearing less hispid in comparison with the now more coarse hispidity developed on all previous chambers (PI. 61, fig. 6). The last chamber also becomes very slightly inturned toward the umbilicus. This increas- ing degree of hispidity through the Albian is typical of all the species described here with the exception of H. planispira. However, the above descriptions and those of Glaessner (1966) are at some variance with those of Longoria (1974) who states that "... in H. infracretacea, the last chamber is ovoid, generally smaller than the pen- ultimate in umbilical view and is in the same plane as other chambers of the last whorl ; whereas with H. delrioensis the last chamber is spherical and protrudes towards the umbilicus . . .’. Both Glaessner (1966), and the writer apply these descriptions to the species H. delrioensis and H. infracretacea respectively, i.e. they should read vice versa as stated in original definition. Thus the writer suggests that H. infracretacea is distinct from H. delrioensis on the additional morphological evidence provided above EXPLANATION OF PLATE 61 S.E.M. photographs. Figs. 1-3. Hedbergella briuonensis Loeblich and Tappan, U.C.L. 325-327, Stoliczkaia dispar Zone, Schoonebeek, Netherlands, x 70. Figs. 4-6. Hedbergella delrioensis (Carsey), U.C.L. 328-330. 4, 5, niobe Subzone. 6, varicosum Subzone, Copt Point, Folkestone, south-east England. 4, 5, x 105; 6, x85. Figs. 7-9. Hedbergella infracretacea (Glaessner), U.C.L. 331-333. 7, 8, niobe Subzone. 9, varicosum Subzone, Copt Point, Folkestone, south-east England. 7, 8, x 120; 9, x90. Figs. 10-12. Hedbergella planispira (Tappan), U.C.L. 334-336, orbignyi Subzone, Copt Point, Folkestone, south-east England, x 150. PLATE 61 PRICE, HedhergeUa 524 PALAEONTOLOGY, VOLUME 20 and corroborated by Glaessner (1966). Also the former species is not a chrono- subspecies of H. delrioensis, but formed the root stock and primitive hedbergellid parent from which H. delrioensis arose. Longoria (1974) records ‘//. delrioensis' stratigraphically earlier than ‘‘H. infracretacea in the Aptian, and it is therefore possible that the latter arose from the former at this level, i.e. H. delrioensis arose from H. infraeretaeea. Unfortunately, Longoria illustrates H. infracretacea s.s. with only one view, namely that of its umbilical side. Therefore other specimens identified as H. delrioensis by Longoria but possessing characteristic features of H. infracretacea have been placed in synonymy of the latter as given. Magniez-Jannin (1975) has also suggested that H. delrioensis arose from H. infracretacea, but around the Lower to Middle Albian boundary. However, there is now doubt on this hypothesis, as from her work with Damotte (1973) on the Lower Aptian of the Aube, France, they figure both forms all nevertheless identified as H. infracretacea but listed by the present writer separately in the synonymies above. However, the writer would agree with Magniez-Jannin that H. delrioensis arose from H. infracretacea although probably in the Aptian as ‘suggested’ by Longoria (1974). The derivation and first appearance of early hedbergellid species is outside this discussion. However, an examination of this genus from its first appearance in the Upper Hauterivian, see Longoria (1974) or within the Lower Barremian, see Bartenstein and Bettenstaedt ( 1 962), is the subject of current research. Within the Albian, Magniez-Jannin (1975) states that H. infracretacea is not very common relative to other planktonic species. The writer has found this to be the case in the Lower and Middle Albian, however, during the Upper Albian it becomes common at certain horizons and reaches its acme in the auritus Subzone prior to its extinction around the rostratum-perinflatum boundary. Both Hart (1973a) and Magniez-Jannin (1975) agree on its extinction of this level. However, Gawor-Biedowa (1972) records the species ranging into the Cenomanian of Poland, but examination of her figured specimens show them to be H. delrioensis, as listed in synonymy. The gradual size increase of both H. delrioensis and H. infracretacea through the Albian is a well-marked feature of their development, whilst the abundance of the former species increases within the Cenomanian. The first occurrence of H. brittonensis in the auritus Subzone is coincident with H. infracretacea reaching its acme. This species is more common in the Lower Cenomanian chalk, which was examined by the writer in the Netherlands and north- west Germany. Hart (1970) has suggested that H. brittonensis is merely a high-spired H. delrioensis. However, the very high spire of the former as described by Loeblich and Tappan (1961) is a major feature of this species, it being much higher than high- spired specimens of H. delrioensis. Also, H. delrioensis although showing a gradation in height of trochospire still possesses a wide last whorl with a globular to ovoid ultimate chamber. The writer suggests that H. brittonensis possibly evolved from H. infracretacea as it possesses all the major morphological features of the latter species with regard to its Upper Albian development. The major difference which characterizes H. brittonensis is its very coarse hispidity and large size in comparison with H. infracretacea. Also it normally has two or two and a half visible whorls as compared with H. infracretacea which has one and a half visible whorls. These suggestions are now supported by Carter and Hart (in press). PRICE; ALBIAN FORAMINIFERIDA 525 The stratigraphical level at which H. planispira evolved in the Lower Cretaceous is difficult to determine due to the very small number of specimens recorded from horizons within the Aptian and Lower Albian. It does not occur in large numbers until the Middle Albian. Longoria (1974) records the species from the Lower Aptian, while the writer has recorded it in the Lower Albian. At these levels it shows a close affinity with early forms of H. delrioensis, and therefore it is probable that H. planispira arose from H. delrioensis within the Aptian, although the exact stratigraphical horizon at which it hrst appears is unknown. The species is quite distinct in that it possesses a planispiral or very low trochospiral coil and is the smallest Albian hedbergellid species. However, it shows a slight size increase from the Middle Albian onwards and becomes extremely abundant in the Upper Albian, where very rarely large individuals are found in an otherwise small-sized population. Its small size is in marked contrast to the now larger H. delrioensis, H. infracretacea, and H. hrittonensis. In the upper S. dispar Zone the species, however, decreases in abundance. In conclusion to the discussion of hedbergellid evolution within the Albian the problematic evolutionary position of 'Hedbergella' washitensis (Carsey, 1926) has not been included within the suggested evolutionary scheme. This is for two reasons. First, the species is a tethyan warm-water form that is only found at periods of hiatus, notably the Middle to Upper Albian, and Lower to Middle Cenomanian boundaries, over north-west Europe. Thus its evolutionary position is uncertain. Secondly, its elevation to new generic status, namely Faviisella washitensis by Longoria (1974) and adopted by van Hinte (1976) would seem to strengthen its exclusion from any evolu- tionary interpretation involving the hedbergellids. This new generic status is, however, still problematic and not discussed here. Acknowledgements. I wish to thank Professor T. Barnard for his supervision and constructive criticism of the original paper, which formed part of a course of study for the degree of Doctor of Philosophy at the University of London. Also the financial support and advice of Robertson Research International Limited is acknowledged from whom the writer received a fellowship award and without whose support the research could not have been undertaken. My sincere and indebted thanks to Dr. H. G. Owen (Palaeontology Section, Br. Mus. Nat. Hist., London) for much help and advice both in the field and laboratory, and for the excellent stratigraphical control given during collection of samples from outcrop. Similarly, I express my thanks to Dr. E. Kemper and Hr. H. Bertram (Bundesanstalt fiir Geowissenschaften und Rohstofife, Hanover) and Dr. P. Destombes (Institut Pasteur, Paris) for their field guidance and advice. I also thank Dr. M. B. Hart (Dept, of Environmental Sciences, Plymouth Polytechnic) for his help and discussion, and together with Dr. R. Walters (B.P. Research and Exploration) for their permission to refer to and quote their unpublished work. I am grateful to Shell Petroleum Company (N.A.M.) for availability of borehole material from the Netherlands. Finally, my thanks to Mr. K. S. Amrit for photography of specimens and Mr. C. F. Stuart for drafting the original figures. REFERENCES BANNER, F. T. and BLOW, w. H. 1959. The classification and stratigraphical distribution of the Globigerinacea. Palaeontology, 2, 1-17. BARNARD, T. and BANNER, F. T. 1953. Arenaceous foraminifera from the Upper Cretaceous of England. Q. Jl geol. Soc. Lond. 59, 173-216. BARTENSTEiN, H. and BETTENSTAEDT, F. 1962. Marine Unterkreide (Boreal und Tethys). In Leitfossilien der Mikropaldontologie, Berlin, 280-281. BERTHELiN, G. 1880. Memoire sur les foraminiferes de I’etage Albien de Montcley (Doubs). Mem. Soc. geol. Fr. (3), 1, 1-84. 526 PALAEONTOLOGY, VOLUME 20 BOLLi, H. M., LOEBLiCH, A. R., JUN. and TAPPAN, H. 1957. Planktonic foraminiferal families Hantkeninidae, Orbulinidae, Globorotaliidae and Globotruncanidae. In loeblich, a. r. jun. et al. (eds.). Studies in Foraminifera. Bull. U.S. nat. Mus. 215, 3-46. BROTZEN, F. 1942. Die Foraminiferengattung Gavelinella nov. gen. und die systematik der Rotaliformes. Sweden Ser. Geol. Unders., Avh., Stockholm, ser. C, 451 (arsb. 36 (8)), p. 50. BURROWS, R., SHERBORN, c. D. and BAILEY, T. 1890. The foraminifera of the Red Chalk of Yorkshire, Norfolk and Lincolnshire. Jl R. microsc. Soc. 2, 549-566. CARSEY, D. o. 1926. Foraminifera of the Cretaceous of central Texas. Texas Univ. Bull. 2612, 1-56. CARTER, D. J. and HART, M. B. (in press). Aspects of mid-Cretaceous stratigraphical micropalaeontology. Bull. Br. Mus. nat. Hist. (Geol.). CASEY, R. 1961. The stratigraphical palaeontology of the Lower Greensand. Palaeontology, 3, 487-621. CHAPMAN, F. 1892. The foraminifera of the Gault of Folkestone. Jl R. microsc. Soc. 3, 319-330; 4, 749-758. CUSHMAN, j. A. 1936. New genera and species of the families Verneuilinidae and Valvulinidae and of the subfamily Virgulininae. Cushman Lab. Foram. Res. Spec. Publ. 6, 27-28. 1937. A monograph of the foraminiferal family Valvulinidae. Ibid. 8, 34-44. DAMOTTE, R. and MAGNiEZ-JANNiN, F. 1973. Ostracodes et foraminiferes de I’Aptien inferieur du sondage du Bois du Perchois (Aube). Bull, d' Inform, des geol. du Bassin de Paris, 36, 3-47. ELLIS, B. F. and MESSINA, A. R. 1951 et seq. Catalogue oj Foraminifera, suppl. 3, Am. Mus. Nat. Hist. New York. FUCHS, w. and stradner, h. 1967. Die Foraminiferenfauna und Nannoflora eines Bohrkernes aus dem hoheren Mittel-Alb der tiefbohrung Delft 2 (NAM), Niederlande. Jb. geol. Bimdesanst. Wien, 110, 245-341. GAWOR-BiEDOWA, E. 1969. The genus Arenobulimina Cushman from the Upper Albian and Cenomanian of the Polish lowlands. Roczn. pol. Tow. geol. 39, 73-102. 1972. Albian, Cenomanian and Turonian foraminifera of Poland and their stratigraphical importance. Acta. Palaeont. pol. 17, 1-155. GLAESSNER, M. F. 1937. Plankton foraminifera aus der Kreide und ihre stratigraphische bedeutung. Moscow Univ. Lab. Paleont., Studies in Micropal. 1/1, 27-46. 1966. Notes on the foraminifera of the genus Hedbergella. Eel. geol. Helv. 59, 179-184. HART, M. B. 1970. The distribution of the foraminiferida in the Albian and Cenomanian of south-west England. Unpublished Ph.D. thesis, Univ. of London. 1973u. A correlation of the macrofaunal and microfaunal zonations of the Gault clay of southeast England. In casey, r. and rawson, p. f. (eds.). The Boreal Lower Cretaceous. Geol. Jl Spec. Issue, 5, 267-288. 19736. Foraminiferal evidence for the age of the Cambridge Greensand. Proc. Geol. Assoc. 84, 65-82. HOFKER, J. 1961. The gens Globigerina cretacea in northwestern Europe. Micropaleontology, 7, 95-100. KELLER, B. M. 1935. Microfauna der oberen Kreide des Dnjepr Donez-Beckens und einiger angrenzender gebiete (Russian with German summary). Soc. Nat. Moscow Bull. 43 (sect. geol. 13 (4)), p. 552. KHAN, M. H. 1950. On some new foraminifera from the Lower Cretaceous of Folkestone, Dunton Green and Sevenoaks. Jl R. microsc. Soc. 3, 268-279. LOEBLICH, A. R., JUN. and TAPPAN, H. 1961. Crctaccous planktonic foraminifera part 1. Cenomanian. Micropaleontology, 7, 257-304. 1964. Sarcodina chiefly ‘Thecamoebians’ and Foraminiferida. In moore, r. c. (ed.). Treatise on invertebrate paleontology, pt. C, Protista 2, 1, Cl-510a; 2, C51 1-900. New York, Geol. Soc. Amer. 1974. Recent advances in the classification of foraminiferida. In hedley, r. h. and adams, c. g. (eds.). Foraminifera, 1, 1-53. LONGORIA, J. F. 1974. Stratigraphic, morphologic and taxonomic studies of Aptian planktonic foraminifera. Rev. Espan. de Micro, extraordinaro. 107 pp. MAGNIEZ-JANNIN, F. 1975. Les foraminiferes de I’Albien de I’Aube. Paleontologie, Stratigraphie, Ecologie. Cah. Paleont. 351 pp. MALAPRis, M. 1965. Les Gavelinellidae et formes affines du gisement Albien de Courcelles (Aube). Rev. Micropaleont. 8, 131-150. MALAPRis-BizouARD, M. 1967. Les Lingulogavelinelles de I’Albien inferieur et moyen de I’Aube. Ibid. 10, 128-150. PRICE: ALBIAN FORAMINIFERIDA 527 MALAPRis, M. and JANNiN, F. 1967. Utilisation du microscope electronique a balayage dans I’etude des foraminiferes. C.r. Acad. Sci., Paris, ser. D, 264, 247-249, MASLAKOVA, N. I. 1963. K. sistcmatike roda Hedbergella. Paleont. Zh. 4, 112-116. MICHAEL, E. 1966. Die evolution der Gavelinelliden (Foram. ) in der n.w. deutschen Unterkreide. Senckenherg. Lc//;. 47, 411-459. MOULLADE, M. 1966. Etude stratigraphique et micropaleontologique du Cretace inferieur de la ‘fosse vocontienne’. These Doct., Doc. Lab. geol. Fac. Sci. Lyon. 15, 1-369. NEAGU, T. 1965. Albian foraminifera of the Rumanian plain. Micropalaeontology, 11, 1-38. ORBiGNY, A. d’. 1840. Memoire sur les foraminiferes de la craie blanche du Bassin de Paris. Soc. geol. Fr. Mem. (4), 1, 240 pp. OWEN, H. G. 1971fl. Middle Albian stratigraphy in the Anglo-Paris Basin. Bull. Br. Mus. nat. Hist. (Geol.), 8, 1-164. 19716. The stratigraphy of the Gault in the Thames Estuary and its bearing on the Mesozoic tectonic history of the area. Proc. Geol. Assoc. 82, 187-207. 1972. The Gault and its junction with the Woburn sands in the Leighton Buzzard area, Bedfordshire and Buckinghamshire. Ibid. 83, 287-312. 1975. The stratigraphy of the Gault and Upper Greensand of the Weald. Ibid. 86, 475-498. PRICE, R. J. 1975. Biostratigraphy of the Albian foraminifera of north-west Europe. Unpublished Ph.D. thesis Univ. of London. (in press (a)). Palaeoenvironmental interpretations in the Albian of western and southern Europe, as shown by the distribution of selected foraminifera. Maritime Sediments Spec. Publ. (eds. SCHAFER, c. t. and PELLETIER, B. R.), 1st Int. Symp Benthonic Foraminifera, 1975, Halifax, Nova Scotia, Canada. (in press (6)). The stratigraphical zonation of the Albian sediments of north-west Europe, as based on foraminifera. Proc. Geol. Assoc. REUSS, A. E. 1844. Geognotische skizzen aus bohmen; II-Die Kreidegebilde des westlichen bohmens, einmonographischer. Prague C.W. Medan, 2, 1-215. 1863 (1862). Die Foraminiferen des norddeutschen Hils und Gault. Denkschr. K. Adad. Wiss. Wien. Math. nat. Kl. 62, 445-493. TAPPAN, H. 1940. Foraminifera from the Grayson Formation, Texas. J. Paleont. 14, 93-126. TEN DAM, A. 1950. Les foraminiferes de I’Albien des Pays-Bas. Mem. Soc. geol. Fr. (29), 63, 1-66. VAN HiNTE, J. E. 1976. A Cretaceous time scale. Bull. Am. Ass. Pet. Geol. 60, 498-516. WALTERS, R. 1958. Investigations of the Albian foraminifera from south-east England. Unpublished Ph.D. thesis, Univ. of Wales, Aberystwyth. R. J. PRICE Robertson Research (North America) Ltd. 501 Cleveland Crescent S.E. Calgary, Alberta T2G 4R8 Canada Typescript received 9 February 1976 Revised typescript received 27 August 1976 • Vi. '■ V « I ' w; ' -m ,•■ -v: >■' J ■ REVISION OF THE ORDOVICIAN CARPOID FAMILY lOWACYSTIDAE by DENNIS R. KOLATA, HARRELL L. STRIMPLE and CALVIN O. LEVORSON Abstract. Newly discovered specimens and re-evaluation of previous evidence indicate a much closer relation between the solutan carpoids Belemnocystites, Myeinocystites, Scalenocystites, and lowacystis than was previously suspected. Comparative studies of all known species, including observations on the ontogeny of 5. strimplei Kolata and I. sagittaria Thomas and Ladd, show that numerous thecal and steleal structures are homologous. In light of the obvious affinity shown by these carpoids, it is proposed that the Family Belemnocystitidae (Belemnocystites, Myeino- cystites, and Scalenocystites) be synonymized with the Family lowacystidae (lowacystis). The likely synonymy of Belemnocystites and Myeinocystites is suggested from a re-examination of the holotype of B. wetlierbyi Miller and Gurley. All species are redescribed and illustrated. A new species, M. crossmani, is described from the Trentonian (Caradocian) Dunleith Formation (Galena Group) of Illinois and Iowa. The dorso-ventrally depressed theca, high degree of bilateral symmetry, anterior mouth, and flexible, caudal appendage suggest that the iowacystids were vagrant bottom-dwelling echinoderms that were adapted to a browsing mode of life. They very likely lived with the oral opening and ambulacral groove facing the substrate. The iowacystids inhabited warm, shallow epeiric seas in environments characterized by relatively quiet deposition of carbonate sediments. Carpoids of the Order Soluta (Class Homoiostelea) are rare fossil echinoderms that occur in rocks ranging in age from the Upper Cambrian to the Lower Devonian. They are characterized by a depressed theca that bears a single exothecal arm and a caudal appendage (stele) composed of axially differentiated plates. The body plan is essentially bilaterally symmetrical, with the arm and stele lying at or near the axial plane at opposite ends of the theca. The iowacystids are a family of solutan carpoids at present known only from the Champlainian and Cincinnatian carbonate facies of North America. They are unique among the Soluta in possessing differentiated thecal plates that have a thick, rigid aboral face, a thin, apparently flexible oral face with a non-marginal arm, and a specialized stele in which the mesistele is undifferentiated from the dististele. The Family lowacystidae was formerly represented by the single species lowacystis sagittaria Thomas and Ladd. However, study of many new specimens and re-evaluation of previous evidence indicates a much closer relation with three other solutan genera, Belemnocystites, Myeinocystites, and Scalenocystites, than was previously suspected. Comparative studies of all known species show that numerous thecal and steleal structures are homologous. Because of the strong aflinity shown by these carpoids it is proposed that the Family Belemnocystitidae, including Belemno- cystites, Myeinocystites, and Scalenocystites, be synonymized with the lowacystidae. In light of the new information, all species are redescribed and illustrated, including one new species of Myeinocystites. TERMINOLOGY Terminology for symmetry, orientation, and morphology in this investigation in general follows the Treatise on Invertebrate Paleontology (Caster 1968, p. S584). [Palaeontology, Vol. 20, Part 3, 1977, pp. 529-557, pis. 62-64.] 530 PALAEONTOLOGY, VOLUME 20 Problems arise, however, in selecting proper terms for the two thecal surfaces or faces. Caster (1968, p. S583, fig. 372) designated the thecal surfaces according to an inferred habitus, and used obverse, brachial, and carapace as synonyms for the upper surface and reverse, antibrachial, and plastron as synonyms for the lower surface. (Caster employed brachial and antibrachial to refer to the thecal faces whereas Bather 1913, p. 373, originally used the terms to refer to the sides of the theca right or left of the symmetry plane.) Elsewhere Parsley and Caster (1965, p. 114) and Parsley (1972, p. 342) applied the terms ‘dorsal’ and ‘vertraP to the two thecal surfaces in the North American solutan genera. In most solutes, including the lowacystidae, the habitus suggested above requires the arm to lie on the upper surface away from the substrate, thus suggesting a passive suspension feeding mode of life. Such a mode of life, however, is not substantiated by the flatfish-like body that exhibits a high degree of bilateral symmetry, an anterior (distal) mouth, and a posterior (proximal), flexible, caudal appendage. These morphologic features strongly suggest a vagile browsing existence (Kolata 1973, p. 973). Inasmuch as the true habitus is unknown, we prefer to use the strictly descriptive terms oral and aboral to refer to the two thecal faces. The oral thecal face is that surface on which the mouth is located. It is also the thecal face on which the ambulacral groove, at the base of the arm, is exposed when the cover plates are open. In the iowacystids it is the surface from which the arm emerges. The aboral face is opposite the oral face. To show the homologous features within the Belemnocystitidae, Parsley (1972, p. 342) proposed a system of nomenclature for thecal plates that is similar in part to that used for the stylophoran mitrate carpoids (Ubaghs 1968, p. S499) and is in part a modification of the system used by Thomas and Ladd (1926) for lowacyslis. The nomenclature is very useful in comparative studies of solutan carpoids. Some changes, however, are needed to describe the significant morphologic features in the simplest, clearest manner. First, as mentioned above, the designation of dorsal and ventral thecal plates (Dl, D2, VI, V2, and so on) should be avoided. The more objective terms aboral and oral should be substituted (Al, A2, Ol, 02, and so on). Secondly, nomenclature for the marginals is so similar to that used for the mitrate carpoids that there is some risk in confusing homoeomorphy for homology. In addition. Parsley’s (1972, p. 343, text -fig. 1 ) marginal M 1 is based solely on Wetherby’s (1881) questionable drawing of an anomalous solute that is very much different from known solutan carpoids. A more desirable plan would be to designate the marginal plates Ml, M2, M3, and so on, beginning with the right lateral adsteleal plate (aboral face up) and counting clockwise to the first anal plate (text-fig. 1). For descriptive purposes the carpoids discussed herein are oriented with the arm at the anterior end and pointing upwards on the page. Caster’s (1968, p. S583) restrictions on the terms ‘right’ and ‘left’ are not followed in this discussion. MORPHOLOGY The iowacystids possess differentiated thecal surfaces, one side (aboral) of which consists of thick, regular plates that form a rigid frame to the theca. The base of the arm is relatively far from the margin of the theca and is surrounded by three or four KOLATA, ET AL.: ORDOVICIAN CARPOIDS 531 TEXT-FIG. 1 . lowacystid morphology and terminology based on lowacystis sagittaria Thomas and Ladd, 1 926. a, aboral face, and b, oral face, showing revised thecal plate nomenclature, c, transverse section of the theca showing the relatively thick aboral plates (upper surface) and nature of contact with thinner, more numerous oral plates (lower surface). Approx, x 1-5. distinct plates, one of which has a poriferous cone-shaped structure generally interpreted as the hydropore. The stele differs from that of most solutan carpoids in having only two parts instead of three, the dististele being undifferentiated from the mesistele. D 532 PALAEONTOLOGY, VOLUME 20 Theca. Like other solutan carpoids, the iowacystids have a depressed theca consisting of a mosaic of plates. Thecal outlines vary from irregularly oval to trigonal, depend- ing in part on the stage of ontogeny. In cross-section the oral face is planate to slightly convex and the aboral side is convex. The position of the stele and arm along the longitudinal axis at opposite ends of the theca imparts a high degree of bilateral symmetry, but the oral-anal axis does not correspond with the axial plane as it does in most animals possessing primary bilateral symmetry. Thecal plate patterns, also, are not bilateral. The aboral face consists of thick, tightly sutured plates that form a rigid carapace to the theca. The plates of the iowacystids are arranged in a characteristic pattern and are readily homologized. The marginal series typically consists of eleven regular plates, including the adsteleal plate (0-M2) of the oral face and excluding the anal series (text-fig. 1). Enclosed within the marginal series are regular somatic plates, typically four in number: the A1 in an anterior position, A2 and A3 centrally located with the suture between them lying on or near the axial plane, and A4 located between A3 and the anal plates. Variations occur in the aboral thecal plates, but homologies can easily be inferred from size, shape, and position in relation to surrounding plates. The adsteleal plates are noteworthy in that they form the frame around the stele. Four marginal plates, including the Ml, A-M2, 0-M2, and M3, form a rigid girdle with a circular to slightly eliptical (in extensiplane) foramen. A marginal flange encircles the foramen and extends out over the first proxistele tetramere. The first tetramere was probably attached by connecting tissue to the recessed surface inside the marginal flange. The oral face of the theca bears the hydropore, arm, and subthecal mouth. Plating is mosaic, with firm sutures between the anterior plates, particularly the adbrachials; the other plates are relatively thin and apparently had integumentary junctures that provided some flexibility to the oral face. The hydropore is invariably located immediately left (oral face up) of the arm, on adbrachial plate Ol. It consists of one or more pores at the top of a cone-shaped tubercle. The subthecal mouth is located at the base of the arm, within a small vestibule formed by the adbrachial plates. The anus is located in the left (oral face up) proximal corner along the thecal margin, between marginals Ml and MIO. Its presence is marked by two quarter- sphere plates that opened along the extensiplane. Additional small, quadrangular adanal plates encircle the valvate quarter-spheres in lowacystis and Scalenocystites. Arm. The single arm is a tapering, unbranched appendage consisting of biserial brachial platelets that curve around the ambulacral groove and smaller biserial platelets that serve as cover platelets (text-fig. 2). Arm length varies from one individual to another but commonly is as long or slightly longer than the theca. Although the arm bears a striking resemblance to some cystoid brachioles, it differs fundamentally in that it is an extension of the body cavity rather than a solid serial skeleton. Whereas cystoid brachioles are mounted on plates outside of the thecal wall, the solutan arm is supported by plates that surround a foramen that opens directly into the body cavity. The exothecal nature of the arm suggests that the nervous, hemal, and water- vascular systems may have extended into the distal portions as they do in the arm of KOLATA, ET AL.\ ORDOVICIAN CARPOIDS 533 TEXT-FIG. 2. Morphology of iowacystid arm based on Scalenocys1itesstrimplei¥^o\&\.-d, 1 973. A, B, aboral and oral views of arm, respectively, showing brachial platelets and cover platelets, c, cross-section of arm. Approx. X 8. TEXT-FIG. 3. Proxistele morphology, based on Scaleno- cystites strimplei Kolata, 1973, a, aboral view. B, diagram- matic longitudinal section of three imbricated, partial tetramere rings. Approx, x 10. bourrelet e — c a a crinoid. A single radial water-vascular canal probably rested within the ambulacral groove. The cover platelets very likely could be opened to allow protraction of tube- feet (Nichols 1972, p. 530). Stele. Unlike most solutan carpoids that possess a tripartite stele differentiated into a proxistele, a mesistele, and a dististele, the iowacystids (not confirmed in Belemno- cystites) are characterized by a two-part structure consisting of a proxistele with telescopically imbricated tetramere rings and an undivided distal stele. Plate organiza- tion typical of a mesistele persists through all of the distal stele. (In order to avoid the homologous inferences of the terms ‘dististele’ and ‘mesistele’ in the following discussion, the less-restricted term ‘distal stele’ will be used to refer to all of the stele that is distal to the proxistele.) The proxistele is round to slightly elliptical in tranverse section and consists of from five to ten tetramere rings that enclose a large central lumen. Each tetramere consists of a thickened ring (bourrelet) with a thin rim that imbricates within the proximally adjacent ring (text-fig. 3). The rim of the first tetramere fits snugly into the recessed edge of the foramen formed by the adsteleals. The juncture between the proxistele and distal stele is abrupt. The distal stele is essentially a biseries of thick polygonal plates that enclose a small central lumen that extends to the distal tip of the stele. The biseries is most evident on the oral side but is interrupted along the medial portion of the aboral side by small intercalate plates that increase in number towards the distal tip. 534 PALAEONTOLOGY, VOLUME 20 PHYLOGENY Morphologic traits possessed by the ancestral iowacystid stock can be inferred by comparing the four known genera. The presence of well-differentiated thecal faces in these genera, for example, strongly suggests that this morphologic character was present in the ancestor. In addition, a high degree of regularity in the aboral somatic and marginal plates was most likely well established. Regularity of the adbrachial plates would also be expected. The remaining oral face plates, however, were prob- ably relatively numerous and irregular in size and shape. The characteristic distal stele with mesistele undifferentiated from the dististele is also considered to have been present in the ancestor. Perhaps Scalenocystites (Trentonian Stage of Middle Ordovician), with its asymmetric theca and numerous irregular oral somatic plates is most like the iowa- cystid ancestor. Although Myeinocystites (Blackriveran Stage of Middle Ordovician) is known from slightly older strata, the relatively few, regular plates on its oral face seem to be of a specialized character. Scalenocystites is judged to be of, or close to, the lineage that led to lowacystis (Cincinnatian Stage of Upper Ordovician). Both genera have similar thecal outlines, oral face organization, and marginal ornament. lowacystis is more advanced than Scalenocystites, possessing a higher degree of bilateral symmetry, a more complex system of nodes, cusps, and ridges on the marginals, and fewer axial intercalates at the juncture between the proxistele and distal stele. PALAEOECOLOGY The iowacystid carpoids occur in argillaceous limestone and dolostone that consist of whole and broken, unabraded, occasionally articulated, shelly invertebrates ‘floating’ in a fine-grained matrix. The rocks, for the most part, lack any evidence of strong currents and appear to have been formed in environments that were relatively far from major sources of terrigenous sediment. The iowacystids are typically associated with an abundant and diverse invertebrate fauna consisting largely of brachiopods, bryozoans, molluscs, trilobites, and other echinoderms. The random orientation of shelly debris and the lumpy, irregular beds indicate extensive biogenic activity due to scavengers and burrowers that reworked the sediment prior to lithifica- tion. The iowacystids lived in warm, shallow epeiric seas in environments charac- terized by relatively quiet deposition of carbonate sediments and with in situ accumulation of shelly debris. The morphology of the iowacystids suggests that they were vagrant organisms, probably able to scull across the sea bottom by means of the caudal appendage (Parsley 1972, p. 347; Kolata 1973, p. 973). The telescopically imbricated proxistele tetrameres indicate that this part of the stele was quite flexible and capable of move- ment in all directions. The relatively large proxistele lumen probably contained muscles that facilitated movement of the stele (Caster 1968, p. S594). In contrast to the proxistele, the distal stele was a relatively stiff structure, consisting of thick, closely appressed (tesselate) plates. It does not appear to have had prehensile capability and very likely was not employed as a holdfast. A vagrant mode of life is further KOLATA, ET AL.: ORDOVICIAN CARPOIDS 535 suggested by the depressed, trigonal to oval thecae, bilateral symmetry, anterior mouth, and posterior anus, which is a recurrent body plan in animals that seek out their food. lowacystid morphology appears to have been well adapted to the hydro- dynamic requirements of a bottom-moving flatfish-like existency (text-fig. 4). The normal living position of the iowacystids was probably with the carapace- like aboral face in the dorsal position and the thinner, flexible, oral surface facing the substrate (Kolata 1973, p. 973). In that position, the thick, pustulose plates of the aboral face would have provided maximum protection for the body. In addition, the arm, with its food groove facing the substrate, could have been used to browse on the accumulation of organic debris on the substrate rather than to wait passively for food-bearing currents to bring nutrients to the animal. A similar orientation and mode of life has been suggested for homoeomorphs of the lowacystidae, such as the cystoids Amecystis (Broadhead and Strimple 1975) and Pleurocystites (Paul 1967). TEXT-FIG. 4. Reconstruction of Middle Ordovician sea floor showing inferred life mode of Scalenocystites strimplei Kolata, 1973. Although the iowacystid carpoids are very rare fossils, they are sometimes found in clusters on bedding planes, suggesting a gregarious habit during life. This has been noted in the occurrence of Scalenocystites from the Dunleith Formation (Galena Group) of Minnesota and lowacystis (PI. 63, fig. 1) from the Fort Atkinson and Scales Formations (Maquoketa Group) of Iowa. Specimens of Myeinocystites crossmani n. sp. from the Dunleith Formation near Rockton, Illinois, were found in an unusually diverse cluster of echinoderms that included cystoids {Pleurocystites), crinoids {Carabocrinus, Cupulocrinus, and Glyptocrinus), edrioasteroids (Edrioaster), 536 PALAEONTOLOGY, VOLUME 20 cyclocystoids {Cyclocystoides), and echinoids (Neobothriocidaris) (Kolata 1975). The cluster occurred on a single bedding plane in an area of approximately 2 sq. ms. M. crossmani n. sp. was found with a similarly diverse cluster of echinoderms in the Dunleith Formation near Burr Oak, Iowa. SYSTEMATIC DESCRIPTIONS AND DISCUSSION Phylum ECHINODERMATA Fleming, 1828 Subphylum homalozoa Whitehouse, 1941 Class HOMOIOSTELEA Gill and Caster, 1960 Order soluta Jaekel, 1901 Family iowacystidae Gill and Caster, 1960 (Belemnocystitidae Parsley, in Caster 1968; in part) Genera. lowacystis Thomas and Ladd, 1926; Belemnocystites Miller and Gurley, 1894; Myeinocystites Strimple, 1953; Scalenocystites Kolata, 1973. Emended diagnosis. Oval or trigonal, depressed theca with dilferentiated thecal faces; basically asymmetric theca with well-developed bilateral symmetry. Aboral face composed of relatively few, thick, tightly sutured plates with large marginals that envelope edges forming a rigid frame to the theca; convex near centre, concave near edges; aboral plates readily homologized within the family. Oral face composed of a mosaic of thin thecal plates of varied size, shape, and number; integumentary junctures near the centre of the face. Oral face bears single exothecal arm consisting of two matching but unequal biseries of platelets; base of arm located proximal to anterior margin and emerges from thecal face; base of arm typically enclosed by three plates, one of which possesses a perforate cone-shaped tubercle generally regarded as the hydropore. Anus located at left (oral face up) proximal margin of theca; closed by bivalved boss. Pustulose ornament on aboral face generally coarser than that on oral face. Four firmly sutured adsteleal plates form a rigid girdle around the stele. Stele round to slightly depressed; proxistele consists of five to ten tele- scopically imbricated tetramere rings; axial intercalates on aboral side of distal stele; mesistele undifferentiated from dististele. Remarks. Thomas and Ladd (1926) described I. sagittaria from the Cincinnatian (Upper Ordovician) Maquoketa Group of north-eastern Iowa and provisionally assigned it to the stylophoran Anomalocystitidae, adding. The genus may eventually be relegated to a new family’. Bather (1926, pp. 233-234; 1928, pp. 5-7), however, rejected Thomas and Ladd’s classification and properly noted its solutan affinities, stating (1926, p. 234), \ . . that it is a Dendrocystis [^/c] at about the same level of evolution as D. seotia though on different lines’. Although some attempt was subse- quently made to resurrect the name lowaeystis (Dehm 1934, p. 21), it was considered to be a synonym of Dendrocystites by most authors until Gill and Caster (1960, pp. 20-22) redefined the genus and proposed the Family Iowacystidae to receive the single species. Gill and Caster (1960, p. 21) considered the depressed theca with differentiated ‘anal and antianal surfaces’, trigonal outline, and arm attachment on the thecal face rather than on the distal margin to be specialized features that clearly KOLATA, ET AL.: ORDOVICIAN CARPOIDS 537 marked the family olf from other solutan carpoids. When the type specimens of I. sagittaria were re-examined by Parsley and Caster (1965), several details were added to the specific description. Additional discussion of the comparative morpho- logy was given by Caster (1968). Wetherby (1881, p. 177) briefly described and illustrated with drawings an apparent solute from Trentonian (Middle Ordovician) rocks of Kentucky. He designated the single specimen, ‘Cystidean, New Genus and Species’, but hesitated to carry the taxonomy further because of the lack of study material. His two drawings (oral and aboral views of the theca) show an oval-shaped theca approximately 22 mm in length that has a small arm on the oral face and a portion of an apparent ‘proxistele’ attached to one end. The pattern of thecal plates on the aboral face bears a strong resemblance to iowacystid genera, except for an anomalous thecal plate that is shown at the juncture with the stele. Furthermore, the ‘proxistele’ is shown to taper abruptly (fifteen holo- merous segments) to one-half its diameter at a distance of 10 mm from the juncture with the theca. This is unusual because in well-preserved solutes the proxistele invariably consists of tetrameres that taper very little distally. Recent attempts to locate the Wetherby specimen have been unsuccessful, and it has been generally assumed by many investigators to be lost. Miller and Gurley ( 1 894, p. 9) described and illustrated a single specimen from Trentonian rocks of Kentucky and assigned it to a new genus and species, Belenmo- cystites wetherbyi (specific appelation in honour of A. G. Wetherby), referring it to the stylophoran family Anomalocystitidae. The specimen (holotype FMNH UC 6046; Field Museum of Natural History, University of Chicago) is remarkably similar in size and shape to the specimen described by Wetherby (1881) (text-fig. 5). In fact, when the two drawings are superimposed, the outlines correspond almost exactly, except that the Miller and Gurley specimen lacks the extra adsteleal plate and terete, holomerous proxistele that make the Wetherby specimen so anomalous. In the generic description Miller and Gurley (1894, p. 9) stated, ‘Column comparatively large composed of thin plates and taper- ing as in Steleocystites', but they do not illustrate the column. This suggests that they either studied an isolated fragment or relied on the Wetherby drawings for information. The unusual adsteleal plate and ‘proxistele’ shown by Wetherby may have been an isolated fragment (possibly the proximal stem and thecal plate of a glyptocystitid cystoid) that was assumed to be part of the solutan theca. Miller and Gurley did not mention who collected the specimen or how it was obtained, and it seems likely that they merely redescribed Wetherby’s specimen and assigned A B C D TEXT-FIG. 5. Photographs of a, aboral face, and b, oral face of a specimen, illustrated by Wetherby ( 1881, pi. 5, fig. 2, 2a) and named ‘New Genus and Species’. C-d, Belemnocystites wetherbyi Miller and Gurley, 1894, photographs of aboral and oral faces of the holotype (FMNH UC 6046) illustrated by Miller and Gurley (1894, pi. 1, figs. 5 and 6). x 1. 538 PALAEONTOLOGY, VOLUME 20 a name to it. If this is so then the Wetherby specimen is in fact the holotype (FMNH UC 6046) of B. wetherbyi. Parsley {in Caster 1968, p. S623) recognized the solutan affinities of Belemnocystites and referred it to the new Family Belemnocystitidae of the Order Soluta. Unfortunately, the paucity of study material forced Parsley to rely heavily on Wetherby’s (1881, pi. 5, figs. 2, 21) drawings in order to define the taxobasis of the new family. The extra adsteleal plate and unusual holomerous stele were regarded as valid features of this monotypic family. Parsley {in Caster 1968, p. S623) also recognized that Belemnocystites bears several traits in common with lowacystis, including ‘configuration, location and interrelationship of the arm and pore plate, unusual somatic biconvexity of the theca, and similar nature and symmetry of the ventral somatic plates, including what appears to be an azygous adanal plate’. Later, in a paper concerning the homeomorphy between the solutan Belemno- cystitidae and the stylophoran Anomalocystitidae, Parsley (1972, p. 341) assigned Myeinocystites natus Strimple (1953) from the Middle Ordovician of Oklahoma and Tennessee to the Belemnocystitidae. (Strimple 1953, p. 105, had previously assigned M. natus to the stylophoran Anomalocystitidae.) Parsley (1972, text-fig. 1c-e) again referred to the Wetherby drawing to show the presumed nature of the theca and stele in Belemnocystites. In addition, a topotype of B. wetherbyi was illustrated (Parsley 1 972, pi. 1 , figs. 3, 5-6). This specimen (USNM 1 420 1 ), although silicified, is a complete theca that shows the thecal plate pattern (ibid., pi. 1, fig. 6) and the nature of the adsteleal plates (ibid., pi. 1, fig. 3). The theca is similar to Myeinocystites, Scaleno- cystites, and lowacystis and does not possess the extra adsteleal plate illustrated by Wetherby. It is evident from re-examination of old material and the discovery of many new specimens that the Family Belemnocystitidae, including the genera Belemnocystites, Myeinocystites, and Scalenocystites, shares a great many morphologic features with lowacystis (lowacystidae). Furthermore, the diagnosis of the Family Belemno- cystitidae (Parsley, in Caster 1968, p. S623; Parsley 1972, p. 342) is not sufficiently distinct from that of the lowacystidae (Gill and Caster 1960, p. 20; Caster 1968, p. S620) to require two family-level taxa. In his original diagnosis Parsley {in Caster 1968, p. S623) stated that the Belemnocystitidae were ‘Solutes with regularized marginal and somatic plates ; single, nonterminal, biserial arm with adjacent coniform pore plate. Stele holomerous [the tetramerous nature of the proxistele was later recognized by Parsley 1972, p. 342 in a revised family diagnosis] or apparently so. Characters essentially those of type genus.’ Except for the differences in thecal out- line, these characteristics apply equally well to the Family lowacystidae and, in part, are the basis for differentiating Belemnocystites, Myeinocystites, Scalenocystites, and lowacystis from all other known solutan carpoids. The differences in thecal outline are judged to be important at the generic level but are outweighed on the family level by the obvious homologous thecal and steleal structures that characterize the four genera. It is proposed here that the Family Belemnocystitidae be included in with the lowacystidae. KOLATA, ET AL.: ORDOVICIAN CARPOIDS 539 Genus iowacystis Thomas and Ladd, 1926 Type species. Iowacystis sagittaria Thomas and Ladd, 1926, p. 6. Diagnosis. Isosceles-triangle-shaped thecal outline; thecal faces differentiated; marginal plates possess a thickened rim with prominent arcuate ridges and grooves, particularly on lateral edges; marginal M7 not in contact with somatic A1 unless the latter is compound; oral face plates numerous (about forty) and irregular; base of arm and subthecal mouth enclosed by three regular adbrachial plates ; bivalved anal boss surrounded by small quadrangular adanal plates on both faces; distal stele typically consists of three plates at juncture with proxistele. Iowacystis sagittaria Thomas and Ladd, 1926 Plate 62, figs. 1-12; Plate 63, figs. 1 - 5 ; Plate 64, fig. 10; text-figs. 1,6,7, 8a 1926 Iowacystis sagittaria Thomas and Ladd, p. 6, pi. 1, figs. 1-5; pi. 2, fig. 1; pi. 4, figs. 1-6; pi. 5, figs. 1-2. 1926 Dendrocystis sagittaria (Thomas and Ladd) Bather, pp. 233-234. 1928 Dendrocystis sagittaria (Thomas and Ladd) Bather, pp. 5-7. 1933 Jowacystis [sic] sagittaria Thomas and Ladd, Dehm, p. 65. 1934 Dendrocystites (Iowacystis) sagitarus (Thomas and Ladd), Dehm, p. 37. 1938 Dendrocystites sagittaria (Thomas and Ladd) Bassler, pp. 9, 85. 1941 Dendrocystis sagittaria (Thomas and Ladd) Chauvel, pp. 7, 241. 1943 Dendrocystites Sagittarius (Thomas and Ladd) Regnell, pp. 41, 195. 1960 Iowacystis sagittaria Thomas and Ladd, Gill and Caster, pp. 20-22, 24, 29. 1965 Iowacystis sagittaria Thomas and Ladd, Parsley and Caster, pp. 141-153, pi. 17, figs. 1-8; pi. 18, figs. 1-7. 1968 Iowacystis sagittaria Thomas and Ladd, Caster, p. S620. Type specimens. Thomas and Ladd (1926) designated seven syntypes for I. sagittaria, including SUI 3525- 3528; three stele fragments were catalogued as syntypes SUI 3529-A, -B, and -C. All specimens are in the repository of the Department of Geology, University of Iowa, Iowa City, Iowa. Material. In addition to the syntypes, thirty-three newly discovered specimens also were studied; eighteen are reposited at Iowa City, including SUI 39433-39450. Age. Cincinnatian Series (Upper Ordovician-Caradocian-Ashgillian). Localities. The type specimens are from the Fort Atkinson Formation (bed no. 9 of Parker et al. 1959) of the Maquoketa Group (stratigraphic classification in the Upper Mississippi Valley region after Templeton and Willman 1963) at Fort Atkinson, Winneshiek County, Iowa. In addition, specimens are known from beds 7, 8, and 9 (lower part of Fort Atkinson Formation) of Parker et al. (1959) in a roadcut on the south edge of Fort Atkinson, Winneshiek County, Iowa, at the north centre line. Sec. 10, 96N.-9W., Decorah Quadrangle, and from the same unit 0-5 km south of Elgin, Fayette County, Iowa, SW. corner Sec. 24, 94N.-7W. I. sagittaria is also known from the greyish brown, argillaceous, dolomitic limestone of the Vogdesia Zone, Elgin Member, Scales Eormation, Maquoketa Group at the following localities; roadcut on north side of Winneshiek County Highway B-32, 3-7 km east of Eort Atkinson, Winneshiek County, Iowa, SW. NE. Sec. 15, 96N.-9W., Decorah Quadrangle; quarry located 5-6 km south-east of Ossian, Winneshiek County, Iowa, NE. SW. Sec. 33, 96N.-8W., Decorah Quadrangle; roadcut on west and south sides of curve in road, 8 0 km south of Ossian in Fayette County, Iowa, SW. Sec. 2, 95N.-8W., Decorah Quadrangle; quarry located 9-6 km north of Cresco, Howard County, Iowa, NW. NW. Sec. 24, lOON.- IIW., Mason City Quadrangle; roadcut on south side of road, 4 0 km east of Eldorado, Fayette County, Iowa, NE. NE. Sec. 9, 95N.-8W., Decorah Quadrangle. Diagnosis. Same characteristics as genus. 540 PALAEONTOLOGY, VOLUME 20 Description of adults: Theca. The depressed, sagittiform theca is biconvex in cross- section and possesses differentiated thecal faces. The arm emerges from the oral face near the apex or distal tip of the theca. The arm and stele lie near the principal plane of symmetry accentuating the well-developed bilateral symmetry. The aboral face consists of thick (0-5-0-6 mm) plates that are generally uniform in size, shape, and position. The marginal series typically consists of ten plates (excluding marginal 0-M2 and the anal plates) that form a rigid frame for the theca. The marginal plates form the thecal edges and extend around to the oral face, where they occupy a narrow peripheral band. The marginals are thick (up to 4-0 mm thick) at the edges and carry an inner groove (text-fig. 1 ) that is continuous around the periphery of the theca (visible on oral face). There is a reverse in curvature on the aboral face between the slightly concave marginals and the convex somatic plates. Marginal M4 occupies the left (aboral face up) proximal (posterior) angle of the theca. Marginals M6 and M8 are usually in contact, with the suture between them lying on the plane of symmetry; in some specimens a small somatic plate may lie between the two plates (PI. 62, fig. 1 ; text-fig. 6c). Marginal M7 occupies the distal tip of the theca. Shallow grooves marking the probable sites of muscle attachment are present deep within the foramen along the sides of the Ml and M3 adsteleals (PI. 64, fig. 10). In addition, a triangular apophysis is sometimes present on the inner proximal edge of the A-M2 adsteleal (PI. 62, fig. 9). A marginal flange encircles the foramen and extends out over the proximal feather edge of the first proxistele tetramere. The marginal plates are marked by a series of sharp arcuate ridges that curve around the thecal edges and loop on to the aboral face (PI. 62, figs. 2-4). One of the most prominent ridges passes from the centre of marginal M4 on the oral face around to the aboral face turns sharply at the juncture of M4 and M5 and curves back around to the centre of M5 on the oral face. The looping pattern is repeated on M5, M6, and M7. A similar pattern occurs along the opposite thecal edge between M7, M8, M9, and MIO. Additional nodes, cusps, and secondary ridges occur along the edges EXPLANATION OF PLATE 62 Figs. 1-12. lowacystis sagittaria Thomas and Ladd. 1, aboral face of SUI 39442 photographed under xylol; Elgin Member, Scales Formation (bed no. 4 of Parker et al. 1959), Maquoketa Group, near Eldorado, Iowa, x2-6. 2-4, lateral views of syntype SUI 3526 with aboral face oriented up; 2, right thecal edge showing marginal ornament; position of a possible sutural pore is shown by upper arrow, lower arrow points to hydropore ; 3, left thecal edge showing marginal ornament and basal part of the arm ; 4, anterior or distal end of theca showing position of the arm and hydropore ; Fort Atkinson Formation, Maquoketa Group, Fort Atkinson, Iowa, x 2. 5, oral face of SUI 39434; Elgin Member (bed no. 4 of Parker et al. 1959), Port Atkinson, Iowa, x4. 6, aboral face of SUI 39437; Fort Atkinson Formation, Elgin, Iowa, X 2. 7, oral face of syntype SUI 3525; same locality as figs. 2-4, x 1-8. 8, aboral face of SUI 39448; same locality as fig. 5, x 4. 9, interior surface of adsteleal marginal A-M2 (SUI 39447); note triangular apophysis along proximal edge at arrow; same locality as fig. 5, x 8. 10, oral face of SUI 39435; same locality as fig. 5, x 3-3. 11, oral face of SUI 39433, note knob-like structure on distal stele at arrow; same locality as fig. 1, x 3. 12, adbrachial plate 01 of syntype SUI 3525 showing hydropore tubercle with hydropore at top and several smaller pores (at lower arrows, accented with ink) below; same locality as figs. 2-4, X 10. PLATE 62 hydropore KOLATA et al., lowacystis 542 PALAEONTOLOGY, VOLUME 20 within the prominent arcuate ridges. The remainder of the aboral face, including the somatic plates, is covered by numerous small pustules (PI. 62, fig. 8). A detailed description of the prosopon (ornament) of lowacystis is given by Parsley and Caster (1965, pp. 148-152). The aboral somatic plates tend to vary in number and shape. Homologous plates or groups of plates, however, are readily apparent. The simplest pattern (PI. 62, fig. 8; text-fig. 6a) is characterized by four somatics, including the distal Al, central A2 and A3, and right proximal A4, a pattern that is characteristic of Scalenocystites and Belemnocystites. A common variation of this pattern occurs in specimens (PI. 63, fig. 2; text-fig. 6b) that possess a compound A2, here interpreted as a homologous pair. The more extreme variants (PI. 62, fig. 1 ; text-fig. 6c) possess two homologous pairs, Al and A2 both being compound. The number of somatics apparently is not related to the size or stage of development. In all specimens observed, the homologous plates and pairs of plates can be determined by their size, shape, and relative position. TEXT-FIG. 6. lowacystis sagittaria Thomas and Ladd, 1926, showing homologous aboral somatic plates. A, SUI 39441 ; b, SUI 39439; c, SUI 39442. Approx. x2-5. The oral face consists of approximately forty relatively thin (0-2-0-3 mm thick) plates that are mostly irregular in size, shape, and position. The plates are loosely articulated and were apparently held within a flexible integument. The oral thecal plates are sutured to the marginals along the marginal lip (text-fig. 1). The base of the arm and the subthecal mouth are enclosed by three regular adbrachials, including the Ol, 02, and 03 plates (text-fig. 1). These three plates are generally thicker (0-5-0-6 mm) than the more proximal oral somatics. The adbrachials are tightly sutured to each other as well as to marginals M6, M7, and M8. The Ol plate is sutured to M7 and M8 and possesses a prominent cone-shaped tubercle with an apical pore. The axis of the tubercle is oriented at an oblique angle to the upper left (oral face up), with the pore exposed along the thecal margin. Serial sections show that the pore expands into a cone-shaped lumen within the theca. Several smaller pores are sometimes clustered around the main apical pore (PI. 62, fig. 12) ; these have been described by Thomas and Ladd (1926, p. 10) and by Parsley and Caster (1965, p. 145). A possible sutural pore was observed along the zigzag suture between the Ol plate and marginal M8 in specimens SUI 39448 and SUI 3526 (PI. 62, fig. 2). KOLATA, ET AL.: ORDOVICIAN CARPOIDS 543 Surfaces of the oral somatic plates are covered by numerous small pustules many of which have coalesced into fine radiating ridges (PI. 62, fig. 12). The ridges are particularly well developed on the adbrachials and on the plates in the anal lobe. The anal opening is covered by a pair of tumid, valvate plates that close along the extensiplane. The bivalve apparatus is surrounded by a number of small, loosely articulated, quadrangular adanal plates. A small vestibule within the anal lobe is outlined by the deeply notched sides (visible on the oral face) of marginals M 1 and MIO (PI. 62, fig. 5). The vestibule is covered on the oral face by a number of small, loosely articulated thecal plates. Arm. The arm consists of a large biseries of brachial platelets that carry the ambulacral groove and a smaller biseries of erectile cover platelets (Parsley and Caster 1965, p. 147). Viewed aborally the brachial platelets alternate in a chevron pattern, with the vertices pointing towards the theca. The brachial platelets form the sides of the arm and imbricate along the distal edges. On the oral side, one cover platelet is matched to every brachial platelet on each side of the ambulacral groove. Stele. The proxistele consists of five to ten telescopically imbricating tetramere rings. A relatively large lumen extends from the inside of the theca to the distal tip of the stele. The distal stele typically consists of three plates at the juncture with the proxistele, thus dilfering from Belemnocystites and Scalenocystites, which usually have four plates. In addition, the distal stele is somewhat flat on the oral side and rounded on the aboral side. In a few individuals (PI. 62, fig. 11) the right (oral face up) distal stele plate at the juncture with the proxistele is expanded into a knob-like structure of unknown function. The mesistele is undifferentiated from the dististele. The distal stele is covered to the tip by numerous small pustules (PI. 63, fig. 5) similar to those on the oral face of the theca. Ontogeny. The ontogeny of I. sagittaria is based on thirty-seven specimens, nineteen of which possess complete and well-preserved thecae. Thecal lengths (measuring from distal tip of M7 to proximal edge of A-M2) range from 7 to 21 mm, with a generally continuous sequence of sizes represented. Immature individuals possess an asymmetric thecal outline characterized by a large, protruding anal lobe. The isosceles-triangle-shaped theca of the adults appears to have developed gradually by accelerated growth of the right proximal thecal angle (oral face up) in comparison with the anal lobe (text-fig. 7). In the smaller specimens the right proximal thecal angle is occupied by marginals M3 and M4. In the larger, presumably more mature individuals, however, the thecal angle is occupied entirely by the M4. The relatively large anal lobe is surrounded by a TEXT-FIG. 7. Superimposed thecal outlines of three specimens of lowacystis sagittaria Thomas and Ladd, 1926, showing progressive changes through ontogeny; anal lobe is on the lower right, x 3. 544 PALAEONTOLOGY, VOLUME 20 number of loosely articulated adanal plates. On the oral face the adanals and oral somatics cover a large vestibule located between the deeply notched sides of marginals Ml and MIO. The ratio of the volume of the vestibule to the main part of the theca is appreciably greater in the immature stages than in the adults. A full complement of aboral thecal plates is clearly developed at the stage of growth represented by the smallest specimens (thecal length 7 mm). As is true for the adults, the aboral somatic plates commonly occur as homologous pairs, particularly the A1 and A2 somatics. The marginals occupy a relatively larger area on the aboral face than the somatics. In the early ontogenetic stages the aboral face is covered by relatively few, widely spaced pustules. Although size of the pustules is relatively constant throughout development, they tend to increase in number, becoming densely packed in the adults. The characteristic nodes, cusps, and arcuate ridges on the marginals are well developed even on the smallest specimens. (Compare immature, PI. 62, fig. 8, with adult, PI. 62, fig. 6.) Plates on the oral side of the theca in the early growth stages tend to be thin, weakly calcified, and, judging from the wide gaps along the sutures, were apparently quite loosely articulated. Furthermore, there is some suggestion that new plates were added by intercalation during growth. The smaller specimens possess from twenty to twenty-five oral somatics, whereas the adults generally have about forty plates. The proxistele and distal stele are differentiated and well developed in the earliest growth stages represented. The axial sutures on both sides of the distal stele are shaped like braces (|) lined end-to-end in an alternating pattern (PI. 62, fig. 10). These arcuate sutures gradually become more linear during growth. The biserial structure of the distal stele is very much evident in the early growth stages; however, new plates were intercalated along the axial suture on the aboral side throughout ontogeny, resulting in a polyplated condition in the adults. Remarks. The aboral thecal plates in lowacystis can readily be homologized with those in ScalenocystUes and Belemnocystites (text-fig. 8), but there are differences in the arrangement of the marginal plates. In lowacystis (A), marginal M7 is typically separated from the aboral somatics by M6 and M8. In addition, the network of ridges and grooves along the marginal edges is more highly developed in lowacystis. EXPLANATION OF PLATE 63 Figs. 1-5. lowacystis sagittaria Thomas and Ladd. 1, SUI 39444 (aboral face), SUI 39445 (oral face), and SUI 39446 (oral face), left, right, and lower respectively; Fort Atkinson Formation (bed no. 9 of Parker et at. 1959), Maquoketa Group, at Fort Atkinson, Iowa, x 1-6. 2, aboral face of SUI 39439; Elgin Member (bed no. 4 of Parker et al. 1959), Scales Formation, Maquoketa Group, Fort Atkinson, Iowa, X 2-5. 3, aboral face of SUI 39438; same locality as fig. 2, x 3. 4, aboral face of SUI 39441 ; Elgin Member (bed no. 4 of Parker e/u/. 1959), near Ossian, Iowa, x2. 5, oral face of SUI 39447 showing pustules on distal stele; same locality as fig. 2, x 3-5. Figs. 6-9. ScalenocystUes strimplei Kolata. Sherwood Member, Dunleith Formation (Cummingsville Member of Weiss 1955, p. 1027), Galena Group, near Cannon Falls, Minnesota, x3. 6-7, aboral face and lateral view of anal lobe of paratype SUI 37048. 8, aboral face of the holotype SUI 37017. 9, oral face of UI X-4895 showing nearly complete arm curved back against theca. PLATE 63 KOLATA et ai, Ordovician carpoids 546 PALAEONTOLOGY, VOLUME 20 lowacystis also possesses more adanal plates. The plates surrounding the base of the arm (adbrachials) on the oral face of the four known genera can confidently be homologized. The remaining oral face plates, however, vary in size, shape, and position so that homologies are not apparent. The structure of the arm and stele in lowacystis is very similar to that of Scalenocystites and Myeinocystites. lowacystis appears to be most closely related to Scalenocystites. Both genera possess a triangular theca characterized by numerous plates on the oral face. The relations are particularly obvious when immature individuals of lowaeystis are compared with adult Scalenocystites. In the early stages of ontogeny, lowacystis posesses an unusually large anal lobe, resulting in a scalene-triangle-shaped thecal outline that is very similar to that of Scalenocystites. If Scalenocystites is a Middle Ordovician ancestor of the Upper Ordovician genus lowacystis, or is close to the M7 \ TEXT-FIG. 8. Homologous aboral plates in the three iowacystid genera, a, lowacystis sagittaria Thomas and Ladd, 1926, SUI 39441. b, Scalenocystites strimplei Kolata, 1973, holotype SUI 37017; suspected modified adanal plate shown at arrow, c, Belemnocystites wetherbyi Miller and Gurley, 1894, holotype FMNH UC 6046; reconstruction of proximal plates based on topotype USNM 14201. Approx. x2-5. lineage that led to lowacystis, as it would appear, then it is quite possible that the similarities between the two genera are due to recapitulatory effects. That is to say, the scalene shape with large anal lobe appears earlier in the descendant’s {lowacystis) ontogeny than in that of the ancestor {Scalenocystites). In addition, compared to the ontogeny of Scalenocystites, the scalene outline in lowacystis appears at a larger thecal size. The unusual cusps, nodes, arcuate ridges, and grooves along the edge of the marginals in lowacystis are noteworthy. Thomas and Ladd (1926, p. 10) carefully described the structures and stated. The elaborate system of grooves and ridges on the marginals and their evident continuity from plate to plate along the periphery of the theca suggest that they may have had a part to play in the economy of the animal other than decoration’. Parsley and Caster (1965, p. 152) gave a detailed description of the structures and proposed a possible function, stating, Tt is possible that this network contained tissue of unusual thickness (i.e., for the external surface of KOLATA, ET AL.: ORDOVICIAN CARPOIDS 547 echinoderm) and may have functioned as a respiratory organ and a sensory system as weir. A similar although much less well-developed pattern of arcuate ridges occurs along the marginals in Scalenocystites. These ridges loop back and forth from one side of the theca to the other in a manner similar to the ridges of lowacystis. Genus scalenocystites Kolata, 1973 Type species. Scalenocystites strimplei Kolata, 1973, p. 970. Diagnosis. Scalene-triangle-shaped thecal outline with large anal lobe; somatic A1 in contact with marginal M7; numerous oral-face plates; base of arm and subthecal mouth typically enclosed by four adbrachial plates; distal stele consists of four plates at juncture with proxistele. Scalenocystites strimplei Kolata, 1973 Plate 63, figs. 6-9; text-figs. 2, 3, 4, 8b, 9 Type specimens. The holotype (SUI 37017) and three paratypes (SUI 37018, 37047, and 37048) are in the repository. Department of Geology, University of Iowa, Iowa City, Iowa. Paratype UI X-4878 and topotype UI X-4895 are reposited in the type collection of the Department of Geology, University of Illinois, Urbana, Illinois. Age. Champlainian Series (Middle Ordovician-Caradocian), Trentonian Stage. Locality. The type specimens are from the argillaceous, buff-coloured calcisiltite of the upper part of the Sherwood Member, Dunleith Formation (Cummingsville Member of Weiss, 1955, p. 1027), Galena Group, at the Wagner Quarry on U.S. Highway 52, 8-8 km south of Cannon Falls, Goodhue County, Minnesota, W. SE. Sec. 8, 1 1 1N.-17W., Sogn Quadrangle. Diagnosis. Same characteristics as genus. Description : Theca. The theca is depressed and generally biconvex in cross-section and is characterized by a large anal lobe. The thecal outline is in the form of a scalene triangle, and the thecal faces are differentiated. The aboral face consists of thick plates that are uniform in size, shape, and position. Ten marginal plates (excluding marginal 0-M2 and the anal plates) form a rigid frame to the theca. On some specimens an additional marginal plate occurs between M 1 and the anal plates (text-fig. 8b) ; it appears to be modified adanal plate. An inner groove (visible on the inside edge of the marginals when the oral face is up) marks the edge of the body cavity and encircles the theca, as in lowacystis. On the aboral face there is a reverse in curvature between the slightly concave marginals and the convex somatic plates. The distal edge of marginal M7 is turned up slightly. Marginals M3 and M4 occupy the right (oral face up) proximal angle of the theca. Marginal M7 is at the distal tip, separating M6 and M8, and is in contact with somatic Al. A marginal flange extends out over the first proxistele tetramere. The marginal plates are marked by a faint arcuate ridge that curves around the thecal edges, looping from one marginal to another in a manner similar to the prominent ridge in lowacystis. The ridge is especially well developed on the larger, presumably more mature, specimens (e.g. UI X-4878 and X-4895). Nodes, cusps, and secondary ridges are present on some of the larger specimens but are not as well developed as those in lowacystis. E 548 PALAEONTOLOGY, VOLUME 20 Typically four aboral somatic plates are present, including the distal Al, central A2 and A3, and a right proximal A4. Somatic Al is heptagonal, and A2 and A3 are hexagonal. The A4 is generally heptagonal or octagonal and is the same size as the other somatics. In one specimen (UI X-4878) the A4 is poorly developed, and its position is occupied by an unusually large MIO and a large marginal plate of question- able homology that is located between the Ml and the adanals (text-fig. 9). The oral face consists of thirty-five to fifty relatively thin plates that apparently were loosely articulated. In most specimens the plates have disarticulated and collapsed on to the inside surface of the more rigid aboral face. In the specimens examined, the pattern of plates on the oral face is generally similar. The larger plates are fairly consistent in shape and position. Minor variations in pattern occur, particularly in or near the anal lobe where plates vary in number. The oral face plates are sutured to the marginals along the marginal lip. The base of the arm and subthecal mouth are typically enclosed by four adbrachial plates. These plates are tilted distally in such a way that the brachial foramen is very close to the distal margin of the theca. The 01 and 02 plates are in positions similar to their places in other iowacystid genera, and the 03 plate is often compound. The adbrachials are tightly sutured to one another, as well as to marginals M6, M7, and M8. The 01 plate is sutured to M7 and M8, and possesses a prominent hydropore adanal TEXT-FIG. 9. Scalenocystites strimplei Kolata, 1973, paratype UI X-4878, showing unusually large MIO and small A4. Approx. x4-5. EXPLANATION OF PLATE 64 Figs. 1-4. Myeinocystites crossmani n. sp. 1-2, aboral faces of paratypes SUI 39452 and SUI 39453, respec- tively; Sherwood Member, Dunleith Formation, Galena Group, near Burr Oak, Iowa. 3, aboral face of holotype UI X-4879; Eagle Point Member, Dunleith Formation, near Rockton, Illinois. 4, oral face of paratype SUI 39451 ; same locality as figs. 1-2. All x 3. Figs. 5-6. Belemnocystites wetherbyi Miller and Gurley. Curdsville Limestone near High Bridge, Kentucky, x2-5. Aboral and oral faces of the holotype FMNH (UC) 6046. Figs. 7-8. Myeinocystites natus Strimple. Bromide Formation, near Ardmore, Oklahoma, x4. Aboral and oral thecal faces, respectively, of USNM (S) 5736. Fig. 9. Scalenocystites strimplei Kolata. Sherwood Member, Dunleith Formation (Cummingsville Member of Weiss 1955, p. 1027), Galena Group, near Cannon Falls, Minnesota, x 3. Lateral view of right thecal edge (aboral face up) of UI X-4878 showing ridges, nodes, and cusps on marginals; hydropore tubercle at arrow. Lig. 10. lowacystis sagittaria Thomas and Ladd. Elgin Member (bed no. 4 of Parker et al. 1959), Scales Lormation, Maquoketa Group, Port Atkinson, Iowa, x 6-5. Interior view of adsteleal plates Ml, A-M2, and M3 (left to right) of SUI 39438 ; grooves along the inner edge of M 1 and M3 are shown by arrows. PLATE 64 KOLATA et al., Ordovician carpoids 550 PALAEONTOLOGY, VOLUME 20 tubercle that is oriented at an oblique angle and projects out along the distal margin of the theca. Four to six pores pass to a small vestibule or depression on the inner surface of the 01 plate. The 01 and 02 plates are sutured to one another at the distal thecal tip beneath the arm. The remainder of the brachial foramen is enclosed by the compound 03 plate. One or two plates occur along the proximal edge of A4 between Ml and the quarter-sphere anal plates. They are probably adanal plates that have become incorporated into the thecal margin. Although small adanals are present in some specimens along the margin between MIO and the quarter-spheres, they are seldom present between A4 and the quarter-spheres, as they are in lowacystis. Both faces of the theca are covered with pustules. Those on the aboral face are relatively large and widely spaced, whereas the pustules on the oral face are smaller and more densely packed. The stereomic microstructure is porous near the plate centres but becomes much more dense at the plate boundaries and in the pustules. Arm. The arm emerges from the oral face at or near the distal margin of the theca. It is slender, nearly half again the length of the theca, and consists of a large biseries of brachial platelets that carry the ambulacral groove and a smaller biseries of erectile cover platelets (text-fig. 2). When viewed aborally, the brachial platelets can be seen to alternate in a chevron pattern with the vertices pointing towards the theca. The brachial platelets form the sides of the arm and imbricate along the distal edges. One cover platelet is matched to every brachial platelet on the adoral side along a slightly depressed line on each side of the ambulacral groove. When closed the cover platelets meet in a zigzag line to form a sharp medial crest along the adoral side. Stele. The proxistele consists of five to seven telescopically imbricated tetramere rings, and the distal stele is composed of thick, elongate, polygonal plates. Through- out its length the stele is round in cross-section. The tetramere rings enclose a large lumen that tapers to the tip of the distal stele. The distal stele typically consists of four plates at the juncture with the proxistele. Within this zone the stele tapers abruptly to a long slender section. The distal stele plates are arranged in a biseries that is obscured somewhat by the presence of intercalary plates that distally increase in number. The entire distal stele is covered to the distal tip by numerous small pustules. Some plates near the distal end are thickened to form short blunt spines that impart a serrate outline to the stele. Ontogeny- Eight specimens were examined that had thecal lengths ranging from 9 to 12 mm. The smaller, presumably immature, specimens possess a relatively large anal lobe and a poorly developed right proximal (oral face up) thecal lobe. Develop- ment appears to have led to a higher degree of bilateral symmetry. The thecal edges in the smaller specimens are sharp, whereas those in the larger are thickened slightly and possess ridges, nodes, and cusps similar to those of lowacystis. Remarks. Scalenocystites appears to be most closely related to lowacystis. Both genera possess a triangular-shaped theca with numerous oral face plates, a marginal hydropore, and ridges, cusps, and nodes on the marginals. Scalenocystites differs, however, in its scalene-triangle-shaped theca, in number and arrangement of thecal KOLATA, ET AL.: ORDOVICIAN CARPOIDS 551 plates, and in its smaller size. The similarity of the plate pattern on the aboral face and the structure of the arm and stele suggest an affinity with Belemnocystites and Myeinocystites. Genus belemnocystites Miller and Gurley, 1894 Type species. Belemnocystites wetherhyi Miller and Gurley, 1894, p. 9. Diagnosis. Oval-shaped thecal outline; thecal edges sharp; marginals supposedly extend equally across both faces; arm and hydropore relatively far removed from thecal edge. Belemnocystites wetherbyi Miller and Gurley, 1894 Plate 64, figs. 5-6; text-figs. 5, 8c, 10 1894 Belemnocystites wetherbyi Miller and Gurley, p. 9, pi. 1, figs. 4-6. 1968 Belemnocystites wetherbyi Miller and Gurley; Parsley in Caster, p. S623, fig. 395. 1972 Belemnocystites wetherbyi Miller and Gurley; Parsley, p. 342, pi. 1, figs. 1-8. Material. The holotype (FMNH UC 6046) is in the Field Museum of Natural Flistory, Chicago, Illinois, and a probable topotype (USNM 14201) is in the U.S. National Museum of Natural History, Washington, D.C. No other specimens are known. Age. Champlainian Series (Middle Ordovician-Caradocian), Trentonian Stage. Locality. The type specimens are from the Curdsville Limestone near High Bridge, Mercer County, Kentucky. Diagnosis. Same characteristics as genus. Description. The holotype (FMNH UC 6046) is a complete, partially silicified theca 19 0 mm long and 15-5 mm wide (PI. 64, figs. 5-6). A small portion of the arm, with some seven or eight segments, is preserved on the oral face. The thecal outline is ovate and the broader end proximal. The theca is depressed and biconvex in cross-section and appears to have suffered little preservational distortion. On the aboral face there is a reverse in curvature between the slightly concave marginals and the convex somatic plates. The thecal edges are sharp and lack ridges, cusps, and nodes. The arm is attached to the oral face towards the distal edge but not at the margin. The plate pattern on the aboral face is like that in the other iowacystids (text- fig. 8c). Marginals M6 and M7 occupy the distal tip of the theca, and the suture between them lies on or close to the plane of symmetry. The right (oral face up) proximal thecal angle is formed by A3. Four aboral somatic plates are enclosed within the marginal series. The distalmost somatic A1 is heptagonal in outline and is generally the largest of the four plates. Somatics A2 and A3, typically pentagonal and hexagonal, respectively, are centrally located and approximately equal in size. The relatively small A4 is in the right proximal thecal angle between A3 and the anal plates. Somatics Al, A2, and A3 are markedly convex. The unusual adsteleal plates described by several authors (Wetherby 1881, p. 177, pi. 5, fig. 2, 2a; Miller and Gurley 1894, p. 9, pi. 1, figs. 4-6; marginals Ml and MT 552 PALAEONTOLOGY, VOLUME 20 of Parsley 1972, p. 342, text-fig. 1c-e) cannot be substantiated in the holotype or in any other specimens now known. Comparison with the topotype supports the reconstruction of the proximal theca shown in text-fig. 8c. The oral face is poorly preserved in the holotype and as a result the exact number and shapes of the plates are questionable. Most authors (Miller and Gurley 1894, p. 8, pi. 1, figs. 4-6; Parsley in Caster 1968, p. S623, fig. 395; Parsley 1972, p. 343, text-fig. 1c-d) describe the marginal plates as extending equally across both thecal faces, and note that five or six oral somatic plates appear in the centre of the oral face. Such an interpretation is based primarily on the apparent alignment of marginal sutures on both thecal faces. The base of the arm and subthecal mouth are enclosed by two or three adbrachial plates. Unlike Scalenocystites and lowa- cystis, however, the adbrachials are not distally angled in a way that brings the arm base dose to the thecal margin. Adbrachial 01 has one, or possibly two, hydropore tubercles close to the arm and well removed from the thecal margin. Adanal plates are limited to one or two small elements along the thecal edge. The original pustulose sur- face ornament is preserved in a few areas on the oral face. The arm rests in a depression that extends between its base and the distal edge of the theca. The exact length of the arm is not known, but it was very likely as long as the theca. The general structure of the arm appears to be very similar to that of other iowacystid species. A large biseries of brachial platelets is covered by a smaller biseries of erectile cover platelets. Neither of the two known thecae have any part of the stele attached. The stele is assumed to be similar to that of other iowacystid species. The topotype is a complete theca, 17 mm long and 13 mm wide. Plate outlines are well preserved on the aboral face but have been obliterated by recrystallization on the oral face. Like the holotype, the topotype is partially silicified. The plating arrangement in the topotype is like that in the holotype except that topotype marginals M9 and MIO are fused. A circular adsteleal foramen is formed in part by Ml, A-M2, and M3; there are strong indications that the same condition existed in the holotype. Remarks. Problems in interpreting the poorly preserved type material have led to differences of opinion between two of the authors of this paper. Kolata believes that plate boundaries, although obscure because of recrystallization, are visible along the edge of the oral face of the holotype and that they support the reconstruction shown in text-fig. 10. These plate boundaries are best seen (under binocular microscope) TEXT-FIG. 10. Belenmocystites wetherbyi Miller and Gurley, 1894. An interpretation of the oral face of the holotype (FMNH UC 6046). x 3. KOLATA, ET AL.: ORDOVICIAN CARPOIDS 553 when light is carefully reflected from the optically oriented crystals within the plates. Sutures corresponding to the reflected boundaries are preserved in some places. According to this interpretation, the pattern of the oral face plates in Belemnocystites wetherhyi is essentially the same as that in Myeinocystites natus. If correct, this would mean that Myeinocystites should be synonymized with Belemnocystites. Strimple disagrees with this interpretation and believes that the poor preservation precludes recognition of discrete plates and that stability of nomenclature requires retention of both genera until more definitive material is found. Genus myeinocystites Strimple, 1953 Type species. Myeinocystites natus Sinmpi\Q, 1953, pp. 105-106; 1961, pp. 184-185. Diagnosis. Oval-shaped theca; thecal edges sharp; thirteen to fifteen plates on oral face ; marginal plates confined to narrow rim on oral thecal face ; base of arm enclosed by three adbrachial plates; arm and hydropore relatively far removed from thecal edge. Myeinocystites natus Strimple, 1953 Plate 64, figs. 7-8 1953 Myeinocystites natus 105-106, figs. 1-2. 1 96 1 Myeinocystites natus Strimple ; Strimple, pp. 1 84- 1 85. 1972 Myeinocystites natus Strimple; Parsley, p. 344, pi. 1, figs. 9-14. non 1975 Myeinocystites natus Strimple; Kolata, p. 15, pi. 1, figs. 8-10. Material examined. The holotype is USNM (S) 4657 and a topotype is USNM (S) 5736 (PI. 64, figs. 7-8). Age. Champlainian Series (Middle Ordovician-Caradocian). Localities. The type specimens are from the Bromide Formation in a bank of Spring Creek, Criner Hills, 1T2 km south-west of Ardmore, Oklahoma. Single specimen (FMNH PE 15647) is known from the Benbolt Formation, 2-4 km west of Washburn, Tennessee, on Highway 131, but it was not available during our investigation. The specimens assigned to M. natus by Kolata (1975, p. 15) from the Dunleith Formation of northern Illinois are herein reassigned to M. crossmani n. sp. Diagnosis. A species of Myeinocystites characterized by a relatively small aboral, somatic A4 that is not in contact with the proxistele. Description. The holotype (USNM S 4657) is a complete theca 16-5 mm long and 14-0 mm wide. Part of the arm and seven or eight proxistele tetrameres are intact. The thecal outline is ovate with the broader end proximal. The theca is depressed and was probably distorted during fossilization. As in B. wetherhyi, the aboral face is slightly concave along the sutures between the marginals and somatics. The thecal edges are tapered and lack ridges, cusps, and nodes. Marginal and somatic plates on the aboral face can confidently be homologized with the other iowacystids. Except for the relatively small somatic A4, the aboral plates are similar to those of B. wetherhyi in size, shape, and arrangement. The marginal plates are bent abruptly at the thecal edges and are confined to a narrow rim on the oral face. The oral face consists of thirteen to fifteen relatively thin plates that are disarticulated and fractured in some places. The plates have collapsed on to the inside surface of 554 PALAEONTOLOGY, VOLUME 20 the more rigid aboral plates. The oral face plates are sutured to the marginal plates along the marginal lip, as they are in Scalenocystites and lowacystis. The base of the arm is surrounded by three adbrachial plates homologous to those in Scalenocystites and lowaeystis. Adbrachial 01 possesses a prominent, cone-shaped hydropore tubercle. The 01 and 02 plates are sutured to each other between the base of the arm and the distal edge of the theca. The remainder of the brachial foramen is enclosed by the 03 plate. The quarter-sphere anal plates lie along the proximal margin in the same relative position as those of the other iowacystids. Two or three small adanal plates appear on the oral face. Both thecal faces and the proxistele are covered with pustulose ornament. Pustules on the aboral face are relatively large and widely spaced, whereas those on the oral face are smaller and more densely packed. The pustulose ornament is also quite pronounced in the topotype (PI. 64, figs. 7-8). A small part of the arm that has about ten segments is attached to the distal oral face. The arm is like arms of other iowacystids in that it consists of two matching but unequal biseries of plates. It rests in a slight depression between adbrachials 01 and 02. About seven or eight telescopically imbricated proxistele tetrameres are intact. No part of the distal stele is preserved. The topotype is a complete theca, 10-0 mm long and 8-5 mm wide, with part of the arm and proxistele intact. Plate patterns on the aboral and oral faces are like those in the holotype. The topotype differs in that on its aboral face the marginals occupy a relatively larger area than the somatics. Similar variation has been observed in the immature stages of lowaeystis. It is probably due to ontogenetic variation. Parsley (1972, p. 344) assigned a specimen (FMNH PE 15647) to M. natus from the Benbolt Formation of Tennessee. The plating arrangement on the oral face of this specimen is quite similar to that of the topotype discussed above. Myeinoeystites erossmani n. sp. Plate 64. figs. 1-4; text-fig. 11 1975 Myeinoeystites natus Strimple; Kolata, p. 15, pi. 1, figs. 8-10. Material. The holotype (UI X-4879) is in the type collection of the Department of Geology at the University of Illinois, Urbana, Illinois. One paratype (BMNH PK-70) is deposited in the Burpee Museum of Natural History, Rockford, Illinois. Three paratypes, SUI 39450, 39451, and 39452 are in the repository of the Department of Geology at the University of Iowa, Iowa City, Iowa. Derivation of name. Specific appellation is for Glenn C. Crossman, who discovered some of the type material. Age. Champlainian Series (Middle Ordovician-Caradocian), Trentonian Stage. Locality. The holotype and one paratype (BMNH PK-70) are from the basal cherty dolomite of the Eagle Point Member, Dunleith Formation, Galena Group, in the Porter Brothers quarry 1 -2 km south of Rockton, Winnebago County, Illinois, NW. SE. NE. Sec. 35, 46N.-1E., South Beloit 7-5-minute Quadrangle. The remaining paratypes are from the cherty, partly calcarenitic limestone at the top of the Sherwood Member, Dunleith Formation, Galena Group, in a quarry located approximately 0-7 km north-west of Burr Oak, Winneshiek County, Iowa, SW. SE. Sec. 14, 100N.-9W., Decorah 15-minute Quadrangle. KOLATA, ET AL.\ ORDOVICIAN CARPOIDS 555 Diagnosis. A species of Myeinocystites characterized by a relatively large aboral somatic A4 that is in contact with the proxistele. Description. Thecal outline is a relatively elongate, asymmetric oval. Right proximal thecal lobe (oral face up) not well developed; left margin nearly continuous with stele. The theca is depressed and biconvex in cross-section. The aboral face consists of regular marginal and somatic plates that are homologous to other iowacystids. The marginal plates occupy a relatively large area on the aboral face, but they are confined to a narrow peri- pheral band on the oral face. Adsteleal M 1 is very small and in most specimens is usually concealed between somatic A4 and the proxi- stele (text-fig. 1 1). Somatic A4 is in a marginal position and appears to have functioned as an adsteleal plate in conjunction with Ml. The oral thecal face is not well preserved in the specimens studied here. From all indica- tions it consists of thin plates arranged in a pattern similar to that of M. natus. The base of the arm and the subthecal mouth are sur- rounded by three adbrachials (Ol, 02, and 03). The hydropore consists of four or five small pores. The arm rests in a shallow depres- sion along the 01-02 suture. The two quarter-sphere plates of the anus are located along the margin of the right proximal lobe between the Ml and MIO. No additional adanal plates were observed. Both thecal faces are covered with pustules. Pustules on the aboral face are rela- tively large and widely spaced, whereas those on the oral face are small and densely spaced. Pustules also occur on the distal stele. Arm. The arm is slender, and its length was probably equivalent to that of the theca (PI. 64, fig. 4). It consists of a large biseries of brachial platelets covered on the oral side by a smaller biseries of erectile cover platelets that meet on the median along a zigzag line. Stele. Only the proxistele and a small part of the distal stele are preserved in the specimens examined here. The proxistele consists of six to ten telescopically imbricated tetramere rings with plane of symmetry sutures forming an irregular zigzag line. The extensiplane sutures are closely appressed and lack the zigzag pattern. The distal stele consists of four plates at the Juncture with the proxistele and has sutures in the plane of symmetry and extensiplane. In cross-section four or five polygonal plates surround a large, round lumen that extends distally. Remarks. The holotype of M. crossmani n. sp. was previously assigned by Kolata (1975, p. 15) to M. natus Strimple. It is now apparent, however, that M. crossmani differs from M. natus in possessing a relatively large A4 somatic plate that is in contact with the proxistele. A-M2 TEXT-FIG. 1 1. Myeinocystites crossmani n. sp., proximal view of theca showing the adsteleal plates. x4-5. 556 PALAEONTOLOGY, VOLUME 20 Acknowledgements. We are grateful to Ronald L. Parsley of Tulane University and Daniel B. Blake of the University of Illinois for critically reading the manuscript and making valuable suggestions for improve- ment. We also wish to thank Matthew H. Nitecki of the Field Museum of Natural History, Chicago, Milton Mahlburg of the Burpee Museum of Natural History, Rockford, Illinois, and Frederick J. Collier of the U.S. National Museum of Natural History, Washington, D.C., for lending study material. We are also indebted to the Illinois State Geological Survey and the Department of Geology, University of Illinois, Urbana, for the use of their facilities during the study. REFERENCES BASSLER, R. s. 1938. Eossilium Catalogus I : Animalia. Pars. 83; Pelmatozoa Palaezoica. Gravenhage, 1-194. BATHER, F. A. 1913. Caradocian cystidea from Girvan. Trans. R. Soc. Edinb. 49, Pt. 2, No. 6, 359-426, 500-508, pis. 1-4. 1926. Review; thomas, a. o. and ladd, h. s. Additional cystoids and crinoids from the Maquoketa Shale of Iowa. Geol. ZentBl. 34, No. 5, 233-234. 1928. Dendrocystis in North America. Bull. natn. Mus. Can. 49 (Geol. Ser. 48, Contr. Can. Paleont.), 5-8. BROADHEAD, T. w. and STRIMPLE, H. L. 1975. Respiration in a vagrant Ordovician cystoid, Amecystis. Paleobiology, 1, 312-319. CASTER, K. E. 1968. In MOORE, R. c. (ed.). Treatise on Invertebrate Paleontology. Pt. S. Echinodermata 1 (2), Homalozoans, Homoiostelea. Geol. Soc. America, Univ. of Kansas Press, S581-S627. CHAUVEL, J. 1941 . Recherches sur les cystoides et les carpoides americains. Mem. Soc. geol. miner. Bretagne, 5, 1-286, pis. 1-7. DEHM, R. 1933. Cystoideen aus dem rheinischen Unterdevon. Neues Jb. Miner. 69, Abt. B, 65, 72. 1934. Untersuchungen an Cystoideen des rheinischen Unterdevons. Abt. Bayer. Akad. Wiss. mat.-nat. Sber. Miinchen, H. 1, 19-43. GILL, E. D. and CASTER, K. E. 1960. Carpoid echinoderms from the Silurian and Devonian of Australia. Bull. Am. Paleont. 41, No. 185, 7-43, pis. 1-7. KOLATA, D. R. 1973. Sccilenocystites strimplei, a new Middle Ordovician belemnocystitid solute from Minnesota. J. Paleont. 47, 969-975, 1 pi. 1975. Middle Ordovician echinoderms from northern Illinois and southern Wisconsin. Paleont. Soc. Mem. 7, J. Paleont. 49, 1-74, pis. 1-15. MILLER, s. A. and GURLEY, w. F. E. 1894. New Genera and species of Echinodermata. Bull. III. St. Mus. nat. Hist. 5, 5-53, pis. 1-5. NICHOLS, D. 1972. The water-vascular system in living and fossil echinoderms. Palaeontology, 15, 519-538. PARKER, M. c., DORHEiM, F. H. and CAMPBELL, R. B. 1959. Resolving discrepancies between surface and sub- surface studies of the Maquoketa Formation of northeast Iowa. Proc. Iowa Acad. Sci. 66, 248-256. PARSLEY, R. L. 1972. The Belemnocystitidae ; Solutan homeomorphs of the Anomalocystitidae. J. Paleont. 46, 341-347, 1 pi. and CASTER, k. e. 1965. North American Soluta (Carpoidea, Echinodermata). Bull. Am. Paleont. 49, 109-174, pis. 16-18. PAUL, c. R. c. 1967. The functional morphology and mode of life of the cystoid Pleurocystites E. Billings, 1854. Echinoderm Biology. Symp. zool. Soc. Land. 20, 105-123. REGNELL, G. 1943. Non-crinoid Pelmatozoa from the Paleozoic of Sweden. MeddnLwtds geol.-miner. Instn, 108, 1-255, pis. 1-15. STRIMPLE, H. L. 1953. A new carpoid from Oklahoma. J. Wash. Acad. Sci. 43, 105-106. 1961. On Myeinocystites Strimple. Okla. Geol. Notes, 21, 184-185. TEMPLETON, J. s. and wiLLMAN, H. B. 1963. Champlainian Series (Middle Ordovician) in Illinois. Bull. III. St. geol. Surv. 89, 1-260. THOMAS, A. o. and LADD, H. s. 1926. Additional cystoids and crinoids from the Maquoketa Shale of Iowa. Stud. nat. Hist. Iowa Univ. 11, 5-18, pis. 1-6. UBAGHS, G. 1968. In MOORE, R. c. (ed.). Treatise on Invertebrate Paleontology. Pt. S. Echinodermata 1 (2), Homalozoans, Stylophora. Geol. Soc. America, Univ. of Kansas Press, S495-S565. KOLATA, ET AL.\ ORDOVICIAN CARPOIDS 557 WEISS, M. p. 1 955. Some Ordovician brachiopods from Minnesota and their stratigraphic relations. J. Paleont. 29, 759-774. WETHERBY, A. G. 1881. Descriptions of new fossils from the Lower Silurian and sub-carboniferous rocks of Kentucky. J. Cincinn. Soc. nat. Hist. 4, 177-179. DENNIS R. KOLATA Illinois State Geological Survey Natural Resources Building Urbana, Illinois 61801 HARRELL L. STRIMPLE Department of Geology University of Iowa Iowa City, Iowa 52242 Typescript received 2 April 1976 Revised typescript received 14 June 1976 CALVIN O. LEVORSON Box 13 Riceville, Iowa 50466 “1; ‘wxUa'V-iMij ■ ■ ‘■'■wSLi' A SYSTEM OF GROUP NAMES FOR SOME TERTIARY POLLEN by M. C. BOULTER Clfld G. C. WILKINSON Abstract. Analysis of the literature has shown that the use of form taxa to describe tricolpate and tricolporate pollen grains from the European Tertiary has little stratigraphic or botanical value. An alternative methodology for investigating Tertiary pollen involves two stages in the process of observation and description. One of these, the first phase, is dealt with in this paper, and involves assigning pollen to a group by means of a simply defined grid; this enables easy identification of all possible types. The second phase demands the use of sophisticated techniques for observation and comparison so as to establish details of botanical affinity and biostratigraphic correlation. The first-phase procedure is demonstrated by reference to pollen assemblages from three deposits in the western part of the British Isles. The rapid increase in the number of publications on pre-Pleistocene palynology over the past twenty-five years has produced an excessive number of described taxa, and this has created many taxonomic problems (Kremp and Methvin 1968). This funda- mental difficulty is clearly evident in a study of a number of European Tertiary pollen and spore assemblages (text-fig. 2) in which large numbers of tricolpate and tri- colporate pollen are encountered. These types of pollen are commonly present in many European Tertiary assemblages and have been regularly described over the past 40 years. Nevertheless, their identification is still very difficult and their strati- graphic and botanical usefulness is increasingly regarded as being negligible. This paper is an attempt to review that information from the literature which might have continuing importance to aspects of stratigraphy and evolution, and to illustrate the use of such knowledge in describing assemblages from three Tertiary deposits. The new method of analysis which is used involves the designation of a small number of groups of pollen which are very simply defined and which we propose as alternatives to binomial nomenclature. Since these groups are defined by two characters (polar length and surface sculpture) which are usually available in the records of established taxa, we have been able to analyse the literature to show that the groups have as much stratigraphic value as the original binomial taxa. This work only applies to fossil pollen which has been compressed perpendicular to the polar axis— equatorially flattened forms of tricolpate and tricolporate pollen have only rarely been described in the European Tertiary and usually occur in small quantities. In the past, palynologists have used very different levels of detail to establish definitions of new form genera and species, and techniques of preparation, sampling, and illustration have also varied considerably in quality and detail. One consequence of this variation is that, for an over-all comparison from the literature, the number of characters that can be used is limited by the minimum detail available in any one major published work. We propose that, for the purposes of the first phase in the analysis, which involves the initial identification and comparison of pollen from different Tertiary assemblages, very simple uncontroversial characters should be used. This can be achieved by the use of a simple method of group identification within [Palaeontology, Vol. 20, Part 3, 1977, pp. 559-579.] 560 PALAEONTOLOGY, VOLUME 20 a grid (Tables 1 and 2, rather than by the use of form taxa. This method of identifica- tion involves only ten primary first-phase groups, which replace about 115 form species of tricolporate pollen that have been described in the literature. Although in this paper we are advocating a rather simple systematic treatment of these pollen types (our ‘first phase’) it is clear that on a long-term basis a more searching and elaborate systematic treatment may yield more refined stratigraphic and botanical data (our ‘second phase’). This second phase of operation demands a very detailed level of study, with the use of the electron microscope for examination and com- parison with other fossil material and with modern equivalents, as well as the use of other advanced techniques such as computer analysis (Germeraad and Muller 1970). When it is necessary to create new form species or biorecords (Hughes and Moody- Stuart 1969) as much information as possible must be provided so as to define the taxa precisely. SOME PROBLEMS OF NOMENCLATURE IN TERTIARY PALYNOLOGY Though the concept of the form taxon is useful for Tertiary macrofossils, the experi- ence of the last 40 years of palynology has shown that it has a far more limited value if applied to Tertiary pollen and spores. There are two major reasons for this. During the Tertiary, angiosperm evolution was progressing rapidly, so that large numbers of species must have existed during that time. There are more than 250000 species of angiosperms in existence today (Sporne 1974), and many more must have existed over the 63 million years of the Tertiary period. Such a diversity over such a length of time is found in few other groups. Given the diversity, it would not have been surpris- ing if those attempting to classify various types of Tertiary pollen had found this a difficult task, even if these pollen types had exhibited a large number of charae- teristics on which their classification could be based. However, many eommonly occurring types of Tertiary pollen, particularly tricolpate and tricolporate ones, show comparatively few characters ; that these show little variation makes the problem more difficult. Indeed, much of the confusion about fossil tricolpate and tricolporate pollen types is due to the well-known controversies about pollen morphology (Kremp 1965) in which authors interpret the same morphographic terms in different ways. In addition, problems of morphological interpretation of light microscope studies abound, though many of these can now be resolved by the use of the electron microscope. Some of these difficulties were recognized by Erdtman (1947, 1948) who proposed the formation of an informal system of identification based on ‘sporomorphs’ — names which describe the major morphological types of pollen without the con- straints of the International Code of Botanical Nomenclature. Though adopted by Cookson (1947), this system has been criticized for the confusion that it creates through similarity with the formal methods (Schopf 1949) and for its disregard of any association with modern botanical affinity (Traverse 1955). Most European palyno- logists have therefore continued to use the formal binomial (though without paying much attention to the nature of the type specimens), perhaps mainly because it is easy to use the form generic names created by Thomson and Pflug (1953) as these are defined in broad and simple terms. Claims of their affinity to genera or families that BOULTER AND WILKINSON: GROUP NAMES FOR TERTIARY POLLEN 561 are defined with extant plants must still be treated with extreme caution. Brown (1957), in a review of European Tertiary pollen studies, urges the creation of a system of ‘classification’ based on the pollen morphology, in order to facilitate the rapid determination of individual grains within a particular assemblage. Others have chosen to make their identifications outside the rules of the Code by using informal group names which lack any precise definition and are usually based on a set of poor photographs with little or no verbal description (Krutzsch 1958; Sontag 1966; Kedves 1967). Since the time of Traverse’s (1955) review of methods of nomenclature in Tertiary palynology, the trend has been to use one of three methods to describe the components of pollen and spore assemblages: form taxa, modern taxa, or form groups. The use of form taxa Since the rejection of Robert Potonie’s form genus PoUeuites (Potonie 1958) the subsequent confusion has brought about several variations on this formal system of naming and division. Most contemporary European Tertiary palynologists follow Thomson and Pflug’s (1953) use of form genera such as TricolporopoUeni1esT\\om?,on and Pflug (tricolporate pollen), Tricolpopolleuites Thomson and Pflug (all tricolpate pollen) and Suhtriporopollenites Thomson and Pflug (all pollen with three simple pores, all or in part subequatorial). These form genera are defined very clearly and simply, and the chief criticism of their use has been their lack of emphasis on possible relationships to extant plant taxa (Traverse 1955). This has not prevented many European palynologists since 1953 from using these names, though a few (e.g. Krutzsch 1961, 1970) have split some of the largest categories. The principle is the same in all cases: a form genus is defined simply on major morphological charac- teristics, and a form species is usually based on specimens from one assemblage, the amount of detailed description varying according to the judgement of the author. This method of citation of form genera and form species suffers from four difficulties. (1) There is often little or no stratigraphic restriction on the range of the major form taxa within the European Tertiary. Indeed, most have very long ranges and some extend even to the Palaeozoic. Pew, if any. Tertiary palynomorphs have a well- understood age range. (2) There are problems connected with different authors’ value-judgements on the amount of detail necessary for diagnosis, as well as with variations in the interpretation of characters and in preparation and preservation. Hughes and Moody-Stuart (1967) have discussed some of these difficulties when proposing that more than 100 specimens be available prior to the erection of a new form species or biorecord. (3) When a new assemblage is studied it is common to find that some specimens cannot readily be interpreted as belonging to form species already known from other assemblages. This difficulty can be overcome in one of two ways. Pirst, these specimens can be referred to a new form species, though only rarely do other workers refer their specimens to these taxa. Secondly, they may be tentatively referred to an existing form taxon by the use of devices such as cf. B or cf. C for form species (Hughes and Moody-Stuart 1967) or Genus sp. A for form genera (Manum 1962; Machin 1971). (4) The small amount of comparison with modern forms that is recorded within the literature provides few opportunities for reliable assignment to categories of living plants. Very little is known of the detailed 562 PALAEONTOLOGY, VOLUME 20 morphology from extant species of angiosperms, though a few species are well understood. Palynological studies can contribute to the solution of two types of problem- stratigraphic and phyletic. Because of the difficulties described above, the inter- pretation of common types of European Tertiary pollen in terms of form taxa has thrown little light on either of these problems, with the exception of the few forms that are easy to identify because of some morphological peculiarity. This is con- firmed by our own analysis and use of Thomson and Pflug’s (1953) form species (see below). The use of modern taxa In the European literature, a few authors have used modern generic names to describe angiosperm pollen from Eocene, Oligocene, or Miocene deposits. Macko (1957), Simpson (1961), and Machin (1971) are the most prominent examples, but both the limited modern pollen reference collections available to them, and the lack of advanced facilities for observation, make it impossible for them to have made substantial detailed comparisons. Many macrofossils occurring within European Tertiary deposits have been identified as belonging to modern genera, but few palynologists other than Machin have been willing to use this knowledge to support a similar identification of the pollen from the same deposit. Using such indications, pollen identification is occasionally possible to the generic level, but not to the specific level. Indeed, many evolutionary botanists (Stebbins 1950; Takhtajan 1969) argue that few modern angiosperm species existed more than 10 million years ago, and few modern genera more than 35 million years ago. Because patterns of plant dispersal in North America were so different from those in Europe, the practice of American workers such as Traverse (1955) and Leopold and Macginitie (1972) in commonly citing modern genera to identify Oligocene pollen is more acceptable there (Wolfe and Hopkins 1967). However, the assignments are rarely confirmed by detailed comparisons with their modern equivalents as well as with fossil material from Europe. The use of form groups Krutzsch (1958, 1970), Sontag (1966), and Kedves (1967) have created more than 200 morphological categories that they call form groups, and which may be used in stratigraphic correlation; most of them are shown to have clearly restricted age ranges. There are two major weaknesses in this method of description. First, none of the authors has produced anything more than a photograph to define each group, and their scientific value is therefore very limited. Other workers cannot assign their specimens to these form groups solely from comparison with these published pictures. Secondly, the range charts are based on material that is limited both geographically and stratigraphically. As with the use of form taxa, the more these stratigraphic limits are tested, the more they are extended. For instance, Krutzsch’s more recent publication (1970) provides a stratigraphic revision to some of the form groups which extends their age range. BOULTER AND WILKINSON: GROUP NAMES FOR TERTIARY POLLEN 563 PROPOSAL FOR A TWO-PHASE APPROACH The future development of Tertiary palynology is likely to be impeded by the existence of these three conflicting systems of naming. If they persist, the literature will become increasingly swamped with unmanageable numbers of new taxa defined at different levels of detail, whilst ever more extended stratigraphic ranges will still further reduce their usefulness. Our first-phase procedure concerns problems associated with preliminary investigation, particularly when different assemblages are being com- pared. It is here that the existing literature is useful, largely in establishing the limits of the range of morphological variation in the major types of pollen. Our concept of group identification uses existing knowledge of this to set up grids based on the com- bination of two variables, both of which have wide ranges of variation. Consequently, any pollen within these ranges will fall into one group within the grid. Although the method is applied here only to the identification of tricolporate and tricolpate pollen grains that are compressed in the polar axial plane, other grids can be devised to designate other types of pollen (e.g. tricolpate and tricolporate pollen flattened in the equatorial plane — a very small amount of this kind of pollen is found in the European Tertiary; triporate pollen, etc.). These different grids can vary in the characters used for definition of the co-ordinates as well as in the extent of any size limits that might be involved. Differently defined grids can be devised for different assemblages, according to the kinds of pollen within each major type that occurs. For instance, the tricolpate pollen that occurs at one locality may be suitably described with psilate, scabrate, and baculate sculpturing characters as one co-ordinate, and polar length ranging from 0 to 25 /xm and from 15 to 40 ;am as the other. Tricolpate pollen from another locality may have the same types of sculpturing but different size limits of polar length, 0-20 f^im and 20-40 ftm. Our second-phase procedure would consist of a very precise level of examination using as many advanced techniques as possible. So far, work to this level of detail has not been attempted in Europe, and little can therefore be said of its potential. Hughes (1970) has discussed the way in which such precise work can help with correlations within the Cretaceous. Also, some of the work of Krutzsch (1961) has achieved a high level of detailed description from light-microscope observations, together with interpretations giving correlation with other pollen-bearing deposits in East Germany. But there is no doubt that other structural detail can be obtained more accurately from the electron microscope, and that this can then be used for correlation within the whole of the European province. The first-phase groups have been devised from a knowledge of the extent of varia- tion within tricolpate and tricolporate pollen of the European Tertiary. Their designa- tion here arose from our confrontation with the very large numbers of pollen from these types which occur in assemblages throughout the European Tertiary. The majority of dicotyledon pollen is of the tricolpate or tricolporate type, and our quantitative analysis of palynomorphs from many European Tertiary assemblages shows that often as much as 80% of the pollen present is of these types. Placing such pollen in existing form taxa is difficult and provides little useful information. Thomson and Pflug (1953) identified eleven form species of tricolpate pollen and thirty-nine tricolporate species from the German Tertiary, and these names are those most F 564 PALAEONTOLOGY, VOLUME 20 commonly used in subsequent studies (see Appendix 1). Our review of work reported in sixteen papers (A-P in Appendix 1) on European Tertiary palynology published since then shows two important tendencies. First, those taxa that have been recorded more than once since 1953 have had their stratigraphic range extended to cover most of the Tertiary. Secondly, those taxa with a restricted range have rarely been referred to by other authors; we believe that this is due to the limitations of the original descriptions of these taxa and does not imply that their geographic and stratigraphic ranges are signihcantly restricted. Since 1953, some workers have proposed new form species of both tricolpate and tricolporate pollen, though few of these have ever been recognized in the published work of others. Our conclusion from this review, there- fore, is that no single existing taxon of tricolpate or tricolporate Tertiary pollen contributes to the solution of stratigraphic problems. It is also widely accepted that the determination of the botanical affinities of these types of pollen cannot be made (Krutzsch 1970). It was against this background that we began to search for a simpler way of designating the tricolpate and tricolporate pollen from the European Tertiary. There is little value in making dubious identihcations if the resulting names have little signihcance, and a simple method of avoiding such ambiguity is therefore preferable. The only characteristics that are regularly used within the literature to identify these pollen are polar length and sculpturing type and, under certain clearly dehned limits, both these features can easily be recognized. Polar length may vary with particular preservation and preparation effects, but not signihcantly. The polar length is not changed signihcantly by preservation except when the pollen grain has been battened equatorially. This type of compression is rare for prolate and otherwise elongate forms of tricolpate and tricolporate pollen. In the European Tertiary it is generally conhned to Tricolporopollenites kruschi accessorius {Polonie 1934) Thomson and Phug 1953, T. kruschi amilepticus (Potonie 1934) Thomson and Phug 1953, T. iliacus (Potonie 1931) Thomson and Phug 1953, and small scabrate tricolpate pollen grains. If such palynomorphs are encountered in signihcant quantity, it may be necessary to dehne a grid system to accommodate them. Thomson and Phug (1953) erected the Turma Brevaxones to accommodate equatorially battened pollen grains, but did not include the genera TricolpopoUenites or Tricolporopollenites, which are strictly referable to the Turma Eongaxones. In the case of polar length, the limits of dehnition of the hrst-phase groups are described on the basis of practical convenience for the types studied, so as to provide the least difficulty in allocating individual specimens to the groups (Tables 1 and 2). Different assemblages of tricolpate and tricolporate pollen may therefore require different limits of dehnition. In the case of the second characteristic commonly available, the type of surface sculpturing, the dehnitions of the different types used follow those of Faegri and Iversen (1964) and are explained in text-hg. 1. If necessary, other columns can be added to accommodate pollen with different types of sculpture (e.g. granulate). Specimens with two types of surface sculpture, such as when that at the poles differs from that at the equator, can be allocated to two combined groups, e.g. 3C: SCA 1-PSI 1. This system, using a combination of polar length and exine sculpture, is designed to accommodate tricolpate and tricolporate pollen types battened along the polar BOULTER AND WILKINSON: GROUP NAMES FOR TERTIARY POLLEN 565 TABLE 1. Grid for first-phase groups of tricolpate in the European Tertiary. The four types of surface sculpture are defined in text-fig. 1 . Existing form taxa can be allocated to these groups as listed in the text. echinate bacuiate scabrate psilate 0 30 50 80 polar length _ microns ECH 1 BAG 1 BAG 2 SCA1 SGA 2 SGA 3 PSl 1 PSl 2 TABLE 2. Grid for first-phase groups of tricolporate pollen in the European Tertiary. The five types of surface sculpture are defined in text-fig. 1. Existing form taxa can be allocated to these groups as listed in the text. reticulate RET 1 RET 2 RET 3 clavate GLA 1 bacuiate BAG 1 BAG 2 scabrate SGA 1 SGA 2 psilate PSl 1 PSl 2 0 35 55 80 polar length _ microns axis. First stage grids based on other characters will be needed to accommodate other types of pollen that may be particularly abundant and difficult to assign to con- ventional form taxa. For instance, pollen belonging to Triatriopollenites, Triporo- pollenites, Trivestibulopollenites, Subtriporopollenites, Intratriporopollenites, and Porocolpopollenites have been assigned to sixty-five form species by Thomson and Pflug (1953). Trial and error has shown that the most suitable characters for grid definition of these pollen are the type of aperture and the grain diameter. 566 PALAEONTOLOGY, VOLUME 20 Grids constructed on the basis of the two characters polar length and exine sculp- ture have provided eight groups (Table 1) into whieh the existing tricolpate pollen form genera can be allocated, as follows: 3C: PSI 1 Tricolpopollenites liblarensis liblarensis Thomson and Pflug 1953 T. liblarensis fallax Thomson and Pflug 1953 3C: PSI 2 Pollenites parmularius Potonie 1934 3C: SCA 1 Tricolpopollenites microhenrici intragranulatus Thomson and Pflug 1953 T. microhenrici intrahaculatus Thomson and Pflug 1953 T. densus Thomson and Pflug 1953 3C : SCA 2 T. asper Thomson and Pflug 1953 T. henrici Thomson and Pflug 1953 T. microstriatus Cavagnetto 1970 T. cavernoides Cavagnetto 1970 3C; SCA 3 Pollenites confinis pudicus Potonie 1934 Tricolpopollenites pudicus Thomson and Pflug 1953 3C: BAC 1 T. retiformis Thomson and Pflug 1953 3C: BAC 2 T. pseudoeuphorii Thomson and Pflug 1953 3C: ECH 1 Pollenites spinosus Potonie 1931 Similarly, the two characters provide ten groups (Table 2) into whieh the existing tricolporate pollen form taxa can be allocated, as follows: 3CP : PSI 1 Pollenites facelus, P. ansatus, P. megae.xactus, P. exactus inimis, P. doliiformis, P. oviforinis, P. lembus, P. fusiis, P. cingulum fusiis, and P. cingulum ovalis, Potonie 1931. P. exactus, P. quisqualis, P. quisqualis pusillus, and P. cingulum briihlensis, Potonie 1934. Tricolporo- pollenites cingulum fusus, T. cingulum pusillus, T. cingulum oviformis, T. megaexactus briihlensis, and T. megaexactus exactus, Thomson and Pflug 1953. T. laevigatus and T. mansfieldensis, Krutzsch 1969. 3CP: PSI 2 Pollenites manifestus and P. inornatus, Potonie 1931. P. manifestus multiexituum, Potonie 1934. Tricolporopollenites escbweilerensis, Thomson and Pflug 1953. 3CP: SCA 1 Pollenites caseolus, P. pompeckji, P. pseudocingulum, P. pseudocingulum granulatum, P. thomsi, P. megagertrudae, P. fraudulentus, P. interruptus, P. ventosus, P. inornatus, P. pulvinus, P. navicula, P. dolium solum, P. dolium megaventiosum, P. dolium clarion, P. rauffi, P. laesus, P. pseudolaesus, and P. pseudocruciatus, Potonie 1931. P. selectus, P. pseudocingulum navicula, P. pseudocingulum rauffi, P. abbreviatus, P. gertrudae propius, P. pseudocruciatus pantherinus, P. orthoaesus, P. kruschi analepticus, P. kruschi scutellatus, P. kruschi dispar, and P. kruschi accessorius, Potonie 1934. P. laesus microlaesus, Potonie and Venitz 1934. Tricolporopollenites kruschi contortus, T. pseudocingulum, T. steinensis, T. pacatus, and T. satzveyensis, Thomson and Pflug 1953. T. eislebensis, Krutzsch 1961. T. singularis, T. Stanley!, and T. globosus, Cavagnetto 1970. 3CP: SCA 2 Pollenites megadolium digitatus, P. megadolium sinuatus, and P. orthoaesus lasius, Potonie 1934. Tricolporopollenites porasper, T. kruschi rodderensis, T. donatus, T. pseudocruciatus, and T. lasius, Thomson and Pflug 1953. 3CP: BAC 1 Pollenites euphorii and P. caroli, Potonie 1931. Tricolporopollenites microporitus and T. villensis, Thomson and Pflug 1953. Pollenites cingulum villensis Potonie, Thomson, and Thiergart 1950. Tricolporopollenites baculatus Krutzsch 1961. T. pseudoaceroides Cavagnetto 1970. 3CP; BAC 2 Pollenites edmundi and P. edmundi tenuis, Potonie 1931. Tricolporopollenites baculoferus, T. marcodurensis, T. waUensenensis, T. hehnstedtensis, and T. borkenensis, Thomson and Pflug 1953. BOULTER AND WILKINSON: GROUP NAMES FOR TERTIARY POLLEN 567 MM AAM 0 0 OO^Oo o°o ooo° °^o0 0o° odD^O o^o%o%o clavate echinate baculate TEXT-FIG. 1. Definitions, after Faegri and Iversen (1964), of the terms used here to describe the surface sculpture of the pollen grains from some of the hrst phase-groups. For each type of sculpture there is a drawing of (top) the equatorial view of the pollen grain, (middle) the sectional view, and (bottom) the surface view. PSILATE: surface even, or with pits no greater than 1 /um in diameter. Drawing of pollen from equatorial view is from group grid 3CP: PSI 1, X 2000. SCABRATE: no dimension of surface sculpturing greater than 1 ,um in diameter. Drawing of pollen from equatorial view is from group grid 3CP: SC A 2, x 1000. RETICUEATE: elements greater than 1 ,am and forming a reticulum. Draw- ing of pollen from equatorial view is from group grid 3CP : RET 1 , x 2000. CLAVATE; upper end of sculpturing element thicker than the base, though the element is greater than 1 fim. Drawing of pollen from equatorial view is from group grid 3CP: CLA I, x 1000. ECHINATE: sculpturing elements greater than 1 / On ^ - U ^ a: u • - '5 0-) a c/5 e 8 -o (U O O o "o Q ON C3 O X) •= "S > o 3 •3 3 pa' Is o § § ^ o sw- — Oh > O ^ z cd . ^ Oh no • ' 'n oo c NO C3 ON cn ^ a. - s CO 3 to ^ — 00 ^ o\ “ - - - 10 11 10 O'-'-'O — ^ 1, APPENDIX I The sources from which the original ranges of Thomson and Pflug's (1953) form species of tricolpate and tricolporale pollen have been revised. For each form species, details are given of : the phase-one group to which it is allocated ; the original range as cited in Thomson and PRug ( 1953) e.xpressed in terms of the stratigraphic scale of Harland et al. (1967) (see Table 3); the occurrences recorded in sixteen articles (A-P, see below) published since 1953 (( \ ) denotes that details of the sub-form-specics arc not recorded in the literature); and the stratigraphic range as revised by these references. A. Padtova 1963; B. Boulter 1971; C, Mazancova 1962; D. Zicmbinska-Tworzydlo 1974; E. Neuy-Stoltz 1958; F. Mamezar I960; G. von der Brelie 1968; H. Padtova I960; I. Doktorowicz-Hrebnicka 1957/»; J. Doktorowicz-Hrebnicka 1957o; K, Padtova 1966; L, Chateauneuf 1972; M, Pfianz! 1956; N. Grabowska 1965; O, Kedves 1969; P, Cavagnetto 1970. lihlarensis lihlorensis liblarensis fallax parnmlarius reliformis pseudocupliorii spinosus Tricolporopolleniles rillensis pacaius cmgulum fusus cingulum puvilus cingulum orifnrmis megaexacliix hnVilensis mcgocxacius exaciiis cuphorii horkenensis IwIntsieJiensii wallenseneiisis iC: SCA 3 SCA 2 SCA 2 SCA 1 SCA I PSI I PSI I PSI 2 BAC 1 BAC 2 ECH 1 3CP: SCA 1 BAC 1 SCA I SCA I PSI I PSI I SCA 1 RET 2 BAC 2 BAC 1 BAC 2 PSI 2 BAC 2 BAC 2 BAC 2 SCA I 1953 10-11 5-8 3-11 5-8 5-10 8-10 8-10 8-10 5-11 8-10 5-8 5-10 5-11 5-10 5-11 8-10 3 5-8 B C D E F G H 5-10 5- 1 1 8-10 3-11 kruschi anulepiiais krvschi foJ4lerfnsis kruschi cnniorliis porasper marganiaiui donaiui SCA 1 5-11 SCA 1 5-10 SCA 2 5-8 SCA I 5-11 SCA 2 5-8 RET 3 5-11 SCA 2 8-10 BAC 2 8-11 SCA 2 8-11 RET I 5-10 BAC I 8-10 CLA 1 5-10 CLA 1 5-10 CLA 1 8-10 CLA I 5-10 CLA I 3-10 CLA 1 3-10 CLA I 5-10 SCA 2 10-11 (-f) ( t ) ( 1 ) ( U (-H ( •-) (r) (t) <-) (*) t+) t’) (F) (+) 5-8 5-11 4-9 4-11 8-11 8-1 1 0 0 578 PALAEONTOLOGY, VOLUME 20 APPENDIX 2 Assemblage lists for the three samples to which the first-phase method has been applied. The tricolpate and tricolporate pollen is identified in terms of first-phase groups, whilst other palynomorphs are referred to by form taxa diagnosed by Thomson and Pflug (1953), unless otherwise stated. The three samples are deposited with the Institute of Geological Sciences. That from the Bovey Forma- tion, Devonshire (IGS SAL 6269, clay sample; IGS SAL 6270, pollen preparation) is a surface sample from the Southacre Member exposed at Southacre pit (SX 855755) ; that from Ballymacadam, Co. Tipperary, Ireland (IGS SAL 6271, clay sample; IGS SAL 6272, pollen preparation) is a surface sample from the old clay pit (4 km SE. Cahir); that from Saint Agnes, Cornwall (IGS GSM 10401, clay sample; IGS SAL 6273, pollen preparation) is thought to have been collected in 1932 by H. Dewey from the Beacon Cottage farm claypits (SW 705502). Bovey Ballymacadam Saint Agnes Laevigatosporites haardti -1 j- 1- L. discordatus + Leiotriletes sp. Krutzsch T Stereisporites sp. f Cicatricosisporites spp. L -1- -f- Gleicheniidites senoniciis Skarby f Reticulatisporites coelatus -( Triplanosporites sp. + Pityosporites labdacus -1- + -1- P. microalatus + -b -r Inaperturopollenites hiatus + + Graminidites media Cookson + + Bohlensipollis hohli Krutzsch + + f DicoIpopoUis kockeli Pflanzl + + Triatriopollefiites coryphaeus punctatus + + + T. coryphaeus microcoryphaeus + + + T. myricoides + T. plicatus + Triporopollenites robustus + T. coryloides + + f T. labraferus T Trivestibulopollenites betuloides + Intratriporopollenites indubitabilis + f I. instructus + f Porocolpopollenites vestibulum + + T Polyvestibulopollenites verus + -T PolyporopoUenites stellatus + MultiporopoUeniles maculosus + Periporopollenites stigmosus + MonocolpopoUenites zievelensis + M. tranquillis + + 3C; PSI 1 + + PSI 2 + SCA 1 f + + SCA 2 + + + BAC 1 f + + ECH 1 + BOULTER AND WILKINSON: GROUP NAMES FOR TERTIARY POLLEN 579 Bovey Ballymacadam 3CP: PSI 1 - , SCA 1 4 I- BAC 2 I RET 1 4 j CLA 1 : Tetracolporopollenites obscwus — ‘ Compositoipollenites rizophorus Potonie f TetradopoHenites calUdus ■ i T. ericius \ Saint Agnes "T H- G \ I? •.> ■ ! p ■ ■ njUfiiiSi A NEW RICCIISPORITES FROM THE TRIASSIC OF ARCTIC CANADA by CHARLES j. FELIX and Patricia p. burbridge Abstract. A new plant spore, Ricciisporites umbonatus sp. nov., is described. Its occurrence in surface and subsurface is reported. The species appears to occur in Norian and Karnian age rocks. Palynologic AL Study of Triassic sediments in the Canadian Arctic Islands has resulted in the designation of a new taxon, Ricciisporites umbonatus, which is best assignable to the genus Ricciisporites Lundblad (1954), 1959. The spore appears to be stratigraphically limited, but it has been observed on numerous occasions from both the surface and subsurface, and is frequently numerous in its representation. We have also recorded it from both marine and non-marine associations. Triassic rocks are widely distributed in the islands of Arctic Canada, but it has only been in the past two decades that salient features of Triassic stratigraphy have been established. In the Sverdrup Basin, exposures of Triassic rocks occur on Ellesmere, Axel Heiberg, Cornwall, Melville, Prince Patrick, Brock, and Borden Islands, as well as on many smaller islands. The extensive Triassic sediments in the Sverdrup Basin have proved to be of interest as reservoirs for hydrocarbons and have increased in commercial potential. The sediments consist of interbedded marine shales and siltstones and non-marine sandstones, and several distinct facies occur. Detailed correlation of the various sandstones is dithcult, and palynological tech- niques are one of the most promising tools for correlation. Relatively little attention has been devoted to Triassic palynology in the Arctic Islands, and the studies of McGregor (1965), Felix (1975), Fisher and Bujak (1975), and Bujak and Fisher (1976) are the most significant palynology contributions. The assignment of the new spore to Ricciisporites is admittedly speculative. In part identification is based upon a morphological similarity to R. tuberculatus Fundblad (1954), 1959, with which it is invariably associated, often in large numbers. In general, the diagnosis is general and brief. The spores have a distal sulcus, and the exine surface has a variety of processes. The major difference from the generic diagnosis is that of tetrad occurrence, since Fundblad (1959) noted that the spores were permanently united into tetrads, and R. tuberculatus, the genotype, seems to always occur in a tetrad configuration. R. umbonatus usually occurs in single grains, but tetrads were observed. About 10% of the recorded occurrences were tetrads. The presence of both single grains and tetrads in the same family, or even genus, is not unique in fossil or extant plants. The failure to have consistent tetrads in R. umbonatus should not deter its assignment to Ricciisporites. The arborescent lycopods have one of the best-known fossil records of the com- mon occurrence of single grains and tetrads. Andrews and Pannel (1942) noted a [Palaeontology, Vol. 20, Part 3, 1977, pp. 581-587, pi. 65.] 582 PALAEONTOLOGY, VOLUME 20 characteristic retention of the tetrad of Lycospora in microsporangiate cones of Lepidocarpon magnificum. Felix (1954) reeorded a frequency of Lycospora tetrads in Lepidostrohus diversus, but the single-grain feature did seem most common. Felix (1954) and Balbach (1967) found varying degrees of tetrad occurrences in L. oldhamius Williamson, 1893 and Brack (1970) reported essentially the same dual spore pattern in L. schopfi. Lycospora in tetrads and single grains are therefore common components of Pennsylvanian spore floras. Such dual occurrences are extremely common among extant floras. Typha of the Typhaceae and Ludwigia of the Onagraceae have species whieh shed pollen in tetrads and others which shed single grains. The Ericaceae are often considered as characteristically having pollen tetrads, but single-grain dispersal occurs in several species in the family. Similarly, species with both single grains and tetrads are found in the Saxifragaceae and Pyrolaeeae. Routine laboratory pro- cedures were used in maceration, with all samples initially treated with hydrochloric acid followed by hydrofluoric acid to digest minerals. In most instances a mild oxida- tion of humic material was undertaken with Schulze’s solution. Separation was done by a zinc chloride flotation, and Clearcol was utilized as a permanent mountant. LOCALITY DATA Materials for this study came from surface exposures and from well cuttings in the Canadian Arctic Islands, with R. umhonatus being present in all samples considered. The associated microflora is given in Table 1. 1. Sun Oil Co. Section no. 77. Surface collections. Oyster River South. Borden Island. Sun Oil Co. Maceration nos. 8571-8575. Schei Point Formation. Karnian. 2. Sun Oil Co. Section no. 78. Surface collections. Oyster River North. Borden Island. Sun Oil Co. Maceration nos. 8597-8603. Schei Point Formation. Karnian. 3. Sun Oil Co. Section no. 81. Surface collections. Intrepid Inlet, Jameson Bay. Prince Patrick Island. Sun Oil Co. Maceration nos. 8917-8920. Heiberg Formation. Norian. 4. Panarctic Gulf et al. East Drake 1-55 Well. Melville Island. Well cuttings. Sun Oil Co. Maceration nos. 12395 (3750-3780 ft), 12396 (3780-3810 ft), 12397 (3810-3840 ft). Schei Point Formation. Karnian. 5. Panarctic Homestead Hecla J-60 Well. Melville Island. Well cuttings. Sun Oil Co. Maceration nos. 12412 (3680 ft). 12414 (3760 ft), 12415 (3810 ft). Heiberg Formation. Norian. 6. Panarctic Drake Point L-67 Well. Melville Island. Well cuttings. Sun Oil Co. Maceration no. 12540 (3990 ft). Geological Survey Canada Slide C-12263 (4100 ft). Heiberg Formation. Norian. SYSTEMATIC DESCRIPTION Anteturma sporites H. Potonie, 1893 Turma plicates (Naumova, 1939) R. Potonie, 1960 Subturma monocolpates Iversen and Troels-Smith, 1950 Genus ricciisporites (Lundblad, 1954) emend. Lundblad, 1959 Type species. Ricciisporites tuherculatus (L\xnAh\?id, 1954) emend. Lundblad, 1959. Ricciisporites umbonatus sp. nov. Plate 65, figs. 1-19 Diagnosis. Spores oval to elongate. Sulcus irregular, not clearly defined and often represented by elongate, thin exinal area. Body minutely granulose, wall distinct, FELIX AND BURBRIDGE; TRIASSIC SPORE FROM ARCTIC CANADA 583 1-5 ;u.m-3-5 ;am thick. Sculptural elements vary, usually of prominent rounded processes from 4 fxm to 13 fxm in diameter, but with variations in shape and size to large verrucae 10 /xmx24 ^m. Infrequently in tetrads. Dimensions. (Sixty-five specimens.) Over-all equatorial diameter 40 /xm x 45 /^m-68 x 70 f^m. Diameter of spore body 26 ;timx33 ^m~A\ ^um x 56 ^um. Rare specimens observed with over-all dimensions of 30 /L<.m x 35 ;um and 65 /^m x 95 /um but are regarded as aberrants. Tetrad size 75 nvn x 80 ^im-85 ftm x 90 /um. Holotype. Slide 8920-1. Location 44-9 x 112. Plate 65, fig. 1. The holotype has been deposited in the col- lection of the United States National Museum of Natural History, under catalogue no. 240061 from USNM Catalogue no. 36. The type specimen has been ringed with a diamond-point engraving objective to further facilitate location. Table 1. Associated Microflora. Surface Subsurface Localities 1 2 3 4 5 6 Ricciisporites tuberculatus X X X X X X Zebrasporites interscriptus X X X Ovalipollis ovalis X X X X Ova lipol lis bre viforn i is X X Limbosporites hmdbladii X X Protodiploxypinus sp. X X X X X X Brachysaccus sp. X X X X X X Sverdrupiella usitata X X X Sverdrupiella baccata X X Sverdrupiella ornaticingulata X X Sverdrupiella septentriomdis Sverdrupiella manicata X X Description. Holotype 67 jum x 69 fxm over all. Body diameter 50-5 /xm. Wall distinct, 3-5 pm thick. Surface-bearing globular proeesses with diameters 9-12 pm. Processes seattered, about fifteen around body periphery. Spore body minutely granulose, with ill-defined, irregular sulcus. Remarks. The surface ornament is usually of prominent globose excrescences of fairly uniform size and shape. Some variations exist such as small diameters (PI. 65, fig. 12), and occasional clavate or pilate shapes. There are rare examples (PI. 65, figs. 15, 18, 19) which would appear too diverse in ornamentation for inclusion in R. umbonatus, but specimens exist which show transitional characters to these forms. The exinal protuberances may vary with specimens having both rounded ornamenta- tion and verrucae development (PI. 65, fig. 15). Greatly enlarged, irregularly shaped ornament features are present such as Plate 65, fig. 19, where only five protuberances developed. A trend also exists to near verrueate, flanged morphology (PI. 65, fig. 18). These departures from the typical morphology are scaree and could represent aberrants. They are so rare and so variable that further taxonomic division seems inappropriate. Much the same variability exists in the well-known R. tuberculatus but is little noted in the literature. Geiger and Hopping (1968) noted considerable variability within R. tuberculatus, with at least four variants present. Schulz (1967) observed wide size and sculpture variations in R. tuberculatus but considered division 584 PALAEONTOLOGY, VOLUME 20 into more species inappropriate. The sulcus is not easily observed, usually being obscured by the processes, and still ill defined on denuded specimens (PL 65, fig. 8). Often it appears as a thinning in the exine and of irregular shape, but it is a consistent feature on most specimens. Ornamentation composed of tubercules or rounded verrucae somewhat similar to those of R. umhonatus are known for other miospores, but there does not appear to be any close comparison with other described taxa. There is some resemblance in ornament to Lophozonotriletes lebedianensis, described from the Famennian of the Russian Platform by Naumova (1953), and Devonian entities are commonly recycled into Arctic Mesozoic sediments. However, the Devonian representatives are easily differentiated, and the preservation and association characteristics of R. umbonatus indicate its indigenousness to the Triassic. L. lebedianensis is also clearly trilete, whereas R. umbonatus is consistently sulcate and never displays a trilete character. STRATIGRAPHICAL OCCURRENCE The exact stratigraphical placement of R. umbonatus is somewhat conjectural, as is often the case in a comparatively new area of investigation and when dealing with such large areal extent as the Canadian Arctic. We have observed the spore in common association with several taxa characteristic of the Upper Triassic (Table 1). When collecting the surface sections considered here, we regarded the field samples in which R. umbonatus is present as being representative of the Schei Point Formation and of Karnian age. However, as our subsurface studies progressed, the association of R. umbonatus in wells has been with marine microplankton successions, which Fisher and Bujak (1975) have regarded as entirely or certainly mostly of Norian age. EXPLANATION OF PLATE 65 Figs. 1-19. Ricciisporites umbonatus sp. nov. All figures x 500. 1, holotype; slide 8920-1, location (44-9 X 112); 2. specimen with large, densely concentrated tubercules, occurring commonly; slide 8920-1, location (21-7 x 1 19-9); 3, small, partially denuded specimen with granulose body and sulcus area visible; slide 8920-2, location (35-5 x 113-5); 4, small specimen with sparse tubercules and minimum over-all diameter for species, sulcus visible, occurring sparsely; slide 8920-2, location (13x122-2); 5, partially denuded large specimen with granulose body and sulcus area visible; slide 8920-1, location (40 X 1 16-4); 6, large specimen with densely concentrated tubercules and maximum over-all diameter for species; slide 8920-2, location (41-1x118); 7, small specimen with uniform tubercule distribution; slide 8920-2, location (38x112-9); 8, isolated, granulose body, sulcus visible; slide 8920-1, location (39-9x116); 9, partially denuded specimen with granulose body and sulcus area visible, occurring commonly; slide 8920-2, location (34-5x 120-5); 10, partially denuded specimen with sulcus visible; slide 8920-2, location (27-8 x 116-5); 11, large, distorted specimen, occurring rarely; slide 8920-1, location (24-8 X 123-8); 12, partially denuded specimen, occurring rarely, with very small diameter tubercules; slide 8920-2, location (48-5 x 114); 13, commonly occurring sub-surface form; slide 12395-1, location (41 X 122); 14, commonly occurring form; slide 8920-1, location (21-6 x 1 19); 15, rare, probable aberrant, with sulcus visible, tubercules irregular; slide 8920-2, location (39-5 x 108); 16, tetrad, with large, densely concentrated tubercules; slide 8920-2, location (36-5 x 115-1); 17, tetrad, with normal tubercule con- figuration; slide 8920-2, location (40x 109-1); 18, rare, probable aberrant, irregular tubercules forming verrucae and incomplete flange; slide 8920-2, location (37-5 x 1 15); 19, rare, probable aberrant, massive irregular tubercules, sulcus area visible; slide 8920-1, location (31-8x 120-2). PLATE 65 FELIX and BURBRIDGE, Ricciisporiies from the Trias 586 PALAEONTOLOGY, VOLUME 20 A comparison of the surface and subsurface successions is difficult since the surface materials containing R. umbonatus are non-marine, whereas the subsurface samples occurred in marine beds. Therefore precise control is difficult to establish with such varied environmental conditions. Our surface collections have some associations with fossil faunas and lithological sequences that offer some stratigraphical clarification. A prominent feature of the Schei Point Formation is the presence of an Upper Karnian ‘Gryphaea Bed’ (Douglas 1970, p. 578). This consists of a thick calcareous sandstone with coquinoid layers of Gryphaea and Plicatula. This bed marks the top of the Schei Point Formation in central Ellesmere Island and is also present on Prince Patrick and Borden Islands. A prominent coquina bed, assumed to be the same one, is present in all three of our surface sections. In Sections 77 and 78 R. umbonatus has its occurrence within the limits of the coquina bed. In Section 81 R. umbonatus occurs immediately above the coquina bed. The conclusion, therefore, is that R. umbonatus is Upper Schei Point (Karnian) in Sections 77 and 78 from Borden Island. It has a Lower Heiberg (Norian) occurrence in Section 81 from Prince Patrick Island. The reasoning for Fisher and Bujak (1975) considering their subsurface dinoflagellate assemblage to be Norian seems valid. Accordingly, the common association of R. umbonatus with these dino- flagellates in wells would indicate the spore’s subsurface presence to be Norian. Present evidence does not indicate that R. umbonatus occurs in Rhaetian age sedi- ments, but that it is presently found in Lower Heiberg Formation (Norian) and Upper Schei Point Formation (Karnian) sediments. The fact that there is still no corroboration of marine and non-marine sediments and considering the actual limited range of Arctic studies, additional range extension of R. umbonatus is not precluded. Further studies may well warrant changes in these premises. ASSOCIATED MICROFLORA All of the assemblages contained numerous bisaccate pollen, and most seemed assignable to Protodiploxipinus (Samoilovich) Scheuring, 1970 and Brachysaccus Madler, 1964. The Protodiploxypinus '\nc\\xdcs MmutosaccusM.dLd\tr , 1964, and species represented include P. gracilis, P. potoniei, and P. schizeatus. The bisaccate grains occur in such numbers and variety as to be beyond the scope of this study. However, they appear to be an integral part of the populations, and they did not occur in association with Rhaetian assemblages in the localities treated here. Table 1 lists the more prominent taxa occurring in association with R. umbonatus. Preservation was good, and R. tuberculatus in both surface and subsurface and Sverdrupiella Bujak and Fisher, 1976 in the subsurface were generally well represented. Such generally diagnostic Upper Triassic representatives as Cornutisporites seebergensis Schulz, 1967, Triancoraesporites communis Schulz, 1967, RhaetipoUis germanicus S)c\wx\z, 1967, RhaetogonyauJax rhaetica 1963), Davey, Downie, Sarjeant, and Williams 1966, and Semiretisporis Reinhardt, 1962, which we have observed frequently in Arctic studies, are not present in these samples. They have been common in other areas of Upper Triassic interest, and their association has always appeared to be Rhaetian age. Ricciisporites tuberculatus was a common entity, and it was usually numerous in all localities. The bisaccates, encompassing a variety FELIX AND BURBRIDGE: TRIASSIC SPORE FROM ARCTIC CANADA 587 of Brachysaccus and Protodiploxypiims were also prominent in all six localities. Zebrasporites interscriptus (Thiergart) Klaus, 1960 was noted only from the surface localities. Sverdnipiella was usually numerous in the subsurface samples, with S. usitata Bujak and Fisher, 1976 being the most common representative. Despite diligent surveillance, Sverdnipiella was never observed in surface sections, and the occurrences of Sverdnipiella treated by Fisher and Bujak (1975) and Bujak and Fisher (1976) from the Arctic Triassic are all from subsurface deposits. The exact field position of specimens is noted in the plate explanation as co-ordinates in parentheses. The reference point co-ordinate of 5 x 120 is marked on each slide to assist in locating specimens. ANDREWS, H. N. and PANNED, E. 1942. Contributions to our knowledge of American Carboniferous floras. II. Lepidocarpon. Ann. Mo. Bot. Card. 29, 19-34, pis. 5-8. BALBACH, M. K. 1967. Paleozoic lycopsid fructifications. III. Conspecificity of British and North American Lepidostrohiis petrifications. Ainer. J. Bot. 54, 867-875, 7 figs. BRACK, s. D. 1970. On a new structurally preserved arborescent lycopod fructification from the lower Pennsylvanian of North America. Ibid, 57, 317-330, 36 figs. BUJAK, j. p. and FISHER, M. J. 1976. Dinoflagellate cysts from the Upper Triassic of Arctic Canada. Micro- paleontology, 22, 44-70, pis. 1-9. DOUGLAS, R. J. w. (ed.) 1970. Geology and economic minerals of Canada. GeoL Surv. Can. Econ. Geol. Rpt. 1. 838 pp. FELIX, c. J. 1954. Some American arborescent lycopod fructifications. Ann. Mo. Bot. Gard. 41, 351-394, pis. 13-19. 1975. Palynological evidence for Triassic sediments on Ellef Ringnes Island, Arctic Canada. Rev. Palaeobot. Palynol. 20, 109-117, pis. 1-2. FISHER, M. J. and BUJAK, J. 1975. Upper Triassic palynofloras from arctic Canada. Geosci. and Man. 11, 87-94, pis. 1-2. GEIGER, M. E. and HOPPING, c. A. 1968. Triassic stratigraphy of the southern North Sea basin. Phil. Trans. R. Soc. Land. 254, 1-36, pis. I -4. LUNDBLAD, B. 1959. On RiccUsporites tubercidatiis and its occurrence in certain strata of the ‘Hollviken IT boring in S.W. Scania. Grana Palynol. 2, 77-86, pi. 1, MCGREGOR, D. c. 1965. Illustrations of Canadian fossils: Triassic, Jurassic, and lower Cretaceous spores and pollen of Arctic Canada. Geol. Surv. Can. Paper 64-55, 32 pp., pis. 1-10. MADLER, K. 1964. Die geologische verbreitung von sporen und pollen in der Deutschen Trias. Beihefte geol. 65, 1-147, pis. 1-12. NAUMOVA, s. N. 1953. Spore-pollen complexes of the Upper Devonian of the Russian platform and their stratigraphic significance. Trudy Inst. Geol. Nauk, Akad Nauk SSSR, 143, 1-202, pis. 1-22. SCHEURING, B. w. 1970. Palynologische und palynostratigraphische Untersuchungen des Keupers im Bolchentunnel (Solothurner Jura). Schweiz, Paldontol. 88, 1-119, pis. 1-43. SCHULZ, E. 1967. Sporenpalaontologische Untersuchungen ratoliassischer Schichten im Zentralteil des Germanischen Beckens. Paldont. Abh. B, 2, 541-633, pis. 1-26. LOCATION OF SPECIMENS REFERENCES C. J. FELIX, P. P. BURBRIDGE Original typescript received 29 March 1976 Revised typescript received 6 September 1976 Sun Oil Company Richardson Texas 75080 U.S.A. 1 IM tv * ” I ' \i t \ n f/f t¥= iqi ASSOCIATED DENTITION OE THE CHIMAEROID FISH BRACHYMYLUS ALTIDENS FROM THE OXFORD CLAY by D. J. WARD and K. J. mcnamara Abstract. The discovery of a well-preserved associated chimaeroid dentition in the Oxford Clay near Peterborough, England has permitted a revised description of the Jurassic chimaeroid Brachymylus altidens 'W oodward. It is assigned with Pachymylus and CaUorhinchus to the family Callorhinchidae. The holotype of B. minor Woodward and lectotype of B. ahidens Woodward are figured for the first time. A COMPLETE set of associated dental plates of the chimaeroid fish Brachymyliis ahidens Woodward was found in 1972 in a disused Peterborough Oxford Clay Pit by one of the authors (K. J. M.). The part of the pit where the specimens were found consists of dumped mounds of non-bituminous clay which are thought to be from the athleta Zone of the Callovian stage which overlies the quarried bituminous lower zones. Weathering of the mounds results in fossil remains being exposed on the surface. One half of the left vomerine plate was visible, whereas the other half, along with the other five plates, was located below the surface close by. No dorsal fin spine was recovered. Associated with the plates was a large amount of fragmented lignite. No other macrofossils were found in the immediate vicinity, except for a specimen of Gryphaea associated with the right palatine plate. Chimaeroids are cartilaginous fishes known in the Mesozoic and Tertiary eras, principally from their detached dental plates and fin spines, although skeletal remains have been found in the Kimmeridgian (Late Jurassic) and Chalk (Late Cretaceous). The first true chimaeroids, members of the suborder Chimaeroidei (Patterson 1965), appear in the Bathonian with the two closely related genera Ischyodus and Ganodus. In the Callovian and Oxfordian, Ischyodus is joined by Pachymylus leedsi Woodward and B. ahidens Woodward. All these genera possess primitive, principally crushing, dentitions. B. minor Woodward and Elasmodectes secans Woodward, the earliest species with dentitions adapted for shearing as well as crushing, appear in the Kimmeridgian. Ischyodus and Edaphodon, genera with crushing dentitions, remained pre-eminent throughout the Cretaceous, then became extinct in the Tertiary. The Palaeogene saw the proliferation of a suite of more specialized forms, including Chimaera and Amylodon, heralding the modern fauna with small shearing dentitions. Chimaeroid dentitions consist of three pairs of plates^mandibular, vomerine, and palatine. The palatine pair are larger than, and are positioned posterior to, the vomerine plates. In the absence of skeletal material, the taxonomy of fossil chimaeroids is based on the characteristics of the dental plates, particularly the number, size, and distribution of their raised biting surfaces known as tritors. The terminology is summarized in Ward (1973) based on Newton (1878), and Woodward (1891). [Palaeontology, Vol. 20, Part 3, 1977, pp. 589-594, pi. 66.] 590 PALAEONTOLOGY, VOLUME 20 Registration numbers prefixed by ‘P’ are those of the Department of Palaeontology, British Museum (Natural History), that prefixed by ‘S.M.’ is in the Sedgwick Museum, Cambridge. SYSTEMATIC PALAEONTOLOGY Class HOLOCEPHALI Order chimaerida Suborder chimaeroidei Family callorhinchidae Genus brachymylus Woodward, 1892 Type species. Brachymylus altidens Woodward, 1892, p. 15; from the Oxford Clay, Peterborough. Revised diagnosis. Mandibular plate rhomboidal and laterally compressed. Oral surface with three tritoral areas all arising from a single body of tritoral dentine which forms the greater part of the plate. Post-oral margin parallel to the symphysial margin; oral margin excavated between the posterior-outer and symphysial tritors. Median tritor occupying the hinder half of the oral surface, not impinging on the oral margin. Inner surface excavated to expose the compact base of the tritoral dentine. Brachymylus altidens Woodward, 1892 Plate 66, figs. 1-6; text-fig. 1a v*1892 Brachymylus altidens A, p. 15. Holotype. Incomplete corroded left mandibular plate P.6891, A. Leeds Collection. Material. Holotype and P.57041u-/, an associated dentition of two mandibular, vomerine, and palatine plates. Occurrence. Holotype; only recorded as ‘Oxford Clay, Peterborough’; thus Callovian or Oxfordian. P.57041 : lathleta Zone, Callovian, near Peterborough, England (TL. 167937). Description. The mandibular plate (PI. 66, figs. 1, 2) is rhomboidal, and laterally compressed, with a concave-oral and post-oral margin and prominent beak. The oral surface, which occupies half the outer surface, bears three tritoral areas. The large symphysial tritor runs the entire oral length of the symphysial margin and is medially truncated by an oblique wear facet. The ovoid median tritor is centrally placed and EXPLANATION OF PLATE 66 Brachymylus altidens Woodward x 1. Fig. 1 ; P.5704 lb. Right mandibular plate; outer (oral) surface. Fig. 2; P. 57041b. Right mandibular plate; inner surface. Fig. 3; P. 57041c. Right palatine plate; inner surface. Fig. 4; P.57041C. Right palatine plate; outer (oral) surface. Fig. 5; P.57041L Right vomerine plate; inner (lateral) surface. Fig. 6; P.57041 f. Right vomerine plate; outer (medial) surface. PLATE 66 WARD and McNAMARA, Chimaeroid fish 592 PALAEONTOLOGY, VOLUME 20 occupies the posterior two-thirds of the length of the oral surface. The outer tritor is narrow and forms the lateral margin of the oral surface, but does not impinge anteriorly on the oral margin. The post-oral surface is covered with enameloid, which extends just over the symphysial and post-oral margins. The inner surface exposes the depressed-toughened base of the tritor, a series of fine lamellae running parallel to the post-oral margin, bounded antero-laterally by a band of enameloid- coated dentine covering the beak and running along the oral margin. The vomerine plate (PI. 66, figs. 5, 6) is quadrate, with a wide symphysial surface extending posteriorly to form a beak, and a prolonged maxillary articulation surface. The large oval tritor is placed medially in the oral surface. The inner and outer surfaces are covered with enameloid, except for the tip of the beak and the upper half of the inner surface, which have the same lamellar development as seen on the mandibular plate. The palatine plate (PI. 66, figs. 3, 4) is rounded anteriorly and has a laterally prominent post-oral wing. There are two oval tritoral areas, the inner tritor being slightly anterior to the larger median tritor. The post-oral surface is covered with enameloid, and the inner surface has the lamellar structure as on the mandibular plate, bounded antero-laterally by a band of enameloid-covered dentine. In both the palatine and mandibular plates the tritors arise from an unexposed mass of tritoral (pleromic) dentine which forms a substantial part of the plate. All six plates are in an excellent state of preservation and are complete, with the exception of the left palatine plate, which is lacking a fragment of post-oral wing. The tritors are all corroded, a feature common to chimaeroids from aerobic sedi- ments. The palatine and right mandibular plates are slightly crushed, a fragment of TEXT-FIG. 1. A, Bracbymylus altidens y^oodward, holotype P.6891. Left mandibular plate, oral surface. Magnification approximately xl -3. B, 5. Woodward, lectotype P. 4166a. Left mandibular plate, oral surface. Magnification approximately x 2-7. Abbreviations; O.S., outer surface; M.T., median tritor; O.T., outer tritor; S.F., symphysial tritor; P.-O.S., post-oral surface. WARD AND McNAMARA: CHIMAEROID FISH BRACHYMYLUS 593 Gryphaea shell being embedded in the laminar tritor of the right palatine. The vomerines are virtually undistorted but have a number of dorso-ventral fissures. The holotype, unfigured by Woodward (1892), is a small left mandibular plate (text-fig. 1a). The oral surface is worn, almost removing the median tritor and causing the outer tritor to impinge on the oral margin. The symphysial (wear) facet has obliterated all but a trace of the symphysial tritor. This degree of wear would suggest the individual died in senility. The inner surface is smooth, but not rolled, with no enameloid remaining and only traces of the laminae. The dentine is corroded and bears a large number of shallow multidirectional scratches. This is necessarily a post-mortem feature and suggests the plate was chewed and partially digested in the stomach of a marine predator or scavenger prior to fossilization. The tip of the beak is lacking but the break has sharp edges, suggesting that it occurred quite recently. TABLE 1. A comparison of the mandibular dental plates of Pachymylus leedsi, Brachymylus minor and B. altidens. Brachymylus minor Plate short Small symphysial tritor Posteriorly positioned median tritor Outer tritor large and convex Small symphysial facet Large symphysial facet Symphysial margin shorter than Symphysial margin longer than posterior outer margin posterior outer margin DISCUSSION Woodward’s diagnosis of Brachymylus is understandably brief, since he had only the single worn B. altidens specimens and three diminutive examples of B. minor. The differences between B. altidens and B. minor are greater than could have been previously anticipated. Table 1 compares some aspects of their mandibular plates with those of Pachymylus leedsi Woodward, a species with which the dentition of B. altidens bears some functional similarities. Woodward also omitted to figure B. minor, nor did he specify a holotype. P.4166a is here designated the lectotype (text-fig. 1b). It is difficult, when considering the dentition alone, to distinguish between features of varietal, specific, or generic significance. This problem is discussed in Newton (1878, p. 3) and acknowledged in Woodward (1912, p. 182) in relation to the recent Chimaera colliei Bennett. In spite of the differences between B. altidens and B. minor, their over-all similarities are considered sufficient to allow their inclusion in the same genus. The presence of a single body of pleromic dentine, forming tritors on the oral surface and exhibiting laminar ornamentation on the inner surface, is a feature common to both Brachymylus and Pachymylus. In all other fossil genera, multiple Brachymylus altidens Plate long Large symphysial tritor Posteriorly positioned median tritor Outer tritor small and concave Pachymylus leedsi Plate long No symphysial tritor Anteriorly positioned median tritor Outer tritor three small punctate areas Large symphysial facet Symphysial margin longer than posterior outer margin 594 PALAEONTOLOGY, VOLUME 20 tritors are formed by longitudinally aligned tubes of pleromic dentine. Only in Callorhmchus is there a single body of pleromic dentine, which being fully exposed on the oral surface forms a single tritor. The base of the plate in both Recent and fossil species of Callorhinchus bears laminar ornament as in the Jurassic species. Patterson (1965), following Woodward (1891), conventionally assigns Brachymyhis and Pachymylus to the Chimaeridae, along with Elasmodus, Edapliodou, Ischyodus, and Chimaera itself. Brachymylus appears more closely related to Callorhinchus than to Chimaera, and it is on this basis that it is assigned to the Callorhinchidae along with Pachymylus. The value of including extinct fossil genera in the present classification is questionable and is under review. Associated dentitions are extremely rare. Where other skeletal remains are pre- served, as, for instance, in the Chalk or Kimmeridgian, the plates are generally either crushed or impossible to free from the matrix without the destruction of the adjacent cartilage. The only comparable specimen known to the authors at present is an associated dentition of Edapliodou mirificus Leidy, from the Upper Cretaceous of New Jersey, U.S.A. (New Jersey State Museum registration no. 11301). A complete dentition of E. sedgwicki (Agassiz) from the Cambridge Greensand is on display in the Sedgwick Museum, Cambridge (S.M. B8802). It is, however, inferred from the account of Newton (1878, p. 8) and from their typical rolled and phosphatized condition, that the individual plates were not found in association and thus are unlikely to belong to a single individual. Plaster replicas of P.57041a-f can be obtained through the senior author (D. W.). Acknowledgements. The authors are indebted to Mrs. D. Ward for typing the manuscript, and to Messrs. J. Cooper, B. Gardiner, and C. Patterson for their helpful comments and criticisms. The photography was by Mr. T. Parmenter, casts by Mr. S. Baldwin, and the line drawings by Miss M. Holloway. REFERENCES NEWTON, E. T. 1878. The chimaeroid fishes of the British Cretaceous rocks, Mem. geol. Swv. U.K., Monogr. 4, 62 pp. PATTERSON, c. 1965, The phylogeny of the chimaeroids. Phil. Trans. Roy. Soc., London (B), 249, 101-219. WARD, D. j. 1973. The English Palaeogene chimaeroid fishes. Proc. Geol. Ass. 84, 315-330. WOODWARD, A. s. 1892. On some teeth of new chimaeroid fishes from the Oxford and Kimmeridge Clays of England. Ann. Mag. nat. Hist. (6), 10, 13-16. 19 12. The fossil fishes of the English Chalk. Part V. Palaeontogr. Soc. (Monogr.), 63, 153-184, pis. 33-38. D. J. WARD 35 Addington Road West Wickham Kent K. J. MCNAMARA Department of Geology and Mineralogy University of Queensland St. Lucia 4067 Queensland Typescript received 27 March 1976 Australia BIVALVED ARTHROPODS FROM THE CAMBRIAN BURGESS SHALE OF BRITISH COLUMBIA by D. E. G. BRIGGS Abstract. The new phyllocarid genus Perspicaris is proposed to include the type, Canadaspis dictynna Simonetta and Delle Cave, 1975, and P. recondita sp. nov., from the Middle Cambrian Burgess Shale of British Columbia, The two species are reconstructed in detail apart from the poorly preserved thoracic appendages. Hymenocaris? parva Walcott, 1912, from the same locality, is tentatively assigned to the genus Tiizoia Walcott, 1912. The material referred by Walcott (1912) to Hymenocaris Salter, 1853 is being re-examined as part of a study of the bivalved arthropods from the Burgess Shale. In this paper two of the specimens which he figured as //. ( ^ Canadaspis) perfecta (1912, pi. 31, figs. 2, 4) are shown to dilTer in the morphology of the telson and cephalic appendages from the others, and are placed in a new genus Perspicaris. Canadaspis dictynna Simonetta and Delle Cave, 1975, is redefined and designated the type species. Perspicaris, although lacking a rostral plate and abdominal appendages, is assigned to the Phyllocarida. A reinterpretation of the only known specimen of Hymenocaris? parva reveals the spinose nature of the carapace border. The evidence is inadequate, however, to determine the genus, and it is referred with a query to the phyllocarid Tuzoia. Terminology. The morphological terms used in the descriptions are those of Moore and McCormick (in Moore 1969) as far as possible; the telson is not considered to be a true somite. The sagittal plane is that passing vertically through the long axis of the body. The following symbols are used on the plates and text-figures : a, anus, ad, trace of carapace adductor muscle, al, alimentary canal, an, antenna, ap, appendage, b, border of carapace, c, cephalic region, cr, caudal ramus, e, eye. gu, gut contents, h, hinge line of carapace, is, inter-somite boundary. 1, prefix indicating left side, ms, muscle scar on carapace, n, nodular feature, p, cephalic appendage? beneath the antenna of GSC 45280. r, prefix indicating right side, t, telson. tl, t2, etc., trunk somites numbered posteriorly (assuming a total of 17). v, valve of carapace. Breaks of slope are represented by hachures, the solid line at the upper edge of the break, the hachures directed downslope. Stippled areas represent ‘outcrops’ of matrix within the outline of a specimen, unless other- wise indicated. The evidence upon which the reconstructions are based is illustrated, as far as possible, by the plates. Differences in level on the fossils are expressed by a minute ‘scarp’ on the specimen which either casts a shadow, or reflects light, depending on the angle of illumination. The photographs, except Plate 67, fig. 4 and Plate 72, figs. 4, 5, were taken on fine-grained, 35-mm panchromatic film in ultra-violet radiation. The radiation was directed at approximately 30° to the horizontal except where reflection was desirable, when the angle was increased to about 65°. Plate 67, fig. 4, was taken on fine-grained, half-plate, orthochromatic film, in ordinary light directed at a high angle, the specimen immersed in white spirit. Plate 72, figs. 4, 5, were taken through a Wild binocular microscope, the specimen illuminated by an intensity lamp with a green filter. An interpretation of the specimens is presented where necessary as an adjacent camera lucida drawing. The specimens were rotated in relation to a unidirectional light source during the preparation of these drawings; different aspects of the morphology are revealed by varying the direction and angle of illumination (indicated in the plate explanations). [Palaeontology, Vol. 20, Part 3, 1977, pp. 595-621, pis. 67-72.] H 596 PALAEONTOLOGY, VOLUME 20 TEXT-FIGS. 1, 2. Reconstructions of Perspicaris dictynna (Simonetta and Delle Cave, 1975). 1, lateral view, features beneath the carapace tentative. 2, dorsal view. Respositories. The following abbreviations are used: GSC— Geological Survey of Canada, Ottawa; ROM — Royal Ontario Museum, Toronto; SM— Sedgwick Museum, Cambridge; USNM— National Museum of Natural History, Washington, D.C. Preservation. Whittington (1971, pp. 1180-1196, 1198, fig. 24) discussed the preservation of Marrella splendens in detail, explaining the effect of variations in orientation to the bedding prior to compaction on the appearance of the fossil. Perspicaris shows a similar range of configurations. Specimens orientated in parallel aspect, the sagittal plane normal to the bedding, preserve the cephalic appendages, valves, and the trunk and telson symmetrically arranged about the mid-line (PI. 69, fig. 1). Specimens preserved in lateral aspect, the sagittal plane parallel to the bedding, show the valves approximately superimposed (PI. 67, figs. 1, 2). Examples also occur in an intermediate or oblique aspect, the outline of one valve approaching completeness, the other folded beneath itself (PI. 68, fig. 6; PI. 69, fig. 3). All eleven identified specimens of P. dictynna appear to have been complete when buried. Poorly preserved individuals, however, particularly those lacking the telson, can not be assigned to the species as they might equally be juveniles of P. recondita or Canadaspis perfecta. Isolated valves within the size range are at least as common as complete individuals, but the majority are probably those of juveniles of C. perfecta. Only two of the twelve known specimens of P. recondita, on the other hand, approach a degree of completeness (PI. 69, fig. 3; PI. 70, figs. 1, 2), and five consist only of posterior trunk somites and the telson. Isolated carapaces are usually difficult to distinguish from those of C. perfecta. Five of the specimens of P. fficn’nna are preserved in /utera/ aspect, four in parallel, and two in oblique. The majority of specimens of P. recondita, however, are preserved in parallel or parallel- oblique aspect, possibly partly due to the influence of the flattened caudal furca, and only the carapace is known in lateral aspect (PI. 72, fig. 3). The isolated carapace USNM 189244 (PI. 72, fig. 7) approaches a vertical-oblique orientation to the bedding (cf. M. splendens, Whittington 1971, p. 1187). BRIGGS: BURGESS SHALE ARTHROPODS 597 SYSTEMATIC DESCRIPTIONS Class MALACOSTRACA Latreille, 1806 Subclass PHYLLOCARiDA Packard, 1879 Order and Family uncertain Genus perspicaris gen. nov. Derivation of name. Latin: perspicax (sharp-sighted); caris (crab). Type species. Canadaspis dictynna Simonetta and Delle Cave, 1975. Other species. P. recondita sp. nov. Diagnosis. Carapace with hinge line, valves sub-oval, tapering anteriorly, rostral plate absent. Pedunculate eyes large, borne on an elongate projection of the cephalon. Abdominal somites lacking appendages, telson not posteriorly produced, caudal furca spinose. Geological horizon. Middle Cambrian, Stephen Formation, Burgess Shale section, Bathyuriscus-Elrathina Zone, British Columbia. Perspicaris dictynna (Simonetta and Delle Cave, 1975) Plates 67, 68; Plate 69, figs. 1,2; text-figs. 1-11 1975 Canadaspis ovalis (Walcott); Simonetta and Delle Cave pars, p. 12, pi. 5, fig. 3; pi. 40, figs. 22-24. 1975 Canadaspis sp. ; Simonetta and Delle Cave pars, pi. 40, fig. 11. 1975 Canadaspis dictynna Simonetta and Delle Cave pars, p. 12, pi. 5, fig. 4; pi. 43, fig. 14. Holotype. USNM 189280, part and counterpart (designated Simonetta and Delle Cave 1975), Plate 67, figs. 3-5, original of Simonetta and Delle Cave 1975, pi. 43, fig. 14. Other material. USNM 114244, 114254 with counterpart, 189242, 189245, originals of Simonetta and Delle Cave 1975, pi. 40, figs. 22, 24, 23, and 11 respectively; USNM 207245 with counterpart, 207246, 207247, 213804, 213833, and one additional specimen. USNM 213805 with counterpart, 213842 and 213850 may belong to the species. Diagnosis. Furcal rami elongate, bearing a row of spines laterally, dorsally, and ventrally. Locality and stratigraphical horizon. All the material bears the USNM locality number 35k, i.e. the ‘Phyllopod bed’ in the Walcott Quarry (see Fritz 1971, for an account of the stratigraphy). No specimens were collected by the GSC expeditions (Whittington 1971); no isolated carapaces were found which correspond in shape or size to that of P. dictynna. The fauna associated with the USNM specimens is confined to Canadaspis perfecta, Waptia fieldensis, Sidneyia inexpectans, Pagetia hootes, Ottoia prolifica, and unidentifiable frag- mentary material, and affords no precise indication of the levels in the quarry from which they were obtained. DESCRIPTION Cephalic region. The cephalon is poorly defined even when exposed by exfoliation of the carapace (PI. 68, fig. 6), or the partial loss (PI. 67, figs. 1, 2; PI. 68, fig. 5), or removal (PI. 67, fig. 4) of the overlying valves. The anterior margin is gently curved, convex anteriorly (PI. 67, fig. 7 ; PI. 69, fig. 2, ventral view) in parallel aspect, but only a suggestion of the margins is afforded by USNM 1 14244 (PI. 67, figs. 1, 2) and 189280 (PI. 67, fig. 4) in lateral aspect, and an accurate reconstruction of the outline is impossible. A pair of large. 598 PALAEONTOLOGY, VOLUME 20 TEXT-FIG. 4 EXPLANATION OF PLATE 67 Figs. 1-8. (Simonetta and Delle Cave, 1975). 1,2,USNM 1 14244, lateral : l,east, x5; 2, north, reflected, x5; original of Simonetta and Delle Cave 1975, pi. 40, fig. 22; right valve largely missing revealing ‘body’ layer; text-fig. 3. 3-5, USNM 189280, part and counterpart, lateral: 3, east, reflected, x5; 4, north, alcohol, x 5, right valve removed to reveal thoracic appendages; 5, north, reflected, x 5; original of Simonetta and Delle Cave 1975, pi. 43, fig. 14; text-fig. 4. 6, USNM 207247, oblique, east, x5; text-fig. 5. 7, 8, USNM 189242, parallel, ventral aspect; 7, north, x5; 8, east, reflected, x 5, showing abdomen and telson; original of Simonetta and Delle Cave 1975, pi. 40, fig. 23; text-fig. 6. PLATE 67 BRIGGS, Perspicaris from the Burgess Shale 600 PALAEONTOLOGY, VOLUME 20 EXPLANATION OF PLATE 68 Figs. 1-7. Perspicaris dictynna (Simonetta and Delle Cave, 1975). 1-3, USNM 207245, part and counter- part, parallel; 1, north-east, x5, carapace partly removed revealing telson; 2, north, x5; 3, east, reflected, x 10, showing antennae; text-fig. 7. 4,USNM 1 14254, parallel, north, X 5, original of Simonetta and Delle Cave 1975, pi. 40, fig. 246; text-fig. 8. 5, USNM 207246, lateral, west, x 10, trunk apparently rotated through 90° so that the dorsal side is uppermost; text-fig. 9. 6, 7, USNM 189245, oblique: 6, north-west, X 5; 7, north, x 10, part of carapace removed to show traces of appendages; original of Simonetta and Delle Cave 1975, pi. 40, fig. 11; text-fig. 10. PLATE 68 BRIGGS, Perspicaris from the Burgess Shale 602 PALAEONTOLOGY, VOLUME 20 highly reflective, ovoid features (PI. 67, fig. 2) borne on an elongate, distally expanding, projection of the cephalon are interpreted as eyes. They may be preserved superimposed on the anterior margin of the carapace (PL 67, fig. 7) or extending beyond it (PI. 69, figs. 1, 2), suggesting that the projection was flexible. The eyes are suboval in outline in parallel (PI. 68, fig. 4) and oblique aspect (PI. 68, fig. 6), tapering slightly proximally, but subcircular in lateral aspect (PI. 67, fig. 2). The highly reflective distal area preserved on some specimens (PI. 67, fig. 2) may represent the visual surface; a defined subcircular area on the left eye of USNM 207247 (PI. 67, fig. 6) may be similar in origin. The cephalic region bore a pair of stout, elongate, segmented antennae attached ventral of the eyes (PI. 67, figs. 1, 2). The antennae appear to have been subcircular in cross-section, tapering gradually distally and composed of at least fourteen segments (evident on USNM 207246, PI. 68, fig. 5; USNM 207245, PI. 68, figs. 1-3). The segments became more elongate towards the distal extremity of the appendage; individually they increased in cross-section distally, each one inserting into the anterior margin of that proximal to it. The anterior margin of the segments, apart from, apparently, the most distal, bore a fringe of elongate spines extending laterally a distance approaching the width of the segment (PI. 68, figs. 3, 5). The antennae were flexible; they are preserved directed forward, curved to the left (PI. 67, fig. 7) or right (PI. 68, figs. 1-3), or downward (PI. 67, figs. 1, 2). The maximum known anterior extent of the alimentary canal is preserved on USNM 213804 (PI. 69, figs. 1, 2) but the trace terminates at a point which is probably posterior of the cephalon. There is no indication of the labrum. Two pairs of nodular features are preserved flanking the hinge line just posterior of the attachment of the cephalic appendages of USNM 213804 (PI. 69, fig. 2). Thesenodesmay result from the nucleation of pyrite (Whittington 1971, p. 1 180). The posterior pair is elongate normal to the hinge and may indicate the posterior margin of the cephalon. The anterior pair are slightly elongate parallel to the hinge and may represent a paired cephalic organ such as the antennal nephridium. Carapace. A bivalved carapace loosely covered the anterior part of the body, including the proximal parts of the antennae and eye stalk and part of the trunk appendages. Five trunk somites, in addition to the telson, are preserved extending beyond the carapace of USNM 1 14244, in lateral aspect (PI. 67, figs. 1, 2) but this number varies from four (PI. 68, fig. 5), or even less (PI. 67, figs. 3, 5, presumably due to distortion), to six or seven (PI. 67, fig. 6; PI. 69, fig. 1 ). The carapace was apparently only attached to the anterior of the body; the greater part of the trunk could move independently of it (PI. 68, figs. 4, 5). Dark, reflective, subcircular areas which occur in the anterior apices of the valves are interpreted as traces of muscle scars, and indicate that the attachment was cephalic. They have no apparent relief on the dorsal surface of the carapace, but are slightly raised on the ventral (PI. 67, fig. 7; PI. 69, figs. 1, 2). A crescentric, reflective area on the adaxial margin of the muscle scars of USNM 213804 (PI. 69, fig. 2) may be a trace of the adductor muscle; its attachment to the body may be represented by a dark, reflective, subcircular area near the base of the antenna of USNM 1 14244 (PI. 67, figs. 1, 2). The valve was suboval in outline, tapering anteriorly and expanding slightly postero-ventrally. The anterior margin is usually obscured by exfoliation (PI. 68, figs. 1, 6) or compaction against the cephalic appendages, but appears to have been gently rounded (PI. 67, fig. 7). The hinge line is approximately straight in lateral (PI. 67, figs. 1, 2) and parallel aspect (PI. 68, fig. 4), but its anterior extension is unknown. There is no evidence that a rostral plate was present, but the hinge was produced very slightly posteriorly (PI. 67, figs. 1, 2). The posterior margin of the valve diverged from the hinge line at an angle of about 110° (PI. 67, figs. 1, 2), creating a shallow embayment between the valves (PI. 68, fig. 4) similar to that at the anterior margin (PI. 67, fig. 7). In the absence of evidence to the contrary the valves are assumed to have been joined by a band of flexible cuticle, which permitted variations in the degree to which they were approximated by the adductor muscles. An indication of the original convexity of the carapace is provided by the relief of some specimens (PI. 68, figs. 1, 2) and the concentric folds which parallel the ventral margin of the flattened valves (PL 67, fig. 7 ; PL 68, fig. 4). A wide border, sloping slightly abaxially, was bounded on its inner margin by a narrow ridge on both the exterior (PL 68, fig. 5) and interior (PL 67, fig. 7) surfaces of the valves. The carapace was smooth otherwise, apart from the muscle scars, and wrinkles and folds acquired during preservation (PL 68, fig. 5). The border appears to follow the hinge line on USNM 114244 (PL 67, figs. 1, 2) but this is not an original feature and may be the result of folding parallel to the hinge during compaction. There is no evidence that the border was sculptured, but this may be a function of the small size of the specimens. BRIGGS; BURGESS SHALE ARTHROPODS 603 Trunk. The anterior somites of the trunk are usually obscured by the carapace, and removal of the latter (PI. 67, figs. 3, 4), where feasible, has revealed little detailed evidence of their configuration. The 7 posterior- most somites of the trunk appear to have lacked appendages (PI. 67, figs. 1, 2, 4; PI. 68, fig. 7) although those of the preceding somites may be compacted against them. There appear to have been 10 appendage- bearing somites. The strongest evidence for this number depends on the assumption that each somite bore a single pair of appendages— 10 limbs, presumably paired, were revealed by the removal of the right valve of USNM 189280 (PI. 67, fig. 4). Extrapolation based on serially arranged, reflective traces on USNM 1 14244 (PI. 67, fig. 2) and 213804 (PI. 69, fig. 2) supports this figure. The trunk thus appears to have con- sisted of a thorax of 10 appendage-bearing somites and an abdomen of 7 somites, in addition to the telson. The somites are henceforth numbered posteriorly from 1 to 17 (see reconstruction, text-figs. 1, 2). The height of the somites diminishes gradually posteriorly in lateral and oblique aspect (PI. 67, figs. 1,2; PI. 68, fig. 7), this feature becoming more marked posterior of somite 16, and is greater in lateral (PI. 67, figs. 1 , 2) than in parallel (PI. 68, fig. 4) or oblique aspect (PI. 68, fig. 6) indicating that the trunk was suboval in cross-section. A series of dark, reflective bands on the thorax of USNM 1 14244 (PI. 67, figs. 1 , 2) probably represents traces of the inter-somite boundaries (cf. Yohoia plena, Whittington 1974) and indicates that the thoracic somites were much shorter (sagitally) than those of the abdomen. The latter appear to have increased slightly in sagittal length posteriorly but this may be obscured by the curvature of the trunk (PI. 68, fig. 7). Traces of the abdominal inter-somite boundaries offset on opposite sides of the trunk are evident on some specimens (PI. 69, figs. 1, 2). The posterior margin of each somite was fringed by up to forty short, stout spines (PI. 68, fig. 5). The trunk was very flexible and is preserved curved to the right (PI. 67, fig. 6) and left (PI. 68, fig. 6), ventrally (PI. 68, fig. 5; PI. 67, figs. 3, 5), and even apparently curved through almost 180° beneath the carapace (PI. 68, fig. 1 ; the trunk of this specimen may be disarticulated). Flexure was achieved by varying the degree of overlap along the inter-somite boundaries; the lateral margins of individual somites are shorter on the concave side of the trunk (PI. 68, fig. 7; PI. 67, figs. 3-5). The telson was suboval in cross-section as the height is greater in lateral (PI. 67, figs. 1, 2) than the width in parallel aspect (PL 68, fig. 4). The furcal rami are similar in dimension in both lateral (PI. 67, figs. 1, 2) and parallel specimens (PI. 67, fig. 7). The dorsal and outer margins were slightly concave, the ventral and inner more markedly convex (PI. 67, figs. 1, 2; PI. 69, fig. 1), the rami tapering to a point distally. Each ramus bore four symmetrically arranged rows of short, posteriorly directed spines, one pair in a vertical plane, the other transverse. One pair is usually preserved in outline, the vertical in lateral aspect (PI. 67, figs. 1-5), the transverse in parallel (PI. 69, fig. 1), as it is compressed into the plane of bedding. One of the rows normal to the plane of bedding is preserved as a series of ridges or grooves (PI. 68, figs. 5, 7) depending upon which side of the part or counterpart it remains; the other may appear in relief, com- pressed through the cuticle from the reverse side (the left ramus of USNM 189245, PI. 68, fig. 7). The dorsal, ventral (PI. 67, figs. 1, 2), and outer rows included up to twelve evenly distributed, stout spines, the inner row up to sixteen finer and more closely spaced (PI. 68, figs. 5, 7). The anus was situated mid-ventrally on a slight projection flanked by a spinose caudal furca (PI. 67, figs. 1, 2; PI. 69, fig. 1). The furcal rami diverged to varying degrees (cf. PI. 68, fig. 4 and PI. 69, fig. 1) but there is no evidence to confirm that they articulated with the telson. Evidence of the alimentary canal is preserved in seven of the eleven specimens. This may consist of a relief trace, due to an original sediment fill (PI. 68, fig. 4; PI. 69, fig. 1 ), or a reflective strip (PI. 67, fig. 8). Where both types of preservation occur on a single specimen (PI. 67, figs. 1, 2) the width of the reflective trace may be variable, and considerably less than that preserved in relief; it may not reliably represent the original. The relief trace occupies up to one-third of the width of the trunk somites just posterior of the carapace (PI. 67, figs. 1, 2; PI. 68, fig. 4). The alimentary canal was presumably subcircular in cross-section, as the sediment-filled outline is similar in both lateral (PI. 67, fig. 2) and parallel (PI. 68, fig. 4) aspect. It was situated mid-ventrally, at least in those somites which extended posteriorly beyond the carapace. Traces of the alimentary canal extend anteriorly into the thoracic somites (PI. 67, figs. 1, 2; PI. 69, figs. 1, 2). No evidence of gut diverticula has been observed. The darker colour of the sediment fill on USNM 213804 (PI. 69, figs. 1, 2), relative to the surrounding cuticle, may be due to the gut contents. Thoracic appendages. Evidence for the arrangement and character of the appendages is slight due to inadequate preservation and the small size of the specimens. Removal of the right valve of USNM 189280 (PI. 67, figs. 3, 4), has revealed evidence of the presence of ten poorly preserved appendages. These appear to have been large, flattened, lamellate, suboval features, overlapping posteriorly. Evidence of flattened 604 PALAEONTOLOGY, VOLUME 20 appendages is also preserved in parallel (PI. 69, fig. 1) and oblique aspect (PI. 68, fig. 7). There is no unequivocal evidence that they were biramous. Very tenuous reflective and relief traces on the appendages of USNM 213804 (PI. 69, figs. 1, 2) may represent the outline and claws of an ambulatory ramus, but these have proved impossible to photograph. Ventral corrugations corresponding to the reflective bands on the thorax of USNM 114244 (PI. 67, figs. 1, 2) may also represent this postulated segmented ramus. The thoracic appendages are not reconstructed in detail (text-fig. 1). Size. Both the flexibility of the trunk and the flattening of the carapace in several orientations, allied to its incompleteness in some specimens, impose limitations on the accuracy of an assessment of the size range. Values for the maximum length of the carapace parallel to the hinge line (/) and the total sagittal length (L) from the anterior margin of the carapace to the distal extremity of the caudal furca are as follows: mean / = 1 1-33 mm, variance = 6-32, N=9\ mean L = 22-4 mm, variance = 21 -79, N = l. The fraction of the total length (L) occupied by the carapace (/): mean -=0-54, variance 00021, N=l. The size ranges between USNM 207245 (PI. 68, figs. 1, 2), 1=1-5 mm, and USNM 213804 (PI. 69, figs. 1, 2)J = 16-5 mm, L = 29-0 mm. The relative dimensions of the carapace are most satisfactorily shown by USNM 114244 (PI. 67, figs. 1, 2); it is 11-6 mm long and 5-2 mm high normal to the hinge (these figures can not allow for the original convexity). The hinge line is too poorly preserved anteriorly to permit measurement. EXPLANATION OF PLATE 69 Figs. 1, 2. Perspicaris dictynna (Simonetta and Delle Cave, 1975). USNM 213804, parallel, ventral aspect : I, north-west, x 3 ; 2, north, reflected, x 3; text-fig. 11. Figs. 3-5. Perspicaris recondita gen. et sp. nov. USNM 114255, parallel-oblique: 3, west, x2; 4, north- east, X 4, showing posterior trunk somites and telson ; 5, north, reflected, x 4, showing eyes and antennae ; original of Simonetta and Delle Cave 1975, pi. 53, fig. 6; text-fig. 12. PLATE 69 BRIGGS, Perspicaris from the Burgess Shale 606 PALAEONTOLOGY, VOLUME 20 Perspicaris recondita gen. et sp. nov. Plate 69, figs. 3-5; Plates 70, 71 ; Plate 72, figs. 1-7; text-figs. 12-24 Derivation of species name. Latin: recondita (concealed). 1912 Hymenocaris perfecta Walcott pars, pp. 152-153, 183-185, 222, pi. 31, figs. 2, 4. 1929 Hymenocaris perfecta Walcott; Gurich pars, pp. 41, 42. 1929 ‘'Hymenocaris' perfecta’, Gurich pars, p. 39, fig. 2, no. la. 1975 Canadaspis perfecta (Walcott); Simonetta and Delle Cave pars, pi. 38, fig. 6. 1975 Canadaspis cfr. obesa Simonetta and Delle Cave pars, pi. 39, figs. 9, 10. 1975 Canadaspis dictynna Simonetta and Delle Cave pars, p. 12, pi. 39, fig. 11. 1975 1 Carnavonia venosa Walcott; Simonetta and Delle Cave pars, p. 13, pi. 36, fig. 2. 1975 Protocaris pretiosa Resser; Simonetta and Delle Cave pars, p. 13, pi. 53, figs. 5, 6. Holotype. LfSNM 114255 (designated herein), Plate 69, figs. 3-5, original of Simonetta and Delle Cave 1975, pi. 53, fig. 6. Other material. USNM 57704 part and SM A 1709 counterpart, former original of Walcott 1912, pi. 31, fig. 2; Simonetta and Delle Cave 1975, pi. 38, fig. 6. USNM 57706, original of Walcott 1912, pi. 31, fig. 4; line drawing of Gurich 1929, pi. 39, fig. 2, no. la; Simonetta and Delle Cave 1975, pi. 39, fig. 9, and counterpart. USNM 1 14245 with counterpart, 189172, 189240 with counterpart, originals of Simonetta and Delle Cave 1975, pi. 39, figs. 11, 10, pi. 53, fig. 5 respectively. USNM 207312, 207313, GSC 45280 with counterpart, ROM 34305. USNM 189244, original of Simonetta and Delle Cave 1975, pi. 36, fig. 2, and 207314, with counterparts, are isolated carapaces. Diagnosis. Furcal rami flattened, leaf like, with spinose lateral margins and median ridge. TEXT-FIGS. 13, 14. Reconstructions of Perspicaris recondita gen. et sp. nov. 13, dorsal view. 14, lateral view. BRIGGS: BURGESS SHALE ARTHROPODS 607 Locality and stratigraphical horizon. The USNM specimens bear the locality number 35k, except for USNM 114255 and 207313 which are not labelled, but all were presumably collected from the ‘Phyllopod bed’ in the Walcott Quarry. The single identifiable specimen collected by the GSC expeditions (Whittington 1971 ) came from the level 7 ft 4 in. to 7 ft 8 in. which also yielded abundant specimens of Canadaspis perfect a, several of which are also present on the slab. All the USNM specimens of Perspicaris recondita are on small pieces with only an incomplete agnostid and unidentifiable fragments in association, which do not indicate their level in the quarry. DESCRIPTION Cephalic region. The cephalon bore a pair of pedunculate eyes and elongate antennae (PI. 69, figs. 3, 5) similar to those of P. dictynna. Removal of the carapace anteriorly from USNM 189240 (PI. 71, figs. 4, 6), revealed an irregular amorphous area proximal of the antennae which may represent part of the cephalic region. This area is discontinuous laterally and posteriorly, presumably due to the effects of decay. The eyes were borne at the antero-lateral corners of a distally tapering projection of the cephalon, wider than that in P. dictynna, which terminated in a gently convex anterior margin (PI. 69, figs. 3, 5; PI. 71, fig. 2). There is no evidence that this projection was segmented, but a degree of flexibility is indicated by a slight inclination to the right and hence dorsally on USNM 1 1 4255 (PI. 69, fig. 3) and in the same direction, and therefore ventrally, on GSC 45280 (PI. 71, fig. 1), but this may be an effect of orientation. The outline of the eyes and the stalk upon which they were borne can not be deduced in cross-section in the absence of a specimen preserved in lateral aspect, but is assumed to have been subcircular for the purposes of reconstruction (text-figs. 13, 14). The antennae included at least sixteen segments which are evident on the right antenna of USNM 189240 (combining the evidence of part and counterpart, PI. 71, figs. 6, 7). A group of small, closely spaced spines, revealed by the removal of the carapace overlying the cephalic region on the part of USNM 189240 (PI. 71, fig. 6), may have projected laterally from a proximal segment. The antenna appears to have terminated in several small spines (PI. 71 , fig. 7), and was clearly flexible. Removal of part of the carapace of GSC 45280 (PI. 71, fig. 3 ; text-fig. 19) revealed the presence of a small projection or appendage emerging laterally from beneath the proximal segments of the right antenna. The nature of this projection is unknown, but it appears to have been divided into at least seven short, wide segments which extended laterally into small, blunt processes, and it may represent a second antenna. It is omitted from the reconstruction (text-fig. 14). The maximum known anterior extension of the alimentary canal is preserved on USNM 57704/SM A 1709 (PI. 70, figs. 1, 2) but the trace terminates at a point posterior of the cephalic region. A small, spinose appendage which projects anteriorly from beneath the right valve of USNM 207312 (PI. 72, figs. 1, 3) may be cephalic. The distal extremity bore a series of closely spaced, fine, elongate, ventrally curved spines along the ventral margin. The dorsal margin was smooth and appears to be gently curved, convex dorsally. The proximal outline of the appendage, exposed by a removal of the overlying valve, is poorly defined, and the limb may not be in situ. It is not included in the reconstruction (text-figs. 13, 14) for this reason. Carapace. The carapace was similar in outline and attachment to that of P. dictynna. The muscle scars are likewise flanked on some specimens by dark reflective features which may represent traces of the adductor muscles (PI. 70, figs. 1, 2; PI. 71, fig. 2). Two small, adjacent oval features preserved posterior of the cephalic appendages of USNM 1 14255 (PI. 69, fig. 3) may represent the attachment of the adductor muscles to the cephalon. The hinge line is slightly convex dorsally in lateral aspect on USNM 207312 (PI. 72, fig. 3), but this may be an effect of compaction. Its posterior extremity was produced into a small, blunt triangular area (PI. 72, fig. 3; PI. 71, figs. 4, 5). The hinge line is obscured anteriorly on the specimens preserved in parallel (PI. 70, figs. 1, 2) and parallel-oblique aspect (PI. 69, fig. 3; PI. 71, figs. 1, 4, 5) but there is no evidence that it was similarly produced in this direction. Both the anterior and posterior margins of the valve diverged from the hinge at angles of 120°- 130° (PI. 72, fig. 3; PI. 70, figs. 1, 2), but the posterior embayment of the carapace was deeper than the anterior due to the extension of the valves postero-ventrally . The valves are assumed to have been joined by a band of flexible cuticle, such as that postulated for P. dictynna. An indication of the original convexity of the carapace is provided by the closely spaced concentric folds around the ventral margins of the valves of USNM 57704/SM A1709 (PI. 70, figs. 1, 2), for example. The carapace is usually smooth apart from such folds and wrinkles, the adductor muscle scars, and a border which sloped slightly abaxially and was bounded on its inner margin by a shallow groove (PI. 70, figs. 1, 2; PI. 71, figs. 1, 4, 5). The border was covered in a vermicular pattern of short. 608 PALAEONTOLOGY, VOLUME 20 EXPLANATION OF PLATE 70 Figs. 1-7. Perspicaris recondita gen. et sp. nov. 1-3, USNM 57704, part, and SM A1709, counterpart, parallel: 1, USNM 57704, east, reflected, x2, original of Walcott 1912, pi. 31, fig. 2, Simonetta and Delle Cave 1975, pi. 38, fig. 6; 2, 3, SM A 1709: 2, north-east, x2; 3, south, reflected, x4, showing telson; text-fig. 15. 4, USNM 114245, parallel, north, x4, original of Simonetta and Delle Cave 1975, pi. 39, fig. 1 \b\ text-fig. 16. 5, USNM 189172, parallel, north, reflected, x 3, original of Simonetta and Delle Cave 1 975, pi. 39, fig. 10; text-fig. 1 7. 6, 7, USNM 57706, part and counterpart, parallel : 6, south, reflected, x 3, original of Walcott 1912, pi. 31, fig. 4, Simonetta and Delle Cave 1975, pi. 39, fig. 9; 7, east, reflected, x 3; text -fig. 18. PLATE 70 BRIGGS, Perspicaris from the Burgess Shale 610 PALAEONTOLOGY, VOLUME 20 closely spaced, elongate ridges orientated parallel to the margin (PI. 72, fig. 5), which may be virtually invisible depending on the nature of the preservation. A reticulate pattern occurs on the carapace of USNM 207312 (PI. 72, figs. 3, 4) and 189244 (PI. 72, fig. 7), but is absent on the other specimens (see Discussion). Trunk. The anterior somites of the trunk are obscured by the overlying carapace, and even where the latter is partly lacking due to exfoliation or fortuitous splitting of the fossil (PI. 69, fig. 3) no evidence of their morphology has been observed. A series of highly reflective areas preserved on the trace of the alimentary canal on the part of USNM 57704/SM A 1709 (PI. 70, fig. 1) may reflect the arrangement of the adjacent somites, but they can not be accurately enumerated. Nine posterior somites are evident on USNM 207312 (PI. 72, fig. 2) in addition to the telson, seven on USNM 114245 (PI. 70, fig. 4), and at least eight on USNM 1 14255 (PI. 69, figs. 3, 4). The trunk somites are numbered assuming a total of seventeen as in P. dictynna (text-figs. 13, 14). All the known examples of the posterior trunk somites and telson are preserved in parallel aspect. The trunk diminished gradually in width posteriorly to the anterior margin of the pre-telson somite, which was slightly wider than that preceding it (PI. 72, fig. 2; PI. 70, fig. 4). The posterior margin of each somite was fringed by up to fifty, closely spaced, elongate spines (PI. 70, fig. 4). The inter-somite boundaries are preserved in relief (PI. 69, fig. 4) due to an overlap of the cuticle of successive somites, and this is parti- cularly evident on USNM 207312 (PI. 72, figs. 2, 3), which preserves the cuticle of both sides of the abdomen. The trunk was presumably flexible, although there is little evidence to support this contention apart from EXPLANATION OF PLATE 71 Figs. 1-7. Perspicaris recondita gen. et sp. nov. 1-3. GSC 45280, part and counterpart, parallel-oblique: 1, part, east, x 1-5; 2, counterpart, east, reflected, x 3, showing cephalic region ; 3, part, west, x 6, show- ing eyes, and small appendage? ventral of right antenna revealed by removal of carapace in this area; text-fig. 19. 4-7, USNM 189240, part and counterpart, oblique; 4, part, north, x 1-5; 5, counterpart, north-east, x 1-5, original of Simonetta and Delle Cave 1975, pi. 53, fig. 5; 6, part, east, x 3, showing cephalic? region revealed by removal of part of carapace; 7, counterpart, north, x 6, showing antennae revealed by removal of anterior margin of left valve; text-figs. 20, 21. PLATE 71 BRIGGS, Perspicaris from the Burgess Shale 612 PALAEONTOLOGY, VOLUME 20 the configuration of the somites of USNM 57704/SM A1709 (PI. 70, figs. 2, 3) which appear to have been compacted at a high angle to the carapace, possibly due to a pronounced ventral curvature. The sagittal length of successive somites appears to have decreased slightly anteriorly (PI. 72, fig. 2; PI. 69, fig. 4) as in P. dictynna. The cross-section is assumed to have been subcircular (text-figs. 13, 14). The telson was shorter than the preceding trunk somite, and bore a pair of broad, flattened, spinose furcal rami flanking the anus distally. Examples preserved in exactly parallel aspect (PI. 69, fig. 4; PI. 72, fig. 2) show that the outer margin of each ramus was slightly convex and the inner margin more strongly so, the ramus expanding rapidly posteriorly to a maximum width in about one-quarter the sagittal length, and tapering gradually distally to an elongate point. A slight obliquity of compaction may distort the outline or apparent width of the rami, the outer margin of one becoming slightly concave and that of the other almost straight (PI. 70, figs. 6, 7; PI. 72, fig. 6). Each ramus bore a series of posteriorly directed spines; up to eleven short, stout, and evenly spaced on the outer margin and over twenty, which became more elongate and closely spaced anteriorly, on the inner (PI. 70, figs. 5-7 ; PI. 72, figs. 2, 6). A ridge extended along the abaxial area of the ramus parallel to the outer margin and tapered towards the distal extremity (PI. 72, fig. 2; PI. 69, fig. 4). There is no evidence that this ridge was spinose. A similar feature is assumed to have been present on both the dorsal and ventral surface of the ramus although this is impossible to verify without a specimen preserved in lateral aspect. An indication of the original convexity is provided by the right ramus of USNM 207313 (PI. 72, fig. 6), which has been flattened in a slightly oblique orientation. The anus appears to have been situated slightly dorsal of the caudal furca. The alimentary canal is preserved in positive relief above the furcal rami on USNM 1 14255 (PI. 69, figs. 3, 4), which affords a dorsal view, and below them, in ventral aspect, on SM A 1709 (PI. 70, fig. 2). The posterior margin of the pre- telson somite traversed the trunk just anterior to the attachment of the caudal furca (PI. 69, fig. 4; PI. 72, fig. 2). The telson was gently convex posteriorly (PI. 72, fig. 2; PI. 70, fig. 5), and extended over the attach- ment of the furcal rami (PI. 69, fig. 4; PI. 70, fig. 4). USNM 207312 (PI. 72, fig. 2) appears to afford a ventral view of the telson; the caudal furca lies at the same level as the exposed (uppermost) side of the trunk, and the cuticle of the telson lying between the rami is at a lower level and thus apparently dorsal. A feature preserved between the furcal rami of USNM 114255 (PI. 69, figs. 3, 4), extending ventrally beyond the trace of the alimentary canal, may represent cuticle which supported the anus. Evidence for the presence of an articulation at the base of the furcal rami is confined to an apparent thickening of the cuticle at this point (PI. 72, fig. 2) which may extend anteriorly along the lateral margin of the pre-telson somite (PI. 70, fig. 5). The expansion of this somite relative to those preceding it suggests that it may have accommodated muscles employed in movement of the furca. The course of the alimentary canal anterior of the telson is evident on only two specimens, USNM 57704/SM A1709 (PI. 70, figs. 1, 2) and 114255 (PI. 69, figs. 3, 4), but in both cases it is preserved in relief, presumably due to a sediment fill. It follows the mid-line of the trunk in parallel aspect, occupying about one-sixth of the width of the somites just posterior of the carapace. The trace of the canal, although distorted, extends anteriorly almost as far as the carapace muscle scars on USNM 57704/SM A 1709 (PI. 70, figs. 1, 2), but there is no indication of its course in the cephalic region. No evidence for the presence of gut diverticula has been observed. The wall of the canal appears to have been annulated, but this may be a feature of preservation. The dark colour of the trace on USNM 1 14255 (PI. 69, figs. 3,4) may be due to the gut contents. No evidence for the arrangement or morphology of the trunk appendages (other than the caudal furca) has been revealed by detailed examination or preparation of the known specimens, apart from poorly preserved traces on ROM 34305, which may represent lamellate rami. Appendages do not, however, appear to have been borne by at least seven or eight somites anterior of the telson. Size. The same considerations apply as to P. dictynna. Mean / ^ 44-25 mm, variance 34-92, N A. L can only be measured for two specimens: USNM 1 14255 (PI. 69, fig. 3), L = 57 mm, IjL =- 0-63; USNM 57704/ SM A 1709 (PI. 70, figs. 1, 2), L = 50 mm, IjL = 0-90 (this value is disproportionately high due to the orienta- tion of the posterior trunk somites during compaction). The remaining specimens are either distorted due to flattening in an oblique orientation to the bedding or too fragmentary to permit comparison. The size ranges between USNM 1 14255 (PI. 69, fig. 3), /= 36 mm, L = 57 mm, and USNM 207312 (PI. 72, fig. 3), / ^ 50 mm. The relative dimensions of the carapace can be most accurately measured on the right valve of USNM 207312 (PI. 72, fig. 3), which is 50 mm long and 28 mm high (these values can not allow for the original convexity). The antero-dorsal apex of this valve is lacking, however, preventing measurement of the hinge line. BRIGGS; BURGESS SHALE ARTHROPODS 613 DISCUSSION Previous descriptions. Walcott (1912, pi. 32, figs. 5, 6) described Hyrnenocaris ovalis on the basis of two specimens, USNM 57714 and 57715. Simonetta and Delle Cave (1975) identified USNM 57715 as Canadaspis perfecta (pi. 38, fig. 8) and designated USNM 57714, an isolated valve, as the lectotype of C. ovalis, reconstructing the species on the evidence of three additional specimens, USNM 114244 (PI. 67, figs. 1, 2) 1 14254 (PI. 68, fig. 4), and 189242 (PI. 67, fig. 7). An isolated valve is not considered a reliable basis for a species due to the over-all similarity of the carapaces of Canadaspis and Perspicaris, for example, and the pronounced variation in outline caused by different orientations to the bedding. USNM 1 14244, 1 14254, and 189242 are there- fore removed from C. ovalis (which is left occupied by the indeterminate lectotype alone) and referred to C. dictynna Simonetta and Delle Cave, 1975, as they are con- specific with the holotype of this species, USNM 189280 (PI. 67, figs. 3-5). The second specimen referred by Simonetta and Delle Cave to C. dictynna, however (USNM 1 14245, pi. 39, fig. 1 1), differs in the morphology of the caudal furca, and is placed in P. recondita. Simonetta and Delle Cave’s reconstructions of C. dictynna and C. ovalis (pi. 5, figs. 4 and 3 respectively) are thus largely based on individuals considered herein to belong to the same species of Perspicaris. There is little evidence to support either the occurrence of the thirteen pairs of elongate ’legs’ depicted on their reconstruction of C. ovalis (pi. 5, fig. 3), or their contention (p. 12) that USNM 1 14254 (PL 68, fig. 4) indicates that ‘probably the first two or three pairs of legs were somewhat specialized as mouth parts or as grasping organs’ (cf. PL 67, fig. 4). Walcott ( 1912) assigned USNM 57704 (PL 70, fig. 1) and 57706 (PL 70, figs. 6, 7), referred herein to P. recondita, to Hyrnenocaris (\.q. Canadaspis) perfecta. He observed (1912, p. 183) that USNM 57704 ‘shows the antennae to be jointed’, but added (p. 184), with reference to the same specimen, that ‘they may, however, be straight, unjointed and long’. This confusion may have arisen as a result of traces of extraneous organic matter in the vicinity of the antennae (PL 70, fig. 2). Walcott (1912, p. 222) considered that USNM 57704 shows ‘traces of the basal joints of the legs’ but it is not clear from his figure (1912, pi. 31, fig. 2) to which features he was referring; the reflective areas which flank the alimentary canal (PL 70, fig. 1) provide little support for his contention. Walcott (1912, p. 184) stated that ‘the terminal segment’ of H. (= Canadaspis) perf ecta has ‘from 2 to 6 cercopods attached to it’, and illustrated the former configuration by USNM 57706 (1912, pi. 31, fig. 4). The telson of P. recondita (USNM 57706, PL 70, figs. 6, 7), however, bore a true caudal furca, whereas the distal ‘ventral projections’ in C. perfecta extended from the pre-telson somite. These ‘ventral projections’ were also paired, but deeply divided into spines which Walcott erroneously interpreted as individual ‘cercopods’. Several subsequent authors (Henriksen 1928; Gurich 1929; Stormer 1944) commented on this mis- conception, but failed to note the fundamental difference between the distal morpho- logy of USNM 57706 (PL 70, figs. 6, 7) and the specimens of C. perfecta which Walcott also figured (1912, pi. 31, figs. 3, 5). Simonetta and Delle Cave (1975) assigned USNM 57704 (pi. 38, fig. 6) to C. perfecta, but removed USNM 57706 (pi. 39, fig. 9) and referred it, together with USNM 189172 (pi. 39, fig. 10; PL 70, fig. 5), to C. cfr. ohesa. Their species C. obesa, however, is 614 PALAEONTOLOGY, VOLUME 20 based mainly on USNM 189019 (cited as USNM 189258, pi. 39, fig. 1) which appears to be a specimen of C. perfecta with a poorly preserved telson. Four additional specimens identified herein as P. recondita were also figured by Simonetta and Delle Cave. USNM 114255 (pi. 53, fig. 6; PI. 69, fig. 3) and 114245 (pi. 39, fig. 11; PI. 70, fig. 4), which show the caudal furca, were assigned to Protocaris pretiosa and C. dictynna respectively; USNM 189240 (pi. 53, fig. 5; PI. 71, figs. 4, 5) and 189244 (pi. 36, fig. 2; PI. 72, fig. 7), preserving a combination of characteristic features including the vermicular carapace border, to P. pretiosa and Carnarvonia venosa. Mode of life, functional morphology. The preservation of Perspicaris dictynna is essentially similar to that of Marrella splendens (Whittington, 1971) and most other Burgess Shale arthropods, and suggests that it was benthic in habitat. The material of P. recondita, however, includes a higher proportion of fragmentary specimens, which may represent exuviae or the remains of dead individuals. The expanded furcal rami of this species (text -figs. 13, 14) are much larger than in P. dictynna, and strikingly similar to those of the Recent Nebaliopsis (c(. Rolfe 1969, p. 313, fig. 133, Ic) which Rolfe (1969, p. 308) considered ‘made sustained swimming possible’ and explained the wide distribution of this form. P. recondita may thus have been nectic; the few complete specimens could have been overtaken by a cloud of sediment while swimming near the sea bed. The large pedunculate eyes of Perspicaris (text-figs. 1, 2, 13, 14), borne on an apparently flexible projection of the cephalon, presumably ensured a wide field of view; the antennae appear to have been sensory rather than locomotory in function. The lack of evidence for the nature of the thoracic appendages prevents a satisfactory discussion of their functional morphology. Those of P. dictynna, however, appear to have included large, lamellate branches (they may have been biramous) which probably served in swimming, and may have induced an anteriorly directed current along the ventral surface of the trunk between the appendages which functioned in respiration and feeding. The apparent flexibility of the trunk of P. dictynna, together with the arrangement of the spines on the caudal furca (text-figs. 1, 2), suggest that it may have employed a grooming action similar to that described by Sanders (1963, p. 13) in Hutchinsoniella—'the head appendages are cleaned by jack-knifing or doubling the abdomen under the thorax and cephalon and drawing the abdomen posteriorly through the head and trunk appendages to its normal position’. The spines on the furcal rami of P. dictynna may have functioned like the combs on the last abdominal somite and telson of Hutcliinsoniella, which pass through the setae and spines of the appendages. Carapace reticulation in P. recondita. A reticulate pattern covers the greater part of the valves of USNM 20731 2 and 1 89244 (PI. 72, figs. 3, 4, 7) but has not been observed on the other specimens. The pattern is made up of irregular, rectilinear, polygonal areas (PI. 72, fig. 4), which range in maximum width from 0-1 to TO mm, but average from 0-3 to 0-5 mm. They are bounded on five, six, or seven sides by bands of darker material about 0-04 mm wide which are preserved in positive relief relative to the areas they enclose. The boundaries become ill-defined and less pronounced in relief towards the periphery of the reticulated area and appear to be obscured by an over- lying layer of cuticle. Rolfe (1962^, p. 4) described a similar reticulate pattern in BRIGGS: BURGESS SHALE ARTHROPODS 615 patchy areas on a few specimens of Prohoscicaris agnosta, also from the Burgess Shale, and noted its occurrence on specimens of Hurdia victoria, Tuzoia, and Caniarvonia from the same fauna. He eonsidered, however, that the cuticle ‘is too poorly preserved to ascertain whether this reticulation is sculptural or structural’. The Burgess Shale fossils are composed essentially of silicate minerals (personal communication S. Conway Morris) and do not include significant amounts of calcite. It is possible, however, that the carapace reticulation reflects the original prismatic structure of the cuticle of Perspicaris recondita which has been replaced during preservation. The variation in size and irregular shape of some of the polygonal areas on USNM 207312 (PI. 72, fig. 4), the smallest of which fall well within the range observed by Rolfe (1962<7, p. 45) on Ceratiocaris papilio from the Middle Silurian of Scotland, may be due to fusion of some of the prism boundaries during the replace- ment process. Some of the large, irregularly shaped polygons are traversed by faint traces which may represent original divisions. The concentration of fine reticulation along the longitudinal fold which accommodates the original convexity of flattened valves of Tuzoia (Resser 1929, pi. 1 ; pi. 2, fig. 1 ; pi. 3, figs. 1, 3) may be a reflection of some effect on the processes of preservation or diagenesis associated with the buckling of the carapace in this region. The specimens of P. recondita which show the reticulate pattern have been oxidized to a brownish-red colour, in contrast to the dark shiny material characteristic of the more finely preserved Burgess Shale fossils, and this ‘weathering’ process may have resulted in differential corrosion similar to that achieved by Rolfe (1962u) by controlled etching of Ceratiocaris. Visible evidence of the pattern may, on the other hand, be a function of the level through which the carapace has split. A study of the carapace of the abundant Canadaspis perfecta using the scanning electron microscope revealed no evidence of primary microstructures, and it is unlikely that finer detals of the cuticle of P. recondita are preserved. It is impossible to verify that the reticulate pattern on the carapace of P. recondita and other Burgess Shale arthropods is a reflection of the configuration of the organic matrix or prismatic structure of the cuticle but the evidence suggests that this may have been the case. Affinities and classification. The largest known specimen of P. dictynna is less than half the size of the smallest of P. recondita. The difference in the caudal furca of the two species, however, and the lack of reticulation on the carapace of all examples of P. dictynna, suggest that it is unlikely to represent a juvenile of P. recondita. The two may, however, be sexual dimorphs. Rolfe (1969, p. 305) recorded that ‘all Recent Leptostraca, except Nehaliopsis, show pronounced sexual dimorphism. . . . The carapace of the male is less deep than that of the female and the antennae are much larger. . . . The furca of the male Nebalia is also longer than that of the female.’ P. dictynna might therefore, by analogy with the Leptostraca, be interpreted as the male dimorph, and P. recondita as the female. Some characteristics of sexual dimorphism in the Leptostraca do not, however, bear out the analogy. Males occur much more rarely than females, whereas the two species of Perspicaris occur in equal numbers. The longer antennae of the male Leptostraea are usually modified ‘presumably to function as clasping organs’ (Rolfe 1969, p. 306). There is no evidence of such specialization in the known appendages of Perspicaris. Glaessner (1931) 616 PALAEONTOLOGY, VOLUME 20 TEXT-FIG. 23 TEXT-FIG. 25 EXPLANATION OF PLATE 72 Figs. 1-7. Perspkaris recondita gen. et sp. nov. 1-5. USNM 207312, carapace lateral, trunk parallel. 1, west, x6, after preparation to reveal appendage at antero-ventral margin of carapace; 2, north- west, X 3, showing posterior trunk somites and telson; 3, north, xL5; 4, north, microscope, x 12, showing reticulate pattern in central area of right valve; 5, north, microscope, x 12, showing border at postero-ventral margin of right valve; text-figs. 22, 23. 6, USNM 207313, parallel-oblique, north-east, X 3; text-fig. 24. 7, USNM 189244, vertical-oblique, north, x2, original of Simonetta and Delle Cave 1975, pi. 36, fig. la. Fig. 8. Tiizoia? parva (Walcott, 1912). USNM 57716, lateral-oblique, north, reflected, x 10, original of Walcott 1912, pi. 32, fig. 7, Simonetta and Delle Cave 1975, pi. 40, fig. 8; text-fig. 25. PLATE 72 BRIGGS, Perspicaris and Tuzoial from the Burgess Shale 618 PALAEONTOLOGY, VOLUME 20 considered that variation in the carapace of one species of Austriocaris was due to sexual dimorphism, but the phenomenon has not been recorded in other fossil phyllocarids. In the absence of specimens of the early instars of the two ‘forms’ of Perspicaris, which might show a convergence of morphology if they were dimorphs, they are described as separate species. The two specimens of P. recondita figured by Walcott (1912; USNM 57704, 57706) were referred by him to Hymenocaris ( = Canadaspis) peifecta. Perspicaris differs from Canadaspis in its larger eyes and antennae, and true caudal furca. The ‘furca’ of Canadaspis con?,\s,is of a pair of spinose ventral projections of the seventh abdominal somite. Perspicaris also differs from the type species of Hymenocaris, H. verrnicauda Salter, 1853, in the nature of the carapace and telson (cf. Rolfe 1969, p. 315, fig. 135). The morphology of Perspicaris indicates strong affinities with the Phyllocarida. The evidence suggests that the cephalon of P. recondita bore two pairs of antennae (PI. 71, fig. 3) and pedunculate eyes. The trunk of P. dictynna appears to have been divided into two tagmata, an appendage-bearing thorax of ten somites, and an abdomen of seven, in addition to the telson. The thoracic appendages are too poorly preserved to show any differentiation of their morphology, but it is possible that the anterior two pairs, although similar to those on successive somites, were cephalic (cf. Hutchinsoniella Sanders, 1963). Thus Perspicaris may have had the division of somites diagnostic of the phyllocarids (see Rolfe 1969). The genus is referred to the Phyllocarida as the lack of a rostral plate and abdominal appendages is not considered sufficient to warrant the erection of a new subclass. A fuller discussion of the nature of the Phyllocarida in the light of new information on C. peifecta is in preparation. Class MALACOSTRACA Latreille, 1806? Subclass PHYLLOCARIDA Packard, 1879? Order and Family uncertain Genus tuzoia Walcott, 1912? Type species. Tuzoia retifera'^ &\coll, 1912. Geological horizon. As for Perspicaris. Tiizoia? par va (Walcott, 1912) Plate 72, fig. 8; text-fig. 25 1912 1 Hymenocaris parva Walcott, pp. 153, 185, 224, pi. 32, fig. 7. 1925 1 Hymenocaris parva Walcott; Fedotov, pp. 386, 387. 1928 1 Hymenocaris parva Walcott; Henriksen, p. 14. 1929 Hymenocaris (?) parva Walcott; Gitrich, p. 41. 1934 1 Hymenocaris parva Walcott; Straelen and Schmitz, pp. 34, 199, 211, 232. 1975 Canadaspis sp.; Simonetta and Delle Cave pars, pi. 40, fig. 8. Holotype. USNM 57716, Plate 72, fig. 8, original of Walcott, 1912, pi. 32, fig. 7; Simonetta and Delle Cave 1975, pi. 40, fig. 8; by original designation. Other material unknown; Walcott (1912, p. 185) mentioned 'two specimens’ but the second was not figured and has not been identified. Locality and stratigraphical horizon. As for P. dictynna. The specimen bears the USNM locality number 35k, i.e. the ‘Phyllopod bed’ in the Walcott Quarry. BRIGGS: BURGESS SHALE ARTHROPODS 619 DESCRIPTION The specimen (PI, 72, fig. 8) is compacted in lateral-oblique aspect, the outline of the right valve apparently complete, the left folded beneath itself. The carapace appears to have been divided by a straight hinge line which was produced anteriorly into a long, straight spine or rostrum. The right valve is suboval in outline, tapering to a blunt anterior margin, and expanding postero-ventrally. The posterior margin is inclined to the hinge line at about 120'’, creating a pronounced posterior embayment of the carapace. A break of slope parallel to the anterior margin may represent a fold accommodating the original convexity and suggests that this margin, which is inclined posteriorly at an angle of about 80° to the hinge, may have been foreshortened by compaction. The valve bore at least five elongate spines ventrally, directed posteriorly at an angle of 50°-70° to the margin. The spinose features which project obliquely from beneath the posterior extremity of the left valve may also represent these spines. The dorsally directed ‘spine’ posterior of the right valve is preserved above the level of the carapace, and does not appear to be part of the specimen. The carapace appears to have been smooth apart from an indication of a narrow border preserved along the ventral margin of the right valve; no satisfactory evidence of a muscle scar has been observed. The small feature bearing a pair of long slender spines which projects ventrally from beneath the posterior margin of the right valve is considered to represent the telson and caudal furca, but no details of the morphology are preserved. The length of the right valve parallel to the hinge line, excluding the anterior spine, is 4-2 mm. The height normal to the hinge is 2-7 mm. DISCUSSION Previous descriptions. Walcott (1912, p. 185) oflfered a different interpretation of USNM 57716. He considered that the left valve was the abdomen which is ‘pushed over on to the carapace’ and that the furcal rami were ‘the antennae’ which ‘project from the left side’. His figure (1912, pi. 32, fig. 7) appears to have been retouehed to give a segmented appearance to the latter. Walcott interpreted the spines borne on the ventral margin of the right valve as appendages (p. 224). There is no evidence that the spines on the margin of the valve project from beneath it, as would be the case if they were appendages; they appear to be continuous with the border of the carapace. An interpretation of the relatively complete valve as the right-hand member of a pair is consistent with an anteriorly tapering outline, which occurs in many bivalved arthropods (e.g. Perspicaris, Canadaspis). The telson and caudal furca are thus in a position which they might be expected to occupy in a specimen preserved in the postulated orientation to the bedding. There is no evidence to support Walcott’s contention that the folded left valve is part of the trunk. Affinities and classification. Walcott (1912) tentatively referred USNM 57716 to Hymenocaris Salter, 1853 to which he also assigned specimens now described as P. recondita and C. perfecta. Subsequent authors (Fedotov 1925; Henriksen 1928; Giirich 1929; Straelen and Schmitz 1934) reiterated, but did not discuss, Walcott’s doubt, which is clearly vindieated by the spinose margin of the earapace, a feature absent from Hymenocaris, Canadaspis, and Perspicaris. Simonetta and Delle Cave (1975), however, considered the specimen to be a juvenile of Canadaspis sp. indet. A spinose carapace occurs in the large bivalved genus Tuzoia Walcott, 1912, which is also present in the ‘Phyllopod bed’. The generic assignment of H. ? parva Walcott, 1912, remains equivocal. It is referred with a query to Tuzoia, to which it bears the greatest similarity, as there is insufficient evidence to warrant the erection of a new genus. 620 PALAEONTOLOGY, VOLUME 20 The valves of USNM 57716 appear to have tapered anteriorly, whereas Rolfe (1969, p. 327, fig. 152, no. 6) reconstructed that of Tiizoia expanding slightly in this direction. A comparison of Resser’s two figured specimens of T. burgessensis (1929, pi. 2, fig. 1 ; pi. 3, fig. 1) suggests, however, that the valve may have tapered anteriorly, and that the outline of the specimen upon which Rolfe’s reconstruction is based (USNM 80477, Resser 1929, pi. 2, fig. 1) has been altered by compaction. There is no evidence that the carapace of T. ? parva was reticulate, as is usually the case in Tuzoia, but this may be a feature of preservation; reticulation is not present, for example, on all specimens of P. recondita. T. ? parva also lacks the prominent ridge characteristic of the valves of Tuzoia (see Rolfc 1969, p. 328) which Resser (1929) referred to as a keel, but this feature varies in position (cf. Resser 1929, pi. 1, fig. 1 with pi. 1, fig. 2; pi. 2, fig. 1 with pi. 3, fig. 1, for example) and is probably due to compaction of the original convexity, which may have reached a maximum along the mid-line of the valve parallel to the hinge. Tuzoia bore spines on the posterior margin of the valves, and the posterior extremity of the hinge line was produced into a spine; these features appear to have been absent on T. ? parva. T. ? parva may have been a juvenile or larval form of a larger bivalved arthropod. Juveniles of C. perfecta (with carapaces about 10 mm in length) do not appear to differ from the adults, but this may not have been the case in T. ? parva. The specimens of Tuzoia found at the Walcott Quarry vary from about 40 to 120 mm in length; smaller valves are unknown. Several authors (Henriksen 1928; Resser 1929) sug- gested that Aiwmalocaris Whiteaves, 1892 may have been the trunk of Tuzoia, but this genus is reinterpreted as the appendage of a large arthropod ; the body of Tuzoia remains unknown. The bivalved carapace and apparently unsegmented caudal furca of T. ? parva support a tentative assignment to the subclass Phyllocarida. Acknowledgements. I am indebted to H. B. Whittington, W. D. I. Rolfe, and C. P. Hughes for discussion and criticism of previous drafts. R. E. Grant and F. J. Collier (USNM) provided liberal access to the Walcott Collection. D. F. Bursill assisted with some aspects of the photography. The work was financed by a Research Fellowship held at Sidney Sussex College, Cambridge, and NERC grant GR3/285 awarded to H. B. Whittington. REFERENCES FEDOTOV, D. 1925. On the relations between the Crustacea, Trilobita, Merostomata and Arachnida. Izv. ross Akad. Nauk, 1924, 383-408. FRITZ, w. H. 1971. Geological setting of the Burgess Shale. Proc. North Am. Paleont. Conv. 1969, I, 1155- 1170. Lawrence, Kansas. GLAESSNER, M. F. 1931. Fine Crustaceenfauna aus den Lunzer Schichten Niederosterreichs. J. geol. Bimdesanst . Wien, 81, 467-486. GURICH, G. 1929. Silesicaris von Leipe und die Phyllokariden uberhaupt. Mitt. Miner.-geol. Stinst. Hamb. 11, 21-90. HENRIKSEN, K. L. 1928. Critical notes upon some Cambrian arthropods described by Charles D. Walcott. Vidensk. Meddr dansk naturh. Foren. 86, 1-20. LATREILLE, p. A. 1806. Histoire naturelle, generale et particuliere, des Crustaces et des Insectes. In L. de BUFFON. Histoire naturelle, 50, 408 pp., Paris. MOORE, R. c. and mccormick, l. 1969. General features of Crustacea. In r. c. moore (ed.). Treatise on Invertebrate Paleontology, Part R, 57-120. Geol. Soc. Am. and Univ. of Kansas Press. PACKARD, A. s. 1879. The Nebaliad Crustacea as types of a new order. Am. Nat. 13, 128. BRIGGS: BURGESS SHALE ARTHROPODS 621 RESSER, c. E. 1929. New Lower and Middle Cambrian Crustacea. Proc. US. natn. Mus. 76, art. 9, 118. ROLFE, w. D. I. 1962fl. The cuticle of some Middle Silurian ceratiocaridid Crustacea from Scotland. Palaeontology, 5, 30-51. 1962^. Two new arthropod carapaces from the Burgess Shale (Middle Cambrian) of Canada. Breviora, 160, 9 pp. 1969. Phyllocarida. In R. c. moore (ed.). Treatise on Invertebrate Paleontology, Part R, 296-331. Geol. Soc. Am. and Univ. of Kansas Press. SALTER, J. w. 1853. On the lowest fossiliferous beds of North Wales. Rep. Br. Ass. Advmt Sci. (1852), Trans, of the sections, 56-58. SANDERS, H. L. 1963. The Cephalocarida— functional morphology, larval development, comparative external anatomy. Mem. Conn. Acad. Arts Sci. 15, 80 pp. SIMONETTA, A. M. and DELLE CAVE, L. 1975. The Cambrian non trilobite arthropods from the Burgess Shale of British Columbia. A study of their comparative morphology, taxonomy and evolutionary significance. Palaeontogr. ital. 69 (n.s. 39), 37 pp. ST0RMER, L. 1944. On the relationships and phylogeny of fossil and Recent Arachnomorpha. Skr. norske Vidensk-Akad. Mat.-naturv. Kl. 5, 158 pp. STRAELEN, V. VAN, and SCHMITZ, G. 1934. Crustacea Phyllocarida ( = Archaeostraca). In w. quenstedt (ed.). Fossilium Catalogus I: Animalia, 64, 246 pp. Berlin. WALCOTT, c. D. 1912. Middle Cambrian Branchiopoda, Malacostraca, Trilobita, and Merostomata. Smithson, misc. Colins, 57, 145-228. WHiTEAVES, J. F. 1892. Description of a new genus and species of phyllocarid crustacean from the Middle Cambrian of Mount Stephen, British Columbia. Can. Rec. Sci. 5, 205-208. WHITTINGTON, H. B. 1971. The Burgess Shale: History of research and preservation of fossils. Proc. North Am. Paleont. Conv. 1969, I, 1170-1201. Lawrence, Kansas. 1974. Yohoia Walcott and Plenocaris n. gen., arthropods from the Burgess Shale, Middle Cambrian, British Columbia. Bull. geol. Siirv. Can. 231, 27 pp. Original typescript submitted 5 April 1976 Revised typescript submitted 20 June 1976 D. E. G. BRIGGS Sedgwick Museum Cambridge CB2 3EQ KV. w ifij- g ■ •*•■ - :4V=" •V i. ii*. ■ -*>■': A NEW METAZOAN FROM THE CAMBRIAN BURGESS SHALE OF BRITISH COLUMBIA by SIMON CONWAY MORRIS Abstract, Hcdlucigenia sparsci (Walcott) gen. nov. from the Burgess Shale (Middle Cambrian) is redescribed. It is characterized by an elongate trunk supported by seven pairs of long spines. The trunk also bears seven tentacles with bifid tips and a group of short posterior tentacles. A globular head lacks appendages. Despite certain similarities to the polychaetes H. sparsa is not an annelid. Its systematic position, as well as its mode of life, remain problematical. C. D. Walcott, who discovered the Burgess Shale (Middle Cambrian) and described much of its fauna and flora, placed seven species in the genus Canadia Walcott, 1911 (Polychaeta: Annelida). They are C. spinosa (the type species), C. setigera, C. sparsa, C. duhia, C. urcgu/ur A (Walcott, 1911), C . grandis,‘din6. C. simplex (Walcott, 1931). Recent research has shown that with the exeeption of the type species none of these worms can be placed in Canadia. New genera have been proposed for them, with the exception of C. irregularis and C. grandis which are junior synonyms of C. spinosa. Furthermore, C. sparsa and C. simplex cannot be accommodated in the polyehaetes (Conway Morris 1976/?). C. sparsa was very briefly described by Walcott (1911), but it was not illustrated until 1931 (Walcott, pi. 6, flg. 3). Although the illustration is poor, it clearly does not tally with Walcott’s earlier account where he noted ‘two strong setae on each very short parapodia [5/c]’. Prominent pairs of ‘setae’ are visible along one side of the animal, but the struetures along the other side are clearly different. The purpose of this communieation is to illustrate the bizarre morphology of this animal which precludes any relationship with Canadia. In addition to the holotype, consisting of part and counterpart, thirty other specimens have been found during three searches through the collections of Burgess Shale fossils in the National Museum of Natural History (formerly the U.S. National Museum (USNM)), Washington, D.C. One specimen has been located in the Museum of Comparative Zoology (MCZ), Harvard. Three specimens were eolleeted by the Geological Survey of Canada (GSC) team led by Dr. J. Aitken in 1966 with the co-operation of the authorities of the Yoho National Park and the Parks Canada, Department of Indian Affairs and Northern Affairs, Ottawa (see Whittington 1971u). A brief review of the excavation of the Burgess Shale and its stratigraphic position were given by Conway Morris (1976a). All the USNM specimens are labelled 35k, whieh is the loeality number for the Phyllopod bed exposed in the Burgess quarry (Walcott 1912a). Walcott did not give any details of the vertical distribution of this species. Two of the GSC specimens are from 88-9-10T6 cm (2 ft 11 in. -3 ft 4 in.), whilst the third is from 88-9-91 -4 cm (2 ft 11 in. -3 ft) above the base of the quarry. The total known range is, therefore, 12-7 cm (5 in.). [Palaeontology, Vol. 20, Part 3, 1977, pp. 623-640, pis. 73-76.] 624 PALAEONTOLOGY, VOLUME 20 SYSTEMATIC PALAEONTOLOGY Phylum UNCERTAIN Family hallucigeniidae fam. nov. Diagnosis. Seven-fold repetition of the dorsal tentacles and pairs of ventral spines that arise from the trunk, which also bears a globular head. Genus hallucigenia gen. nov. Type and only known species. Hallucigenia sparsa (Walcott, 1911) gen. nov. Derivation of name. Hallucigenia refers to the bizarre and dream-like appearance of the animal. Diagnosis. Elongate {c. 2 cm) bilaterally symmetrical metazoan. Body consists of globular head without appendages and long narrow trunk. Trunk supported by seven pairs of ventro-lateral spines, and bears medially seven dorsal tentacles with bifid tips. Each tentacle opposed to a pair of spines, except for anteriormost tentacle. Posterior to seventh tentacle is a cluster of shorter dorsal tentacles. Posterior trunk bent upwards and forwards. Hallucigenia sparsa (Walcott, 1911) gen. nov. Plates 73-76; text-figs. 1, 3, 4 1911 Canadia sparsa Walcott, p. 119. 1912 Canadia sparsa Walcott, p. 190. 1931 Canadia sparsa Walcott, p. 5, pi. 6, fig. 3. Diagnosis. As for the genus. Holotype. USNM 83935 (Walcott 1931, pi. 6, fig. 3) from the Stephen Formation (Middle Cambrian), Burgess Shale Member (Pagetia bootes faunule of the Bathyuriscus-Elrathina Zone; Fritz 1971). The Phyllopod bed (2-31 m) lies within division h of the Burgess Shale (Walcott 191 2fi), and is exposed in the Burgess quarry which is 4-8 km north of Field, southern British Columbia. Other material. USNM 188602, 193996 (two specimens), 194137, 194890 (three specimens), 194906, 196348, 198584, 198658-198662, 198663 (two specimens) 198664-198666, 198777, 199699 (counterpart is 199732), 200272, 201290, 203135, and five un-numbered specimens. GSC 8231 (located by D. E. G. Briggs), 45332, 45333, and an un-numbered specimen. MCZ 1084. A note on the photography and interpretation of specimens. All the specimens have been photographed in ultra-violet light from a directional lamp using Panatomic-X film. The majority were photographed in high-angle light. The lamp was inclined to the horizontal specimen at about 60°, the specimen was then tilted through about 10° towards the lamp until maximum reflectivity, as observed down the focusing tube, was obtained. Unless stated otherwise the plate-flgures were photographed in high-angle light. A few specimens (PI. 73, fig. 2; PI. 74, figs. 1, 3, 6; PI. 76, fig. 4) were photographed in low-angle light. The inclination of the lamp was about 30° and the specimen was placed as near horizontal as possible. Eocusing was undertaken in ordinary light. CONWAY MORRIS: CAMBRIAN METAZOAN 625 Camera-lucida drawings are placed beside Plate 73, figs. 1-3; Plate 74, figs. 5, 6; Plate 76, figs. 1, 2, as a guide to their interpretation. Preservation. The specimens are preserved as very thin films. The spines and tips of the tentacles are preserved as reflective films, whilst the rest of the body is usually less reflectively preserved. The composition of the film in a specimen of the priapulid Ottoia prolifica was determined by R. A. Chappell (National Physical Laboratory, Teddington) using Auger spectroscopy to consist of calcium aluminosilicates, although reflective areas contain additional magnesium. It is apparent that the great majority of Burgess Shale fossils are composed of this silicate film. The dia- genetic processes that led to the formation of this film are, however, obscure. With two exceptions the specimens are comparatively poorly preserved and are often associated with considerable amounts of algae (PI. 75, figs. 3, 6), as well as other fossils such as the priapulid O. prolifica, the trilobitoid Marrella splendens and other arthropods. MCZ 1084 is exceptional in having at least eighteen specimens of H. sparsa associated with a specimen of an undescribed worm (PI. 76, figs. 1,2; text-fig. 4). Morphology. Text-fig. 2a shows a reconstruction of the animal in life. The basic form of the animal was a long narrow trunk supported by seven pairs of ventro-lateral spines. One end of the trunk carried a swollen mass which presumably was the head. There was a single median row of dorsal tentacles, and more posteriorly there were about six short tentacles. Dorsal and ventral surfaces are identified on the assumption that the spines were embedded in the bottom sediments. The bilateral symmetry of the animal was defined by the pairs of ventro-lateral spines. The length of the animals varied between about 0-5 and 3-0 cm, the average being about 1-8 cm. All, save one, of the specimens are preserved laterally, so that the plane of bilateral symmetry is more or less parallel to the bedding plane. No dorsally or ventrally flattened specimens have been recognized. The longitudinal axis of one GSC specimen (PI. 76, figs. 3-5) is, however, steeply inclined to the bedding plane. Burial in a mud- flow seems to be the most probable explanation for such steeply and vertically orientated specimens (Whittington 1971fl) and, as is the case with M. splendens, such specimens are far outnumbered by those with the longitudinal axes parallel to the bedding plane. The head is preserved in two specimens. Its poor definition may be due partly to an enveloping dark stain similar to that associated with M. splendens (Whittington 1971a, b). Whittington interpreted the dark stain as body contents that were squeezed out by the pressure of superincumbent strata. The stain has been reinterpreted as the product of body contents seeping out of the corpse during decay, because the time taken to deposit sufficient overburden would have far outweighed the time taken for a specimen to decay (Conway Morris 1 916b). In the Burgess Shale the stain is restricted to a few species which presumably had a peculiar body composition in common. The stain often occurs around the anterior and posterior ends suggesting that the mouth and anus acted as points of egress. More extensive stains that flank the body probably represent rupturing of the body wall. The extent of the stain is, therefore, probably directly proportional to the degree of decay. A similar feature has been noted in both fossil and recent conditions. Bardack (1974) reported a light-coloured 626 PALAEONTOLOGY, VOLUME 20 5 mm TEXT-FIG. 1. Camera-liicida drawing of USNM 83935 (holotype), combining features of the part and counterpart. Lines with hachures indicate definite breaks in slope, the hachures being directed downslope. Stippled areas represent rock. Hd., Head; Ms. Ah., Muscle attachment area; Pst. Tr., Posterior trunk; S., Spine; St. Tt., Short tentacle; Tr. Tb., Trunk tube; Tt., Tentacle. Stain around the anus of partially decayed fish from the Pennsylvanian of Illinois. In modern subaerial conditions Schafer (1972, fig. 17) noted that in rotting seals oily liquids are discharged from the mouth and anus, and later from the abdominal area. The head was probably globular and there were no appendages or mouth parts (PI. 73, fig. 3; PI. 74, figs. 1,6; text-figs. 1, 3). Apart from the trunk tube (see below) entering the head (PI. 74, figs. 5, 6) and an indistinct area of greater reflectivity in USNM 83935 (PI. 73, fig. 3), no internal detail is discernible. The smooth, narrow trunk extended horizontally posterior to the head. The plane of splitting appears to have cut across the steeply inclined specimen GSC 45332 so EXPLANATION OF PLATE 73 Figs. 1-5. Hallucigenia sparsa (Walcott) gen. nov. USNM 83935 (holotype). 1, part, light from south-west, x3-7. 2, part, low-angle light from north-east, x3-7. 3, counterpart, light from north-west, X 5-2. 4, part, enlargement of posterior trunk with short tentacles, light from south-west, X 6. 5, counter- part, enlargement of tentacle with bifid tip, light from east, X 16. PLATE 73 CONWAY MORRIS, Cambrian metazoan An. TEXT-FIG. 2. Anatomy of Halhicigenia sparsa (Walcott) gen. nov. a, reconstruction of appearance in antero- lateral view. B, hypothetical arrangement of muscles running from the proximal end of the spine to the horseshoe-shaped attachment area on the trunk, c, hypothetical transverse section of the trunk and a tentacle. An., Anus; Ms., Muscle; Tr., Trunk. See text-fig. 1 for other abbreviations. CONWAY MORRIS. CAMBRIAN METAZOAN 629 producing a transverse section of the trunk (PI. 76, figs. 3, 4). The cross-section of the trunk was more or less circular. In this specimen the trunk is traversed by a dorso- ventral strand that may represent the remains of the trunk tube or some vertical septum (PI. 76, fig. 3). The trunk carried seven median tentacles (Tj-T7) and, more posteriorly, six short tentacles on its dorsal surface. Seven pairs of ventro-lateral spines (Sj-Svii) projected into the sediment. Each tentacle was opposite a pair of spines, except for the anteriormost one (Tj) which was unopposed. Thus, the most posterior pair of spines (Svn) was also unopposed (PI. 73, figs. 1, 2, 4; PI. 74, figs. 5, 6; text-figs. 1, 3). The spacing of the tentacles is more or less constant, with the exception of Tj which is separated from T2 by a lesser distance. The tentacles decreased slightly in length anteriorly (PI. 73, fig. 3; text-fig. 1). The length of the tentacles varies from 2- 7 mm (USNM 198658, total length 1-6 cm) to 5-5 mm (USNM 83935, total length 3- 0 cm). Typically the tentacles are preserved running at right angles to the trunk, with the distal part bent forwards (PI. 73, figs. 1-3; text-fig. 1). Tentacles Tg and T7 of USNM 198658 are, however, flexed backwards (PI. 74, figs. 5, 6; text-fig. 3), whilst the tentacle bases of USNM 198659 (PI. 75, fig. 8) appear to be bent ventrally. The tips of the tentacles were bifurcate, with the superior fork being slightly longer than the other (PI. 73, fig. 5; PI. 74, fig. 6; text-fig. 3). The trunk contains a longitudinal reflective band, which is interpreted here as an internal tube (PL 73, figs. 1, 3; PI. 74, fig. 5; text-figs. 1, 3). This trunk tube ran from the head to the posterior end of the trunk, and may have been the gut. Continuations of the tentacles can be traced into the trunk and they appear to join the trunk tube (PI. 73, fig. 3; PI. 74, fig. 2; text-figs. 1, 2c). It is almost certain that the tentacles were hollow, but as is discussed below it is uncertain whether the lumen was in direct contact with the exterior via the bifid end. Posterior to tentacle T7 there was a dorsal cluster of smooth tentacles that were shorter than tentacles T1-T7 (T5-2-0 mm long) (PI. 73, figs. 1, 2, 4; text-fig. 1). Their tips appear to have been complete and not bifid. The most anterior of the short tentacles is separated from tentacle T7 by the same spacing as separates the tentacles from each other. In USNM 198658 six short tentacles are preserved on two different bedding planes (PI. 74, figs. 4-6; text-fig. 3). This observation suggests that they formed three pairs, with the tentacles of each pair separated by the plane of bilateral symmetry. Upon burial in one of the mudflows that went to form the Phyllopod bed (Piper 1972), the two sets of tentacles were separated by sediment in the same manner as the appendages of M. splendens (Whittington, 1971a, h). In USNM 83935 the posteriormost of the three short tentacles preserved can be traced entering the trunk and apparently joining the trunk tube (PI. 73, fig. 4; text-fig. 1). It is probable that this feature was common to all the short tentacles. Posterior to the short tentacles the trunk decreased in diameter by about a half (PI. 73, fig. 2) This narrower length was smooth and lacked appendages. Characteristically it was bent upwards and then forwards, so that it overlay the posterior tentacles T^7. (PI. 73, figs. 1, 2; PI. 74, figs. 5, 6; text-figs. 1, 3). The swollen end of USNM 198584 (PL 75, fig. 1) may be original, but it could owe its appearance to decay reducing the rest of the posterior trunk to a thin strand. There were seven pairs of ventro-lateral spines. The spacing between the pairs was 630 PALAEONTOLOGY, VOLUME 20 fairly constant, although S, was separated from Sj, by a greater distance. The total of seven pairs is invariable, even in the smallest known specimen (5 mm long). Each spine was straight and tapered to a fine point (PI. 73, figs. 1, 2; PI. 74, figs. 5, 6; PI. 75, figs. 1-8; text-figs. 1, 3). They varied in length from 0-8 mm (GSC 45333, total length 5-0 mm) to 10-0 mm (USNM 83935, total length 3-0 cm), and the average was about 4-0 mm. In similar-sized specimens each spine has about the same proximal diameter (0-7 mm) whether preserved laterally (PI. 73, figs. 1, 2; text-fig. 1), or vertically (PI. 76, figs. 3, 4). This suggests that they had a circular cross-section. Well- preserved spines have about ten longitudinal lines each, which probably represent original ribbing (PI. 73, fig. 4; PI. 74, fig. 3). The blunt square ends of the spines were TEXT-FIG. 3. Camera-lucida drawing of USNM 198658. See text-fig. 1 for explanatory notes and abbreviations. EXPLANATION OF PLATE 74 Figs. 1-6. Hallucigenia sparsa (Walcott) gen. nov. USNM 83935 (holotype), figs. 1-3; USNM 198658, figs. 4-6. 1, counterpart, enlargement of anterior trunk and head, low-angle light from south-east, X 7- 1 . 2, counterpart, enlargement of tentacle entering trunk and joining trunk tube, light from north, X 1 1 . 3, part, trunk with horseshoe-shaped muscle attachment areas, low-angle light from north- west, X 5-3. 4, enlargement of posterior trunk with short tentacles, light from north, x 16. 5, complete specimen, light from north-east, x7-6. 6, complete specimen, low-angle light from north, x7-6. PLATE 74 CONWAY MORRIS, Cambrian metazoan 632 PALAEONTOLOGY, VOLUME 20 inserted within the trunk. Furthermore, the trunk itself extended as a sheath along a short distance of each spine (PL 73, fig. 2; PI. 76, figs. 3, 4; text-fig. 1). The spines of each pair did not articulate against each other, and they were probably separated by the trunk tube (PI. 76, fig. 3; text-fig. 2c). They formed an interspinal angle of about 70°. In laterally preserved specimens the angle between the spines of each pair can vary; in USNM 198665 from 0° (Sy,, Sy„) to 20° (S,) (PI. 75, fig. 3). This suggests that the spines could move independently. The orientation of the specimen may, however, also determine the angle of separation, especially in cases where the angle increases by a regular amount along the length of the animal. This may be due to the specimen lying at a progressively steeper angle to the bedding plane along its length (e.g. PI. 75, figs. 5, 7). The proximal end of each spine was surrounded by a horseshoe-shaped line that opened ventrally (PI. 73, figs. 1, 2; PI. 74, fig. 3; text-fig. 1). This line may represent a strengthened part of the body wall which acted as the insertion point for muscles that ran to the proximal end of the spine. The proximal end of the spine is sometimes raised with respect to the rest of the spine and the muscles were probably inserted at this point. The muscles may have been in the form of a fan that radiated from the spine, but they were more probably grouped into several discrete bundles (text- fig. 2b). Additional muscles may have run from the horseshoe-shaped line to more distal parts of the embedded spine, while other muscles could have been inserted within the area defined by the horseshoe-shaped line. Contraction of the different muscle bundles would have moved the spine. A parallel exists with the acicular muscles of polychaetes. Aciculae are stout spines that support and move the para- podia, particularly during the power stroke of walking (Mettam 1967). They project to, or just beyond, the distal end of the parapodia and also into the body cavity. Typically there is one aciculum in each ramus of a parapodium, although multiples are known. In Hermodice caninculata, however, the aciculae are replaced function- ally by the setal sacs (Marsden, 1966). Protractor and generally weaker retractor muscles inserted on the base of the aciculum, and neurosetal sac of H. caninculata, radiate outwards and are attached to the trunk and parapodial walls. Information on acicular muscles and their points of insertion is available in Clark and Clark (1960), Clark (1964), Marsden (1966), Manton (1967), Mettam (1967, 1971), and Lawry (1971). In Nereis diversicolor the insertion line on the posterior parapodial wall of most of the acicular protractors of the neuropodium forms an incomplete arc (Mettam 1967), and thus is not dissimilar to the horseshoe-shaped insertion line of EXPLANATION OF PLATE 75 Figs. 1-8. Hallucigenki sparsa (Walcott) gen. nov. All partially decayed specimens. Note algae associated with specimens in figs. 2-4, 6, 7. 1, USNM 198584, light from south, x 12. 2, USNM 198662, light from south, x3-6. 3, USNM 198665, light from north-west, X 5-8. 4, USNM 198660, light from north, X 3-6. 5, USNM 198664, light from south-east, x 4-6. 6, USNM 198663, light from north, x 2-4. 7, USNM 198661, light from south-west, x 3-2. 8, USNM 198659, light from south, x4-2. PLATE 75 CONWAY MORRIS, Cambrian metazoan 634 PALAEONTOLOGY, VOLUME 20 Hallucigema sparsa. In N. diversicolor, however, the arc is not raised on the wall of the parapodium, nor is it complete as in H. sparsa. The polychaete parapodium possesses other muscles that are also used in its movement (Mettam 1967, 1971). No analogous muscles have been identified in H. sparsa. DISCUSSION Mode of life. As no animal like H. sparsa is known today its mode of life is rather problematical. It must have been epifaunal, as it is impossible to imagine it either swimming or burrowing. The spines appear to be suitable for supporting the animal on a muddy bottom (text-fig. 2a). The large interspinal angle of each pair would have given a high degree of stability. The varying position of the independent spines with respect to each other, and the postulated existence of muscles indicates that the spines could move and were not rigidly fixed. The movement of the spines may have been similar to the locomotory cycle of walking polychaetes, and the notopodial ‘poling’ movements with which tubicolous polychaetes such as Sabella progresses along the tube (Clark 1964, fig. 74). In addition, the section of the trunk that extended around the proximal spine may have been extended by coelomic fluid during the power stroke, as occurs in the neuropodia of Hermodice carunculata (Marsden, 1966). If this was the case it is probable that like the polychaetes the trunk of Hallucigenia sparsa was subdivided by transverse septa to maintain turgor pressure. No evidence of septa has, however, been preserved. Thus the creature could have moved over the mud, with the spines presumably lifted clear of the sediment by the action of their muscles during the recovery stroke. Some specimens are curved so that the tentacles lie on the concave side (PI. 74, figs. 5, 6; text-fig. 3). This configuration, which may have arisen by contraction of longitudinal muscles in the dorsal trunk, could have helped to lift the spines clear. Marsden (1966) noted that Hermodice carunculata often raises its anterior end, apparently to test the environment. It is possible that Halluci- genia sparsa had the same behavioural pattern. Locomotion would, however, have been far more effective if the pointed tips of the spines could have pushed against a resistant substrate. This is because the ends would have tended otherwise to be pushed into the sediment during the power stroke, without giving effective leverage. For this reason one may speculate that H. sparsa could have lived on a hard bottom. The Phyllopod bed was deposited immediately adjacent to a carbonate bank (Fritz 1971), and it is possible that H. sparsa lived on the bank itself. However, unless the mudflows that went to form the Phyllopod bed swept over the basal apron of the bank, it is diflicult to see how the specimens could be swept away. H. sparsa probably did not progress rapidly over rocks or mud, and much of its time may have been spent stationary. The movement of H. sparsa may not, however, have been as awkward as it intuitively appears. Mettam (1971), for example, reported that during locomotion Aphrodite (Polychaeta) can support its entire body on about six neuro- podial bundles of setae at any one time. In addition, some echinoids can support the test above the sediment on long spines. In the reeent echinoid Plesiodiadema indicum the adoral spines have terminal thickenings to prevent sinking (Mortensen 1940). Specimens of Pseudodiadema sp. from the Ringstead Waxy Clay (Upper Oxfordian) of Dorset have, however, long thin spines without terminal thickenings, CONWAY MORRIS: CAMBRIAN METAZOAN 635 which suggests a relatively firm clay surface (Dr. M. Brookfield pers. comm.). It might be postulated that the sediments of the pre-slide environment of the Burgess Shale showed a similar resistance to penetration, perhaps due to early hardening. MCZ 1084 has at least eighteen specimens of H. sparsa associated with a new undescribed worm (PL 76, figs. 1,2; text-fig. 4). This association cannot be by chance because practically all the specimens lie on the worm and not beyond it. The variation in size and lack of coherent arrangement demonstrates that the specimens did not form a colony. It is proposed that they were attracted from the surrounding area and congregated to feed on the corpse. The spines could have been embedded in the decaying flesh. H. sparsa was, therefore, probably a scavenger. In modern deep-sea communities similar occurrences have been observed where various crustaeea, ophiuroids, and later fish come together to scavenge bait lowered from ships (Isaacs and Schwartzlose 1975). The slow-walking polychaete Hermodice canmcidata, to which comparison with Hallucigenia sparsa was made above, ‘is a scavenger or else feeds on sessile alcyonarians and zooantharians . . . and does not prey on active animals’ (Marsden 1966, p. 275). It is possible that H. sparsa included sessile creatures such as sponges in its diet. The tentacles with their bifid tips appear to have been suited for grasping food. Evidence is presented below suggesting that the bifid tips were more cuticularized and resistant to decay, which supports the notion that they were used for biting. Food may have been taken from the water, or if the tentacles were bent ventrally from either prey or the sediment. For a tentacle to reach the surface of the sediment or corpse on which it was feeding, assuming that it was not extensible, two-thirds of the ventral spine would have to be embedded. Despite the pointed spines, the animal could not have sunk to this depth under its own weight. This is because the sea-water would have almost counterbalanced the weight of the animal by buoyancy, and the residual weight would not have been sufficient to allow the animal to embed itself. Thus penetration of the sediment by the spines would have required active muscular effort. It is uncertain how the food was ingested. The food may have been passed forward to the head, but the possibility that the bifid tip of each tentacle contained an opening that led directly to the trunk tube, which presumably was the gut, cannot be dismissed. Either hypothesis presents difficulties. If the mouth was at the anterior, it is uncertain how the food was passed forward by the tentacles. One possibility is that a longitudinal ciliated gutter conveyed food to the mouth. It seems highly unlikely that food was passed forward from tentacle to tentacle. Alternatively, if the bifid openings of the tentacles aeted as individual mouths, only the comparatively short length of gut posterior to tentacle T7 would have been available for effeetive digestion. The function of the short tentacles is unknown. Their posterior location renders their use as food-sorters or sensory organs improbable. It has been suggested to the author that the anterior and posterior ends of the animal should be reversed. Thus, it is conceivable that the short tentaeles sorted food, and the curved posterior trunk bent down to take the food. Definitive evidence is lacking. The author prefers to regard the tentacles as bending forwards, and the swollen anterior end as the head rather than the simple posterior trunk. Figs. 1-5. Hallucigenia sparsa (Walcott) gen. nov. MCZ 1084, figs. 1-2; GSC 45332, figs. 3-5. 1, part, specimens of H. sparsa distributed over an undescribed worm, light from north-east, x 3. 2, counter- part of fig. 1, light from north-west, x 3. 3, part, specimen steeply orientated with respect to the bedding plane, light from west, x 6-4. 4, part, low-angle light from east, x 6-4, 5, counterpart of figs. 3-4, light from east, x 6-4. PLATE 76 CONWAY MORRIS, Cambrian metazoan 638 PALAEONTOLOGY, VOLUME 20 There is no evidence that the specimens of H. sparsa are detached fragments of a colonial organism. The vast majority of Burgess Shale fossils are complete, and a special explanation must be invoked for species such as the arthropod Anomalocaris gigantea Walcott, 1912a which is only found as isolated appendages (D. E. G. Briggs pers. comm.). Preservation and decay. The poor preservation of the majority of specimens is attri- buted to decay, which was stopped by the onset of fossilization. The spines, however, are always well preserved and show no signs of deterioration. This suggests that they were made of a tough resistant material, but their exact composition is unknown. The trunk is usually poorly preserved (PI. 75, figs. 3-5, 7, 8), and sometimes almost completely absent (PI. 75, figs. 1, 2, 6). The head and tentacles are well preserved only in two specimens (PI. 73, figs. 1-5; PI. 74, figs. 1, 2, 4-6; text-figs. 1, 3), although in some specimens the basal stumps of some of the tentacles are present (PI. 75, fig. 7). The bifid end of each tentacle is, moreover, preserved as a more reflective film than the remainder of the tentacle (PI. 73, figs. 3, 5). The bifid ends appear to be more resistant to decay so that they apparently persist after the disappearance of the rest of the tentacle (PI. 75, figs. 2, 4). The body wall of the head and tentacles was probably thinner than that of the trunk. It is concluded that the decreasing order of resistance to decay was: spines, trunk, tentacles, and head. Systematic position. H. sparsa cannot readily be compared to any living or fossil animal. As noted above, Walcott’s (1911) placement of this worm in the genus Canadia (Polychaeta) cannot be upheld. There are virtually no similarities between the type species, C. spinosa Walcott, and this animal. The new genus Hallucigenia has, therefore, been proposed. Walcott (1911) assigned the species to the polychaetes on the supposition that the spines were enormous setae which arose from tiny parapodia. Although parallels with the polychaetes have been drawn above with the spine muscles and method of locomotion, the author believes that a direct relation- ship is unjustified. The polychaete aciculae do not project as far beyond the trunk as the spines of H. sparsa. Furthermore, Manton (1967) noted that in polychaetes that walk upon their neuropodia the aciculae are never enlarged to act as stilts. The pro- posed similarity between the polychaete acicular muscles and those inserted on to the spines results from a common attempt to obtain a universal-joint system, and is with- out phylogenetic significance. The horseshoe-shaped insertion lines of H. sparsa have no direct counterpart in the polychaetes. Thickened acicular setae replace some or all the normal setae in some polychaetes. To the author’s knowledge, however, the acicular setae are never reduced to one per parapodium, nor are they as large. Moreover, if the ventro-lateral spines were to be interpreted as arising from the neuropodia, there is no trace of the corresponding notopodia. There is no evidence to suggest that the pairs of spines exposed in laterally preserved specimens belong only to one side of the animal, with another pair hidden beneath the body. In these specimens the spines of each pair are often separated by a layer of rock, that in USNM 83935 and USNM 198658 was removed with a dental micro-drill to expose the lower spines (PI. 73, figs. 1, 2; PI. 74, figs. 5, 6; text-figs. 1, 3). This indicates that each spine of a pair belongs to one side of the animal. Vertically orientated specimens confirm this observation (PI. 76, figs. 3-5). In the great majority of polychaetes, the number CONWAY MORRIS; CAMBRIAN METAZOAN 639 of setiferous segments increases with age, whereas H. sparsa has seven pairs of spines regardless of size. Similarly the tentacles cannot be compared with the cirri of polychaetes. The Heterospionidae and Cirratulidae have numerous dorsal cirri, and the Cossuridae has a single dorsal tentacle. None of these polychaetes, however, has seven cirri arranged in a single median row, succeeded by three pairs of shorter cirri. These three polychaete families are, moreover, typical of their class and show no especially aberrant features. The cirri of polychaetes do not have bifid tips, and although the gills of the oligochaete Alma nilotica are sometimes bifid (Gresson 1927), they are in no other way at all comparable. Unlike the tentacles of H. sparsa, the cirri never project into the body cavity and join a central tube, but arise instead from the surface. The tentacles of H. sparsa were almost certainly hollow. Although the polychaete cirratophore contains a coelomic space (Lawry 1971), the cirrus itself is solid with a central mass of nervous tissue (Lawry 1967; Boilly-Marer 1972a, b). It may be concluded that H. sparsa cannot be placed in the polychaetes. Its affinities remain uncertain. The seven-fold repetition, presumably some sort of segmentation, of the tentacles and spines is unusual. The total number of ‘segments’ is difficult to evaluate. There are at least seven, but the unopposed tentacle Ti and spine Svh, and the cluster of short tentacles suggest that there may be another three ‘segments’. There are very tentative grounds for suggesting a comparison with the Echinodermata. If the tentacles were joined to the trunk tube, they would not be dissimilar to the canal and podia of the water vascular system of the Echinodermata. The tentacles and trunk tube might have formed a hydrostatic system with food-collecting move- ments of the tentacles being powered by fluid pressure. This interpretation assumes that the bifid tips did not house mouths, and raises the question of the location of the gut. This suggestion must, therefore, remain speculative. Acknowledgements. I am very grateful to my supervisor Professor H. B. Whittington for helpful discussion and criticism of this paper which forms part of my Ph.D. thesis. Helpful comments on this animal were offered by Dr. R. Hessler and Professor M. F. Glaessner. Dr. M. F. Brookfield kindly made available unpublished information on fossil echinoids. I thank Dr. R. E. Grant and Mr. F. J. Collier of the National Museum of Natural History, Washington, D.C., and Professor B. Kummel and Vickie Kohler of the Museum of Comparative Zoology, Harvard, for help during my visits and loan of specimens from their respective institutions. The initial part of this work was undertaken under a Natural Environment Research Council studentship, and the remainder as a research fellow of St. John’s College, Cambridge. REFERENCES BARDACK, D. 1974. A larval fish from the Pennsylvanian of Illinois. J. Paleont. 48, 988-993. BOILLY-MARER, Y. 1972fl. Presence de cellules de type myoepithelial chez les Nereidae (Annelides polychetes). J. Microsc. 15, 253-256. \912b. Etude ultrastructurale des cirres parapodiaux de Nereidiens atoques (Annelides polychetes). Z. Zellforsch. mikrosk. Anat. 131, 309-327. CLARK, R. B. 1964. Dynamics in metazoan evolution. Oxford. 313 pp. and CLARK, M. E. 1960. The ligamentary system and segmental musculature of Nephtvs. Q. Jl microsc. Sci. 101, 149-176. 640 PALAEONTOLOGY, VOLUME 20 CONWAY MORRIS, s. 1976a. A new Cambrian lophophorate from the Burgess Shale of British Columbia. Palaeontology, 19, 199-222. 1976h. Worms of the Burgess Shale, middle Cambrian, Canada. Unpubl. Ph.D. thesis, Cambridge University. FRITZ, w. H. 1971. Geological setting of the Burgess Shale. In Extraordinary fossils. Symp. North Amer. Paleont. Conv. 1969, Pt. I, 1 155-1170. GRESSON, R. 1927. On the structure of the branchiae of the gilled oligochaete Alma nilotica. Ann. Mag. nat. Hist. (9th ser.) 19, 348-360. ISSACS, J. D. and schwartzlose, r. a. 1975. Active animals of the deep-sea floor. Scient. Am. 233, 84-91. LAWRY, j. V. 1967. Structure and function of the parapodial cirri of the polynoid polychaete, Harmothoe. Z. Zellforsch. mikrosk. Anat. 82, 345-361. 1971. The parapodial and segmental musculature of Harmothoe imhricata (L.). J. Morph. 135, 259-272. MANTON, s. M. 1967. The polychaete Spinther and the origin of the Arthropoda. J. nat. Hist. 1, 1-22. MARSDEN, J. R. 1966. Segmental musculature and locomotion in Hermodice carunculata (Polychaeta; Amphinomidae). J. Morph. 119, 259-276. METTAM, c. 1967. Segmental musculature and parapodial movement of Nereis diversicolor and Nephthys homhergi (Annelida: Polychaeta). J. zool., Lond. 153, 245-275. 1971. Functional design and evolution of the polychaete Aphrodite aculeata. Ibid. 163, 489-514. MORTENSEN, TH. 1940. A monograph of the Echinoidea, III. 1. Aulodonta. Copenhagen. 370 pp. PIPER, D. J. w. 1972. Sediments of the Middle Cambrian Burgess Shale, Canada. Lethaia, 5, 169-175. SCHAFER, w. 1972. Ecology and palaeoecology of marine environments. Edinburgh. 568 pp. WALCOTT, c. D. 191 1. Middle Cambrian annelids. Cambrian geology and paleontology, II. Smithson, misc. Colins, 57, 109-144. 1912a. Middle Cambrian Branchiopoda, Malacostraca, Trilobita and Merostomata. Cambrian geology and paleontology, II. Ibid. 145-228. 1912/?. Cambrian of the Kicking Horse Valley, B.C. Rep. geol. Surv. Can. for 1911, 188-191. 1931. Addenda to descriptions of Burgess Shale fossils (with explanatory notes by C. E. Resser). Smithson, misc. Colins, 85, 1-46. WHITTINGTON, H. B. 1971a. The Burgess Shale: History of research and preservation of fossils. In Extra- ordinary fossils. Symp. North Amer. Paleont. Conv. 1969, Pt. I, 1170-1201. 1971/?. Redescription of Marrella 5/?/e«r/ea5(Trilobitoidea) from the Burgess Shale, Middle Cambrian, British Columbia. Bull. geol. Surv. Can. 209, 1-24. Typescript received 29 March 1976 Revised typescript received 15 July 1976 S. CONWAY MORRIS Department of Geology Sedgwick Museum Cambridge AN UNUSUAL BENN ETTIT ALE AN LEAE FROM THE UPPER TRIASSIC OF THE SOUTH-WESTERN UNITED STATES by SIDNEY R. ASH Abstract. Eoginkgoites davidsonii sp. nov. is a large pinnately compound bennettitalean leaf which has wedge- shaped pinnae. It is unusual because the pinnae are aggregated near the top of a short rachis and not arranged laterally on a long rachis as in other pinnate bennettitalean leaves. The veins radiate from the base of each pinna and divide and anastomose several times before reaching the margins and apices. The cuticle of the new species shows paracytic (syndetocheilic) stomata. Typically E. davidsonii sp. nov. is larger than the other species of the genus. E. davidsonii sp. nov. occurs at seven localities in the basal strata of the Upper Triassic Chinle Formation in Arizona and southern Utah and appears to be confined to the lowest unit (Shinarump Member) of the formation. Another one of the unusual plant fossils that occur in the Upper Triassic rocks of the south-western United States is described in this report. However, unlike the others (e.g. Sanmiguelia Brown, 1956, Diuophyton Ash, 1970, and Dechellyia Ash, 1972), the relationships of this fossil are reasonably certain. The fossil described here is a large pinnately compound leaf which has wedge- shaped pinnae. It has paracytic (syndetochelic) stomata so the fossil is assigned to the bennettitales. The leaf is unusual because the pinnae are aggregated near the top of a short rachis instead of being arranged laterally on a long rachis as in other pinnate bennettitalean leaves. The remains of the leaf described here were first discovered during the early 1950s by field parties of the U.S. Geological Survey who were investigating the occurrence of uranium in the South-west. Those geologists found the leaf at four localities in the basal beds of the Upper Triassic Chinle Formation in Utah and Arizona (localities 1, 3, 6, 7 on text-figs. 1-3). Brown {in Davidson 1967; Smith et al. 1963; and Stewart et al. 1972) identified the fossil as the remains of the pinnate bennettitalean leaf Sphenozamites rogerskmus Fontaine. During the past several years I also found the same leaf in the Chinle at other places (localities 2, 4, 5) in Utah and Arizona. Some of the specimens I collected were more complete than those examined by Brown and after study it became evident that the leaf is not related to S. rogersianus. Instead it is probably congeneric with Eoginkgoites Bock, 1952 from the Upper Triassic Newark Group of Pennsylvania as they both have the same shape and venation. Although Bock had attributed Eoginkgoites to the Ginkgoales cuticular studies of the Chinle, specimens showed that the genus actually is bennettitalean. Subsequently Eoginkgoites was redescribed and transferred to the Bennettitales (Ash 1976). All the fossils attributed to Eoginkgoites are similar in architecture and venation. The fossils from Pennsylvania, however, are the remains of leaves that typically are smaller than those found in the south-western United States. Also the proportions of the pinnae are different, those from Pennsylvania being much narrower for their [Palaeontology, Vol. 20, Part 3, 1977, pp. 641-659, pis. 77-79.] 642 PALAEONTOLOGY, VOLUME 20 114° 112° 110° TEXT-FIG. 1 . Index map showing by numbers the localities that have yielded Eogmkgoites davidsonii sp. nov. (See the text for a description.) Other significant fossil-plant localities in the Chink Formation are shown by encircled letters. They are CR, Capitol Reef National Park, Utah; FW, Fort Wingate, New Mexico; PF, Petrified Forest National Park, Arizona; SJ, St. Johns, Arizona, The same localities and symbols are used on text-figs. 2 and 3. length than those from the South-west. Therefore, I believe that the fossils attributed to Eoginkgoites from the South-west should go into a new species which is described in this paper as E. davidsonii sp. nov. The abbreviations listed below are used in text-fig. 6 and Plates 77-79. They are the same as those used by Harris (1932/?) in his study of cycadophyte stomata: d— dorsal guard cell cuticle; e— epistomatal pit; f— free edge of dorsal guard cell cuticle; g— guard cell; i— inner end of aperture tube; 1— line of attachment of cuticle of subsidiary cell; o— outer end of aperture tube; oe— opening into epidermal cell papilla; os— opening into subsidiary cell papilla; p— polar region of guard cell; s— stomatal pore; su— subsidiary cell; w— wall separating guard cells. GEOLOGIC SETTING The Chinle Formation, which contains the new species of Eoginkgoites, is widely exposed in the south-western United States and ranges from 0 to about 450 m in thickness. It consists principally of structureless claystone although it also contains significant amounts of conglomerate, sandstone, siltstone, and mudstone. Locally ASH: TRIASSIC BENNETTITALE AN LEAF 643 the formation also contains thin interbeds of coaly material. The formation was deposited in a large inland basin by streams and in lakes and swamps during Late Triassic time. As a consequence of its environment of deposition the formation consists of several discontinuous lithologic units that often interfinger and intergrade along their boundaries. Various aspects of the complex stratigraphy of the Chinle have been discussed in a number of publications since the formation was first described by Gregory (1916). The most comprehensive modern discussion is in the report pre- pared by Stewart et al. (1972). Text-fig. 2 summarizes the nomenclature usually applied to the units recognized in the Chinle Formation in southern Utah and Arizona where the new species occurs. The text-figure also shows the stratigraphic position of the localities that contain Eogiukgoites sp. nov. and of the other important Chinle plant localities in the area. The Chinle contains many plant and animal fossils. A summary of the fossils that have been found in the Chinle is contained in a recent symposium (C. S. and W. J. Breed 1972). One of the papers (Ash 1972) in that symposium showed that nearly all the plant megafossils described from the Chinle occur in the lower part of the formation in the Monitor Butte and Petrified Forest Members (see text-fig. 2). The new species, however, occurs only within the lower 1 2 m of the Chinle in the Shinarump Member. The Shinarump Member typically is the lowest unit in the Chinle Formation. In places, such as locality 7, it is underlain by a thin sequence of rocks which are termed ‘mottled strata’. These may represent a soil that developed before the Shinarump North South Mottled Strata TEXT-FIG. 2. Diagram showing the relationships of the various members of the Chinle in parts of Utah and Arizona. The diagram shows by numbers the approximate stratigraphic position of the localities that have yielded Eoginkgoites davidsonii sp. nov. It also shows by encircled letters the position of other signi- ficant fossil-plant localities in the Chinle. L 644 PALAEONTOLOGY, VOLUME 20 was deposited in the area (Stewart et al. 1972). In most parts of the South-west the Shinarump or ‘mottled strata’ rest uncomformably on the underlying Moenkopi Formation of Early and Middle (?) Triassie age. As shown in text-fig. 2 the Shinarump is overlain by various members of the Chinle depending upon the area. The Shinarump averages about 9 m in thickness, but locally may be as much as 75 m thick where it fills channels. In some areas the Shinarump is only a few metres thick and in others it is entirely absent. The member is composed principally of cross-bedded con- glomerate and conglomeratic sandstone, but at some places it also contains lenses and discontinuous beds of finer-grained rocks such as mudstone and siltstone and even carbonaceous layers and lenses of coaly material. Most of the unit is cross-stratified but horizontally bedded and massive strata also occur. Petrified wood and leaf impres- sions and compressions are locally abundant in the Shinarump (Ash 1975u, b). The presence of cross-bedding, scour surfaces, and layers of conglomerate suggest that the Shinarump is principally a stream deposit. It is also suggested by the common occurrence in the member of plant debris such as large logs and local occurrence of continental vertebrate remains (Stewart et al. 1972). The fine-grained carbonaceous deposits and coal that occur in the Shinarump at places, however, probably represent either swamps that occurred along the margins of streams or that formed in abandoned stream channels. Certainly they do not represent high-energy deposits of the central part of streams. LOCALITIES The seven localities which contain E. davidsonii sp. nov. extend from south-central Utah to east-central Arizona, a distance of about 500-0 km (text-fig. 1). The northern- most locality (locality 1) is about 0-5 km east of the headquarters of Capitol Reef National Park in southern Utah. At this locality the leaf occurs in great numbers throughout a lens of brownish mudstone in the base of the Shinarump Member. The lens occupies a channel cut into the Moenkopi Formation (see text-fig. 3). Locality 1 has been assigned U.S. Geological Survey fossil plant locality number 10154. Locality 2 is about 22 km south of locality 1 near the intersection of Oak Creek and Bear Canyons. In the vicinity of the intersection the Shinarump ranges from 0 to 6 m in thickness and occupies a north-eastward trending channel cut into the Moenkopi Formation (Smith et al. 1963). Here the member consists chiefly of sand- stone and conglomerate but it also contains several discontinuous beds of carbonaceous shale and coaly material. The new Eoginkgoites occurs about 1 m above the Moenkopi in carbonaceous shale. Locality 3 is about 10-0 km south of locality 2 and 0-8 km north-west of a butte called the Lamp Stand in the Circle Cliff's area of southern Utah. At this locality the new species occurs in the lower part of the Shinarump in a sequence of cross-bedded white to greyish sandstone and grey to greenish mudstone. The sequence occupies a channel about 9 m deep cut into the underlying Moenkopi Formation. The channel has been traced for a distance of about 100 km and is part of a pre-Shinarump drainage system that developed in the region during Late Triassie time (Davidson 1967, fig. 14). The new species is not very common at locality 3 and all specimens are ASH: TRIASSIC BENNETTITALEAN LEAE 645 fragmentary. This locality has been assigned U.S. Geological Survey fossil plant locality number 10153. Locality 4 is about 23-0 km south of locality 3 and 0-8 km east of the point where Death Hollow Canyon crosses the Moenkopi Formation in the central part of the Circle Cliffs area. The new species occurs about 4-5 m above the Moenkopi Forma- tion in coaly lenses and thin interbeds of mudstone in a bed of sandstone in the upper part of the Shinarump Member (text-fig. 3). Elsewhere in the Circle Cliffs area the bed overlies 30 m or more of white to grey sandstone which fills a deep stream channel cut into the Moenkopi Formation. According to Davidson (1967, fig. 14) this is the same channel that contains the new species at locality 3. In some layers the leaves of Northwest © N e or Death Hollow Conyon, Giro le Cliffs Ufoh I Southeast © Across the Little Colorodo River from Comeron Arizona I TEXT-FIG. 3. Stratigraphic sections of the lower part of the Chinle Formation at some of the localities in Utah and Arizona that have yielded Eoginkgoites dcividsonii sp. nov. The localities where the sections were measured are shown on text-fig. 1 . 646 PALAEONTOLOGY, VOLUME 20 E. davidsonii sp. nov. are very densely packed. The locality has been assigned U.S. Geological Survey fossil plant locality number D1341. Locality 5 is about 150 km east of locality 4 on the north side of The Notch, Elk Ridge, Utah (text-fig. 2). In this area the Shinarump Member ranges from 0 to about 9 m in thickness and consists mainly of cross-bedded sandstone. In places it also contains discontinuous lenses of mudstone that are often fossiliferous. At locality 5 the Shinarump occupies a broad, shallow, westward-trending channel cut into the underlying Moenkopi Formation. The channel is a part of the larger Elk Ridge-White Canyon channel system in which sediment was transported in a westerly direction from the ancient Uncompahgre highlands of western Colorado during Late Triassic time (Lewis and Campbell 1965). This locality has been assigned U.S. Geological Survey fossil plant locality number 9370. Locality 6 is about 250 km south-west of locality 5 across the Little Colorado River from Cameron in north-central Arizona (text-fig. 1). The locality is in a lens of greenish grey mudstone which is about 2 m thick and 60 m wide. The base of the lens is about 3 m above the top of the Moenkopi Formation. The stratigraphic position of the lens is controversial. According to Cooley et al. (1969) it is in the Shinarump Member of the Chinle. Stewart et al. (1972) restrict the Shinarump to the beds of conglomerate and sandstone that directly underlie the lens and assign it to the sand- stone and mudstone member of the Chinle. The presence in the lens of Eoginkgoites (which occurs only in the Shinarump elsewhere in the south-west) suggests that the lens should be included in the Shinarump as shown on text-figs. 2-3. Leaves are very abundant throughout the lens and frequently overlap each other. They are usually well preserved and the new Eoginkgoites is the most common leaf at the locality. This locality has been assigned U.S. Geological Survey fossil plant locality number 9377 and Museum of Northern Arizona locality number 197. Locality 7 is the southernmost locality. It is about 250 km south-east of locality 6 and 8 km south-east of St. Johns, Arizona. At this locality the fossils occur in a lens of white to reddish claystone about 5 m thick and 750 m wide. The lens is separated from the Moenkopi by about 8 m of mottled strata. This locality has been assigned U.S. Geological Survey fossil plant locality number 9373. SYSTEMATIC DESCRIPTIONS Class BENNETTITALES Genus Eoginkgoites Bock, 1952, emend. Ash, 1976 Generitype. Eoginkgoites sectoralis Bock, 1952. Discussion. Three species of Eoginkgoites are now known. They are differentiated more or less arbitrarily on the basis of pinna proportions and size as shown below: Key to the North American species of Eoginkgoites 1. Pinnae broad, length typically 2-4 x width (3-16 cm wide, 15-40 cm long) E. davidsonii sp. nov. 1 . Pinnae narrow, length typically 5-8 x width 2 2. Pinnaetypically 5-15mmbroad, 25-90mmlong E. sectoralis Bock 2. Pinnae typically 40 mm broad, 180 mm long E. gigantea Bock ASH: TRIASSIC BENNETTITALEAN LEAF 647 Bock’s two species, E. sectoralis and E. gigantea, occur in the lower part of the Lockatong Formation of the Newark Group of Late Triassic age in Pennsylvania. E. davidsonii sp. nov. occurs in the basal strata of the Chinle Formation of Late Triassic age in Utah and Arizona. Eoginkgoites has been recognized in the Upper Triassic Pekin Formation of the Newark Group in North Carolina (Hope, written communication, 1975). The specific identity of these fossils is unknown. Eoginkgoites davidsonii Ash Plates 77-79; text-figs. 4-6 1963 Sphenozamites rogersiamis Fontaine ex Brown (in Smith et al. p. 16). Identification only. 1967 Sphenozamites rogersianus Fontaine ex Brown (in Davidson, p. 30). Identification only. 1972 Sphenozamites rogersianus Fontaine ex Brown (in Stewart et ah p. 85). Indentification only. Holotype. USNM 172363. Paratypes: USNM 172357, 172359, 172360. Derivation of name. The specific name honours Edward S. Davidson, of the U.S. Geological Survey who mapped the Circle Cliff's area in southern Utah and gave me much useful information on the localities there that subsequently yielded specimens of the species. Diagnosis. Leaf pinnate, large, width known to reach 90 cm but sometimes as small as 20 cm wide, length unknown. Pinnae borne laterally and terminally on rachis, elosely aggregated at upper end of rachis, apical pinnae usually fused at bases for about 2-4 cm, lateral pinnae free at bases. Pinnae wedge-shaped about equal in size on same leaf, widest near apex (largest 16 cm wide, 45 cm long, smallest 3 cm wide, 15 cm long). Lateral margins straight to slightly curved, without lobes, symmetrically contracted from widest point near apex to base. Apex nearly straight to rounded, occasionally wavy to slightly lobed but never showing sharp indentations or points. Lateral margins scarcely thickened below but gradually developing a thick rim above, apical margins with a strongly thickened rim formed by a marginal vein. Rachis robust, up to 12 mm wide, surfaces smooth and appearing similar, without a groove on the upper side. Veins distinct, radiating from the base of each pinna, rather few and stout near base but forking and anastomosing frequently, in middle of pinna typically 0-1 mm broad, traversing lamina at a concentration of three to four per mm, most veins ending in a marginal vein but some meeting lateral margins and ending at a very acute angle with the margin. Free ends of veins often expanded. Dark rounded bodies about 150 /xmxlOO ^xm, oceurring at interval of about 0-5-L0 mm, also oecasional single longitudinal strands about 20 ;u.m-30 ptm wide oceurring between veins. Cuticle of lamina of medium thickness, about 3 p.m above, 2 ;um below (measured in folds). Details varying in different parts of leaf. Over most of pinna epidermal cells papillate but papillae becoming scarce to absent near pinna base. Upper cuticle generally showing uniform cells, veins not or scarcely indicated, cells tending to be rectangular, in longitudinal files, anticlinal walls strongly marked, essentially straight but always showing jagged and uneven thickenings, sculpturing on periclinal walls consisting of irregular, small thickened areas or low hollow papillae about 10 fxm in diameter. Cells near base of pinnae irregularly arranged. Lower TEXT-FIG. 4, Eoginkgoites davidsonii sp. nov. from the Shinarump Member of the Chinle Formation. A, apex of the rachis and the bases of three pinnae. Dotted lines represent the broken edges of the leaf and the dashed lines indicate the probable position of the pinnae margins. Holotype. USNM 172363, x^. B, D, details of the venation. The dark transverse bars connecting the veins in b and the dark rounded bodies in d may be masses of resin or remnants of the fossilized mesophyll. USNM 222764, 222768, x 10. c, apex of a pinna showing the wavy margin and the veins. Note that there is a large swelling at the end of each vein and that the marginal vein is absent. Some of the veins divide and join at several places in the fossil. USNM 222762, x 5. e, a single cell showing pitting that frequently occurs on the cuticle of this species. USNM 172360b, x400. f, lateral margin of a pinna showing the veins which typically are free in this part of the leaf. USNM 222761, x 5. G, apical region of a pinna showing the venation and the marginal vein which is well developed in this fossil. Some of the veins divide and join at several places in the fossil. USNM 222763, x 5. h, basal region of a pinna showing the spreading veins that divide and join in places. USNM 172357, x 5. Specimens in a, b, d, g, from locality 1 in Capitol Reef National Park, Utah; those in c, E, F, H from locality 4 near Death Hollow Wash in the Circle Cliffs, Utah. ASH: TRIASSIC BENNETTITALEAN LEAF 649 cuticle showing veins distinctly, veins marked by several (usually three) files of elongated cells (20 ;um-50 jxm wide and long), anticlinal walls as on upper cuticle, periclinal walls strongly papillate, most papillae hollow, typically about 14 jxm high, 10 |Ltm in diameter. Some ordinary epidermal cells also bearing large sack-like papillae about 12 jum wide, 50 jxm long. Cuticle of petiole thick, about 5 ;um, anticlinal walls of ordinary epidermal cells strongly marked on both upper and lower cuticles, side walls irregular to slightly wavy (up to 12 ^um), end walls usually thick (up to 3 |um), straight, not irregular. Cells along sides of petiole irregularly arranged, in central region of petiole cells nearly uniform, arranged in longitudinal rows, square to rectangular or polygonal, end walls often arranged at 45° to side walls, periclinal walls smooth. Stomata sparse (twenty to thirty per mm^) on lower cuticle of lamina and petiole, rare (four to nine per mm^) on upper cuticle, scattered or in irregular files between veins, mostly transverse to veins but some oblique or longitudinal particularly near and on petiole. Subsidiary cells rectangular, about the same size as normal epidermal cells, 18-32 fxm long, 15-26 ij.m wide, each bearing a single, hollow, papilla. Papillae 10-16 /xm long, 4-6 ij.m wide, usually overlapping adjacent guard cell and stoma. Guard cell dorsal cuticle thickened, about 4-6 jjim wide, 25-30 jum long, two-thirds covered by subsidiary cell, slightly sunken at the bottom of a shallow rectangular epistomatal pit, lower surface marked with radially running striations about 0-5 fxm broad. Poles of guard cells often overhung by neighbouring epidermal cells. Description of material. This diagnosis is based on several dozen specimens. Most are fragmentary but a number of complete leaves have been observed in the field at locality 1. However, because of their large size and the nature of the matrix it has not been possible to collect an entire leaf from that locality. Estimates of the size of the leaf are based principally on specimens observed at locality 1 . Preservation varies considerably from locality to locality. At locality 2 most of the specimens are only carbon- and iron-stained impressions which give just the out- line and venation of fossil. In many specimens from localities 1 and 7 the leaf substance has contracted into small bits of coaly material which yield tiny (1 mm or less) frag- ments of cuticle upon maceration. In other specimens the leaf is represented by a thin brownish residue. Transfer preparations of some of these specimens did give useful results. At locality 6 the fossil is represented by thin carbonaceous films which can be transferred. At locality 4 the cuticles are well preserved and often can be separated from the rock with a needle or small knife before maceration. Although these cuticles appear to be quite robust in the rock they do not tolerate more than 30 minutes in concentrated HNO3 and KCLO3. In some of the fossils from locality 4 a thin layer of sediment has infiltrated between the upper and lower cuticles of the same leaf. In others there are rows of many low, narrow transverse ridges of brownish carbonaceous material adhering to the lower cuticle (PI. 77, fig. 4). Possibly they are merely the plates observed in the transfer preparations of fossils from locality 6 (text-fig. 4b, d), or they may represent fossilized remnants of the mesophyll. Pinna bases have not been found at locality 6 and they are rare at most other localities. The exception is at locality 1 where they occur quite frequently. Most of the 650 PALAEONTOLOGY, VOLUME 20 pinna bases shown on Plates 77 and 78 are from this loeality. At locality 7 some of the pinnae show evidence of fraying prior to burial. The fraying could have occurred while the leaves were still attached to the plant as in the living Welwitschia or after they fell and were being transported to the burial site. None of the leaves from the other localities shows this feature or any other type of damage. No reproductive organ associated with E. davidsonii seems likely to belong to it. One locality (4) contains the fossil and nothing else. All the others contain several additional leaves although E. davidsonii is the most common fossil. There is nothing to unite the several large unidentified cones that occur with E. davidsonii at locality 1. Discussion. The scanning electron photomicrograph of the stomata of this species in Plate 79, fig. 2 shows that the polar regions of the guard cells are partially divided longitudinally by a plate of cuticle. This observation tends to confirm Harris’s ( 1 932(7, h) contention that the line he and others have observed in the same position on the stomata of several other bennettitaleans with light microscopes is a wall separating the guard cells. Such a line has been observed, for example, on the stomata of Ptero- phyllum rosenkrantzi Harris (1932(7), P. astar tense Harris (\92>2b), P. compressum Lundblad (1959), and Ptilophyllum pecten (Phillips) Harris (1969). The striations noted on the lower surface of the dorsal guard cell cuticle of the new species are rather unusual (PI. 79, fig. 2). These striations are visible with the light microscope (see text-fig. 4d) but it is impossible to determine their position. The scanning electron microscope showed their true position. Similar striations have been observed in only a few other Bennettitaleans such as Williamsonia himas Harris (1953) and Pterophyllum zygotacticum Harris (19326). Sac-like trichomes and medial papillae somewhat similar to those on the ordinary epidermal cells on the lower cuticle of the new Eoginkgoites occur on a second bennettitalean, Zamites powelli, that is found in the Chinle and other Upper Triassic units in North America (Ash 1975, text-fig. 4g). In addition they are similar to the trichomes found on Otozamites penna Harris (1969) from the Middle Jurassic of Yorkshire, Pterophyllum zygotactium Harris (1932(7) from the Rhaetic of Greenland, and P. filicoides (Schlothelm) from the Carnian of Lunz, Austria (see Barnard 1970). EXPLANATION OF PLATE 77 Figs. 1-9. Eoginkgoites davidsonii sp. nov. from the Shinarump Member of the Chinle Formation, Utah and Arizona. 1, apex of a pinna. The thickened rim formed by the marginal vein is darker than the rest of the pinna. Slide, USNM 172355, x 1. 2, bases of two pinnae, USNM 172366, xT 3, naturally macerated pinna in which the venation is visible, USNM 172356, x^. 4, paratype, apex of the rachis and the base of several pinnae. The lower cuticle has been removed from the lamina and the upper part of the rachis. USNM 172360, x 1. 5, paratype, rachis and remains of a lateral pinna, USNM 1723M, x 1. 6, apical region of the rachis and the remains of four pinnae, USNM 172358, x^. 7, 8, slightly lobed apices of two pinnae, USNM 172365, Xj, USNM 172364, x 1. 9, remains of three pinnae, USNM 172359, xT Specimens in 1 and 8 from locality 6 near Cameron, Arizona; specimens in 2, 3, 6, 7, 9 from locality 1 in Capitol Reef National Park, Utah; specimen in 4 from locality 4 in the Circle Cliffs area, southern Utah; specimen in 5 from locality 7 near St. Johns, Arizona. PLATE 77 ASH, Triassic bennettitalean leaf 652 PALAEONTOLOGY, VOLUME 20 Small angular pits 2-12 nm in cross-section occur on the lower cuticle in the basal part of some pinnae of the new species (text-fig. 4e). Similar pits have been observed on the cuticle of the Chinle bennettitalean leaf Nilssoniopteris sp. nov. (Ash 1972), and on the cuticle of the Chinle conifer Pagiophyllum sp. C (Ash 1972). They have been observed also on the cuticles of other extinct conifers, such as Stabbarpia Florin (1958) and on the cuticles of certain living conifers including Sequoiadendron giganteum (see Florin 1931). Such pits have been attributed to calcium oxalate crystals embedded in the outer walls of the epidermal cells of these leaves by Florin (1958, p. 310). The pits do compare favourably in size and shape with calcium oxalate crystals that 1 have obtained by evaporating a solution of calcium oxalate dissolved in dilute hydrochloric acid. In one specimen of the new species from locality 1 the petiole is represented by a limonite-stained cast about 3 cm long, 4 mm thick, and 8 cm wide. The surface of the cast is covered with a thin layer of carbon. Several thin irregular layers of carbon occur also within the core and form an irregular oval as shown in text-fig. 5h-j. Probably at least some of these layers represent the crushed vascular tissue of the petiole. There is no evidence of a medial groove or of two vascular bundles in the cast as reported in the petiole of E. gigantea by Bock (1969). In fact the carbonaceous layers seem to match the arrangement of vascular tissue reported in Monathesia and other petrified cycadeoid stems (see Delevoryas 1959). Comparisons. As noted earlier the leaf described here can be separated from the other species of the genus Eoginkgoites by the proportions of the pinnae. What are taken to be typical pinnae of E. davidsonii sp. nov. are much longer and wider than the pinnae of both E. sectoralis and E. gigantea and they should not be confused. Small pinnae of E. davidsonii sp. nov., however, may cause confusion as they are about the same length as the pinnae of E. gigantea. Generally the small pinnae of the new species are much wider than the pinnae of the other species and thus are easily distinguished. Regretfully nothing is known about the cuticle of the E. seetoralis and E. gigantea so additional comparisons are limited. The leaf called E. davidsonii sp. nov. can be easily distinguished from Sphenozamites rogersianus Fontaine (1883) the species with which it was confused by Brown (see synonymy). The basic architecture of the two leaves is very different. In S. rogersianus. EXPLANATION OF PLATE 78 Figs. 1-3. Scanning electron photomicrographs of the outer surface of the lower cuticle of Eoginkgoites davidsonii sp. nov. 1, papilla on an ordinary epidermal cell of the lamina. Many small wrinkles and pits are visible on both the papilla and adjacent surfaces, x 4000. 2, 3, stomatal apparatuses and subsidiary cell and ordinary epidermal cell papillae. Note the rectangular epistomatal chambers at several places in the figures. The outer surface of the dorsal guard-cell cuticles form the floors of chambers. Several of the papillae shown in the upper part of fig. 3 have collapsed giving them the appearance of doughnuts. 2, X 1200; 3, x 1000. Material from the Shinarump Member of the Chinle Formation at locality 4 in the Circle Cliff's area, southern Utah. PLATE 78 ASH, Triassic bennettitalean leaf TEXT-FIG. 5. Eoginkgoites davidsonii sp. nov. from the Shinarump Member of the Chinle Formation. A, lower cuticle of lamina in the upper part of a pinna showing two stomatiferous zones. Note that each of the epidermal cells shows a medial papillae as is typical of the cells in this part of the leaf. Several of the large sac-like papillae are also present. Compare with d. USNM 172368, x 100. b, fold in the cuticle of the lamina showing the medial papillae. USNM 172362, x200. c, papillae along the edge of the apex of a pinnae. USNM 222766, x 200. d, upper cuticle of the lamina in the basal part of a pinna. As indicated in the figure the outer surfaces of the epidermal cells are typically smooth and non-papillate in the basal part of the pinnae of this species. Compare with a. USNM 172360a, x 100. e, upper cuticle of the lamina in the upper part of a pinna showing papillate epidermal cells as is characteristic of this part of the leaf. Note the absence of stomata. USNM 172362, x 100. f, lower cuticle of the lamina a short distance above the basal region of a pinna. In this part of the leaf the epidermal cells are more irregular than higher up and the stomatiferous zones and non-stomatiferous zones are not as well defined. Compare with a. USNM 172360a, x 100. g, cuticle from the petiole showing elongate thick-walled epidermal cells. USNM 222765, X 100. H-j, cross-sections of the petiole. The carbonaceous material in the sections is indicated by dots. USNM 222767a, b, x 5. k, distribution and orientation of stomata (short lines) in 1 sq mm of the petiole cuticle. USNM 222765, x 25. l, distribution and orientation of stomata (short lines) and of papillae (dots) on 1 sq mm of the lower cuticle of the lamina a short distance above the basal region of a pinna. USNM 172362, X 50. Specimens in a, h-j from locality 1 in Capitol Reef National Park, Utah; those in b-g, K, L from locality 4 near Death Hollow Wash in the Circle Cliffs area, Utah. ASH: TRIASSIC BENNETTITALEAN LEAF 655 which for no clear reason was transferred by Boek to the genus Glandulozamites, the pinnae are arranged laterally on a long rachis whereas in the new species the pinnae are arranged at the end and along the margins of a very short rachis. In S. rogersiamts there are typically two or three pinnae with fused bases at the end of the rachis but only one in the new species. The pinnae also show significant differences. In S. rogersianus the pinnae are obovate to rectangular and in the new species they are wedge-shaped. The venation is free dichotomous in S. rogersianus whereas it is anastomosing in E. davidsonii. Pinnae of the new Eoginkgoites are somewhat like certain species of the Permian- Triassic genus Noeggerathiopsis Feistmantel (see Maithy 1965) and the poorly known Triassic genus Chiropteris Kurr (in Bronn 1858). Noeggerathiopsis and Chiropteris are simple leaves consisting of an ovate to spathulate blade which usually has a broadly TEXT-FIG. 6. Eoginkgoites davidsonii sp. nov. from the Shinarump Member of the Chinle Formation. A, general appearance of a stoma and subsidiary cells. Note that the polar regions of the guard cells are strongly overlapped by adjacent ordinary epidermal cells. USNM 172367, x 800. b, reconstructed transverse section through the stoma in a. The cuticle is shown in solid black and the missing cell waits are indicated by dashed lines, x 800. c, stoma from the basal part of a pinna. The epistomatal pit has been slightly offset to the left. Holotype. USNM 172363a, x 400. d, stoma from the lower cuticle in the upper part of a pinna. Several of the sac-like papillae are present in addition to the ordinary medial papillae. USNM 172368, X 400. The specimen in a and b is from locality 5 on Elk Ridge, Utah, the specimen in c is from locality 1 in Capitol Reef National Park, Utah, and the specimen in d is from locality 4 near Death Hollow Wash in the Circle Cliffs area, Utah. 656 PALAEONTOLOGY, VOLUME 20 rounded apex and sides that taper evenly to a narrow base. None of the species of those two genera, however, has lateral pinnae below a terminal pinna as in E. davidsonii sp. nov. Also the pinnae of the new species are usually larger than either Noeggera- thiopsis and Chiropteris. The venation is free dichotomous in Noeggerathiopsis whereas it is anastomosing in E. davidsonii sp. nov. and there is a ring of subsidiary cells around the guard cell pair in Noeggerathiopsis (one subsidiary cell opposite each guard cell in the new species). The venation of Chiropteris and the new species is anastomosing and remarkably similar. However, the cuticle of Chiropteris is unknown and the fossil is often classified as a fern. Comments. As noted above, E. davidsonii sp. nov. occurs only in the basal strata of the Chinle Formation in the Shinarump Member. It does not occur in the large floras known from higher Chinle strata at Fort Wingate, New Mexico (Ash 1970u, 1972), in Petrified Forest National Park, Arizona (Daugherty 1941 ; Ash 1972), in Capitol Reef National Park, Utah, or near St. Johns, Arizona. The relative stratigraphic position of these localities is shown on text-fig. 2. Also the species has not been recognized in any of the several dozen smaller floras known from the Chinle else- where in the South-west (Ash 1972; Stewart et al. 1972) or in any other formation. The limited distribution of E. davidsonii sp. nov. suggests that it was narrowly restricted both geographically and stratigraphically. Undoubtedly this is due at least in part, to the incompleteness of the fossil record but, nevertheless, it appears that the new species may be a guide fossil to the lowermost part of the Chinle Formation. Probably E. davidsonii sp. nov. lived in a very moist environment in or adjacent to swampy areas. It is most abundant at localities 1 , 4, and 5 where it is densely packed in thin lenses that have a limited lateral extent. These lenses appear to have accumu- lated in swamps or a paludal environment of some sort. They consist of dark mud- stone that contains fern leaves and many other plant fossils and much organic matter. In addition the stems of Equisetites occur in the position of growth in one of these lenses at locality 1 in Utah. The new species appears to have been a dominant in the Upper Triassic environments represented by the deposits. Eoginkgoites is uncommon at the other localities in the South-west and most of the specimens are fragmentary. Some are frayed as if they had been transported some EXPLANATION OF PLATE 79 Figs. 1 -2. Scanning electron photomicrographs of the cuticle of Eoginkgoites davidsonii sp. nov. 1, general view of a stomatal apparatus and vicinity. A second stomatal apparatus is in the upper-left corner of the figure. Openings into ordinary epidermal and subsidiary cell papillae are visible at several places. Note the irregular anticlinal flanges of the subsidiary and ordinary epidermal cells, x2800. 2, stomatal apparatus seen from the inside of the cuticle showing prominent radiating striations on the guard-cell’s cuticle. The area of overlap of the polar regions of the guard cells by adjacent ordinary epidermal cells is visible in this figure. The wall separating the guard cells in the polar regions is at w. Note that the anticlinal flanges of the subsidiary and ordinary epidermal cells are rather irregular. Compression of the thin cuticle of the free edge of the dorsal guard-cell cuticle has formed a thickened rim. Compare this figure with the diagram of a bennittitalean stomata given by Harris (1932, fig. 37h), x 3000. Material from the Shinarump Member of the Chinle Formation at locality 4 in the Circle Cliff's area, southern Utah. PLATE 79 ASH, Triassic bennettitalean leaf 658 PALAEONTOLOGY, VOLUME 20 distance. Only a few other plant fossils occur at these localities and they too are frag- mentary. The containing rock at these localities is light coloured shale or sandstone which does not contain much organic matter. The sandstone beds often show cross- bedding and other features characteristic of stream deposits. Possibly Eoginkgoites lived in the swampy margins of Upper Triassic streams and its remains fell into the moving water together with other plants and they were generally fragmented before burial. Certain features of E. davidsonii sp. nov. suggest that the plant grew in a warm, moist environment and substantiate the theory that it inhabited a paludal environ- ment. This is especially obvious if E. davidsonii sp. nov. is compared with the Jurassie plants of Yorkshire which are thought to have grown in a moist tropical climate (Seward 1933). These features include: 1. A relatively thin cuticle (often thick in the Jurassic plants of Yorkshire). 2. Some stomata on upper side of leaf (nearly always limited to the lower cuticle of the Yorkshire Jurassic plants). 3. Individual stomata only slightly sunken and stomatal surface not in grooves (mostly sunken and often in grooves in the Jurassic plants of Yorkshire). 4. Subsidiary cell papillae small and rarely covering aperture (subsidiary eell papillae often large and eovering aperture in the Jurassic plants of Yorkshire). 5. Broad, rather thin lamina (frequently contracted and thick in the Jurassic plants of Yorkshire). Acknowledgements. I am grateful to Professor T. M. Harris and Dr. Peter Barnard, University of Reading, for their comments about this report. Also I acknowledge with thanks the assistance of Arthur H. Watt, Washington, D.C. who loaned specimens of this species to me from the stratigraphic collections of the U.S. Geological Survey, the assistance of Marianne Abel, Philadelphia, Pennsylvania, who loaned me specimens of E. sectoralis from the collections of the Academy of Science, and the help of E. S. Davidson, Tucson, Arizona, who directed me to some fossil plant localities in the Circle Cliffs area, Utah. I thank the Superintendent, Capitol Reef National Park, Utah, for allowing me to collect from areas under his super- vision. Research supported by the Earth Sciences Section, National Science Eoundation, Grant GA-25620. The fossils described here have been deposited in the U.S. National Museum (USNM), Washington, D.C. REFERENCES ASH, s. R. 1970fl. Ferns from the Chinle Formation (Upper Triassic) in the Fort Wingate area, New Mexico. Prof. Pap. U.S. Geol. Surv. 613-D, D1-D52, 5 pis., 19 figs. 1970b. Dinophyton, a problematical new plant genus from the Upper Triassic of the southwestern United States. Palaeontology, 13, 646-663, pis. 122-124, 6 figs. 1972. Plant Megafossils of the Chinle Formation. In breed, c. s. and w. j. (eds.). Investigations of the Chinle Formation. Bull. Mus. Northern Ariz. 47, 23-43, 1 pi., 4 figs. 1975a. Zamites powelli and its distribution in North America. Palaeontographica, 149 (B), 139-152, 2 pis., 5 text-figs. 1975b. The Chinle (Upper Triassic) flora of southeastern Utah. Four Corners Geol. Soc. Guidebook, 8th Field Conf, Canyonlands, 143-147, 6 figs. 1976. The systematic position of Eoginkgoites. Am. J. Bot. 63. BARNARD, p. D. w. 1970. Upper Triassic plants from the Kalawch River, North-east Afghanistan. In Italian E.xped. Karkorum (IC) and Hindu Kush, Sci. Repts. Pt. 4, 2, pp. 25-40, pis. 4-5, 3 figs. BOCK, w. 1952. New eastern Triassic ginkgos. Bull. Wagner Free Inst. Sci. 27, 9-14, 1 pi. 1969. The American Triassic flora and global distribution. Geol. Cen. Res. Ser. 3 and 4, 406 pp., 639 figs. ASH: TRIASSIC BENNETTITALEAN LEAF 659 BREED, c. s. and w. J. (eds.) 1972. Investigations in the Triassic Chink Formation. Bull. Mas. Northern Ariz. 47, 103 pp. BRONN, J. G. 1858. Beitrage zur triassischen Fauna und Flora der bituminosen Schiefer von Raibl. Neues Jahrb. Min., GeoL, Paldo. 1-32, 129-144, pis. 1-12. BROWN, R. 1956. Palmlike plants from the Dolores Formation (Triassic) southwestern Colorado. Prof. Pap. U.S. Geot. Survey, 274-H, 205-209, pis. 32-33. COOLEY, M. E., HARSHBARGER, J. w., AKERS, J. p., HARDT, w. F. and HICKS, o. N. 1969. Regional hydrogcology of the Navajo and Hopi Indian reservations, Arizona, New Mexico and Utah. Ibid. 521-A, A-1 -A-61, 5 pis., 20 figs., 8 tables. DAUGHERTY, L. H. 1941. The Upper Triassic flora of Arizona with discussion of its geologic occurrence by H. R. Stagner. Carnegie Inst. Washington Pub. 526, 108 pp., 34 pis. DAVIDSON, E. s. 1967. Gcology of the Circle Clilfs area, Garfield and Kane Counties, Utah. Bull. U.S. Geol. Survey, 1229, 140 pp., 2 pis., 20 figs., 7 tables. DELEVORYAS, T. 1959. Investigations of North American Cycadeoids: Monanthesia. Amer. J. Bot. 46, pp. 657-666, 23 figs. DORF, E. 1958. The geologic distribution of the Ginkgo family. Bull. Wagner Free Inst. Sci. 33, pp. 1-8, 3 figs, FLORIN, R. 1931. Untersuchungen zur stammesgeschichte der coniferales und Cordiatales. Kgl. Svenska vetenskapsakad handlingar, Ser. 3, 10 (1), 588 pp., 57 pis. 1958. On Jurassic taxids and conifers from northwestern Europe and eastern Greenland. Acta Horti Bergiani, 17 (10), 257-402, pis. 1-56. FONTAINE, w. M. 1883. Contribution to the knowledge of the older Mesozoic flora of Virginia. U.S. Geol. Survey Mon. 6, 144 pp., 54 pis. GREGORY, H. E. 1916. The Navajo country, a geolgraphic and hydrologic reconnaissance of parts of Arizona, New Mexico, and Utah. U.S. Geol. Survey Water Supply Paper, 380, 219 pp. HARRIS, T. M. 1932u. The fossil flora of Scoresby Sound, east Greenland, Part 2. Medd. om Gronland, 85 (3), 1 14 pp., 9 pis., 39 figs. 19326. The fossil flora of Scoresby Sound, east Greenland, Part 3. Ibid. 85 (5), 130 pp., 19 pis., 52 figs. 1953. Notes on the Jurassic flora of Yorkshire, 58-60. Ann. Mag. nat. Hist. Ser. 12, 6, 33-52, 6 figs. 1969. The Yorkshire Jurassic flora. III, Bennettitales. Brit. Mus. (Nat. Hist.), 186 pp., 7 pis., 69 figs. KRAUSEL, R. 1949. Koniferen und andere Gymnospermen aus der Trias von Lunz, Nieder-Osterreich. Palaeontographica, B, 89, pp. 35-82, pis. 6-18, 18 text-figs. and SCHAARSCHMIDT, F. 1966. Die Keuperflora von Neuewelt bei Basel. IV. Pterophyllen und Taeniopteriden. Schweizerische Paldont. Abh. 84, 1-64, pis. 1-15, figs. 1-11. LEWIS, R. Q. and Campbell, r. h. 1965. Geology and uranium deposits of Elk Ridge and vicinity, San Juan County, Utah. Prof. Pap. U.S. Geol. Survey, 474-B, 69 pp., 2 pis., 33 figs., 4 tables. LUNDBLAD, A. B. 1959. Studies in the Rhaeto-Liassic floras of Sweden, 11:1, Ginkgophyta from the mining district of northwest Scania. Kgl. Svenska vetenskapsakad handlingar, Ser. 4, 6 (2), 38 pp., 6 pis., 9 figs. MAiTHY, p. K. 1965. Studies in the Glossopteris flora of India— 20. Noeggerathiopsis and allied remains from the Karharbari Beds, Giridih Coalfield, India. Paleobotanist, 13, pp. 94-IO(), 1 pi. SCOTT, R. A. 1960. Pollen of Ephedra from the Chinle Formation (Upper Triassic) and the genus Equiseto- sporites. Micropaleontology, 6, pp. 271-276, 1 pi., 2 figs. SEWARD, A. c. 1933. Plant life through the ages. Cambridge Univ. Press, 603 pp., 139 figs. SMITH, J. F. Jun., HUFF, L. D., HiNRiCHS, E. N. and LUEDKE, R. G. 1963. Geology of the Capitol Reef area, Wayne and Garfield Counties, Utah. Prof. Pap. U.S. Geol. Survey, 363, 102 pp., 2 pis., 33 figs. STEWART, J. H., POOLE, F. G., WILSON, R. F., CADIGAN, R. A., THORDARSON, W., ALBEE, H. F. 1972. Stratigraphy and origin of the Chinle Formation and related Upper Triassic strata in the Colorado Plateau region. Ibid. 690, 336 pp., 5 pis., 34 figs. S. R. ASH Department of Geology Weber State College Ogden Utah, 84404 U.S.A. Typescript received 9 March 1976 Revised typescript received 1 September 1976 M .V' i'=: : ... i'i'i Sk’:;!:' ■ ADDITIONAL LATE SILURIAN OSTRACODERMS EROM THE LEOPOLD FORMATION OF SOMERSET ISLAND NORTH WEST TERRITORIES, CANADA by E. J. LOEFFLER and b. jones Abstract. An ostracoderm fauna which includes Tolypelepis leopoldensis sp. nov., Corvaspis cf. C. arctica Loeffler and Dinely, and 1 Kallostrakon sp. indet. occurs 30 m above the base of the Leopold Formation on Somerset Island in the Canadian Arctic Archipelago. Associated ostracods and conodonts indicate a Late Ludlovian or Pridolian age for the ostracoderm horizon. Although the lithology of the enclosing sediment suggests that it accumulated in intertidal conditions, the ostracoderms were not necessarily inhabitants of such an environment; some post-mortem transportation of the bony plates may have taken place. The ostracoderms described in this paper were collected 30 m above the base of the Leopold Formation, approximately 75 m above sea level, at Port Leopold (text-fig. 1 ) on Somerset Island. This locality was briefly described by Jones and Dixon (1975, p. 403) but, because of a typographical error, its position was given as 75 m above the base of the Leopold Formation. Vertebrates were first discovered here in 1971, by Dr. O. A. Dixon of the University of Ottawa, but a more extensive collection was made when the authors revisited the site in 1973. The Leopold Formation comprises a complex succession of dolostone, limestone, and sandstone which probably accumulated in supratidal/intertidal conditions. It is becoming apparent that heterostracan ostracoderms were common and quite wide- spread during the period when these sediments were laid down. A fauna containing Archegonaspis cf. A. schmidti Geinitz, Hof^mlaspidella cf. H. borealis Denison, Cyathaspididae indet. and Fleterostraci indet. occurs at a higher stratigraphic level on the eastern side of the bay at Port Leopold (Loeffler and Jones 1976), and ostra- coderms were found at four additional sites during the 1975 field season (text-fig. 1). SUCCESSION AND DEPOSITIONAL ENVIRONMENTS The section in which these ostracoderms were found (text-fig. 2) comprises rocks containing dolomite, calcite, quartz, shell debris, and minor quantities of muscovite. Petrographic analysis suggests that the original sediment was a lime mud, with which small quantities (generally less than 15%) of angular to subangular quartz grains (up to 0-15 mm longest axis, averaging 0-05-0-10 mm) and flakes of muscovite were intermixed. Dolomitization and the formation of evaporites occurred subsequently, probably at an early stage in the post-depositional history of the sediment, leading to the complex lithologic assemblage now found. Dolomite is most common in the basal 30 m of the section (text-fig. 2, units 1-13), [Palaeontology, Vol. 20, Part 3, 1977, pp. 661-674, pi. 80.] 662 PALAEONTOLOGY, VOLUME 20 TEXT-FIG. 1. Map of north-eastern Somerset Island, showing ostracoderm localities in the Leopold Formation. where it is closely associated with evaporites, the latter being restricted to this interval. At the present day, the synchronous formation of dolomite and evaporites is generally associated with sabkha-like environments, as exemplified by the Persian Gulf area (Bathurst 1971, pp. 205-211). The detrital quartz and muscovite may have been brought into the area from the near-by landmass (Jones and Dixon 1975) by inter- mittent currents or local winds. Immediately above the evaporite-dolomite part of the sequence, there is a marked decrease in the amount of dolomite, and a complete absence of evaporites. Units 14-21 thus mark a change in depositional conditions, the sabkha-like environment LOEFFLER AND JONES: SILURIAN OSTRACODERMS 663 UNIT ROCK M NUMBER TYPE ASSOCIATED FEATURES 20- 10- oJ 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 Ostracoderm Horizon Cavities - up to 3 cm diameter- filled with gypsum Vuggy Vuggy Dolomitic Limestone Micntic Limestone Dolomite - L Sandy Dolomite Evaponte MS Millli Calcareous Dolomite Intraformational Conglomerate Stromatolites NE No Exposure TEXT-FIG. 2. Measured section, commencing above second waterfall in gorge on the west side of the bay at Port Leopold, showing lithological divisions and the position of the ostracoderm horizon. The base of the section is approximately 10 m above the base of the Leopold Formation. having been replaced by one in which dolomite formation was minimal and evaporite formation had ceased. The same part of the sequence also contains evidence of more favourable biotic conditions; pellets are present in some units (e.g. unit 17) and shell fragments (primarily ostracods) in others. Together these facts suggest that units 14-21 accumulated in the intertidal environment, possibly in a tidal flat zone. 664 PALAEONTOLOGY, VOLUME 20 ASSOCIATED FAUNA In the measured section (text-fig. 2), unit 20 is the only unit in which fossils, other than shell fragments, occur. Dr. M. J. Copeland has identified the following ostracods (since they are steinkerns, specific identifications could not be made) : Dizygopleura ? sp., Cytherellim sp., Eukloedenella sp., Kloedenia sp. of ‘A", montaguensis (Weller) type, Zygobeyrichia? sp., Baschkirina sp. Copeland (1975, written comm.) states that ‘A Late Silurian, Cayugan, age is most probable for this assemblage, based on similar faunas present in the Decker, Manlius, and Cobleskill limestones of northeastern United States’. The conodont Ozarkodina confluens (Branson and Mehl), approaching the e morphotype of Klapper {in Klapper and Murphy 1974) occurs in unit 20, together with the ostracods and ostracoderms. According to Dr. T. T. Uyeno (1975, written comm.), who identified the conodonts, ‘the e morphotype of O. confluens was previously reported from the level of the Pelekysgnathus index fauna, of early Pridolian age (Klapper and Murphy 1974). The Port Leopold individuals are not exactly like those described from the Roberts Mountain Formation, but may suggest a Late Ludlow or Early Pridolian age.’ SYSTEMATIC PALAEONTOLOGY The ostracoderms described in this paper are the property of the National Museum of Canada, and bear their catalogue numbers (prefixed NMC); they will eventually be housed in that institution. Order heterostraci Lankester, 1868 Family cyathaspididae Kiaer, 1932 Subfamily tolypelepidinae Denison, 1964 Genus tolypelepis Pander, 1856 Synonymy. See Denison (1964). Diagnosis. After Denison (1964). Dorsal shield broad, preorbital length rather short (orbital length ratio = 0T4). Dentine ridges of central epitegum and postrostral field short and grouped into scale-like areas, with narrower, lower ridges grouped around a coarse, higher central ridge. Type species. Tolypelepis undulatus Pander (1856). Tolypelepis leopoldensis sp. nov. Plate 80, figs. 3-6 Derivation of name. Leopoldensis, from Port Leopold. Synonymy. Ptomaspis sp. nov. (Loeffler, in Jones and Dixon 1975). Diagnosis. Dorsal shield 35 mm long, with width ratio of 0-77. Dentine ridges rather narrow (average 7 per mm) and of low relief over most of the dorsal shield, but wider (4/mm) on the rostrum; posterior scale-like units large and intricately ornamented. LOEFFLER AND JONES: SILURIAN OSTRACODERMS 665 Holotype. Dorsal shield, NMC 21635 (PI. 80, fig. 5; text-fig. 3). Other material. Three incomplete ventral shields, NMC 21636-21638; an isolated scale, NMC 21639. Locality. Thirty metres above the base of the Leopold Formation, on the west side of the bay at Port Leopold, Somerset Island (text-fig. 1). Description. Dimensions of holotype dorsal shield (parameters selected for measure- ment are the same as those used by Denison 1964); Median length Maximum width 35 mm 27 mm Width ratio 0-77 Orbital width 20 mm Orbital width ratio 0-57 Orbital length 5 mm Orbital length ratio 0-14 Pineal length 1 1 mm Pineal length ratio 0-31 The dorsal shield is broad and flat, with a smoothly rounded rostral margin and shallow orbital notches. Its outline has undoubtedly been distorted somewhat by crushing, but maximum width was probably achieved at about mid-length. Although the boundary between the central and the lateral epitega is obscured by damage to the shield, other epitegal divisions are conspicuous; the opposing epitegal margins TEXT-FIG. 3. Tolypelepis leopoldensis sp. nov. Holotype dorsal shield (NMC 21635), showing variation in ornamentation. Plan x2, detail x6. cep— central epitegum; /ep— lateral epitegum; position of orbital notch; pw— position of pineal body; rep— rostral epitegum. 666 PALAEONTOLOGY, VOLUME 20 are bordered by minute tubercles, particularly distinct along the boundary between the central and the rostral epitegum (text-fig. 3). The ornamentation of the rostral epitegum comprises dentine ridges of uniform height, which are broad (4 per mm) and transverse anteriorly; posteriorly, they are narrower and divided into short lengths which have longitudinal and oblique orienta- tions (text-fig. 3). On the lateral epitega, several continuous ridges are parallel to the margin of the shield ; other ridges approach a longitudinal orientation and may be divided into short lengths. In the orbital region, broad (4 per mm) ridges curve around the orbital notch and small tubercles are present to its anterior and posterior. On the central epitegum, including the postrostral field, ridges are divided into short lengths, and grouped into areas which become more scale-like towards the posterior margin of the shield. Within these groupings, the median ridge is commonly wider, higher, and sharper crested than the peripheral ones, although the relief of all of the ridges is rather low. Immediately behind the pineal region, individual groups of ridges are longer and narrower than on the rest of the central epitegum, where 2-3 mm long and 1-5 mm wide is the typical size. Towards the posterior of the central epitegum, the groups of ridges take on an imbricated appearance closely resembling fused scales. These rhomb-shaped, scale-like areas are each approximately 5 mm in diameter, and have intricate ornamentation which comprises shorter ridges and tubercles anteriorly and longer, longitudinal ridges posteriorly (text-fig. 3); each has a median ridge which is higher, wider, and sharper crested than the rest. The posterior margin of the shield is incomplete, some of the fused scales apparently having become detached. It is not possible to distinguish a separate postrostral field within the central epitegum, the ornamentation being gradational. Several short, longitudinal ridges are present over the pineal region, and the surrounding ridges curve around these; there is not a distinct macula. No lateral line sensory pores are distinguishable, but this may be a result of the poor state of preservation. Three incomplete ventral shields, NMC 21636-21638, are referred to this species because of the similarity of their ornamentation to that of the holotype dorsal shield. The most complete of these shields, NMC 21636 (PI. 80, fig. 6) has a deep concavity in its anterior margin, and its anterolateral corners are truncated. Its median length exceeds 28 mm, although the shield is incomplete posteriorly; its total length was probably in the order of 35 mm. The lateral margin of the shield comprises a long, straight, anterolateral part, and a shorter, straight, posterolateral part, the two being separated by a deep notch at the widest part of the shield. The ornamentation of this EXPLANATION OF PLATE 80 Figs. 1, 2. 1 Kallostrakon sp. indet. 1, plate fragment (NMC 21648); magnification x2 approx. 2, detail of ornamentation on plate fragment (NMC 21648); magnification x 12 approx. Figs. 3-6. Tolypelepis leopoldensis sp. nov. 3, fragment of ventral shield (NMC 21637); magnification X 2 approx. 4, isolated scale (NMC 21639); magnification x 2 approx. 5, holotype dorsal shield (NMC 21635); magnification x2 approx. 6, ventral shield (NMC 21636); magnification x2 approx. Fig. 7. Corvaspisci. C. arctica Loeffler and Dineley. Median plate (NMC 21642); magnification x 1 approx. PLATE 80 LOEFFLER and JONES, Silurian ostracoderms 668 PALAEONTOLOGY, VOLUME 20 TEXT-FIG. 4. Tolypelepis leopoldensis sp. nov. Ventral shield (NMC 21637) fragment, showing scale-like subdivisions. Plan x2, detail x6. scale-like subdivisions of the shield. specimen (NMC 21636) is poorly preserved, but is seen to comprise short, non- uniform dentine ridges with an average density of 6 per mm. Over the greater part of the shield, these are grouped into areas which become progressively more scale-like towards the posterior of the shield; an elevated ridge occupies a median position within each group. As on the dorsal shield, the most posterior scale-like areas have an imbricated appearance; this is best shown in NMC 21637, where the fused scales are approxi- mately 5 mm long and 6 mm wide and are separated from an area of less scale-like ornamentation by a narrow band of ridges and tubercles (text-fig. 4). An isolated scale, NMC 21639 (PI. 80, fig. 4), which resembles the more posterior scale-like units of the dorsal and ventral shields, is also referred to this species. The scale, which is approximately 4 mm long and 6 mm wide, is asymmetrical. Its orna- mentation is of longitudinal dentine ridges, one being more elevated than the rest and extending beyond the posterior margin as a spur. It is not possible to determine the position of this scale on the body. Remarks. This material was provisionally identified as a new species of Ptomaspis Denison (Loeffler, in Jones and Dixon 1975), but more detailed examination indicates that it is better accommodated within the genus Tolypelepis Pander. Although the LOEFFLER AND JONES; SILURIAN OSTRACODERMS 669 ornamentation is finer and of lower relief, and the anterior scale-like groupings are less distinct than in the two established species {T. undukita Pander and T. lenzi Dineley and Loeffler), there are no features which exclude this species from Tolypelepis, as defined by Denison (1964). cf. Tolypelepis leopoldensis sp. nov. Material. Two incomplete ?ventral shields, NMC 21640-21641. Locality. Thirty metres above the base of the Leopold Formation, on the west side of the bay at Port Leopold, Somerset Island (text-fig. 1). Description. The two shields have very similar ornamentation to that developed in T. leopoldensis sp. nov., but they differ in shape, both from one another and from the three ventral shields which are referred to the latter species. NMC 21640 is a ?ventral shield approximately 29 mm long and 19 mm wide; its lateral margins are concave, such that the shield is narrowest some 7-8 mm behind the anterior margin, the latter being transverse but for a shallow median concavity. The poorly preserved ornamenta- tion comprises short, relatively narrow (6/mm), dentine ridges which are not of uniform height; they are locally grouped into scale-like areas. The larger, but less complete, plate (NMC 21641) has the same sort of ornamentation, but its lateral margins are more deeply indented than those of NMC 21640, and its anterior margin is transverse with anterolateral notches. The plate is over 35 mm long and 29 mm wide, the border of short ridges and tubercles around the anterior and lateral margins suggesting that these are natural edges. Remarks. This material was originally referred, along with the species with which it is compared, to the genus Ptomaspis (Loeffler, in Jones and Dixon 1975). In view of the differences in shape of the two shields, and the similarity in ornamentation to T. leopoldensis sp. nov., they are considered best accommodated by use of open nomenclature. Family corvaspididae Dineley, 1953 Genus corvaspis Woodward, 1934 Corvaspis cf. C. arclica Loeffler and Dineley Plate 80, fig. 7 Material. Four incomplete median plates, NMC 21642-21645; an indeterminate fragment, NMC 21647; impression of plate fragment, NMC 21646. Locality. Thirty metres above tlie base of the Leopold Formation, on the west side of the bay at Port Leopold, Somerset Island (text-fig. 1). Description. Although varying in the extent of their preservation, all of these plate fragments bear similar ornamentation; this comprises short (average 2 mm), rela- tively coarse (3-4/mm) dentine ridges, grouped into areas which become scale-like at the posterior of the shield. The ridges are of uniform height on all but the most posterior and posterolateral parts of the plate, where the median ridge of each scale- like area is sharper crested than are the peripheral ridges. The best preserved of the plates, NMC 21642, is 48 mm long and 40 mm wide. 670 PALAEONTOLOGY, VOLUME 20 although the left side is apparently crushed. The anterior margin has a deep median notch, and the anterolateral corners are truncated. The over-all orientation of the dentine ridges on the plate is approximately longitudinal, with slight convergence on the mid-line towards the posterior, and stronger divergence around the median notch on the anterior margin. Over much of the area of the plate, ornamentation is of short ( 1 •5-2-5 mm) straight dentine ridges which are grouped into areas or ‘tesserae’ approximately 2 mm wide and 4 mm long (text-fig. 5). Towards the posterior and posterolateral margins of the plate, the tesserae take on a more scale-like appearance and, within each, the median ridge is more sharply crested than the peripheral ridges. At the posterior margin of the plate, these scale-like units are up to 5 mm wide and have complex ornamentation, comprising short ridges anteriorly and longer ridges posteriorly. The anterior, anterolateral, and much of the lateral margin of the shield is bordered by a narrow band (0-5-T0 mm) of tiny tubercles (text-fig. 5). Other plate fragments, being less complete, show correspondingly less detail of the tuberculated border and of the scale-like areas. In NMC 21643, the scale-like areas are well developed at the posterolateral extremity of the plate, but are separated from areas of more typical ornamentation by an irregular band of short ridges. In NMC TEXT-FIG. 5. Corvaspis cf. C. arctica Loeffler and Dineley. Median plate (NMC 21642) showing variation in ornamentation. Plan X 1, detail x6. LOEFFLER AND JONES: SILURIAN OSTRACODERMS 671 21644, the dentine ridges are commonly contorted in the region of the lateral line sensory pores (text-fig. 6). The more peripheral ridges of individual tesserae on the front of the shield in both NMC 21643 and 21644 are curved around the median ridge. Remarks. This material is referred to Corvavpw Woodward because its ornamentation comprises short dentine ridges which are grouped into tesserae. Although originally (Loeffler, in Jones and Dixon 1975) compared with the type species, C. kingi Woodward, it is closer to the recently established C. arctica Loeffler and Dineley (1976) by virtue of the presence of scale-like areas towards the posterior of the shield. It does differ from C. arctica, however, in at least two respects : its dentine ridges are, on average, slightly coarser (3-4/mm as opposed to 4-5/mm) and its scale-like areas each have a sharp-crested median ridge. The importance of these differences is difficult to assess, as C. arctica is known only from dorsal shields. There is also a marked similarity between this material and that which has been referred to T. leopoldensis sp. nov. The main differences are in the coarseness of the dentine ridges and in the distinctness of the tesserae in Corvaspis, also in the restric- tion of the sharper-crested ridges to within the most posterior scale-like areas. TEXT-FIG. 6. Corvaspis cf. C. arctica Loeffler and Dineley. Median plate (NMC 21644) showing variation in ornamentation. Plan x 1-5, detail x6. //p— lateral line sensory pore. 672 PALAEONTOLOGY, VOLUME 20 It has been suggested elsewhere (Loeffler and Dineley 1976) that Corvaspis is related to the primitive cyathaspidids ; this may represent an intermediate form, but its exact status remains uncertain without knowledge of the morphology of the dorsal shield, particularly of the form of the orbital region. Family tesseraspididae Berg, 1955 1 Kallostrakon sp. indet. Plate 80, figs. 1, 2 Material. A plate fragment, NMC 21648. Locality. Thirty metres above the base of the Leopold Formation, on the west side of the bay at Port Leopold, Somerset Island (text-fig. 1). Description. The plate fragment, which is 34 mm long and 17 mm wide, has an orna- mentation of rather irregular, bulbous, ridges with minutely serrated lateral margins; in some areas, these are closely spaced, but in others are interspersed with narrower ridges. The over-all pattern of ridges is longitudinal, with slight convergence both anteriorly and posteriorly. Remarks. This specimen is questioningly referred to Kallostrakon Lankester because of its ornamentation, which is similar to that of fragmentary material which has been placed in that genus by Tarlo (1964, 1965). It must be pointed out, however, that the shape of the tubercles and their separation by narrower ridges resembles the condition in certain traquairaspidids (Dineley and Loeffler 1976). SIGNIFICANCE OF THE VERTEBRATE FAUNA Geological investigations on Somerset Island and neighbouring Prince of Wales Island, by the Geological Survey of Canada and by members of the geology depart- ments of the universities of Ottawa (Canada) and Bristol (England), have yielded extensive collections of ostracoderms from various stratigraphic levels. The col- lections from the Peel Sound Formation are well documented (Thorsteinsson and Tozer 1963; Dineley 1965a, 1965Z>, 1966a, 1966/), 1968; Broad and Dineley 1973; Broad 1973; Broad, Dineley, and Miall 1968; Loeffler and Dineley 1976), but ostraco- derms have also been recorded from the underlying Read Bay Formation (Dineley 1965a, 1965/), 1966a, 1966/); Broad 1973; Broad and Dineley 1973; Jones 1974; Jones and Dixon, in press) and from the ‘transitional beds’ (now referred to the Cape Storm Formation, Reinson et al. 1976) between the Read Bay and the Allen Bay Formations. (Turner and Dixon 1971; Dixon et al. 1972.) While it was initially supposed that these ostracoderm faunas would facilitate correlation and dating, the situation in the Canadian arctic has proved rather complex because the area appears to have been an evolutionary centre for hetero- stracan ostracoderms during the Silurian (Dineley 1973; Broad 1973; Dineley and Loeffler 1976) ; as a consequence, the same genera have different age ranges in Europe and in northern Canada, The genus Corvaspis is, for example, known only from the latest Downtonian {sensu White 1950) and the Dittonian in Europe, but in arctic Canada it occurs in strata of pre- or early Downtonian age (the Pridolian Stage being LOEFFLER AND JONES: SILURIAN OSTRACODERMS 673 accepted as equivalent to the lower part of the Downtonian, below the Traquairaspis zones). It is important, therefore, to establish the ranges of particular genera and species within the Canadian arctic, in order to permit their use for dating and correlation on a local basis and to appreciate the pattern of ostracoderm distribution in space and time. To these ends, an ostracoderm fauna which can be dated from the associated microfauna is of particular interest. CONCLUSIONS This ostracoderm fauna, comprising Tolypelepis leopoldensis sp. nov., cf. T. leopoldensis, Corvaspis cf. C. arctica Loeffler and Dineley, and IKallostrakon sp. indet., is dated as late Ludlovian or Pridolian on the basis of the associated ostracods and conodonts. Together with evidence outlined by Jones and Dixon (1975) this suggests a Late Ludlovian/Pridolian age for the Leopold Formation. The lithology of the ostracoderm horizon suggests deposition in intertidal condi- tions, but this may not have been the environment in which the ostracoderms lived. The plates are dissociated and, although not appreciably abraded or broken, eould have been transported over quite large distances while still attached to a buoyant corpse. Acknowledgements. The field-work and research were supported by funds from the National Research Council of Canada (Grant Number A-5121) and the Department of Indian Affairs and Northern Develop- ment (Jones), and from the National Museum of Natural Sciences and the Natural Environment Research Council (Loeffler). Assistance and logistic aid at Resolute, Cornwallis Island, was provided by the Polar Continental Shelf Project. Thanks are extended to Drs. T. T. Uyeno and M. J. Copeland, of the Geological Survey of Canada, for their identifications of the conodonts and ostracods, and to Professor H. B. Whittington of the University of Cambridge (England) for the use of facilities in the geology department (Loeffler). The photographic illustrations are the work of R. Godwin of the University of Bristol, England. REFERENCES BATHURST, R. G. c. 1971. Carbonate sediments and their diagenesis. Dev. Sedimentol. 12, 620 pp. BROAD, D. s. 1973. Amphiaspidiformes (Heterostraci) from the Silurian of the Canadian Arctic Archipelago. Bull. geol. Surv. Can. 222, 35-50. and DINELEY, D. L. 1973. Torpedaspis, a new Upper Silurian and Lower Devonian genus of Cyatha- spididae (Ostracodermi) from Arctic Canada. Ibid. 53-90. DINELEY, D. L. and MiALL, A. D. 1968. The Peel Sound Formation (Devonian) of Prince of Wales and adjacent islands; a preliminary report. Arctic, 21, 84-91. DENISON, R. H. 1964. The Cyathaspididae: a family of Silurian and Devonian jawless vertebrates. Fieldiana, Geol. 13, 309-473. DINELEY, D. L. 1965«. Notes on the scientific results of the University of Ottawa expedition to Somerset Island, 1964. Arctic, 18, 55-57. 19656. Demonstration: ostracoderms from the Siluro-Devonian of Somerset Island. Proc. geol. Soc. 1624, 97-98. 1966a. Fossil vertebrates from the Read Bay and Peel Sound Formations, Somerset Island, District of Franklin. Pap. geol. Surv. Can. 66-1, 12-13. 19666. Geological studies in Somerset Island, University of Ottawa expedition 1965. Arctic, 19, 270-277. 674 PALAEONTOLOGY, VOLUME 20 DINELEY, D. L. 1968. Osteostraci from Somerset Island. Bull. geol. Surv. Can. 165, 49-63. 1973. The fortunes of the early vertebrates. Geology, 5, 2-20. and LOEFFLER, E. J. 1976. The ostracoderm fauna of the Delorme Formation and associated Siluro- Devonian strata in the District of Mackenzie, North West Territories, Canada. Spec. Pap. Palaeontology, 18, iv+214 pp., 33 pis. DIXON, j., WILLIAMS, R, and TURNER, s. 1972. Stratigraphical setting of the Silurian thelodonts from Prince of Wales Island, Northwest Territories. Lethaia, 5, 281-282. JONES, B. 1974. Facies and faunal aspects of the Silurian Read Bay Formation of Northern Somerset Island, District of Franklin, Canada. Unpublished Ph.D. thesis, University of Ottawa, Canada. 448 pp. and DIXON, o. a. 1975. The Leopold Formation; an Upper Silurian intertidal/supratidal carbonate succession on northeastern Somerset Island, Arctic Canada. Can. J. Earth Sci. 12, 395-41 1. and DIXON, o. a. In press. Stratigraphy and sedimentology of Upper Silurian rock. Northern Somerset Island, Arctic Canada. Can. J. Earth Sci. KLAPPER, G. and MURPHY, M. A. 1 974. Silurian-Lower Devonian conodont sequence in the Roberts Mountain Formation of central Nevada. Univ. Cal. Publns Geol. Sci. 3, 62 pp. LOEFFLER, E. J. and DINELEY, D. L. 1976. A ncw specics of Corvaspis from the Peel Sound Formation on Somerset Island. Palaeontology, 19, 757-766. and JONES, b. 1976. An ostracoderm fauna from the Leopold Formation (Silurian to Devonian) of Somerset Island, North-west Territories, Canada. Palaeontology, 19, 1-15. REINSON, G. E., KERR, J. w. and STEWART, w. D. 1976. Stratigraphic field studies, Somerset Island, District of Franklin (58B, C, D, E, F). Pap. geol. Surv. Can. 76-lA, 497-499. TARLO, L. B. 1964. Psammosteiformes (Agnatha). A review with descriptions of new material from the Lower Devonian of Poland. 1. General part. Palaeont. pol. 13, 1-135. 1965. Psammosteiformes (Agnatha). A review with descriptions of new material from the Lower Devonian of Poland. 2. Systematic part. Palaeont. pol. 15, 1-168. THORSTEiNSSON, R. and TOZER, w. 1963. Geology of northern Prince of Wales Island and northwestern Somerset Island. In fortier et al. Geology of the North Central part of the Arctic Archipelago. Mem. geol. Surv. Can. 320, 1-671. turner, s. and dixon, j. 1971. Lower Silurian thelodonts from the Transition Beds of Prince of Wales Island, Northwest Territories. Lethaia, 4, 385-392. WHITE, E. I. 1950. Vertebrate faunas of the Lower Old Red Sandstone of the Welsh borders. Bull. Br. Mus. nat. Hist. (Geol.), 1, 51-67. E. J. LOEFFLER Department of Geology University of Bristol Bristol BS8 ITR B. JONES Department of Geology University of Calgary Calgary Alberta Canada T2N 1N4 Typescript received 9 June 1976 THE JURASSIC AMMONITE BREDYIA BUCKMAN by J. R. SENIOR Abstract. The lower Aalenian (Middle Jurassic) ammonite Bredyia subinsignis (Oppel, 1856) has been investigated at several growth stages and found to be dimorphic. Burtonia crassornata Buckman (1910o), the type species of Bredyia Buckman ( 1 9 1 Oft), is regarded as a junior synonym of Ammonites subinsignis Oppel ( 1 856) as are Hammatoceras newtoni Buckman (1892), H. feugeurollense Brasil (1893), and several species described by Dumortier (1874). The lower Aalenian genus Bredyia belongs to the Hammatoceratinae, a subfamily of ammonites which, because of their comparative rarity, have not been studied in detail, although numerous references can be found in the literature. In the Aalenian (Middle Jurassic) of Europe, the ammonite fauna is composed predominantly of leioceratinids, on which the present system of zonation is largely based (Arkell 1956, p. 10); this zonation is under review as a result of fresh field information. In addition to leioceratinids, smaller numbers of tmetoceratinids, lytoceratids, and hammatoceratinids occur, and in areas of Tethyan influence phylloceratids also often constitute a large percentage of the ammonite fauna (text-fig. 1). Some hammatoceratinids are important since they are probably directly ancestral to two prolific ammonite groups in the Jurassic, the Sonniniidae, and the Stephano- cerataceae (Arkell 1957, p. L287), and are also probably indirectly ancestral to a third group, the Perisphinctaceae (Spath 1931, p. 279; Arkell 1957, p. L308; Sturani 1971, p. 1 53). Bredyia apparently remained a minor and obscure element in Lower Aalenian faunas. SYSTEMATIC PALAEONTOLOGY Family phymatoceratidae Hyatt, 1867 Subfamily hammatoceratinae Buckman, 1887 The Phymatoceratidae have been divided into two subfamilies (Arkell 1957, pp. L265 and L267; ICZN opinion 575, 1959), the ancestral Phymatoceratinae and the Hammatoceratinae. The former is restricted to the Toarcian, but the latter ranges from the Upper Toarcian to the Lower Bajocian. Before 1960 little had been written about the keeled members of the Hammatoceratinae, but since then several authors have figured and described faunas containing them. In describing ammonite faunas from the Bassin Rhodanien, Elmi ( 1 963 ) used much of the generic nomenclature erected by Buckman (1919-1 928) for the keeled hammatoceratinids and also described a new genus, Pseudammatoeeras and a new subgenus Rhodanieeras. Geczy (1966), however, working independently on faunas from the Mount Bakony area of Hungary, recognized only two genera within the Hammatoceratinae, Euaptetoeeras and [Palaeontology, Vol. 20, Part 3, 1977, pp. 675-693, pis. 81-84.] N 676 PALAEONTOLOGY, VOLUME 20 SCISSUM ZONE 1 LEIOCERATINAE HAMMATOCERATINAE I TMETOCERATINAE LYTOCERATIDAE PHYLLOCERATIDAE ! TOTAL NUMBERS Burton Cliff, Dorset 70. 19"/* (73) 11.53% (12) 14.42% (15) 3,85% (4) 0% (0 ) 104 Bonscombe Hill, near Shipton 76 47% 9 80% 9 80% 3.92% OV. 51 Gorge, Dorset (39) (5) (5) (2) (0) Truyas, near Digne, 40. 28% 6 94% 0% 4.17% 48.61V. 72 Basses Alpes, France (29) (5) (0) (3) (35) Wochenberg, near Balingen, 96 80% 0% 3.19% 0% 0% 94 W(jr ttemberg, Germany (91) (0) (3) (0) (0) OPALINUM ZONE Burton Cliff, Dorset 9 5 58% (238) 0.81% (2) 0.04% (1) 2.03% (5) 0% (0) 24 6 Green Hill, Innesacre Farm, 97.01% 1 49% 0% 1 . 49% 0% 67 near Bridport, Dorset (6 5) (1) (0) (1) (0) Road cutting, Severals, 98 86% 0% 0% 1.14% OV. near Crewkerne. Somerset (8 7) (0) (0) (1) (0) 88 Heiningen, near Goppingen. 92 .11% 0% 0% 7.89 V. 0% 342 WUrttemberg, Germany (31 5) (0) (0) (27) (0) TEXT-FIG. 1. Analysis of cephalopod faunas from the Aalenian of Europe. Hammatoceras, the latter a genus which Arkell (1957, p. L267) considered to be confined to the Toarcian. In reviewing the work of Elmi and Geczy as well as other literature, Westermann (1969, pp. 63-72) could not . . arrive at any definite opinion regarding the classification of many of the early and intermediate Hammatocera- tinae . . but concluded that \ . . taxonomic levels somewhere midway between the ones reviewed are strongly suggested, similar to the treatment in the Treatise . . I endorse this moderate view of the suprageneric status of the Hammatoceratinae. Abbreviations. B— Brigadier G. Bomford Collection (private collection). BM— British Museum (Natural History). GSM— Geological Survey Museum, London. LY —Collection of the University of Lyon, Lrance. MU— University Palaeontological Collection, Munich, West Germany. MM— Manchester Museum. OUM— Oxford University Museum. SH— Department of Geology Collection, University of Sheffield. M— macroconch, m— microconch. EXPLANATION OF PLATE 81 Bredyia subinsignis (Oppel) [M]. Pigs. 1, 2. The holotype of Bredyia crassornata (Buckman), from the Scissum Beds of Burton Bradstock (probably Burton Cliff), Dorset. Pigured by Buckman (1910a, pi. 9, fig. 1) as Burtonia crassornata. MM L11221 (Buckman Collection), xO-44. Pigs. 3, 4. The paratype of Bredyia crassornata (Buckman), from the same locality and horizon as figs. 1, 2. Pigured by Buckman (1925, pi. DLXXXII). GSM 47763 (Buckman Collection), xO-5. PLATE 81 SENIOR, Bredyia from the Jurassic of Dorset 678 PALAEONTOLOGY, VOLUME 20 TEXT-FIG. 2. Illustrating the ontogeny of Bredyia subinsignis (Oppel). a-k, B. suhinsignis (Oppel) [M]. fl, BM C78467, Scissum Zone, Bonscombe Hill, near Shipton Gorge, Dorset. xO-5. b, GSM 47763, paratype of B. crassornata (S. Buckman), Scissum Bed, Burton Bradstock, Dorset. xO-5. c, BM C78462, Scissum Zone, Burton Cliff, Dorset. xO-5. d, GSM Zxl402, Scissum Zone, Coder’s Cross, near Bridport, Dorset. xO-5. e, BM C78466, Scissum Zone, Bonscombe Hill, Shipton Gorge, Dorset, x 0 5./ and g, figured by Dumortier (1874, pi. 53, figs. 1-4) as Ammonites insignis Zieten. From La Verpilliere, Isere, France. LY 91 12 and LY 9118 respectively, x 0-5. /;, Munich ASVIII 76, lectotype of A. subinsignis Oppel, Torulosus Schichten, Gomaringen, near Tubingen, Germany. xO-5. /, LY 9110, holotype of A. alleoni Dumortier (1874, pi. 52, figs. 3, 4), La Verpilliere, Isere, France. xO-5. / nucleus showing nepionic con- striction and k, protoconch of BM C78465, Scissum Zone, Bonscombe Hill, near Shipton Gorge, Dorset. Both x 14. /, BM C78469 (author’s collection), Hammatoceras insigne (Zieten), Upper Toarcian, Leckhampton Hill, near Cheltenham, Gloucestershire. xO-5. m, LY 9181, H. insigne (Zieten), figured by Dumortier (1874, pi. 54, figs. 4, 5), Upper Toarcian, Saint Nizier, Loire, France, x 0-5. «-5, B. subinsignis (Oppel) [m]. n, BM C78461, Scissum Beds, Burton Cliff, Dorset. X 1.0, GSM 1 160HW, Northampton Ironstones, New Duston, near Northampton, x \ .pandq, BM C78457 and GSM 3666 respectively, Scissum Beds, Burton Cliff, Dorset, x 1 . r, BM C77995, Northampton Sands, New Duston, near Northampton, xl. .s, BM C78458, Scissum Beds, Burton Cliff, Dorset, x 3. SENIOR: THE JURASSIC AMMONITE BREDYIA 679 Genus bredyia Buckman, 1910 (Synonym Pseudammatoceras E\mi, 1963) Type species. Burtonia crassornata Buckman, 1910 (= Ammonites subinsignis Oppel, 1856). Diagnosis. Hammatoceratinid with a massive macroconch which has a small keel and coarse nodate or tuberculate bifurcate ribbing on juvenile whorls, tending to be smooth on the last whorl of the mature shell. Moderately evolute with marked uncoiling of umbilical seam towards maturity. Sutures relatively simple even at larger diameters ; the retraction of the umbilical lobe is not marked. Mature apertures are simple and collared. Microconch comparatively small also coarse nodate or tuberculate ribbing continuous up to a mature aperture, which is completed by midlateral lappets. Moderately evolute with no marked excentricity of the umbilical seam towards maturity. Sutures very simple. Remarks. Although Bredyia is as robust as the ancestral Hammatoceras (text-fig. 2c), the whorl sections are more massive and subquadrate in appearance, only becoming slightly more inflated at maturity in the macroconch; Bredyia [M] is larger and more robust than the macroconchs of the Upper Aalenian genera Planammatoceras and Eudmetoceras. Ornamentation in Bredyia is also distinctive. In Hammatoceras the nodate or tuberculate part of the coarse-ribbed ornament (formed where the ribs bifurcate) is very close to the umbilical seam, whereas in Bredyia appreciably more of the primaries are seen. At the venter, the secondaries abut almost at right angles to the keel in Hammatoceras, but in Bredyia the ribs have a definite oral direction at the venter. Bredyia differs from the contemporary Erycites which has only a rudimentary keel. TEXT-FIG. 3. Hammatoceratinid sutures from the Upper Toarcian, Aalenian and Lower Bajocian, all x 0-5. a, paratype of Bredyia (Buckman) (GSM 47763), suture at 1 10 mm diameter. Scissum Zone, Lower Aalenian. b, holotype of B. crassornata (Buckman) (MM LI 1221), suture at 142 mm diameter. Scissum Zone, Lower Aalenian. c, B. subinsignis (Oppel) (OUM J 162 18), suture at c. 190 mm diameter. Opalinum Zone, Lower Aalenian. d, Hammatoceras insignis{Z\Q\.Qr\) {MM LI 1 290), suture at c. 94 mm diameter. Upper Toarcian. e, holotype of Eudmetoceras amplectens (Buckman) (MM LI 1287), suture at 168-5 mm diameter. Discites Subzone, Lower Bajocian. /, sieboldi (Branco) (Bayer Coll. H20), suture at 69 mm diameter. Murchisonae Zone, Aalenian. 680 PALAEONTOLOGY, VOLUME 20 or no keel at all, with ribs which may continue over the venter and a sutural pattern which is very different with a very shallow ventral lobe and first lateral saddle. The degree of simplicity seen in the sutures of Bredyia distinguish it from most hammatoceratinids (text-fig. 3) on sutural evidence alone and only the skeletal nature of the second lateral lobe can be used to confirm that this is a hammatoceratinid. In the microconch, because of the small sizes attained at maturity, the sutural appearance is not significantly diagnostic at a generic level. Distribution. Opalinum Zone in many parts of Europe (text-fig. 4), and more commonly in the Scissum Zone, especially in England. Bredyia has also been reported by Westermann (1964, p. 359) from the upper Murchisonae Zone of Beaminster, Dorset, England. However, very extensive collecting at this locality and other localities with exposures of similar stratigraphical horizons has yielded no specimens of Bredyia. TEXT-FIG. 4. The distribution of Bredyia subinsignis (Oppel). EXPLANATION OF PLATE 82 Bredyia subinsignis (Oppel) [M] Fig. 1. A complete macroconch showing slight constriction of the aperture on the mature bodychamber. From Bed 22 (Scissum Bed) of Bonscombe Hill, near Shipton Gorge, Dorset. The reverse half of the specimen was eroded before subsequent deposition of Bajocian (Garantiana Zone) sediments. BM C78467 (author’s collection), xO-5. Figs. 2, 3. A septate nucleus from the Scissum Bed of Bradford Abbas, Dorset. BM C77992 (Buckman Collection), xl. Fig. 4, The impression of ventral siphuncular attachment scars on the holotype of Bredyia crassornata (Buckman), as c. 114 mm diameter. MM LI 1221 (Buckman Collection), x T5. Fig. 5. Dorsal wrinkle layer at 71 2 mm diameter on the specimen BM C78465 (author’s collection), locality and horizon as fig. 1, x 8-6. PLATE 82 SENIOR, Bredyia from the Jurassic of Dorset 682 PALAEONTOLOGY, VOLUME 20 Bredyia suhinsignis (Oppel, 1856) *1856 Ammonites subinsignis', Oppel, p. 367 [M], 71874 Ammonites alleoni', Dumortier, p. 259, pi. 52, figs. 3, 4 [M]. 71874 Ammonites subinsignis Oppel; Dumortier, p. 261, pi. 53, figs. 1, 2 [M]. V. 1883 Harpoceras insigne Schiibler; Wright, p. 453, pi. LXXV, figs. 1-3 [M]. 71892 Hammatoceras newtoni; Buckman, p. 259. 1893 Ammonites feugeurollense', Brasil, p. 39, pi. 5, figs. 1, 2 [M]. 1904 Hammatoceras dumortieri; Prinz, p. 74. 1905 Hammatoceras subinsignis (Oppel); Benecke, p. 331, pi. XXXII, fig. 2 [M]. V. 1910a Burtonia crassornata; Buckman, p. 97, pi. 9, fig. 1 ; pi. 10, fig. 1 [Mj. 19106 Bredyia crassornata (Buckman); p. xciv [M]. V. 1925 Bredyia crassornata (Buckman), pi. DLXXVII [M]. 1925 Hammatoceras subinsignis (Oppel); Renz, pi. 10; pi. 1, fig. 5 [M]. 1962 Hammatoceras alleoni Dumortier; Migacheva, p. 82, pi. 8, figs. 1, 3 [M]. 1962 Hammatoceras subinsignis Oppel; Migacheva, p. 82, pi. 8, fig. 8 [M]. 1963 Pseudammatoceras subinsignis (Oppel); Elmi, p. 13, pi. I, figs. 1, 2 [M]. 71963 Parammatoceras alleoni (Dumortier); Elmi, p. 55, pi. VIII, fig. 1. 1963 Parammatoceras suballeoni Elmi; p. 57, pi. VIII, fig. 4 [M]. 1963 Pseudammatoceras feugeurollense (Brasil); Elmi, p. 93 [M]. 1964 Bredyia newtoni (Buckman); Westermann, p. 359 [m]. Type material. Although described in 1856 by Oppel, this species was not figured until 1925 when Renz redescribed it in an attempt to stabilize the species. The specimen Renz figured (1925, pi. 1, fig. 5) is the only remaining example in Oppel’s Collection (Dr. G. Schairer in litt) and is here selected as lectotype of the species. The lectotype is from the Torulosus Schichten (= Opalinum Zone) of Gomaringen, Wiirttemberg, South West Germany and is deposited in the University Palaeontological Collection, Munich (MU ASV11176). Diagnosis. As for the genus. Stratigraphical and geographical distribution. As for the genus. Other material. During this study 76 examples of this species were examined (42 macroconchs and 34 microconchs), all are from English sources, unless otherwise stated. OPALINUM ZONE Macroconchs. Burton Cliff, Burton Bradstock, Dorset, bed 8a of Richardson (1928, p. 63), BM C78456 (author’s coll.), B 1902, B 2078, B 4164, B 4596, B 7476. Haresfield Hill, Gloucestershire, BM C9216 (S. Buckman Coll.), OUM J16218; Erocester Hill, near Stroud, Gloucestershire, BM 67903 (Etheridge Coll.). La Verpilliere, Isere, France, LY 9110 (holotype of Ammonites alleoni, Dumortier Coll.). Microconchs. BM C77972-77975, BM C77977, BM C77982-77983 (Buckman Coll.), B 2079, B 2139, B 4580. Sand- stone below Scissum Bed, Green Hill, Innesacre Farm, near Bridport, Dorset, BM C78463 (author’s coll.). SCISSUM ZONE Macroconchs. Burton Bradstock (probably Burton Cliff), Dorset, MM LI 121 and GSM 47763 (holotype and paratype of Bredvia crassornata, Buckman Coll.), GSM 72799 (Spath Coll.), BM 50642 (Morris Coll.), BM C10242 (Witchell Coll.), BM C77958 (Buckman Coll.). Scissum Bed (bed 7 of Richardson 1928, p. 63), Burton Cliff, Burton Bradstock, B 1885, B 3592, B 6057 ; BM C78462 (author’s coll ). Quarry Hill, Chideock, OUM J33812 (Walford Coll.). Bed 22 Bonscombe Hill, near Shipton Gorge, BM C78465-78467 (author’s coll., mentioned Senior et at. 1970, p. 1 16). Stony Head, Coders Cross, near Bridport, B 4856. Quarry north-east of Coders Cross (bed 2 of Bomford 1948, p. 148), near Bridport, B 2474-2475, SH 55104 (Bomford Coll.), GSM ZK1401-1402 (Bomford Coll.). Gribbs Quarry, Vinney (‘Vetney’) Cross, near Bridport, BM C77989 (S. Buckman Coll.). Upton Farm section, Matravers, near Bridport, GSM 72800-72801 (Spath Coll.), BM C78468 (author’s coll.), bed 2 of the same locality (mentioned Senior et al. 1970, p. 118). Broad Windsor, GSM 3307 (Sharpe Coll.). Bradford Abbas, BM C77991-77992 (Buckman Coll ). Marston Road Quarry, near Sherborne, BM C77990 (Buckman Coll.). Crewkerne Station Quarry (more probably the Crewkerne Railway SENIOR: THE JURASSIC AMMONITE BREDYIA 683 Cutting), BM C77993 (Buckman Coll.). Hampton, Somerset, BM C6218 (Slatter Coll.). Newmarket, Nailsworth, Gloucestershire, GSM 22813 (Lycett Coll.). Ravensgate Hill, near Cheltenham, GSM 25101 (Lycett Coll.). Leckhampton, near Cheltenham, GSM Y3444 (Hudleston Coll ). Oatley (‘Otley’) Hill, near Hook Norton, Oxford- shire, GSM Z3881 (Richardson Coll ), OUM J33628-33630 (Beesley Coll.), OUM J33646, Whichford Hill, near Hook Norton, OUM J33647 (Walford Coll.). Duston, near Northampton, GSM Y3345 (Hudleston Coll.), BM C77513. Billing Road, near Northampton, BM C77515. Microconchs. Burton Cliff, Dorset (Scissum Bed, bed 7 of Richardson 1928, p. 63), BM C78457-78458, BM C78461, BM C78459-78460 ; BM C78462 (author’s coll.) ; BM C77969-77970, BM C7798 1 , BM C77997, GSM 3666 ( Buckman Coll.); B 4563, B 6062. Scissum Bed, Green Hill, Innesacre Earm, near Bridport, BM C78463 (author's coll.). Sherborne (?Sandford Lane), GSM 69945 (S. Buckman, ex. J. Buckman Coll.); near Stroud, Gloucestershire, BM C10233 (Witchell Coll.); Wedford, BM C10333 (Witchell Coll.); Duston, near Northampton, GSM Y3346-3347 (Hudleston Coll.); GSM 1 160 HW (Woodward Coll.); New Duston, near Northampton, BM C77994-779945 (Buckman Coll.); and Gayton, near Northampton, GSM h378 (Judd Coll.). Description. Protoconchs in both forms are smooth and globular (dimension given in text-fig. 5), but none shows any apparatus other than a subcircular caecal bulb. Shallow nepionic constrictions occur approximately one whorl forward of the proseptum (between 0-80 and 109 mm diameter in the sample seen) and these have the form of a shallow sigmoidal groove on the internal mould (text-fig. 2). After the nepionic constriction the second growth stage occurs (cf. Currie 1944, pp. 192-194) and is marked by the formation of rounded whorl sections by 6 mm diameter in the macroconch and slightly earlier in the microconch. Early development of a sub- quadrate whorl profile in the microconch coincides with the first appearance of the ribbed ornament and a small keel (text-fig. 5). Although ribbing and the keel appear later in the ontogeny of the macroconch by 10 mm diameter both have very similar subquadrate whorl sections (text-fig. 2n, s). With increasing diameter the macroconch whorl profile progressively changes due to slight ventro-lateral compression and MAC RO CONCH MICROCONCH Pro toconc h dimensions ( m millimetres ) fn 0.500 diameter m 0.536 width (2) m 0.380 diameter m 0.540 width tAJ Position of nepionic constriction 170* alter prosuture ( 1 ) laOMOO* alter prosuture (3 ) Diameter at which the nepionic constriction occurs 1.08 mm . ( 1 ) 0.80 - 1.09mm ( 3) First appearance of ribbed ornament 5-6mm. diameter ( 3 ) 4 -5mm. diameter (4 ) Range of mature phragmocone d iameters c 1 64 - 203 mm. ( 7 ) c 2 3 - 2 7mm. (6 ) Mean mature conch diameters m 24 3. 3 7mm. < 7) rh 37,96mm, (6) Shell volutions c 7.6 ( 7 > c 4.5 - 5 ( 4 ) Bodychamber length in all growth stages seen rh 221.5* (20) m 21 5.9* (15) TEXT-FIG. 5. A comparison of macroconch and microconch data in Bredyia subinsignis (Oppel). 684 PALAEONTOLOGY, VOLUME 20 increasing prominence of the coarse-ribbed ornament. The resulting subtriangular or subquadrate sections are retained throughout the juvenile stage, up to about 90 mm diameter (PI. 84, figs. 3, 4 and text-fig. 2b), after which a mature macroconch growth stage can be recognized when the whorl section becomes slightly inflated and fastigate with only a small keel (text-fig. 2a~e). Although subquadrate whorl sections appear earlier in the microconch (at about 5 mm diameter) little further development of the whorl shape occurs and except for moderate increases in dimensions the profile remains the same up to the mature aperture. This profile is also accentuated by the early development of coarse falcoid ribbing which is tuberculate or nodate where the ribs bifurcate on the lower lateral portion of the whorl flanks (PL 84, figs. 9, 13). This strong ornament is supplemented throughout growth by fine falcoid growth lines. Nodate or tuberculate ribbing with growth lines is also a prominent feature of the macroconch (PI. 83, figs. 1, 6) and may give an angular appearance to the whorl section (text-fig. 2e). After about 90 mm diameter, however, the ribbing gradually fades finally leaving the mature body- chamber ornamented only by surface lirae (PI. 82, fig. 1). Each form of Bredyia subinsignis has almost the same number of ribs per whorl, varying with the ontogeny from 5 to 28, although the average for both forms is slightly different, microconch 17-34 per whorl (42 in sample), microconch 18-72 per whorl (34 in sample). Both sexes in subinsignis show the usual features indicative of maturity. Changes in ornament and slight inflation of the fastigate whorl section after about 90 mm diameter in the macroconch are also accompanied by uncoiling of the umbilical seam (PI. 81, fig. 4; PI. 82, fig. 1); this occurs about one complete whorl (360°) before the mature aperture which is simple, falcoid, and collared (PI. 82, fig. 1). Features indicative of maturity in the microconch are not as prominent. Ornamentation remains virtually the same until the final aperture and growth is almost linear, although the microconch is generally more evolute than the macroconch (compare PI. 84, figs. 6, 9). The mature aperture is distinctive with the development of midlateral lappets and a small rostrum (PI. 84, figs. 22, 24). The umbilicus in both forms is fairly large with small steep walls and is distinctly ornamented by the ribbing of previous immature whorls. All complete examples seen had half to three-quarters of a whorl of bodychamber (PI. 82, fig. 1 and PI. 83, fig. 1). During dissection of the material the complete sutural ontogeny of each form was recorded at half whorl intervals and is represented in text-fig. 6. The retraction of the umbilical lobe attributed to this genus by Buckman (1910a, p. 97) and later reiterated EXPLANATION OF PLATE 83 Bredyia subinsignis (Oppel) [M] Figs. 1, 2. A mature and almost complete macroconch from the Cotswold Sands (Opalinum Zone) of Haresheld Hill, Gloucestershire. OUM J16218, xO-5. Figs. 3, 4. The plastotype of Ammonites alleoni Dumortier (LY 9110), from the Opalinum Zone (?) of La Verpilliere, Isere, France. Figured by Dumortier (1874, pi. 52, figs. 3, 4), x 1. Figs. 5, 6. An unusual evolute immature macroconch from the Scissum Bed of Bradford Abbas, Dorset. BM C7791 (Buckman Collection), x 1. PLATE 83 W- ■■ SENIOR, Bredyia from the Jurassic of Dorset 686 PALAEONTOLOGY, VOLUME 20 TEXT-FIG. 6. The sutural ontogeny of Bredyia subinsignis (Oppel). a-l, macro- conch (BM C78465), from Bonscombe Hill, near Shipton Gorge, Dorset. A, prosuture at 0-48 mm diameter ( x 50). b, first suture at 0-50 mm diameter (x35). c, suture and nepionic constriction at 108 mm diameter (x35). D, 1 -56 mm diameter ( x 22-5). e, 2-88 mm diameter ( x 1 5). f, 2-84 mm diameter (x 11). G, 5-23 mm diameter (x 10). H, 7T2 mm diameter (x5). i, 1314 mm diameter ( x 3-75). J, 17T7 mm diameter (x 2-3). k, 47-8 mm diameter (x 0-7). L, 92-7 mm diameter ( x 0-4). m, the paratype of B. crassornata (S. Buckman), from Burton Bradstock, Dorset (GSM 47763). Suture at c. 110 mm diameter ( x 0-25). N, BM C78467, same locality and horizon as a-l. Suture at c. 203 mm diameter ( x 0-2). a-g, BM C78463, microconch, from Green Hill, Innesacre Farm, near Bridport, Dorset, a, prosuture at 0-40 mm diameter (x35). b, L36mmdiameter ( X 25). c, 2-80mmdiameter (x 21-5). d, 3-84 mm diameter ( X 6-25). e, 6-30 mm diameter ( x 3-25)./, 6-3 mm diameter ( x 1 -9). g, 27-9 mm diameter (xL7). h, BM C77515, macroconch from Billing Road, near Northampton, suture at 35 mm diameter ( X 2-5). i-k, microconchs from Burton Cliff, Dorset. /, GSM 3666, final approximated sutures at c. 25 mm diameter. J, BM C78457, suture at c. 26 mm diameter and k, BM C77997, suture at c. 23 mm diameter. All x 2-5. SENIOR: THE JURASSIC AMMONITE BREDYIA 687 by Arkell (1957, p. L267) was not found to be noticeable. The sutural ontogeny of both sexes are very similar, especially in the early juvenile stages (text-fig. 6) although in late stages the development of the sutures in the much larger macroconch is naturally more pronounced. However, the relative simplicity of the macroconch sutures, even at the maximum of their development (about 90 mm diameter), is unusual and unlike that seen in other hammatoceratinids (text-fig. 3d, f). The crowd- ing and simplification of the final sutures in the mature examples of both sexes is a common feature in most mesozoic ammonites (text-fig. 6). Dorsal wrinkle-layer structures were seen at various dimensions on both forms (PI. 82, fig. 5) and showed great similarity with those described in the Graphoceratidae (Senior 1971). Siphuncular attachment scars sited parallel to the siphuncle tube, described by Neaverson (1927) and Holder (1973, p. 44) were also seen (PI. 82, fig. 4). Dimorphism. There can be little doubt that the two forms of Bredyia described above are conspecific dimorphs, especially since they are found in the same strata with Erycites being the only other hammatoceratinid present. The large differences in dimensions, especially in diameter, are a function of sexual dissimilarity only. The macroconch : microconch size ratio (6-4: 1) may be misleading, as the full size range of mature individuals (especially of the microconch) is uncertain due to a shortage of suitable material. It is, however, similar to the same ratio seen in Toarcian hammato- ceratinids (Dr. M. K. Howarth pers. comm.). Certainty the initial growth of both forms is almost identical, having protoconchs of similar shape and size (fext-fig. 5), equivalent placings of the nepionic constriction, and rapid development of rounded, then robust angular whorl sections (text-fig. 2). Graphical representation of the biometric data obtained from both forms also shows an identical relationship up to about 27 mm diameter (text-fig. 7). A direct comparison can be made between the microconch and macroconch with the whorl width/whorl height ratio; in the microconch the value of this ratio remains at above 1 00 throughout development, whereas in the macroconch, this value drops appreci- ably below 1 00 with the onset of maturity, after about 90 mm diameter. This change of ratio can also be correlated in the macroconch with the loss of the ribbed ornament and marked uncoiling of the umbilical seam. Similar parallel developments can be seen in other plotted ratios (text-fig. 7). Up to diameters of 27 mm there is very little to separate the sutural ontogeny of either form (text-fig. 6), although the sutures of the macroconch become more complex at a later stage, a function of the enormous difference in size (text-fig. 6k-n). The skeletal development of the second lateral saddle in the macroconch (text-fig. 6l) is of interest; this feature is not always visible in every specimen, as the acme of development seems to be reached at about 90 mm diameter and subsequent sutures become more simplified (text-fig. 6m-p). This skeletal appearance is common to most hammatoceratinids (text-fig. 3) and also the sonniniids, but the invariable absence of this feature at larger diameters makes it sometimes very difficult to distinguish the macroconch of B. suhinsignis from that of Ludwigia haugi Douville, the general morphology and sutural pattern being similar. This has possibly been one cause of misidentification, particularly the records of Bredyia from the Murchisonae Zone. Using the complete ontogeny of each macro- conch one can readily distinguish between both species. 688 PALAEONTOLOGY, VOLUME 20 TEXT-FIG. 7. Graphical representation of the ontogeny of Bredyia subinsignis (Oppel), • macroconch, ° microconch, O the lectotype of Ammonites subinsignis Oppel. Both axes are logarithmic and each plotted parameter or ratio on the vertical axis is offset by one cycle. SENIOR: THE JURASSIC AMMONITE BREDYIA 689 So far only two other groups of microconchs, Kialagvikes and Rhodaniceras, have been recognized in the hammatoceratinid ammonites. The subgenus Kialagvikes was described by Westermann (1964, p. 391) from a large sample of ammonites obtained from Wide Bay, Alaska and there are general similarities in size and appearance between Bredyia [m] and Kialagvikes, yet the general lack of nodate or tuberculate ornament (with the exception of K. spinosa) and the minute keel in the latter makes it distinctive, as does the more complex sutural appearance. The presence of identical lappets and a small rostrum in both microconchs is probably only a general characteristic of the subfamily Hammatoceratinae. Westermann ( 1 964, p. 392) drew attention to the fact that the macroconch subgenus Erycitoides is always associated with Kialagvikes and he assumed that they have a dimorphic relationship. As Westermann also noted hammatoceratinid microconchs bear a strong resemblance to certain microconch Graphoceratidae. However, con- sideration of the whole ontogeny allows discrimination. Bearing in mind this similarity between the microconchs of these subfamilies, it is unfortunate that Elmi (1963, p. 60) failed to illustrate the sutures of the microconch Rhodaniceras although he writes ‘La ligne cloisonnaire apparient au “type hammatoceratidien” . . .’, but it is not unreasonable that Rhodaniceras is the microconch form of Eudmetoceras, as indicated by Elmi (1963, p. 61). Discussion. One of the main problems involved in the understanding of this species, was the interpretation of the five trivial names available. In 1856 Oppel described a number of hammatoceratinids as Ammonites subinsignis, and because he never illustrated these some confusion resulted when later workers applied his nomenclature. The lectotype of this species is indifferently preserved, having a slightly contorted body- chamber (three-quarters of a whorl in length) with an entirely crushed and largely absent phragmocone (PI. 84, figs. 3, 4). The appearance of the whorl section and level of ribbed ornament development indicate this as an immature specimen. I examined a plaster cast of the specimen figured by Renz (1925, pi. 1, fig. 5), and there is little doubt that this immature example is comparable with the better-preserved ammonites later described by Buckman (1910n, p. 97) as Burtonia crassornata Buckman. This comparison is also endorsed by Oppel’s own account of the species (1856, p. 368) in which he recorded having found another example at Burton Bradstock, Dorset, the type area for crassornata. Before his description of Bredyia crassornata, Buckman (1892, p. 259) gave a very brief account of a small new hammatoceratinid from the Inferior Oolite of Northamptonshire. To this species Buckman gave the name Hammatoceras newtoni, but he failed to describe or figure this species adequately, even at a later date. It is difficult to recognize this species from Buckman’s description and no type material seems to be available, although the specimen figured by Wright (1883, pi. LXXV, figs. 1-3) is probably the one seen by Buckman and therefore should be regarded as the lectotype of newtoni. This species has often been quoted in the literature, especially from the Scissum Zone, but the interpretation of it has varied, the name having been used for immature or nucleii specimens of the macroconch B. crassornata ( = B. subinsignis) (e.g. Donovan 1954, p. 49) or for microconch hammatoceratinids (Westermann 1964, p. 359). Although the former interpretation is probably correct, there is a considerable degree of uncertainty attached to the use of this name. Two ammonites found at Feuguerolles-Sur-Orne and figured by Brasil (1893, pi. 5, figs. 1, 2) as H. feugeuroUense would also seem to be synonymous with subinsignis, but regrettably these specimens were destroyed in air raids on Caen in 1944. This hammatoceratid apparently only occurs rarely in the Opalinum Zone of the Normandy region (Dr. N. Rioutt in Hit.). In his classic work on the Jurassic palaeontology of the Rhone Basin, Dumortier (1874) figured several macroconchs which are possibly either synonymous with or closely related to B. subinsignis (Oppel). In the former category are A. alleoni Dumortier (1874, pi. LII, figs. 3, 4) and A. sub- insignis Oppel (1874, pi. LIII, figs. 1-4), later redescribed by Prinz (1904, p. 74) as H. dumortieri. Deter- mining the stratigraphical horizon of Dumortier's specimens is difficult because he cited all the material as having come from the ‘Zone de V Ammonites Opalinus', which encompasses not only the whole of the Aalenian but also the upper portion of the Toarcian. Elmi (1963) investigated the stratigraphical position 690 PALAEONTOLOGY, VOLUME 20 of Dumortier’s material and concluded that alleoni possibly came from the Murchisonae Zone and dumortieri originated very doubtfully from the Opalinum Zone (the horizon of origin being highly condensed, from Upper Toarcian-Lower Aalenian). Conclusions. A specimen from Oppel’s original collection figured by Renz (1925) is cited as the lectotype of B. subinsignis (Oppel). The type species of Bredyia, Burtonia crassornata Buckman (1910or) is considered a junior synonym of Oppel’s species as are H. newtoni Buckman (1892), H. feugeurollense Brasil (1893) and several species described and figured by Dumortier (1874); notably A. alleoni and A. subinsignis {= H. dumortieri Prinz, 1904). The synonymy of Bredyia with Hammatoceras sug- gested by Geczy (1966, p. 30) is not upheld as considerable morphological differences indicate a separate generic status and Pseudammatoceras Elmi (1963), a genus also based on A. subinsignis Oppel, is considered a junior synonym of Bredyia. The stratigraphical range of B. subinsignis seems to be limited to the Lower Aalenian (Opalinum and Scissum Zones) and records of its occurrence in the Murchisonae Zone have not been substantiated during this study. Geographically this uncommon ammonite seems to have been widely distributed throughout boreal Jurassic seas in Europe and in Tethyan sediments of Caucasia and the Northern Mediterranean. Acknowledgements. Much of the work was done during the tenure of a N.E.R.C. research studentship at the University of Hull, and I would also like to thank the University of Durham Staff Research Fund. I acknowledge the help given by Herr U. Bayer, Brigadier G. Bomford, Mr. E. J. Chaplin, Dr. R. M. C. Eagar, Dr. M. K. Howarth, Dr. E Penn, Mr. D. Phillips, Dr. G. Schairer, Dr. M. Warth, and Mr. J. M. Edmonds. To the latter I am also particularly grateful for the loan of valuable manuscript notes. Dr. G. Larwood and P. F. Rawson kindly read and criticized the hnal script. EXPLANATION OF PLATE 84 Bredyia subinsignis (Oppel) [M] Figs. 1, 2. A partial internal mould of an immature macroconch from the Northampton Ironstones of Duston, near Northampton. BM C77513, x 1. Figs. 3, 4. The plastotype of Ammonites subinsignis (Munich ASVIII 76), from the Torulosus Schichten (Opalinum Zone) of Gomaringen, near Tubingen, West Germany. Described by Oppel (1856, p. 367) and later figured by Renz (1925, pi. 1, fig. 5), x 1. Figs. 5, 6. An ironstone internal mould of a septate nucleus from Billing Road, near Northampton. BM C77515, xl. Bredyia subinsignis (Oppel) [m] Figs. 7, 8. A complete but immature example from the Scissum Bed of Sherborne (probably Sandford Lane), Dorset. GSM 69945 (Buckman Collection), x 1. Figs. 9, 10. A mature specimen showing the base of lappets from the Scissum Beds (Scissum Zone) of Burton Cliff, Dorset. GSM 3666 (Buckman Collection), x 1. Figs. 1 1, 12. A mature example with a broken mouth border from the Northampton Sands of New Duston, near Northampton. BM C77995 (Buckman Collection), x 1. Figs. 13-24. Microconchs from the Scissum Beds of Burton Cliff, Dorset. 13, 14, a mature specimen with an incomplete aperture (BM C77997, Buckman Collection). 15, 16, another incomplete but adult example (BM C77985, Buckman Collection). 17, 18, and 19, 20 (BM C78460 and BM C78458 respec- tively, both author’s collection), complete immature specimens. 21-24, a well-preserved adult showing very fine midlateral lappets and small rostrum (BM C78457, author’s collection). All X 1, with the exception of fig. 24 which is x 3. PLATE 84 SENIOR, Bredyia subiusignis 692 PALAEONTOLOGY, VOLUME 20 REFERENCES ARKELL, w. J. 1956. The Jurassic System of the World. Edinburgh and London. 1957. In MOORE, R. c. (ed.). Treatise on Invertebrate Paleontology, Part L. Mollusca4. Univ. of Kansas and Geol. Soc. Amer. BAYER, u. 1972. Zur Ontogenie und Variabilitat des jurassichen Ammoniten Leioceras opalinum. Neues Jb. Geol. Paldont. Abh. 140, 306-327. BENECKE, E. w. 1905. Die Versteinerungen der Eisenerzformation von Deutsch Lothringen und Luxemburg. Abh. geol. Spezkarte Els. -Loth. 6, 1-598, pis. 1-59. BOMFORD, G. 1948. New sections in the Inferior Oolite. Proc. Geol. Ass. 59, 148-150. BRASIL, L. 1893. Etude sur le niveau a Ammonites opalinus en Normandie. Bull. Soc. geol. Normandie, 15, 37-41, pi. 5. BUCKMAN, s. 1887-1907. Ammonites of the ‘Inferior Oolite Series’. Palaeontogr. Soc. [Monogr.], 1-456 + i-cclxxii; pis. 1-92, suppl. pis. 1-24. 1892. The reported occurrence of Ammonites Jurensis in the Northampton Sands. Geol. Mag. (3), 9, 258-260. 1910u. Certain Jurassic (Inferior Oolite) specimens of ammonites and Brachiopoda. Q. Jl geol. Soc. Loud. 66, 90-108, pis. 9-12. 19106. Communication to the President of the Geological Society of London. Proc. geol. Soc. Lond. 66, p. xciv. 1909-1930. Yorkshire Type Ammonites (7, 2); Type Ammonites (3-7). London and Thame. CALLOO, B. 1972. In MOUTERDE, R., RUGET, c. and CALLOO, B. Les limites d’etages. Examen du probleme de la limite Aalenien-Bajocian. Man. Bur. Rech. geol. minier. 77, 59-68. CURRIE, E. D. 1944. Growth stages in some Jurassic Ammonites. Trans. R. Soc. Edinb. 63, 171-198, 1 pi. DONOVAN, D. T. 1954. Synoptic supplement to Wright’s ‘Monograph on the Lias Ammonites of the British Isles’. Palaeontogr. Soc. [Monogr.], 1-54. DUMORTIER, E. 1874. Etudes paleontologiques sur les depots jurassiques du Bassin du Rhone, 4; Le Lias superieur. Paris. ELMi, s. 1963. Les Hammatoceratinae (Ammonitina) dans le Dogger Inferieur du Bassin Rhodanien. Trav. Lab. Geol. Univ. Lyon, 10, 1-144, pis. 1-11. GTCZY, B. 1966. Ammonoides Jurassique de Csernye, Montagne Bakony, Hongrie (Part I, Hammato- ceratidae). Geologica hung, seria palaeontologica, 34, 1-276, pis. I-XLIV. GERARD, c. H. and BiCHELONNE, J. 1940. Les Ammonites aaleniennes du Minerai de Per de Lorraine. Mem. Soc. geol. Er., N.s. 19, (42), 1-60, pis. 1-33. HOLDER, H. 1973. Miscellanea cephalopodica. Munster Eorsch. Geol. Paldont. 29, 39-76, pis. 1-3. MiGACHEVA, G. E. 1962. Aalenian Ammonoides from the North West Caucasus. Zap. Geol. Otdel Kharkov Gosud. Univ. 15, 69-93, pis. 1-8. NEA VERSON, E. 1927. The attachment of the ammonite siphuncle. Proc. Liverpool Geol. Soc. 14, 65-77, pi. 2. NEWTON, E. T. 1891. Note on the occurrence of Ammonites Jurensis in the Ironstones of the Northampton Sands in the neighbourhood of Northampton. Geol. Mag. (3), 8, 493-494. OPPEL, A. 1856-1858. Die Jura Formation Englands, Frankreichs und des siid westlichen Deutschlands. Jh. Var. veterl. Naturkde Wiirtt. 12-14, 1-857. PRiNZ, G. 1904. Die Fauna der alteren Jurabildungen im nordostlichen Bakony. Mitteil. Jb. K. ungar. geol. Anst. 15, 1-142, pis. 1-38. RENZ, c. 1910. Stratigraphischen Untersuchunge im Griechischen Mesozoikum und Palaeozoikum. Jb. geol. Bundesanst., Wien, 60, 421-636, pis. 18-22. 191 1. Die Insel Ithaka. Z. dt. geol. Ges. 63, 468-495, pi. 19. 1925. Beitrage sur Cephalopoden fauna des alteren Doggers am Monte San Giuliano (Monte Erice) bei Trapani in Westsizilien. Abh. schweiz. Ges. 45, 2-33, pis. I-II. RICHARDSON, L. 1923. Certain Jurassic (Aalenian-Vesulian) strata of the Banbury District, Oxfordshire. Proc. Cotteswold Nat. Eld Club, 21, 109-132, pi. 2. 1925. Certain Jurassic (Aalenian-Vesulian) strata of the Duston Area, Northamptonshire. Ibid. 22, 137-152. 1928-1930. The Inferior Oolite and contiguous deposits of the Burton Bradstock-Broadwindsor District, Dorset. Ibid. 23, 35-68 (1928); 149-186 (1929); 253-264 (1930). SENIOR: THE JURASSIC AMMONITE BREDYIA 693 SENIOR, J. R. 1971. Wrinkle-layer structures in Jurassic ammonites. Palaeontology, 14, 107-1 13, pis. 13-14. PARSONS, c. F. and torrens, h. s. 1970. New Sections in the Inferior Oolite of South Dorset. Proc. Dorset nat. Hist, archaeol. Soc. 91, 114-119. SPATH, L. E. 1931. Revision of the Jurassic cephalopod fauna of Kachh (Cutch), parts IV and V. Mem. geol. Surv. India, Palaeont. Indica, N.s. 9, 279-658, pis. 48-124. STURANi, c. 1971. Ammonites and stratigraphy of the "Posidonia alpina' Beds of the Venetian Alps (Middle Jurassic, mainly Bajocian). Mem. Inst. geol. Min. Univ. Padova, 28, 1-190, pis. 1-16. WESTERMANN, G. E. G. 1964. The Ammonite fauna of the Kialagvik Formation at Wide Bay, Alaska Peninsula. Part I, Lower Bajocian (Aalenian). Bull. Amer. Paleont. 47, 329-503, pis. 44-76. 1969. The Ammonite fauna of the Kialagvik Formation at Wide Bay, Alaska Peninsula. Part II. Sonninia Sowerbyi Zone (Bajocian). Ibid. 57, 5-226, pis. 1-47. WRIGHT, T. 1878-1886. Monograph of the Lias Ammonites of the British Islands. Palaeontogr. Soc. [Monogr.], 1-503, pis. i-lxxxviii. J. R. SENIOR Original typescript received 29 March 1976 Revised typescript received 21 June 1976 Department of Extra-Mural Studies University of Durham 32 Old Elvet Durham DHl 3JB 1} t- ,J£ TOOTH FUNCTION AND SUCCESSION IN THE TRIASSIC REPTILE PROCOLOPHON TRIGONICEPS by c. E. Gow Abstract. Dental morphology and tooth succession in Procolophon are described and discussed in detail. Replace- ment is not alternate; instead, a limited number of teeth are added at the back of the row and tost from the front. It is possible that the teeth of old individuals represent yet another set. The Permo Triassic procolophonids probably had a world-wide distribution. They are known from European Russia, Western Europe, and North America, and from South Africa, South America, and Antarctica. They will doubtless eventually also be found in India and Australia. The procolophonids are primitive cotylosaurs of obscure affinities characterized by a uniquely specialized heterodont dentition. In Procolophon Owen, 1876 a battery of incisiform teeth (hereafter referred to as incisors) in the dentary rests within the arc formed by the premaxillary incisors. Terminal facets are formed on the incisors by tooth-to-tooth contact during the bite. The transversely widened molariform cheek teeth (hereafter referred to as molars) intermesh in the resting position, but grind the food in a crown-to-crown pounding action. Adults probably had a rather specialized vegetable diet, such as seeds or seed-like structures. Colbert (1946) and van Heerden (1974) agree with Broili and Schroder’s (1936) description of the teeth of Procolophon as protothecodont, due to the presence of extensive pulp cavities. Van Heerden tabulates tooth counts gleaned from the litera- ture, which all fall within the range found in the present study. Broom (1936) and Broili and Schroder suggested that variation in tooth count might be due to sexual dimorphism. Both authors specifically exclude the possibility of tooth replacement. Van Heerden hypothesized that teeth might be added at the back of the premaxillary row and, by implication, also at the back of the maxillary row. Colbert and Kitching (1975) clearly accepting that P. trigoniceps had a fixed number of teeth, write of a seventh maxillary tooth as being ‘reduced’. They, like van Heerden, describe the teeth as biting in the intermeshed position. They further believe that the size of the first maxillary tooth varies considerably within the speeies. The most significant contribution in the field of procolophonid dentitions is that of Ivachnenko. Writing of Contritosaurus, a tiny Lower Triassic procolophonid from the U.S.S.R., he states (1974, pp. 350-351): ‘In connection with the appreciable differentation of the teeth, replacement is occasionally observed only on the front teeth of the maxillary and dentary. Replacement is hardly ever observed in the rear “quasicheek” teeth. However, when the size of the animal is increased the very last small teeth are greatly enlarged, reaching the height of the preceding teeth, and new [Palaeontology, Vol. 20, Part 3, 1977, pp. 695-704.] 696 PALAEONTOLOGY, VOLUME 20 fairly small teeth appear behind them. . . . The rear quasicheek teeth of Contritosaurus have a strong feature not previously noted in procolophonids, namely the presence of fairly small semicircular sulci surrounding the teeth on the inside and outside of the jaw. A row of small openings extends along the floor of the sulcus. The purpose of these structures, which make the insertion of the teeth less strong, is not clear.’ (Translated from the original Russian.) MATERIAL AND METHODS This study has been based almost entirely on the collections in the Bernard Price Institute. The material is rather varied. The bone is invariably very soft, filled with calcium carbonate crystals, and embedded in hard red mudstone. Very occasionally a specimen is found where the quality of the bone allows detailed preparation. In another form the specimens occur as very detailed natural moulds in indurated red mudstone, only occasionally requiring the removal of the last remnants of bone. Apart from standard preparation techniques, most of the present study relies on casts taken from the moulds. Black rubber latex proved the best impression medium. This had to be worked into the small cavities, and even then it was usually necessary to work from more than one impression of each specimen. Apart from air bubbles, care was required in order to recognize artefacts in the latex which resembled morpho- logical features. Dentition q/ Procolophon trigoniceps Premaxillary teeth and their eounterparts in the dentary (text-fig. 1a, b, and G). There are typically 4/3 incisiform teeth. These are mildly recurved, with a pair of lateral grooves on the distal portion of the lingual surface. They are subject to three forms of wear. The tips are worn flat in direct occlusion (necessitating forward movement of the jaw during a nipping phase of the bite). A second type of facet is formed by teeth remaining in contact after tip-to-tip occlusion, thus gouging facets posterior and anterior to the tip in upper and lower teeth respectively. The third type of wear is seen on the central tooth in G; this is caused by abrasive contact between the sides of opposing teeth. Incisors are subject to occasional loss, but no replacements have been found. Molariform teeth (text-figs. 1, 3, and 5). There is no fixed formula for cheek teeth; numbers may vary between five and nine or more, with the majority in the range 6/5 to 7/7. It was initially assumed that dental analysis in these primitive reptiles would be difficult, due to possible lack of correspondence between ontogenetic stage and skull size, but fortunately this problem does not seem to arise. Owing to the fragmentary nature of the material, it is often not possible accurately to estimate the original size of a complete skull. The twelve dentitions figured are therefore all drawn to the same scale, and it is readily apparent that they increase in size from A to L. There are probably six size groups represented, ranging in 5-mm steps from 30 to 60 mm maximum skull length. The molariform teeth are transversely widened with a basically bilobate structure (text-fig. 1c-e). They are bulbous in lateral aspect, narrowing to the tips. The pulp GOW; TEETH OF REPTILE PROCOLOPHON 697 cavity is very extensive but is never breached during wear. The enamel is very thin. A mature tooth situated centrally in the row has an extensive root zone (text-fig. 5b) surrounded by bone of attachment, and having a good nutrient and sensory supply. This condition is clearly protothecodont. Unworn teeth have sharply pointed labial and lingual tips connected by a sharp eoncave ridge (text-fig. 2). The tips abrade rapidly at first, until these areas are actually wider than the connecting surface, which then in its turn abrades more rapidly, thus tending to retain the concavity. Eventually the whole occlusal surface has a uniform surface area, when all portions will wear at the same rate. The concavity in the occlusal surface becomes less pronounced, and in some cases the surface becomes flattened. This sequence of events is shown diagrammatically in text-fig. 2. There is a striking similarity between the molar dentitions of procolophonids as described in this paper and those of bauriamorphs as described by Crompton (1962). Both use a simple pounding action, and both start with a transversely widened essentially concave tooth crown and are mechanically designed to retain this crown shape as long as possible. The teeth seem to be subjected to maximum wear when centrally situated in the row. Teeth formed anterior to this point never undergo extreme wear, while at the back of the row teeth become fully functional before undergoing any abrasion. This wear pattern is produced by a simple pounding action, the jaw hinging on large, trans- versely orientated, banana-shaped quadrate articular facets. The details of the crown TEXT-FIG. 1 . Procolophon trigoniceps. a, left upper and B, right lower incisors of specimen no B.P.I. 957, internal aspect, c-f, right upper molars of specimen no. B.P.I. 2282; c, distal view of M^; d, distal view of M^; E, anterior view of M^; f, distal view of M''. G, right upper incisors of specimen no. B.P.I. 2282, internal aspect. TEXT-FIG. 2. Procolophon tri- goniceps. Stages of tooth wear, worn surfaces hatched. Crown views on the left, sectional views on the right, with previous wear stage shown by dashed line. A, points connected by a sharp ridge. B, wear on the points slower as greater cross-sectional area is exposed, c, stage of uniform wear. 698 PALAEONTOLOGY, VOLUME 20 in some of the casts is very good, particularly in B.P.l. 2269. Mesial and distal enamel ridges stand proud of the dentine, while at the lateral margins the enamel is confluent and smoothly rounded off. The enamel being thin, there is an apparent tendency for it to chip away as a result of pounding mesially and distally. Several crowns display transverse striations clearly visible at x 40 magnification. Close inspection shows that they occur on any one side of the occlusal surface. These scratches must have been made by hard particles being forced ‘downslope’ towards the centre of the crown during the bite. Molar occlusion is normally faultless, but in B.P.l. 2282 (text-fig. 1) there is a well- preserved upper dentition where occluding surfaces were T 0-5 mm out of true during the pounding phase, so that the lower teeth tended to scrape against the posterior surface of the uppers. In M^ there are two areas of deepest wear (shaded) representing the points of impact of the tips of the lower tooth. In this tooth, as well as in M^ and M", the rather oblique occlusal surface is covered with curious lunate pits, reminiscent of those on the surface of boulders from high-energy streams. These features support the view that the teeth did not move transversely and that food was comminuted by pounding only. Text-fig. 3 clearly demonstrates the pattern of succession of molar teeth. In the juvenile A the formula is 6/5 with M; a small new tooth. In B, M5 has erupted further and M^ has just appeared, giving the formula 7/5. C has the same number of teeth as B, but here all are well worn, M^ and M5 occupy more anterior positions than young teeth of the same designation, and it is suggested that M^ is about to be shed. Next it is necessary to add a hypothetical case 6/6 by adding a lower and losing an upper tooth. This is followed by D at 6/7 where M7 is very new and Mj old. E and F are both larger animals than D and it is suggested that their dental formula of 6/6 was arrived at by the loss of Mj. The next stage is G in which a new M^ is newly erupted (present on the left side only). In H at 7/6, M^ has matured considerably, while I has added M7 to give 7/7. In J and K the count of 7/6 is achieved by the loss of M^ and Ml and addition of a new M^. In L, a very large animal, the formula has reverted to 6/5 by the loss of an upper and a lower tooth. From the above data it is possible to construct a model of molar succession in Procolophon \ this is attempted in text-fig. 4, which reads as follows: In stage 1 (specimens A-C) M^ occludes in front of Mj. Specimens B and C have added M^. In stage 2 (specimen D) M^ has been lost. M^ now occludes behind Mj. The upper teeth are designated by dashed numbers to indicate that they are not the same teeth as bear these numbers in stage 1. Two lower molars have been added. In stage 3 (specimens E-I) Mi has been lost and the existing lower teeth are designated by dashed numbers as for the uppers in stage 2. As in stage 1, the first upper molar occludes in front of the first lower molar. Specimens G and H have added an upper molar and specimen I has added a lower molar. By stage 4 (specimens J and K) there has been the additional loss of M^ and Mi and the addition of M^. The double dashes indicate that the functional molars are different teeth from their counterparts in the previous stages. Stage 5 (specimen F) is attained by the loss of both M^ and Mi. GOW: TEETH OF REPTILE PROCOLOPHON 699 c c c (U (U -O g Dh oi 'S CD OQ X O O c c QJ c C S ^ o> S g o o 0\ 0\ ^CQ C4-H o 0 c C C g e 1 § a (U ^ ■£ Q a o 133 ^ l-H C/3 ^ ^ Oh a qa u d 5 c c a vD m -H /^ 01 ON ON i ? H m m w d d H c c 700 PALAEONTOLOGY, VOLUME 20 This model requires the loss of three upper and lower molars and the addition of three upper and lower molars. It combines a replacement sequence with a consistent pattern of occlusion. Molar teeth are added at the back of the row. They arise in crypts situated labially to the rest of the row and continue to erupt as they migrate inwards and forwards (text-fig. 5a). It is, however, exceedingly difficult to visualize, let alone demonstrate, the histological basis of this mechanism. One possibility would be for profound histological changes to the implantation of the teeth to take place during brief periods of tooth movement. An alternative hypothesis would be that teeth are only added and that there is little age size correlation. This might be difficult to disprove, parti- 1 2 3 4 5 . 6.7 WaW 2 3 4 5 Wa'Wa (2) 1 . . f . 2', . 3', . 4', . 5', . 6', . 7', 1 1' 2' 3' 4 5 6 7' (4) A' ''' ' V 'C/ ^ ^ 1 r 1" r 2" 3" 4 5 (5) TEXT-FIG. 4. Procolophon trigoniceps. Model of molar succession. See text for explanation. A system of dashes is used to indicate that numbered teeth are not the same teeth as those occupying the same position in previous stages. GOW: TEETH OF REPTILE PROCOLOPHON 701 cularly as the first Ml is generally poorly known, being a small round tooth dis- placed labiad to the rest of the row. However, it is obvious that the Ml’s displayed so well in text-fig. 3j are of dilferent ages and morphologically unlike early Ml’s. There is no successional synchrony between right and left sides (see specimen G), but there clearly must be close control over development and movement of teeth in upper and lower jaws of the same side. Ivachnenko (1974) recorded rare instances of replacement in the molar series of Phaanthosaurus and Contritosaurus. There is evidence of occasional molar loss in the series studied here. In text-fig. 5a the right M^ is missing, there being simply a shallow depression in its place, while in text-fig. 5b a large empty tooth socket can be seen. There is no positive proof of the generation of a new tooth in the middle of the molar sequence subsequent to such loss. TEXT-FIG. 5. Procolophon trigoniceps. a, palatal view of upper molars of specimen no. B.P.I. 966. Note absence of third right molar and far labial situation of IVT on both sides, b. Lateral view of lightly ground portion of maxilla of specimen no. B.P.I. 3899. Abbreviations; b.a. bone of attachment; d, dentine; e, enamel; e.s. empty socket; n.c. nutrient canal; p. pulp cavity; r. root. The above analysis deals with a graded sequence of twelve specimens. It is now necessary to discuss several specimens which fall outside this range but which are nevertheless referrable to Procolophon trigoniceps. The first of these, B.P.I. 1187 (text-fig. 6) consists of a partly disarticulated skull and the anterior portion of the skeleton of a very small animal. The teeth of this animal are tiny and beautifully preserved. There are four premaxillary teeth followed by twelve maxillary molars. The dentary count is uncertain, as the tip of the jaw is missing. The skull itself is about the same size (about 30 mm long) as B.P.I. 959 (text-fig. 3a), but the latter has a normal count of larger molars. It does not seem justifiable to regard this single specimen as representative of a new species. I prefer to suggest that in animals of this size there may have been a change of diet from insects to plant material, and that the cheek dentition has therefore been replaced between B.P.I. 1157 and 959. It is normal in small reptiles that there is a higher number of teeth in insectivorous dentitions than in herbivorous dentitions. The above being so, then the type of Spondylolestes rubidgei (Broom 1937) is seen to fall within the range of P. trigoniceps. (According to Broom this specimen has thirteen dentary teeth, which would give three incisors and ten molars.) n.c. 0 4 cm 702 PALAEONTOLOGY, VOLUME 20 Another specimen which does not fit the general picture is B.P.I. 4284 (text-fig. 7). This is an exceptionally large, and hence probably old, animal. This skull is about one-third again longer than the next largest specimen, very broad, with large robust quadratojugal horns. The molar count is 7/7, and the teeth are remarkably small and mediodistally narrow for a skull of this size. I suggest that it was unusual for a P. trigoniceps to attain such a large size and great age, and that in the process its normal complement of molars was exhausted and worn away to be followed by a completely new abnormal set. This would fit the pattern already suggested by other apparent instances of replacement, that replacement is retained in these animals purely as a contingency mechanism. This is not an entirely new concept. Gans (pers. comm.) has recorded an instance of a similar sort of spontaneous regeneration in a crocodilian which lost all its teeth in a fight. A third specimen which falls outside the normal range for P. trigoniceps is the type of P. baini (Broom 1936), a large specimen (about 60 mm skull length) having eight maxillary teeth on both sides, one more than any of the larger specimens discussed above. It is clearly undesirable that this should be the basis of specific status for a single specimen. CONCLUSIONS The dentition of Procolophon is described. Incisiform teeth are fixed in number and may be replaced. Molariform teeth vary in number with age, being added in labially situated crypts at the back of the row and lost from the front of the row. Rare cases of loss within the molar row are reported. Teeth appear to be typically acrodont, but are in fact protothecodont having deep roots and extensive pulp cavities. The mechanism of forward movement is unknown. Replacement appears to be retained as a contingency mechanism only, possibly filling in accidental gaps and possibly providing a complete new dentition in old animals. Large banana-shaped quadrate articular facets ensure that the bite is a simple pounding action. Glenoid detail is lacking, but a mechanism is necessary whereby the teeth can be moved from the resting to the occluding position. Incisors are subject chiefly to terminal wear. Molar teeth are designed to retain concave opposing surfaces for as long as possible— ultimately the wear facets become flattened. Attention is drawn to the extremely close parallel between the dentitions of procolophonids and those of bauriamorph therocephalians. Acknowledgements. I have benefitted from discussions with Dr. James Kitching, who found most of the material on which this paper is based. Dr. Mike Cluver of the South African Museum was extremely helpful with photographs and specimens. Some of the more significant findings owe much to discussions with Professor Carl Gans. Dr. James Hopson read an early manuscript and made many helpful suggestions. GOW: TEETH OF REPTILE PROCOLOPHON 703 TEXT-FIG. 6. Procolophon trigoniceps, specimen no. B.P.I. 1187. Above, left, partly flattened skull in lateral view. Below, left, lateral view of right upper dentition enlarged. Right, occlusal view of left upper dentition. Breaks indicated by heavy hatching, pulp cavities black, wear facets finely hatched. Abbreviations; F, frontal; p, parietal; Q, quadrate; t, tabular. TEXT-FIG. 7. Procolophon trigoniceps, specimen no. B.P.I. 4248. Above, denti- tion of left side. Right, skull in dorsal view (top) and lateral view (bottom). 704 PALAEONTOLOGY, VOLUME 20 REFERENCES BROILI, F. and SCHRODER, J. 1936. liber Procolophon Owen. Sitz. Ber. Akad. Wiss. Munchen, 2, 239-256. BROOM, R. 1936. The South African Procolophonia. Ann. Tvl. Mus. 18, 387-391. 1937. A further contribution to our knowledge of the fossil reptiles of the Karroo. Proc. zool. Soc. London (B), 107, 299-318. COLBERT, E. H. 1946. Hypsognuthus, a Triassic reptile from New Jersey. Bull. Am. Mus. nat. Hist. 86, 221-274. and KiTCHiNG, J. w. 1975. The Triassic reptile Procolophon in Antarctica. Am. Mus. Novit. 2566, CROMPTON, A. w. 1962. On the dentition and tooth replacement in two Bauriamorph reptiles. Ann. S. Afr. Mus. 46, 231-255. iVACHNENKO, M. F. 1974. New data on the early Triassic procolophonids. Palaeont. Zh. (3), 68-74. [In Russian.] VAN HEERDEN, J. 1974. A short note on some natural casts of the cotylosaurian reptile Procolophon. Navors. nas. Mus., Bloemfontein, 2, 417-428. 1-23. C. E. GOW Typescript received 1 April 1976 Revised typescript received 10 May 1976 Bernard Price Institute (Palaeontology) University of the Witwatersrand Milner Park Johannesburg 2001 South Africa A CONSIDERATION OF THE TRIBE THYRSOPORELEEAE, DASYCLAD AEGAE by GRAHAM F. ELLIOTT Abstract. The algal tribe Thyrsoporelleae Pia, 1927 (Family Dasycladaceae, Order Dasycladales) is examined in the light of later additions and discoveries. It is considered that the reasons for the earlier grouping are not now valid : Thyrsoporella, Belzungia, Dohunniella, and Placklesia now constitute the Thyrsoporelleae emend. ; DissocladeUa constitutes the Dissocladelleae trib. nov.; Truiocladus is transferred to the Triploporelleae. Possible ancestries are discussed, the limitations of the nature of this fossil evidence considered, and the extinction of all three reviewed against what is known and surmised of the decline of the post-Triassic Dasycladaceae generally. The foundations of our knowledge of fossil dasycladacean algae were laid by various workers, amongst whom Julius Pia is usually considered pre-eminent. With- out discounting the pioneer work of Munier-Chalmas (1877) or the meticulously careful studies of the Morellets (1913, 1922) on a limited microflora, it was Pia who, in a series of publications from 1912 to 1943, endeavoured to interpret the fossil dasycladacean record as a whole. His sometimes bizarre reconstructions from limited thin-section evidence, and his ever-ready facility for postulating phylogenetic links, qualify but do not invalidate his achievement, which all subsequent workers have recognized. The broad outlines of his classification have been followed, or at any rate not replaced, up to the present day. A recent timely re-examination in some detail of assumed fundamentals and questioning of deductions from them by the ‘Groupe franqais pour I’etude des algues fossiles’ (Bassoulet et al. 1975, p. 288) paid tribute to Pia’s work whilst criticizing his successors for their largely unqualified acceptance or failure to extrapolate in the light of later knowledge. Pia’s subdivision of the family Dasycladaceae (then including all taxa now placed within the Dasycladales) was into tribes (Pia 1920, p. 237). He used this term because of the relatively large number of such small divisions recognized, and because of the very unequal size of the two higher-category subfamilies, had he then proposed them. It so happens that one of these tribes, the Thyrsoporelleae (Pia 1927) is, as now con- stituted in 1977, of especial interest as showing unusual anomalies for a conventional taxonomic grouping. Moreover, in a considerable personal experience over the years of these particular fossils I have found that almost invariably my doubts and uncer- tainties were resolved neither by the literature nor by more material. It seems useful, therefore, to consider the tribe and its content anew, and this is now attempted below. HISTORICAL In 1927 Pia, in a textbook treatment of the algae, proposed the tribe Thyrsoporelleae (Pia 1927, p. 77). In it he placed Trinocladus Raineri, then known only from the Upper Cretaceous; Thyrsoporella Giimbel, similarly from the Eocene; and Belzungia Morellet, similarly from the Palaeocene-Eocene. In these genera Pia stressed the [Palaeontology, Vol. 20, Part 3, 1977, pp. 705-714.] 706 PALAEONTOLOGY, VOLUME 20 conspicuous thickening of primary and secondary, and of other branch-elements if present, which he considered as evidenee of their having contained reproductive elements, and he added that this tribe probably came from the Triploporelleae (Jurassic-Cretaceous). In 1935 Pia again considered these fossils in three papers: one published in that year and two dated 1936. Both of these last must have been completed in 1935, since he refers in one to the other as ‘Rama Rao and Pia 1935’, and the former appeared in January 1936 (Pia 1935, 1936a, b). The information on which he amplified his concept of the Thyrsoporelleae is divided between the three. The new genus Disso- cladella appeared in Pia 19366 (type species D. savitriae Pia): a distinctive form, discussed below, with near-spherical swollen primary branch-elements. In Pia (1936a) a redescription of the Upper Cretaceous Trinocladus tripolitarms Raineri was accompanied by detailed description of the accompanying T. undidatus (Raineri) Pia and its reference to Dissocladella. (A recent clarification of the stratigraphy at Raineri and Pia’s locality is to be found in Radoicic (1975).) Pia, whilst detailing differences between D. savitriae and D. undidatus, wrote that the latter ‘might very well be the direct ancestor’ of the former. He regarded Dissocladella as the simpler genus, stating that ‘its natural place in the system is near the starting-point giving origin to the Thyrsoporelleae. Whether it is better included with this tribus (taken in a somewhat wider sense) or with the Triploporelleae, I am not yet sure. This question can only be discussed when certain new Triassic species of Diplopora, resembling in an astonishing way Dissocladella, will have been described’ (Pia 19366; pp. 18, 19). And in 1935 Pia (p. 243), describing and discussing the Middle Triassic Diplopora subtilis Pia var. dissocladelloidea Pia, gave it as a possible origin for the line of succession of four genera: Dissocladella, Trinocladus, Thyrsoporella, and Belzungia. Thus in 1936 Pia had suggested a Triassic origin for his Cretaceous-Eocene Thyrsoporelleae, with a link in the Cretaceous between Dissocladella and the more advanced Trinocladus, leading eventually (Pia 1936a, p. 7) to the Eocene type genus Thyrsoporella and its close relation Belzungia. All possess ‘swollen branch-systems’ and this may be quoted as a logical classificatory character. But iht form of these branch-systems is conspicuously very different: Thyrsoporella (and Belzungia) show a few thickened irregular branches taking up much space in the thick calcareous wall, and divided by consequent irregular-outlined calcification ; in Trinocladus the spindle- shaped branch-elements, long or short, usually take up much less space between consequently thicker calcification in a thick wall; and in Dissocladella the primaries are swollen into conspicuous spherical structures with much smaller secondaries, all within a very thin wall, occasioned by proportionally larger outer and inner thallus- diameters than with the other two. During the subsequent forty years, up to the present, two new genera and many new species were described for the Thyrsoporelleae. They extend the total range of the tribe from Upper Triassic to Eocene: the three component elements outlined above, Thyrsoporella, etc., Trinocladus and Dissocladella, extending from Upper Triassic, Upper Jurassic, and Upper Trias or Lias respectively. The individual values of the various new taxa contribute unequally to the understanding of the subfamily, e.g. of my species, T. radoicici and D. deserta (Elliott, 1968) were based on very ELLIOTT: DASYCLAD ALGAE 707 limited, and on abundant but extremely poorly preserved material, respectively. They were significant for the palaeontology of the Middle East but of no value for this present study since they occur at levels from which much better-preserved and more typical species of their respective genera occur. It is, therefore, proposed to examine now the significant taxa only, i.e. those which extend the total range or which increase our knowledge over and above the record of a new species as such, and this is attempted for the three groups, beginning with Dissoc/adella which Pia considered ancestral ; then Trinocladus, to which he connected it, and finally Thyrsoporella and its related genera. Elements of the Thyrsoporelleae Dissocladella D. ereticaiOtt, 1965) was described from within an Upper Triassic-Lias succession. It is a thin-walled dasycladacean, ovoid-elongate, as reconstructed in Ott’s fig. 4, whereas the much smaller Palaeocene D. savitriae Pia is annular-elongate (Pia 19366, reconstruction fig. 43; Elliott 1968, solid specimen pi. 11, fig. 3). But the distinctive branch-pattern within the thin walls is closely similar: swollen near- spherical primaries followed by several short secondaries. On morphological grounds, the attribution of these two species to the same genus is reasonable. Could they perhaps be two similar but separate evolutionary develop- ments of which the calcification (all we have, and on which the genus is necessarily based) is closely similar, and which took place in different geological periods? Iterative evolution, repeated development in time of identical or near-identical forms from a common stock, has been postulated for some organisms. Henson (1950, p. 14) considered he had evidence for it in Tertiary peneroplid foraminifera. He had, how- ever, a profusion of well-preserved material on which to work, which is not available D E F TEXT-FIG. 1 . Diagrammatic representations, much enlarged, of comparable thin sections of : a, Dissocladella savitriae Pia. B, D. cretica Ott. c, Trinocladus tripolitanus (Raineri) Pia. D, T. exoticus Elliott. E, Placklesia multipora Bilgiitay. F, Dobwmiella coriniensis Elliott. Proportions and number of elements approximately correct in individual figures, but all figures converted to the same size for comparison. Drawn by Mr. M. Crawley. 708 PALAEONTOLOGY, VOLUME 20 for Dissocladella. It seems most likely, therefore, from the limited evidence, that D. cretica is a fortunate discovery of an early occurrence of a genus whose species were never very numerous. The essential importance of D. cretica is its closeness in geological age to Pia’s Middle Triassic Diplopora suhtilis dissocladelloidea which he postulated as an ancestor for Dissocladella. This was later incorporated by Ott when describing D. eretica (1965, text-fig. 7) as part of a scheme of diplopore phytogeny. Pia’s detailed postulated ancestry is, I consider, a possibility rather than a prob- ability, but it is marginally improved by the finding of D. cretica. Given that Dissocladella existed from the older Mesozoic, in what light should D. undulata (Raineri) Pia of the Upper Cretaceous be regarded? This species was Pia’s connecting link between Trinocladus and Dissocladella : he transferred it from Trinocladus to Dissocladella, so making it the earliest known Dissocladella at that time. All Pia’s illustrations of this species (sketches of thin-sections and reconstructions) show branch-outlines like those of Trinocladus (though much shorter than in other Cretaceous species of that genus and branching only to the second, not the third, degree) rather than the peculiar spherical Dissocladella pattern. This is confirmed by my examination of materials from various localities in the Middle East as well as North Africa from which the types came. The species should, therefore, correctly be Trinocladus undulatus (Raineri) Pia, as Pia (1927) first referred to it. In most materials examined by me, T. undulatus is the constant associate of the larger T. tripolitanus Raineri. Usually both are ill-preserved: the smaller species is more numerous than T. tripolitanus which additionally shows tertiary branchlets. This constant association as fossils of two marine species suggests that they grew together in the same environment in life, which in turn throws doubts on the relation- ship. Were they in fact two species (the fossils do not suggest hybridization) or were they two forms of the same species, the smaller being either the remains of those plants, which stunted and reproducing early did not survive to achieve full growth, or possibly a record of high early mortality? Statistical analysis of large populations might throw light on this if better-preserved material can be found. Meanwhile, both species names are available for the calcifications as preserved for the palaeontologist. The important thing is that the genus Dissocladella is clarified by the removal and transfer of the species undulata. Trinocladus Since Pia’s revision (1936a) of the type species T. tripolitanus Raineri other Upper Cretaceous species, some larger and better-preserved, e.g. T. pinarensis (Keijzer 1945), T. exoticus (Elliott 1972) have been described. In this genus the spindle-shaped primary branches, of varying length and shape according to the species, may be rela- tively thin and tend to be set in a thick calcareous wall, though they take up more space proportionally in the smaller species. Of these last, T. perplexus (Elliott 1955, 1968) was first described from the Palaeocene-Lower Eocene: surprisingly, it was later discovered in the Upper Jurassic and carefully redescribed in comparison with the original (Conrad et al. 1975; Peybernes 1976). Obviously, a similar argument could be applied to these two stratigraphically separate occurrences of one species, as for the two occurrences of the genus Disso- ELLIOTT: DASYCLAD ALGAE 709 cladella discussed previously. But again, it seems reasonable to conclude that the fossil calcifications, which are all we have, do represent chance preservation of individuals of a stock whose occurrences were never more than locally abundant and whose range in time is now longer than formerly supposed. Thyrsoporella and related genera Pia (1927, \936b) knew only of the Eocene Thyrsoporella, a single-tubular dasycladacean fossil and its ‘serial-unit’ relation Belzimgia (Palaeocene-Eocene) with a beaded structure like Mizzia or CymopoHa spp. (Morellet and Morellet 1913). Within the calcareous walls of these fossils the verticils show characteristic thickened to swollen branch-system cavities which are somewhat irregular in outline, few in number, and, because of size and shape, take up much of the space so that the inter- vening calcification is conspicuously irregular in outline. The repeated branching lends itself to a simple formula indicating total number of successive primaries, secondaries, tertiaries, etc. Massieux (1966), in a detailed analysis, gave such a formula of 1:2:8:32 for Thyrsoporella and 1 : 2 : 4 : 8 : 1 6 : 32 for Belzimgia. As with Dissocladella and Trinoeladus much older forms are now known : Plaeklesia from the Rhaetic (Bilgiitay 1968) and Dobunniella from the Middle Jurassic (Elliott 1975). There are also doubtful, inadequately known forms recorded from the Jurassic {Thyrsoporella sp.. Lower Jurassic; T. (?) haligomoriensis and Belzimgia sp.. Upper Jurassic: Nikler and Sokac 1968; Yabe and Toyama 1949; Golonka 1970) but these do not affect the total range. The interesting thing about these genera, all showing the peculiar thickened irregular branches of Thyrsoporella type, is obtained by comparing their branch- formulae with geological age: Rhaetic 1:2:8:32:128 Plaeklesia Middle Jurassic 1:2:4 Dobunniella Eocene 1:2:8:32 Thyrsoporella Palaeocene-Eocene 1:2:4:8:16:32 Belzimgia Thus the most elaborate branching occurs in the earliest genus, with the most simple of intermediate age, before the later medium-complicated ones. The succession in time shows no definite progression in structural detail. In seeking an explanation of this, one must consider the effect of limited calcifica- tion in life as a factor in the selective nature of the fossil record of dasycladaceans. Erom living species we know that their calcification is usually near-constant in adult individuals of one species growing under normal conditions, i.e. it is usually a specific character though it may be light or heavy. It is capricious in siting between one taxon and another within dasycladaceans viewed as a whole. Thus there are all sorts of limited calcifications available for possible preservation as fossils, varying between a little calcification only around stem-cell or reproductive bodies, or a thin sheet only marginally near the tips of branches, up to a heavy calcification preserving a record of much of the plant’s gross external morphology. Where the calcification is minimal, much of the plant is unknown if the species is extinct. (Cf. the interpretation of the extinct Pagodaporella in the light of the living Dasycladus (Elliott 1968, p. 60).) It is thus possible that in life the branching of Dobunniella continued outside the calcified 710 PALAEONTOLOGY, VOLUME 20 zone, perhaps as elaborately as in the other genera. There is no evidence of this at all : whether it was so or not, it seems best to regard the genus as one of the chance witnesses preserved of the Thyrsoporella stock, whose details would shift slowly through time with the genetic patterning consequent on small local populations. Whether the differences between these taxa should be regarded as generic or specific is a taxonomic, not an evolutionary, question. Pia considered this problem for the Thyrsoporelleae as a whole (Pia \ 936b, p. 19). Personally I accord them generic rank, since the different calcifications preserved are all we have. New species would have the same general calcification but different sizes and proportions. The important thing is the long, if sporadic, record of that type of branching and its calcified surround, characteristic of Thyrsoporella and its allies. The Thyrsoporelleae reconsidered as a tribe The original definition of the Thyrsoporelleae referred to their swollen branches and to the presumed function of these as housing the reproductive elements (Pia 1927, p. 77). Some later-described species, e.g. Trinocladus pinarensis Keijzer are less obvious candidates for the secondary and tertiary branchlets having this function as in Pia’s definition. But in no case is there direct evidence of this in Thyrsoporelleae; it is in fact very exceptional generally in fossil dasycladaceans to see remains of reproductive bodies within the branches, e.g. in some examples of Triploporella. Usually, where one portion of the branch-system is markedly swollen, this has been presumed to have contained the reproductive elements. How far this is to be con- sidered a reasonable view depends on a consideration of what is known in living dasycladaceans (cf. Valet 1968, 1969) and its extrapolation to extinct forms (see discussion in Bassoulet et al. 1975, on Pia’s terminology); it is not further dealt with here. Whether Thyrsoporelleae carried their reproductive elements within the branch- ing of which we have evidence, or outside the calcification which is all we now have, is not known. But the distinction between the general outlines of the three branch- patterns characteristic of and persisting in Dissocladella, Trinocladus, and Thyrso- porella, etc., is important. Pia’s reasons for uniting them are no longer valid in the light of subsequent discoveries. Is their taxonomic union still justified; if not, should they be classified apart or with other dasycladacean genera outside the Thyrso- porelleae? Thyrsoporella, with Belzimgia, Dobunniella, and Placklesia are together the most distinctive of the three. Ranging from Rhaetic to Eocene, there is little else like them in branch-form and calcite surround. Presumably all the dasycladaceans of the Jurassic to Recent are likely to be modified survivors of the very rich Triassic flora, but Thyrsoporella and the others afford no real clue to their ancestry. Dr. Ernst Ott (in correspondence, 1975) compared the branch-pattern of the Permian Imperiella (Elliott, 1975) to Placklesia. The former, with swollen crowded branch-outlines, shows a delicate lace-like calcification pattern, different to that of Placklesia. It is such incidental details of structure, chemistry, etc., which, carried on unmodified, often mark lines of descent, and not types of structure as observed and formulated, how- ever important these are to progressive evolution itself. Dr. Ott’s comparison of the branches is, however, valid, the preservations are different, and his suggestion is the only one I can record for a possible origin of the tribe. ELLIOTT: DASYCLAD ALGAE 71 1 These four genera therefore stay together and from the name of the type genus now constitute the Thyrsoporelleae emend. (See Appendix.) Dissocladella, as restricted earlier in this account, is a separate stock. I have not examined material of the Triassic diplopore variety which Pia considered ancestral; from the published account (Pia 1935) it seems possible. It does in any case seem very likely that the genus arose from a Triassic ancestor. There seems now no special reason to associate it with Thyrsoporella and its allied genera. It can be compared with other genera showing spherically swollen branch-elements, e.g. Cylindroporella, where they are conventionally regarded as ‘fertile’ branches and where such verticils alternate with verticils of thin ‘sterile’ branches; or with Sarfatiella, showing the swollen elements only. (Did this last genus perhaps not calcify a lower, presumed non-reproductive part of the thallus?) In these two, however, there are no secondary branches from the inflated elements. Once again one is in the area of random morpho- logical comparisons, and Dissocladella, as known, seems to stand by itself. For that reason the genus, although solitary, becomes the occupant of Dissocladelleae trib. nov. (see Appendix), of possible diplopore origin as shown by Ott (1965). With Trinocladus, which again in this re-examination seems to stand apart from the other two, a comparison with other dasycladaceans is more fruitful. It compares well with Triploporella in swollen primaries and subsequent thinner branches, differ- ing in proportions. This relationship was considered by Pia followed by Kamptner (1958) who, in a general view of dasycladaceans, derived all Pia’s Thyrsoporelleae from Triploporella. The Upper Jurassic appearance of Trinoeladus also accords with this, Triploporella being Upper Jurassic and Cretaceous. Accordingly, Trinoeladus is here transferred to the Triploporelleae. The extinetion of the Thyrsoporelleae (sensu Pia) The possible origins of the Thyrsoporelleae (emend.) and Dissocladelleae nov., and the probable origin of Trinoeladus, have been discussed above. One thing they still have in common: they all ended in the early Tertiary, after surviving the Cretaceous-Palaeocene transition. Is this a fact for which a common explanation can be given? The Tethyan Palaeocene seems in certain facies to have contained favourable environments for algae of all kinds (Elliott 1968, p. 96). After the Eocene, however, with the rupture of the Tethys and continued drifting of shelf-seas as parts of their respective continental masses, the dasycladacean survivors are found as a relict flora with markedly discontinuous distribution of its component elements. It seems very unlikely that any of the numerous Palaeocene-Eocene dasycladacean genera which disappeared from the fossil record evolved into something else, so poor is the Recent flora, though a solitary exception is just possible with Pagodaporella and Dasyeladus. One asks, did those genera known fossil from the Cretaceous and still living today, such as Cyrnopolia and Neomeris, possess some inherent advantage over Pia’s Thyrsoporelleae? I think not. Few things are more striking than the way in which the teeming diplopore dasycladaceans of the Triassic lagoons have been replaced by the equally abundant codiacean Halimeda of the present-day atolls, as witnessed by diplopore limestones in the Alpine Trias and Halimeda limestones in the Indo-Pacific Tertiary. This phenomenon has been considered as possibly due to 712 PALAEONTOLOGY, VOLUME 20 the more efficient reproduction of the latter (Elliott 1968, p. 100). Whatever the cause, the replacement is a fact. During the long period of their gradual decline the dasy- cladaceans underwent a rich and varied evolution which did not improve their selectiveness for survival in any way that we can trace, since it was elaboration and diversification with their basic and constant fundamentals unchanged. It was the intra-regressive evolution to which attention has been drawn earlier in certain brachiopods (Elliott 1948, 1953). Such organisms may last a very long time geo- logically. Palaeontologists are prone to seek cause and effect to explain the biological changes of the past as zealously as they once sought for purpose in evolution. But chance plays a very great part in survival. Organisms long since superseded, in the sense of more highly organized competitors having evolved, will survive as relicts so long as a limited foothold can be maintained in a suitable environment. Their times of peril come when the environment changes rapidly (geologically speaking) and the few survivors have to establish their kind elsewhere. But even so, they may outlive various crises which are sporadically distributed over a very long time indeed. The algae discussed here did not survive the great changes in distribution of land and sea which began after the Eocene and which led gradually to the geography of the world as we know it today. In this they were not alone but were affected as were various other dasycladaceans. So far as we can judge, if this had not happened they could have been alive today like the surviving dasycladaceans ; strange little algae of warm coastal waters, forming a very minute element indeed in the marine flora. In conclusion, it would seem that the Thyrsoporelleae of Pia were, unintentionally, very well named. Eor the thyrsus was the emblem of Bacchus, whose initiates achieved, at best, an intuitive comprehension of the whole, rather than a detailed understanding of its component parts. appendix: diagnoses of emended and new tribes Class chlorophyceae Order dasycladales Family dasycladaceae Tribus thyrsoporelleae Pia 1927, emend. Tubular or serial-unit calcified dasycladaceans, medium to thick walled, with verticils each usually containing six to eight branches, which divide distally up to five times; all branches and branchlets thickened or swollen; calcification weak adjacent to stem-cell. Rhaetic-Eocene. Genera: Thyrsoporella, Belzimgia, Dobumiiella, Placklesia. ImperieUa (Permian) doubtfully referable to tribe. Tribus dissocladelleae nov. Elongate-ovoid or annulated-tubular calcified dasycladaceans, thin walled; verticils each containing numerous small branches, each showing one near-spherical short primary communicating proximally with the stem-cell by a pore or very short stem, and distally giving rise to a small number of very small inflated secondaries. Rhaetic or Lias, to Palaeocene (?Eocene). Genus: Dissocladella. ELLIOTT: DASYCLAD ALGAE 713 REFERENCES BASSOULET, J. P., BERNIER, P., DELOFFRE, R., GENOT, P., JAFFREZO, M., POIGNANT, A. F. and SEGONZAC, G. 1975. Reflexions sur la systematique des Dasycladales fossiles. Etude critique de la terminologie et importance relative des criteres de classification. Geobios, 8, 259-290. BiLGUTAY, u. 1968. Some Triassic calcareous algae from Plackles (Elohe Wand, Lower Austria). Verb, geol. Bundesanst., Wien, 1968, 65-79. CONRAD, M. A., PEYBERNES, B. and WEiDMANN, M. 1975. Presence de Trinocladus perplexus Elliott (Dasycladales) dans le Jurassique de France et d’Afrique du Nord-Est. C. r. Seanc. SPNH Geneve, N.s. 9, 14-29. ELLIOTT, G. F. 1948. The evolutionary significance of brachial evolufion in terebratelloid brachiopods. Ann. Mag. nat. Hist. (12), 1, 297-317. 1953. Brachial development and evolution in terebratelloid brachiopods. Biol. Rev. 28, 261-279. 1955. Fossil calcareous algae from the Middle East. Micropaleontology, 1, 125-131. 1968. Permian to Palaeocene calcareous algae (Dasycladaceae) of the Middle East. Bull. Br. Mas. nat. Hist. (Geol.) Suppl. 4, 1 1 1 pp. 1 972. Trinocladus exoticus, a new dasycladacean alga from the Upper Cretaceous of Borneo. Palaeonto- logy, 15, 619-622. 1975. Transported algae as indicators of different marine habitats in the English middle Jurassic. Ibid. 18, 351-366. GOLONKA, J. 1 970. Calcareous algae from the Upper Jurassic of the southern periphery of the Swietokrzyskie Mts. Part II: Chlorophyta and Porostromata. Bull. Acad. pol. Sci. Ser. Sci. geol. geogr. 18, 85-93. HENSON, F. R. s. 1950. Middle Eastern Tertiary Peneroplidae (Foraminifera) with remarks on the phylogeny and taxonomy of the family. Wakefield, England. 70 pp. KAMPTNER, E. 1958. Uber das System und die Stammesgeschichte der Dasycladaceen (Siphoneae verti- cillatae). Annin naturh. Mus. Wien, 62, 95-122. KEUZER, F. G. 1945. Outline of the geology of the eastern part of the province of Oriente, Cuba. Geogr. geol. Meded. Utrecht (2), 6, 1-238. MASSiEUX, M. 1966. ‘Les Algues du Nummulitique egyptien et des terrains Cretaces-Eocenes de quelques regions mesogeennes’ par J. Pfender 1940; etude de revision par M.M. Part 2; Etude critique. Rev. Micropaleont. 9, 135-146. MORELLET, L. and MORELLET, J. 1913. Les dasycladacccs du Tertiaire parisien. Mem. Soc. geol. Fr. (paleont.), 47, 1-43. 1922. Nouvelle contribution a I’etude des dasycladacees tertiaires. Ibid. 58, 1-35. MUNiER-CHALMAS, E. p. 1877. Observations sur les algues calcaires appartenant au groupe des siphonees verticillees (Dasycladacees Harv.) et confondues avec les foraminiferes. C.r. hehd. Seanc. Acad. Sci. Paris, 85, 814-817. NiKLER, L. and SOKAC, B. 1968. Biostratigraphy of the Jurassic of Velebit (Croatia). Geo. Vjesnik, Zagreb, 21, 161-176. OTT, E. 1 965. Dissocladella cretica, eine neue Kalkalge (Dasycladaceae) aus dem Mesozoikum der griechischen Inselwelt und ihre phylogenetischen Beziehungen. Neues jb. Geol. Paldont. Mh. 11, 683-693. PEYBERNES, B. 1976. Le Jurassique et le Cretace inferieur des Pyrenees franco-espagnoles entre la Garonne et la Mediterranee. Acad. Thesis, Univ. of Toulouse. 460 pp. (Algae, 403-412.) PIA, J. 1920. Die Siphoneae verticillatae vom Karbon bis zur Kreide. Abh. Zool.-bot. Ges. Wien, 11 (2), 1-263. 1927. Thallophyta: 1. Abteilung. In hirmer, m. Handbuch der Palaobotanik, Munich, Berlin. 708 pp. 1935. Die Diploporen des anisischen Stufe Bosniens. Ann. geol. Penin. balkan. 12, 190-246. 1936fl. Calcareous green algae from the Upper Cretaceous of Tripoli (North Africa). J. Paleont. 10,3-13. 19366. Description of the Algae. In rama rao, l. and pia, j. Fossil Algae from the Uppermost Cretaceous Beds (the Niniyur Group) of the Trichinopoly District, S. India. Mem. geol. Surv. India Palaeont. indica (N.S.), 21 (4), 49 pp. RADOicic, R. 1975. On Fikanella hammudai sp. nov. from the Upper Cretaceous of the Tripoli area (Lybia) and the age of strata containing Dissocladella ondulata Raineri. Ann. geol. Penin. balkan. 39, 147-152. 714 PALAEONTOLOGY, VOLUME 20 VALET, G. 1968. Contribution a I’etude des Dasycladales. 1. Morphogenese. Nova Hedwigia, 16, 21-82. 1969. Contribution a I’etude des Dasycladales. 2. Cytologie et reproduction. 3. Revision systematique. Ibid. 17, 551-664. YABE, H. and TOYAMA, s. 1949. New Dasycladaceae from the Jurassic Torinosu Limestone of the Sakawa Basin. II. Proc. Japan Acad. 25 (7), 40-44. GRAHAM F. ELLIOTT Typescript received 14 April 1976 Revised typescript received 10 June 1976 Department of Palaeontology British Museum (Natural History) Cromwell Road London SW7 5BD THE PALAEONTOLOGICAL ASSOCIATION The Association was founded in 1957 to further the study of palaeontology. It holds meetings and demonstrations as well as publishing Palaeontology and Special Papers in Palaeontology. Membership is open to individuals and to institutions on payment of the appropriate annual subscription: Institutional membership .... £25-00 (U.S. $50.00) Ordinary membership .... £8 00 (U.S. $16.00) Student membership .... £5 00 (U.S. $10.00) There is no admission fee. Institutional membership is only available by direct application, not through agents. Student members are persons receiving full-time instruction at educational institutions recognized by the Council. On first applying for membership, an application form should be obtained from the Membership Treasurer. 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H. Blackwell, Broad Street, Oxford 0X1 3BQ, England. COUNCIL 1977-1978 President'. Professor W. G. Chaloner, Department of Botany, Birkbeck College, London WCIE 7HX Vice-Presidents'. Dr. J. M. Hancock, Department of Geology, King’s. College, Strand, London WC2R2LS Dr. L. R. M. Cocks, Department of Palaeontology, British Museum (Natural History), Cromwell Road, London SW7 5BD Treasurer'. Mr. R. P. Tripp, High Wood, West Kingsdown, Sevenoaks, Kent TNI 5 6BN Membership Treasurer'. Dr. E. P. F. Rose, Department of Geology, Bedford College, Regent’s Park, London NWl 4NS Secretary : Dr. C. T. Scrutton, Department of Geology, The University, Newcastle upon Tyne NEl 7RU Editors Dr. C. P. Hughes, Department of Geology, Sedgwick Museum, Cambridge CB2 3EQ Professor J. W. Murray, Department of Geology, The University, Exeter EX4 4QE Professor C. B. Cox, Department of Zoology, King’s College, Strand, London WC2R 2LS Dr. M. G. Bassett, Department of Geology, National Museum of Wales, Cardiff CFl 3NP Other Members of Council Dr. M. C. Boulter, London Dr. P. J. Brenchley, Liverpool Dr. C. H. C. Brunton, London Dr. J. C. W. Cope, Swansea Dr. G. E. Farrow, Glasgow Dr. R. A. Fortey, London Dr. G. P. Larwood, Durham Dr. S. C. Matthews, Bristol Dr. I. E. Penn, London Dr. R. E. H. Reid, Belfast Dr. R. B. Rickards, Cambridge Dr. E. B. Selwood, Exeter Dr. G. D. Sevastopulo, Dublin Dr. P. Toghill, Church Stretton Overseas Representatives Australia'. Professor B. D. Webby, Department of Geology, Sydney University, Sydney, N.S.W., 2006 Canada '. Dr. B. S. Norford. Institute of Sedimentary and Petroleum Geology, 3303-33rd Street NW., Calgary, Alberta India'. Professor M. R. Sahni, 98 Mahatma Gandhi Marg, Lucknow (U.P.), India New Zealand'. Dr. G. R. Stevens, New Zealand Geological Survey, P.O. Box 30368, 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, University of California, Berkeley 4, California Eastern U.S. A. ; Professor J. W. Wells. Department of Geology, Cornell University, Ithaca, New York South America: Dr. O. A. Reig, Departamento de Ecologia, Universidad Simon Bolivar, Caracas 108, Venezuela Palaeontology VOLUME 20 PART 3 CONTENTS Cretaceous and Palaeocene species of the ostracod Hornibrookella from Saudi Arabia ALI A. F. AL-FURAIH 483 The evolutionary interpretation of the Foraminiferida Arenobulimina, Gavelinella and Hedbergella in the Albian of north-west Europe R. J. PRICE 503 Revision of the Ordovician carpoid family lowacystidae D. R. KOLATA, H. L. STRIMPLE and C. G. LEVORSON 529 A system of group names for some Tertiary pollen M. C. BOULTER and G. C. WILKINSON 559 A new Ricciisporites from the Triassic of Arctic Canada c. J. FELIX and p. p. burbridge 581 Associated dentition of the chimaeroid fish Brachymylus altidens from the Oxford Clay D. J. WARD and K. J. MCNAMARA 589 Bivalved arthropods from the Cambrian Burgess Shale of British Columbia D. E. G. BRIGGS 595 A new metazoan from the Cambrian Burgess Shale of British Columbia S. CONWAY MORRIS 623 An unusual bennettitalean leaf from the Upper Triassic of the south-western United States S. R. ASH 641 Additional late Silurian ostracoderms from the Leopold Formation of Somerset Island, North West Territories, Canada E. J. LOEFFLER and B. JONES 661 The Jurassic ammonite Bredyia Buckman J. R. SENIOR 675 Tooth function and succession in the Triassic reptile Procolophon trigoniceps G. E. GOW 695 A consideration of the tribe Thyrsoporelleae, dasyclad algae G. F. ELLIOTT 705 Printed in Great Britain at the University Press, Oxford by Vivian Ridler, Printer to the University Palaeontology VOLUME 20 PART 4 DECEMBER 1977 Published by The Palaeontological Association London THE PALAEONTOLOGICAL ASSOCIATION The Association publishes Palaeontology and Special Papers in Palaeontology. Details of member- ship and subscription rates may be found inside the back cover. PALAEONTOLOGY The journal Palaeontology is devoted to the publication of papers on all aspects of palaeontology. Review articles are particularly welcome, and short papers can often be published rapidly. A high standard of illustration is a feature of the journal. Four parts are published each year and are sent free to all members of the Association. 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 The Secretary, P.A. 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(for 1977): Fossil Priapulid Worms, bv s. c. morris. 159 pp., 99 text-figs., 30 plates. Price £16 (U.S, $32.00). © The Palaeontological Association, 1977 Cover: A Middle Jurassic megaspore, Minerisporites richardsoni (Murray) Potonie, from Oxfordshire ( x 350, S.E.M. by T. M. Windle). SOME LOWER CRETACEOUS CONIFERS OF THE CHEIROLEPIDIACEAE FROM THE U.S.A. AND ENGLAND by JOAN WATSON Abstract. Five species of Lower Cretaceous conifers assigned to the genera Pseudofrenelopsis Nathorst, Frenelopsis Schenk, and Cupressinocladus Seward of the family Cheirolepidiaceae are redescribed and figured with emended diagnoses. Lectotypes o{ P. parceramosa (Fonlame) comb, nov., P. vrrrwnj (Fontaine) comb, nov., and F. ramosissima Fontaine are selected from Fontaine’s figured specimens in the collection of the National Museum of Natural History, Smithsonian Institution. A specimen of F. alata (K. Feistmantel) from Texas is redescribed and compared with the Czechoslovakian type material and specimens from Portugal. The holotype of C. vaWeni'/.s (Seward) from the English Wealden is rediagnosed and its cuticle figured for the first time. P. varians and F. ramosissima are unlike any living conifer in having a very slender core of wood separated from a very thick cuticle by a wide, succulent cortex, indicating that these species were probably shrubby plants rather than large forest trees. They may have been quite small, salt- marsh plants. In the Lower Cretaceous of Europe, North America, Africa, and Asia there are several conifers distinguished by their smooth, cylindrical stems bearing minute leaves, often at long intervals and having a jointed appearance. Most of these have been placed in the genus Frenelopsis Schenk and attributed to the Cupressaceae. The type species of Frenelopsis was described by Ettingshausen (1852) as Fhuites hoheneggeri from the Carpathians. Schenk (1869) also describing material from the Carpathians, which he considered identical to Ettingshausen’s, removed it to a new genus, Frenelopsis, because he considered it to be closer to the living genus Frenela (now Callitris) than to Thuja. Schenk hgured several specimens which almost certainly included more than one species. Unfortunately none of Ettingshausen’s or Schenk’s specimens can be located. In recent years new Carpathian material has been collected (Reymanowna 1965) which also contains two conifers, one with leaves in alternating whorls of three and one with spirally arranged leaves. This three-leaved species has recently been used as the basis for a rediagnosis of the genus Frenelopsis Schenk and the type species F. hoheneggeri (Ettingshausen) (Reymanowna and Watson 1976). This new generic diagnosis (slightly emended) is repeated below. Subsequent to Schenk’s work a number of authors used F. hoheneggeri for material from many countries and about ten further species of Frenelopsis have been erected, though some of these are very unsatisfactory. Whilst revising the English Wealden flora (Watson 1964) I found shoots of a very similar-looking segmented conifer which, however, differs from F. hoheneggeri in bearing leaves one at a node and forming a simple spiral. I tentatively identified this as F. parceramosa Fontaine (1889) described from the Potomac Formation of the U.S.A. I have since been able to examine the type material in the Smithsonian Institu- tion and to confirm the identity of the English Wealden specimens. On the basis of the phyllotaxis a new genus, Manica (Watson 1974) was erected for species with [Palaeontology, Vol. 20, Part 4, 1977, pp. 715-749, Pis. 85-97.] 716 PALAEONTOLOGY, VOLUME 20 spiral leaf arrangement but otherwise resembling Frenelopsis. I have subsequently discovered that Nathorst (1893) erected a genus, Pseiidofrenelopsis, for shoots of such a species from the Lower Cretaceous of Mexico. Nathorst’s type species, P. felixi is now known to be identical to material from Glen Rose, Texas described as F. varians and Pagiophylhim dubium by Fontaine (1893, 1905). This is discussed below in detail but clearly Pseudofrenelopsis and Matuca are synonymous and the diagnosis given for the latter (Watson 1974) will now serve for Nathorst’s genus. Species of Frenelopsis and Pseudofrenelopsis are sometimes mixed in the same bed and because the leaves are so small may look much alike but are clearly distinguished by their cuticles. An intimate mixture of a Frenelopsis species and a Pseudofrenelopsis species is present in Lower Cretaceous silicified material from the Sudan (Edwards 1926; Watson in preparation). Reymanowna’s Carpathian material is now known to contain F. hoheneggeri (Ettingshausen) mixed with P. parceramosa (Eontaine) and it is highly probable that Schenk (1869) had the same mixture in his material. When describing Tlndtes hoheneggeri Ettingshausen (1852) also described specimens which he called Cuhnites prisons and regarded as a grass. Schenk (1869) transferred one of these specimens (Ettingshausen 1852, pi. 1, fig. 5) to F. hoheneggeri. It consists of two short jointed stems and it may be that C. prisons is what is now called P. parceramosa (Fontaine) but the figure and description of Ettingshausen do not provide enough information for a clear identification. Amongst English Wealden material of P. parceramosa from the Isle of Wight Dr. K. E. Alvin has found male cones which have yielded Classopollis Pflug pollen (to be described elsewhere). Classopollis has also been found by Fllustik and Konzalova (1976) in cones attributed to F. alata (K. Eeistmantel) and by Barnard (1968) and Barnard and Miller (1976) in cones attributed to Cupressinocladus pseudoexpansum Barnard and Miller. It therefore seems that these plants hitherto regarded as Cupres- saceae should be classified in the family Cheirolepidiaceae. It may be noted here that some authors prefer to use the family name Hirmeriellaceae as the genus Cheiro- lepidiuni Takhtajan ( = Choir olepis Schimper) is no longer in use, being a synonym of Hirmeriella Horhammer. In describing these jointed cheirolepidiaceous conifers certain difficulties arise in choosing terminology, mainly because the leaf and internode are continuous and the position of the node cannot be seen on the abaxial surface. Text-fig. 1 shows the terminology which is used below for describing the various species of Frenelopsis, Pseudofrenelopsis, and Cupressinocladus. Cupressinocladus, which Seward proposed as a form-genus, has whorls of leaves which extend downwards into broad decurrent bases separated by narrow grooves; these are called leaf-base cushions (text-fig. 16). Frenelopsis has no such grooves or sutures and consequently no separate basal cushions. The free leaves join laterally to form a cylindrical sheath below which the stem surface is a perfectly smooth cylinder and it seems best to call this internode (text-fig. Ifl). The node is taken to be the line along which the adaxial cuticle joins the base of the internode above and is more or less transverse. Pseudofrenelopsis with its different leaf forms presents further difficulties. Its leaves are one per node and normally have the base of the free part joined into a cylindrical sheath with smooth internode below and a transverse node as in Frenelopsis (text-fig. Ic; PL 85, fig. 4; PI. 89, fig. 2). In some shoots the leaf is equally broad but does not join into a cylinder JOAN WATSON: CRETACEOUS CONIFERS 717 and thus has a suture (PL 85, fig. 5; text-fig. \d). Generally in these ‘open’ leaves the internodes are short and the nodes oblique. In P. parceramosa from Portugal Dr. Alvin has seen leaves which are notched in the suture position but are cylindrical below the notch (Alvin 1977). Sometimes the edges of the ‘open’ type of leaf do not meet (text- figs. Ic, 2a) but have a gap filled by the base of the leaf above and in this form it resembles some kinds of BrachyphyUum. Clearly in describing these ‘open’ leaf forms it is convenient to use the terms internode and basal cushion interchangeably. FREE LEAF TIPS' FUSED LEAF BASES (sheathing cylinder) INTERNODE < iFREE LEAF TIP SHEATHING LEAF BASE ^ INTERNODE UNIT SEGMENT a) FRENELOPSIS c) PSEUDOFRENELOPSIS 'closed' type DECURRENT LEAF-BASE or LEAF-BASE CUSHION or INTERNODE b) CUPRESSINOCLADUS < d) PSEUDOFRENELOPSIS open' type with short suture e) PSEUDOFRENELOPSIS TEXT-FIG. 1 . Diagrammatic representations ol'disarticulated units of the various genera and the terminology used to describe them in the text. 718 PALAEONTOLOGY, VOLUME 20 The purpose of this paper is to redescribe five species from the Lower Cretaceous of the United States and England. They are P. parceramosa (Fontaine), P. varians (Fontaine), F. alata (K. Feistmantel), F. ramosissima Fontaine, and C. valdensis (Seward). Fontaine’s material was mostly collected last century from several localities in Virginia, Maryland, and Texas. Details of stratigraphic horizons are given with the description of each species. Stratigraphic relations of the Potomac Group localities in Maryland and Virginia are given by Doyle and Hickey (1976). Most of the American material is housed in the National Museum of Natural History, Smithsonian Institution but one specimen of F. ra/nu^mnnu (bearing a Smithsonian number) is in the Hunterian Museum, Glasgow University. A few of the figured specimens of Fontaine (1889, 1893) and Berry (1911) are missing but most are intact and as Fontaine did not designate holotypes I have selected lectotypes from them. The Glasgow specimen is not recognizable as one of the missing ones. The description of P. parceramosa includes figures of English specimens which are in the British Museum (Natural History). Specimen numbers with the prefix USNM are from the Smithsonian Institution, those bearing the letter V. from the British Museum (Natural History), and Pb. the Hunterian Museum, Glasgow. A duplicate set of slides made from American specimens has been deposited in the British Museum (Natural History) (numbers V. 58657- V. 58679) and examples of English P. parceramosa have been added to the Smithsonian collection. SYSTEMATIC DESCRIPTIONS Order coniferales Family cheirolepidiaceae (hirmeriellaceae) Genus pseudofrenelopsis Nathorst, 1893 1974 Manica Watson, p. 428. Emended diagnosis. Branching, segmented shoots bearing a simple spiral of leaves with sheathing bases, each individual leaf completely encircling the stem. Leaf small, triangular, obtuse, adpressed; usually joined laterally to form sheathing base con- tinuing as smooth cylindrical internode to node below; when not joined laterally internode short. Stoma circular having guard cells sunken below ring of subsidiary cells which form a stomatal pit. Type species. Frenelopsis varians Fontaine. 1893. Remarks. The diagnosis originally based only on the type species is emended here after studying specimens of F. varians Fontaine which is now transferred to this genus. The diagnosis of P. parceramosa (Fontaine) given below is based on information from American, English, Polish, and Portuguese material. Specimens from the Sudan which I have examined are in the form of silica moulds and have been studied by EXPLANATION OF PLATE 85 Figs. 1-7. Pseudofrenelopsis parceramosa (Fontaine). 1, lectotype. USNM 192360, x2. 2, 3, specimens showing branching, both with ‘closed’ kind of leaf-base or sheath. 2, USNM 192358, 3, USNM 192362, both X 1. 4, two long internodes showing stomatal rows and very small free leaf on the lower one. USNM 192393, x 3. 5, small macerated shoot showing ‘open’ kind of leaf and short sutures. V. 51543, X 10. 6, ‘closed’ leaf with very short internode or basal cushion. V. 51548, x 25. 7, adaxial cuticle with leaf margin at top, line of junction with next highest internode at bottom. V. 51549, x60. PLATE 85 WATSON, Pseudofrenelopsis parceramosa 720 PALAEONTOLOGY, VOLUME 20 means of silicone rubber casts (Watson and Alvin 1976). I have not used these for diagnostic purposes as they do not add any information but they seem to be specific- ally identical. Pseudofrenelopsis parceramosa (Fontaine) comb. nov. Plate 85, tigs. 1-7; Plate 86, figs. 1-12; Plate 87, figs. 1-10; text-figs. 2, 3 71852 Ciilmites prisms Ettingshausen, 24, pi. 1, fig. 5 (imperfect figure of what might possibly be a Pseudofrenelopsis shoot). 1889 Frenelopsis parceramosa ¥on\.‘d\nt,2\%,p\. Ill, figs. l-5;pl. 112, figs. l-5;pl. 168, fig. 1. 1905 Frenelopsis parceramosa Fontaine; Fontaine in Ward, 544 (name only in lists). 191 1 Frenelopsis parceramosa Fontaine; Berry, 425, pi. 70, figs. 1-5. 1926 Frenelopsis parceramosa Fontaine; Edwards, 97 (mentioned in comparison). 1940 Frenelopsis parceramosa Fontaine; Oishi, 390, pi. 40, figs. I, 5-8. 1946 Frenelopsis hoheneggeri (Ettingshausen); Romariz (pro parte), 143, pi. 2, figs. 1, 2; pi. 3, fig. 1, non pi. 1, figs. 1-3 ( - F. occidentalis). 1948 Frenelopsis hoheneggeri (Ettingshausen); Teixeira, 65, pi. 24, figs. 1-3. 1965 Frenelopsis hoheneggeri (Ettingshausen); Reymanowna (pro parte), 19, pi. 1, figs. 1, 3, 6; text-fig. 2a, c, e-m, non pi. 1, figs. 2, 4-5; text-fig. 2b, d, k ( = F. hoheneggeri). 1965 Manica parceramosa (Fontaine); Reymanowna, 23 (nomen nudum). 1974 Manica parceramosa (Fontaine) Watson, 428 (generic diagnosis and name change only). 1976 30 CHEIR MaA; Oldham, 462, pi. 72 (code no. used instead of specific name). 1976 Manica parceramosa (Fontaine); Reymanowna and Watson, 19. 1977 Manica parceramosa (Fontaine); Alvin, 397, pi. 44, figs. 1-8; text-fig. 3. Emended diagnosis. Branched shoots bearing leaves in 2/5 phyllotactic spiral. Triangular part of leaf up to 2 mm high, sheathing base up to 0-8 mm, borne at intervals of 1-11 mm (= internode length); twigs of variable width from 1 mm upwards, unrelated to distance between leaves. Thickly cutinized internode with stomata in well-marked longitudinal rows, uniseriate or imperfectly biseriate; 6-10 rows per mm; rows may continue on to abaxial surface of free leaf or may be absent. Leaf margin usually scarious and microscopically dentate, having unicellular, hollow teeth or hairs up to 80 /xm long. Stomatal apparatus typically 50-80 pin diameter with 5 or 6 (occasionally 4, rarely 7) more or less equal subsidiary cells; guard-cell apertures irregularly orientated. Stomata of a row often with subsidiary cells adjacent, rarely sharing a subsidiary cell. Subsidiary cells in different shoots varying from completely non-papillate to strongly papillate, papillae up to 13 pm long, solid or hollow. Perclinal walls of subsidiary cells as thick as ordinary epidermal cells, anti- clinal walls much narrower; ordinary epidermal cells forming ill-defined longitudinal rows, having broad, irregular anticlinal walls, 5-15 pm broad, unpitted. Total thick- ness of cuticle in mid-internode about 30 pm, much thinner at base where overlapped by and joined to adaxial cuticle of leaf below. Adaxial cuticle showing cells of variable shape and arrangement, often strongly papillate; few, scattered stomata, often abortive. Well-developed cutinized hypodermis of pitted, thin-walled cells except under stomatal apparatus; hypodermal cells isodiametric under stomatal rows, elongated under non-stomatal areas. Material and occurrence. Lectotype USNM 192360. This specimen was figured by Fontaine (1889) on plate 1 12, fig. 3. Of the specimens figured by Fontaine four remain in the Smithsonian Collection and there are two unfigured specimens. They are all extremely fragile and have probably lost numerous leaves since Fontaine JOAN WATSON: CRETACEOUS CONIFERS 721 described them. They were all collected from the same locality, Trent’s Reach, Virginia which has been dated on the basis of pollen and spore content as Barremian to Aptian (Doyle and Hickey 1976). There is also a very fine specimen (PI. 85, fig. 4) consisting of two internodes on a piece of borehole core from Louisiana. Information with it suggests that it is the same age as the Glen Rose Formation in Texas which is regarded as late Aptian to earliest Albian (see below under P. varians). The English Wealden specimens are nearly all fragments obtained by bulk maceration of coaly shales from several localities, notably Hastings, Sussex and Hanover Point, Isle of Wight. Oldham (1973, 1976) has found it throughout the Wealden succession (Berriasian to Aptian). P. parceramosa collected by Reymanowna (1965) is from the Grodisht Beds, Przenosza, SE. of Krakow which are Hauterivian-Lower Barremian in age. The Portuguese material (Alvin 1977) is Aptian- Albian. The Nubian Sandstone at Jebel Dirra, E. Darfur, Sudan, from which the silicified specimens were collected (Edwards 1926) is of uncertain age (Whiteman 1971, p, 54), but on the evidence of these conifers is presumably Lower Cretaceous. TEXT-FIG. 2. Pseudofrenelopsis parceramosa. a, small shoot with widely ‘open’ type of leaf, showing phyllotaxis, x20, V. 51542; B, single ‘open’ leaf unit showing dis- tribution of stomata, adaxial cuticle has few stomata, x25, V. 51544; c, scarious leaf margin showing hairs joined laterally, x 300, V. 51545. 722 PALAEONTOLOGY, VOLUME 20 Description. Despite the abundance of P. parceramosa obtained from the English Wealden little is known of the branching of this species. The matrix is extremely friable and though a few small hand specimens have been salvaged most of it was subjected to oxidative bulk maceration yielding only isolated segments (PI. 85, fig. 6) or short coherent lengths of shoot (PI. 85, fig. 5). Though few in number the Potomac specimens are much larger and there are two showing branching (PI. 85, figs. 2, 3) which appears to be alternate in one plane. I could not work out the phyllotaxis from any of the American specimens but using several small English shoots I have satisfied myself that it approximates to 2/5 divergence. The abundant English material has provided all the information about variation in size and leaf form. As would be expected the segments vary greatly in dimensions and doubtless represent large and small stems. The largest I have measured is 1 1 mm long x 6 mm wide but the pro- portions vary, e.g. 9 mm longx 3 mm wide; 4 mm long x 4 mm wide; 1-5 mm longx 3-5 mm wide. The ‘open’ type of segment described earlier occurs in both broad and narrow forms but is always comparatively short. Neither the variable widths nor ‘open’ and ‘closed’ segments have been seen in relation to each other in situ. The dentate margin of the leaf and sheath is developed to varying degrees. In some (text-fig. 2c) there is the appearance of hairs fused laterally to form a frill whereas others (PI. 86, figs. 2, 3) have well-developed individual hairs. Sometimes the scarious margin is scarcely developed at all. There is considerable variation in the details of the cuticle; mainly in the density of stomatal rows, papillae on subsidiary cells, papillae on ordinary epidermal cells, and the thickened ring formed by the outer surface of the subsidiary cells. The density of stomatal rows is dependent upon the number of biserial rows present and the number of cell rows between them. Plate 86, fig. 6 shows widely spaced uniserial rows; Plate 86, fig. 4 shows closely spaced uniserial rows; Plate 87, fig. 4 shows a closely spaced mixture of uniserial and biserial; and Plate 86, fig. 5 a widely spaced mixture. Oldham (1973, 1976) has found that the presence of papillae on ordinary epidermal cells increases markedly with decreasing geological age but at present I can see no such age relationship to the presence or absence of subsidiary cell papillae. All the American specimens have well-developed papillae on the subsidiary cells (PI. 86, figs. 7-9, 11; PI. 87, fig. 5) as do all the Isle of Wight specimens inspected. Alvin (1977) has seen only non-papillate subsidiary cells in the Portuguese specimens but EXPLANATION OF PLATE 86 Figs. 1-12. Psendofrenelopsis parceramosa (Fontaine). All scanning electron micrographs. 1, triangular free leaf showing strongly papillate surface, marginal hairs and sparse stomata in lower part only. V. 58655, X 60. 2, 3, part of leaf sheath showing marginal hairs and extent of stomata. USNM 192358, 2, X 100, 3, x250. 4-6, internode outer surface showing variation in density of stomatal rows and in form of stoma. 6, showing individual epidermal cells outlined by grooves. 4, USNM 192393, 5, USNM 192358, 6, USNM 192362, all x 100. 7-9, stomata showing subsidiary cell papillae and differences in development of thickened ring and surrounding furrow. 7, USNM 192362, 8, USNM 192358, 9, USNM 192393, all x 1000. 10, silicone rubber cast of stoma from silicified Sudanese material, showing similarity to type of stoma in fig. 8. V. 21708, x 1000. 11, 12, two stomata each with a subsidiary cell papilla inside the stomatal pit. 12, in vertical section. 11, USNM 192363, 12, USNM 192360, both x 1000. PLATE 86 WATSON, Pseudofrenelopsis parceramosa 724 PALAEONTOLOGY, VOLUME 20 was able to sample only two internodes. In the Hastings material such papillae may be present or absent and I was able to study the variation in numerous isolated segments. There is also variation in the occurrence of papillae on ordinary epidermal cells. I found as a general rule that segments with short internodes (less than 3 mm) have papillate subsidiary cells (text-fig. 3a), whilst those with internodes over 5 mm long have non-papillate subsidiary cells (text-fig. 3b; PI. 87, fig. 6). Internodes A TEXT-FIG. 3. Cuticle of internode of Pseudofrenelopsis parceramosa. a, cuticle of a small unit with papillate subsidiary cells, V. 51546; b, cuticle of a larger unit with non-papillate subsidiary cells, V. 51547. Hypodermal cells shown by dotted lines. Both x 300. EXPLANATION OF PLATE 87 Figs. 1-10. Pseudofrenelopsis parceramosa (Fontaine). 1-3, 8-10, scanning electron micrographs. 1, 2, inner surface of internode cuticle showing stomatal rows. 2, shows a Flastings specimen in which the extensive cutinized hypodermis obscures the ordinary epidermal cells. V. 58654, x250. 1, a Potomac specimen clearly shows the epidermal cells with only a few pitted hypodermal cells. USNM 192363, x 250. 3, inner surface of a single stoma showing five subsidiary cells, cutinized part of guard cells and stomatal aperture. Subsidiary cell on left shows the entrance of a hollow papilla and the striated ridge which is related to the deep furrow surrounding the stoma on the outer surface. USNM 192363, x 1000. 4, 5, internode cuticle of lectotype showing typical appearance in light microscope. 4, shows both uniseriate and biseriate rows of stomata, x 100. 5, is a single stoma with strongly papillate subsidiary cells, x 500, USNM 192360. 6, internode cuticle of Hastings specimen with non-papillate subsidiary cells, showing two stomata sharing a subsidiary cell. V. 58656, x 400. 7, long, hollow epidermal hair near base of internode of lectotype. USNM 192360, x 500. 8, outer surface of adaxial cuticle with long hairs pointing towards leaf apex. V. 58654, x250. 9, 10, inner surface of adaxial cuticle. 9, showing stoma on left, x250. 10, showing an abortive stoma, x 500. V. 58654. PLATE 87 WATSON, Pseudofrenelopsis parceramosa 726 PALAEONTOLOGY, VOLUME 20 between 3 and 5 mm long may be of one kind or the other or have mixed stomata. On the whole the cell size and, therefore, stomatal diameter, are smaller in non- papillate ones (cf. text-fig. 3a, b). Many of the smallest segments have a solid, central papilla on the surface of the ordinary epidermal cells, occasionally on all cells but more commonly near the base of the leaf cushion only. The longer internodes, parti- cularly those with non-papillate subsidiary cells mostly lack these other papillae too except on the free leaf tip where both abaxial (PI. 86, fig. 1 ) and adaxial (PI. 87, fig. 8) surfaces may have strongly developed papillae or hairs. Only on the lectotype have I found long hairs such as in Plate 87, fig. 7 near the base of the internode (cf. P. varians below). Other variations encountered in the stomata are illustrated in Plate 86. For example, Plate 86, fig. 4, shows the most usual form of stoma with a broad, raised rim surrounding the stomatal pit, the rim in turn surrounded by a deep groove. This groove is related on the inside surface of the cuticle to a raised ridge which frequently has radial striations (PI. 87, fig. 3). Plate 86, figs. 8 and 10 show stomata where the rim and furrow are much less pronounced. Figure 10 is a silicone rubber cast of the silicified material from the Sudan. This type of stoma is fairly common scattered amongst the usual kind in the Potomac and Sudanese specimens but I have never seen such a stoma in an English specimen. It will also be noted that the subsidiary cell papillae vary in their position in relation to the stomatal pit, either at the top (PI. 86, fig. 8), slightly below the top and bounded by a groove (PI. 86, fig. 9), or occasionally even half-way down the stomatal pit (PI. 86, figs. 11, 12). I think it worth pointing out that I was completely unaware of these subtle differences when studying cuticle preparations with the light microscope and became aware of them only after SEM work. In the light microscope (PI. 87, fig. 4) the cuticle of P. parceramosa is extremely distinctive and, I find, easy to identify. Plate 86, figs. 6 and 7 show an unusual feature where the outline of each epidermal cell is marked by distinct furrows and the surface is pitted. Dr. Alvin has seen the same feature in a specimen of Frenelopsis alata from Portugal (Alvin 1977) and we think it is a preservational feature perhaps reflecting loss of surface wax. The hypodermis of P. parceramosa is particularly well developed and in the SEM often obscures details of the epidermal cells (PI. 87, fig. 2). Its distribution is best illustrated in text-fig. 3a. Comparison. The only other fossil conifer I know which matches P. parceramosa in having a leaf which completely encircles the stem is P. varians (Fontaine) which is described and compared below. Pseudofrenelopsis varians (Fontaine) comb. nov. Plate 88, figs. 1 -9; Plate 89, figs. 1,2; Plate 90, figs. 1-13; Plate 91, figs. 1-13 1893 Frenelopsis varians Fontaine, 273, pi. 40, figs. 1-2; pi. 41, figs. l-3a. 1893 Pagiophylhtm diibiwn Fontaine, 271, pi. 39, figs. 2-11. 1893 Pseudofrenelopsis felixi Nathorst, 52, text-figs. 6-8. Emended diagnosis. Branched shoots bearing leaves in simple spiral. Free tip of leaf up to T5 mm high, sheathing base up to 0-8 mm; leaves borne at intervals of T5- 17 0 mm ( ^ internode length); shoots of 3-7 mm wide. Internode cuticle extremely JOAN WATSON: CRETACEOUS CONIFERS 111 thick, varying from 50 to 110 /xm in total thickness; outer periclinal wall of subsidiary cell forming almost all this thickness; outer periclinal wall of ordinary cells forming half to three-quarters of total thickness; euticle much thinner at base of internode where overlapped by leaf below. Stomata seattered in smooth, cylindrical internodes; arranged in uniseriate rows in short internodes where leaf does not join laterally, stomatal rows 8-10 per mm; stomata continuing on to abaxial surface of free leaf but not on to leaf sheath. Leaf margin scarious and microscopically dentate, teeth up to 60 jixm long. Stomatal apparatus varying from 70 to 100 /xm diameter except in extreme basal part of internode where they are much smaller; having 5 to 8 (rarely 4 or 9) subsidiary cells. Guard cells at bottom of deep, parallel-sided stomatal pit formed by extremely thick cuticle of subsidiary cells; aperture randomly orientated. Outer surface of subsidiary cells forming raised rim bounded by deep groove around top of stomatal pit; each cell having hollow papilla overarching pit. Anticlinal walls of subsidiary cells 2-3 /xin broad; those of ordinary epidermal cells 5-6 /xm broad with thickened corners giving rounded lumen; cells haphazard or in short files amongst seattered stomata; in long uninterrupted files between rows of stomata. Each epidermal cell bearing on outer surface a distinct, acutely pointed hair up to at least 80 /xm long. Cutinized hypodermis present (seen only in ‘open’ leaf-base cushions) except under stomatal apparatus; hypodermal cells square under stomatal rows, elongated between stomatal rows; anticlinal walls 1 /xin broad. Female cones nearly round (largest 18 mm longx 16 mm wide), surface showing probably 3 /5 para- stiehies of rhomboidal scale ends (no inner parts known) ; borne on a stalk resembling smaller vegetative stems. Wood forming slender core, less than one-third total width of shoot. Material. Lectotype USNM 192381, figured by Fontaine (1893), plate 41, fig. 3, 3a. The Smithsonian Collection contains all Fontaine’s figured specimens of P. varians together with a number previously unfigured. They were all collected from the Trinity Group of the Lower Cretaceous at Glen Rose, Texas where they occur in the Glen Rose Limestone together with an abundant marine fauna. The Glen Rose Formation is considered to be late Aptian to earliest Albian (Stephenson et al. 1942), Description. The specimens now described as P. varians (Fontaine) were separated by Fontaine into two distinct species, F. varians and Pagiophyllum dubiuin. He attributed all the female cones to P. duhium. In his account Fontaine (1893, p. 274), describing the leaves of one specimen of F. varians, points out how they ‘. . . strikingly resemble the leaves at the summit of the cone-bearing twigs of Pagiophyllum duhiinn . On examination of the cuticles it is immediately obvious that they are different leaf forms of a single species. At the same time as Fontaine was describing this material from Texas, Nathorst (1893) was unknowingly describing the same plant from Mexico under another name. Nathorst compared his specimens to F. parceramosa Fontaine, suspecting that they were the same species and at the same time mildly criticizing Fontaine for describing the F. parceramosa specimens as articulated. Not wishing to use the genus Frenelopsis for shoots other than those with leaves in whorls of three or four Nathorst erected a new genus, Pseudofrenelopsis, with the Mexican specimens as a new species, P. felixi. Fontaine (1905) in correcting the criticism about the jointed nature of F. parceramosa pointed out that Nathorst’s P. felixi was identical to his own 728 PALAEONTOLOGY, VOLUME 20 Pagiophylhim dubium from Texas, i.e. what is now the ‘open’ leaf form of Pseudo- freuelopsis varians. I think Fontaine was correct, notwithstanding the absence of the Mexican specimens and details of their cuticle. In joining these species I have chosen to retain the specific epithet varians because shoots given that name by Fontaine more clearly typify the species and include the lectotype. There are only two branching specimens in the collection (PI. 88, fig. 1 ; PI. 89, fig. 1 ), both are strikingly jointed with a stiff, sparsely branched appearance. All the other specimens are lengths of shoot of up to a dozen segments (PI. 88, figs. 2-6) or short lengths of shoot bearing a cone (PI. 88, figs. 7-9). As with P. parceranwsa there is no specimen which shows the ‘closed’ and ‘open’ leaf forms together on the same shoot. However, both long and short segments are present in specimen USNM 192378 (PI. 89, fig. 1) on the lowest right-hand branch which has segments of variable length in the lowest part, long segments in the middle with an abrupt change to short, narrow segments in the distal region. As noted by Fontaine, the shoots in their smallest form are very like those of P. parceramosa. The small leaves below the cones are of either the ‘closed’ or ‘open’ variety but not mixed as far as I can tell. The cuticle of these small leaves (PI. 90, fig. 11) easily identifies the cones as belonging to P. varians. Variation in details of the cuticle is chiefly associated with differences in the epidermal hairs. The long cylindrical internodes have, in the main, short sharply pointed hairs (PI. 90, figs. 2, 5) or the eroded remains of such hairs (PI. 90, fig. 6). In the basal region of some internodes patches of considerably longer hairs occur (PI. 91, figs. 11, 12). The epidermal hairs of the ‘open’ leaf type are often densely packed (PI. 91, fig. 10) particularly on the free part of the leaf (PI. 90, figs. 8, 9) where they tend to join laterally and point towards the apex. There is little variation in the external appearance of the stoma which is usually as seen in Plate 90, fig. 7 but occasionally the thickened rim has the form of a low cone as seen in Plate 90, fig. 5. The long, wide internodes consistently contain a very narrow cylinder of wood (PI. 89, fig. 2) separated from the cuticle by a wide gap where all the tissue has vanished, I imagine because it was parenchyma. Several of the internodes have numerous small holes puncturing the cuticle (PI. 91, fig. 13) which were clearly made when the plant was living because they have a callus around them. It seems to me quite likely that they were made by the proboscis or ovipositor of an insect, either to suck at the juicy tissue below or to lay eggs in it. EXPLANATION OF PLATE 88 Figs. 1-9. Pseudopxmelopsis (Fontaine). 1, lectotype showing jointed, sparsely branched appearance, with long cylindrical internodes. USNM 192381, X 1. 2-4, short lengths of shoot with the 'open' type of leaf. 3, cone probably not attached. 2, USNM 192364, x 1, 3, USNM 192371A, x 1, 4, USNM 192365, X 2. 5, 6, shoots with ‘closed' type of leaf but much shorter internodes than lectotype. 5, shows very small free leaves in 5th and 6th segments from bottom, USNM 192380, x 2. 6, is a shoot apex and shows a free leaf on the 3rd segment up, USNM 192379, x3. 7-9, female cones attached to short lengths of shoot which have been identified by their cuticle. 7, USNM 192368, 8, USNM 192367, 9, USNM 192376, all x 1. PLATE 88 i r • ; Jr •f>| WATSON, Pseudofrenelopsis various 730 PALAEONTOLOGY, VOLUME 20 Comparison. There is a strong superficial resemblance between some shoots of P. various and P. parceramosa (cf. PL 85, fig. 1 and PI. 88, fig. 5) but they are easily separable on cuticle differences which are summarized in Table 1. The fragmentary shoots of P. parceramosa which abound at Hanover Point, Isle of Wight are intimately associated with considerable amounts of fossil wood and the cliff section is only a matter of metres away from the famous ‘pine-raff on the foreshore. Any relation- ship between wood and leafy shoots has yet to be established but clearly there are indications that P. parceramosa may have been a sizeable tree. On the other hand, the very small size of the stele in P. varians, about one-quarter of the total diameter of the shoot, leads me to suppose that it was not a tree at all but a small shrub. This is further discussed below in comparison with F. ramosissima. Genus erenelopsis Schenk 1869 1976 Frenelopsis Schenk; Reymanowna and Watson, 19. Diagnosis (slightly emended after Reymanowna and Watson). Branching, articulated shoots consisting of cylindrical internodes each extending at the upper margin into a whorl of equal, scale-like, adpressed, triangular leaves (usually three, sometimes two); successive whorls alternating; internode surface smooth, showing no grooves or sutures. Stomatal apparatus circular, monocyclic, or incompletely amphicyclic, having guard cells sunken below a ring of subsidiary cells which form a stomatal pit. Type species. Thuites holie)ieggeri EUmgshinisen 1852, 26. Remarks. The diagnosis above is slightly emended because shoots with two leaves per node have recently been found. These are at present being studied (Pais, Alvin pers. comm.) and do not match any known species, but they lack the sutures of Cupressinocladus so will be included in Frenelopsis. So far there is no evidence of both two-leaf and three-leaf whorls in one species, contrary to expectation. Frenelopsis alata (K. Feistmantel) Knobloch Plate 89, figs. 3, 4; Plate 92. figs. 1-9 Selected synonomy: 1881 Sclerophyllum alatum K. Feistmantel, 96, pi. 7, fig. \a-k. 1888 Frenelopsis hohemica Velenovsky, 590, pi. 1, figs. 1, 2, 10. 1893 Frenelopsis lioheneggeri (Ettingshausen); Fontaine, 275, pi. 42, fig. 4, Aa. 1926 Frenelopsis hohemicaVelenovsky 133, pi. l,figs. 1-3; pi. 2, figs. 1-5; pi. 3, figs. 1-4. 1946 Frenelopsis hisitanica Romariz, 144, pi. 3, figs. 2, 3; pi. 4, figs. 1, 2. EXPLANATION OF PLATE 89 Figs. 1, 2. Pseudofrenelopsis varians (Fontaine). 1, branched specimen showing variable internode length, particularly on lowest, right-hand branch. USNM 192378, x 1. 2, portion of long cylindrical internode showing free leaf (slightly eroded) at back left, and the slender core of wood. USNM 192371 A, x8. Figs. 3, 4. Frenelopsis alata (K. Feistmantel). Branched specimen with only one intact whorl of leaves which is shown in fig. 4. The position of this whorl is indicated by the arrow on fig. 3, and a dotted line in fig. 4. USNM 3750, 3, x 1, 4, x6. PLATE 89 WATSON, Pseudofrenelopsis, Frenelopsis 732 PALAEONTOLOGY, VOLUME 20 1971 Frenelopsis alata (K. Feistmantel) Knobloch, 44 (name change only). 1972 Frenelopsis alata (K. Feistmantel); Hlustik, 210. 1974 Frenelopsis alata (K. Feistmantel); Hlustik, 265, pi. 1, figs. 3, 4; pi. 3, figs. 1, 2. 1976 Frenelopsis alata (K. Feistmantel); Hlustik and Konzalova, 38, pis. 1-6 (description of male cone). 1977 Frenelopsis alata (K. Feistmantel); Alvin, 388, pi. 41, figs. 1-5; pi. 42, figs. 1-6; text-fig. 1a. Material. USNM 3750. The lectotype is in the National Museum, Prague, Czechoslovakia. Description. Only one specimen of this species (PI. 89, figs. 3, 4) is present in the Smithsonian Collection. It is from Glen Rose, Texas and was found amongst specimens of P. varians (Fontaine). Only one node shows well-preserved leaf arrange- ment (PI. 89, fig. 4; Fontaine 1893, pi. 42, fig. Aa) and this is clearly a whorl of three. Fontaine states that the leaves in successive whorls alternate but I certainly could not verify this on examining the specimen. However, this feature has been clearly estab- lished in European specimens. The free leaf was not sampled and the description below is based on only two slide preparations and one SEM preparation from the internode. Also I was unable to ascertain whether the leaf is bordered by a fringe of hairs as are all the other species of Frenelopsis and Pseudofrenelopsis I have examined. The specimen is branched but the details are not clear. As far as I can tell the segments are 1 •5-2-0 cm long and 3-5-5-0 mm wide. The free leaf tip is about 1-0 or 1-2 mm high but I do not know the extent of the leaf sheath. The leaves show a distinct series of ridges and furrows radiating from the apex (PI. 89, fig. 4), a feature commonly seen in specimens of Frenelopsis. The epidermis of the internode has stomata in fairly ill-defined uniseriate rows with 10 or 12 rows per mm and with 1-4 rows of ordinary epidermal cells between the stomatal rows. Within a row the individual stomata are irregularly spaced. The diameter of the stomatal apparatus varies from 52 to 77 p,m and most have 5 subsidiary cells though sometimes 4 or 6. The form of the stomatal pit is highly distinc- tive (PI. 92) having a stellate opening (up to 20 ixm across) which is formed by a lobed canopy arching over the pit. The number of lobes appears to equal the number of subsidiary cells. Half-way down inside the pit is a ring of large, hollow papillae again equal in number to the subsidiary cells. On the outer surface the canopy is sur- rounded by a deep furrow (PI. 92, figs. 3, 9). The guard cells are very thinly cutinized EXPLANATION OF PLATE 90 Figs. 1-13. Pseudofrenelopsis varians (Fontaine). All scanning electron micrographs. l,part of long internode showing scattered stomata. USNM 192383, x 25. 2, part of same showing epidermal papillae, marginal hairs, and absence of stomata from leaf sheath, x 100. 3, long hairs of leaf sheath margin. USNM 192383, X 500. 4, transverse section of internode showing extreme thickness of cuticle. USNM 192383, x 100. 5, surface of internode with short epidermal papillae and cone-shaped rim of stomatal pit. USNM 192380, X 100. 6, 7, surface of internode with severely eroded papillae and ring of thickening around stomatal pit. USNM 192378, 6, x 100, 7, x 1000. 8, ‘open’ type of leaf with stomata in rows, showing difference in papillosity between internode (lower half) and free leaf. USNM 192371 A, x25. 9, ‘open’ leaf with papillae joined in rows and pointing towards apex, stomata somewhat stunted. USNM 192364, x250. 10, stoma from mid-internode of a specimen with strongly developed pointed papillae and hairs. The base of this specimen is seen in Plate 91, figs. 11, 12. USNM 192378, x 500. 11, 12, ‘open’ scale-leaf from below female cone. The cuticle is very similar to that in fig. 10. USNM 192372, II, x250, 12, x25. 13, outer surface of adaxial cuticle. USNM 192378, x 250. PLATE 90 WATSON, Pseudofrenelopsis varians 734 PALAEONTOLOGY, VOLUME 20 and did not survive maceration but Dr. Alvin has seen some in Portuguese specimens and thinks they are randomly orientated. Plate 92, figs. 4 and 5 show the absence of guard cells so that the papillae inside the stomatal pit are clearly seen. Plate 92, fig. 5 shows that these papillae are hollow. The cells immediately surrounding the sub- sidiary cells tend to form a definite ring and occasionally a stoma has a cell which appears to be a genuine encircling cell. The other ordinary epidermal cells are arranged in irregular longitudinal files and may be rounded, squarish, or slightly elongated ; they are 25-50 fxm long and 20 ixm wide with anticlinal walls 3-6 /xm broad. The inner surface of the periclinal walls is often finely sculptured (PI. 92, figs. 6, 7) but the outer surface (PI. 92, fig. 1) is quite smooth with no hint of papillae. There is a cutinized hypodermis of pitted, very thin-walled cells, elongated between stomatal rows, squarish within the stomatal rows, often slightly overlapping the subsidiary cells (PI. 92, fig. 5). The total thickness of the internode cuticle is about 40 i^m (measured on SEM photographs). Discussion and comparison. I have examined the cuticle of the Portuguese material assigned to F. alata by Alvin (1977) and compared it with USNM 3750 and it seems to me that they are specifically identical. The Portuguese specimens are known to be Cenomanian whereas the Texas specimen can only be early Albian at the youngest. Hlustik (1974) has figured the cuticle of Czechoslovakian F. alata and comparing his light micrograph (pi. 1, fig. 3) to the cuticle of USNM 3750 I can see only minor differences such as slightly shorter epidermal cells. His scanning electron micro- graphs show only the inner surface of the cuticle with guard cells intact so that I can- not tell if the stoma has the same distinctive structure as described above. However, Hlustik has examined Alvin’s photographs of Portuguese F. alata and is satisfied that the determination is correct. The silicified Frenelopsis from the Sudan (Watson and Alvin 1976) has stomata closely similar to those of F. alata but studying them only as silicone rubber casts it is difficult to be certain whether or not they are the same species. EXPLANATION OF PLATE 91 Figs. l-Xl). Pseudofrenelopsisvarians(¥on\.a.im). 1-4, 6, 7, 12, are scanning electron micrographs. 1,2, cuticle in section showing tubular stomatal pits with papillae at top and cutinized guard cells at bottom. 2, shows that the cuticle of the subsidiary cell is twice as thick as that of the adjacent epidermal cell. USNM 192378, 1, x250,2, x 500. 3, vertical section of thickest cuticle sampled (over 100 f^m), inside uppermost. USNM 192380, x400. 4, inner surface of internode cuticle with scattered stomata. USNM 192380, X 100. 5, light micrograph of internode cuticle, outside uppermost. USNM 192378, x 100. 6, inside of cuticle showing guard cells and hypodermal cells, USNM 192380, x250. 7, stoma with eight sub- sidiary cells showing small lumen compared to other epidermal cells. USNM 192380, x400. 8, stoma outside uppermost showing subsidiary cell papillae. USNM 192378, X 500. 9, stoma inside uppermost showing aperture and that stomatal pit is fluted in section. USNM 192378, x 500. 10, cuticle of ‘open’ leaf-cushion with papillae more prominent than stomata. USNM 192371 A, x 100. 11, 12, light and scanning micrographs of the same internode with very long epidermal hairs at base. USNM 192378, both x 100. 13, possible insect bites in cuticle. USNM 192378, x 100. PLATE 91 WATSON, Pseudofrenelopsis varians 736 PALAEONTOLOGY, VOLUME 20 The same basic type of stoma with papillae inside the pit occurs in several other species of Frenelopsis and also in Cupressinocladus valdensis but they all have differences in external details of the pit opening. F. oligostomata Romariz from Portugal (Alvin 1977) has a thick ring around the pit entrance and rather short papillae inside. F. hoheneggeri (Ettingshausen) from Poland (Reymanowna and Watson 1976) has a stellate pit opening surrounded by large pouch-like papillae; the papillae inside the pit are large and obscure the guard cells. F. occidentalis Heer from Portugal (Alvin 1977) also has very large papillae in the pit but the pit opening is flush with the smooth outer surface. This is very similar to the stoma of C. valdensis (Seward) described below. F. ramosissima Fontaine is the only species of Frenelopsis I have seen without this kind of stoma. Frenelopsis ramosissima Fontaine Plate 93; Plate 94, figs. 1-5; Plate 95, figs. 1-4; Plate 96, figs. 1-10; Plate 97, figs. 1-5 1889 Froielopsis ramosissima Fontaine, 215, pis. 95-99; pi. 100, figs. 1-3; pi. 101, fig. 1. 1910 Frenelopsis ramosissima Fontaine; Berry, 305, text-figs. 1, 2. 1911 Frenelopsis ramosissima Fontaine; Berry, 422, pis. 71, 72. Emended diagnosis. Fateral branches profusely branched in one plane, bearing leaves in whorls of three. Triangular part of leaf up to 2-0 mm high, sheathing base up to 0-5 mm; leaf margin dentate, teeth up to 100 [xm long. Thickly cutinized internodes with stomata occurring roughly in longitudinal rows, irregularly spaced within rows; rows close together in ultimate branches (10-12 per mm), widely spaced (one per mm) and less well defined in older orders of branching; few stomata present on free leaf. Stomata with 4-6 (usually 5) subsidiary cells; diameter of stomatal apparatus 50-75 ;um; guard cells at bottom of shallow pit, apertures tending to be horizontally orientated. Outer surface of subsidiary cells forming thickened rim around stomatal pit, lobed or with papillae (one per subsidiary cell) overhanging pit, rim bounded by distinct groove. Outer surface of each ordinary epidermal cell bearing a papilla or hair, up to 120 fxm long; ordinary epidermal cells with thin periclinal walls, arranged roughly in files, often wider than long in older branching orders. Material and occurrence. Lectotype USNM 192385, figured by Fontaine (1889), plate 96, fig. 2. There are about twelve specimens remaining in the Smithsonian Collection, all from Fredericksburg, Virginia though Fontaine and Berry listed other localities. It seems probable that at least some of the missing specimens were exchanged with other museums many years ago. EXPLANATION OF PLATE 92 Figs. 1-9. Frenelopsis alata (K. Feistmantel). 1, 3-5, 8, 9, scanning electron micrographs. All USNM 3750. 1, outer surface of internode cuticle. x250. 2, light micrograph of internode cuticle showing stomatal arrangement, x 100. 3, cuticle tilted at 60° to show stoma in vertical section. x250. 4, inner surface of internode cuticle. Note that guard cells are not preserved, x 250. 5, single stoma showing openings to hollow papillae in stomatal pit. The papillae can be clearly seen here because the guard cells are absent. X 500. 6, stoma in high plane of focus to show stellate opening to stomatal pit. x 500. 7, same stoma in low plane of focus showing large papillae inside stomatal pit. x 500. 8, outer view of single stoma showing pit papillae below the lobed canopy. X 1000. 9, vertical section of a stoma. X 1000. PLATE 92 ww A r • WATSON, Frenelopsis alata 738 PALAEONTOLOGY, VOLUME 20 Localities. Fredericksburg, Virginia and Federal Hill (Baltimore), Maryland which are both lower Albian (Doyle and Hickey 1976); Chinkapin Hollow, Virginia is probably Doyle and Hickey Zone I (Barremian- lower Albian) but has not yielded pollen for dating (Hickey pers. comm.). Description. The Fredericksburg locality produced a profusion of handsome specimens and though many are missing the larger ones remain (PI. 93 and PI. 94, fig. 2) together with some lengths of wide stem (PI. 94, fig. 1). Thus it has been possible to sample the cuticle more extensively than in any of the other species. The cuticle of F. ramosissima is immediately distinguishable from other species by its epidermal papillae and hairs which may be extremely long; Plate 96, fig. 10 shows them at their smallest and Plate 97, fig. 2 at their longest. Plate 97, figs. 1-4 show the cuticle of four of the five orders of branching of the Glasgow specimen (PI. 95, fig. 1); fig. 1 is the oldest and fig. 4 the youngest. The third order is not shown as it is closely similar to the second (fig. 2). I have not seen any long hairs in the youngest segments and clearly there is a distinct trend towards longer hairs in the older orders with some mixing of different lengths. The rim around the stomatal pit is somewhat variable. The subsidiary cells may each have a well-developed papilla overhanging the stomatal pit (PI. 96, fig. 5 and PI. 97, fig. 4). Usually I found these in the youngest segments with dense stomatal rows and small epidermal cell papillae. Plate 97, fig. 2 shows stomata where the subsidiary cell papillae are less strongly developed and do not overhang the pit, and Plate 96, fig. 4 shows the rim as a gently undulating ring. This type of stoma is usually found in the older segments with widely spaced stomata and long epidermal hairs. However, these combinations of characters are not consistent : Plate 96, fig. 10 shows a young segment with scarcely any epidermal papillae and a lobed stomatal rim. The specimen in Plate 94, fig. 1 is of especial interest because this is a stem 2 cm in diameter with persistent cuticle and there are similar specimens with persistent leaves (Fontaine 1889, pi. 96, fig. 3). The epidermal cells of this specimen are consider- ably elongated horizontally with a somewhat stretched appearance, but in places there is clear evidence of continuing cell division, mostly in a vertical plane (text- fig. 4). The stomata are very widely spaced (one row per mm) but are in no way distorted and around the stomatal apparatus there is both vertical and horizontal cell division. On the outer surface the SEM shows the epidermal papillae widely separated in sinuous tracts with smooth areas between (PI. 97, fig. 5). I assume that the papillae were present on the original cells and that the smooth areas, which show stretch-marks, are where most of the new cells have been intercalated to facilitate expansion in diameter of the stem without rupturing the epidermis. Fontaine’s account of this plant (1889, pp. 215-218) indicates that F. ramosissima had very little woody tissue. He reports seeing the woody axis in the form of jet ‘always much smaller than the tube of epidermis which incloses it’. He suggested that the stem originally had a ‘thick succulent cortical layer’ and quite commonly found ‘the shrunken remains of the twigs lying in molds which are now considerably larger than themselves, and which they evidently once filled’. EXPLANATION OF PLATE 93 Fig. I. Frenelopsis ramosissima Fontaine. The lectotype. USNM 192385. xf. PLATE 93 WATSON, Frenelopsis ramosissima 740 PALAEONTOLOGY, VOLUME 20 TEXT-FIG. 4. Cuticle of the wide stem of Frenelopsis ramosissima in Plate 94, fig. 1 showing horizontally elongated cells with continuing cell divisions in horizontal and vertical planes; stomata now widely isolated from one another but undistorted; a few epidermal papillae can be seen. Comparison. Clearly F. ramosissima was rather similar in morphology and habit to Pseudofrenelopsis varians, as well as in surface features of the epidermis. However, they differ considerably (see Table 1) in their branching, leaf number per node, cuticle thickness, and, of course, they have not been found in association. The stoma of F. ramosissima, unlike all other species of Frenelopsis I have seen, does not have papillae inside the stomatal pit and is much more like that of P. parceramosa. Frenelopsis and the very similar Pseudofrenelopsis differ strikingly in the aspect of their shoots from any living conifer. Particularly F. ramosissima and P. varians seem much more like some stem succulent dicotyledon, such as Salicornia of the Cheno- podiaceae. Salicornia flourishes on marshes where the soil is loaded with sodium chloride or sodium carbonate. The predominance of Classopollis pollen in coastal, marine sediments of the Jurassic and Cretaceous has led to the suggestion that the plants bearing this pollen may have been stilt-rooted mangrove species (Hughes and Moody-Stuart 1967) or dominant on the seaward margin of lowland forests (see EXPLANATION OF PLATE 94 Figs. 1-5. Frenelopsis ramosissima Fontaine. 1, the widest stem in the collection. This specimen has cuticle which shows the continuing cell division of the epidermis, seen in text-fig. 4. USNM 192387, X 1. 2, 3, pro- fusely branched specimens with fairly long internodes, photographed dry. 2, USNM 192388, x 1, 3, USNM 192390, x 1. 4, 5, unexpanded shoots with short internodes, crowded branching, and bud- like tips. 4, USNM 192386, 5, USNM 192391, both x 1. PLATE 94 WATSON, Frenelopsis ramosissima 742 PALAEONTOLOGY, VOLUME 20 Hughes 1976, p. 37). Vachrameev (1970) favours an upland habitat and Batten (1974) has reconstructed several alternatives including those above. Current work continues to link more plants with ClassopoUis (Archangelsky 1968; Lorch 1968; Hlustik and Konzalova 1976; Barnard and Miller 1976) and it is now clear that the family Cheirolepidiaceae includes a wide variety of shoot types. It may well be that its members also exhibited a much wider range of habitat than has hitherto been supposed and some of them, such as P. varians and F. ramosissima, may have been low, coastal succulents and even salt-marsh inhabitants (Jung 1974). Dr. S. Baksi and Professor P. Allen (pers. comm.) have found, in situ, a small Frenelopsis-like plant in brackish clays at the top of the Indian Gondwanas where a Wealden facies has now been recognized. Form-genus Ciipressinocladus Seward 1919; 307 I960 Ciipressinocladus Seward; Chaloner and Lorch, 237. 1969 Ciipressinocladus Seward; Harris, 250. 1976 Ciipressinocladus Seward; Barnard and Miller, 43. The following is the diagnosis of Harris slightly emended by Barnard and Miller. Shoot bearing leaves in decussate pairs or alternate whorls. Leaves small and scale- like or longer, dorsiventrally flattened and spreading, not constricted basally into a petiole. In any whorl where adjacent lateral margins of decurrent leaf bases are contiguous, their junctions are marked by conspicuous sutures. Type species. Tlniites salicornoides Unger (selected by Andrews 1955). The form-genus Cupressinocladus was made by Seward to accommodate vegetative shoots with decussate leaf arrangement like the living Cupressaceae. It now seems that some of the species which have been described belong to the Cheirolepidiaceae. Cupressinocladus valdensis (Seward) Seward Plate 97, figs, 6-11 1895 Tlniites valdensis Seward, 209, pi. 20, fig. 6. 1919 Cupressinocladus valdensis (Seward) Seward, 309. 1960 Cupressinocladus valdensis (Seward); Chaloner and Lorch, 236 (brief comparison with C. ramonensis). Emended diagnosis (based on holotype alone). Branching of lateral shoots opposite or alternate, in one plane. Leaves opposite, decussate; free part short, adpressed, surmounting long decurrent bases separated by distinct sutures. Some leaves having median keel along the length of leaf and decurrent base; largest internodes 10 mmx4 mm; smallest 2-0 mmx 1-5 mm. Stomata on abaxial surface (including EXPLANATION OF PLATE 95 Figs. 1-4. Frenelopsis ramosissima Fontaine. 1, part of the specimen in Glasgow Museum photographed under paraffin. Pb 2207, x2. 2, the same magnified to show leaf whorls. x5. 3, SEM of a single segment from an ultimate branch. USNM 192385, x25, 4, SEM of a leaf whorl of the same segment. The marginal hairs are mostly missing but a few can be seen, x 75. PLATE 95 WATSON, Frenelopsis ramosissima 744 PALAEONTOLOGY, VOLUME 20 whole leaf-base cushion) occurring in longitudinal rows, uniseriate or imperfectly biseriate, 9-11 rows per mm. Stoma monocyclic having guard cells sunken below ring of 4-6 subsidiary cells which form a stomatal pit; opening of stomatal pit level with epidermal surface. Over-all diameter of stomatal apparatus 65-85 /xm; each subsidiary cell having a large papilla inside the stomatal pit obscuring guard cells. Guard cells randomly orientated. Epidermal cells non-papillate, thick walled, squarish or rectangular tending to be in longitudinal rows; stomatal rows separated by up to four rows of such cells. Hypodermis of thin-walled rectangular cells under non-stomatal regions, square cells under stomatal regions but absent under stomatal apparatus. Material. Holotype and only known specimen B.M. (N.H.) V. 2138. The locality in the English Wealden is given as Ecclesbourne, Hastings though the exact horizon is not known but it must be Berriasian in age (Hughes 1975). This specimen was originally well preserved but was cellulose varnished in 1 940 which damaged the cuticle. However, I was able to get satisfactory preparations from the surfaces facing the rock and from side branches previously unexposed. Even so the preservation is poor by comparison to the other material described in this paper. Description and comparison. The cuticle of C. valdensis is now known to have the same distinctive type of stoma as various species of Frenelopsis. F. occidentalis Heer from the Lower Cretaceous of Portugal has a closely similar stoma in that the opening of the stomatal pit has no thickening around it and is flush with the general cuticle surface which is totally featureless (PI. 97, fig. 8) except for these simple pit openings. Both species have the characteristic ring of large papillae inside the stomatal pit, entirely filling it and obscuring the guard cells from above. The leaf number of F. occidentalis has not been determined (Alvin 1977) but it is clear that there are no sutures. Two species with leaf arrangement and sutures like C. valdensis are C. acuminifolia Kon’no and F. malaiana Kon’no from the Cretaceous of Malaya (Kon’no 1967, 1968). The latter species which clearly has sutures should not be included in Frenelopsis and has recently been transferred to Cupressinocladus by Barnard and Miller (1976) who think it may have its leaves in whorls of three. Unfortunately there are no cuticle details of either species. C. rarnonensis Chaloner and Torch (1960) from the Lower EXPLANATION OF PLATE 96 Eigs. 1-10. Frenelopsis ramosissima Eontaine. 1, internode cuticle of a young branching order showing closely arranged papillate stomata. USNM 192390, x 100. 2, internode cuticle of an older branching order showing widely spaced stomata. USNM 192385, x 100. 3, SEM of cuticle similar to that in fig. 1. USNM 192385, x 100. 4, SEM of cuticle similar to that in fig. 2. USNM 192385, x 100. 5, single stoma from specimen in fig. 1 showing strongly papillate subsidiary cells. X 500. 6, single stoma from specimen in fig. 2 showing subsidiary cells without papillae. In this stoma the subsidiary cells form a fluted ring as in figs. 4, 10. x 500. 7, cuticle tilted at 60° in SEM to show vertical section of stoma. USNM 192385, x 500. 8, inner surface of cuticle of older branching order, from same piece as fig. 4. USNM 192385, x 100. 9, inside view of stoma (young branching order) showing guard cells and some cutinized, pitted hydrodermal cells. USNM 192385, x 500. 10, stoma on young branch, scarcely papillate and without subsidiary cell papillae, showing guard cells at bottom of shallow stomatal pit. USNM 192385, x 500. PLATE 96 1 WATSON, Frenelopsis ramosissima 746 PALAEONTOLOGY, VOLUME 20 TABLE 1 . Comparison of the species in this paper together with Frenelopsis hoheneggeri (from details given by Reymanowna and Watson 1976). SPECIES KNOWN DETAILS Pseudofrenelopsis parceramosa Pseudofrenelopsis varians Frenelopsis ramosissima Frenelopsis alata Frenelopsis hoheneggeri Cupressinocladus valdensis BRANCfflNG sparse sparse profuse moderate moderate moderate INTERNODE LENGTH 1 - 1 1mm 1.5 - 17mm up to 2cm up to 1.5cm typically 8mm up to 1cm INTERNODE WIDTH 1mm upwards 3 - 7mm up to 2cm up to 5mm typically 3mm up to 2mm PRESENCE OF SUTURE in some ‘open’ forms no no no no yes LEAF NUMBER PER NODE 1 (2/5 phyllotaxis) 1 alternating whorls of 3 alternating whorls of 3 alternating whorls of 3 2 -opposite & decussate MAXIMUM LENGTH OF FREE LEAF 2mm 1.5mm 2mm about 1mm 1.5mm 2mm DEPTH OF SHEATHING BASE 0.8mm 0.8mm 0.5mm up to 1 mm 1mm - LEAF MARGIN hairs up to 80pm hairs up to 60pm hairs up to 100pm fringe of hairs scarious not known INTERNODE CUTICLE THICKNESS 30pm 50- 110(im 38pm 30 - 40pm 40pm about 20pm STOMATAL ARRANGEMENT well defined rows scattered in ‘closed’ forms rows in ‘open’ forms ill defined rows ill defined rows well defined rows well defined rows DENSITY OF STOMATAL ROWS 6 - 10 per mm 8*10 per mm 10-12 per mm less with age 10- 12 per mm 10-12 per mm 9-10 per mm DIAMETER OF STOMATAL APPARATUS 50 - 80pm 70 - 100pm 50 - 75pm 52- 77iim 60 - 70pm 65 - 85pm NUMBER OF SUBSIDIARY CELLS usually 5 or 6 rarely 4 or 7 usually 5-8 rarely 4 or 9 4-6 usually 5 usually 5 occas. 4 or 6 4-6 usually 4 4-6 ORIENTATION OF STOMATAL APERTURE random random horizontal ?random horizontal random PAPILLAE INSIDE STOMATAL PIT? no no no yes yes yes TRICHOMES ON EPIDERMAL CELLS none to very long hairs up to 80pm up to 120pm none none none RIM OF STOMATAL PIT round:- with or without papillae round:- with papillae round:- lobed or papillate stellate stellate stellate STRATIGRAPHIC RANGE Berriasian-Albian Aptian-Albian Barremian - Albian Aptian - Cenomanian Hauterivian Berriasian Jurassic of Israel which is very similar in appearance to C. valdensis is thought to have borne a Masculostrobus cone with Classopollis pollen (Lorch 1968). From the middle Jurassic of Iran Barnard and Miller (1976) have recently described C. pseudoexpansum which has leaves in whorls of three. It is profusely branched with short leaf-base EXPLANATION OF PLATE 97 Figs. 1-5. Frenelopsis ramosissima Fontaine. 1 -4, four of the five successive branching orders of the Glasgow specimen. I, is the oldest; 5, is the youngest; 2, the second order is closely similar to the third order which is omitted. Pb 2207, all x 250. 5, cuticle from the wide stem in Plate 94, fig. 1 showing widely spaced sinuous rows of papillae on original cells separated by smooth areas showing stretch-marks where new cells have been intercalated. USNM 192387, x 100. Figs. 6-11. Cupressinocladus valdensis (Seward), B.M. (N.H.) V. 2138. 6, holotype and only known specimen, xl. 7, cuticle of leaf-base cushion, x 100. 8, outer surface of leaf-base cushion showing stomatal pits flush with surface. X 100. 9, single stoma showing stomatal pit opening, x 500. 10, 11, stomata showing large papillae inside stomatal pit. 10, x 500, 1 1, x 1000. Figs. 1-5, 8, 10, 11, scanning electron micrographs. PLATE 97 WATSON, Frenelopsis, Cupressinocladus 748 PALAEONTOLOGY, VOLUME 20 cushions and a completely different appearance to C. valdensis, nor does it have a similar stoma. However, it is known to bear a male cone containing Classopollis pollen and is therefore clearly cheirolepidiaceous. At the moment there is no evidenee for any species having both two- and three-leaf whorls nor can I say if any of them are succulent like P. varians and F. ramosissima. Acknowledgements. I am most grateful for the opportunity to study the collection in the National Museum of Natural History, Smithsonian Institution and especially thank Dr. Leo Hickey for his continuing help. My visit to Washington D.C. was partly financed by the Royal Society and the University of Manchester. I also thank the following who have been enormously helpful : Dr. K. L. Alvin for use of his unpublished manuscript, help with SEM work, and endless discussion; Professor T. M. Harris, F.R.S., for invaluable help with the manuscript; Dr. Alan Charlton for his patient discussion of the various botanical problems posed by these plants; Mr. James P. Ferrigno of the Smithsonian Institution for all the photography of hand- specimens; Mr. Brian Atherton of Manchester University for all the printing of the micrographs; Depart- ment of Textile Technology, U.M.I.S.T. for use of the SEM. A donation from the W. H. Lang Fund, Manchester University has helped towards the cost of the plates in this paper and is gratefully acknowledged. REFERENCES ALVIN, K. L. 1977. The conifers Frenelopsis and Monica in the Cretaceous of Portugal. Palaeontology 20, 387-404. ANDREWS, H. N., Jun. 1955. Index of generic names of fossil plants, 1820-1950. U.S. Geol. Surv. Bull. 1013, 262 pp. ARCHANGELSKY, s. 1968. 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Sen Memorial Volume, 243-252. Calcutta. HLUSTIK, A. 1972. Frenelopsis alata (Cupress. fossil). Taxon, 21, 210. 1974. New finds of Frenelopsis (Cupressaceae) from the Cretaceous of Czechoslovakia and their problems. Cas. Miner, geol. 19, 263-26R [In Czech, English summary.] JOAN WATSON: CRETACEOUS CONIFERS 749 HLUSTIK, A. and konzalova, m. 1976. Polliniferous cones of Frenelopsis alata (K. Feistm.) Knobloch from the Cenomanian of Czechoslovakia. V'est. ustfed. Ust. geol. 51, 37-45. HUGHES, N. F. 1975. Plant succession in the English Wealden strata. Proc. Geol. Ass. 86, 439-455. 1976. Palaeobiology of Angiosperni Origins. Cambridge University Press, 242 pp. and MOODY-STUART, J. c. 1967. Palynological facies and correlation in the English Wealden. Rev. Palaeohotan. Palynol. 1, 259-268. JUNG, w. 1974. Die Konifere Brachyphyllum nepos Saporta aus den Solnhofener Plattenkalk (unteres untertithon), ein Halophyt. Mitt, hayer. Staatsamml. Palaont. hist. Geol. 14, 49-58. KNOBLOCH, E. 1971. Neuc Pflanzenfunde aus dem bohmischen und mahrischen Cenoman. N. Jh. Geol. Palaont. Abh. 139, 43-56. kon’no, e. 1967. Some younger Mesozoic plants from Malaya. Contributions to the Geology and Palaeonto- logy of Southeast Asia, 38. Geol. palaeont. S.E. Asia. 3, 135-164, Tokyo. 1968. Additions to some younger Mesozoic plants from Malaya. Contributions to the Geology and Palaeontology of Southeast Asia, 48. Ibid. 4, 139 155. Tokyo. LORCH, j. 1968. Some Jurassic conifers from Israel. J. Linn. Soc. (Bot.). 61, 177-188. NATHORST, A. G. 1 893. In FELIX, J. and lenk, h. Beitrdge zur Geologie und Paldontologie der Republik Mexico. 2, 51-54. Leipzig. NEMEJC, F. 1926. On the identity of Sclerophyllutn alatuni Eeistm. and Frenelopsis bohennca Vel. Sb. st. geol. Ust. csl. Repuh. 6, 133-142. [In Czech, English Summary.] oiSHi, s. 1940. The Mesozoic floras of Japan. J. Fac. Sci. Hokkcudo Univ. 5, 123-480. OLDHAM, T. c. B. 1973. The Plant debris beds of the English Wealden. Unpublished Ph.D. Thesis, University of Cambridge, No. 8681. 1976. Elora of the Wealden Plant-debris beds of England. Palaeontology. 19, 437-502. REYMANOWNA, M. 1965. On Weicihselia reticulata and Frenelopsis holieneggeri from iheWsslern Carpathians. Acta palaeobot, Cracov. 6, 15-26. and WATSON, j. 1976. The genus Frenelopsis Schenk and the type species Frenelopsis hoheneggeri (Ettingshausen) Schenk. Acta palaeobot. Cracov, 17, 17-26. ROMARiz, c. 1946. Estudo e revisao das formas portuguesas de Frenelopsis. Bohn. Miis. Lab. miner, geol. Univ. Lis. (4) 14, 135-150. SCHENK, A. 1869. Beitriige zur Elora der Vorwelt. III. Die fossilen Pflanzen der Wernsdorfer Schichten in den Nordkarpathen. Palaeontographica. 19, 1-34. SEWARD, A. c. 1895. The Wealden Elora. Part II. Gymnospermae. Catalogue of Mesozoic Plants in the Department of Geology, British Museum (Natural History), xii ■ 259 pp. 1919. Fo.ssil Plants. A Textbook for Students of Botany and Geology, 4. Cambridge University Press, 543 pp. STEPHENSON, L. w. et ah 1942. Correlation of the outcropping Cretaceous Eormations of the Atlantic and Gulf Coastal Plain and Trans-Pecos Texas. Bull. geol. Soc. Am. 53, 435-448. TEIXEIRA, c. 1948. Flora Mesozoica Portuguesa. I Parte. Services Geologicos, Lisboa, 1 18 pp. VACHRAMEEV, V. A. 1970. Range and palaeoecology of Mesozoic conifers, the Cheirolepidiaceae. Paleont. Jour. 1, 12-25. VELENOVSKY, J. 1888. Ueber einige neue Pflanzenformen der bohmischen Keideformation. Sher. K. bohm. Ges. Wiss. 29, 590-598. WATSON, J. 1964. Revision of the English Wealden Eossil Elora. Unpublished Ph.D. Thesis, University of Reading, R. 1 146. — 1974. Maniccr. A new fossil conifer genus. Taxon. 23, 428. and ALVIN, K. L. 1976. Silicone rubber casts of silicified plants from the Cretaceous of Sudan, Palaeonto- logy, 19, 641-650. WHITEMAN, A. J. 1971. The Geology of the Sudan Republic. Clarendon Press, Oxford. 290 pp. JOAN WATSON Departments of Botany and Geology Typescript received 3 June 1976 jj.^g University Revised typescript received 20 November 1976 Manchester M13 9PL EARLY CAMBRIAN BUTTON-SHAPED PHOSPHATIC MICROFOSSILS FROM THE SIBERIAN PLATFORM by STEFAN BENGTSON Abstract. Button-shaped phosphatic microfossils from the uppermost Atdabanian (Lower Cambrian) of the Siberian Platform (middle reaches of the River Lena, Yakutia, U.S.S.R.) are described as Lenargyrion knappologkum n. g., n. sp. The fossils have a mean diameter of about 150 ^m. One side is smooth and slightly convex, the other conical with a flat crest on which are set minute nodes. The internal structure is double-layered: the conical and nodular surfaces are formed by a dense layer capping the more porous core, which contains fine canals. No growth structures can be seen, and there is evidence of mechanical abrasion on the nodular surface. The ‘buttons’ were probably dermal sclerites in an animal of unknown systematic position. The possibilities of vertebrate afirnities are briefly discussed, but the evidence is considered inconclusive. Phosphatic fossils have long been known to be common in Lower Cambrian rocks. Recent studies by Soviet palaeontologists, notably Missarzhevsky (1966, 1973, 1974, and in Rozanov and Missarzhevsky 1966; Rozanov et al. 1969) and Meshkova (1969, 1974, and in Repina et al. 1974), on the Upper Precambrian and Lower Cambrian carbonates of the Siberian Platform have revealed numerous such fossils, showing that in the early Cambrian a variety of animal groups developed hard parts of calcium phosphate. Most were shortlived, and their affinities are unknown, but they are often very characteristic fossils with great potential for stratigraphical work. A recent review of some of these fossils was given by Matthews and Missarzhevsky (1975). This paper deals with a new form of early Cambrian phosphatic fossil from the Siberian Platform. The material comes from a section on the River Lena, and was collected in 1973 during an international geological excursion to the Aldan and Lena rivers, sponsored by the U.S.S.R. Academy of Sciences. At the visit to the exposure. Dr. Vladimir V. Missarzhevsky informed me of the small ‘buttons’ occurring at a certain level in the carbonatic sequence, and I secured a 900-g sample of the rock for investigation. The ‘buttons’ are described here for the first time and given the systematic name Lenargyrion knappologicum. They cannot yet be included confidently in any known group of organisms, but the morphology and hne structure of the sclerites give some clues to their function. GEOLOGICAL SETTING The sample containing Lenargyrion comes from a section on the River Lena at the outlet of the Achchagyj-Kyyry-Taas creek, about 200 km upstream from Yakutsk (61° 0' N., 126° 44' E.). This is locality Nr. 45 of Zhuravleva et al. (1969). A descrip- tion of the section, together with lists of fossils, is given by Keller et al. (1973). The [Palaeontology, Vol. 20, Part 4, 1977, pp. 751-762.] 752 PALAEONTOLOGY, VOLUME 20 sample is from the middle part of the 16-m thick 2nd Member of the Transitional ‘Formation’ {Perekhodnaya svita). The rock is a light yellow, fine-grained dolomite, with voids partly or completely filled with drusy calcite. The voids are mostly in the form of winding tubes up to a few millimetres in diameter, and are probably caused by boring activities in the consolidated sediment. Lenargyrion occurs in the dolomitic parts of the rock. Associated fossils. The following archaeocyathans have been reported from the 2nd Member of the Transitional ‘Formation’ at Achchagyj-Kyyry-Taas (Rozanov and Missarzhevsky 1966, locality 2015; see Zhuravleva et al. 1969, p. 84): Archaeofungia sp., Compositocyathus muchattensis Zhuravleva, Cyclocyathellidae, Porocyathus piniis Zhuravleva, Lenocyathus sp., Coscinocyathus isoiiitervallum Zhuravleva. In addition to Lenargyrion, my sample contained Rhombocornicidum caneellatum (Cobbold), hyolithelminth tubes, and fragments of inarticulate brachiopods. Stratigrapliieal level. The 2nd Member of the Transitional ‘Formation’ belongs to the youngest part of the Atdabanian Stage (archaeocyathan Zone of Fansycyathus lermontovae). The base of the subsequent Lenian Stage is drawn at the base of the 3rd or 4th Member (see Rozanov 1973, pp. 1 13-115 for discussion of this boundary). In terms of the classical sequence in north-western Europe, the level with Lenargyrion would probably fall within the lower parts of the Lower Comley Limestones in Shrop- shire, i.e. the Callavia Sandstone, 'Eodiseus' bellimarginatus Limestone, or Strenuella Limestone (see Rushton 1974). Matthews (1973) described a large sample of Lapworthella dentata Missarzhevsky from the Strenuella Limestone of Comley. This species was originally described from the uppermost Atdabanian of the River Lena; apart from its occurrence at the type locality at the outlet of the Sinyaya creek, about 8 km from Achchagyj-Kyyry-Taas, Missarzhevsky also reported it from the 3rd Member of the Transitional ‘Formation’ at Achchagyj-Kyyry-Taas (Mis- sarzhevsky in Rozanov et al. 1969, p. 164; and pi. 6, fig. 9). This is just a short distance above the beds with Lenargyrion. The occurrence of R. caneellatum together with Lenargyrion does not help to correlate the level with the Comley sequence, since Cobbold (1921) reported the species to range from the Red Callavia Sandstone (AC2) to the Lapworthella Limestone (Ad), i.e. through practically all of the Lower Comley Limestones. In Scania (south Sweden), a form very similar, if not identical, to Lapworthella dentata occurs in the middle and upper parts of the beds traditionally assigned to the Holmia kjerulfi Zone (Bengtson, unpublished). This form belongs to the species described by Wiman (1903) as Stenotheca cornu, but it is certainly a Lapworthella. The characteristically denticulated L. cornujdentata are followed stratigraphically by smooth-ribbed forms in Scania {L. bornholmiensis (Poulsen) in the ‘fragment limestone’) as well as in Shropshire (L. nigra Cobbold in the Lapworthella Limestone; Cobbold 1921). It is probable that the denticulated lapworthellids mark about the same stratigraphical level in Shropshire and Scania, but a more detailed correlation of the upper Lower Cambrian sequence in Scania must await a revision of both the phosphatic faunas (revision in progress) and the calcareous faunas, particularly the trilobites. (Bergstrom 1973 showed that the zone-fossil H. kjerulfi is apparently not BENGTSON: EARLY CAMBRIAN MICROFOSSILS 753 even present in Scania.) It can be tentatively concluded that the level with Lenargyrion, in terms of Scandinavian stratigraphy, probably lies within the H. kjerulfi Zone. METHODS The phosphatic fossils were isolated through dissolution of the rock in 10% acetic acid. For optical thin sections isolated specimens were embedded in an epoxy resin and ground to a thickness of 25-30 i^m. For microprobe analyses, sections of unetched specimens still embedded in the rock matrix were used. Specimens investigated under a scanning electron microscope (SEM) were coated with gold. For the study of internal structure under the SEM, fractured specimens were used, as well as sections of specimens embedded in epoxy resin and specimens still embedded in rock matrix. The polished sections were etched with 4% HCl for 5-20 seconds before coating. SYSTEMATIC DESCRIPTION Phylum, class, order and family unknown. Genus lenargyrion n. g. Derivation of name. From the River Lena and the Greek argyrion (n.), a small coin. Type and only species. Lenargyrion knappologicum n. sp. Diagnosis. Small (observed range of diameter 50-460 pm) phosphatic sclerites in the shape of circular to oblong discs. One side smooth and slightly convex, the opposite one consisting of a conical surface with a flat crest parallel to the smooth side and capped with minute nodes. Internal structure double-layered; core of porous sub- stance capped by denser layer forming the nodular and conical surfaces. Lenargyrion knappologicum n. sp. Text-figs. 1-5 Derivation of name. The science of knappology (from the Swedish knapp, button) was introduced by August Strindberg in his satirical work De lycksaligas 6 {The Island of the Blissfuk 1884). Knappology deals with classification of buttons, and thus the term is most appropriate for naming the Lena ‘buttons’. Holotype. Swedish Museum of Natural History, Stockholm No. X 1543. Diagnosis. As for the genus. Material. Around 800 investigated specimens. Using the SEM, 236 specimens were studied; optical thin sections were made of 14 specimens in different orientations; polished and etched sections for SEM study were made of 7 specimens. Distribution. The species is known so far only from the type locality at Achchagyj- Kyyry-Taas. Morphology. Text-figs. 1-5 give a representative picture of the variations in size and morphology. The discs are circular to oblong in outline. The observed size range 754 PALAEONTOLOGY, VOLUME 20 TEXT-FIG. 1. Sclerites of Lenargyrion knappologicum n. sp. SEM photographs. Scale bar in lower-right corners is 1 0 /xm. a, Swedish Museum of Natural History, Stockholm (SMNH) No. X 1 533 ; x 900. b, X 1 534 ; x450. c, X 1535; ■ 450. d, X 1536; x 300. e, X 1537; x 300. f, detail of e; x 1200. G, X 1538; x 300. H, X 1539; x250. i, X 1540; x250. J, X 1541 ; x200. k, X 1542; x200. BENGTSON: EARLY CAMBRIAN MICROFOSSILS 755 (length of longest diameter) is 50-460 /xm, most specimens falling between 100 and 220 ^m. In one exceptionally large specimen (text-fig. Ik) with a long diameter of 460 jjim, the ratio between the long and short diameter is as high as 1-8 ; 1, but in no other case does this ratio exceed 1-5:1 (the second largest specimen found has a long diameter of 300 |U,m). There is no clear correlation between size and roundness. The thickness of the discs is fairly constant between 65 and 85 i^m, except for the smallest specimens (below c. 100 fxm in diameter). One side of the disc is smooth and slightly convex (text-figs. Id, 3-5), while on the opposite side is a surface capped with minute nodes (text-figs. 1, 2, 4, and 5). This nodular face is smaller in diameter than the smooth face, and consequently there is an approximately conical surface, here called the girdle, which connects them (text- figs. 1, 2, 4, and 5). The size relationship between the smooth and nodular faces varies considerably, but typically it is about 2 ; 1 in linear dimensions. TEXT-FIG. 2 (left). Holotype of Lenargvrion knappologicum n. sp. SMNH No. X 1543. SEM photograph; x250 TEXT-FIG. 3 (right). Sclerite of Lenargyrion knappologicum n. sp. SMNH No. X 1544. SEM photograph, showing smooth face; x 300. The nodes have a diameter of about 10-15 fim and a density of about 50 per 0-01 mm^. The outermost ones are arranged in a ring, but this regular order decreases progressively towards the centre of the face. Exceptionally, a node may occur on the girdle outside the otherwise well-defined face (text-fig. It, upper left). Specimens may have some or all of the nodes effaced. In most cases, the missing nodes are represented by fracture surfaces, whereas neighbouring nodes are unaffected. This can be seen in text-fig. 1e and k. In a few cases, as represented by the specimen in text-fig. 1g, the whole nodular face is almost smooth, although the nodular pattern may still be faintly visible. Commonly, the sharp brim of a sclerite appears unaffected by any kind of abrasion, even when part or all of the nodes are thus missing. The profile of the girdle is concave to straight, rarely convex. Commonly it has radiating patterns which are directly related to the outermost ring of nodes. This is very pronounced in text-fig. 1h, but can also be seen in text-figs. Id, e, i-k, and 2. Also, a finer radiating pattern may be present (text-fig. If). The girdle ends in a circum- ferential demarcation line (e.g. text-fig. 1d-f) which is related to the internal structure (see below and text-figs. 4 and 5). The brim of the disc often bears fine transverse 756 PALAEONTOLOGY, VOLUME 20 striations (text-fig. Id, e, f, h, i), and this surface sometimes passes directly into the smooth face, or sometimes meets further circumferential lines (e.g. text-fig. If). The surface of the slightly convex smooth face is in fact somewhat rougher than that of the girdle and nodular face (cf. text-fig. 3 and text-figs. 1, 2), but bears no regular structures. TEXT-FIG. 4. Polished and etched section through sclerite of Lenargyrion knappologicum n. sp. SMNH No. X 1545. A, over-all view of section, showing distinct histological differentiation into capping (top), forming nodular face and girdle, and core. Positions of b-d indicated; x530. b-d, details of a; x2120. Note external boundary between capping and core in b (white arrow). Internal structure. Both in optical thin sections and in polished and etched sections studied by SEM microscopy, the discs are clearly seen to be built up of two com- ponents (text-fig. 4). The surfaces of the nodular face and girdle are formed by a continuous layer which is 2 jum thick at the girdle and somewhat thicker at the nodular face. The nodes are formed entirely by this layer, which may reach a thick- ness of around 15 /xm at a node. This layer is here called the capping', it terminates just short of the brim of the disc, and the boundary can be seen externally as the demarcation line mentioned above (text-fig. 4b, arrow). The remainder of the disc is made up of a slightly more porous substance, here called the core. The porosity as observed has probably been exaggerated by the etching processes, but there can be no doubt that the core is less dense than the capping. The primary porosity is probably the main reason why Lenargyrion sclerites are easily corroded, even in weak acids. BENGTSON: EARLY CAMBRIAN MICROFOSSILS 757 The porosity is generally greater near the smooth face, although this too may be a result of the acid preparation, which is likely to have stronger effects where the substance is not protected by the capping. Very often, particularly near the smooth face, the porosity can be seen to consist of fine canals with a direction roughly parallel to the axis of the disc (text-fig. 4d). This may be compared to the striation of the brim (text-fig. If). In a few specimens there are suggestions of a layering close to and parallel to the smooth face. This may reflect the same structure as the external circumferential growth lines seen in some specimens (e.g. text-fig. If, bottom) outside the capping core demarcation line. The wide space between capping and core seen in text-fig. 4a-c seems to be an artefact due to shrinkage of the epoxy resin or to the etching being facilitated in the zone of contact between the two layers. It is less prominent on not so deeply etched specimens, and has not been observed in fresh fracture surfaces. No discrete apatite crystallites have been identified with certainty, although the granulated pattern seen in the specimen in text-fig. 4 suggests more or less isodiametric crystallites with an approximate size of 0-2-0-3 [xm. As observed under a polarizing microscope, the crystallographic c axes in the core are generally aligned parallel to the axis of the disc and, in the peripheral parts, parallel to the surface of the girdle. This direction corresponds well to that of the canals in text-fig. 4, and the extinction between crossed nicols usually brings out a pattern which appears to conform to the direction of the canals. Often there is a layer of particularly strong extinction along the smooth face. The extinction in the capping is usually weak, but at least in one section the orientation of c axes has been observed to be perpendicular to the inner surface, both in the girdle and in the nodular face. 758 PALAEONTOLOGY, VOLUME 20 Investigations with a microprobe revealed no difference in chemical composition between core and capping. Both have a composition corresponding to that of fluoric apatite. When dissolved in acid such as HCl some, but not all, sclerites leave a shrivelled ‘ghost’ of presumably organic matter. There is no internal evidence of periodic growth of the sclerites. Once the capping had been formed, they could not have grown at all unless the growth was coupled with periodical resorption of at least the capping. Frequency. Text-flg. 6 is a size-frequency histogram for all specimens (340) found in the unsifted residue of 39-6 g of rock. The curve is unimodal and approaches normal distribution. However, the etching of this sample also revealed that some Lenar- gyrion sclerites dissolve even in the 10% acetic acid used and, although factors other than size (e.g. degree of porosity) also appear to be important for the preser- vation, small specimens are generally more likely to have been destroyed than larger ones. Another factor, which might also have caused a loss of small specimens in this count, is that these were more likely to be overlooked among the bulk of remaining dolomite grains of approxi- mately the same size. It is thus likely that a true size-frequency curve would include more small specimens. Extrapolating from the number of specimens found in this count, the number of Lenargyrion sclerites per kilogram of rock would be around 8500. Considering the possible losses mentioned above, the true value probably exceeds 10000. TEXT-FIG. 6. Size-frequency histogram of all sclerites (340) of Lenargyrion knappologicum n. sp. found in etching residue of 39-6 g of rock. FUNCTION OF THE LENARGYRION SCLERITES The fact that the nodular face and the girdle are formed by a capping layer, denser than the core of the sclerite, together with the evidence of mechanical abrasion restricted to the nodular face, suggests that the Lenargyrion ‘buttons’ were external dermal sclerites. The capping would thus serve the same function as enamel and enamel-like substances in vertebrate odontodes (= ‘dermal teeth’; see (5Z)rvig 1967, p. 47). As dermal sclerites, they could be distributed more or less evenly over the body surface for general protection and increase of surface friction, or they could be con- centrated in organs for locomotion, grasping, or dealing with food. The circumstance that abraded nodular faces are quite common, in spite of the minute size of the sclerites, suggests that the function was not merely protective. The general morphology of the sclerites agrees well with this interpretation. The broad base (i.e. the smooth face) would provide good anchorage for the sclerite, and BENGTSON: EARLY CAMBRIAN MICROFOSSILS 759 the nodes would serve to increase the friction. The fact that the thickness is roughly equal (c. 65-85 jwm) in sclerites of all sizes except those smaller than 100 ixm in diameter would reflect the demand that the nodular faces of neighbouring sclerites be in the same plane. This would also mean that the sclerites were situated fairly close to each other, although the regular curve of the brim shows that they were not in contact. Text-flg. 7 shows a reconstruction of the outer part of the body wall of Lenargyrion, based on the above interpretation, with the sclerites shown in their assumed functional position. The picture gives no indication as to whether they were also formed in this position, or within or below the epithelial tissue. However, the fact that there is no evidence of successive growth of sclerites, in spite of the large variation (almost by a factor of ten) in their individual diameters, indicates that they were unable to grow once they had assumed their shape and functional position. If the animal increased its skeletal mass during growth, it probably did so by adding new sclerites rather than increasing the size of the old ones. Whether the latter were retained, resorbed, or shed is not possible to determine. This inability of the sclerites to grow suggests that they were not formed in the position shown in text-flg. 7, but rather were secreted by tissue below the body surface, through which they afterwards erupted. However, the evidence for this is not conclusive. TEXT-FIG. 7. Hypothetical reconstruction of outer part of body wall of Lenargyrion knappologicum n. sp., showing inferred position of sclerites (capping black, core dark grey) relative to soft tissue (light grey). Approximately xl30. One possible alternative interpretation is that the sclerites were opercula of tube- dwelling animals. This view stems from the fact that the conical shape of the girdle would make them fit snugly (smooth face outwards) against the aperture of such a tube, as well as from the presence of phosphatic tubes (although very rare compared to the ‘buttons’) with comparable diameter in the same sample. The lack of growth structures could be explained by the assumption that the animal continually shed its opercula during growth, and the presence of a capping layer could represent a modi- fication of the surface of attachment with the secreting epithelium. However, the evidence for selective abrasion of the nodular face would remain unexplained by this model, and for this reason it is considered less probable. AFFINITIES OF LENARGYRION Very little can be said about the Lenargyrion animal itself, except that it was probably equipped with dermal sclerites, in general structure superficially similar to odontodes of, e.g. thelodonts or sharks. It is tempting to take this general similarity as an indication of deeper homology, since an apatitic sclerite consisting of a porous core 760 PALAEONTOLOGY, VOLUME 20 with fine canals and a capping of denser material would agree quite well with a simple unit of the dermal skeleton that might be expected to occur in the earliest vertebrates of the hypothetical primary micromeric stage of skeletal development ((JZ)rvig 1968, p. 381), i.e. the initial stage in which the dermal skeleton supposedly consisted of isolated, minute scales. However, Lenargyrioti sclerites show no conclusive vertebrate characteristics such as cavities after odontoblast processes (dentinal tubules) or osteoblasts, and the rare examples of acellular bone tissue in vertebrates (e.g. aspidin in heterostracans) seem to offer no striking points of comparison. Consequently, any such suggestion of homology between skeletal tissues of Lenargyrion and vertebrates is highly speculative. The question of affinities of Lenargyrion is thus better left open at present. Whereas the sclerites appear to show some agreement with the structure and function of a primitive vertebrate dermal skeleton, the evidence for vertebrate affinity is far from convincing, and there remains a strong possibility that these Cambrian sclerites originated in an unknown group of invertebrates, unrelated to the vertebrate stock. The earliest presumed vertebrate of which there is a published record, Anatolepis, is of Arenigian age and carried a continuous, very thin armour, set with minute elliptical to rhomboidal plates (Bockelie and Fortey 1976). In addition. Winder (1976) gives a reference to an unpublished record (by N. E. Cygan 1962) of presumed fish remains in the Upper Cambrian. It is not unlikely that the earliest evolution of mineralized skeletons in vertebrates occurred during a substantial part of the Cambrian, and it may be possible to arrive at a conception of Cambrian vertebrates when more information has been assembled on the histology of the various groups of problematical phosphatic fossils that occur in Cambrian rocks. With such informa- tion available, it may also be possible to find a place for Lenargyrion within the zoological system. Acknowledgements. I am grateful to Vladimir V. Missarzhevsky, Moscow, for information on the occurrence of the Lena 'buttons’. Michael G. Bassett, Cardiff, kindly commented on the manuscript and improved the English. The study has also profited from criticism by Valdar Jaanusson, Stockholm, Anders Martinsson, Uppsala, and Tor (Z)rvig, Stockholm, My participation in the excursion to the Aldan and Lena rivers was financed through grants from the Swedish Natural Science Research Council, Th. Nordstroms Testa- mentsfond and C. F. Liljewalchs Resestipendiefond. Note added in proof. In a recent report on Cambrian to Triassic conodont stratigraphy of the Taurus Range in Turkey, Gedik (1977) briefiy described and illustrated fossils similar to Lenargyrion knappologieum. They were referred to the new genus and species Hadimopanella oezgueli. Judging from Gedik’s illustrations, H. oezgueli differs from L. knappologieum in that the capping terminates shortly outside the nodular face, so that most of the width of the girdle shows the exposed surface of the core. Also, the nodes are eoarser (about 20 ptm in diameter as compared to 10-15 jum in L. knappologieum) and their density is correspondingly smaller (about 15 per 0-01 mm^ as compared to about 50 per 0 01 mm^ in L. knappologieum). Thus the two speeies are clearly distinguished from each other; whether or not the generic name Lenargyrion should be considered a junior subjective synonym of Hadimopanella is better judged when more forms of this little-known group have been described. BENGTSON: EARLY CAMBRIAN MICROFOSSILS 761 Gedik’s material comes from reddish nodular limestones stated to belong to the Upper Cambrian. However, the additional fossils he reported from these beds, Prooneotodus tenuis (Muller) and Hertzina? hisulcata Muller, do not prove a late Cambrian age. Both species are known from the Middle Cambrian as well, and this is true also for the third conodont-like form, Furnishina furnishi Muller, which Gedik (1977, p. 36) reported from approximately equivalent beds in the same area. REFERENCES BERGSTROM, J. 1973. Classification of olenellid trilobites and some Balto-Scandian species. Norsk geol. Tidsskr. 53, 283-314. BOCKELiE, T. and FORTEY, R. A. 1976. An early Ordovician vertebrate. Nature, 260 (5546), 36-38. COBBOLD, E. s. 1921. The Cambrian horizons of Comley (Shropshire) and their Brachiopoda, Pteropoda, Gasteropoda, etc. Q. Jl geol. Soc. Loud. 76, 325-386. GEDIK, I. 1977. Orta Toroslar’da konodont biyostratigrafisi. [Conodont biostratigraphy of the Middle Taurus.] Turk. Jeol. Kurumu Bui. 20, 35-48. [In Turkish, with an English summary.] KELLER, B. M. et al. 1973. PutevoditeT ehkskursii po rekarn Aldami i Lene. Mezhdunarodnaya ehkskursiya po prohleme granitsy kembriya i dokemhriya. [Excursion guide to the Aldan and Lena Rivers. International excursion on the problem of the Precambrian-Cambrian boundary.] 118 pp. Moscow, Yakutsk. [In Russian and English.] MATTHEWS, s. c. 1973. Lapworthellids from the Lower Cambrian Strenuella limestone at Comley, Shrop- shire. Palaeontology, 16, 139-148. and MISSARZHEVSKY, V. V. 1975. Small shelly fossils of late Precambrian and early Cambrian age; a review of recent work. Jl geol. Soc. bond. 131, 289-304. MESHKOVA, N. p. 1969. K voprosu o paleontologicheskoj kharakteristike nizhne-kembrijskikh otlozhenij Sibirskoj platformy. [To the question of the palaeontological characteristics of the Lower Cambrian deposits of the Siberian Platform.] In Zhuravleva, i. t. (ed.). Biostratigrafiya i paleontologiya nizhnego kembriya Sibiri i DaTnego vostoka, 158-174. Izd. ‘Nauka’, Moscow. [In Russian.] 1974. Cambroscleritida incertae sedis— novyj otryad kembrijskikh iskopaemykh. [Cambroscleritida incertae sedis— a new order of Cambrian fossils.] In Zhuravleva, i. t. and rozanov, a. yu. (eds.). Biostratigrafiya i paleontologiya nizhnego kembriya Evropy i severnoj Azii, 190 193. Izd. 'Nauka’, Moscow. [In Russian.] MISSARZHEVSKY, V. V. 1966. Pcrvyc nakhodki Lapworthella v nizhnem kembrii Sibirskoj platformy. [The first finds of Lapworthella in the Lower Cambrian of the Siberian Platform.] Paleont. Zh. 1966 (2), 13-18. [In Russian ] 1973. Konodontoobraznye organizmy iz pogranichnykh sloev kembriya i dokembriya Sibirskoj platformy i Kazakhstana. [Conodont-shaped organisms from the Precambrian-Cambrian boundary strata of the Siberian Platform and Kazakhstan.] In Zhuravleva, i. t. (ed.). Problemy paleontologii i biostratigrafii nizhnego kembriya Sibiri i DaTnego vostoka, 53-57. Izd. ‘Nauka’, Moscow. [In Russian.] 1974. Novye dannye o drevnejshikh okamenelostyakh rannego kembriya Sibirskoj platformy. [New data on the oldest Cambrian fossils of the Siberian platform.] In Zhuravleva, i. t. and rozanov, a. yu. (eds.). Biostratigrafiya i paleontologiya nizhnego kembriya Evropy i severnoj Azii, 179-189. Izd. ‘Nauka’, Moscow. [In Russian.] ORViG, T. 1967. Phylogeny of tooth tissues: evolution of some calcified tissues in early vertebrates. In MILES, A. E. w. (ed.). Structural and Chemical Organization of Teeth, 1, 45 110. Academic Press, New York. 1968. The dermal skeleton; general considerations. In orvig, t. (ed.). Current Problems of Lower Vertebrate Phylogeny, 373-397. Almqvist & Wiksell, Stockholm. REPINA, L. N. et al. 1974. Biostratigrafiya i fauna nizhnego kembriya Kharaulakha (khr. Tuora-Sis). 299 pp. Izd. ‘Nauka’, Moskva. [In Russian.] ROZANOV, A. YU. 1973. Zakonomemosti morfologicheskoj ehvolyutsii arkheotsiat i voprosy yarusnogo raschleneniya nizhnego kembriya. [Regularities in the morphological evolution of archaeocyathans and questions regarding the stage division of the Lower Cambrian.] Trudy geol. Inst. Akad. Nauk SSSR, 241, 164 pp. [In Russian.] 762 PALAEONTOLOGY, VOLUME 20 ROZANOV, A. YU. and MISSARZHEVSKY, V. V. 1966. Biostratigrafiya i fauna nizhnikh gorizontov kembriya. [Biostratigraphy and fauna of the lower beds of the Cambrian.] Trudy geol. Inst. Acad. Naiik SSSR, 148, 126 pp. [In Russian.] et al. 1969. Tommotskij yams i problema nizhnej granitsy kembriya. [The Tommotian Stage and the problem of the Cambrian lower boundary.] Ibid. 206, 380 pp. [In Russian.] RUSHTON, A. w. A. 1974. The Cambrian of Wales and England. In Holland, c. h. (ed.). Cambrian of the British Isles, Norden, and Spitsbergen, 43-121. John Wiley & Sons, London, New York, Sydney, Toronto. wiMAN, c. 1903. Studien iiber das Nordbaltische Silurgebiet. I. Olenellussandstein, Obolussandstein und Ceratopygeschiefer. Bull. geol. Instn Univ. Upps. 6, 12-76. WINDER, c. G. 1976. Enigmatic objects in North American Ordovician carbonates. In bassett, m. g. (ed.). The Ordovician System : proceedings of a Palaeontological Association symposium, Birmingham, September 1974, 645-657. University of Wales Press and National Museum of Wales, Cardiff. ZHURAVLEVA, I. T., MESHKOVA, N. p. and LUCHININA, V. A. 1969. Gcologicheskij profiT cherez rajon strato- tipicheskogo razreza nizhnego kembriya v srednem techenii r. Leny. [A geological profile through the region of the Lower Cambrian stratotypical section in the middle reaches of the River Lena.] 176 pp. Izd. ‘Nauka’, Novosibirsk. [In Russian.] STEFAN BENGTSON Department of Palaeobiology Box 564 S-751 22 Uppsala Typescript received 6 July 1976 Sweden SPECIES OF TRETASPIS (TRILOBITA) FROM THE ASHGILL SERIES IN WALES by DAVID PRICE Abstract. Nine species of Tretaspis are recognized from various horizons of the Ashgill Series in Wales. Tretaspis coUiquia Ingham is regarded as a sub-species of T. moeldenensis Cave. Four populations of Tretaspis are placed in T. moeldenensis (s.l.) and considered to occupy intermediate positions within the plexus connecting T. moeldenensis coUiquia and T. m. moeldenensis', for the latter, large topotype samples also give increased knowledge of the fringe characters. T. cf. radialis Lamont occurs throughout the bulk of the Sholeshook Limestone Formation (south-west Dyfed) but is replaced in the topmost part by T. alT. radialis. The pygidium of an indeterminate species from the Birdshill Limestone at Llandeilo resembles that of T. m. moeldenensis. T. hadelandica hrachvsticlius Ingham is described from the highest Sholeshook Limestone and succeeding Slade and Redhill Mudstone Formation, T. cf. latilimbus distichus Ingham from the high Ashgill of the south-west Berwynsand T. cf. jort/ro (Reed) from the topmost Ashgill of the Meifod area. An indeterminate form from the Slade and Redhill Mudstones and T. cf. calcaria Dean from the Rhiwlas Limestone are not yet placed within either of Ingham’s two main species groups. As with other trinucleid trilobites at lower levels in the Ordovician, species of the genus Tretaspis are of stratigraphical importance within the Ashgill Series in that, apart from their abundance and wide geographical distribution, some forms appear to exhibit progressive evolutionary changes. Good examples of this are seen in some of the species described by Ingham (1970, pp. 45-57) from the north of England. Although the phylogeny of Tretaspis is far from completely understood, some evolutionary relationships are known, and these can be used for correlation in different successions. Terminology. The terminology and notation used in describing fringe characteristics largely follow those of Ingham (1970, pp. 40-41). Ingham has pointed out that in many species of Tretaspis new internal (I) arcs of pits are apparently inserted in evolution on the external side of the innermost arc already present. In many specimens this is strongly suggested by the disposition and small size of pits developed in this position (e.g. in the specimen illustrated here as PI. 101, fig. 2). Accordingly the innermost pit-arc is regarded as complete and is unnumbered and referred to as the E arc. Hughes eta/. (1975, p. 6) have found the concept of the E arc of wide application within family Trinucleidae and reveal that current work on silicified young stages of marrolithines shows E to be the first arc to develop on the immature fringe. Ingham (1970) is also followed in using an aR/bR notation to refer respectively to the radii containing the E-E Pds and those with the E. E,, and Ej pits which in members of his T. seticornis species group (see below) are out of line, and in his use of the terms ‘genal roll’ and ‘brim’ solely for describing fringe shape. In addition, the term ‘list’ (Stormer 1930) is used for the concentric ridges sometimes developed between the inner pit-arcs on the upper lamella. The cephalic orientation adopted for descriptive purposes is that suggested by Hughes et al. (1975, pp. 546-547, fig. 7) with the anterior and posterior fossulae in the horizontal plane. Repositories. The material upon which this paper is based is housed in the following museums, the prefixes for whose specimen numbers are indicated in brackets: British Museum (Natural History) (BM), Geology Museum, University of Birmingham (BU), Hunterian Museum, Glasgow (HM), Institute of Geological Sciences (GSM), National Museum of Wales (NMW), and the Sedgwick Museum, Cambridge (SM). [Palaeontology, Vol. 20, Part 4, 1977, pp. 763-792, Pis. 98-103.] 764 PALAEONTOLOGY, VOLUME 20 SYSTEMATIC PALAEONTOLOGY Family trinucleidae Hawle and Corda, 1847 Subfamily trinucleinae Hawle and Corda, 1847 Genus tretaspis M’Coy, 1849 Type species. Subsequently designated by Bassler 1915, p. 1285; Asaphus seticornis Hisinger, 1840, p. 3, pi. 37, fig. 2; Fjacka Formation, Dalarna, Sweden. Remarks. Ingham (1970, pp. 41-44) attempted a division of known species of Tretaspis into three species-groups typified respectively by T. moeldenensis Cave, 1960, T. seticornis (Hisinger), and ‘C’ grannlata (Wahlenberg, 1818). ‘C.’ granulata and allied forms such as "T.'' portrainensis Lamont, 1941, have subsequently been removed from Tretaspis and placed in genus Nankinolithus Lu (Hughes et al. 1975). The genus Tretaspis is thus divided by the latter authors into two major groups of species. As Ingham noted (1970, p. 41), the extent to which these groups form natural associations is not yet clear and there are difficulties in fitting a few forms (including two dealt with in this paper) into them. Accordingly the T. moeldenensis group and the T. seticornis group are adopted herein tentatively and with the reservation that the two forms referred to above (T. sp. indet. B and T. cf. calcaria Dean) are not placed in either group but are regarded as being, as yet, of uncertain affinity (see also p. 787 below). THE TRETASPIS MOELDENENSIS GROUP For the characteristics of the group see Ingham 1970, p. 43. Tretaspis moeldenensis Cave, 1960 (sensu lato) Plates 98 and 99; Plate 100, fig. 1 ; text-fig. 1 1909 Trinucteus seticornis, var. hiickkmdi, Barr.; Elies, faunal list, p. 182. 1909 Trimtcleus fimbriatiis Murch.; Strahan et al., p. 56. 1921 Trimtcleus cf. nicholsoni Reed; Wills and Smith, table, p. 187. 1921 Trinucleus seticornis Hisinger; Wills and Smith (pars), table, p. 187. 1921 Trimtcleus sp.; Wills and Smith (pars), table, p. 187. 1927 Trimtcleus cf. nicholsoni Reed; Wedd et al., list, p. 40. 1927 Trimtcleus seticornis (His.); Wedd et al. (jtars), list, p. 40. 1927 Trimtcleus sp.; Wedd et al. (pars), list, p. 40. 1928 Trimtcleus seticornis group; King, lists, p. 698. EXPLANATION OF PLATE 98 Figs. 1-5. Tretaspis moeldenensis Cave (s.l.). Population A, Bodeidda Mudstone Formation, Bodeidda, near Conway, x 6. 1-3, GSM RV 9144a, internal mould of cephalon, dorsal, anterior, and left-lateral views. 4, GSM RV 9141, partial internal mould of cephalon, anterior view. 5, GSM RV 9142, internal mould of cephalon, anterior view. Figs. 6-9. Tretaspis moeldenensis Cave (s.l.). Population B, basal Tre-wylan Beds, Glan-yr-afon Farm, north of Llansantffraid-ym-Mechain. 6, Bu. 209, internal mould of cephalon, antero-dorsal view, x4; original of Whittington 1938, pi. 38, fig. 2. 7, SM A94573a, internal mould of cephalon, dorsal view, x5. 8, Bu. 208, internal mould of cephalon, oblique view, x4; original of Whittington 1938, pi. 38, fig. 1 . 9, SM A94592, internal mould of pygidium, dorsal view, x 5. PLATE 98 PRICE, Tetraspis from Wales 766 PALAEONTOLOGY, VOLUME 20 1929 Trinucleus sp.; Wedd et al. (pars), list, p. 61. 1938 Tretaspis cf. kiaeri Stormer; Whittington (pars), p. 445, pi. 38, figs. 1-3; non list, p. 452. 1960 Tretaspis moeldenensis Cave, pp. 334-337, pi. 10, figs. 1-7. 1961 Tretaspis kiaeri Stormer radialis Lamont; Dean (pars), pp. 122-125. 1962 Tretaspis kiaeri Stormer radialis Lamont; Dean, p. 86, pi. 9, figs. 2-4. 1970 Tretaspis colliquia Ingham, pp. 53-54, pi. 8, figs. 8-20; text-fig. 146. 1970 Tretaspis cf. moeldenensis Cave; Ingham, pp. 54-55, pi. 8, figs. 21-26; pi. 9, figs. 1-7; text- figs. 14c, 19. 1973n Tretaspis moeldenensis Cave; Price, tables 3 and 4. 19736 Tretaspis moeldenensis Cave; Price, p. 540. 1974 Tretaspis moeldenensis Cave; Price, pp. 844-847, pi. 112, figs. 10-12; pi. 113, figs. 1-4; text-fig. 1. Holotype. Figured by Cave 1960, pi. 10, figs. 1 and 3, SM A50668, from the basal Sholeshook Limestone Formation of Moldin ( ^ ‘Moelden’), near Llandowror, Dyfed, South Wales. Remarks. Ingham (1970, p. 55) has referred to an evolving T. colIiquia-T. moeldenensis plexus. In Wales there appear to be at least three or four populations which fall within this plexus and whose members in general show characters intermediate between those of T. colliquia and T. moeldenensis. In terms of fringe-characters, particularly the development of the I4 pit-arc, each of these populations shows much variation. This variation can be such ^n Population B of text-fig. 1 for instance) that the fringe- characters of some members of a single population fall within the range of T. colliquia, the fringe-characters of other members within the range of T. moeldenensis, and those of yet other members fall between, outside the known range of either form. For this reason, T. colliquia and T. moeldenensis are no longer regarded as specifically distinct and T. colliquia is treated here as a sub-species of T. moeldenensis (s.L). The name T. m. colliquia is considered applicable to populations with a similar range of fringe variation to that of the sample described by Ingham (1970, see synonomy) while the name T. m. moeldenensis is similarly applied to populations falling within the range of fringe variation of topotype material of that form (here described). Populations where the variation ranges outside that of either of these end-members might be compared with one or other of them by the use of such designations as ‘cf.’ and ‘aflf.’. The large range of variation already referred to within some of these popula- tions, however, renders such terms difficult of application. Partly for this reason and partly because of the small sample sizes and consequent limited knowledge of the range of variation of some of the populations involved (and of the described material of T. m. colliquia), such a course is not adopted and the populations described here are referred to as populations of T. moeldenensis (s.l.). This solution is also felt to be more appropriate in reflecting the probable existence of a continuum between T. m. colliquia and T. m. moeldenensis. Population A Plate 98, figs. 1-5; text-fig. 1 Material, horizon, and locality. Twenty specimens, in the collection of the Geological Survey, from the Bodeidda Mudstone Formation; quarry 14 m west of Bodeidda, about 2-5 km south-west of Conway, Gwynedd, North Wales. Description. Cephalon approximately semicircular in dorsal view; exact proportions masked by distortion. Pseudofrontal glabella lobe occupying almost two-thirds of total glabellar length (sag.), sub-circular in frequency frequency frequency frequency frequency T moeldenensis (s.l.) (Population A) Pits in El Pits in I4 Pits in El (Population B) o' I ' 2' 3' 4' 5' 6* 7' s' 9'10’tl 'l2'l3'l4 Pits in I4 Pits in I3 absent frontally Pits in I3 absent frontally T. moeldenensis moeldenensis (topotype) n=i6 26 27 28 29 30 31 10 II 12 13 14 15 16 17 18 19 Pits in El Pits in I4 Pits in I4 absent frontally T of. radialis n = io 'iM VJlu n = io 23 2425 26 2728 10 11 12 13 14 15 16 17 IB 19 0 12 3 4 12 13 14 15 I6'l7 18 19 20 21 l4 extends to (R no.) Pits in El Pits in I4 T. off. radialis Pits in I4 absent I4 extends to frontally (Rno.) 23' 2425' 262728' 012 3 4^^ Pits in El Pits in I4 9 'lO n 12 13 14 Pits in posterior row Pits in posterior row 10 II 12 13 14 15 Pits in posterior row Pits in posterior row Pits in posterior row TEXT-FIG. 1. Histograms of selected fringe characters in species of Tretaspis of the T. moeldenensis group, n is the sample number for each character shown. All histograms show half-fringe data. T. moeldenensis (s.l.): Population A from Bodeidda Mudstone Formation, Bodeidda, near Conway, Population B from basal Tre-wylan Beds, near Llansantffraid-ym-Mechain, Powys. T. moeldenensis moeldenensis from basal Sholeshook Limestone Formation, Moldin, near Llandowror, Dyfed. T. cf. radialis from Sholeshook Limestone Formation of Haverfordwest and Llandowror, Dyfed. T. aff. radialis from topmost Sholeshook Limestone and Slade and Redhill Mudstone Formation of Haverfordwest area. 768 PALAEONTOLOGY, VOLUME 20 dorsal view, strongly domed, particularly transversely, but never sub-spherical so that the outline in anterior view remains parabolic (PI. 98, figs. 2, 4-5); bearing small, apically situated median tubercle; barely overhanging the fringe anteriorly. Occipital ring narrow and strongly convex (sag. and exsag.), orientated postero-dorsally ; curving forwards abaxially. Occipital furrow broad and shallow mesially, abaxially containing deep ovoid apodemal pits. Ip lateral glabellar lobes short (tr.), gently convex, abaxially rounded. Ip lateral furrows in form of strongly oblique shallow slots, diverging posteriorly and almost reaching the occipital apodemes. 2p lobes only gently convex (exsag.), set transversely, narrowest adaxially, broadening outwards and coalescing anteriorly, around the 2p furrows, with the pseudofrontal lobe. 2p furrows in form of large, shallow ovoid depressions of rather indistinct outline. 3p furrows present as faint but definite depressions on sides of pseudofrontal lobe. Axial furrows broad (tr.), particularly posteriorly; anteriorly containing small, deep fossulae. Genal lobes sub-quadrant shaped, moderately convex, and dropping steeply antero-laterally but not overhanging fringe; bearing lateral tubercles, rather larger than the median tubercle, on about the level of the anterior edges of the 2p lateral furrows; dropping steeply to broad (exsag. ) posterior border furrows which abaxially contain large posterior fossulae. External moulds show surface of glabella and genal lobes to be smooth. Fringe moderately broad, comprising steeply inclined, convex genal roll and well-developed, gently concave brim; internal moulds show a deep, rather narrow girder. Outer 3 pit-arcs, Ei„2. In arranged frontally and antero-laterally in deep radial sulci which persist on one specimen to about R19, on another to R24. The number of pits in E, ranges from 24 to 28 (half-fringe, see text-fig. 1 ); pits of E2 are usually absent from the posterior row and sometimes from the posterior-most 2 rows. The number of pit-arcs developed internally to the 3 outer arcs and their degree of completeness is very variable. In addition to I„, all specimens have a complete I2 arc. Nine specimens show a complete I3 arc but on 3 others I3 pits are absent frontally from R1 and R2 (e.g. PI. 98, figs. 4, 5). These 3 specimens do not show an I4 pit-arc but on the 9 where I3 is complete, a short I4 arc, normally with between 1 and 5 pits, is developed in front of the axial furrows. One specimen, however (GSM RV9133), shows at least 10 I4 pits. In no specimen is the I4 arc complete frontally, pits generally being developed from R3 or R4 outwards. Pits of the I„ arc are frequently large. All pits are arranged in strict radial alignment until the genal prolongations are reached, where the alignment breaks down due to the intercalation of extra pits between the I, and I2 arcs; the fringe, thus expanded, may have from 1 1 to 14 pits in the posterior row. No lists have been observed on the fringe upper lamella. On the lower lamella, pits of the internal arcs are arranged, except on the genal prolongations, in strong radial sulci (PI. 98, fig. 3). Thorax and pygidium unknown. Population B Plate 98, figs. 6-9; text-fig. 1 Material, horizon, and locality. Useful material comprises about twenty-eight specimens from the basal Tre-wylan Beds exposed around a small waterfall in the dingle 370 m north-west of Glan-yr-afon Farm, about 4 km north of Llansantffraid-ym-Mechain, Powys, Mid-Wales. This is Locality 42 of Whittington 1938 and Locality 3 of Wedd et al. 1929 (list, p. 62). Description. The general form and proportions of the cephalon are very similar to those described for specimens m Population A; however, no specimen so far seen definitely shows the presence of 3p lateral glabellar furrows. Again, the genal lobes, though dropping steeply antero-laterally, do not generally over- hang the fringe. Both these and the pseudofrontal lobe are smooth. The fringe itself has a well-developed brim, particularly laterally and antero-laterally. Pit-arcs E2, Ej, and I; are contained in deep radial sulci which persist laterally to R23 or R24. Ej contains from 26 to 29 pits; E2 pits are absent from the posterior row or posterior 2 rows. All specimens have a complete I2 arc. Of 9 specimens which show clearly the dis- tribution of pits anteriorly, 7 have the I3 arc complete, the others have respectively 1 and 24 pits of I3 missing. I4 is very variably developed. Apart from the definite numbers shown in the histogram (text-fig. 1), this arc in other specimens contains respectively 1 or 2, at least 3, at least 4, at least 1 1, and at least 13 pits. Only in one specimen is the I4 arc complete frontally, pits of I4 usually being developed from R3. R4, R5, or R6 outwards. One specimen, however, appears to show a single pit of I4 at about RIO. Pits of I„ are frequently rather larger than those of the other arcs. The posterior row contains between 9 and 13 pits. Lists do not appear to be developed. The girder is broad and deep with weak, closely spaced terrace lines. Pygidium (PI. 98, fig. 9) sub-triangular in outline, broad (tr.), the sagittal length only about one-third PRICE: TRETASPIS FROM THE ASHGILL OF WALES 769 of the maximum width ; postero-lateral margins moderately convex ; bluntly rounded posteriorly. Maximum pygidial width about four and a half times anterior width of axis. Latter tapers posteriorly at about 25° and is gently convex (tr.). Ring furrows shallow, gently arched forward, each containing a pair of deep apodemal pits a short distance from the axial furrows ; axis bears eight such pairs of pits in all, the posterior- most pair usually only weakly developed. Pleural lobes flat, with up to four faintly defined pleural ribs. There is no submarginal rim. Population C Plate 99. figs. 1-5 Material, horizon, and locality. Twenty-four specimens in the collection of the Geological Survey, from the basal Ty’n-y-twmpath Beds of the Northern Berwyns; Locality 47 of Wedd et al., 1927 (p. 41 ), in the head- waters of the Nant-y-Lladron, about 5 km south-south-east of Corwen. Most of this material is distorted and/or fragmentary and the comments below are effectively based on less than half of it. Description. Cephalon similar in over-all morphology to that described for specimens of Population A, with the surfaces of the pseudofronta! and genal lobes smooth and with the latter, although steep antero- laterally (PI. 99, fig. 1), not overhanging the fringe. No 3p lateral glabellar furrows have been seen in the present material. Fringe with well-developed brim. Ej, Ej, and P pits arranged in deep radial sulci except on posterior parts of prolongations. Ij and Ij arcs complete frontally on all available material. The I4 arc is variably developed. On 2 specimens (PI. 99, figs. 1, 3) it is definitely not developed and on a third it appears to be absent also. On 3 other specimens I4 is developed though the number of pits is difficult to estimate. On the original of Plate 99, fig. 5 at least 3 and possibly 5 pits are present, on the original of Plate 99, fig. 4, 2 pits are clearly present opposite the axial furrow and up to 7 further pits may be present sharing sulci with pits of I„; a third specimen shows at least 2 and possibly 3 or 4 I4 pits. The pits of the In arc tend to be large (PI. 99, figs. 1, 3, 4). The number of pits in the E, arc is difficult to count accurately due to fringe distortion but estimates on 4 specimens are as follows: 27 or 28, about 29, 28 or 29, about 28. There are 1 1 pits in the posterior row (3 specimens). Two pygidia are far too distorted for their proportions to be of any use. One of them (GSM LW836) shows at least 7 pairs of apodemes. Discussion. The material of T. m. colliciuia described by Ingham (1970, pp. 53-54, pi. 8, figs. 8-20; text-fig. 14/?) from the lower part of the Pusgillian Stage of the Cautley Mudstones shows less variation in fringe characters than the forms described here. Even so, the variation does encompass a frontally incomplete I3 pit-arc and up to two or three pits in the I4 arc. Population A is thus relatively close to T. m. coUiquia while Population B of the Welsh material differs more markedly in the relatively more frequently and more extensively developed I4 arc. In this respect it is nearer to T. m. moeldenensis in which, however, the I3 arc is invariably complete and in which no specimen has yet been seen with less than ten pits in the I4 arc (text-fig. 1). All the Welsh material differs from T. m. colliquia in apparently lacking the faint pseudo- frontal lobe reticulation seen in the latter and in that the genae do not definitely overhang the fringe. Pygidia, though relatively poorly known, differ too in that none shows definitely more than eight pairs of apodemal pits on the axis. Another small sample of a form belonging within T. moeldenensis (s.l.) comes from the basal Ashgill Mudstones of the stream section south of the old quarry at Pen-y- garnedd, about 20 km north-west of Welshpool, Powys (Locality 1 of Wedd et al. 1929, list, p. 61). Of 8 specimens known, only 3 are complete enough and well-enough preserved to yield useful data. SM A42898 has 29 or 30 pits in the Ej arc, 6 pit-arcs (Ei_2r I1-3, In) anteriorly from R1 to R4 and has the I4 arc developed from R5 to at least R13 (i.e. at least 9 pits are present); a specimen on the same block (SM A94999) shows at least 8 I4 pits. The third specimen, however, GSM WK 389, shows no sign 770 PALAEONTOLOGY, VOLUME 20 of the I4 arc even in the axial furrow region, although I3 is complete. Again the varia- tion is considerable though still well within the range seen, for instance, in Population B described above. Clearly a larger sample is needed before the relationships of this form can be properly assessed. Tretaspis moeldenensis moeldenensis Cave, 1960 Plate 99, figs, 6 9, ?10; ?Plate 100, fig. 1 ; text-fig. 1 1909 Trinucleus fimbrialus Murch.; Strahan el al., p. 56. 71921 Trinucleus sp.; Wills and Smith (pars), table, p. 187. 71927 Trinucleus sp.; Wedd et al. (pars), list, p. 40. 71928 Trinucleus seticornis group; King, lists, p. 698. 1960 Tretaspis moeldenensis Cave, pp. 334-337, pi. 10, tigs. 1-7. 1973fl Tretaspis moeldenensis Cave; Price, tables 3 and 4. 1974 Tretaspis moeldenensis Cave; Price, pp. 844-847, pi. 112, tigs. 10 12; pi. 113, figs. 1-4; text-fig. 1. Holotype. As under T. moeldenensis (s.l.) above. Horizons and localities. Apart from its presence in a thin basal horizon of the Sholeshook Limestone Forma- tion of South Wales (Localities 17, 24a, and 25 of Price 1973a), the subspecies is here tentatively recognized from (locally) basal or near-basal Ashgill strata at two localities in the Berwyn Hills. Discussion. Topotype material of T. m. moeldenensis has already been redescribed in detail (Price 1974, see synonomy), though fringe characters were dealt with at that time on the basis of rather small samples (Price 1974, text-fig. 1). However, to allow clear distinctions to be made between T. m. moeldenensis and other closely related forms, it was considered desirable to work with much larger samples and extensive re-collecting of topotype material was undertaken. This has resulted in a much- increased knowledge of fringe characters as shown by the histograms in text-fig. 1. (The I3 arc, where seen frontally, is invariably complete.) Larger samples of topotype pygidia show that larger and better preserved specimens occasionally bear nine pairs of apodemes on the axis, though the last pair is usually very faint (PI. 99, fig. 9). Eight is the much more usual number (PI. 99, fig. 6) and even then the posterior-most pair is often faint. A small sample of Tretaspis from a locality (Locality 36 of Wedd et al. 1927, p. 41) EXPLANATION OF PLATE 99 Figs. 1-5. Tretaspis moeldenensis Cave (s.l.). Population C, basal Ty’n-y-twmpath Beds, headwaters of Nant-y-Lladron, south of Corwen. 1, GSM JM 3908, cast from partial external mould of cephalon, anterior view, x6. 2, GSM JM 3905, incomplete internal mould of cephalon, dorsal view, x4. 3, GSM LW 832, partial internal mould of cephalon, anterior view, x6. 4, GSM LW 844, cast from partial external mould of cephalon, left-lateral view, x 5. 5, GSM LW 835, partial internal mould of cephalon, antero-dorsal view, X 6. Figs. 6-9. Tretaspis moeldenensis moeldenensis Cave, basal Sholeshook Limestone Formation, Moldin, near Llandowror. 6, SM A77741, internal mould of pygidium, dorsal view, x 5. 7, 8, SM A94951a, internal mould of cephalon, anterior and left-lateral views, x 5. 9, SM A77734, incomplete internal mould of pygidium, dorsal view, x 6. Fig. 10. ITretaspis moeldenensis moeldenensis Cave, GSM LW 1289, internal mould of cephalon, low Ty’n-y-twmpath Beds, headwaters of Nant-y-Lladron, south of Corwen, anterior view, X 6. PLATE 99 PRICE, Tetraspis from Wales in PALAEONTOLOGY, VOLUME 20 in the Ty’n-y-twmpath Beds of the Northern Berwyns, close to and stratigraphically perhaps 40 m above that from which Population C of T. moeldenensis (s.l.) was col- lected, appears to belong with T. m. moeldenensis. External moulds show the cephalon to be non-reticulate. Three specimens show, in addition to a complete I3 pit-arc, at least 14 (PI. 99, fig. 10), at least 10 (PI. 100, fig. 1) and 9 or 10 (GSM LW 1297) pits in I4. In the original of Plate 99, fig. 10, I4 pits are absent for \\ rows frontally; the position in the original of Plate 100, fig. 1 is not clear. In the 3 specimens referred to, the I4 pits, apart from being more extensively developed than in specimens of the slightly older Population C of T. moeldenensis (s.l.), are larger and more clearly separated from the I „ pits, not closely associated with them as they are when developed in specimens of the latter form and the I„ pits themselves are not noticeably large. A fourth specimen (GSM LW 1310) is a distorted pygidium which appears to show at least 8 pairs of apodemal pits. A form first recorded by King (1928, p. 681) from the basal Ashgill Mudstones near Glyn Cottage at the head of Cwm Nant-y-meichiaid, 3 km north-west of Meifod, may also belong here. Material collected by the author (SM A94800-9481 1, A94826- 94830, and 94832) is of a non-reticulate form with 26 or 27 pits in Ej (one specimen in each case). Seven specimens showing the appropriate regions of the fringe have a complete I3 pit-arc and an extensive I4 arc developed. On one specimen I4 is incomplete frontally for 2 radii and on 4 others for an indeterminate but small number. In the first specimen I4 extends from R3 to R14 (i.e. 11 pits), in 2 others to around R16. Two further specimens show respectively 1 1 and at least 10 pits in I4 and a fringe fragment shows part only of an I4 arc with 7 pits. The posterior row shows 10, 11, 12 (1 specimen each), or (in 3 specimens) 13 pits. An incomplete pygidium shows 7 or 8 pairs of apodemes on the axis. For other material not described here but regarded as belonging within T. moelde- nensis (s.l.) (see synonomy of that form), there is insufficient fringe data, particularly in relation to the extent of the I4 pit-arc, to establish its relationship with T. m. moeldenensis. Tretaspis cf. radialis Lamont, 1941 Plate 100. figs. 2-10; text -fig. 1 1909 Triniicleus sp.; Strahan el al., table, p. 58. 1912 Triniicleus seticornis (Hisinger); Reed, p. 391, pi. 19, fig. 5, 5a. EXPLANATION OF PLATE 100 Fig. 1. ITretaspis moeldenensis moeldenensis Cave, GSM LW 1311, internal mould of cephalon, low Ty’n-y-twmpath Beds, headwaters of Nant-y-Lladron, south of Corwen, antero-lateral view, x 6. Figs. 2-10. Tretaspis cL radialis Lamont, Sholeshook Limestone Formation of Sholeshookand Prendergast, Haverfordwest, x 5. 2-4, BM It. 9200, internal mould of cephalon partially retaining exoskeleton, topmost Locality 8d, anterior, left-lateral, and dorsal views. 5, BM It. 9259, incomplete internal mould of cephalon, topmost Locality 8d, right-lateral view, x 5. 6, BM It. 9252, cast from incomplete external mould of cephalon, topmost Locality 8d, oblique view. 7, SM A85138, incomplete internal mould of pygidium. Locality 9h, dorsal view. 8, 9, SM A77523a, b, internal mould and cast from external mould of cephalon. Locality 9e, right-lateral and left antero-lateral views. 10, SM A3 1529, internal mould of pygidium and posterior part of thorax of enrolled specimen, Sholeshook, dorsal view of pygidium. Locality numbers are those of Price 1973a. PLATE 100 PRICE, Tetraspis from Wales 774 PALAEONTOLOGY, VOLUME 20 1914 Trirnicleus seticomis, Hisinger; Reed, pi. 28, iig. 5, 5a. 1914 Trinucleus seticomis (His.); Strahan et al. (pars), table, p. 64. 1914 Trinucleus seticornisl (His.); Strahan et al., table, p. 64. 1938 Tretaspis cf. kiaeri Stormer; Whittington, list, p. 452. 1945 Tretaspis ceriodes var. sortita; Lamont, p. 123. 1966 Tretaspis aff. kiaeri Stormer radialis Lamont; Ingham, pp. 467, 470, 471, 486, 499-501. 1966 Tretaspis kiaeri Stormer; Whittington (pars), p. 91. 1968 Tretaspis kiaeri Stormer; Whittington (pars), pi. 29, figs. 1, 2, 4 only. 1970 Tretaspis cf. radialis Lamont; Ingham (pars), pp. 55-57, pi. 9, figs. 8-16, 20; text-figs. \Ad, 19; non pi. 9, figs. 17-19. 1973a Tretaspis cf. radialis Lamont; Price (pars), pp. 229, 234, 236, 238-239, 242; tables 1-5. 19736 Tretaspis cf. radialis Lamont; Price, pp. 538-540. 1974 Tretaspis cf. radialis'. Price (pars), p. 847. Lectotype. Subsequently selected by Dean 1961, p. 124, SM A16202, original of Lamont 1941, text-fig. 5, p. 497; from the Portrane Limestone, Portrane, Co. Dublin. Material, horizons, and localities. This description is based on some forty-five specimens from the Shole- shook Limestone Formation of South Wales. In the type development at Sholeshook and Prendergast (Haverfordwest, Dyfed) the species is common throughout all but the topmost four metres of the forma- tion, the highest occurrence being in topmost Locality 8d of Price 1973a. Around Llandowror it appears to range through most of the formation but is absent from the basal Moldin horizon (Localities 17, 24a, 25) and is not known with certainty above Locality 18a. One other occurrence, in Mid-Wales, is noted in the discussion. Description. Cephalon sub-semicircular in dorsal view. Pseudofrontal lobe of glabella occupying two- thirds of sagittal length; sub-spherical in form, standing high above level of genal lobes and overhanging fringe in lateral view (PI. 100, fig. 3); strongly reticulated and apically bearing a small median tubercle. Occipital ring narrow and strongly convex (sag. and exsag.), orientated postero-dorsally, abaxially curving forwards. Occipital furrow broad (sag. and exsag.) and shallow mesially, abaxially containing deep, ovoid apodemal pits. Ip lateral glabellar lobes short (tr.), convex, abaxially rounded. Ip lateral furrows in form of deep, strongly oblique apodemal slots, converging anteriorly at 120-130°. 2p lateral lobes only gently convex (exsag.), set transversely, narrowest (exsag.) adaxially, broadening outwards and merging anteriorly with the pseudofrontal lobe around the 2p lateral furrows (PI. 100, figs. 4-6). Latter in form of large, deep, ovoid pits, diverging anteriorly at about 140°. On well-preserved specimens the 3p lateral furrows are clearly visible as shallow, elongate-ovoid pits on the sides of the pseudofrontal lobe, slightly behind its mid-length (PI. 100, fig. 6). Axial furrows broad (tr.) posteriorly, narrowing forwards and constricted slightly on about level of 3p lateral furrows at the adaxial ends of faintly developed eye-ridges; at anterior ends containing deep, round anterior fossulae of about the same size as the pits of the arc of the fringe. Genal lobes sub-quadrant shaped; convex (tr. and exsag.), bearing prominent lateral tubercles at the level of the anterior margins of the 2p lateral furrows; variably reticulated, sometimes strongly, sometimes not at all. Where reticulation is absent, the faint eye-ridge referred to above may be seen on the external surface running obliquely forwards from the lateral tubercles to the level of the 3p furrows (PI. 100, fig. 6). Genal lobes drop steeply to broad (exsag.), adaxially shallow posterior border furrows. Posterior borders narrow (exsag.) and gently convex (exsag.) adaxially, broadening outwards. Fringe with steeply inclined, convex genal roll ; brim narrow anteriorly but broadening laterally. Internal moulds show a broad, deep girder with fine, closely spaced terrace lines (PI. 100, fig. 8). Arrangement of pits similar to that in T. moeldenensis (s,.).), the strict radial alignment only breaking down on the genal prolongations. There are 6 completely developed pit-arcs, Ej ,, Ii_3, In' a variably developed I4 arc. In 8 out of 10 specimens showing the pit arrange- ment frontally, the I4 arc is complete in front of the glabella, while in both of those remaining I4 pits are absent from R1 (text-fig. 1). The number of pits in I4 ranges from 10 to 18 (half-fringe), the pits merging with those of the I„ arc between R12 and R19. The Ei arc has from 24 to 28 pits in the half-fringe. Pits of E2 are absent from the posterior-most row and occasionally from the posterior-most 2 rows; the posterior row contains from 9 to 1 1 pits. As in T. moeldenensis, the sulci containing E2, Ej, and L pits anteriorly and antero-laterally on the upper lamella tend to contain only the Ej and E2 pits on the genal prolongations (PI. 100, fig. 9), where the sulci containing the Ii_n pits on the lower lamella also break down (PI. 100, fig. 8). PRICE: TRETASPIS FROM THE ASHGILL OF WALES 775 Well-developed lists separate the pits of the Tares anteriorly on the upper lamella (PI. 100, hgs. 6, 9; see also Whittington 1968, pi. 29, hg. 1 ) and may persist laterally to around R14 or R15. Thorax poorly known but apparently similar to that described below for T. aff. radialis. Pygidium (PI. 100, figs. 7, 10) similar in over-all form to those described for Population B of T. moeldenensis (s.l.) though with axis relatively slightly broader (tr.), occupying about one-quarter of total width anteriorly, tapering posteriorly at about 25° and bearing, in well-preserved specimens, seven pairs of apodemal pits, though frequently only six are visible in poorer specimens. Pleural lobes on available material poorly preserved. Discussion. This form is synonymous with T. cf. radialis described by Ingham (1970) from the Cautleyan and low Rawtheyan Stages of the Cautley Mudstone Formation. Ingham concluded (1970, pp. 56-57) that this form is more likely than T. m. moelde- nensis and related forms to be identical with T. radialis Lamont from the Portrane Limestone. Whether or not this is the case (and the issue is now further complicated by the presence of a third related species in the Welsh faunas— T. aff. radialis, see below), separation of the form from T. m. moeldenensis is justified on the basis of several morphological differences. Apart from the pit-count differences in the fringe (text- fig. 1) which mainly relate to the number of pits in Ej and in the posterior row, the distinction is based on the degree of inflation of the pseudofrontal glabellar lobe, the presence or absence of reticulation, the presence or absence of 3p lateral furrows and of well-developed lists, the degree to which the brim is developed anteriorly, and the number of pairs of apodemal pits on the pygidial axis. T. cf. radialis has also been collected by the author (Price 19736, p. 539) (specimens SM A94697, A94701, 94704, 94712, and 94718) from a quarry at Ty-isaf-mawr near Llantsantffraid-ym-Mechain in the Berwyns, a locality which Whittington (1938, his Locality 53) included in the " Diacalymene marginata Zone’ of the Lower Tre-wylan Beds. Tretaspis aff. radialis Lamont, 1941 Plate 101, figs. 1-7; text-fig. 1 1914 Trinucleus seticornis (His.) ’, Strahan et al. (pars), tables, pp. 64, 75. 1914 Trinucleus seticornis (His.), var. bucklandi (Barr.); Strahan et al., table, p. 75. 1914 Trinucleus sp. ; Strahan et al., table, p. 75. 1923 Trinucleus sp.; King (pars), list, p. 495. 71970 Tretaspis cf. radialis Lamont; Ingham (pars), pi. 9, figs. 17-19 only. 1973fl Tretaspis cf. radialis Lamont; Price (pars), pp. 229, 238-239, 242; tables 1, 2, 5. 1974 Tretaspis cf. radialis’. Price (pars), p. 847. Material, horizons, and localities. This form replaces T. cf. radialis in the topmost four metres of the Sholeshook Limestone Formation of Prendergast Place (Localities 8c, 8b of Price 1973a) and continues into the overlying Slade and Redhill Mudstone Formation (Locality 8a). It is the only species of Tretaspis known from the exposures in the latter formation at Redhill Quarry (Locality 7 of Price 1973a). Material from these sources totals thirty-nine specimens (of which twenty-four are from the topmost Sholeshook Limestone). A further occurrence at Aber-marchnant in the south-west Berwyns is noted in the discussion. Description. In over-all cephalic morphology this form does not differ appreciably from T. cf. radialis, except in the extent of surface reticulation. On the pseudofrontal glabellar lobe, reticulation is subdued and appears to be confined to the post-apical region (just visible, for instance, on PI. 101, fig. 7); the genal lobes on all known specimens are smooth. The main difference between the two forms is in the development of the L pit-arc of the fringe. Of 18 specimens of T. aff. radialis showing the frontal area of the fringe, one-third had no T pits at all and the remaining 12 had short L arcs of between 1 and 4 pits (text-fig. 1). 776 PALAEONTOLOGY, VOLUME 20 When present, this short arc is developed between R2 and R6 with at least 1 and possibly as many as 5 pits absent frontally (half-fringe). There may also be a tendency for the Ej arc in T. aff. radialis to contain slightly fewer pits than that in T. cf. radialis (text-fig. 1 ). Otherwise the arrangement of pits is similar in both forms, with the Ij arc invariably complete. Thorax (PI. 101, fig. 3), known from single, poorly preserved specimen, of six segments. Axis occupies about one-third of total width (tr.) anteriorly, gradually tapering posteriorly, only gently convex (tr.). Axial rings separated by broad (sag. and exsag.) articulating furrows containing deep, ovoid apodemal pits a short distance from the axial furrows. Axial furrows rather shallow. Pleurae broad (exsag.), flat, apparently horizontal for most of length (tr.). Pygidium similar in over-all form to those described previously with axis occupying slightly over one-quarter of total width (tr.) anteriorly, tapering back at 25-30° and bearing six or seven pairs of apodemal pits. Pleural lobes on available material again poorly preserved. Discussion. T. aff. radialis is readily distinguished from both T. cf. radialis and T. m. moeldenensis by virtue of its very short or absent I4 pit-arc. In this respect, however, the fringe is very similar to that of T. m. colliquia. This last form does show some fringe differences such as the anteriorly well-developed brim, the occasionally incomplete I3 arc, and the large I„ pits. There are differences, too, in the degree of inflation of the pseudofrontal glabellar lobe, the degree to which the genal lobes overhang the fringe and in pygidial characters, particularly the relatively broader and more rapidly tapering pygidial axis of T. aff. radialis with its fewer pairs of apodemal pits. So far as the Welsh populations of T. moeldenensis (s.l.) described herein are concerned, these show much greater variation in the development of the I4 arc in addition to most of the differences listed above. Lamont (1941, p. 456) originally described T. kiaeri radialis on the basis of two fragments from the Portrane Limestone of Co. Dublin, Eire. Of these, the lectotype, SM A 16202, has at least twelve pits clearly visible in the I4 arc and the remaining syntype, SM A 16203, appears to have had an extensive I4 arc as well. The form described above is not, therefore, thought likely to prove identical with T. radialis. Nevertheless, redescription of the latter form from topotype material and clarifica- tion of the status of related forms is clearly urgent. A further sample of 12 specimens of T. aff. radialis comes from the (locally) basal Ashgill strata of Aber-marchnant in the south-west Berwyns (locality al of King, EXPLANATION OF PLATE 101 Figs. 1-7. Tretaspis aff. radialis Lamont. 1, SM A94505, cast from partial external mould of cephalon, basal Ashgill Mudstones, Aber-marchnant, south-west Berwyns, oblique view, x 5. 2, BM It. 9203, partial internal mould of cephalon, basal Slade and Redhill Mudstones of Prendergast Place, Haverford- west, oblique view, x5. 3, SM A77860a, internal mould of articulated exoskeleton, basal Slade and Redhill Mudstones of Prendergast Place, dorsal view, x 4. 4, SM A3 1597, internal mould of pygidium, high Sholeshook Limestone of Prendergast Place, dorsal view, x 6. 5, SM A56043, partial internal mould of cephalon, topmost Sholeshook Limestone of Prendergast Place, oblique view, x 5. 6, SM A94507a, partial internal mould of cephalon, horizon, and locality as for fig. 1, oblique view, x 6. 7, SM A94998, cast from partial external mould of cephalon, horizon and locality as for fig. 5, anterior view, x 5. Fig. 8. Tretaspis sp. indet. A, BM It. 8953, cast from external mould of pygidium, Birdshill Limestone, Birdshill Farm, near Llandeilo, dorsal view, x 6. Figs. 9, 10. Tretaspis hadelandica Stormer, brachysticlnis Ingham. 9, BM It. 9275, incomplete internal mould of cephalon. Sholeshook Limestone horizon at Robeston Wathen (Locality 10a of Price 1973a), dorsal view, x6. 10, SM A77794, incomplete internal mould of cephalon, horizon and locality as for fig. 9, antero-lateral view, x 6. PLATE 101 PRICE, Tetraspis from Wales 778 PALAEONTOLOGY: VOLUME 20 1923). One specimen has 23 pits in Ej. The number of pits in the posterior row is 11 in 2 specimens and 12 in a third though the original of Plate 101, fig. 1 shows only 6! The number of pits in varies from 0 (1 specimen) through 1 and 2 (1 specimen in each case, in the latter the original of PI. 101, fig. 1) to 4 or 5 (original of PI. 101, fig. 6). Two external moulds show subdued reticulation on the posterior part of the pseudofrontal glabellar lobe. In all other general features the material resembles T. cf. radialis. What makes its identity with T. aff. rcidialis of further interest is its occurrence at Aber-marchnant together with T. hadelandica Stormer brachy- stichus Ingham and Kloucekia robertsi (Reed), a situation exactly paralleled with T. aff. radialis in the high Sholeshook Limestone (see Price 1973a, p. 229 and table 2). Ingham (1970, pi. 9, figs. 17-19) has figured, among forms which he refers to T. cf. radialis, a specimen from Zone 5 of the Rawtheyan Stage in the Westerdale Inlier which appears to have only four pits in the I4 arc and which on the cast from the external mould does not appear to be obviously reticulated. It is conceivable that this and other forms referred to T. cf. radialis in the topmost part of its range might belong with the forms described here as T. aff. radialis. Ingham (1970, p. 56) notes an association with T. hadelandica bracliystichus and it is from Zone 5 also that Kloucekia cf. robertsi is recorded (Ingham 1966, table 2). Tretaspis sp. indet. A Plate 101, fig. 8 1973fl Tretaspis of T. moelderiensis group; Price, list, p. 244. Material, horizon, and locality. Eight specimens from the Birdshill Limestone of the old quarry 180 m north-west of Birdshill Farm, 2-5 km west-north-west of Llandeilo, Dyfed. These specimens (BM It. 8946-8948, 8950-8954) comprise 4 fragments of fringe and 2 internal moulds and 2 external moulds of pygidia. Description. The fringe fragments show that the pits are arranged in strict radial alignment and with the following arcs developed in all 4:Ei_2, Ii_3, I„. One fragment appears to show 1 or 2 pits of an I4 arc. On the upper lamella the E,, Ej, and Ij pits are contained in radial sulci and all the internal arcs are arranged in such sulci on the lower lamella. The Ej pit is absent from the posterior row. Pygidium (PI. 101 , fig. 8) sub-triangular in outline, broad (tr.), maximum width three times sagittal length. Postero-lateral margins convex, posterior bluntly rounded; these margins strongly bevelled from a distinct sub-marginal rim. Axis narrow, occupying about one-fifth of maximum width (tr.) anteriorly and tapering back at about 25°; moderately convex (tr.). Ring furrows shallow mesially, gently arched forward, each containing a pair of prominent apodemal slots abaxially. Eight such pairs of slots are visible, the posterior- most markedly fainter than the rest. Axial furrows shallow. Pleural lobes nearly flat, horizontal, crossed by four distinct, broad pleural ribs and a faint fifth; ribs separated by shallow pleural furrows and each with faint interpleural furrows. Discussion. The sparsity and fragmentary nature of the available material precludes detailed comparison with other forms. A close similarity may be noted, however, between the pygidia described above and topotype pygidia of T. m. moeldenensis (PI. 99, figs. 6, 9). PRICE: TRETASPIS FROM THE ASHGILL OF WALES 779 THE TRINUCLEUS SETICORNIS GROUP For the characteristics of the group see Ingham 1970, p. 41. Tretaspis hadelandica Stormer, 1945, hrachystichus Ingham, 1970 Plate 10), figs. 9, 10; Plate 102, figs. 1-5; text-fig. 2 1885 Trimicleus seticornis. His.; Mart and Roberts (pars), p. 480 (centre). 1914 Trimicleus seticornis (His.); Strahan et al. (pars), tables, pp. 64, 75. 1914 Trinucleus seticornis (His.), var. hucklandi (Barr.); Strahan et al. (pars), tables, pp. 64, 75. 1914 Trinucleus seticornis (His.), var. ; Strahan et al., table, p. 75. 1923 Trinucleus sp.; King (pars), list, p. 495. 1938 Tretaspis ceriocles (Angelin); Whittington, list, p, 452. 1938 Tretaspis sp.; Whittington (pars), list, p. 452 (bottom). 1965 Tretaspis seticornis anderssoni Stormer; Cave, p. 296. 1970 Tretaspis hadelandica Stormer brachysticlms Ingham, pp. 46-49, pi. 6, figs. 13-19; pi. 7, figs. 1-7; text-figs. 14/i 16. 1973n Tretaspis cf. hadelandica Stormer hrachystichus Ingham; Price, pp. 229, 233-234, 237, 239; tables 1-3, 5. 1975 Tretaspis cf. hadelandica Stormer hrachystichus Ingham; Cocks and Price, pp. 705-706, pi. 81, figs. 8, 9. Holotype of subspecies. Figured Ingham 1970, pi. 6, fig. 15, HUD 4.10, an enrolled specimen from the Rawtheyan Stage, Zone 5, of the Cautley Mudstone Formation. Material, horizons, and localities. The following description is based on samples totalling thirty-five specimens from the high Sholeshook Limestone and basal Slade and Redhill Mudstone Formations of the areas around Haverfordwest, Robeston Wathen, and Llandowror, Dyfed (Localities 8a, 8b, 9d, 10a, 15, and 22 of Price 1973) and a further sample of fourteen specimens from the high Slade and Redhill Mudstone Formation of Haverfordwest (Locality I of Cocks and Price 1975). When histograms of fringe data are plotted separately for these two sets of specimens there are no appreciable differences. They are therefore treated together in the histograms on text-fig. 2 and in the description. Occurrences in the Ashgill Series of the Berwyn Hills and of the Lleyn Peninsula are noted in the discussion. Description. Cephalon approximately semicircular in dorsal view. Pseudofrontal lobe of glabella sub- spherical in form, standing high above level of genal lobes, occupying almost two-thirds of total glabellar length (sag.), and apically bearing a small median tubercle. Occipital ring narrow and strongly convex (sag. and exsag.), strongly arched (tr.), and orientated postero-dorsally. Occipital furrow broad (sag. and exsag.) and shallow mesially, abaxially containing deep, ovoid apodemal pits. Ip lateral glabellar lobes short (tr.), convex, abaxially rounded. Ip lateral furrows deep, slot-like, converging anteriorly at 140-150°. 2p lobes gently convex (exsag.), set transversely, narrowest (exsag.) adaxially, broadening outwards. 2p lateral furrows in form of large, ovoid pits, diverging anteriorly at 150-160°. Well-preserved ex ernal moulds show the presence of a faintly developed pair of depressions on the sides of the pseudofrontal lobe representing the 3p lateral furrows. Axial furrows broad (tr.) posteriorly, less so anteriorly where they contain deep anterior fossulae of about the same size as the pits of the arc of the fringe. Genal lobes sub-quadrant shaped, steeply declined antero-laterally, not overhanging fringe; bearing prominent lateral tubercles on the level of the anterior margins of the 2p lateral furrows. In all external moulds so far examined, the surface of the glabella has been coarsely reticulated. In all but two of these external moulds the entire surface of the genal lobes has also been coarsely reticulated (PI. 102, fig. 4; Cocks and Price 1975, pi. 81, fig. 9). Specimens GSM Pg, 216 and Pg. 226, however, both from the high Sholeshook Limestone of Prendergast Place, Haverfordwest (Locality 8b, Price 1973) and similar in all other respects, including glabellar reticulation, show completely smooth genal lobe surfaces. The genal lobes drop steeply to broad, deep posterior border furrows which contain large posterior fossulae abaxially. Posterior borders narrow (exsag.) abaxially, broadening outwards. Fringe with anteriorly steep, gently convex genal roll; a gently curled brim is developed laterally. Genal prolongations rather short (PI. 101 fig. 10), produced into stout 780 PALAEONTOLOGY, VOLUME 20 genal spines which project beyond the posterior margin of the pygidium (PI. 102, fig. 2). Genal spines with narrow dorsal groove and a strong ventral ridge which is continuous with the prominent girder; the latter carries a few faint, widely spaced terrace lines. The half-fringe contains from 18 to 23 pits in the Ej arc (text-fig. 2). Anteriorly these pits are contained in sulci with pits of the Ij arc but beyond about R7 the 2 arcs become separate (PI. 101, fig. 10). The Ej arc is only developed postero-laterally where from 8 to 14 pits share sulci on the upper lamella with pits of the Ej arc. Ej pits are absent from the posterior row which contains from 7 to 10 pits, most usually 7 or 8. Pits in the arcs to are developed in separate aR radii which are out of line with the bR radii containing the Ei_, and Ij pits (PI. 101, fig. 10; PI. 102, figs. 4, 5). In front of the axial furrows pits of arcs I2, I3, and are developed but the I3 arc merges with the arc both laterally and in front of the glabella. The number of pits in this short I3 arc is usually between 3 and 6 in the available material though one specimen (GSM Pg. 226) shows only a single pit; from 1 to 3 pits (half-f inge) are absent in front of the glabella. Lists may be developed on the upper lamella of the fringe separating the I, and Ij arcs up to about aR6 and the I2/I3 and 13/Ij, arcs over the region in which I3 is developed. On the lower lamella pits of the l2-In arcs lie in deep radial sulci forward of the genal prolonga- tions. One of the fringes examined shows a slight irregularity antero-laterally where, in aRlO, a single pit of the I2 arc is absent and appears to have merged with the rather large I„ pit in the same radius (PI. 101, fig. 10). Thorax, known only from single internal mould (PI. 102, fig. 2), of six segments. Axis occupies about one-third of total width (tr.) anteriorly. Axial rings moderately convex (tr.), slightly arched forward mesially, separated by bro; d (sag. and exsag.) articulating furrows which contain deep, ovoid apodemal pits a short distance from the axial furrows. The elongated median tubercle near the anterior margin referred to by Ingham (1970, p. 48) and the associated row of small, sub-circular projections are not seen in this specimen. Axial furrows shallow. Pleurae directed transversely, straight, and horizontally for most T. hadelandicQ brachystichus Pits in El Pits in E2 Pits inis Pits in I3 absent Pits in frontally posterior row T. cf. latilimbus distichus >v u c Pits in El Pits in E2 Pitsinl4 Pits in posterior row T.cf.sortita Pits in El n=7 8'9'lo'M '12' Pits in E2 9IOIII2I3 l4 extends to (R no ) 0 12 3 4 Pits in Is 2 3 4 5 Pits in Is absent frontally 7 8 9I0II Pits in posterior row TEXT-FIG. 2. Histograms of selected fringe characters in species of Tretaspis of the T. seticornis group, n is the sample number for each character shown. All histograms show half-fringe data. T. hadelandica brachystichus from highest Sholeshook Limestone Formation and Slade and Redhill Mudstone Formation of Haverfordwest, Robeston Wathen, and Llandowror areas, Dyfed. T. cf. latilimbus distichus from "Calymene quadrata Mudstones’ of south-west Berwyns. T. cf. sortita from highest Ashgill strata of Craig- wen Quarry, near Meifod, Powys. PRICE: TRETASPIS FROM THE ASHGILL OF WALES 781 of length (tr.), deflected ventrally and slightly posteriorly at distal extremities. Broad (exsag.) pleural furrows are directed obliquely along each pleura. Pygidium sub-triangular in form, about three times as broad (tr.) as long (sag.). Postero-lateral margins moderately convex, strongly bevelled, and covered in fine, sub-parallel terrace lines (PI. 102, fig. 3). A strong sub-marginal rim is developed. Axis rather over one-quarter the maximum pygidial width anteriorly ; crossed by six shallow, forwardly arched furrows, the posterior-most of which is extremely faint and each of which contains a pair of deep apodemal slots a short distance in from the axial furrows. Axial furrows shallow, converging posteriorly at about 35°. Pleural lobes horizontal; crossed by four pairs of divergent pleural furrows. Up to two pairs of very faint, narrow interpleural furrows are sometimes visible. Discussion. The form described above is very similar in both over-all morphology and fringe characters to that described by Ingham (1970, see synonomy) as T. hacle- landica brachystichiis subsp. nov. from the Rawtheyan and ?Cautleyan Stages of the Cautley Mudstone Formation and the two are regarded here as synonymous. The only major difference is in the degree of genal lobe reticulation which in mature individuals of the North of England populations affects only the posterior parts of the lobes. In view of the two Welsh specimens mentioned above with completely smooth genal lobes and in view of the great variability of reticulation in the other Welsh samples discussed below, it is thought that this difference may be of purely local (adaptive) significance. Twelve specimens from the Crugan Mudstones of the Lleyn Peninsula (BM It. 9350-9353, 9355-9358, 9360-9362, and 9419) from an exposure at Berllan Cottage, 1-8 km north of Llanbedrog, also belong with this form (see PI. 102, fig. 5) as do small samples from the following horizons and localities within the Ashgill Series of the southern Berwyn Hills: Locality 54 of Whittington 1938, an exposure by the side of a track 450 m north of the crossroads at Cefn-y-blodwel, 1-5 km north-north-west of Llanyblodwell, Powys and within Whittington’s " Diacalymene drummuckensis Zone’ of the Lower Tre-wylan Beds; Locality 61 of the same author which lies just below the basal Llandovery near Gelli Farm, 1-75 km south-east of Llansantffraid-ym- Mechain ; and Locality al of King 1923, in (locally) basal Ashgill strata 140 m north- east of Aber-marchnant Farm, 2 km east of Llanwddyn. The fringe characters of all these samples fall within the range given for the South Welsh forms. In spite of this, there is extreme variation in the degree of surface reticulation. External moulds from the Berllan Cottage material show no sign of either glabellar or genal lobe reticula- tion while reticulation on the specimens from Whittington’s Locality 54 is so coarse on both the glabella and genal lobes as to be clearly visible on the internal moulds. Ingham (1970, p. 49) has distinguished T. hadelandica brachystichiis from T. h. hadelandica, T. seticornis seticornis, and other related Scandinavian forms. Tretaspis cf. latilimhiis (Linnarsson, 1869) distichus Ingham, 1970 Plate 102, figs. 6-11; ?Plate 103, fig. 8; text-fig. 2 1923 Trimicleus cf. bucklandi Barrande; King, list, p. 497 (bottom). 71923 Trimicleus bucklandi Barrande; King, list, p. 498. Holotype of subspecies. Figured Ingham 1970, pi. 7, fig. 1 5, HUD 4.25, partial cephalon from the Rawtheyan Stage, Zone 7 of the Cautley Mudstone Formation. Material, horizon, and locality. The description below is based on sixteen specimens (NMW 74.6G.1-I5, 72.18G.133) from Locality A8 of King 1923, fig. 3, in the higher part of his "Calymene quadrata Mudstones’ 782 PALAEONTOLOGY, VOLUME 20 at Craig-Fawr, 3 km south-east of Hirnant in the south-west Berwyns. A further single specimen (SM A39862) from King’s Locality S6 near by may also belong here. Description. Cephalon similar in over-all form and proportions to that of T. h. brachystichus. Pseudo- frontal lobe of glabella sub-spherical in form with depressions representing the 3p lateral furrows clearly developed along its sides about midway between the anterior margins of the 2p furrows and the anterior fossulae. Neither the pseudofrontal glabella lobe nor the genal lobes overhang the fringe. Glabellar and genal surfaces strongly reticulated. The reticulation, clearly visible on internal moulds (PI. 102, figs. 9, 11), is particularly coarse on the inner posterior parts of the genal lobes (PI. 102, fig. 6) ; it is terminated posteriorly on the occiput at a transverse ridge joining the posterior parts of the Ip lateral lobes. Fringe anteriorly steep and only gently convex; the narrow, slightly curled brim is developed only laterally (PI. 102, fig. 8). Pit -arcs El, I^, and are developed both frontally and laterally with either 17 or 18 pits in Ei. Though pits of arcs I3 and appear to merge laterally on 1 or 2 specimens at around aR12 (PI. 102, fig. 7), they remain separate on others. On the upper lamella Ej and I; pits share sulci frontally up to about aR6 but form discrete arcs laterally. E2 pits are only developed laterally from bR 10 or 1 1 where on the upper lamella they share sulci with the Ej pits. Lfsually Ej pits are absent from the posterior row so that between 6 and 8 pits are present in the half-fringe. On 2 specimens, however, Ej pits are absent from the posterior-most 3 rows; these 2 specimens are responsible for the 2 lowest counts on the histogram in text-fig. 2. A short I4 arc is developed in front of the axial furrow. The number of pits can only be counted in 1 specimen where 4 are present from aR5 to aR8 (PI. 102, fig. 8). This same specimen has lists developed separating each of the internal pit-arcs. The number of pits in the posterior row is 7, 8, or 9 ( 1 specimen in each case). Thorax incompletely known. Axis moderately convex (tr.), occupying about one-third thoraxic width anteriorly. Axial rings with broad (sag. and exsag.) ring furrows which contain deep, ovoid apodemal pits abaxially— at a distance of about their own length (tr.) inside the axial furrow. Pleurae flat and horizontal for most of length (tr.), deflected ventrally and slightly posteriorly near distal tips. Pleural furrows com- mencing at inner anterior corners and running obliquely outwards and posteriorly, broadening rapidly and separating narrow (exsag.) transverse anterior bands from adaxially broad (exsag.) triangular posterior bands which narrow towards the fulcrum and have a prominent, slightly raised, oblique anterior margin. Pygidium sub-triangular in form, about three times as wide (tr.) as long (sag.). Axis occupies about one- third of total width anteriorly and tapers back at 30-35°; on available material bears six apodemes. Axial furrows broad (tr.) and shallow. Pleural lobes not well-preserved; bearing perhaps four pleural ribs. There is a well-developed marginal rim. Discussion. Although detailed comparison is hindered by the rather small amount of material, giving very low sample numbers on the histograms in text-fig. 2, the form described above does seem close to T. latilimbus distichus as described by Ingham (1970, p. 50, pi. 7, figs. 8-16; text-figs. 14g, 16) from the Rawtheyan Stage, Zone 7 of the Cautley Mudstones. The stratigraphically older form T. convergens Dean EXPLANATION OF PLATE 102 Figs. 1-5. Tretaspis hadelandica Stormer, brachystichus Ingham. 1 , BM It. 9272, incomplete internal mould of cephalon, Sholeshook Limestone horizon at Robeston Wathen (Locality 10a of Price 1973), dorsal view, X 6. 2, SM A77802a, internal mould of articulated exoskeleton, horizon and locality as for fig. 1, dorsal view, x4. 3, SM A7781 lb, cast from external mould of pygidium, horizon and locality as for fig. 1, dorsal view, x6. 4, SM A77581b, cast from external mould of cephalon, horizon and locality as for fig. 1, anterior view, x 6. 5, BM It. 9352, cast from partial external mould of cephalon, Crugan Mudstone Formation, Berllan Cottage, north of Llanbedrog, anterior view, x 6. Figs. 6-11. Tretaspis cf. latilimbus (Linnarsson) distichus Ingham, "Calymene quadrata Mudstones’, Locality A8 of King 1923, south-west Berwyns. 6-9, NMW.74.6G.lb, a, cast from external mould of cephalon in dorsal, left-lateral, and anterior views and internal mould in dorsal view, all x 5. 10, NMW. 74.6G.13, internal mould of cephalon, anterior view, x5. 11, NMW.72.18G.133, partial internal mould of cephalon, dorso-lateral view, x 4. PLATE 102 I 6 9 ;• *•**. ?'• •<’2! •Vi»J * % ■% '■% *■•.'• • • I'-i * •‘■'^ PRICE, Tetraspis from Wales 784 PALAEONTOLOGY, VOLUME 20 (1961, p. 127, pi. 9, figs. 1-6; see also Ingham 1970, pp. 45-46, pi. 6, figs. 1-12; text-figs. Me, 15) is similar in many respects to the Welsh material but differs in having a greater number of pits in Ej, in having Ei and Ij more extensively silicate frontally and in its characteristic swollen genal lobes. Another specimen which may belong here comes from King’s Eocality §6 (1923, fig. 4) about 1 km south-west of Craig Fawr and from stratigraphically slightly higher than the other material. This specimen (PI. 103, fig. 8) is similar in most features but differs in showing 12 pits in the E2 arc and 7 pairs of apodemal pits on the pygidial axis. There are 10 pits in the posterior row. It may be noted that the number of apodemal pits on the pygidial axis in this specimen exceeds the maximum of 6 stated by Ingham (1970, p. 41) to be characteristic for the T. seticornis group. Tretaspis cf. sortita (Reed, 1935) Plate 103, figs. 1-7; text-fig. 2 1928 Trinucleiis seticornis Hisinger; King (pars), list, p. 699 (top). ?1968 Tretaspis kiaeril\ Whittington, p. 92, list, p. 123, pi. 29, figs. 3, 5. Type material. A lectotype has yet to be selected from the syntypes figured by Reed (1935, pi. 1, figs, 4-10) from the Starfish Bed of the Upper Drummuck Group, Girvan, Scotland. Material, horizon, and locality. Fifteen specimens from the highest Ashgill Mudstones of Craig-wen Quarry, 120 m west of Craig-wen-fach Farm, 7 km south-west of Meifod (Locality 59 of King 1928). The specimens are all from phosphatic nodules and so retain the original convexity and many have the exoskeleton preserved. Description. Cephalon sub-semicircular in dorsal outline. Pseudofrontal lobe occupying three-fifths of glabellar length (sag.) ; sub-circular in dorsal view, strongly convex (tr. and sag.) but not overhanging fringe anteriorly; apically bearing small median tubercle. Occipital ring convex (tr.), orientated slightly dorsally and strongly posteriorly so that the mesial section is broad (sag. and exsag.) in dorsal view, rather flat and not sharply separated from the occipital furrow, the posterior margin convex. Occipital furrow broad and shallow, transverse, abaxially containing deep, ovoid apodemal slots. Ip lateral glabellar lobes short (tr.), convex, strongly rounded abaxially. Ip and 2p lateral furrows deep and prominent, the former slot-like, diverging posteriorly at about 95°, the latter large ovoid pits diverging anteriorly at 1 1 0- 1 20°. Between them the 2p lateral lobes broaden (exsag.) abaxially. There may be very faint traces of the 3p lateral furrows on some specimens but they are never clearly developed. Glabella separated from genal lobes by broad (tr.) axial furrows which in dorsal view are slightly divergent anteriorly and abaxially convex. Anterior fossulae small, rather far back from arc of fringe. Genal lobes sub-quadrant shaped, convex (tr. and exsag.) but not overhanging fringe; bearing prominent lateral tubercles on the level of the anterior margins of the 2p lateral furrows; dropping steeply posteriorly to broad (exsag.), transverse posterior border furrows which abaxially contain large posterior fossulae. Posterior borders narrow (exsag.) over transverse adaxial section, broadening rapidly towards the posterior fossulae where they are deflected posteriorly. External moulds and specimens retaining the exoskeleton show the pseudofrontal lobe of the glabella to be finely reticulated in a manner very similar to that seen in a specimen of T. 1. latilimbus figured by Ingham (1970, text-fig. ISQ. This reticulation is terminated posteriorly in a narrow (sag. and exsag.), anteriorly convex ridge joining the posterior parts of the 1 p lateral glabellar furrows. The genal lobes are smooth. The posterior margins of the posterior borders bear fine, sub-parallel terrace lines. Fringe anteriorly comprises steep, gently convex genal roll; the narrow (tr.), very slightly curled brim is developed only laterally. Anteriorly 6 pit-arcs are present in the fringe : El, Ii_4, and I„. The pits of Ej and Ii, which are out of line with the Ij-Ip pits, in 1 or 2 specimens share short radial sulci but in most remain clearly separate (PI. 103, figs. 1,6). Available material shows 183 or 19 pits in E,. E2 is only developed laterally from between bR7 and bRlO outwards and is absent from the posterior row so that between 9 and 12 pits are present. Arcs Ej, Ii_3, and E are complete. Arc I4 merges with laterally between aRl 1 and aRI4. In all but 1 of 7 specimens PRICE: TRETASPIS FROM THE ASHGILL OF WALES 785 showing the appropriate region of the fringe, a short I5 arc is developed of between 1 and 4 pits, extending between aR3 and aR6 and absent frontally for between 24 and 44 radii. There are between 8 and 1 1 pits in the posterior row. On the upper lamella of the fringe lists may be developed between the internal pit- arcs and, laterally, between Ii and Ej. Internal moulds show that on the lower lamella the I2-In phs are associated in radial sulci which, as in other forms, break down on the genal prolongations. Girder broad, deep anteriorly but shallow laterally, ornamented with moderately strong, widely spaced sub-parallel terrace lines. Thorax of six segments. Axis occupying slightly less than one-third total width (tr.) anteriorly; only moderately convex (tr. ). Axial rings strongly convex (sag. and exsag.) mesially, becoming flatter and broaden- ing (exsag.) outwards to form sub-quadrilateral axial lobes; separated by broad (sag. and exsag.) ring furrows from lower, less strongly convex half-rings. Axial furrows shallow. Pleurae straight and flat for almost three-quarters of length (tr. ) then deflected ventrally and strongly posteriorly with strongly truncated, rounded antero-lateral corners. Pleural furrows commencing at inner anterior corners where they are narrow and broadening rapidly as they run outwards and back separating narrow anterior pleural bands from broader posterior bands. Anterior margins of latter raised and forming prominent oblique ridges. Pygidium slightly less than three times as wide (tr.) as long (sag.), with convex postero-lateral margins and strongly bevelled from a narrow sub-marginal rim. Axis occupying rather over one-quarter of total width (tr.) anteriorly, tapering back at about 35° and bearing six pairs of slot-like apodemal pits within the mesially shallow ring-furrows. Pleural lobes almost flat and horizontal, crossed on available material by at least two poorly defined ribs. Bevelled margin ornamented with fine, closely spaced, sub-parallel terrace lines. Discussion. In terms of fringe characters the form described above relates to T. sortita (Reed) as briefly characterized by Ingham (1970, p. 50, pi. 8, fig. 1). The specimen illustrated by Ingham has four pits in I5 and as far as can be judged the numbers of pits in other arcs are similar to those for the Welsh material. Dr. Ingham too com- ments (pers. comm.) that the fringe characters of the Welsh specimens appear to fall within the range of variation of T. sortita from the Upper Drummuck Group and that there is a close similarity in general morphology. More detailed comparison is pre- cluded until T. sortita itself is redescribed. Ingham has also noted (1970, p. 43) the occurrence of a form apparently similar to T. sortita in the Ddolhir Beds of the Cynwydd area of the Northern Berwyns in Wales. A specimen figured by Whittington (1968, pi. 29, figs. 3, 5) as T. kiaeril has 19 pits in Ej, a laterally incomplete I4 arc, 2 or 3 pits in I5, 13 pits in E2, and 9 in the posterior row. Five other specimens from the same general area (BM I 1308) are poorly preserved but give the following pit-counts: 18, 194 (1 specimen in each case), or 20 (2 specimens) pits in Ei, 7, 12, or 14 pits in E2 (1 specimen in each case) and, in 1 specimen, 4 or 5 pits in I5. As will be seen from the specimen figured by Whittington, the over-all morphology is very similar to that of the Meifod specimens described here. Close comparison, however, must await better-preserved material. The Cynwydd area specimens in the BM collections are poorly localized (see Whittington 1968, p. 123) and their position within the Ddolhir Beds uncertain. TRETASPIS OF UNCERTAIN AFFINITY Tretaspis sp. indet. B Plate 103, fig. 14 1909 Trinucleiis seticornis (His.); Strahan et at., faunal list, p. 59. Material, horizon, and locality. GSM Pr. 161, 162, counterpart moulds of almost complete articulated exoskeleton; Pr. 130, poorly preserved internal mould of incomplete exoskeleton, both from a low horizon 786 PALAEONTOLOGY, VOLUME 20 in the Slade and Redhill Mudstone Formation at Lower Cresswell Farm, about 3-75 km south-east of Llandowror, Dyfed. Three other specimens from the same locality, a poor pygidium (Pr. 170) and two fringe fragments (Pr. 163, 165), probably also belong with this species. Description. Cephalon approximately semicircular in outline with a sub-spherical pseudofrontal glabellar lobe and strongly convex (tr. and exsag.) genal lobes, sub-quadrant shaped and not overhanging the fringe. Both glabella and genal lobes are coarsely reticulated and this reticulation is strong enough to be discernible, faintly, even on internal moulds. The available fringes are incomplete and poorly preserved so that the over-all pit distribution is not clear. The half-fringe has about twenty-one pits in the Ej arc. An Ej arc is developed and the pits in this are clearly separate from the Ej pits except in the anterior-most radius (Rl) where they become conjunct. Pits of the Ii arc are radially in line with the two E pits and these three pits are contained together in radial sulci on the upper lamella. On the lower lamella the pits of the remaining internal arcs are associated in radial sulci and these are seen to be out of line with the radii containing the E2, E], and Ij pits. The number of internal arcs in addition to the arc is uncertain but in front of the axial furrows there appear to be at least two more (I3, I„, ?). There are at least seven pits in the posterior row. The girder is broad and deep frontally, shallower laterally. The genal prolongations are relatively short and there are long, slender genal spines with dorsal grooves. Thorax of six segments. Axis broad (tr.), gently convex, with broad (sag. and exsag.), mesially shallow articulating furrows containing deep, ovoid apodemal slots abaxially. Pleurae broad (exsag.), horizontal for most of length, deflected ventrally and slightly posterior at distal extremities. Pygidium about two and a half times as broad (tr.) as long (sag.), with strongly rounded postero-lateral margins. Axis occupies about one-quarter of total width (tr.) anteriorly and tapers back at about 25°. Mesially shallow ring furrows contain deep apodemal slots near the abaxial ends; six such pairs of slots are clearly visible and a seventh may be faintly developed. Axial furrows shallow. Pleurae flat, crossed by four oblique, abaxially broadening, faintly defined ribs. A sub-marginal rim is developed and the posterior margin is strongly bevelled. Discussion. Whilst the out-of-line arrangement of the Ei_2. Ii. and the I2-In pits in aR and bR radii in this species is characteristic of the T. seticornis species group of Ingham (1970, p. 41), the significance of the virtually complete E2 arc is uncertain. Species within the T. seticornis group are characterized by an E2 arc which is only developed laterally while the known species in which the E2 arc is continuous frontally have been placed (with the exception of T. persulcatus Reed, 1935) in the T. moeldenensis group (Hughes et al. 1975, pp. 563-564). The typical form of the E2 arc in the species described here can only be ascertained when more material is available. While such information as this and the number and degree of completeness of the inner I arcs is lacking, comparisons are difficult. Dr. Ingham (pers. comm.) has, however, drawn attention to the similarity of the form described here to a form, as yet unnamed, from the Lower Drummuck group of the Girvan area. This latter species, which appears to be a precursor of T. persul- catus Reed, is characterized by an E2 pit-arc which is incomplete frontally and also lacks the external pseudogirder which is developed in T. persulcatus itself (Hughes, et al. 1975, p. 564). Tretaspis cf. calcar ia Dean, 1971 Plate 103, figs. 9-13 1966 Tretaspis kiaeri Stormer; Whittington (pars), pi. 28, figs. 1, 6-14; non pi. 29. Holotype. Eigured by Dean 1971, pi. 4, fig. 1, BM It. 8135, a cephalon from the Chair of Kildare Limestone of Eastern Ireland. Remarks. Neither T. kiaeri nor the allied T. calcaria fit readily into one or other of PRICE: TRETASPIS FROM THE ASHGILL OF WALES 787 Ingham’s two species groups. Whilst the fringe is made up of aR and bR radii out of line, the E2 pit-arc is continuous frontally and, moreover, the arrangement of pits is very similar to that seen in such forms as T. moeklenensis and T. cf. radialis belonging to the T. moeldenensis species group. It is possible to emphasize these similarities and to consider, as Dean has done (1971, p. 16), that the affinities of T. Ar/ncr/and T. calcaria are with these members of the T. moeldenensis group and that the significance of the out-of-line arrangement of pits in aR and bR radii is not, in this case, very great. On the other hand, the development of the E2 arc in members of the T. seticornis group is very variable. It is tempting, to the present author at least, to consider the form described above as Tretaspis sp. indet. B as a member of the T. setieornis group in which E2 has become almost complete frontally. It is then possible to regard T. kiaeri and allied forms more reasonably as members of the T. seticornis group in which E2 is frontally complete. Material, horizon, and localities. Available material totals some twenty-nine specimens in various col- lections (BM, BU, NMW, and SM). Most of these are distorted and/or fragmentary and sample numbers for pit-counts are extremely small. The material is from various localities in the Rhiwlas Limestone (Rawtheyan) of the Bala area, North Wales. Description. Whittington’s recent treatment (1966, see synonomy) of this form renders extensive illustration unnecessary. Pseudofrontal lobe of glabella strongly inflated, sub-parabolic in anterior view, standing high above level of genae; in lateral view dropping very steeply anteriorly. Neither pseudofrontal lobe nor genal lobes overhang fringe. Surface of both genal lobes and glabella as far back as Ip latera lobes finely reti- culated (PI. 103, fig. 12). Genal roll steep and gently convex anteriorly, brim rather narrow (sag. and exsag.), only becoming well-developed laterally. In front of the axial furrows the 8 pit-arcs Ei_2, fi-s, and are developed. Ij is absent for H ( 1 specimen), 2 (2 specimens), or 3 radii (1 specimen) frontally but is developed from aR2-4 to approximately aR18 (estimate on 1 specimen). In all specimens examined the I5 and pits do not share radial sulci but are clearly separate over the region in which the former arc is developed (PI. 103, figs. 9, 11). Arcs E-fi and E are complete laterally. On the upper lamella pits of the Ei_2 and E arcs are contained in bR radii which are out of line with the E^E Phs in aR radii. E is contained in radial sulci with Ei and Ej to around bR15 or 16 outwards from which the sulci contain the E pits only except in the posterior row where there is a single Ei pit. This posterior row contains 11(1 specimen) or 12 pits (3 specimens). The number of pits in Ej varies from ?26 to 28 or 29 (1 specimen in each case). On available internal moulds the girder is ornamented with only very weakly developed sub-parallel terrace- lines. Pygidium sub-triangular, with postero-lateral margins strongly convex; rather over two and a half times as wide (tr.) as long (sag.). Axis occupies rather over one-quarter of total width (tr.) anteriorly, is moderately convex (tr.), and tapers back at about 30° bearing seven pairs of apodemal pits. Pleurae crossed by at least three faint ribs. There is a low sub-marginal rim. Discussion. Though the fragmentary and distorted nature of much of the Rhiwlas material renders comparison difficult, there appears to be close similarity in many features to the specimens of T. calcaria described by Dean (1971, pp. 12-16, pi. 4, figs. 1-8, 10, 11; pi. 5, fig. 6) from the Chair of Kildare Eimestone. One difference is that in the Rhiwlas specimens I5 is developed as a clearly separate arc whereas in the Chair of Kildare specimens I5 and I„ pits are closely associated in short sulci. I5 may be slightly more extensive laterally in the Welsh material. Otherwise differences in pit distribution between the two forms are slight, the Irish material possibly having a slightly higher peripheral pit-count. Irish material also appears to lack the well- developed lists seen in the Welsh specimens. 788 PALAEONTOLOGY, VOLUME 20 T. kiaeri Stormer (1930, p. 50, pi. 10, figs. 1-6; pi. 1 1, fig. 12; pi. 13, fig. 3; pi. 14, figs. 1-3; text-figs. 22-26; 1945, pp. 403, 406, pi. 1, figs. 11, 12) from the highest beds of the Upper Chasmops Limestone (in the lithological sense^the ‘4bS2 sub-zone’ of Stormer 1945) on Frogno, Ringerike, and the lower part of the Gagnum Shale of Hadeland, differs from both the type material of T. calcaria and the Welsh specimens described above in the respects noted by Dean (1971, p. 14). LIST OF OCCURRENCES Tretaspis moeldenensis Cave (s.l.). Bodeidda Mudstone Eormation; quarry 14 m west of Bodeidda, 2| km south-west of Conway, Gwynedd (Population A). Basal Tre-wylan Beds exposed around waterfa 1 in dingle 370 m north-west of Glan-yr-afon Farm, 4 km north of Llansantffraid-ym-Mechain, Powys (= Locality 42 of Whittington, 1938 = Locality 3 of Wedd et al. 1929, list, p. 62) (Population B). Basal Ty’n-y-twmpath Beds in headwaters of Nant-y-Lladron, 5 km south-south-east of Corwen, Clwyd (= Locality 47 of Wedd et al. 1927, p. 41) (Population C). Basal Ashgill Mudstones in stream section south of quarry at Pen-y- garnedd, 20 km north-west of Welshpool, Powys (= Locality 1 of Wedd et al. 1929, p. 61). Tretaspis moeldenensis moeldenensis C‘d\Q. Thin, basal horizon of Sholeshook Limestone Formation around Llandowror, 3 km south-west of St. Clears, Dyfed (Localities 17, 24a, and 25 of Price 1973a, last = type locality). ITretaspis moeldenensis moeldenensis. About 40 m above base of Ty’n-y-twmpath Beds in headwaters of Nant-y-Lladron, 5 km south-east of Corwen, Clwyd ( = Locality 36 of Wedd et al. 1927, p. 41). Basal Ashgill Mudstones, stream section in Cwm Nant-y-meichiaid at Glyn Cottage, 3 km north-west of Meifod, Powys ( = Locality 29 of King, 1928). Tretaspis cf. radialis Lamont— Ranges throughout all but topmost 4 m of Sholeshook Limestone Forma- tion of Sholeshook and Prendergast, Haverfordwest, Dyfed, while around Llandowror it is absent from the base of the formation ( Localities 1 7, 24a, 25) and not known with certainty above Locality 1 8a of Price, 1973a, Lower Tre-wylan Beds; quarry at Ty-isaf-mawr, 1 -75 km north-east of Llansantffraid-ym-Mechain, Powys (= Locality 53 of Whittington, 1938). Tretaspis aff. radialis Lamont. Topmost 4 m of Sholeshook Limestone Formation and overlying Slade and Redhill Mudstone Formation at Prendergast Place, Haverfordwest, Dyfed (Localities 8c-8a of Price 1973) and latter formation at Redhill Quarry, 2-5 km north-west of Havei fordwest (Locality 7). Basal Ashgill EXPLANATION OF PLATE 103 Figs. 1-7. Tretaspis cf. sortita (Reed), topmost Ashgill of Craig-wen Quarry, south-west of Meifod. 1-3, SM A 14390, internal mould of undistorted cephalon, anterior, left-lateral, and dorsal views, x6. 4, SM A14389, internal mould of articulated exoskeleton, dorsal view, x4. 5, SM A14395a, pygidium and posterior part of thorax, part of enrolled specimen retaining exoskeleton, pygidium in dorsal view, x5. 6, SM A14393a, internal mould of cephalon, antero-lateral view, x 6. 7, SM A14392, internal mould of right genal area of fringe, dorso-lateral view, x 5. Fig. 8. ITretaspis cf. latilimbus (Linnarsson) distichns Ingham, SM A39889a, internal mould of articulated exoskeleton. Locality S6 of King 1923, head of first tributary on south side of Marchnant valley, south- west Berwyns, dorsal view, x 4. Figs. 9-13. Tretaspis cf. calcaria Dean, Rhiwlas Limestone, Bala area. 9, SM A41329, partial internal mould of cephalon, anterior view, x 5. 10, NMW.27.1 10.G541, cephalon partially retaining exoskeleton, anterior view, x4. 1 1, NMW. 56. 316. G9, partial internal mould of cephalon, antero-lateral view, x6. 12, SM A41330, partial cephalon partly retaining reticulated exoskeleton, dorsal view, x 5. 13, SM A85521, internal mould of pygidium, dorsal view, x 5. Fig. 14. Tretaspis sp. indet. B, GSM Pr. 162, articulated specimen partly retaining exoskeleton, Slade and Redhill Mudstone Formation, Lower Cresswell Farm, south-east of Llandowror, dorsal view, x4. PLATE 103 8 PRICE, Tetraspis from Wales 790 PALAEONTOLOGY, VOLUME 20 Mudstones, stream section east-north-east of Aber-marchnant Farm, 2 km east of south end of Lake Vyrnwy, Powys (Locality al of King 1923). Tretaspis sp. indet. A. Birdshill Limestone; old quarry 180 m north-west of Birdshill Farm, 2-5 km north- west of Llandeilo, Dyfed. Tretaspis hadelandica Stormer, brachystichus Ingham. Highest Sholeshook Limestone Formation and base of succeeding Slade and Redhill Mudstone Formation at Sholeshook and Prendergast, Haverfordwest, and around Llandowror (Localities 8a, 8b, 9d, 15, and 22 of Price 1973a); Sholeshook Limestone horizon at Robeston Wathen (Locality 10a); high Slade and Redhill Mudstones on west bank of Western Cleddau, Haverfordwest (Locality I of Cocks and Price 1975). Crugan Mudstone Formation; exposure at Berllan Cottage, 1-8 km north of Llanbedrog, Lleyn Peninsula. Lower Tre-wylan Beds; exposure by track 450 m north of crossroads at Cefn-y-blodwell, 1-5 km north-north-west of Llanyblodwell, Powys ( = Locality 54 of Whittington 1938). Upper Tre-wylan Beds; exposure 45 m north-north-west of Gelli Farm, 1-75 km south-east of Llansantffraid-ym-Mechain, Powys (= Locality 61 of Whittington 1938). Basal Ashgill Mudstones, stream section east-north-east of Aber-marchnant Farm, 2 km east of south end of Lake Vyrnwy, Powys (Locality al of King 1923). Tretaspis cf. latilimhus (Linnarsson) distichus Ingham. Higher part of 'Calyinene quadrata Mudstones’ on Craig-Fawr, 3 km south-east of Hirnant, Powys (= Locality A8 of King 1923, hg. 3). ITretaspis cf. latilimbus (Linnarsson) distichus Ingham. 'Trinucleus bucklandi Mudstone’ of King 1923, exposed near head of first tributary on south side of Marchnant valley, 2-6 km south-south-east of Hirnant, Powys ( = Locality S6 of King 1923, fig. 4). Tretaspis cf. sortita (Reed). From phosphatic nodules in mudstones immediately beneath the Craig-wen Sandstone in Craig-wen Quarry, 120 m west of Craig-wen-fach Farm, 7 km south-west of Meifod, Powys (= Locality 59 of King 1928). ITretaspis cf. sortita (Reed). Ddolhir Beds of area around Cynwydd, 3-5 km south-west of Corwen, Clwyd (exact horizons and localities uncertain). Tretaspis sp. indet. B. Low horizon in Slade and Redhill Mudstone Formation ; exposure at Lower Cresswell Farm, about 3-75 km south-east of Llandowror, Dyfed. Tretaspis cf. calcaria Dean. Rhiwlas Limestone Member of Moelfryn Mudstone Formation; various localities around Bala, Gwynedd (for details see Whittington 1966, p. 90). Acknowledgements. This work commenced during a N.E.R.C. Research Studentship in the Department of Geology, University College, London. Further collecting was undertaken from the Department of Geology, University College of Wales, Aberystwyth and, with the aid of grants from the F. R. Cowper-Reed Fund, from the Sedgwick Museum, Cambridge. I thank the following for the loan of museum material: Dr. R. A. Fortey and Mr. S. F. Morris (BM), Dr. J. K. Ingham (HM), Dr. R. M. Owens (NMW), Dr. A. W. A. Rushton (GSM), and Dr. I. Strachan (BU). I also thank Dr. Ingham for much useful discussion and advice and for kindly reading the manuscript. REFERENCES BASSLER, R. s. 1915. Bibliographic index of American Ordovician and Silurian fossils. Bull. U.S. natn. Mus. 92, 1-1521. CAVE, R. 1960. A new species of Tretaspis from South Wales. Geol. Mag. 97, 334-337, pi. 10. 1965. The Nod Glas sediments of Caradoc age in North Wales. Geol. J. 4, 279-298. COCKS, L. R. M. and price, d. 1975. The biostratigraphy of the upper Ordovician and lower Silurian of south-west Dyfed, with comments on the Hirnantia fauna. Palaeontology, 18, 703-724, pis. 81-84. DEAN, w. T. 1961. Trinucleid trilobites from the Higher Dufton Shales of the Caradoc Series in the Cross Fell Inlier. Proc. Yorks, geol. Soc. 33, 1 19-134, pis. 7-9. PRICE: TRETASPIS FROM THE ASHGILL OF WALES 791 DEAN, w. T. 1962. The trilobites of the Caradoc Series in the Cross Fell inlier of northern England. Bull. Br. Mus. nat. Hist. (Geol.), 7, (3), 65-134, pis. 6-18. 1971. The trilobites of the Chair of Kildare Limestone (Upper Ordovician) of eastern Ireland. Palaeontogr. Soc. [Monogr.], 1-60, pis. 1-25. ELLES, G. 1909. The relation of the Ordovician and Silurian rocks of Conway (North Wales). Q. Jl geol. Soc. Loud. 65, 169-194. HAWLE, I. and CORDA, A. j. c. 1847. Prodrom einer Monographic der Bohemischen Trilobiten. Prague. HisiNGER, w. 1840. Lethaea Svecica sen Petrificata Sveciae, iconihus et characterihus illustrata. Suppl. secundum. Holmiae. HUGHES, c. p., INGHAM, J. K. and ADDISON, R. 1975. The morphology, classification and evolution of the Trinuclidae (Trilobita). Phil. Trans. R. Soc. bond. B272, 537-604, pis. 1-10. INGHAM, J. K. 1966. The Ordovician rocks in the Cautley and Dent districts of Westmorland and Yorkshire. Proc. Yorks, geol. Soc. 35, 455-505. 1970. A monograph of the Upper Ordovician trilobites from the Cautley and Dent districts of Westmor- land and Yorkshire. Palaeontogr. Soc. [Monogr.], 1-58, pis. 1-9. KING, w. B. R. 1923. The Upper Ordovician rocks of the south-western Berwyn Hills. Q. Jl geol. Soc. bond. 79, 487-507. 1928. The geology of the district around Meifod (Montgomeryshire). Ibid. 84, 671-702. LAMONT, A. 1941. Trinucleidae in Eire. Ann. Mag. nat. Hist. (1 1), 8, 438-469, pi. 5. 1945. Tretaspis in the north of England. Quarry Mgrs' J. 29, 122-123, pi. 1. LiNNARSSON, J. G. o. 1869. Om Vestergbtlands Cambriska och Siluriska Aflagringar. K. svenska Vetensk- Akad. Handl. 8 (2), 1-89, pis. 1, 2. MARR, J. E. and ROBERTS, T. 1885. The Lower Palaeozoic rocks of the neighbourhood of Haverfordwest. Q. Jl geol. Soc. bond. 41, 476-491. m’coy, f. 1849. On the classification of some British fossil Crustacea, with notices of new forms in the University Collection at Cambridge. Ann. Mag. nat. Hist. (2), 4, 161-169, 330-335, 392-414. PRICE, D. 1973a. The age and stratigraphy of the Sholeshook Limestone of South-West Wales. Geol. J. 8, 225-246. 1973h. The Phillipsinella parabola-Staurocephalus clavifrons fauna and Upper Ordovician correlation. Geo/. Mag. no, 535-541. 1974. Trilobites from the Sholeshook Limestone (Ashgill) of South Wales. Palaeontology, 17, 841- 868, pis. 112-116. REED, F. R. c. 1912. Sedgwick Museum Notes. Notes on the genus Trinucleus. Parts I and II. Geol. Mag. 49, 346-353, 385-394. 1914. Sedgwick Museum Notes. Notes on the genus Trinucleus III. Ibid. 51, 394-395. 1935. The Lower Palaeozoic trilobites of Girvan. Supplement No. 3. Palaeontogr. Soc. [Monogr.], 1-64, pis. 1-4. STORMER, L. 1930. Scandinavian Trinucliidae with special reference to Norwegian species and varieties. Skr. Norsk Vidensk.-Akad. Mat. Naturv. Kl. 4, 1-111, pis. 1-14. 1945. Remarks on the Tretaspis (Trinucleus) Shales of Hadeland with description of trilobite faunas. Norsk geol. Tidsskr. 25, 379-426, pis. 1 -4. STRAHAN, A., CANTRiLL, T. c., DIXON, E. E. L. and THOMAS, H. H. 1909. The geology of the South Wales Coal- field. Part X. The country around Carmarthen. (Sheet 229.) Mem. geol. Surv. U.K. i-viii, 1-177. and JONES, o. t. 1914. The geology of the South Wales Coalfield. Part XI. The country around Haverfordwest. (Sheet 228.) Ibid, i-viii, 1-262. WAHLENBERG, G. 1818. Petrificata Telluris Svecanae Uppsaliae. Nova- Acta R. Soc. Sclent, upsal. 8, 1-293. WEDD, c. B., SMITH, B., KING, w. B. R. and WRAY, D. A. 1929. The geology of the country around Oswestry. (Sheet 137.) Mem. geol. Surv. U.K. i-xix, 1-234. and WILLS, l. j. 1927. The geology of the country around Wrexham, Part I. Lower Palaeozoic and Lower Carboniferous rocks. (Sheet 121.) Ibid, i-xviii, 1-179. WHITTINGTON, H. B. 1938. The geology of the district around Llansantffraid-ym-Mechain, Montgomery- shire. Q. Jl geol. Soc. bond. 94, 423-457, pis. 38, 39. 1941. The Trinucleidae^with special reference to North American genera and species. J. Paleont. 15,21-41, pis. 5, 6. 792 PALAEONTOLOGY, VOLUME 20 WHITTINGTON, H. B. 1966. A monograph of the Ordovician trilobites of the Bala area, Merioneth. Palaeontogr. Soc. [Motwgr.], 63-92, pis. 19-28. 1968. A monograph of the Ordovician trilobites of the Bala area, Merioneth. Ibid. 93-138, pis. 29-32. WILLS, L. j. and smith, b. 1922. The Lower Palaeozoic rocks of the Llangollen district with special reference to the tectonics. Q. Jl geol. Soc. Land. 78, 176-226. Original typescript received 20 April 1976 Revised typescript received 3 November 1976 DAVID PRICE Department of Geology Sedgwick Museum Downing Street Cambridge CB2 3EQ THE MICROMORPH ALBIAN AMMONITE FALLOTICERAS PARONA AND BONARELLI by W. J. KENNEDY and M. R. COOPER Abstract. Falloticeras Parona and Bonarelli, 1897 (type species: Ammonites proteiis d'Orhigny, 1842) is a diminutive Cretaceous (Middle Albian, dentatus Zone) member of the acanthoceratacean subfamily Mojsisovicsiinae, individuals of which are generally adult at less than 35 mm diameter. The genus is considered to be a micromorph, perhaps a neotenous offshoot of Mojsisovicsia Steinmann, 1881, rather than simply a microconch of that genus. This is suggested by differences in ontogenetic development, relative abundance, and stratigraphic distribution. The type specimens are illustrated photographically for the first time, a lectotype designated, and the range of variation discussed. The genus Falloticeras Parona and Bonarelli (Acanthocerataceae) is a rare dwarf ammonite known originally from condensed sediments in the Alpes Maritimes, France, and subsequently recorded from the spat hi subzone of the dentatus Zone in the Anglo-Paris Basin ; both of which lie in the area of the hoplitinid or European faunal province. Besides redescribing and analysing populations from France, we record for the first time the presence of this genus in strata of equivalent ages in Zululand and Peru, areas well outside the hoplitinid province. Its rarity is not, therefore, due to faunal provincialism. The present study indicates that Falloticeras is best considered a neotenous offshoot, adult at 25-35 mm diameter, of Mojsisovicsia Steinmann, 1881, which is adult (in the type species at least) at diameters in excess of 100 mm, rather than a sexual dimorph. D’Orbigny’s type material is redescribed and figured for the first time, together with abundant topotype material, in an attempt to illustrate the range of variation within this monospecific genus. SYSTEMATIC DESCRIPTION Suborder ammonitina Hyatt, 1889 Superfamily acanthocerataceae Hyatt, 1900 Family brancoceratidae Spath, 1933 Subfamily mojsisovicsiinae Hyatt, 1903 Genus falloticeras Parona and Bonarelli, 1897 Tvpe species. Ammonites proteus d'Orhigny, 1842, p. 624, by the original designation of Parona and Bonarelli 1897, p. 89. Diagnosis. Shell small, moderately involute, with a subquadrate, generally depressed whorl section. Early whorls with simple, broad, prorsiradiate ribs, projected on the venter to meet a fine siphonal keel at an acute angle. Ornament declines in maturity and the last half of the body chamber is commonly smooth. Con- strictions variably developed. Sutures simple, with rather broad, slightly divided elements. [Palaeontology, Vol. 20, Part 4, 1977, pp. 793-804, pis. 104-105.] 794 PALAEONTOLOGY, VOLUME 20 Measurements. diameter; Wb = whorl breadth; Wh = whorl height; U == umbilical diameter. All measurements are in millimetres; figures in parentheses are dimensions as a percentage of total diameter. D Wb Wh Wb/Wh U *BMNH C68140 29 9(31) 8-5(29) 1-06 9(31) BMNH C68140 21 7(33) 8(38) 0-88 7(33) BMNH C68140 14-5 6(41) 6(41) 1-00 5(34) BMNH C68145 25 9(36) 12(48) 0-75 10(40) BMNH C68145 22 7(32) 11(50) 0-64 6-5(30) MNHP 5766a 25 9(36) c. 12(48) 0-75 c. 9(36) MNHP 5766d c. 24 8(33) 9(38) 0-89 c. 8(33) BMNH C68141 22 7(32) 12-5(57) 0-56 8-5(39) BMNH C68141 18-5 6(32) 11(59) 0-56 6-5(35) MNHP 5766c 22 8(36) 10(45) 0-80 7(32) BMNH C68142 20-5 7(34) 9(44) 0-78 7-5(37) BMNH C68142 15-5 5(32) 8(52) 0-63 5(32) BMNH C68146 20 9(45) 10(50) 0-90 7(35) BMNH C68146 14 4-5(32) c. 8(57) 0-56 c. 4-5 (32) BMNH C68143 20 7(35) 11(55) 0-64 7(35) BMNH C68143 15 5(33) 8(53) 0-63 5-5(37) MNHP 5766b 19 7(37) 8(42) 0-88 7(37) MNHP 5766b 15 5(33) 7(47) 0-71 5(33) MNHP 5766e c. 18 7(39) 10(56) 0-70 — BMNH C2298 17 6-5(38) 8(47) 0-81 6(35) MNHP 5766f 14 5-5(39) 6-5(46) 0-85 4(29) BMNH C68144 10 3(30) 6(60) 0-50 3-5(35) BMNH C68144 c. 7-5 2-5(33) 5(66) 0-50 2(27) BMNH: British Museum (Natural History) Collections. MNHP: d’Orbigny Collection, Museum d’Histoire Naturelle, Paris, c. : approximately. * Lectotype. Discussion. Only the type species, F. proteus, has been referred to Falloticeras. The distinctive features are the small size, ribbed early but smooth adult whorls, con- strictions, and delicate but distinct keel, which is commonly lost on the body chamber. All other members of the Mojsisovicsiinae reach much larger sizes than Falloticeras. Mojsisovicsia are mature at diameters up to 100 mm (e.g. BMNH C78865); Oxytro- pidoceras and its subgenera are commonly adult at between 100 and 300 mm (Spath 1921 ; Collignon in Besairie 1936) ; Diplocerasare adult at 50-200 mm (e.g. Van Hoepen 1941). However, juvenile Mojsisovicsia show remarkable similarities to adult Fallo- ticeras 105, figs. \a-c,Aa-b, \2a-b, 13). They are smooth or faintly ribbed, and bear a distinct keel as does Falloticeras', contemporary species differ in showing a lack of strong ribbing on the earliest whorls (PI. 105, figs. 4a-b, 13) and developing, abruptly, the very strong adult ornament of strong ribs, flares, umbilical and ventro- lateral tubercles (PI. 1 05, figs. 2a-c, 1 3 ; text-fig. 2). Medium-sized and adult individuals (e.g. PI. 105, fig. 18) are unmistakably different. Oxytropidoeeras and its subgenera are usually oxycone, and may be strongly ribbed, tuberculate, or sometimes virtually smooth. We figure here two juveniles which show the smooth early stages (PI. 105, figs. Sa-c, 9a-c, text-fig. 2) as in Mojsiso- vicsia, and the change to ribbing characteristic of middle and later growth. Here again, the ontogenetic changes in ornament are the reverse of those seen in Falloticeras. Dipoloceras is equally distinctive (PI. 105, figs. 16, \la-e, 18, \9a-b'. KENNEDY AND COOPER: AMMONITE FALLOTICERAS 795 TEXT-FIG. 1. Sutures and whorl sections of Falloticeras proteus (d'Orbigny). a, JC 81 1-705C ; B, the lectotype, BMNH C68140; c, BMNH C2298. All x 12-5. d, MNHP 7566c; e, MCd; f, BMNH C6814; g, MCc; FI, MCe ; I, MCa ; J, MCb. All x 4 except h, which is x 6. 796 PALAEONTOLOGY, VOLUME 20 text-fig. 2). Evenly ribbed forms such as Dipoloceras bouchardiaimm (d’Orbigny) virtually lack ribs up to diameters of 3-4 mm (PI. 105, fig. Mb', text-fig. 2); beyond this, strong ribs are developed throughout ontogeny. In more typical members of the group, such as D. cf. pseudaon Spath (PI. 105, figs. 16, I9a-b) very strong, coarse ribbing also succeeds an initial smooth stage, here augmented by ribs which flare at the point of branching and are decorated by spiral, Elobiceras-like crenulations (PI. 105, fig. \9a). In all Dipoloceras, the keel is much stronger than in Falloticeras, and retained throughout ontogeny. Members of the Brancoceratinae such as Eubrancoceras Breistroffer, 1952, Brancoceras Steinmann, 1881, and Hysteroceras Hyatt, 1900, all lack the delicate keel and are strongly ribbed capricorns in middle and late growth stages. The morphologically closest member of this group is the subgenus Eubrancoceras {Para- brancoeeras) Breistroffer, 1952, which has constrictions on the inner whorls; the outer whorls are, however, distinctively capricorn. Occurrence. D’Orbigny’s remaining specimens of Ealloticeras are simply labelled ‘Clar’ (Alpes Maritimes). From the phosphatic preservation and sandy glauconitic matrix they clearly derive from one of the phosphatic sequences known in the Albian of this area, resembling closely the preservation of material from Escragnolles (Alpes Maritimes) before us. The species has been recorded independently from Escragnolles by Parona and Bonarelli (1897), Breistroffer (1947), and Collignon (1949) amongst others, and from Gourdon (Alpes Maritimes) by Collignon (1949). Both of these sequences are highly condensed, and the Ealloticeras cannot be precisely placed zonally in this region. In terms of English zonal and subzonal sequence proposed by Casey (1961) and Owen (1971), the faunas from Escragnolles (Collignon 1949) suggest horizons from the lowest Albian Leymeriella tardefurcata Zone to the Dipoloceras cristatum Zone of early late Albian age. At Gourdon, a broadly similar ammonite fauna occurs, and General M. Collignon tells us that it is his view that the Ealloticeras are confined to the Middle Albian Hoplites dentatus Zone. Ealloticeras has also been recorded from one horizon and locality in England, the spathi subzone of the dentatus Zone of the Gault Clay at Wrotham, Kent (Casey 1959; Milbourne 1963; Owen 1971). To these European occurrences, we can now add records from South America and South Africa. The first of these is based on a re- examination of the material from the Middle Albian of Saco near Oroya, Peru, described by Douglas (1921). Amongst previously unfigured material is what may be an undescribed Ealloticeras species (OUM KU 81 ; PI. 105, fig. \Aa-b). EXPLANATION OF PLATE 104 Figs, \a~c~\9a-c. Falloticeras proteus (d'Orh'igny). All specimens are phosphatic internal moulds, retaining traces of test, \a-c-6a-c, \%a-c-\9a-c are specimens in the d’Orbigny Collection, Museum d’Histoire Naturelle, Paris, and are from the Middle Albian of Clar, near Escragnolles, Alpes Maritimes, France. \a~c are MNHP 5766g; 2a-c are MNHP 5766a; 3a-b are MNHP 5766b; 4a-b are MNHP 5766e; 5a-c, 1 9a-c are MNHP 5766f ; 6a-e, 1 8a-c are MNHP 5766c ; la-b- 1 la-b are a variation series from the Middle Albian of Gourdon, Alpes Maritimes, France (M. Collignon Collection); \%a-c-\9a-c are hgured x 2, all the rest x 1 . r-f^ PLATE 104 3b 18a 18b 18c 19a 19b 19c KENNEDY and COOPER, Falloticeras from the Albian of France TEXT -FIG. 2. Comparative developmental stages of a, Mojsisovicsia sp. }uv., BMNH C68147, Middle Albian, Escragnolles; b, Falloticeras proteus (d’Orbigny), the lectotype BMNH C68140, Middle Albian, Escragnolles; c, Dipoloceras boiichardianum (d’Orbigny), BMNH C79611, cristatum Subzone, Wrotham, Kent; D, Oxytropidoceras sp. juv. BMNH 78785a; Albian ‘South of France’. All specimens are x2; sutures x 12-5. EXPLANATION OF PLATE 105 Fig. la-c. Mojsisovicsia sp. juv. BMNH C68147, Middle Albian, Escragnolles, Alpes Maritimes (Astier Collection). Figs, la-b, 5a-c, la-b. Falloticeras aff. proteus (d’Orbigny). BMNH C68145, C68143, and C68146. Middle Albian, Escragnolles, Alpes Maritimes (Astier Collection). Figs. 3fl-c, 6a-b. Falloticeras proteus {A'Oxh'igny). 3u-c the lectotype, BMNH C68140, a paralectotype, BMNH C68142, both in the Astier Collection, Middle Albian, Escragnolles, Alpes Maritimes. Figs. 4u-h, \la-b. Mojsisovicsia sp. juv. BMNH C78872 and C78865. Middle Albian, Mzinene Formation, Mzinene River, Zululand (South Africa). Figs. 8a-c, 9a-c. Oxytropidoceras sp. juv. BMNH 78783a-b, ‘South of France’ (Astier Collection). Fig. \0a-b. Falloticeras sp. BMNH C78873 and C78871, from the Middle Albian, Mzinene Formation, Mzinene River, Zululand (South Africa). Figs. 11, 13, 18. Mojsisovicsia ventanillensis (Gabb). OUM KU 88, 84, and 80, Middle Albian of Saco, near Oroya, Peru (J. A. Douglas Collection). Fig. 14u-h. Falloticeras sp. OUM KU 81, Middle Albian of Saco, near Oroya, Peru (J. A. Douglas Collection). Figs. 16, \9a-b. Dipoloceras cf. pseudaon (Spath). Van Hoepen Collection, South African Museum, Cape Town (figured x2) and BMNH C78882. Upper Albian, Mzinene Formation, Mzinene River, Zululand (South Africa). Fig. 17a-c. Dipoloceras bouchardianum (d’Orbigny). BMNH C7961 1, Upper Albian, Lower-Upper Gault Junction Bed, Division 6, ex cristatum subzone. Rugby Portland Cement Co. Pit, 450 yards North of Ford Place House, Wrotham, Kent (H. G. Owen Collection). All figures x 1, unless otherwise stated. PLATE 105 KENNEDY and COOPER, Albian ammonites 800 PALAEONTOLOGY, VOLUME 20 The second new record is from the Middle Albian of Zululand, South Africa, where collections from the lower part of the Mzinene Formation on the Mzinene (Umsinene of authors) River near Hluhluwe (Locality 51, bed 1 of Kennedy and Klinger 1975) have yielded a further series of Falloticeras (BMNH C78868, 78870- 78871, 78873; PI. 105, figs, \0a-b, \5a-b). The Zululand material occurs associated with Mojsisovicsia aff. ventanillensis (Gabb), Phylloceras (Hypophylloceras) velledae velledae (Michelin), Oxytropidoceras (Manuaniceras) mcmuanense (Spath), Pseud- helicoceras catenatum (d’Orbigny), and Puzosia sp. juv., again suggesting a Middle Albian age. Falloticeras pro tens (d’Orbigny) Plate 104; Plate 105, figs. 2, 3, 6, 7, 10, 15; text-figs. 1-3 1842 Ammonites proteus d’Orbigny, p. 624. 1850 Ammonites proteus d’Orbigny; d’Orbigny, p. 124. 1860 Ammonites proteus d’Orbigny; Pictet and Campiche, p. 306. 1897 Falloticeras proteum (d’Orbigny); Parona and Bonarelli, p. 89, pi. 12, fig. 1. 1922 Falloticeras . . .; Spath, p. 97. 1931 Falloticeras . . .; Spath, pp. 346, 352. 1938 Falloticeras proteum (d’Orbigny); Roman, p. 370, pi. 37, fig. 353a-b. (Copy of Parona and Bonarelli 1897.) 1942 Falloticeras . . .; Spath, p. 708. 1947 Falloticeras proteus d’Orbigny; Breistroffer, p. 30. 1949 Falloticeras proteus d’Orbigny; Collignon, p. 122. 1957 Falloticeras proteus (d’Orbigny); Wright in Arkell et ai, p. L404. 1959 Falloticeras cf. proteus (d’Orbigny); Casey, p. 207. 1963 Falloticeras proteus (d’Orbigny); Milbourne, Table 1. 1971 Ffl//o?/cerfls protcnm (d’Orbigny) ; Owen, p. 155. Type material. D’Orbigny introduced the name proteus in 1 842, stating that the species had been discovered by Astier in the ‘gault superieur’ of Clar, near Escragnolles. D’Orbigny’s collection (which was catalogued in 1858-1860, after his death in 1857) contains six specimens of Falloticeras under the catalogue number 5766. Associated with them is a label, apparently in d’Orbigny’s hand, as follows: Clar Gault am. Proteus avec interieur (Mouton) D’Orbigny’s collection contains many specimens in addition to those cited in his publications, including in some cases more than one specimen of species originally described on the basis of single specimens, and also specimens of manuscript species, whilst in other instances d’Orbigny returned specimens to other workers after describing and naming them. Astier’s collection was purchased (in 1853) by, and is now housed in, the British Museum (Natural History), and there are seven specimens which could be regarded as Falloticeras, BMNH C68140-68142, C681404-681406, and C2298. The d’Orbigny and Astier specimens all occur in a similar preservation. While it is, in our view, quite impossible to be certain whether all or any of these specimens were studies by d’Orbigny prior to publication of the name proteus in 1842, it is reasonable to regard the specimens in the Astier Collection as part of the syntype series, and we designate one of these, BMNH C68140 (PI. 105, fig. 3o-c; text-fig. 2b) as lectotype. Other specimens studied. Three topotypes, 81 l-705u-c in the Jaubert Collection, housed at the Universite Paris VI, also from Clar (Alpes Maritimes). Twenty-one specimens from the condensed Albian sequence of Gourdon (Alpes Maritimes), kindly loaned by General M. Collignon (MCa-k). Diagnosis. As for genus; see above. KENNEDY AND COOPER: AMMONITE FALLOTICERAS 801 Description. All specimens are phosphatic internal moulds; a few retain traces of phosphatized shell. Up to 15 mm diameter. Shell strongly inflated, involute, almost cadicone, the whorl breadth to height ratio varying between 0-5 and 0-85 (text-figs. 1, 3). Whorls reniform to subelliptical in cross-section, greatest breadth low on the flank. Umbilicus generally narrow, conical, with steeply inclined walls and an evenly rounded shoulder. Flanks strongly rounded, venter somewhat flattened with a narrow, delicate, continuous siphonal keel (PI. 104, fig. 6a, c; PI. 105, fig. 6a-b). Low, broad, simple ribs arise at the umbilical seam as mere striations, to strengthen across the umbilical shoulder and flank. They are commonly broader than the interspaces, rounded, concave, and markedly prorsiradiate (PI. 104, figs. 3b, 6b, 18c), being projected forwards across the ventrolateral shoulder and venter to meet the siphonal keel at an acute angle. There are between twenty-four and thirty ribs per whorl in the material before us. Weak to strong constrictions, parallel to the ribs, are present in some specimens (e.g. PI. 104, figs. 4a, 5a-b, 19a-c). 40 30 E 20 © *■ A AA AA^ : • • • • 20 30 Diameter (mm) ® Lectotype 40 1-10 1 00 0 90 0 80 _ 0 70 g 1 0 60 OBO 0 40 0-30 - 3 Gourdon Specimens * *.® \ A J • * , A A A • • • Aa * * AAA 20 30 Diameter (mm) ▲ Escragnolles/Var Specimens TEXT-FIG. 3. Graphical analysis of variation in Falloticeras proteus (d’Orbigny). 40 15-32 mm diameter. The shell becomes progressively more evolute (umbilicus up to 44% of diameter), degree of evolution increasing with size, the body chamber itself tending to uncoil in some individuals (e.g. PI. 104, figs, lb, 86, 13a, 166; PI. 105, figs. 36, 66) giving a scaphitoid coiling. The umbilicus becomes shallower, flanks flatten, the ventrolateral shoulder approaches the subangular, and the venter flattens (PI. 104, figs. 106, 14a) or tends to slight concavity. Ribbing generally declines, and disappears progressively between diameters of 7 and 1 5 mm. The siphonal keel persists on to the outer whorl (e.g. PI. 1 04, figs. 2a, 6c, 15a) but generally declines on the later parts of the body chamber (PI. 104, figs. Ic, 8a, 1 16; PI. 105, fig. 3a). The aperture of mature forms is preceded by a broad, shallow constriction (PI. 104, figs. 16,9a, 13o;Pl. 105, fig. 36), succeeded by a distinct flare (e.g. PI. 104, fig. 9a; PI. 105, fig. 36). The aperture is gently sinuous in lateral view, with a distinct ventral peak (PI. 104, fig. 156). Sutures (text-figs. 1,2). The sutures of mature Falloticeras are very simple, with broad, little incised elements. Intraspecific variation. Juveniles show a wide variation in strength of ribbing (compare PI. 104, figs. 36, 66, 18c, with PI. 104, figs. 5a-c; 19a-c;Pl. 105, fig. 15a-6) from near obsolete to strong. Inmost individuals, the strength of ornament declines between 7 and 15 mm, thereafter disappearing. A few specimens, e.g. MCf (PI. 104, fig. 11a), retain their ribs to over 20 mm. Constrictions are very variably developed; they are commonly absent in ribbed juveniles (PI. 104, figs. 6a-c, 18a-c) but may be conspicuous on feebly orna- mented ones (PI. 104, figs. 5a-c, 19a-c), a few specimens tentatively referred to this species retaining both 802 PALAEONTOLOGY, VOLUME 20 characteristics (PI. 105, figs. 2a~h, la-b). The keel is very variably developed; in some (Collignon’s 1949 var. nov.) it is retained to the mature aperture (PI. 104, fig. 15u-c), but in most it disappears. Exceptionally faint but distinctive spiral strigations are developed (PI. 105, fig. 3u-c). Over-all relative proportions vary greatly, as is clear from the table of dimensions, plots in text-fig. 3 and the variation series figured on Plate 104, with a continuum from robust specimens (PI. 104, fig. la-b) to slender (PI. 104, fig. llu-^?), and flat-sided (PI. 104, fig. \Qa-b) to round-whorled (PI. 104, fig. \6a-b) individuals. The whorl breadth-height ratio changes from relatively depressed to compressed throughout ontogeny; the variation in whorl breadth-height ratio being as follows (diameter and WbiWh) 14 mm, 0-53-1 00: 20 mm, 0-56-0-98; 30 mm, 0-74-0-92. There is also a tendency towards more evolute coiling as size increases, but again there is a range (diameter, umbilical width): 17 mm, 19-41%: 25 mm, 28-41%: 30 mm, 31-39%. There are a few specimens in the British Museum (Natural History) (Astier Collection), which we are unable to place in F. proteus with complete confidence; they include BMNH C68145 and C68146; both are far more strongly constricted than typical forms (PI. 105, figs. 2a-b, la-b) and have strong ribs associated with the constrictions which may develop umbilical bullae (PI. 105, fig. 2b). Both bear a delicate Falloticeras-Wk^t keel, and for the present we would identify them as F. aff. proteus; they may indicate, however, the presence of a second species at Escragnolles. Occurrence. As for genus (see above). Discussion. The only forms liable to be eonfused with F. proteus belong to other genera, and these are diseussed above under the aceount of the genus. Text-fig. 2 compares juveniles of all genera of Mojsisovicsinae; the closest form morphologically is Mojsisovicsia itself, most species of which can be distinguished by lack of ornament on early whorls, a stronger keel, and sudden acquisition of strong ribbing after a smooth or feebly ornamented stage as size increases, rather than the progressive loss of ornament seen in Falloticeras. A certain amount of confusion appears to surround the date of introduction of the name proteus', it is first used on p. 624 of Paleontologie Frangaise, Terrains Cretaces Cephalopodes, in a list of the cephalopods of the ‘gault superieur’, and diagnosed in a footnote as follows: ‘Cette Ammonite vient de Clar, pres d’Escragnolle (Var.). Elle y a ete decouverte par M. Astier. Elle est remarquable en ce qu’elle n’a des cotes, qu’etant jeune; plus tard, elle est entierement lisse et porvue d’une carene, comme les A. varicosus et Delaruei.' This is a perfectly acceptable indication, and the species thus dates from 1842, rather than 1840 or 1850 as indicated by some authors. The species is named for the sea god Proteus of classical mythology (although as Ovid {Metamorphoses) observes, the latter showed rather more extreme changes in morphology than the ammonite bearing his name, having appeared as a young man, a lion, a raging wild bear, snake, bull, stone, and tree, as running water, a river, and fire on occasion). The name should therefore be spelt proteus', proteum is an error. DISCUSSION Our description and illustrations of F. proteus demonstrate how very different adults are from all other adult members of the Mojsisovicsinae, although they are similar in many respects to juveniles of associated Mojsisovicsia (e.g. compare PI. 105, figs. 1 and 3; PI. 105, figs. 4, 10, and 12; PI. 105, figs. 13 and 14). Since the two occur together at all known localities of Falloticeras, one must consider whether the genus is not only a micromorph, but also a microconch, that is to say the male of Mojsiso vicsia. The following observations run counter to this suggestion: 1, in Falloticeras, the early whorls are generally ribbed (e.g. PI. 105, figs. 66, 15u). In Mojsisovicsia the KENNEDY AND COOPER: AMMONITE FALLOTICERAS 803 reverse is generally the case (PL 105, figs. 1/?, 4b, \2a, 13). 2, in Falloticeras the keel declines at maturity, in Mojsisovicsia it strengthens. 3, although Falloticeras always occurs with Mojsisovicsia, the latter has a somewhat wider geographic distribution. 4, Falloticeras is always much rarer than Mojsisovicsia, whereas only one species of Falloticeras occurs in the type area, there are several Mojsisovicsia species recorded. 5, the recorded stratigraphical range of the two genera are dififerent. Falloticeras is confined to the Hoplites dentatus Zone of the Middle Albian (spathi subzone in England), and its equivalents, whilst Mojsisovicsia ranges as high as the Euhoplites loricatus Zone {delariiei subzone in England). Thus there is a strong case for regarding Falloticeras as a micromorph genus. A comparison of juveniles of the other genera of the subfamily (text-fig. 2) suggests that the genus arose as a result of neoteny, with Mojsisovicsia as a possible ancestor. If Falloticeras is a neotenous micromorph, the evolutionary experiment appears to have been less than successful, for Falloticeras was, as far as we know, an evolutionary cul-de-sac. It is not in the mainstream of brancoceratid evolution, and it lacks descendants, as do several other micromorph Acanthocerataceae such as the Flickiidae, and the acanthoceratinid Neosaynoceras. However, this type of evolution can lead to evolutionary success, with neotenous micromorphs giving rise to new genera and subfamilies, for example, in the genus Protacanthoceras Spath, 1923 (Acanthocerataceae), the evolution of which is to be discussed by Wright and Kennedy elsewhere. Acknowledgements. Our best thanks go to Dr. J. Sornay of the Museum d’Histoire Naturelle (Paris), who kindly allowed us to work on specimens in the d’Orbigny Collection, and provided much information. We also thank General M. Collignon (Moirans, Isere) for the use of his collections, Messrs. G. Thomel and O. de Villoutreys for showing us sections in the Alpes Maritimes and H. C. Klinger for help in the field in South Africa. Mr. H. P. Powell, Mr. D. Phillips, Dr. M. K. Howarth, and Dr. H. G. Owen kindly allowed us to study specimens in their care, and also provided useful information, whilst Mr. C. W. Wright kindly reviewed a draft of the manuscript. REFERENCES ARKELL, w. J. et at. 1957. Treatise on Invertebrate Palaeontology L., Mollusca (4). Univ. Kansas Press and Geol. Soc. Amer., xxii + L1-L490. Lawrence, Kansas and New York. BESAiRiE, H. 1936. Recherches geologiques a Madagascar. Premiere suite. La geologie du nord-ouest. Mem. Acad. Malagache, 21, 9-259, pis. 1-24. BREiSTROFFER, M. 1 947. Sur les zones d’ammonites dans I’Albien de France et d’Angleterre. Trav. Lab. Geol. Univ. Grenoble, 26, 1-88 (17-104). CALLOMON, J. H. 1963. Sexual dimorphism in Jurassic ammonites. Trans. Leicester lit. phil. Soc. 57, 21-56. CASEY, R. 1959. Field meeting at Wrotham and the Maidstone By-Pass. Proc. geol. Ass. 70, 206-209. 1961. The stratigraphical Palaeontology of the Lower Greensand. Pa/ucouto/ogv, 3, 487-621, pis. 77-84. COLLIGNON, M. 1949. Recherches sur les faunes albiennes de Madagascar 1. L’Albien d’Ambarimaninga. Annls geol. Serv. Mines Madagascar, 14, 1-128, pis. 1-22. DOUGLAS, J. A. 1921. Geological sections through the Andes of Peru and Bolivia: III From the Port of Callao to the River Perene. Q. Jl geol. Soc. Lond. 77, 246-284, pis. 15-20. KENNEDY, w. J. 1977. Ammonite Evolution. In hallam, a. (ed.). Patterns of Evolution. Elsevier, Amsterdam, London, and New York. and COBBAN, w. a. 1976. Aspects of Ammonite Biology, Biogeography and Biostratigraphy. Spec. Pap. Paleont. 17, 93 pp., 1 1 pis. and KLINGER, H. c. 1975. Cretaceous faunas from Zululand and Natal, South Africa. Introduction, Stratigraphy. Bull. Br. Mus. nat. Hist. (Geol.), 25, 263-315, 1 pi. 804 PALAEONTOLOGY, VOLUME 20 MAKOWSKi, H. 1962. Problems of sexual dimorphism in ammonites. Palaeont. pol. 12, 1-92. MiLBOURNE, R. A. 1963. The Gault at Ford Place, Wrotham, Kent. Proc. geol. Ass. 74, 55-79, pis. 4, 5. ORBiGNY, A. d’. 1840-1842. Paleontologie Fran^aise, Terrains Crhaces. I. Cephalopodes. I 120 (1840); 121-430 (1841); 431-662 (1842); 148 pis. 1850. Prodrome de Paleontologie Stratigraphique Universelle des Animanx Molhisques et Rayonnes II. Paris, 427 pp. OWEN, H. G. 1971. Middle Albian Stratigraphy in the Anglo-Paris Basin. Bull. Br. Mus. nat. Hist. (Geol.), Suppl. 8, 164 pp., 3 pis. PARONA, c. E. and bonarelli, e. g. 1897. Fossili albiani d’Escragnolles, del Nizzardo e della Liguria occidentale. Palaeontogr. Ital. 2, 53-112, pis. 10-14. PICTET, E. J. and CAMPICHE, G. 1858-1864. Materiaux pour la Paleontologie suisse. Description des fossiles du terrain cretace des environs de Sainte-Croix. Geneva, 1-380, pis. 1-53. ROMAN, E. 1938. Les Ammonites Jurassiques et Cretaces. Paris, 554 pp., 53 pis. SPATH, L. F. 1921. On Cretaceous Cephalopoda from Zululand. Ann. S. Afr. Mus. 12, 217-321, pis. 19-26. 1922. On Cretaceous Ammonoidea from Angola, collected by Prof. J. W. Gregory, D.Sc., F.R.S. Trans. R. Soc. Edinb. 53, 91-160, pis. 1-4. 1923-1943. A monograph of the Ammonoidea of the Gault. Palaeontogr. Soc. [Monogr.], 787 pp., 72 pis. VAN HOEPEN, E. c. N. 1941. Die gekielde Ammoniete van die Suid-Afrikaanse Gault. 1. Diploceratidae, Cechenoceratidae en Drepanoceratidae. Paleont. Navors. nas. Mus. Bloemfontein, 1, 55-90, figs. 1-55, pis. 8-19. WESTERMANN, G. E. G. (ed.), 1969. Sexual dimorphism in fossil metazoa and taxonomic implications. Schweizerbart’sche Verlagsbuchhandlung, Stuttgart, iv 1-251. W. J. KENNEDY M. R. COOPER Original typescript received 5 July 1976 Revised typescript received 20 October 1976 Geological Collections University Museum Parks Road Oxford 0X1 3PR THE ECHINOIDS MICRASTER AND EPIASTER FROM THE TURONIAN AND SENONIAN OF ENGLAND by ROBERT B. STOKES Abstract. A revised nomenclature and stratigraphical distribution are recorded for species of the spatangoid genera Epiaster and Micraster from theTuronian and Senonian of southern England. Distinguishing characters of the species are summarized, and the names E. michelini, E. la.xoporus, M. normanniae, M. decipiens, M. corangiumtm simpsoni, and M. westlakei advocated for British material. The old cortestudinarium Zone is here replaced by a lower normanniae Zone, of probable Turonian age, and an upper decipiens Zone, of Coniacian date. These new zones are defined in the Dover cliffs, where the base of the planus Zone, here redefined on the basis of spatangoid faunas, is held to corre- spond with the base of the Chalk Rock. M ICRASTERS from southern England need little or no introduction as they form the evidence for three widely-read classic papers (Rowe 1899; Kermack 1954; Nichols 1959) which are summarized in various text-books and review papers. Rowe described in detail many of the evolutionary trends which affect parts of the test and he emphasized their use in stratigraphy. Kermack’s biometrical study confirmed and extended Rowe’s results, and Nichols interpreted the evolutionary changes in terms of functional morphology by comparison with living spatangoids. Twentieth-century British authors have mainly followed the nomenclature used by Rowe even though he had been unable to consult the most recent taxonomic revision of Micraster made by Lambert in 1895. Kermack (1954, p. 378) pointed out that The systematics of the genus Micraster are in a very unsatisfactory state’. The author has tried to rectify this situation elsewhere (Stokes 1975) and here gives only diagnoses of the English species, omitting their synonymies and lengthy descriptions of the genus and the evolutionary trends to which it was prone. The systematic notes on Epiaster are more detailed than those on Micraster. The stratigraphical ranges of the spatangoids are based on both recent collections and a re-examination of original museum material (see Acknowledgements). Mr. C. J. Wood’s specimens from the cliffs between Dover and South Foreland (TR 325415- 360433) have been invaluable in this study and enable revisions of certain zonal boundaries to be suggested. This paper therefore summarizes a revised nomenclature for species of Epiaster and Micraster from southern England, and indicates their stratigraphical ranges. SYSTEMATIC NOTES The taxonomy of Epiaster and Micraster and their species is somewhat confused because in the past there has been general adherence to a classification based essentially on the presence or absence of fascioles, and there is an abundance of synonyms. [Palaeontology, Vol. 20, Part 4, 1977, pp. 805-821, pis. 106-109.] 806 PALAEONTOLOGY, VOLUME 20 Species names adopted in the stratigraphic section of this paper are therefore defined below. The signs attached to the synonymy list of E. michelini correspond to Richter’s system as advocated by Matthews (1973). Micraster species are treated alphabetically. EPIASTER d’Orbigny, 1855 Type species. Epiaster crassissimus (Defrance), 1827 by the subsequent designation of Lambert (1895). Epiaster has generally been regarded as distinguishable by the absence of all fascioles, whereas Micraster possesses a sub-anal fasciole. Whilst the type species E. crassissimus lacks fascioles, absence or presence of fascioles can no longer be considered a generic characteristic. The really distinctive features of Epiaster are: adults rarely exceed 60 mm in length, and more commonly are in the range 30-50 mm; a very thin test, usually about 0-4 mm thick ; a marked sub-anal heel. The term ‘heel’ is here introduced for raised or attenuated areas of interambulacrum 5 below the periproct, and ‘rostrum’ is restricted to such projections above the periproct (e.g. as in Micraster coranguinum rostratus). At present both these features are called ‘rostrum’. Other characteristics of the genus Epiaster include : a broad and shallow anterior notch (less than 1 mm deep at ambitus); peristome far from the anterior border (one- third to one-quarter of the total length) with, at most, a very feebly projecting labrum; peristome surrounded by a smooth rim and well-developed pores in the adjacent ambulacra; all interambulacra join the peristomal margin and are often thickened here to add strength to the delicate peristomal rim; paired petals are deeply sunken and their conjugate pores are all elongate, in some cases more so in the inner than in the outer rows; interporiferous zones of the paired petals are smooth; unpaired petal is broad with divergent edges, its pores are never conjugate; in the ethmophract apical system, none of ocular plates I, IV, and V touches the madreporite (text-fig. 1); periproct is oval, elongated in a vertical sense, and situated high (70- 90% of total height— see Stokes 1976, for method) on the outwardly sloping posterior face; plastronal tubercles never tightly packed together; periplastronal areas are broad and finely granular; sub-anal fasciole is narrow when developed and often diffuse in nature, on the oral surface it is situated immediately behind a distinct swelling at the posterior of the plastron. Range. ? Aptian, Albian to Lower Maastrichtian. Epiaster michelini (Agassiz), 1847 Plate 107, figs. 4-6, 10, 11; text-fig. la, b * Micraster Michelini Agassiz in Agassiz and Desor 1847, p. 23. Micraster Michelini Agassiz; d’Orbigny 1855, p. 205, pi. 866. Micraster Michelini Agassiz; Desor 1858, p. 363, pi. 41, figs. 5-8. Micraster Michelini Agassiz; Cotteau and Triger 1859, p. 244, pi. 39. ?p. Micraster cor-testiuhnarium Goldfuss; Quenstedt 1874, p. 646, pi. 87, fig. 31, 31o. vp. * Micraster Sanctae-Maurae Gauthier, 1886, p. 356. Material from Saint-Maure only. Micraster Michelini Agassiz', Lambert 1895, p. 192. vp. Micraster corhovis Forbes; Rowe 1899, p. 518. vp. Micraster Leskei Desmoulins; Rowe 1899, p. 525. V. *Micraster leskei war. joviniacensis Lambert in Lambert and Thiery 1924, p. 481, pi. 12, fig. 10. 1 Micraster micrantlms Lambert in Lambert and Thiery 1924, p. 481. STOKES: MICRASTER AND EPIASTER 807 E from Lambert Collection. 808 PALAEONTOLOGY, VOLUME 20 Holotype. Specimen (not seen) represented by cast T 49 in the Agassiz and Desor Collection (Universite de Neuchatel). Stated to be from the Turonian of Touraine by Lambert and Jeannet (1928). Description. Small to medium sized species (30-45 mm long). In the anterior paired petals the pores of rows Ila and IVb are usually more elongate than those of Ilb and IVa, and thus give rise to broader poriferous zones. Pore pairs of the unpaired petal are not at right angles to the edge of the petal but are in the form of ‘V’s pointing towards the apical system. At the ends of the paired petals (in positions where a peri- petalous fasciole is to be found on certain spatangoids) are areas in which tubercles are more or less absent and the granules smaller and more tightly packed than is usual in this region, giving a smooth appearance in comparison with the rest of the upper surface of the test. The sub-anal fasciole is very variable in its development, often incomplete and diffuse. Range. Upper Cenomanian and Turonian. Epiaster laxoporiis (d’Orbigny), 1855 Plate 109, figs. 7-9; text-fig. Ic-e With the exception of Rowe’s specimen from Dover, post-Turonian Epiasters are known only from Touraine and Aquitaine. The ranges of such forms are given from these latter regions (Stokes 1975, figs. 17 and 18) using the trivial names adopted by Lambert (1895) and stratigraphical information in de Grossouvre (1897-1898). Senonian species of Epiaster (previously attributed to Micraster laxoporus d’Orbigny, 1855, M. latiporus Cotteau, 1869, M. carentonensis Lambert, 1895, and Lambert’s variety campaniensis (1895) of M. laxoporus) have been distinguished from each other by such characters as: the number of pairs of pores in the paired petals; the size; the position of the apical system; the development of the heel; the depth of excavation, the length and the flexuosity of the paired petals. Lrom the limited quantitative information given in Lambert (1895) and the few specimens available for study, the author is not convinced that differences between the Senonian species would stand up to statistical treatment if sufficient material were available for such a study. In this paper, therefore, the oldest available name [E. laxoporus) has been used for all post-Turonian Epiasters. The author has been able to examine in detail only four well-preserved Senonian Epiasters, all of which come from the Coniacian Craie de Villedieu of Touraine, Trance : one from Couture and one from Torchay (Lambert Collection both numbered 538 and labelled M. carentonensis), and two from ‘Villedieu’ (Cotteau Collection both labelled M. laxoporus). Of the several characters measured and counted, only the relative length of the anterior paired petals could be used to distinguish these specimens from E. miclielini. In the latter species the length of the anterior paired petals is over 30% of the length of the test (four specimens: 30-2, 30-3, 31-4, and 33-8%) whereas in the Senonian species these petals are shorter and do not reach 30% of the length of the test (four specimens: 25-3, 26T, 27-7, and 29-2%). The length of the test was measured, using external calipers, from the most anterior part of the test to the most posterior point above the periproct; the length of the right anterior paired petal was measured, using internal calipers under a binocular microscope. STOKES: MICRASTER AND EPIASTER 809 from the contact with the ocular plate to the adoral suture of the farthest plate bearing enlarged pores. Range. Coniacian to Lower Maastrichtian. MICRASTER Agassiz, 1836 Type species. Micraster coranguimmi (Leske, 1778), by the subsequent designation of Pomel (1883). The numerous evolutionary trends to which Micraster was prone (Stokes 1975, pp. 81-84) make a succinct diagnosis of this genus almost impossible. The test is thick (1-2 mm), except in M. corhovis whose test is thin as in Epiaster; the depth of the anterior notch is very variable ; the peristome may be one-third of the total length from the anterior border, marginal, or any where in between these extremes; the labrum may be feebly projecting to strongly projecting such that it completely covers the peristome ; the number of interambulacra joining the peristomal margin is variable ; paired petals vary from deeply sunken to superficial, their pores are conjugate with the outer rows elongate and the inner rows typically round; interporiferous zones of the paired petals vary from smooth to divided ; pores of the unpaired petal usually round, those of one pair being separated by granules, but sometimes developed like those of the paired petals ; the number of ocular plates touching the madreporite varies from two to five ; the periproct is usually round, situated at a very variable height from the base of the test; plastronal tubercles often tightly packed together; peri- plastronal areas varying from fine to coarsely granular, sometimes with tubercles present; a distinct sub-anal fasciole is usually present but this may be absent and a supplementary peripetalous fasciole may be incompletely developed. Range. Middle Turonian to Lower Maastrichtian. Micraster coranguinum (Leske), 1778 Figured as M. coranguinum by Chatwin 1924, pi. 2, figs. 4, 5, 10. Although variable in form and size, this species is typified by: a sharp groove which runs down the mid-line of each paired petal (‘interporiferous zones divided’) ; coarsely granulated periplastronal areas ; an anterior notch which is deeper than in M. decipiens ; the whole peristome being hidden by the labrum when the echinoid is viewed from below; the peristome being closer to the anterior border than in M. decipiens. Range, coranguinum Zone to pihda Zone {M. coranguinum s.l.), coranguinum Zone to Marsupites Zone {M. coranguinum s.s.). Micraster coranguinum rostratus (Mantell), 1822 Plate 108, figs. 4-6 The distinctive features of this subspecies are; adults are usually 50-70 mm in length; a subconical shape; a strongly arched carina which overhangs the low periproct; pores of the unpaired petal tend to become conjugate ; pores of the paired petals more numerous than in M. coranguinum s.s. Range. Marsupites Zone. 810 PALAEONTOLOGY, VOLUME 20 Micros ter coranguinum simpsoni Stokes, 1975 Plate 109, figs. 4-6 This broad and low subspecies is usually 45-50 mm in length and is typified by: a test somewhat thinner than that of M. coranguinum s.s.; a long and narrow labral plate; a gently curved carina which overhangs the periproct; areas between the pore zones of the paired petals which have lost the distinctive mid-line groove characteristic of M. coranguinum s.s. Range. Marsupites Zone and pilula Zone. Micraster corbovis Forbes, 1850 All specimens of this species have: a thin test, usually about 0-5 mm thick; relatively short paired petals whose areas between the pore zones are smooth; the peristome relatively far from the anterior border and lacking a projecting labrum. Range, lata Zone and planus Zone. The planus Zone form of Micraster corbovis Plate 106, figs. 1 -3 This rare form, which is represented by the type specimen, is distinguished by: its large size, being up to 80 mm in length; its swollen aspect. The lata Zone form of Micraster corbovis Plate 106. figs. 4- 6 This form is less rare than that of the planus Zone and is typified by: a side profile which shows that the maximum height is close to the anterior; its small size which rarely exceeds 50 mm in length; its steep anterior slope and gentle posterior slope of the upper surface when viewed in profile. Micraster decipiens (Bayle), 1878 Plate 108, figs. 1-3 This is the species which has usually been called M. eortestudinarium and it is dis- tinguished by: a very rounded outline when viewed from above or below; the groove EXPLANATION OF PLATE 106 Figs. 1-3. Micraster corbovis Forbes. The type specimen from Sussex representing the planus Zone form of the species. Oral, apical, and left lateral views. BM(NH) E 30157, x 1. Figs. 4-6. Micraster corbovis Forbes. The lata Zone form of the species. 4 and 5, oral and apical views of a specimen from the planus Zone (sensu Rowe) of Dover, Rowe Collection, BM(NH) E 37706. 6, right lateral view of a specimen from the lata Zone of Dover, Rowe Collection, BM(NH) E 37695, x 1. PLATE 106 STOKES, Micraster corhovis ill 812 PALAEONTOLOGY, VOLUME 20 which runs down the mid-line of the paired petals is broader and less sharp than in M. coranguimim (‘interporiferous zones subdivided’); when viewed in profile the upper surface is rather symmetrically arched ; the peristome is further from the anterior border than in M. coranguinum, and it is not completely hidden by the labrum when viewed from below. Range, normanniae Zone to basal part of coranguinuni Zone. Micraster gibbus (Lamarck), 1816 Figured as M. (Isomicraster) senonensis by Kermack 1954, pis. 24-26, figs. 13, 15, 17. This uncommon species is distinguished by : a conical shape ; a low periproct, situated between 45 and 56% of the total height ; a tendency in the unpaired petal for there to be a groove between the pores in each pair (‘conjugate pores’), i.e. the unpaired petal is like the paired petals; a reduction or absence of the sub-anal fasciole. Range, deeipiens Zone and coranguinum Zone. Micraster leskei (Des Moulins), 1837 Plate 108. figs. 7-9 Typical specimens of this species are: small, not often exceeding 40 mm in length; relatively narrow, but high compared with M. normanniae', lacking a groove along the mid-line of the petals, but under a hand-lens the sutures between the ambulacral plates are visible; having a peristome about a quarter to a third of the length from the anterior border, and a feebly developed labrum. Range, planus Zone. Micraster normanniae Bucaille, 1883 Plate 107, figs. 1-3, 7-9 The distinguishing features of this rare species are: when viewed from above the maximum breadth is close to the anterior; the side profile is markedly flat and low; the paired petals are relatively short. Range. Upper part of planus Zone and normanniae Zone. EXPLANATION OF PLATE 107 Figs. 1-3. Micraster twrmatmiae Bucaille. Apical, oral, and left lateral views of a specimen from the base of the corteslitdinarium Zone of Dover, between two strong flint lines 15 ft {4-57 m) apart (Rowe’s MS. label). Rowe Collection, BM(NH) E 38020, x 1. Figs. 4-6. Epiaster michelini (Agassiz). Apical, oral, and left lateral views of a specimen from 0-2 m below the Chalk Rock, Kensworth, Herts., author’s collection No. 2360, x 1. Figs. 7-9. Micraster normanniae Bucaille. Apical, oral, and left lateral views of the type specimen from the ‘lit tubule’ in the cliff's at Pollet, Seine Maritime, France. Bucaille Collection, Museum d’Histoire naturelle de Rouen, x 1 . Figs. 10 and 1 1. Epiaster michelini (Agassiz). Apical and right lateral views of a plaster cast of the type specimen from the Turonian of Touraine. Cast T 49, Agassiz and Desor Collection, Universite de Neuchatel, x 1 . PLATE 107 STOKES, Micraster and Epiaster 814 PALAEONTOLOGY, VOLUME 20 Micros ter westlakei Stokes, 1975 Plate 109, figs. 1-3 This rare species, which resembles M. coranguinum, is distinguished by : its large size, being 60-70 mm in length; the strong curve of the carina when viewed in profile; a relatively low periproct; an almost marginal peristome covered by a strongly projecting labrum. Range, nmcronata Zone. Rowe introduced the name Micraster praecursor (without designating a type specimen) for a range of Micraster which had in common only a breadth less than length, and decoration which Rowe collectively described as ‘low-zonal’. Under M. praecursor he included forms here separated into M. decipiens, M. normanniae, and large forms of M. leskei, together with a variety of other species which have never been found in England. For these reasons the name is abandoned. THE TURONIAN AND SENONIAN SPATANGOID SUCCESSION IN SOUTHERN ENGLAND Definitions of certain zonal boundaries are given in the section on Chalk stratigraphy. Epiaster occurs in the labiatus Zone at Seaton, Devon. The specimen (Wright’s Collection) recorded by Kermack (1954) as M. leskei, is an Epiaster. Likewise, all the specimens in Rowe’s Collection from the south Devon ‘Cuvieri Zone’, which he called M. eorbovis, are Epiaster. Specimens of Epiaster from the lata Zone were collected by Rowe from the Hooken-White Cliff region. South Down Common, and Compton Bay. From the planus Zone Rowe collected specimens from Pinhay Bay, Westerham, and east of Dover. In Mr. Wood’s Dover collection it can be seen that the Epiaster stock ranges up into the lower part of the Chalk Rock where it occurs with intermediates to M. leskei. Above the Chalk Rock the only known specimen of Epiaster is an E. cf. laxoporus in the Rowe Collection recorded as M. eorbovis from 6 m above the base of the Cortestudinarium Zone (Rowe 1899). The lota Zone form of M. eorbovis is not common and does not range as high as the Chalk Rock in Wood’s Dover material. The author has not seen any specimens of the planus Zone form of M. eorbovis which have been collected bed by bed. M. leskei first appears in the Chalk Rock. The author has found only the typical small form in the lowest Chalk Rock hardground at Kensworth, Flerts., which is immediately followed by an horizon yielding fragments of a very large Micraster. EXPLANATION OF PLATE 108 Figs. 1-3. Micraster decipiens Apical, oral, and left lateral views of a specimen from Purley, Surrey. T. Wright Collection, BM(NH) E 1512, x 1. Figs. 4-6. Micraster coranguimon rostratus (Mantell). Apical, oral, and right lateral views of the type specimen from the Chalk near Brighton. Mantell Collection, BM(NH) E 8662, x 1. Figs. 7-9. Micraster leskei (Desmoulins). Apical, oral, and left lateral views of a specimen from the Chalk Rock of Dover. J. D. Hollis Collection, x 1. PLATE 108 STOKES, Micraster 816 PALAEONTOLOGY, VOLUME 20 From a second hardground, 0-7 m above the first, I have collected a distinctive medium-sized variety of M. leskei. Intermediates between E. michelini and M. leskei occur in the Wood Collection from the Chalk Rock, but typical specimens of the latter are lacking. In the lower part of the Chalk Rock at Dover large forms of M. leskei have already appeared. Many of the Micraster from the mass of the planus Zone, which many authors may call M. corbovis and/or M. praecursor, are here included amongst large forms of M. leskei. Intermediates between M. leskei and M. normanniae occur throughout the planus Zone above the Chalk Rock. Whilst the typical form of M. normanniae is found within the 1-5 m of chalk above the Top Rock, early specimens of this species appear in the upper 1-5 m of the planus Zone. The commonest Mieraster of the old ‘Cortestudinarium Zone’ is M. deeipiens. The earlier ones, from the normanniae Zone and the lower half of the deeipiens Zone, are not as rounded in outline as the higher ones seen which are closer to the type. Many of the large M. leskei from the upper part of the planus Zone have features which indicate that they are transitional to M. deeipiens. The earliest specimen of M. gibbus known to the author is that collected by Mr. Wood some 4-5 m above the Top Rock at Dover. The latest occurrence of this species seems to be in the Barrois Sponge Bed on Thanet. In the eoranguinum Zone intermediates between M. gibbus and M. eoranguinum occur. This pair of sympatric species and its intermediates has been discussed by Kermack (1954) and Stokes (1976). M. eoranguinum, from Wood’s Dover material, first appears between two marl seams which are respectively 18 and 20 m above the Top Rock. M. deeipiens is still present at this horizon, and indeterminable specimens of Mieraster occur in the 9 m of chalk above the lower of the two marls. Throughout much of its zone, M. eoranguinum is not particularly common and bed by bed collections are lacking. The species becomes relatively abundant from Whitaker’s ‘3-inch’ Band to 1 -5 m above the Barrois Sponge Bed on the Thanet coast. From museum material it is seen that advanced forms of M. eoranguinum continue into the Marsupiles Zone. A broad flat Micraster collected by the author from the Barrois Sponge Bed is indistinguishable from M. rogalae of the Northern Faunal Province (see Kermack 1954 and Stokes 1975), and may thus indicate either a migration of northern elements or homoeomorphy. M. eoranguinum rostratus is known to the author only from museum material of which the horizon is simply stated to be the Marsupites Zone. EXPLANATION OF PLATE 109 Figs. 1-3. Micraster westlakei Stokes. Figs. 1 and 2, apical and right lateral views of the type specimen No. 3320, X 1. Fig. 3, oral view of specimen No. 3321. Both specimens from the mucronata Zone, Tich- bourne Farm, Hants. Westlake Collection, University of Southampton, x 1. Figs. 4-6. Micraster eoranguinum simpsoni Stokes. Apical, oral, and left lateral views of the type specimen from the tectiformis horizon of the pHula Zone, Saltdean, Sussex. R. Simpson Collection S54, x 1 . Figs. 7-9. Epiaster laxoporus (d’Orbigny). Oral, apical, and left lateral views of a specimen from the Craie de Villedieu (Coniacian), Villedieu, Loir et Cher, France. Cotteau Collection, Universite d’Orsay, x I. PLATE 109 STOKES, Micraster and Epiaster LANGDON STAIRS M.CORANGUINUM M. DECIPIENS M.NORMANNIAE -O "ols 3 metres o Cb o 1 •l* c TOP - ROCK EAST CLIFFS *1* • • H. PLANUS obscured T. LATA CHALK ROCK BASAL r COA\PLEX ® o "*1 FOUR FOOT mJ BAND TEXT-FIG. 2. Stratigraphical distribution of spatangoids in the Dover cliffs, w ^ marl band; t = tabular flint band; stipples = important hardground; each spot represents one specimen. With the exception of E. cf laxoporus, which is from the Rowe Collection, all specimens are from the C. J. Wood Collection. The section was measured at Langdon Stairs (TR 346 425) and Mr. Wood indicated the horizons from which his specimens were collected. See text for definitions of zonal boundaries. STOKES: MICRASTER AND EPIASTER 819 Micraster coranguinum simpsoni first appears in the Marsupites Zone. Mr. Simpson has collected it from the upper part of this zone at Friars Bay, Sussex, and the author has collected a loose specimen from the cliffs at Cliftonville near Margate where only the Marsupites Zone is exposed. In the lower part of the pilula Zone the subspecies is common at Saltdean. Micraster is apparently absent from the remainder of the Lower Campanian in southern England. M. westlakei is known from only three specimens in the Westlake Collection, all coming from the mucronata Zone of Tichbourne Farm, Hants. From this pit Mr. Hollis collected a small conical Echinocorys which is here interpreted as indicating an horizon low in the mucronata Zone. Micraster is quite common in the mucronata Zone at Studland Bay, but the crushed and fragmentary material collected there by the author cannot be identified. Kermack (1954) recorded a very large Micraster glyphus in the Hawkins Collection from the mucronata Zone of the Isle of Wight. Assuming this identification to be correct, the specimen indicates a southern migration of the Northern Faunal Province stock. IMPLICATIONS FOR CHALK STRATIGRAPHY OF THE DOVER SPATANGOID SEQUENCE The lata-planus Zone boundary has been drawn at various horizons. Rowe (1900) placed it at a marl band 2-9 m below the base of the Chalk Rock on the grounds that it was at this level that one first finds an association of Holaster planus, Micraster, and Echinocorys. Rowe did not state which species of Micraster he found, and a perusal of his faunal records in the lata Zone suggests that it was the appearance of Echinocorys that was the deciding factor. Numerous records of Echinocorys in the lata Zone (Hayward 1940) show that such a definition is unacceptable. On the spatangoid faunas it would be more sensible to place the zonal boundary at the base of the Chalk Rock in which we see the appearance of large forms of M. leskei and transitions between E. michelini and M. leskei. In other localities typical small M. leskei appear within the Chalk Rock. The planus-cortestudinarium Zone boundary. It is now difficult to decide from Rowe’s description which horizon he took for this boundary, but he said that it coincided with the disappearance of Holaster planus itself, M. corbovis, and M. leskei. This is generally held to correspond to the upper limit of the Top Rock. M. decipiens predominates in the chalk above the Top Rock and ought to give its name to this zone, following de Grossouvre’s (1895-1896) reference to this part of the English succession as the ‘Craie a Micraster decipiens'. The 1 - 5 m of chalk above the Top Rock at Dover yield M. normanniae and would be regarded as a separate normanniae Zone, between the planus and decipiens Zones, on the Normandy coast (Cayeux 1967). In view of the fact that Mr. C. W. Wright has collected Turonian ammonites from the lower part of the cortestudinarium Zone (pers. comm. 1968), and that a comparison of the spatangoid faunas of the north- west and south-east of the Paris Basin suggests that the normanniae Zone is Turonian (Stokes 1975), it seems desirable to admit a normanniae Zone in southern England. LANGDON STAIRS M.CORANGUINUM M. DECIPIENS M.NORMANNIAE .o DJD 3 metres • I u • •,•4 OA TOP - ROCK EAST CLIFFS •l* • • I H. PLANUS obscured T. LATA CHALK ROCK BASAL C0A\PLEX ® o •e N O C3 . « "'1 FOUR FOOT m-T BAND TEXT-FIG. 2. Stratigraphical distribution of spatangoids in the Dover cliffs. «;==marl band; r = tabular flint band; stipples = important hardground; each spot represents one specimen. With the exception of E. cf. laxoporus, which is from the Rowe Collection, all specimens are from the C. J. Wood Collection. The section was measured at Langdon Stairs (TR 346 425) and Mr. Wood indicated the horizons from which his specimens were collected. See text for definitions of zonal boundaries. STOKES: MIC RASTER AND EPIASTER 819 Micraster corangidnum simpsoni first appears in the Marsupites Zone. Mr. Simpson has collected it from the upper part of this zone at Friars Bay, Sussex, and the author has collected a loose specimen from the cliffs at Cliftonville near Margate where only the Marsupites Zone is exposed. In the lower part of the pilula Zone the subspecies is common at Saltdean. Micraster is apparently absent from the remainder of the Lower Campanian in southern England. M. westlakei is known from only three specimens in the Westlake Collection, all coming from the miicronata Zone of Tichbourne Farm, Hants. From this pit Mr. Hollis collected a small conical Echinocorys which is here interpreted as indicating an horizon low in the mucronata Zone. Micraster is quite common in the mucronata Zone at Studland Bay, but the crushed and fragmentary material collected there by the author cannot be identified. Kermack (1954) recorded a very large Micraster glyphus in the Hawkins Collection from the mucronata Zone of the Isle of Wight. Assuming this identification to be correct, the specimen indicates a southern migration of the Northern Faunal Province stock. IMPLICATIONS FOR CHALK STRATIGRAPHY OF THE DOVER SPATANGOID SEQUENCE The lata-planus Zone boundary has been drawn at various horizons. Rowe (1900) placed it at a marl band 2-9 m below the base of the Chalk Rock on the grounds that it was at this level that one first finds an association of Holaster planus, Micraster, and Echinocorys. Rowe did not state which species of Micraster he found, and a perusal of his faunal records in the lata Zone suggests that it was the appearance of Echinocorys that was the deciding factor. Numerous records of Echinocorys in the lata Zone (Hayward 1940) show that such a definition is unacceptable. On the spatangoid faunas it would be more sensible to place the zonal boundary at the base of the Chalk Rock in which we see the appearance of large forms of M. leskei and transitions between E. michelini and M. leskei. In other localities typical small M. leskei appear within the Chalk Rock. The planus-cortestudinarium Zone boundary. It is now difficult to decide from Rowe’s description which horizon he took for this boundary, but he said that it coincided with the disappearance of Holaster planus itself, M. corbovis, and M. leskei. This is generally held to correspond to the upper limit of the Top Rock. M. decipiens predominates in the chalk above the Top Rock and ought to give its name to this zone, following de Grossouvre’s (1895-1896) reference to this part of the English succession as the ‘Craie a Micraster decipiens'. The 1 - 5 m of chalk above the Top Rock at Dover yield M. normanniae and would be regarded as a separate normanniae Zone, between the planus and decipiens Zones, on the Normandy coast (Cayeux 1967). In view of the fact that Mr. C. W. Wright has collected Turonian ammonites from the lower part of the cortestudinarium Zone (pers. comm. 1968), and that a comparison of the spatangoid faunas of the north- west and south-east of the Paris Basin suggests that the normanniae Zone is Turonian (Stokes 1975), it seems desirable to admit a normanniae Zone in southern England. 820 PALAEONTOLOGY, VOLUME 20 However, it must be emphasized that such a zone is based solely on Micraster and that correlation with the ammonite sequence is not yet known. The normanuiae Zone, resulting from the boundaries defined above and as shown in text-fig. 2, is a concurrent range zone and as such it is perhaps somewhat unsatis- factory. It might be better to lower the base of this zone to the first appearance of M. normanniae (as suggested to me by Mr. Wood, pers. comm. 1972) making the normanuiae Zone a local-range zone. Such a revision may be closer to the zonal system used in north-west France where M. normanniae is not recorded below the base of its zone (Cayeux 1967). The cortestudinarinm-corangiiinum Zone boundary. It would seem logical to place the base of the coranguinum Zone at the lower of the two marl bands, 18 and 20 m above the Top Rock respectively, between which M. coranguinum first appears at Dover. Rowe (1899, 1900) placed the base of the coranguinum Zone some distance below the appearance of M. coranguinum as he understood the species. The result was that he had a ‘lower third of the coranguinum Zone’ and sometimes a ‘lower fourth’, in which ‘M. praecursof and ‘M. cortestudinarium' were said to occur but ‘M. coranguinum' was absent. In spite of the detailed descriptions given by Rowe (1899, pp. 512-513) the author has found it impossible to follow his zonal division. Knowing that he (Rowe 1900) took horizons which differ by 10-3 m for the base of the coranguinum Zone at Langdon Stairs and St. Margaret’s Bay (pers. comm, of Dr. R. Shephard-Thorn and Mr. C. J. Wood 1969), which are only 3 km apart, one doubts if Rowe himself could really fix this boundary with confidence. Acknowledgements. I thank Dr. J. M. Hancock for his advice, encouragement, and help in drafting an original version of this paper. The details of the distribution of spatangoids in the Dover cliffs would not have been possible without the excellent bed-by-bed collection of Mr. C. J. Wood, to whom I am most grateful for access to his collection (Institute of Geological Sciences, London) and helpful discussion. I am likewise indebted to Messrs. J. D. Hollis, R. F. Simpson, and C. W. Wright. For access to collections in their care I thank Drs. R. P. S. Jefferies and H. G. Owen (British Museum (Natural History)— Dixon, Mantell, Rowe, and T. Wright Collections), Professor F. Hodson (University of Southampton— Westlake Collection), Professor J.-P. Schaer (Universite de Neuchatel— Agassiz and Desor Collection), Dr. J. Manivit (Universite d'Orsay— Cotteau Collection), Dr. D. Pajaud (Universite Pierre et Marie Curie — Lambert Collection), and M. Leclerc (Museum d’Histoire naturelle de Rouen— Bucaille Collection). I thank Dr. W. J. Kennedy and Miss Helen Cooper for the photography. Professor J.-P. Lehman (Museum national d’Histoire naturelle, Paris) kindly gave permission to republish the figures of M. coranguinum simpsoni and M. westlakei. Most of this work was carried out during the tenure of a N.E.R.C. studentship, and continued with a grant from the C.N.R.S. ; both these grants are gratefully acknowledged. REFERENCES AGASSIZ, L. and desor, e. 1847. Catalogue raisonne des Echinides. Ann. Sc. nat., Zool. (3), 7 and 8, 167 pp., 1 pi. BAYLE, E. 1878. Eossiles principaux des terrains. E.xplic. Carte geol. France, 4, 158 pis. BUCAILLE, E. 1883. Etude sur des Echinides fossiles du Departement de la Seine-Inferieure. Bull. Soc. geol. Normandie, 8, 16-39, 8 pis. CAYEUX, L. 1967. Repartition des Echinides du Coniacien du Bee de Caux. Ibid. 57, 21-38, pis. 1-3. CHATWiN, c. p. 1924. The use of Micraster in Zoning anclThe Groups of Micraster. In dewey, h., bromehead, c. E. N., CHATWIN, c. p. and DINES, H. G. The Geology of the Country around Dartford. Mem. Geol. Surv. U.K., 18-22, pi. 2. STOKES; MICRASTER AND EPIASTER 821 COTTEAU, G. and TRIGER, J. 1855-1869. Echmides du departemeiit de la Sartbe, Bailliere, Paris. 458 pp., 75 pis. DEFRANCE, J. L. 1827. Spatanguc fossile. In Diclionmiire des Sciences naturelle, 50, 93-97. DES MOULINS, c. 1837. Etudes sur les Echinides. Troisieme Memoire siir les Echinides. Actes Soc. Linn. Bordeaux, 9, 522 pp. FORBES, E. 1850. Notes on Cretaceous Echinodermata. In dixon, f. The Geology and Fo.ssils of the Tertiary and Cretaceous Formations of Sussex. Longman, Brown, Green, Longmans, London. Pp. 325-343, pis. 19-25. GAUTHIER, V. 1886, Description de trois Echinides nouveaux recueillis dans la craie de I’ Aube et de I’Yonne. C.R. Assoc, frang. Avanc. Sc., Congr. Grenoble. Pp. 356-362, pi. VI. GROSSOUVRE, A. DE. 1895-1901. Rechcrclies sur la craie superieure. Premiere partie: Stratigraphic generale. Mem. Carte geol. det. France, 1013 pp., 3 pis. HAYWARD, J. F. 1940. Some variations in Echinocorvs in south-eastern England. Proc. Geol. Assoc. 51, 291-310. KERMACK, K. A. 1954. A Biometric Study of Micraster coranguinum and M. (Isomicraster) senonensis. Phil. Trans. Roy. Soc. Fond. B, 237, 375-428, pis. 24-26. LAMARCK, J.-B. DE. 1816. Histoire naturelle des animaux sans vertehres, 3. Verdiere, Paris. iv+ 586 pp. LAMBERT, J. 1895. Essai d’une monographic du genre Micraster et notes sur quelques Echinides. In GROSSOUVRE, A. DE. 1895. Recherclies sur la craie superieure, pp. 149-267. and JEANNET, A. 1928. Nouveau catalogue des moules d’Echinides fossiles du Musee d'EIistoire naturelle de Neuchatel. Mem. Soc. helv. Sc. nat. 64, 79-233, 2 pis. and THIERY, p. 1909-1925. Essai de nomenclature raisonnee des Echinides. Chaumont, Eerriere. 607 pp., 15 pis. LESKE, N. G. 1778. Jacobi Theodori Klein Naturalis Dispositio Echinodernuitum. Addimenta ad Kleinii dispositionem Echinodernuitum. Lipsiae, Othcina Gleditschiana. 22-1-279 pp., 54 pis. MANTELL, G. 1822. The Fossils of the South Downs or Illustrations of the Geology of Sussex. Lupton Relfe, London. xvi4 327 pp., 41 pis. MATTHEWS, s. c. 1973. Notes on open nomenclature and on synonymy lists. Palaeontology, 16, 713-719. NICHOLS, D. 1959. Changes in the heart-urchin Micraster interpreted in relation to living forms. Phil. Trans. Roy. Soc. Fond. B, 242, 347-437, pi. 9. ORBIGNY, A. d’. 1854-1860. Paleontologie frangaise. Terrains cndaces, VI, Echinides irreguliers. Masson, Paris. 597 pp., 206 pis. POMEL, A. 1883. Classification methodique et Genera des Echinides vivants et fossiles. Jourdan, Alger. 132 pp., 1 pi. QUENSTEDT, F. A. 1874, Petrefactenkunde Deutschlands, Aht. I, Bd. 3, Die Echiniden. Lues’s Verlag, Leipzig. 720 pp., 90 pis. ROWE, A. w. 1899. An Analysis of the Genus Micraster, as determined by rigid zonal collecting from the Zone of Rhvnchonella Cuvieri to that of Micraster cor-anguinum. Q. Jl Geol. Soc. Fond. 55, 494-547, pis. 35-39. ' 1900. The Zones of the White Chalk of the English coast. Part 1. Kent and Sussex. Proc. Geol. Assoc. 16, 289-368. STOKES, R, B, 1975. Royaumes et provinces fauniques du Cretace etablis sur la base d’une etude systematique du genre Micraster. Man. Mus. nat. Hist, nat., C, 31, 94 pp., 12 pis. 1976. Distinction between sympatric species of Micraster (Echinoidea) from the English Chalk. Palaeontology, 19, 689-697. Typescript received 23 September 1974 Revised typescript received 1 December 1976 R. B. STOKES c/o 21 Watton Road SwalTliam Norfolk PE37 7ES % c b- 'c I. i: A* • c • rM A NEW NON-CALCIFIED ALGA FROM THE UPPER SILURIAN OF MID WALES by DIANNE EDWARDS Abstract. The alga, Powysia hassettii gen. et sp. nov., is described from the early Ludlow Series at Llangammarch Wells, Powys, mid Wales. The most complete specimen consists of a thallus differentiated into holdfast, stipe, and much branched distal region, all of which appear to have a tubular construction. Reproductive structures have not been found. Comparison is made with living and fossil algae, but the precise affinities of these Welsh fossils, in which a thallus of such marked morphological differentiation has an apparently simple internal structure, remain unresolved. In 1972, while collecting Silurian graptolites on a field excursion to the Builth Wells- Llangammarch Wells area of Powys in mid Wales, members of the Brecon County Naturalists Trust, led by Dr. M. G. Bassett, discovered two specimens in part and counterpart of a branching, non-calcified alga. The material came from an old quarry on the side of the road running eastwards along the south bank of the River Irfon, 250 m SE. of Llangammarch Wells Church (SN 9374 4720). Subsequently a third specimen was collected from the same locality. All the specimens came from scree on the quarry floor, but the lithology is undoubtedly that of the in situ rock, comprising hard dark grey, flaggy-bedded, slightly calcareous graptolitic siltstones and shales. The plants are preserved mainly as brown or yellow stained impressions but carbon- aceous residues of the original thallus are present in some areas. In a few instances iron ?hydroxide casts of small fragments of axes are present. The flattened algae look remarkably like pressed herbarium specimens; the contrast between rock and fossil being enhanced by an area of powdery lighter rock immediately outside the thallus. A similar zone is also seen around some graptolites. Although associations of graptolites and plants have been described from widely separated late Silurian and early Devonian localities (Bohemia, Obrhel 1962; Australia, Lang and Cookson 1935; Jaeger 1967; Alaska, Churkin et al. 1969), they have hitherto been only briefly recorded from Britain (see, for example. Straw 1953, p. 215). The plants from the Llangammarch locality, however, differ from those in previously described associations in that they are non-vascular. An account of the locality is given by Bassett in Baker and Hughes (in press) who list a faunal assemblage indicative of the lower nilssoni Zone (Eltonian). The presence of Monogr aphis ludensis (Murchison) in the assemblage possibly suggests that some of the beds may belong to the ludensis Zone of the uppermost Wenlock, although M. ludensis itself does occur in earliest Ludlow beds elsewhere. Graptolites accompanying the algae on the blocks have been identified by Dr. B. Rickards as follows: NMW. 72 39G. la Boheinograptus hohemicus {^eixxdindQ) 1 Saetograptus varians (Wood) NMW. 72 46G. 1 S. varians (Wood) NMW. 72 39G. 2b 5. varians (Wood) 1 Pristiograptus duhius (Suess) [Palaeontology, Vol. 20, Part 4, 1977, pp. 823-832, pis. 110-111.] 824 PALAEONTOLOGY, VOLUME 20 SYSTEMATIC PALAEONTOLOGY Algae INCERTAE SEDIS Genus powysia gen. nov. Type species. P. bassettii sp. nov. Derivation of name. Erom Powys, the Welsh county. Diagnosis. Macroscopic non-calcified alga with thallus diflferentiated into expanded basal region with short cylindrical outgrowths (holdfast), unbranched stipe, and much branched distal region. Branching irregular with axis width decreasing distally. Thallus composed of longitudinally aligned intertwined tubes (siphons or filaments) approximately the same size, numerous in the wider branches and stipe but decreasing to two or three in both the narrow ultimate and the short truncated lateral branches. Reproductive structures not seen. Powysia bassettii sp. nov. Plate 110, figs. 1-5; Plate 111, figs. 1-10 Diagnosis. As for genus. Locality. Llangammarch Wells, Powys, Wales. Quarry opening off south side of road running eastwards along south bank of River Irfon, 250 m SE. of Llangammarch Church (SN 9374 4720). Plants associated with graptolites on darkish grey flaggy-bedded shales; blocks loose on quarry floor. Faunal assemblage indicative of lower nilssoni Zone (Eltonian), Ludlow Series, Upper Silurian. Holotype. Specimens NMW. 72 39G. la and lb. Department of Geology, National Museum of Wales, Cardiff. Derivation of name. After Dr. M. G. Bassett who found the specimens. Description of plants. The following account is based on information from all three specimens. That designated the holotype (NMW. 72 39G. la) has been most informative for the gross morphology of the alga (PI. 110, fig. 1). The thallus is differentiated into three regions; an expanded basal part, a short, stout stipe, and a distal much branched ‘frond’. Its counterpart (NMW. 72 39G. lb) was partially destroyed to provide samples for chemical analysis. The most fragmentary specimen (NMW. 72 46G. 1) which lacks a counterpart, has only branch tips present. Much of the evidence for the internal structure of the branches was obtained from the isolated fronds on specimen NMW. 72 39G. 2a and its counterpart (2b). The slightly expanded region at the base of the stipe is interpreted as a holdfast (PI. 1 10, fig. 2). Depressions and protrusions approximately a millimetre in diameter give an irregular appearance to the surface of the plant and the underlying rock EXPLANATION OF PLATE 110 Figs. 1-5. Powysia bassettii. 1, holotype. Note part of graptolite alongside on the left. Arrow indicates central thickened region, xl-7. 2, basal holdfast region enlarged. Protrusions are arrowed, x71. 3, isolated tube in stipe region, x 30 (NMW. 72 39G. la). 4, counterpart of holotype from which organic material removed for analysis by Dr. K. Niklas. Isolated holdfast is arrowed, x L9 (NMW. 72 39G. lb). 5, iron stained specimen with some structural detail, x 1-9 (NMW. 72 39G. 2b). PLATE 110 EDWARDS, Silurian non-calcified alga 826 PALAEONTOLOGY, VOLUME 20 matrix. One such protrusion is seen in profile: it is 1-2 mm high, 1-2 mm wide at its base, and increasing to 1-8 mm diameter distally (PI. 110, fig. 2). It seems possible that these basal extensions were involved in the anchoring of the alga to the sub- stratum. Details of the internal structure of the holdfast region are unknown. Very little carbonaceous residue remains particularly at the extreme base of the fossil where carbonaceous strands ramify between the irregularities in the rock surface. A further isolated holdfast was originally present on thecounterpart (NM W. 72 39G. 1 b ; PI. 1 10, fig. 4). This showed the same over-all features as the one described above, but was less well preserved. Traces of it are visible on the holotype. The holdfast in the intact plant on the holotype passes into a short unbranched axis 3-5-4-0 mm in diameter and 5-0 mm long. The carbonaceous residue in this area is thick, particularly towards the centre suggesting that the organ was cylindrical and not flattened in life. The surface of the stipe is longitudinally striated but any further anatomical details are obscured by the regular cleat-like fracture of the carbon. Evidence for a tubular or filamentous construction comes from a parallel sided element, or strip of carbonaceous material OT mm wide, projecting from the right- hand edge of the stipe (PI. 1 10, fig. 3) and from similar, but less well preserved, struc- tures on the frayed left-hand margin. Whether or not the stipe consists entirely of such elements longitudinally orientated cannot be determined. The stipe divides unequally distally : the wider right-hand branch (2-7 mm diameter) branches repeatedly producing the main body of the thallus. The narrower left-hand branch (2-4 mm) divides again but soon peters out. The thallus gives the over-all impression of irregular branching, in which it is possible to distinguish several different kinds of lateral branch. Many attempts have been made to demonstrate a pattern of branching, i.e. a repeated sequence of the different categories, and although these have been unsuccessful, a few generalizations may be made. Branching angles vary: those in the proximal branches are wide, those of the narrower distal branches are more acute. The diameter of the branches decreases on the whole from base to apex. The nearest approach to dichotomous branching is seen in the widest basal axes, but the branches produced are not absolutely equal in diameter. These main branches divide repeatedly in a monopodial fashion in which a main axis maintains its diameter while producing laterals of various types. Some of EXPLANATION OF PLATE 111 Figs. 1-10. Powysia bassettii. 1, part of holotype photographed using unilateral illumination showing corrugated appearance. Arrowed is the base of a tube projecting from the surface of the thallus, x 8. 2, area of thallus in which short lengths of carbonaceous tubes are visible, x 20. 3, note the short lateral branches, the one to the right comprising two tubes, abruptly truncated distally. Arrowed is a short theca-like projection, x 10(NMW. 72 39G. la). 4 and 5, outlines ofindividual tubes in ultimate branches, X 30. 6, part of petrified axis (?limonite) with bases of lateral tubes, x 10 (NMW. 72 39G. 2a). 7, petri- fied tubes, X 30 (NMW. 72 39G. 2a). 8, part of the distal region of the holotype showing truncated tips and short lateral branches composed of one or two tubes, x 10 (NMW. 72 39G. la). 9, wider axis in which several aligned tubes are visible, x 10 (NMW. 72 39G. 2a). 10, area of carbonized thallus show- ing bases of tubes (arrowed), x 20 (NMW. 72 39G. la). PLATE 111 EDWARDS, Silurian non-calcified alga 828 PALAEONTOLOGY, VOLUME 20 these act as main axes themselves and branch further. Others are narrow, of varying length and remain undivided (PI. Ill, fig. 3) while others divide just once or twice. Plate 1 1 1, fig. 8 illustrates the appearance of part of a fan-shaped cluster of ultimate branches. Note that in this region a slight increase in axis diameter may occur. It should be emphasized that this frond although lying alongside the main axis is not attached. Like the stipe, the widest basal branches possess a considerable thickness of carbonaceous residue and are longitudinally striated. Plate 1 10, fig. 1 shows a branch in which a prominent thicker central band is present. It is therefore concluded that the wider branches were cylindrical and not flattened in the original plant. Although the holotype itself gives the impression that the whole frond was planated, it seems likely that in at least the basal regions (where axes sometimes overlie each other at a branch- ing point) branching was in more than one plane. More problematical are the splayed out ultimate branches which may indeed have been flattened in life. Most of the evidence for the detailed internal structure of the plant comes from the narrower distal branches. While the wider ones have a striated surface, narrower branches present an irregular longitudinally corrugated appearance (PI. Ill, fig. 1) suggesting groups of intertwining tubes of some sort. Even where the carbonaceous residue has disappeared, the yellow to brown iron stained rock beneath bears the pronounced imprints of the tubes. Further information was obtained from carbona- ceous examples in less well preserved areas of thallus (PI. Ill, fig. 2) and from iron petrifactions, presumably casts of the original tubes or groups of tubes (PI. 1 1 1, fig. 6). A combination of these two preservation types is seen on the holotype where petrified brown tubes are scattered on the surface of a heavily carbonized portion of thallus. The tubes themselves are parallel sided, on average OT mm wide and have smooth featureless longitudinal walls. It is postulated that these must have been quite rigid to produce the impressions of individual tubes on the rock. The tubes are unbranched, at least for the two to three millimetres over which they can be traced. The frequent changes in depth of the intertwining tubes made it impossible to follow a single tube over any great distance. Individual tubes are occasionally sinuous. The majority are longitudinally aligned. Plate 111, fig. 6 shows the bases of presumably incompletely preserved tubes arising from a central bundle. In one case only a petrified U-shaped tube has been preserved (PI. Ill, fig. 7). It was impossible from these types of preserva- tions to determine whether or not the tubes consisted of rows of cells, i.e. were filamentous or were siphoneous. Specimen NMW. 72 39G. 2a and its counterpart are impression fossils on which very little organic material remains. This occurs as very fine longitudinally running black lines, marking the outlines (walls) of tubes on the various branches at the extremities of the frond (PI. Ill, figs. 4 and 5). These lines are also visible on the holo- type where the carbonaceous material has flaked off. Transverse lines are not present, nor are any indications of branching tubes. Here again the tubes could be traced for a maximum of only two millimetres. Tube diameter varies between 0-08 mm and 0- 1 5 mm (average 0- 1 1 mm). While the absence of transverse walls suggests a siphoneous rather than filamentous construction, it is possible that cross walls, if more delicate than longitudinal ones, were originally present but escaped preservation. Indeed as only comparatively short DIANNE EDWARDS: SILURIAN NON-CALCIFIED ALGA 829 lengths of tubes (up to 3 mm) are visible, it is also considered possible that the thallus consisted of filaments of very elongate cells. Whether or not the thallus contained other types of tissue in addition to these tubes cannot be determined. Detailed internal organization cannot be detected in the wider branches, where longitudinal striations presumably represent longitudinally aligned tubes of the kind described above. In the narrower branches it is possible to distinguish up to ten individual tubes aligned in parallel, but there is no evidence of any additional tissues (PI. 1 1 1, fig. 9). Many of the branches bear short theca-like (in the zoological sense) lateral pro- jections, usually seen in profile (PI. Ill, fig. 3). They often consist of just one tube, which ends abruptly close to the branch. Circular scars, of similar diameter to the tubes and present on the surface of some narrow branches, are thought to represent the bases of these short truncated projections (PI. Ill, fig. 10). Tubes are also visible in the individual lateral branches mentioned above. While up to three tubes occur at the base, there is a progressive reduction in number distally. Individual tubes are abruptly truncated and give a stepped appearance to the tip of the branch. Some of the terminal branches have a similar organization. Where tubes (up to four) are visible, they end abruptly. It is possible that more delicate areas of tissue were originally present beyond the tubes but these were not preserved. A few branches end in sheets of featureless carbonaceous residue, lacking any indication of tubes or of apical organization (PI. Ill, fig. 8). Habitat. The gross morphology of Powysia suggests a benthic alga, while its presence in graptolitic shales probably indicates a marine origin, although it must have been transported some distance from where it grew in shallow water. However, the possi- bility that it was a fresh water alga which was swept into the sea before burial cannot be ruled out. COMPARISONS Macroscopic non-calcified algae which are sufficiently well preserved to allow identification in terms of present-day taxa are rare in the early Palaeozoic. Indeed the early history of the group centres on calcified representatives and more recently, on microscopic algae preserved in cherts. Many of the identification problems in non- calcified algae result from lack of preserved anatomy and reproductive parts. Simi- larities in thallus form seen in various lines of extant algae serve as important reminders of the pitfalls of identification based on external morphology in compression fossils. Excellent examples of the necessary critical approach are found in Fry and Banks’s description of apparently complete and highly distinctive algae from the Upper Devonian of New York State (Fry and Banks 1955) and in Elliott’s taxonomic treat- ment of his new genus Inopinatella from the Upper Silurian of Britain (Elliott 1971). None of the algae described in these two papers sufficiently resemble the Welsh fossils to merit detailed comparisons, although two general points, relevant to any con- siderations on non-calcified algae, emerge. Firstly, there is Elliott’s comment that Inopinatella, a non-calcified alga, shows marked similarities with the juvenile stage of Neomeris an extant calcified genus, and secondly, as Fry and Banks point out, there is 830 PALAEONTOLOGY, VOLUME 20 a possibility that the calcium carbonate originally present in the plant has been subsequently leached out producing an apparently non-calcified fossil. It is concluded unlikely, however, that either possibility applies in the present study. The genus Buthotrephis Hall is widespread in Ordovician and Silurian strata. While it is outside the scope of this paper to discuss in detail the affinities of the numerous Buthotrephis species, it seems likely that a few are indeed non-calcified algae (Johnson et al. 1959). Two such examples are B. newlinii and B. divaricata described by White (1901) from the Silurian of Indiana. In both, the ‘/fragment of the thallus consists of regularly dichtomizing axes of uniform width and with rounded apices. Species distinction is based on axis width and frequency of branching. Another possible non- calcified alga B. nidarosiensis ( Hoeg 1941) shows less regular branching, and in common with the other two species shows none of the over-all morphological complexities of Powysia. I consider it possible that many Buthotrephis specimens were distal branch- ing fragments of much larger algae, perhaps with gross morphology similar to that in Powysia, although they are quite distinct from the distal branches of Powysia itself. White (1903) also described Thanmoeladus elarkei from the Upper Devonian of New York State, which he considered to be a non-calcified alga. It consists of an extensively branched thallus in which the regular branching is described as ‘alternately dichotomous’. Individual axes are flexuous, gradually tapering, and have a central line. Whether or not this highly distinctive plant is indeed vascular is being investigated by Dr. D. Grierson in the United States. Although the distal regions of Powysia as seen in the more complete specimens bear a superficial resemblance to T. elarkei, I conclude they are unrelated. It would be unwise to exclude the enigmatic Prototaxites Dawson from any discussion on non-vascular plants of this age. However, I know of no Prototaxites species of such elaborate morphological dilferentiation and two sizes of tube are not recorded for Powysia, although, of course, this could be due to preservation failure. AFFINITIES OF POWYSIA The possibility that Powy’sia was an animal cannot be ignored. It has long been appreciated that many of the fossils described as algae in the last century under such genera as Fueoides Brongniart are trace fossils (Seward 1898). Indeed many Butho- trephis species may belong in this category and Simpson ( 1 956) has assigned B. graeilis. Hall’s type species to Chondrites von Sternberg, a trace fossil genus considered to represent the branching burrowing system of a worm. In addition, remarkable morphological similarities exist between certain invertebrate fossils and plants (Chaloner and Allen 1970; Lundblad 1972). Ruedemann (1916) postulated graptolitic affinities for B. lesqueureuxii and renamed it Inoeaulis lesqueureuxi. Dr. B. Rickards has examined all the Powysia specimens and has confirmed that they are not dendroid graptolites. Geochemical analysis of carbonaceous residues from specimen NMW. 72 39G. lb by Dr. K. Niklas, New York Botanical Garden (pers. comm.) supports the plant nature of the fossils. The evidence presented above suggests that Powysia was an alga of marked morpho- logical complexity but with relatively simple internal organization, the thallus consisting of intertwining filaments or siphons. As discussed earlier the reliability of DIANNE EDWARDS: SILURIAN NON-CALCIFIED ALGA 831 the anatomical evidence is questionable: it is possible at least for the wider axes, that while tubes or filaments have been preserved, softer parenchymatous or pseudo- parenchymatous tissues have disappeared. A morphologically complex thallus of siphoneous construction characterizes members of the Siphonales (Chlorophyta). Indeed the complete Powysia plant resembles the upright and rhizoidal portions of members of the Caulerpaceae. Powysia, however, lacks ‘rhizomes’, regularity of branching, and the complexity of internal structure typical of Caulerpa and allied genera. These two latter features also exclude relationships with Codium a non-calcified, non-rhizomatous member of the Codiaceae. On the limited data available it is impossible to assign Powysia to any living family within the Siphonales. Filamentous organization of heterotrichous type, in which a basal prostrate system of filaments is accompanied by a system of upright branches, is present in many living algae. In the Chlorophyta, the heterotrichous habit is very well developed in the Chaetophorales, as in Stigeocloniimi. The majority of the Chaetophorales have erect branches consisting of a single filament with the highest degree of internal differentiation in certain species of Draparnaldia and Draparnaldiopsis where lateral branches produce rhizoid-like structures which completely invest the main axis in its basal region. Aggregation of filaments in mucilaginous envelopes are seen in certain species of Chaetophora itself. None of these species are morphologically similar to Powysia. Considered the simplest growth form in the brown algae, the heterotrichous habit is typical of the Ectocarpales. Powysia is best compared with those members in which erect branches consist of aggregations of filaments (multiaxial forms), but here again their internal organization is more complex than in the fossils because filaments are of varying size and orientation. Indeed some species have a pseudoparenchymatous organization in ultimate branches. Similar problems arise when Powysia is compared with heterotrichous multiaxial members of the red algae and so it is concluded that the combination of morphological and anatomical characteristics seen in Powysia is not represented in modern hetero- trichous forms in any of the major groups of macroscopic algae. Finally, there are some red and brown algae which resemble Powysia in habit and size, but which have highly elaborate internal differentiation. In the browns, for example, the extant fucoid Cystoseira is superficially like Powysia, although the fossil lacks any small swellings, while in the reds, similarities exist with tough branching forms such as Cystocloniiim. It is, of course, possible that the fossil alga exhibits a combination of characters unknown in present-day forms. I feel, therefore, that until further, better-preserved specimens are found, Powysia should be considered an alga of uncertain affinities. Acknowledgements. I thank Drs. G. Elliott and J. Price of the British Museum (Natural History) and Dr. Kathryn Benson-Evans (University College, Cardiff) for advice on living and fossil algae. I am grateful to Dr. M. G. Bassett for providing the specimens for study and for geological advice. 832 PALAEONTOLOGY, VOLUME 20 REFERENCES BAKER, J. w. and HUGHES, c. P. (In press). Field meeting in Central Wales, Summer 1973. Proc. Geol. Assoc. CHALONER, w. G. and ALLEN, K. 1970. Palaeobotany and phytochemical phylogeny. In j. b. harborne (ed.). Phytochemical Phylogeny, 21-30, 1 pi. Academic Press, London. CHURKIN, JR. M., EBERLEIN, G. D., HUEBER, E. M. and MAMAY, s. H. 1969. Lower Devonian land plants from graptolitic shale in south-eastern Alaska. Palaeontology, 12, 559-573, 2 pis. ELLIOTT, G. F. 1971. A new fossil alga from the English Silurian. Ibid. 14, 637-641, 2 pis. FRY, w. L. and BANKS, H. p. 1955. Three new genera of algae from the Upper Devonian of New York. J. Paleont. 29, 37-44, 2 pis. HOEG, o. A. 1941. Buthotrephis niclarosiensis n. sp. a non-calcified alga from the Lower Silurian of the Trondheim area. K. norske Vidensk. Selsk. Forh. 13, 187-190, 1 pi. JAEGER, H. 1967. Preliminary stratigraphical results from graptolite studies in the Upper Silurian and Lower Devonian of south-eastern Australia. J. Geol. Soc. Ansi. 14, 281-286. JOHNSON, J. H., KONiSHi, K. and REZAK, R. 1959. Studies of Silurian (Gotlandian) Algae. Colo. Sch. Mines Q. 54, 1-173. LANG, w. H. and COOKSON, I. c. 1935. On a flora, including vascular land plants, associated with Monograptus in rocks of Silurian age, from Victoria, Australia. Phil. Trans. R. Soc. Lond. B 224, 221-249, 4 pis. LUNDBLAD, B. 1972. A reconsideration of Psilophyton Ohedei Halle, Silurian of Gotland (Sweden). Rev. Palaeobot. Palynol. 14, 135-139, 1 pi. OBRHEL, J. 1962. Die Flora der Pridoli-Schichten (Budnany-Stufe) des mittelbomischen Silurs. Geologic, 5er/;>7, 11, 83-97, 2 pls. RUEDEMANN, R. 1916. Paleontologic contributions from the New York State Museum. Bull. N.Y. St. Mus. 189, 7-97, 36 pis. SEWARD, A. c. 1898. Fossil plants. Vol. I. Cambridge, pp. 1-452. SIMPSON, s. 1956. On the trace fossil Chondrites. Q. Jl geol. Soc. Lond. 112, 475-499, 4 pis. STRAW, s. H. 1953. The Silurian succession at Cwm Graig Dddu (Breconshire). Lpool Manchr geol. J. 1, WHITE, D. 1901. Two new species of algae of the genus Buthotrephis, from the Upper Silurian of Indiana. Proc. U.S. natn. Mus. 24, 265-270, 3 pis. 1 903. Description of a fossil alga from the Chemung of New York with remarks on the genus Haliserites Sternberg. Ann. Rep. N.Y. St. Mus. 55, 593-605. 208-219. Typescript received 21 June 1976 Revised typescript received 22 November 1976 DIANNE EDWARDS Department of Botany University College Cardiff CFl IXL A NEW ENTOPROCT-LIKE ORGANISM FROM THE BURGESS SHALE OF BRITISH COLUMBIA by S. CONWAY MORRIS Abstract. Dinomischus isolalus gen. et sp. nov. is described from the Burgess Shale (Middle Cambrian). A calyx, supported by a long slender stem, bears distally a circlet of elongate bracts which may have been used in filter feeding. Within the calyx a recurved gut with enlarged stomach is supported in a spacious body cavity by suspensory fibres. A sessile mode of life comparable to that of the modern pennatulacean Umhelliila (Cnidaria) is proposed. Certain similarities with other stalked animals, especially the Entoprocta, exist. The actual affinities of D. isolalus remain, however, uncertain. Although some 90% of the Burgess Shale fauna has received at least a preliminary description a number of animals, usually represented by only a few specimens, have remained undescribed. The present paper delineates one such new genus and species. Three specimens, all lacking their counterparts, of this new creature are known. One specimen has been located in the National Museum of Natural History (formerly the United States National Museum, USNM), Washington, D.C., and another in the Royal Ontario Museum (ROM), Toronto during searches through the collections of Burgess Shale material in these institutions. Dr. D. E. G. Briggs kindly drew the attention of the author to a third specimen in the Museum of Comparative Zoology (MCZ), Harvard. The USNM specimen had evidently been noted by C. D. Walcott, who discovered the Burgess Shale and described much of its fauna and flora, because a retouched photograph was found beside the specimen. However, neither Walcott nor any other worker has published any information on this animal. The history of excavation of the Burgess Shale and its stratigraphic setting were briefly reviewed by Conway Morris (1976t7). The USNM specimen is labelled 35k, which is that institution’s locality number for the Phyllopod bed exposed in the Burgess quarry (Walcott 1912). It was from this quarry that Walcott recovered, during several seasons (1910-1913, 1917) of collecting, the great majority of fossils with their soft parts preserved. No information on the stratigraphic position of this specimen within the 2-31 m (7 ft 7 in.) thick Phyllopod bed is available. Presumably the MCZ specimen was found by the Harvard team during their expedition to the Burgess Shale exposures in 1930 (Raymond 1935). Although fossil material was obtained from the Burgess quarry, they also collected a substantial number of specimens in a higher quarry (USNM locality 35k/ 10) which is situated some 19-8 m (65 ft) above the Burgess quarry. Walcott had recovered some fossils from this excavation which is generally known as Raymond’s quarry. The matrix surrounding the MCZ specimen is lithologically similar to the rocks exposed in Raymond’s quarry. The MCZ specimen may, therefore, have come from this higher horizon in the Burgess Shale. The ROM specimen was collected in 1975 from talus material which had been discarded from the two quarries by previous expeditions: more precise stratigraphic information is unavailable (D. Rudkin pers. comm.). [Palaeontology, Vol. 20, Part 4, 1977, pp. 833-845, pi. 112.] 834 PALAEONTOLOGY, VOLUME 20 A note on the photography and interpretation of the specimens. All three specimens have been photographed in ultra-violet light under a directional lamp using Panatomic-X film. Plate 1 12, figs. I, 3, 5, 6 were photographed in high-angle light. The lamp was inclined to the horizontal specimen at about 60°. The specimen was then tilted through about 10° towards the lamp until maximum reflectivity, as observed down the focusing tube, was obtained. Plate 112, figs. 2, 4 were photographed in low-angle light. The inclination of the lamp was about 30° and the specimen was placed as horizontal as possible. Focusing was undertaken in ordinary light. Camera-lucida drawings (text-fig. 2a, b) are placed opposite Plate 1 12 as a guide to the interpretation of figs. 1-5. SYSTEMATIC PALAEONTOLOGY Phylum UNCERTAIN Family dinomischidae fam. nov. Diagnosis. Long slender stem supporting calyx with distal circlet of bracts which apparently encloses both openings of the recurved gut. Genus dinomischus gen. nov. Type and only known species. Dinomischus isolatus sp. nov. Derivation of name. The generic name is derived from Dinos (Greek— goblet) and Mischos (Greek— stalk or stem) and refers to the similarity to a hock glass. Diagnosis. Sessile non-colonial metazoan. Body consists of calyx supported by elongate stem. Calyx bears about twenty elongate bracts which project distally. Calyx otherwise smooth, without plates or spines. Gut recurved with prominent saccular stomach supported in body cavity by suspensory fibres. Stem enlarged immediately beneath calyx, otherwise straight and slender, terminating in slightly swollen holdfast. Dinomischus isolatus sp. nov. Plate 112; text-fig. 2a, b Derivation of name, isolatus (NL) refers to the non-colonial nature of the animal. Diagnosis. As for the genus. Holotype. USNM 198735 from the Stephen Eormation (Middle Cambrian), Burgess Shale member ( Pagetia hootes faunule of the Bathyuriscus-Elrathma Zone : Eritz 1971), Eield, southern British Columbia. Paratypes. MCZ 1083, ROM 32573. Preservation. The specimens are preserved as very thin films in the same manner as the majority of Burgess Shale species (Whittington 1971n, b, 1974, 1975«, b; Hughes 1975). The films, which have a siliceous composition (Conway Morris 1977), are in part darker than the surrounding rock matrix, but certain features such as the gut, suspensory fibres, and stem are preserved as reflective areas. The specimens are isolated on small slabs and none is associated with any other identifiable fossils. The preservation of the USNM specimen is superior to the others and features of internal anatomy are comparatively clear. This variation in preservational quality may be largely ascribed to the amount of decay that occurred prior to fossilization. CONWAY MORRIS: DINOMfSCHUS FROM THE BURGESS SHALE 835 Morphology. The probable appearance of the animal is shown in text-fig. 1 , which is drawn in the style of a partial dissection. The body can be divided into a calyx and slender stem. Dimensions of the principal parts of the body are given in Table 1. In the ensuing discussion the stem is assumed to have supported the calyx above the sea- floor. Thus upper and distal, and lower and proximal are taken to be synonymous. The terms dorsal and ventral are not used because of the impossibility of determining which side was in fact directed towards the sea-floor. The entoprocts, for instance, are attached to the stalk on what is morphologically their dorsal side (Harmer 1886). TABLE 1 . Dimensions of various parts of the body of Dinomischus isokitus gen. et sp. nov. All readings in mm. Feature USNM 198735 MCZ 1083 ROM 32573 Length of calyx up to base of bracts 54 3-8 4-8 Length of bracts 4-5 2-7 4-2 Width of bracts 0-7 0-6 0-6 Length of upper stem 2-8 c. 14 c. 2 Length of lower stem 5-1 + 12 16-5 i Width of lower stem 0-5 0-3 04 Length : width of lower stem 10-2 + 40 41-2 Length of basal holdfast — 2 — Width of basal holdfast — 0-7 — The over-all shape of the calyx was a rounded cone. It is assumed that the roof of the calyx was flat (text-flg. 1). Slight variations in calyx shape have, however, been noted. In the MCZ specimen the calyx increases in width noticeably towards the distal end (PI. 1 12, figs. 3, 4; text-fig. 2b), whereas in the ROM specimen it is narrower and the sides diverge only slightly (PI. 112, fig. 6). The calyx of the USNM specimen appears to represent an intermediate case (PI. 1 12, figs. 1,2; text -fig. 2a). This varia- tion may be a reflection of the calyx being originally laterally compressed so that its cross-section was elliptical. Alternatively, the walls of the calyx may have been sufficiently pliable to allow the calyx shape to be controlled by muscular contraction. With this latter alternative in mind it may not be coincidental that in the narrow ROM specimen the calyx bracts (see below) are clustered together (PI. 112, fig. 6), while in the broad MCZ specimen the braets diverge from one another (PI. 112, figs. 3, 4; text-fig. 2b). The calyx bore prominent plate-like structures, termed here the calyx bracts, which arose from about two-thirds above its base. They appear to have been rather rigid and were probably thin and plate-like. They are not, therefore, considered to have been true flexible tentacles. The bracts were elongate, with smooth edges and pointed distal terminations (PI. 112, figs. 1-4, 6; text-fig. 2a, b). In the USNM speeimen the distal left-hand edge of some of the bracts is deflected inwards so giving them an asymmetrical appearance (PI. 1 12, figs. 1, 2; text-fig. 2a). This feature may be due to partial deeay and is not regarded as original. The distal extension of the gut past the insertion points of the bracts (PI. 1 12, fig. 1 ; text-fig. 2a) indicates that they probably mantled the upper part of the calyx, although it is impossible to determine whether the inner surfaces of the bracts were firmly attached to the outer wall of the calyx. Distally the bracts projected beyond the calyx (text-fig. 1). Nine bracts have been noted in the USNM specimen. It is believed that they represent the complement 836 PALAEONTOLOGY, VOLUME 20 HdFs i \ I mm CONWAY MORRIS: DINOMISCHUS FROM THE BURGESS SHALE 837 of one side of the animal so that the total was about twenty. The bracts apparently encircled the calyx and there is no evidence of any interruption or gap. The overlap (PI. 112, figs. 1, 2; text-fig. 2a) and separation (PI. 112, figs. 3, 4; text-fig. 2b) of adjacent bracts demonstrates that they were not fused into a single collar-like structure. There is no clear evidence that the bracts were connected by a membranous structure and it is probable that each bract was separately inserted on to the calyx wall. Below the insertion line of the bracts the calyx was smooth and lacked spines, plates, or other ornamentation. Features of the internal anatomy of the calyx are comparatively well preserved in the USNM specimen. The upper calyx is occupied by a reflective mass whose shape can be resolved into a U with a greatly thickened base (PI. 112, fig. 1; text-fig. 2a). This feature is interpreted as a recurved gut. The two vertical limbs of the U, taken to be extensions of the gut, appear to have been simple tubes. They are regarded here as the oesophagus and intestine which opened on the roof of the calyx at the mouth and anus respectively (text-fig. 1). The more median branch of the gut is taken to be the oesophagus (PI. 1 12, fig. 1 ; text-fig. 2a), because it is reasonable to imagine the mouth in a more central position so as to accept food from all sides. The eccentric branch that ran close to the edge of the calyx is taken to be the intestine (PI. 112, fig. 1 ; text-fig. 2a). The anus would thus have been situated near the margin of the animal to avoid fouling (text-fig. 1). Adjacent to the anus the bracts may have been absent, reduced, or more widely spaced to facilitate dispersal of waste matter. No direct evidence is, however, available. The centrally positioned mass (i.e. the thickened closure of the U : PI. 112, fig. 1 ; text-fig. 2a) is interpreted as the stomach (text-fig. 1). On the basis of slight variation in the reflectivity of the fossil film the stomach may be divided into a narrow upper region and a larger lower unit which narrowed proximally to a square-shaped termina- tion. This lower region is regarded as a sac-like extension of the stomach. The more diffuse reflective areas in the upper calyx of the other specimens are also interpreted as poorly preserved remnants of the gut (PI. 1 12, figs. 3, 6; text-fig. 2b). The space between the gut and the edges of the calyx is traversed by about fifteen reflective strands that radiate from the lower stomach (PI. 112, fig. 1; text-fig. 2a). The arrangement of these strands suggests that they were suspensory fibres or muscles which helped to support the stomach (text-fig. 1). Their distribution does not uphold the idea that they were either body-wall or retractor muscles. Their presence strongly suggests that the gut was suspended in a fluid-filled body cavity. Immediately beneath the proximal extension of the stomach the lower calyx is preserved as a reflective film. The upper margin of this film is highly irregular and is distinctly more reflective than the remainder of the lower calyx (PI. 1 12, fig. 1 ; text- fig. 2a). The significance of the reflective preservation within the lower calyx is TEXT-FIG. 1, Reconstruction of appearance of Dinoniischus isolatiis gen. et sp, nov. A portion of the upper calyx and bracts has been cut away to reveal internal details. The groove separating the upper calyx wall from the bracts is hypothetical. Most of the lower stem has been omitted. The holdfast is inflated to its maximum size. An., anus; Bd. Cav., body cavity; Br., bract; Ca., calyx; Hd. Fs., holdfast; Int., intestine; Lr. So., lower stomach; Lr. St., lower stem; M., mouth; Oes., oesophagus; Sus. Fb., suspensory fibres; Up. So., upper stomach; Up. St., upper stem. Br. TEXT-FIG. 2. Camera-lucida drawings. Lines with hachures indicate definite breaks in slope, the hachures being directed downslope. a, USNM 198735. b, MCZ 1083. So., stomach. See text-fig. 1 for other abbreviations. EXPLANATION OF PLATE 112 Figs. 1-6. Dinomischus isolatiis gen. et sp. nov. USNM 198735 (holotype), figs. 1-2; MCZ 1083 (paratype), figs. 3-5; ROM 32573 (paratype), fig. 6. All photographs taken under ultra-violet light. 1, high-angle light from east, X 4. 2, low-angle light from east, x 4. 3, high-angle light from south-west, x 6. 4, low- angle light from south-east, x 6. 5, enlargement of proximal holdfast, high-angle light from north-east, X 16. 6, high-angle light from north-west, x 6. PLATE 112 CONWAY MORRIS, Dinomischus 840 PALAEONTOLOGY, VOLUME 20 uncertain. It could, for example, represent body-wall muscles or even reproductive organs. It is not known whether the body cavity extended into this part of the calyx. The stem was attached to the undersurface of the calyx (PI. 112, figs. 3, 4; text- fig. 2b), presumably in its centre. It can be divided into three sections; a short upper section, a lower slender section, and a proximal holdfast. The width of the upper stem increased distally, but it was demarcated from the calyx by a distinct change in width (PI. 1 12, figs. 1, 2, 6; text-figs. 1, 2a). Its union with the rest of the stem was, however, less abrupt (PI. 112, figs. 1, 2, 6; text-figs. 1, 2a). The upper and lower stem are preserved as a uniform reflective film. This similarity in preservation indicates that it would be incorrect to take the upper stem as a proximal extension of the calyx. The lower stem is remarkable for its length, straightness, and slender proportions as compared with the size of the calyx it supported (PI. 1 12, figs. 3, 4, 6; text-fig. 2b). It was of more or less constant width and probably had a circular cross-section. The surface of the lower stem appears to have been smooth. No internal structures such as supporting skeletal tissue or canals are preserved. The basal stem consisted of a slightly swollen holdfast which lacked rhizoids or additional attachment devices (PI. 112, fig. 5; text-fig. 2b). DISCUSSION Mode of life. Recent work (Whittington 1971a, b, 1974, 1975a, b; Hughes 1975; Conway Morris 1976/?) on other members of the Burgess Shale fauna has shown that features such as the variable orientation of specimens with respect to the bedding plane and the separation of appendages by sediment are best explained by transport and burial in mudflows which probably did not extend very far above the sea-bed. It has become clear that the majority of Burgess Shale species suffered this burial history and must, therefore, have been benthonic. The specimens of D. isolatus are preserved parallel to the bedding plane and do not show any evidence as to their taphonomy, unless the imbrication of the bracts of the USNM specimen (PI. 1 12, figs. 1,2; text- fig. 2a) is ascribed to the effects of transport in a mudflow. However, the elongate stem with holdfast was presumably used to support the calyx and this strongly suggests that D. isolatus was a member of the sessile benthos. It is most probable that D. isolatus either lived on the muds that slumped into the area where the Phyllopod bed was being deposited or was overwhelmed by mudflows descending from further upslope. The scarcity of this creature and its apparently isolated occurrence might suggest that it was not gregarious and its original distribu- tion over the sea-floor was very sparse. Alternatively, the rarity of D. isolatus may be due to infrequent disturbance by the mudflows. The Phyllopod bed was deposited in deep water close to a prominent carbonate bank (Fritz 1971). D. isolatus might have lived on parts of the bank, such as a basal apron, which generally remained clear of basinal mudflows. On first consideration the length to width ratio of the stem (Table 1) appears to be high in relation to the size of the calyx. It is possible that the stem was deeply embedded in the sediment. The functional advantage of a largely buried slender stem over a thicker and shorter stalk is, however, difficult to imagine. As is discussed below several phyla have representatives with attenuated attachment devices that serve to CONWAY MORRIS: DINOMISCHUS FROM THE BURGESS SHALE 841 keep the animal clear of the sea-floor. It is, therefore, suggested that most of the stem was free of the sediment. The exact depth of penetration might have depended to some extent on its rigidity, but it should be remembered that the sea-water would have counterbalanced most of the calyx weight. The straightness of the stem (PI. 112, figs. 3, 4, 6; text-fig. 2b) indicates that it was rather inflexible, although this may be a post-mortem effect. Rigidity of the stem may have been produced by supporting tissue, such as a collagenous or chitinous endoskeleton, or turgor pressure derived from an internal canal. These two mechanisms need not have been mutually exclusive and may have complemented one another. As noted above there is, however, no direct evidence of any skeletal support. The action D. isolatus took to avoid being scoured out by strong currents or overwhelmed with sediment is conjectural. The holdfast, or even the stem, may have been sufficiently muscular to drag the animal upwards or downwards. Although a number of animals support the body on a slender stalk of varying flexibility, the mode of attachment of D. isolatus would seem to have its closest analogue in the modern deep-sea UmbeUula {Crndd^xidi: Pennatulacea) (Kolliker 1880; Hickson 1916; Broch 1958). In this sea-pen a rosette of large feeding polyps or auto- zooids is supported by a long slender stalk or peduncle which is embedded in soft sediments with the aid of a muscular bulb. As in D. isolatus the terminal bulb lacks additional attachment devices such as rhizoids. The peduncle can be up to 1 m long and is supported by water-filled gastrovascular canals and a skeletal axis, which in Urnbellula is variably calcified (Broch 1958). Although the peduncle is flexible it can achieve sufficient rigidity to keep the autozooids well clear of the sediment (Jahn 1970, fig. 2; Menzies et al. 1973, figs. 5-25, 5-266, 7- 15c). It is proposed that the calyx bracts were involved in feeding. As is stated below there is no evidence that the animal possesses a tentacular feeding device, and D. isolatus does not appear to have any other organ more suitable for collecting food. As is noted above the bracts are not considered to be genuine tentacles. The rigidity of the bracts indicates that they were unable to enfold or grasp prey, and it is more probable that they were ciliated so that food was swept, perhaps with the aid of mucous secretions, to the mouth. D. isolatus is, therefore, regarded as a microphagous suspension feeder. The feeding position may be represented when the bracts are spread outwards (PI. 112, figs. 3, 4; text-fig. 2b). The observation that the bracts originate at points rather low on the sides of the calyx is difficult to explain if their proposed use as food collectors is correct. One possibility is that a deep, perhaps ciliated, gutter or groove separated the bracts from the calyx (text-fig. 1 ). Alternatively, only the distal part of the bracts may have been involved in feeding. Ciliary currents may have also dispersed faeces. Zoological affinities. A number of phyla or groups within a phylum have adopted the groundplan of a body, generally cup-like, supported by an elongate stem. Examples may be found in the sponges, cnidaria, tunicates, echinoderms, and entoprocts. D. isolatus has at least superficial similarities to these groups as well as the ectoprocts, but important differences remain. 1. Stalked sponges such as Hyalonema (Laubenfels 1955) have a much simpler organization than D. isolatus and no realistic comparison is possible. The similarity 842 PALAEONTOLOGY, VOLUME 20 to Stalked cnidarians such as the Hydroida, Stauromedusae, and Pennatulacea, e.g. Umbellula would also appear to be purely superficial. The presence of a recurved gut with separate mouth and anus is clearly more advanced than the body plan of the Cnidaria. 2. Similarly, no close resemblance can be demonstrated between D. isolatus and stalked tunicates such as Boltenia and Culeolus (Herdman 1882). 3. A number of Middle Cambrian echinoderms possess either variously developed aboral extensions of the calyx termed holdfasts or else true stems (Sprinkle 1973). They are represented by the eocrinoids, e.g. Akadocrimis, Gogia, and the earliest known crinozoan (?crinoid), Echmatocriims brachiatus, which is also from the Burgess Shale (Sprinkle 1973). Comparisons show that no genuine affinity exists between these echinoderms and D. isolatus. A major difference is the absence of calcareous plates and ossicles in the calyx and stem. 4. A closer comparison is, however, possible with the Entoprocta and Ectoprocta (or Bryozoa). A number of workers believe that entoprocts and ectoprocts have developed different grades of organization from a common, but distant, proto- stomatous ancestor (Brien and Papyn 1954; Hyman 1959). Opinion differs, however, as to the exact degree of affinity between the two groups. Some authors have suggested that there are sufficient similarities to place the entoprocts in the Bryozoa (Marcus 1939; Nielsen 1971). The majority of workers are more impressed by the numerous differences between the entoprocts and ectoprocts (Atkins 1932; Hyman 1951 ; Brien 1960, 1970; Brien and Papyn 1954), and the former group is now usually placed in a phylum of its own. The entoprocts are a minor marine and freshwater group of small (seldom above 5 mm long) animals. The solitary Loxosomatidae are regarded as the most primitive family (Hyman 1951; Brien 1960), whilst the Pedicellinidae and Urnatellidae are believed to represent successively more evolved families that became colonial. The more recently described Loxokalypodidae (Emschermann 1972) may represent a group intermediate between the Loxosomatidae and the latter two families. Helpful accounts of entoproct morphology are available in Hyman (1951) and Mariscal (1965). The bilaterally symmetrical body consists of a slightly laterally compressed calyx supported by a stalk. The calyx bears a circle of ciliated tentacles. In the solitary loxosomatids the stalk is attached to the substrate by an adhesive disc. The stalk of the colonial entoprocts, however, often has a swollen muscular attachment to the stolon. The gut is recurved with both the mouth and anus opening within the circle of tentacles. The body cavity, which extends into the tentacles, is a pseudocoel that is filled with a gelatinous substance containing mesenchyme cells. D. isolatus has superficially, at least, a certain resemblance to an individual ento- proct : both groups being characterized by a calyx, stem, and recurved gut. Neverthe- less there are some differences. The individual entoproct is over five times smaller than D. isolatus. The calyx bracts do not appear to be true tentacles, although like those of an entoproct they apparently encircled both mouth and anus. The ancestral entoproct conceivably had a fluid-filled pseudocoel, but extensive development of mesenteries and suspensory fibres is not typical of other pseudocoelomate animals. In some entoprocts fibres run from the calyx wall to the mouth and oesophagus, but the rest of the gut receives no such attachment. It is concluded that the similarities CONWAY MORRIS: DINOMISCHUS FROM THE BURGESS SHALE 843 may indicate that some degree of affinity, albeit distant, exists between D. isolatus and the entoprocts. One possibility is that present-day entoprocts are miniaturized descendants of a dinomischid-like creature. 5. The ectoprocts are always colonial and the individual animals (zooids) are usually eneased in a tough exoskeleton. Useful summaries of this group are given by Hyman (1959) and Ryland (1970). A typical unmodified autozooid of the eolony bears a horseshoe-shaped or eircular ring of tentacles, the lophophore, which embraces the mouth. As the gut is strongly recurved the anus opens close to the lophophore. The lophophoral tentaeles arise from an introvert-like strueture which when with- drawn by the retraetor muscles forms the tentacle sheath. The body eavity is regarded as a true coelom. D. isolatus has certain similarities to an individual autozooid. The saecate nature of the stomach has a parallel in the ectoproct caecum which forms a prominent extension of the stomach. The caecum is attached to the zooid base by a strand of tissue— the funieulus. The trunk coelom is sometimes traversed by peritoneal strands and muscle fibres, but an exact parallel to the suspensory fibres of D. isolatus does not appear to exist. The calyx bracts cannot be directly compared with the lophophore. The anus of D. isolatus appears to have opened within the circle of bracts and it is very unlikely that they were deflected around the anus to give a horseshoe shape. In a few ectoprocts, e.g. Bowerhankia (Ctenostomata) the proximal tentacle sheath is surrounded by a eollar which pleats upon retraction of the tentaeles and might then superficially resemble the circlet of calyx bracts. Even were it assumed that the braets are equivalent to the collar, there is no evidence for a tentacular organ in D. isolatus that might be compared with the lophophore. In over-all appearance the autozooids show a less striking resemblance to D. isolatus than do the entoprocts. In particular the autozooids always lack a stem, even when they have separate insertions on the stolon. The autozooids are, moreover, about ten times smaller than the individuals of D. isolatus. It may, therefore, be concluded that no actual affinity exists between D. isolatus and the ectoprocts. Farmer et al. (1973) suggested that the ancestral eetoproct was a solitary phoronid- like creature which underwent simplification and a marked reduction in size when it adopted a colonial way of life. D. isolatus evidently differs in too many features to be even eonsidered as an ancestral ectoproct. 6. A comparable example deserving examination is Escumasia roryi Nitecki and Solem, 1973. This curious animal is characterized by a flattened sac-like body with two distal tentacles situated either side of the mouth. The body was supported by a slender stem that had a proximal attachment disc. The gut was apparently large and the anus was situated on the side of the body. Nitecki and Solem (1973) were unable to assign this animal to any known phylum, although they made certain comparisons with the Cnidaria. No close affinity exists between this creature and D. isolatus. Although the phyletic position of D. isolatus remains unresolved, the author believes that the closest affinities of this creature may possibly lie with the entoprocts. However, descriptions of other animals from the Burgess Shale (Whittington 1975u; Conway Morris 1976a, b, 1977) as well as from younger Palaeozoic rocks (Johnson and Richardson 1969; Davis and Semken 1975) are a useful reminder that not all fossils can be direetly accommodated in extant phyla. 844 PALAEONTOLOGY, VOLUME 20 Acknowledgements. I am very grateful to Professor H. B. Whittington and Dr. S. C. Matthews (Bristol) for careful criticism of the manuscript and for suggesting improvements. Dr. R. Grant, Mr. F. Collier (National Museum of Natural History, Washington, D.C.), Professor B. Kummel, Miss V. Kohler (Museum of Comparative Zoology, Harvard), Dr. D. Collins, and Mr. D. Rudkin (Royal Ontario Museum, Toronto) made available every facility during my visits to their respective institutions. They also readily arranged the loans of the specimens. This work has been undertaken whilst a research fellow of St. John’s College, Cambridge. REFERENCES ATKINS, D. 1932. The ciliary feeding mechanism of the entoproct polyzoa, and a comparison with that of the ectoproct polyzoa. Q. JI microsc. Sci. 75, 393-423. BRiEN, p. 1960. Le bourgeonnement et la phylogenese des Endoproctes et des Ectoproctes. Reflexions sur les processus de revolution animate. Bull. Acad. r. Belg. Cl. Sci. 46, 748-766. — 1970. Considerations phylogenetiques a propos des Lophophoriens. Ibid. 56, 565-579. and PAPYN, L. 1954. Les endoproctes et la classe des bryozoaires. Annls Soc. r. zool. Belg. 85, 59-87. BROCH, H. 1958. Octocorals. Part I. Pennatularians. "Discovery Rep. 29, 245-280. CONWAY MORRIS, s. 1976«. A iiew Cambrian lophophorate from the Burgess Shale of British Columbia. Palaeontology, 19, 199-222. \916b. Worms of the Burgess Shale, middle Cambrian, Canada. Unpublished Ph.D. thesis. Cambridge University. 1977. A new metazoan from the Cambrian Burgess Shale of British Columbia. Palaeontology , 20, 623-640. DAVIS, R. A. and semken, h. a. 1975. Fossils of uncertain affinity from the Upper Devonian of Iowa. Science, N.Y. 187, 251-254. EMSCHERMANN. p. 1972. Loxokalvpus socialis gen. et sp. nov. (Kamptozoa, Loxokalypodidae fam. nov.), ein neuer Kamptozoentyp aus dem ndrdlichen Pazifischen Ozean. Ein Vorschlag zur Neufassung der Kamptozoensystematik. Marine Biol. 12, 237-254. FARMER, J. D., VALENTINE, J. w. and cowEN, R. 1973. Adaptive strategies leading to the ectoproct ground- plan. Syst. Zool. 22, 233-239. FRITZ, w. H. 1971, Geological setting of the Burgess Shale. In Extraordinary fossils. Symp. North Amer. Paleont. Conv. 1969, Pt. I, 1155-1 170. HARMER, s. F. 1886. Oil the life-history of Pedicellina. Q. Jl microsc. Sci. 27, 239-263. HERDMAN, w. A. 1882. Report on the Tunicata collected during the voyage of H.M.S. Challenger during the years 1873-1876. Challenger Exped. Rep. 6, Pt. 17, HICKSON, s. J. 1916. The Pennatulacea of the Siboga expedition with a general survey of the order. Siboga Exped. Monograph 14, 1-265. HUGHES, c. p. 1975. Redescription of Burgessia hella from the Middle Cambrian Burgess Shale, British Columbia. Eossils and Strata, 4, 415-435. HYMAN, L. H. 1951 . The Invertebrates : Acanthocephala, Aschelminthes, and Entoprocta. The p.seudocoelomate Bilateria. Vol. III. McGraw-Hill, New York. 572 pp. 1959. The Invertebrates : Smaller coelomate groups. Vol. V. McGraw-Hill, New York. 783 pp. JAHN, w. 1970. Umbellulidae distribution extended in the Atlantic. Nature, Land. 225, 1068-1069. JOHNSON, R. G. and RICHARDSON, E. s. 1969. Peimsylvaiiian invertebrates of the Mazon Creek area, Illinois: The morphology and affinities of Tullimonstrwn. Eieldkma, Geol. 12, 8. KOLLIKER, A. v. 1880. Report on the Pennatulida dredged by H.M.S. Challenger during the years 1873- 1876. Challenger Exped. Rep. 1, Pt. 2. LAUBENFELS, M. w. DE. 1955. Porifera. In moore, r. c. (ed.). Treatise on invertebrate paleontology, E(Archaeo- cyatha and Porifera), E21-E1 12. MARCUS, E. 1939. Bryozoarios Marinhos Brasileiros-III. Bohn Eac. Eilos. Cienc. Univ. Sdo Paulo, Zoologia, 3, 111-299, MARISCAL, R. N. 1965. The adult and larval morphology and life history of the entoproct Barentsia gracilis (M. Sars, 1835). J. Morph. 116, 311-338. CONWAY MORRIS: DINOMISCHUS FROM THE BURGESS SHALE 845 MENZIES, R. J., GEORGE, R. Y. and ROWE, G. T. 1973. Ahysscil environment and ecology of the work! oceans. Wiley-Interscience, New York. 488 pp. NIELSEN, c. 1971. Entoproct life-cycles and the entoproct/ectoproct relationship. Ophelia, 9, 209-341. NiTECKi, M. H. and SOLEM, A. 1973. A problematic organism from the Mazon Creek (Pennsylvanian) of Illinois. J. Paleont. 47, 903-907. RAYMOND, p. E. 1935. LeanclioiUa and other Mid-Cambrian Arthropoda. Bull. Mas. comp. Zool. Harv. 76, 205-230. RYLAND, J. s. 1970. Bryozoans. Hutchinson University Library, London. 175 pp. SPRINKLE, J. 1973. Morphology and evolution of blastozoan echinoderms. Spec. Pubis Mas. comp. zool. Harv. Univ. 283 pp. WALCOTT, c. D. 1912. Middle Cambrian Branchiopoda, Malacostraca, Trilobita and Merostomata. Cambrian geology and paleontology, II. Smithson, misc. Colins, 57, 145-228. WHITTINGTON, H. B. I971u. The Burgess Shale: History of research and preservation of fossils. In Extra- ordinary fossils. Symp. North Amer. Paleont. Conv. 1969, Pt. I, 1 170-1201. \91\h. Redescription of Marrella splendens (Trilobitoidea) from the Burgess Shale, Middle Cambrian, British Columbia. Bull. geol. Surv. Can. 209, 1-24. 1974. Yohoia Walcott and Plenocaris n. gen., arthropods from the Burgess Shale, Middle Cambrian, British Columbia. Ibid. 231, 1-27. 1975u. The enigmatic animal Opabinia regalis. Middle Cambrian, Burgess Shale, British Columbia. Phil. Trans. R. Soc. Ser. B, 271, 1-43. \915b. Trilobites with appendages from the Middle Cambrian, Burgess Shale, British Columbia. Fossils and Strata, 4, 97-136. S. CONWAY MORRIS Department of Geology Sedgwick Museum University of Cambridge CB2 3EQ Typescript received 21 September 1976 Revised typescript received 3 November 1976 I 1 I ■I .t ■■■%;■ , .:/\isri2!U^ u THE SILURIAN TRILOBITE ENCRINURUS VARIOLARIS AND ALLIED SPECIES, WITH NOTES ON FRAMMIA by R. P. TRIPP, J. T. TEMPLE, and K. C. GASS Abstract. Encrinurus variolahs (Brongniart) from the Wenlock of the Welsh Borderland is redescribed and related species discussed. Of these, E. diaholus from the Llandovery of Shropshire and E. rosensteinae from the Ludlow of the Welsh Borderland are new. The genus Frammia is restricted to F. arciica (Salter) and F. rossica (Maksimova). Reed (1928, p. 66) subdivided the genus Encriminis into several species-groups, one of which was characterized by E. variokiris (Brongniart). Preliminary results of a numerical taxonomic study of encrinurines (currently in progress by Temple and Tripp) reveal no clear-cut species-groups among Silurian species of Encrinurus. A variolaris species-group is therefore not recognized in the present paper. Terminology. Miller (1976, pp. 341-343) has distinguished domes (in which the cuticle thickness is reduced towards the apex of the bulge), tubercles (small discrete structures with the appearance of pustular organelles embedded in the cuticle), and pseudotubercles (pustular structures which lack this discrete appearance). Many, but not all, of the raised features of encrinurines are domes (Miller 1976, text-fig. 2g). In this paper the term tubercle is used in its conventional general sense. The notation for glabellar tubercles is that proposed by Tripp (1957, 1962), except that the abaxial tubercles in rows II and III are referred to as 2L and 3L (see p. 848). The area underlying the tips of the pleural ribs of the encrinurine pygidium is here, following Whittington and Campbell (1967, p. 471) and Temple (1970, p. 67), referred to as the border; the pygidial doublure is reflexed dorsally and is normally not seen in ventral view. Proportions of various parts of the exoskeleton refer to specimens at least 5 mm long, and are quoted as percentages rounded to the nearest 5%. Except where stated to the contrary, the orientations of isolated parts of the exoskeleton in the photographs are those proposed as standard at Oslo (see Temple 1975), i.e. at right angles to horizontal planes defined by the sagittal lengths of cranidium, hypostome, and pygidium. A list of localities and registered specimen numbers has been deposited with, and may be purchased from, the British Library, Boston Spa, Yorkshire LS23 7BQ, Great Britain, as Supplementary Publication No. SUP 14008 (7 pages). TUBERCULATION Glabella. The glabellar tubereulation of the speeies deseribed is charaeterized by four main features; 1. The common presence of tubercle pair I-l. The presence of pair I-l is a major point of difference from many of the species related to E. punctatus (Wahlenberg), in which the most posterior glal3ellar tubercles are either the pair I I-l or the single small tubercle I-O (Tripp 1962, text-hg. 1). 2. The forward position of tubercle pairs I-l and II- 1. In E. cf. mullochensis of Temple (1970, p. 66, pi. 19, figs. 1-2) from the early Llandovery and E. schmidti Mannil (1968, p. 273, pis. 1-2) from the upper Llandovery, tubercle pair II- 1 lies on [Palaeontology. Vol. 2(1. Part 4. 1977. pp. 847-867. pis. 113-115.] 848 PALAEONTOLOGY, VOLUME 20 or close to the shortest arc joining 2L across the glabella, and tubercle pair I-l lies far behind this are. In the species described here both the I-l and II-l pairs are situated further forwards, so that pair I-l often lies closer to the arc joining 2L than does pair II- 1. 3. Development of glabellar lobes 2L and 3L. These form nodular tubercles which are usually large in diameter and low in profile compared with the adaxial glabellar tubercles. This feature, which is dilficult to objectify, is another distinction from E. pimctatus and its allies, in which 2L and 3L are more like the adaxial glabellar tubercles in diameter and profile (and thus possibly in function too). 4. The tendency of tubercles III-2 (when present) to lie close to 3L. III-2 and 3L often share a eommon base, especially in E. rosensteinae (PI. 115, figs. 4, 5). This feature is probably related to the less tubercle-like nature of 2L and 3L eompared with E. pimctatus and its allies, for in the latter III-2 does not usually encroaeh on to 3L. The number of tubercles on the posterior part of the glabella of a sample of BM specimens of E. variolaris (Table 1) increases during growth, declining again, possibly significantly, in the largest specimens (0-01 > o o o TEXT-FIG. II. Critical velocities at which scour began for each of three elevations of the posterior tip of Neotrigouia models above the surface of fine sand. Symbols as in text-fig. 10. The Carina represents the trace of a minor deflection of the shell margin. The carinas of the two valves are offset so as to interlock at the margin, and perhaps aided in valve alignment at closure. The area dorsal to the carina is smooth or granulated in most species. The granulation (PI. 1 17, flg. 9) may have served to camouflage an animal by trapping a thin layer of sediment when the surface of the shell was exposed. At any rate, the posterior dorsal region lacks pronounced ribs or spines of the sort found in certain cardiids. (PI. 118, flg. 1). The reason may be that the trigoniids’ lack of mantle fusion and discrete siphons required that the posterior mantle margins remain mobile to control water flow. Formation of permanent siphons in the Cardiidae may have freed the mantle lobes adjacent to the shell for secretion of more elaborate spines and ribs. STANLEY: COADAPTATION IN TRIGONIID BIVALVES 895 INTERPRETATION OE EVOLUTIONARY HISTORY To summarize the foregoing analysis, the Trigoniidae, whieh seem to display a varied collection of bizarre morphological features, actually exhibit a remarkable degree of coadaptation, illustrating in an impressive way Cuvier’s Principle of Correlation, or the tendency of arrays of morphologic features to operate in concert, or at least with compatability, fitting a taxon to a particular mode of life. Thus, evolution of the remarkable muscular foot, which was the adaptive breakthrough leading to the Mesozoic radiation of the trigoniids, required wide gaping of the valves, which led to the evolution of large, complex hinge teeth. The foot gave trigoniids the capacity to occupy shifting substrata on a large scale. Rapid burrowing would have been aided by the evolution of a prosogyrous shape, but this was apparently precluded by the early evolution of the huge central hinge teeth, the myophorous buttress required for support of the teeth, and the adductor muscle attached to the buttress. As an alterna- tive to the prosogyrous shape, which is a common feature of other bivalve families, discordant patterns of ornamentation evolved to grip the sediment. Here, then, we have a chain of coadaptive relationships. Partial adaptive analogy between the Trigoniidae and the Cardiidae offers addi- tional insight. The cardiids are in various ways more advanced bivalves than the trigoniids. They have eulamellibranch rather than filibranch gills and well developed siphons with tentacles that often bear eyes (Charles 1966). Their muscular L-shaped foot resembles the trigoniid foot but moves more rapidly, and the cardiids are indeed more rapid burrowers (Stanley 1970). Having a more effective pedal system than the trigoniids, and being somewhat prosogyrous, the cardiids have had much less need for anterior ornamentation to aid in burrowing. Such ornamentation is found in only a few cardiid species (Stanley, in preparation). The two families arrived at quite different solutions to the problems of valve alignment imposed by large angles of gape. The trigoniid solution took the form of large, complex hinge teeth, which are highly specialized and evolved very little after arising in the Triassic. The hinge teeth apparently limited the group’s mobility somewhat by introducing sizeable frictional forces opposing valve movement. These frictional forces can be easily examined by manipulation of empty valves. In the cockles, an alternative and less confining solution was made possible by certain ancestral features of the group: heterodont dentition and radial ribbing of the shell. Elongate, loosely articulating lateral teeth evolved as a mechanism for crude valve alignment at wide gapes, and the interlocking terminations of radial ribbing or fine-scale crenulation of the ventral valve margins arose to ensure accurate final closure. Not only can cardiids jump like trigoniids, but some can swim (Stanley 1970). Movements of the shell are very rapid here, as in burrowing. The condition of the Cardiidae is reminiscent of that of the swimming scallops, in which articulating structures of the hinge are weak and the valves move with little friction. It would seem that the complex dentition of trigoniids, which has borne the entire responsibility for valve alignment, has been one of the chief adaptive deficiencies of the group in comparison with the cardiids. The excellent phylogenetic study by Newell and Boyd (1975) of the Paleozoic trigoniaceans that preceded the Trigoniidae reveals interesting aspects of the origins of trigoniid adaptations. As we would predict, the adaptations led to much greater 896 PALAEONTOLOGY, VOLUME 20 success of the trigoniids, as measured by diversity (text-fig. 1), than was ever attained by their antecedents. Among Newell and Boyd’s conclusions are the following. The early trigoniacean groups were not only of restricted generic diversity, they were of conservative morphology. All pre-Permian forms (Eoschizodidae, Schizodidae) had smooth shells. These gave rise to both smooth-shelled and ornamented taxa, but only certain of the latter diversified markedly and survived into the Jurassic as the Trigoniidae. Newell and Boyd (1975) have shown that the secondary dentition that characterizes the Trigoniidae arose polyphyletically within the more primitive members of the Trigoniacea. The oldest species displaying it is from the Early Triassic, and it also appears in incipient form in several Middle Triassic species. One of the striking discoveries of Newell and Boyd is that the appearance of secondary dentition was sporadic and variable, even within species. Some individuals of transi- tional species may lack any secondary dentition, while others have it along almost all articulating surfaces. The evolution of a full complement of secondary dentition in one or more ancestral groups, together with elongation of the primary teeth, rapidly led to the condition of the advanced Trigoniidae. The exact ancestry of the family is uncertain, but the oldest genus recognized by Newell and Boyd (1975) is Lyrio- myophoria of the Permian (PI. 1 19, figs. 10, 11). Its external morphology is much like that of Trigonia, but its hinge teeth are short and lack secondary dentition. While it is quite likely that late Palaeozoic trigoniaceans were more adept borrowers than other contemporary taxa, we may infer that the modern trigoniacean foot under- went much of its evolutionary development during the origin of secondary dentition in the Triassic, opening one of the most remarkable chapters in the history of the Bivalvia. No Palaeozoic group of suspension-feeding infaunal bivalves compares to the Mesozoic trigoniids in morphologic diversity, including range of body sizes and variety of ornamentation patterns, and I doubt that any Palaeozoic group was their equal in adeptness at burrowing. It was no accident that the Trigoniidae became the most successful group of shallow burrowing bivalves occupying near-shore habitats of Mesozoic seas. Although they clearly remained more primitive than the Cardiidae in ways discussed above, we can, in a sense, view the trigoniids as the cockles of the Mesozoic. The almost total extinction of the family at the close of the Mesozoic certainly had little to do with any of the features discussed in the present study. Like contemporaneous mass-extinctions of other Tethyan groups, it remains a mystery. (The fact that a single recognized genus, Eotrigonia, remained in the early Cenozoic can be viewed as a statistical accident.) Hence, there is no apparent fossil evidence that trigoniids are rare today because they have been unable to meet the demands of the modern marine ecosystem. The Anadarinae (burrowing arcids), which are well represented in modern seas, have life habits that are somewhat similar to those of cardiids and trigoniids but are distinctly less adept burrowers than Neotrigonia (Stanley 1970). Eurther evidence that remnant trigoniids have not performed poorly in the Cenozoic history of the Bivalvia comes from consideration of rates of diversification. New techniques for estimating rates of speciation show that marine Bivalvia have generally speciated at very low rates (Stanley 1975u, in press). Eor newly radiating taxa of the Cenozoic, the net rate of geometric increase (rate of speciation minus rate of extinction) has produced an average doubling time for number of species of STANLEY: COADAPTATION IN TRIGONIID BIVALVES 897 about 1 1 my. Neotrigonia arose in the Oligocene and now contains about six or seven living species. These facts show that the net rate of geometric increase and doubling time for number of species in Neotrigonia are very close to the average for other genera and families of the Bivalvia that have been radiating simultaneously. Clearly Neotrigonia has been holding its own. It seems evident that, if trigoniids had been present in high diversity at the start of the Cenozoic, they would persist in high diversity today. CONCLUSIONS The Trigoniidae radiated early in the Mesozoic, to become the most abundant and diverse family of shallow-burrowing bivalves in shallow marine habitats of the Jurassic and early Cretaceous. The centre of trigoniid distribution was in the Tethyan Realm. The adaptive zone of Mesozoic trigoniids included relatively unstable, sandy areas of the sea-floor. Most populations occupied substrata of grain-supported arenitic lithologies and nearly all lived nearshore, in water less than 10-15 m deep. Trigoniidae of the Mesozoic were shallow borrowers that had life positions similar to that of Neotrigonia, the only living genus of the family. Though a relict, Neotrigonia is not truly a living fossil genus because it ranges back into only the Oligocene. The initial radiation of the trigoniids was triggered by the evolution of a large, muscular, T-shaped foot that probably endowed them with better mobility than was possessed by any Palaeozoic group of suspension-feeding clams. The enormous trigoniid hinge teeth with transverse striations (secondary dentition) evolved to maintain valve alignment at the wide angles of gape required for extrusion of the muscular foot. The appearance of these teeth in the early Mesozoic fossil record signals the origin of the muscular foot. The so-called myophorous buttress of the Trigoniidae is actually a structural support for the large anterior hinge tooth. Evolution of the bulky hinge teeth, myophorous buttresses, and associated anterior adductor muscle virtually eliminated the possibility for the Trigoniidae to evolve a prosogyrous shape from the orthogyrous shape of their ancestors. The lack of a prosogyrous shape of the sort that assists many other bivalve taxa in burrowing was compensated for in the Trigoniidae by the evolution of various kinds of discordant ornamentation that aided in burrowing. The seemingly curious suite of morphologic structures of the Trigoniidae formed a coadaptive system that represented an alternative to the sets of adaptations found in other groups of burrowing bivalves. In their pedal morphology, behaviour, and gross shell form, the Mesozoic Trigoniidae resembled the Cardiidae. Despite being slightly less mobile than cardiids, they can be viewed as the cockles of the Mesozoic. Neotrigonia and the rest of the Trigoniidae are not properly considered to be primitive bivalves. They are more advanced, for example, than the Anadarinae, which resemble them in gross form and life position and which have radiated in the Cenozoic despite being sluggish burrowers. 898 PALAEONTOLOGY, VOLUME 20 For unknown reasons, the Trigoniidae were nearly wiped out by the mass extinc- tion at the end of the Cretaceous. The low present-day diversity of the Trigoniidae is largely a result of this mass extinction. 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Bay and shoreface benthic communities in the Lower Cretaceous. Lethaia, 7, 315-330. seilacher, a. 1954. Okologie der triassischen Muschel Lima lineata (Schoth) und ihrer Epoken : Neues Jh. Geol. Paldont. Monatsh. 4, 163-183. STANLEY, s. M. 1969. Bivalve mollusk burrowing aided by discordant shell ornamentation. Science, 166, 634-635. — 1970. Relation of shell form to life habits in the Bivalvia. Mem. geol. Soc. Amer. 125, 1 296. 1972. Functional morphology and evolution of byssally attached bivalve mollusks. Jour. Paleont. 46, 165-212. 1975a. A theory of evolution above the species level. Proc. nat. Acad. Sci. (U.S.A.), 72, 646-650. 19756. Why clams have the shape they have: an experimental analysis of burrowing. Paleobiology, 1, 48-58. In press. Trends, rates, and patterns of evolution in the Bivalvia. In A. hallam (ed.). Patterns of Evolution. Elsevier, The Hague. STENZEL, H. B. 1971 . Oysters. In R. c. moore (ed.). Treatise on Invertebrate Paleontology, part N, MoUilscu 6, Bivalvia. Geol. Soc. America and University of Kansas Press, Lawrence, Kansas, 954-1224. TEVESZ, M. J. s. 1975. Structure and habits of the ‘living fossil’ pelecypod Neotrigonia. Lethaia. 8, 321-327. WATSON, J. 1971. A Preliminary Account of the Benthic Flora and Fauna of Northwestern Westernport, Victoria. Underwater Research Group of Victoria, Melbourne. WRIGHT. R. p. 1974. Jurassic bivalves from Wyoming and South Dakota: A study of feeding relationships. Jour. Paleont. 48, 425-433. WOODWARD, s. p. 1851. /I Manual of the Mollusca. John Weal. London. STEVEN M. STANLEY Department of Earth and Planetary Sciences Johns Hopkins University Baltimore. Maryland 21218 U.S.A. Typescript received 1 September 1976 J THE EARLIEST TISSOTIID AMMONITE by w. J. KENNEDY and o. h. bayliss Abstract. Pseudotissotia (Pseudotissotia) inopinata sp. nov. is described from the Upper Cenomanian phosphatic Calvcoceras navicularejEucalycoceras pentagonum Zone fauna of Division C of the Cenomanian Limestone of Shapwick Grange, Devon. It is the earliest occurrence of the otherwise exclusively Turonian genus Pseudotissotia Peron, 1897, and the Turonian to Coniacian Family Tissotiidae Hyatt, 1900. The family is otherwise unknown in the Cretaceous of the United Kingdom. The ammonite family Tissotiidae Hyatt, 1900, comprises approximately twenty genera with a widespread, largely Mesogean distribution. The group as a whole is characterized by a tendency towards loss of ornament, by the development of an entire, simple keel or keels, involute coiling, and a suture line which commonly shows a tendency towards multiplication of sutural elements and over-all simplification. Tissotia H. Douville, 1878, and Buchiceras Hyatt, 1875, are perhaps the best-known genera, and are classic Cretaceous pseudoceratites (e.g. Hyatt 1 903), homoemorphous with Triassic ammonoids in their development of entire saddles and denticulate lobes. The group is chiefly known from the Tethyan Realm, especially North and East Africa, the Middle East, Central and South America, Texas and Spain (Bayle 1878; Douville 1912; Peron 1897; Hyatt 1903; Reyment 1954<3, h, 1955; Barber 1957; Collignon 1958, 1965r/; Freund and Raab 1969; Choflfat 1898; Benavides- Caceres 1956; see palaeogeographic maps in Matsumoto 1973u, h). They occur rarely in the U.S. Western Interior (e.g. Cobban and Scott 1972) and are also known from as far south as Madagascar (e.g. Collignon 19656) and Borneo. In Western Europe the family becomes progressively rarer as one moves northward, the most northerly record hitherto being the occurrence of Pseudotissotia (Pseudotissotia) gallienuei (d’Orbigny) in the Turonian of Sarthe and Touraine. The previously known stratigraphic range of the tissotiids is Turonian to Coniacian. The actual dating of their first appearance in southern areas is difficult to relate to northern European faunal successions, but records by Freund and Raab (1969), Reyment (1955), Barber (1957), Wiedmann (1959), and others suggest it to be some way up in the Lower Turonian. So far as evolutionary origins are concerned, Wright in 1952 (p. 221, n. 35) con- sidered the family to be polyphyletic to a minor degree, with their source presumed to be in the Mammitinae. The work of Reyment ( 1954<:/, 6, 1955) on the rich Nigerian faunas led him (1955, text-fig. 31) to suggest the subgenus P. (Bauchioceras) Reyment, 1954 as the rootstock of the group, whilst Barber (1957) suggested that this in turn derived from the vascoceratid Gomheoceras Reyment, 1954, during the early Turonian. Subsequently, Collignon (1965a, p. 179) suggested an alternative origin for the group in the vascoceratids, when he demonstrated that the early Turonian genus Disco- vascoceras Collignon, 1958 bore three keels when young, and could equally be regarded as intermediate between the two families. [Palaeontology, Vol. 20, Part 4, 1977, pp. 901-906, pi. 120.] 902 PALAEONTOLOGY, VOLUME 20 It is therefore of great interest to record what appears to be a P. (Pseudotissotia) from the English Upper Cenomanian, apparently pre-dating the vascoceratids from which certain other tissotids have been claimed, or demonstrated, to be derived, especially as the family has never before been recorded from this country. SYSTEMATIC DESCRIPTION Superfamily ACANTHOCERATACEAE Hyatt, 1900 Family tissotiidae Hyatt, 1900 Subfamily pseudotissotiinae Hyatt, 1903 Genus and Subgenus pseudotissotia Peron, 1897 Type species. Anmionites galliewiei d’Orbigny, 1850. Pseudotissotia inopinata sp. nov. Plate 120. figs. \a-d, 2a-c, text-fig. 1 Derivation of name. Latin wo/) /na/a— unexpected. Holotype. Formerly O. H. Bayliss Collection, no. 257; now B.M. (N.H.). No. C80436. Diagnosis. A Pseudotissotia with a depressed whorl section (breadth to height ratio 1-16), strong umbilical bullae which project into the umbilicus and give rise to broad, subdued, triangulate ribs which efface at mid-flank, and a venter bearing three strong, equal keels. Deseriptiou. The holotype consists of a phosphatic internal mould of just over one-third of a whorl, is partially septate, and retains a considerable amount of phosphatized shell, which largely obscures the sutures. The coiling appears to have been quite involute, with a moderately deep umbilicus; the umbilical wall is vertical, with an abruptly rounded shoulder. The whorl section is depressed, with a whorl breadth to height ratio of M6; the greatest breadth is at the umbilical bullae. The flanks are flattened and convergent, with rounded ventrolateral shoulders. The venter is broad (approximately 80% of maximum whorl breadth), and bears three distinct, entire, strong keels, the two lateral ones being rather more narrowly rounded than the siphonal. The keels are separated by quite deep, rounded grooves, of somewhat greater breadth. Flank ornament consists of strong, rounded umbilical bullae which project slightly into the umbilicus. From these bullae arise broad, flat, triangulate ribs, which efface completely by mid-flank. EXPLANATION OF PLATE 120 Figs. \a-d, 2a-c. Pseudotissotia (Pseudotissotia) inopinata sp. nov. The holotype, Bayliss Collection no. 257, now B.M. (N.H.) no. C80436, a partly septate phosphatic internal mould retaining phosphatized shell. Specimen from the phosphatic Calycoceras navicularel Eucalycoceras pentagonum Zone fauna of Division C of the Cenomanian Limestone, Shapwick Grange, near Lyme Regis, Dorset. \a-d, x 1 ; 2a-c, x2. Figs. 3a-c. Pseudotissotia (Pseudotissotia) galliennei (d’Orbigny). Specimen from the Turonian Tuffeau of Ponce, Sarthe, France. Museum d’Histoire Naturelle, Paris, ex Bourgeois Collection, x 1. PLATE 120 KENNEDY and BAYLISS, earliest tissotiid ammonite 904 PALAEONTOLOGY, VOLUME 20 TEXT-FIG. 1 . Partial suture of the holotype of Pseudotissotia(Pseudotissotia) iiwpinata sp. nov. x 6. Little of the suture line can be deciphered, but there appears to have been a moderate degree of incision to both lobes and saddles (text-fig. 1). Discussion. Identification of this fragment as a tissotiid is based upon whorl section, rib-style, and the prominent equal keels. Erection of a new species based on the frag- ment is justified by the distinctive ornament, and by the great age compared with most other members of the group. Three subgenera have been distinguished within Pseudotissotia. Of these, P. (Bauchioceras) Reyment, 1954 has crenulate keels, and a siphonal keel which may be very feeble, together with ribs which extend across the whole of the flank at comparable diameters. Species such as P. {B.) nigeriensis (Woods), P. (B.) tricarinata (Reyment) are thus readily distinguishable from P. {P.) inopinata. P. (Wrightoceras) Reyment, 1954 has compressed outer whorls which lack a siphonal keel, whilst the umbilical region may be inflated. Species such as P. (Wrightoceras) wallsi (Reyment), P. (W.) mirabilis (Pervinquiere), P. (W.) mimieri (Pervinquiere), P. (W.) Uareni Karrenberg, and P. ( W.) gagnieri Faraud may be distinguished from the present form by these criteria. When compared with typical P. (Pseudotissotia), a specimen of the type species of which is figured for comparison (PI. 120, fig. 2>a-c), the attribution of our specimen to the restricted subgenus is quite clear, for it has three distinct, entire keels. When compared with P. (P.)galliennei, P. (P.) inopinata is depressed and broad, rather than high-whorled and compressed, whilst all specimens of P. (P.) galliennei we have seen completely lack umbilical bullae and ribs at comparable diameters; the long, low, fold-like ribs of the adult instead appear at much larger diameters, as in Peron’s specimen (Peron 1897, p. 28, pi. 2, fig. 3; pi. 3, fig. 1). The suture of P. (P.) inopinata is, in addition, more divided than that of P. (P.) galliennei. Collignon (1957, p. 15) has described, but not figured, a var. inflata of P. (P.) galliennei, based on a rather worn specimen from the Turonian of Tinhret (Fezzan). It has a breadth: height ratio of 0-83, substantially less than the present species, but further comparison is difficult in the absence of illustrations of Collignon’s variety. KENNEDY AND BAYLISS: EARLIEST TISSOTIID AMMONITE 905 Occurrence. The holotype and only known specimen of Pseudotissotia inopinata is from Division C of the Cenomanian Limestone exposed in the large chalk pit at Shapwick Grange Farm, Devon, near Lyme Regis, Dorset (National Grid Reference SY 313918). Age. The sequence at Shapwick Grange is closely similar to that on the Devon Coast described by Kennedy (1970, p. 657 ; text-fig. 1 5) who also summarizes previous work. Large collections from the succession have enabled us to place the present specimen and associated material precisely in sequence. Division B of the Cenomanian Lime- stone at Shapwick has yielded scarce Acanthoceras of Middle Cenomanian age. This unit is terminated by a phosphatic veneer, and overlain by the glauconitic chalk of Division C ; from the base of this comes a rich phosphatic fauna including, in addition to P. (P.) inopinata, the following ammonites in similar preservation (O. H. Bayliss Collection); abundant Schloenbachia lymense Spath. Calycoceras spp., including C. (C.) navicular e (Mantell), C. (C.) guerangeri (Spath), C. (Lotzeites) aberrans (Kossmat), Eucalycoceras pentagonum (Jukes-Browne), E. rowei (Spath), Prota- canthoceras including P. compressum (Jukes-Browne) and P. bunburianum (Sharpe), Thomelites spp., including T. aff. sornayi (Thomel), Eorbesiceras spp., Hanntes cf. simplex (d’Orbigny) and abundant Scaphites equalis J. Sowerby. This is an Upper Cenomanian, C. navieularejE. pentagonum Zone fauna. Occurring somewhat higher in Division C is an essentially indigenous fauna preserved as glauconite-coated moulds. This includes Sciponoceras gracile {S>\\\xra?Lxd), C. navicular e, Allocrioceras annulatum (Shumard), Pseudocalycoceras dentonense (Moreman), and Metoicoceras geslinianum (d’Orbigny) ( = M. gourdoni de Grossouvre). This fauna indicates the latest Cenomanian S. gracile Zone (for a dis- cussion of zonal nomenclature see Kennedy and Juignet 1976, and Rawson et al. in press). DISCUSSION The recognition of a Pseudotissotia in the English Cenomanian would seem to confirm Wright’s (1952) suggestion that the Tissotiidae are polyphyletic, for Bauchioceras appears to be a quite definite derivative of the early Turonian vascoceratid Gombeo- ceras, as Reyment (1955) and Barber (1957) demonstrated, whilst Collignon’s Discovascoceras is a further contender as a vascoceratid ancestor for other tissotids. The origin of P. inopinata remains a problem. The morphologically closest con- temporary ammonites appear to be amongst the Acanthoceratinae. Certain com- pressed Acompsocerashom the Lower to Middle Cenomanian develop a low siphonal keel and sharp ventral shoulders which are sometimes tuberculate, e.g. Acompsoceras essendiense (Schliiter) and A. renevieri (Sharpe) (Kennedy 1971, p. 67 et seq., pi. 30, pi. 31, fig. 2). These forms may also bear umbilical bullae and ribs, which die out on the flank. Mr. C. W. Wright has also drawn our attention to certain compressed, feebly ornamented variants of Acanthoceras rhotomagense (Brongniart) which show similar flank ornament and develop an incipient siphonal keel; we would suggest, therefore that, within the Cenomanian acanthoceratid radiation, these forms were a possible source for P. (P.) inopinata. 906 PALAEONTOLOGY, VOLUME 20 Acknowledgements. We thank Dr. J. M. Hancock and Mr. M. R. Cooper for useful discussions, and Mr. C. W. Wright for advice, and for critically reviewing the manuscript of this article. BARBER, w. 1957. Lower Turonian ammonites from north-eastern Nigeria. Bull. geol. Surv. Nigeria, 26, 86 pp., 34 pis. BAYLE, E. 1878. Fossiles principaux des Terrains. Explic. Carte geol. France, 4 (1) (Atlas), 158 pis. BENAViDES-CACERES, V. E. 1956. Cretaceous system in northern Peru. Bull. Am. Mus. nat. Hist. 108, 357-498, pis. 31-66. CHOFFAT, p. 1898. Recueil d’etudes paleontologiques sur la faune cretacique du Portugal. 1, Especes nouvelles ou peu connues. 2, Les ammonees du Bellasian, des Couches a Neolobites vibrayeanus, du Turonien et du Senonien. Trav. geol. Portugal, 1898, 41-86, pis. 3-22. COBBAN, w. A. and scott, g. r. 1972. Stratigraphy and ammonite fauna of the Graneros Shale and Green- horn Limestone near Pueblo, Colorado. Prof. Pap. U.S. geol. Surv. 645, 108 pp., 41 pis. COLLiGNON, M. 1958. Cephalopodes neocretaces du Tinhret (Fezzan). Annis Paleont. 43, 1 15-136, pis. 16-18. 1965u. Nouvelle ammonites neocretaces Saharienne. Ibid. 51, 165-202, pis. A-H. 19656. Atlas des Fossiles Caracteristiques de Madagascar (Ammonites) fasc. 12 (Turonien), pp. 1-82, pis. 376-413. Service Geologique, Tananarive. DOUViLLE, H. 1912. Evolution et classification des Pulchelliides. Bull. Soc. geol. Fr. (4) 11, 285-320. FREUND, R. and RAAB, M. 1969. Lower Turonian ammonites from Israel. Spec. Pap. Palaeont. 4, 83 pp., 10 pis. HYATT, A. 1903. Pseudoceratites of the Cretaceous. Monogr. U.S. Geol. Surv. 44, 351 pp., 47 pis. JUIGNET, p. and KENNEDY, w. J. 1977. Stratigraphic comparee du Cenomanien du sud d’Angleterre et de la Haute Normandie. Bull. Soc. Geol. Normandie et Amis du Museum du Havre (in press). KENNEDY, w. J. 1970. The correlation of the uppermost Albian and the Cenomanian of south-west England. Proc. Geol. Asi'. 81, 613-677. 1971. Cenomanian ammonites from Southern England. Spec. Pap. Palaeont. 8, 133 pp., 64 pis. PERON, A. 1896-1897. Les ammonites du Cretace Superieur de I’Algerie. Mem. Soc. geol. Fr. 6 (1896), 1-24, pis. 1-6; 7 (1897), 25-88, pis. 7-18. RAWSON, p. et al. A correlation of the Cretaceous Rocks of the British Isles. Geological Society of London (in press). REYMENT, R. A. 1954u. New Turonian (Cretaceous) ammonite genera from Nigeria. Colon. Geol. Min. Resour. 4, 149-164, 4 pis. 19546. Some new Upper Cretaceous Ammonites from Nigeria. Ibid. 248-270, 5 pis. 1955. The Cretaceous Ammonoidea of southern Nigeria and the southern Cameroons. Bull. Geol. Surv. Nigeria. 25, 112 pp., 25 pis. wiEDMANN, J. 1959. Le Cretace Superieur de I’Espagne et du Portugal et ses cephalopodes. C.R. Congres des Societes Savantes-Dijon 1959: Collogue sur le Cndace superieur fraru;ais, 709-764, 8 pis. WRIGHT, c. w. 1952. A classification of Cretaceous ammonites. J. Paleont. 26, 213-222. 1957. In ARKELL, w. J., et al. Treatise on Invertebrate Palaeontology. Part L, 4, 490 pp., 558 figs. University of Kansas Press and Geological Society of America. Lawrence, Kansas and New York. REFERENCES W. J. KENNEDY Department of Geology and Mineralogy Parks Road Oxford Typescript received 12 May 1976 Revised typescript received 19 July 1976 O. H. BAYLISS Spring House Uplyme Dorset THE PRE-DEPOSITIONAL FORMATION OF SOME LEAF IMPRESSIONS by ROBERT A. SPICER Abstract. Observations show that an inorganic sedimentary encrustation may be built up on plant leaves within a few weeks after entry into a depositional environment. Such an encrustation may be the basis of a detailed impression fossil. SEM examination and X-ray microanalysis of this encrustation on freeze-fractured, freeze-dried leaves reveals preferential deposition of fine-grained, iron-rich material that faithfully replicates the epidermal surface detail of the leaf By analysis, fossil-leaf impressions from the Upper Cretaceous Dakota Sandstone of Kansas are shown to have a similar elemental composition. A possible biogenic origin for the surface encrustation is suggested. In a recent paper Schopf (1975) reviewed the forms in which plants may be preserved as fossils. They may be preserved by cellular permineralization (petrifaction) in which three-dimensional cellular detail is retained, by the remains becoming com- pressed in the vertical plane often accompanied by coalification of the original tissues (compression), as external or internal moulds and occasionally bulk replacement by inorganic material (authigenic preservation), or as unaltered hard parts (duripartic preservation). The factors governing the type of fossil that will be formed are a com- bination of the nature of the plant material, the events both preceding and following burial, and the physical and chemical characteristics of the entombing sediment. The term impression fossil may be loosely applied to that which remains when the coalified organic remains in a compression fossil (the anthracolemma) are removed from the rock (either by the palaeobotanist or by weathering) or to the surface mould of a leaf in a concretionary nodule (authigenic fossil). In this paper both meanings are implied. Impression fossils have in the past received less detailed study than some of the other forms of fossil primarily because they lack organic remains and retain only surface detail. However, with improved study techniques (particularly the examina- tion of silicone rubber impression replicas in the Scanning Electron Microscope (SEM) (Chaloner and Gay 1972) and the increasing taxonomic use of foliar venation and cuticular characters (see review in Dilcher 1974)) more attention is being paid to the impression fossil. Schopf (1975) wrote: ‘By authigenic preservation fossil fragments commonly have been encased by cementing materials during the soft mud stage soon after burial. The requirements are deposition in fine textured sediment and commonly, but not invariably, early precipitation of authigenic minerals in sediment pore space around the organic fragment.’ Krystofovich (1944) recognized that plant material deposited in stagnant pools often becomes coated with a thin encrustation of inorganic material even before burial. He suggested that carbon dioxide given off by the decaying vegetable matter might cause chemical precipitation of the film (which he termed primary or initial crust) and that subsequent thickening of this film could lead to the eventual preservation of the remains. While studying the potential formation of plant fossil beds in Recent aquatic environments (Spicer 1975), it was similarly noted [Palaeontology, Vol. 20, Part 4, 1977, pp. 907-912.] 908 PALAEONTOLOGY, VOLUME 20 that many leaves became encrusted with a layer of inorganic material within a few weeks after entry into a freshwater stream or lake environment but before final deposition had taken place. The sediment crust was often so coherent that it could not be removed by washing and adhered to the leaf even during violent transport. This paper described the nature of the sedimentary crust, as revealed by X-ray microanalysis in the SEM, makes a comparison with a similar fossil impression, and suggests a possible biogenic origin for the encrustation. THE FIELD SITE All the modern leaves studied were collected from a freshwater fluviolacustrine environment in the grounds of the Imperial College Field Station at Silwood Park, near Ascot, Berkshire, England. Here a small stream drains from iron-rich Tertiary Bagshot Sands and flows into Silwood Lake where it has formed a delta, the surface sediments of which are composed mainly of flocculent ferric hydroxide (Fe(0H)3.nH20) similar to that described by Coey and Readman (1973). Sheaths of the iron bacterium Sphaerotilus sp. were abundant in both stream and delta surface sediment, together with a small quantity of quartz sand grains and diatom frustules, and are figured in Muir et al. (1974). Leaves for study were collected from both fluviatile and deltaic surface sediments. Specimens of fossil-leaf impressions from the Upper Cretaceous Dakota sandstone in Kansas were borrowed from the Museum of Paleontology of the University of California at Berkeley. METHOD Modern leaves were prepared under both field and laboratory conditions in the following manner. A rectangular (approximately 7 mm x 10 mm) piece of intercostal lamina was cut from the unwashed leaf using scissors, which facilitated cutting the leaf with a minimum of contamination of either epidermal surface. This piece of leaf was then mounted vertically in a groove that had been previously cut in an aluminium scanning electron microscope stub and the two halves of the stub were squeezed together so as to lightly grip the leaf. Two small nicks were made in the leaf approximately 1 mm above the surface of the stub to aid fracturing in the desired position. The mounted leaf was then plunged into ‘Arcton 12’, held at its melting point of 155 °C., and, with the aid of stainless steel forceps, the leaf was fractured parallel to the stub surface. The stub and leaf were then rapidly transferred to the specimen block (pre-cooled to 70 °C.) of a freeze dryer (Spicer et al. 1974) and the leaf was freeze dried at -70 °C. for 48 hours. When dry the specimen was vacuum coated with carbon and examined in a Cambridge Stereoscan MkllA fitted with an ORTEC SiLi energy dispersive X-ray detector. Fossil specimens were mounted directly on to aluminium stubs and coated with carbon before being examined in a Cambridge SI 80 SEM with an EDAX SiLi energy dispersive X-ray detector. SPICER: FORMATION OF FEAF IMPRESSIONS 909 TEXT-FIG. 1 . An air-dried leaf of Fagus sylvcitica recovered from iron-rich stream sediments. The surface encrusta- tion has curled back from the leaf during drying to reveal a faithful impression of the leaf surface, x 900. RESULTS AND DISCUSSION Text-fig. 1 illustrates the nature of the sediment coat on the lower epidermal surface of a leaf of Fagus syhatica L. extracted from the surface of the deltaic deposits. Little fungal breakdown is evident in the tissues of the leaf but the coherent encrustation has already formed. This figure shows a partially air dried F. sylvatica leaf from the stream waters. The partial air drying, whilst leading to some tissue collapse, has resulted in the curling back of the encrustation revealing faithful replication of the epidermal cellular detail. The results of the X-ray microanalysis of the encrustation are presented in text-figs. 2 and 3. Tt can clearly be seen that the spot analysis (i.e. with a stationary electron beam) of the external surface of the sedimentary crust (text- fig. 3) exhibits large silicon and iron peaks as well as pronounced sulphur and chlorine peaks. By comparison the spot analysis of the sedimentary encrustation originally in contact with the leaf surface (text-fig. 2) exhibits no silicon peak and the sulphur and chlorine peaks are considerably reduced. Some, possibly all, of the attenuation of the sulphur and chlorine peaks may be due to X-ray absorption because the analysis was of necessity restricted to a portion of the specimen not directly ‘seen’ by the detector. The loss of the silicon peak, however, is so complete that it is unlikely that such an effect could explain its absence. Rather the analysis indicates that the sedi- ment in contact with the leaf is almost entirely composed of iron-rich material, most probably finely divided ferric hydroxide. After this deposit had formed on the leaf, the coarser fractions of the sediment, namely the quartz grains and diatom frustules, became incorporated. Thus the epidermal features of a leaf may become preserved in the fine-grained iron flocks in spite of the coarser nature of the bulk sedimentary components. 910 PALAEONTOLOGY, VOLUME 20 Fe TEXT-FIG. 2. Results of the X-ray microanalysis of the surface of the encrustation originally in direct contact with the leaf of Fagus sylvatica. Fe TEXT-FIG. 3. X-ray spectrum from the analysis of the encrustation. The electron beam was positioned on the surface of the encrustation not originally in contact with the leaf surface (i.e., exposed to the stream waters). Krystofovich ( 1944) noted that often good quality plant impressions may be found even in coarse-grained sediments and cited examples from the Paleocene and Eocene floras of the Ukraine and Volga and the South Urals. Similar examples may be found in the Dakota sandstone fossils and analyses of these impressions yield elemental compositions comparable to those observed in the Recent material. The X-ray spectrum of a leaf impression from the Dakota sandstone (text-fig. 5) exhibits a very high iron peak compared to that of silicon. Text-fig. 4 is a spectrum TEXT-FIG. 4. X-ray spectrum from the area of sedi- text-fig. 5. X-ray spectrum obtained from the ment matrix which surrounds the Dakota sandstone surface of the Dakota sandstone leaf-impression fossil leaf impression. fossil. SPICER: FORMATION OF LEAF IMPRESSIONS 911 obtained from the sedimentary matrix of the same specimen; there is a very high silicon peak in relation to the iron. This seems to indicate that the leaf impression was composed mainly of iron-rich material. The impression itself unfortunately showed little cellular detail except along veins where elongated cells with their longest axis aligned parallel to the vein could be seen. While the quality of the impression is not as good as some described in the literature (e.g. Chaloner and Collinson 1975), it is evident that the impression itself is made up of much finer-grained material than that of the surrounding matrix. A number of analyses were carried out on this and other specimens and all gave similar results. CONCLUSIONS High iron concentrations on a fossil impression do not necessarily mean that an encrustation was laid down prior to deposition and burial. It is well known that many minerals, particularly those of iron, will form around an organic nucleus during diagenesis although the mechanism for this process is not well understood (Tarr 1921 ; Edwards and Baker 1951; and Schopf 1975). Too close a comparison between the Silwood leaves and the Dakota sandstone fossils is not warranted because they were probably formed in different depositional environments. Most of the Dakota sand- stone has been interpreted as marginal marine (Lee 1923; Waage 1959) laid down by an advancing Cretaceous sea and as such represents a variety of local depositional environments. Nevertheless, it has been demonstrated that such an encrustation, having the same elemental composition as that which may be observed in the fossil state, may develop before the leaf has finally been deposited, even within a few weeks after entry into a stream or lake environment. The effect of such a coating may be to limit biological breakdown either by inverte- brate particle feeders or micro-organisms. The cuticle surface would certainly be partially protected from abrasion during transport with the result that fine surface detail could be preserved. The proposition of Krystofovich that precipitation of sediment at the plant surface is caused by carbon dioxide given off by the decaying organic matter may not account for the formation of the ferric hydroxide encrustation observed in the Silwood environment because the encrustation was also seen to occur on such biologically inert substances as a glass bottle and nylon rope. If carbon dioxide was in some way causing the precipitate then the encrustation would be expected to be greater on the decaying plant matter than the inert material, a phenomenon that was not observed. The mechanism of deposition of this early encrustation has not yet been established but may result from the activity of iron bacteria at or on the leaf surface. The close association of micro-organisms and mineral deposition has been frequently reported (Stocks 1902; Kuznetsov et al. 1963; Love and Murray 1965; and Ehlers el al. 1965) and it seems likely that the role of micro-organisms in the mineral preservation of both animal and plant remains may well be greater than was at one time thought. Acknowledgements. I am very grateful for the assistance of Mr. Paul Grant and Mr. Robert Oscarson and for the advice of Dr. M. D. Muir, Dr. K. L. Alvin, and Dr. J. A. Wolfe. Part of this work was undertaken whilst I was in receipt of an N.E.R.C. research studentship at Imperial College London and part whilst as a Lindemann Fellow at the U.S. Geological Survey in Menlo Park, California. 912 PALAEONTOLOGY, VOLUME 20 REFERENCES CHALONER, w. G. and COLLINSON, M. E. 1975. Application of SEM to a sigillarian impression fossil. Rev. Paleobiol. Palynol. 20, 85-107. and GAY, M. M. 1972. Scanning Electron Microscopy of latex casts of fossil plant impressions. Palaeonto- logy, 16, 654-659. COEY, J. M. D. and readman, p. w. 1973. Characterization and magnetic properties of natural ferric gel. Earth and Planetary Sci. Letters, 21, 45-51. DiLCHER, D. L. 1974. Approaches to the identification of angiosperm leaf remains. Bot. Rev. 40, 1-157. EDWARDS, A. B. and BAKER, G. 1951. Some occurrences of supergene iron sulphides in relation to their environment of deposition. J. Sediment. Petrol. 21, 34-46. EHLERS, E. G., STILES, D. V. and BIRLE, J. D. 1965. Fossil bacteria in pyrite. Science, 148, 1719-1721. KRYSTOFOViCH, A. 1944. Mode of preservation of plant fossils and its bearing on the problem of coal forma- tion. Am. Jour. Science, 242, 57-73. KUZNETSOV, s. I., IVANOV, M. w. and LYALIKOVA, N. L. 1963. Introduction to Geological Microbiology. McGraw-Hill, New York, 252 pp. LEE, w. T. 1923. Continuity of some oil bearing sands of Colorado and Wyoming. Bull. U.S. Geol. Survey, 751-A, 1-22. LOVE, L. G. and Murray, j. w. 1965. Biogenic pyrite in recent sediments of Christchurch Harbour, England. Am. Jour. Sci. 261, 433-448. MUIR, M. D., HAMILTON, L. H., GRANT, p. R. and SPICER, R. A. 1974. A Comparative study of modern and fossil microbes using X-ray microanalysis and Cathodoluminescence. In hall, t. a., echlin, p. and kauffman, r. (eds.). Microprobe Analysis as Applied to Cells and Tissues. Academic Press, 435 pp. SCHOPF, J. M. 1975. Modes of fossil preservation. Rev. Paleobotany and Palynology, 20, 27-53. SPICER, R. A. 1975. The Sorting of Plant Remains in a Recent Depositional Environment. University of London, unpublished Ph.D. Thesis, 309 pp. GRANT, p. R. and MUIR, M. D. 1974. An inexpensive portable freeze-drying unit for SEM specimen preparation. Proc. VII Ann. S.E.M. Symposium I.I.T.R.I. Chicago, 299-304. STOCKS, M. B. 1902. On the origin of certain concretions in the Lower Coal Measures. Quart. J. Geol. Soc. Lond. 58, 46-58. TARR, w. A. 1921. Syngenetic origin of concretions in shale. Bull. Geol. Soc. Amer. 32, 373-384. WAAGE, K. M. 1959. Stratigraphy of the Inyan Kara Group in the Black Hills. Bull. U.S. Geol. Survey, 1081-B, 13-26. ROBERT A. SPICER Typescript received 7 July 1976 Revised typescript received 10 November 1976 Branch of Paleontology and Stratigraphy U.S. Geological Survey 345 Middlefield Road Menlo Park California 94025 U.S.A. SHORT COMMUNICATIONS UNUSUAL PATTERN PRESERVATION IN A LIASSIC AMMONITE FROM DORSET by E. C. MANLEY Abstract. Regular colour markings on a specimen of Asteroceras stellare (J. Sowerby) are compared with the tuberculation known within this species. A FRAGMENT of an ammonite collected from fallen material on the beach below Black Ven, Dorset, by C. J. Burnell was found, on examination, to show unusual colour markings. It has been desposited with the British Museum (Natural History), Registered Number C 79624. The specimen is an internal cast of the body chamber of an Asteroceras stellare (J. Sowerby). It must have come from within the Stellare sub-zone (Obtusum Zone) of the Sinemurian, and can probably be ascribed to the Stellare Nodule Band, or close to it (i.e. bed 88f of Lang 1926, p. 158). The infilling is a dark-grey limestone. The specimen has become flattened considerably on one side, with fracturing along the keel. The flattened side is covered with fibrous calcite, and removal of this showed that the surface of the shell has become destroyed by the crystal growth. Traces of the inner whorls, preserved in brown sparry calcite, are grossly distorted. A little pyrite is present along the keel. The ratio between the adoral width and height of the whorl suggests that some flattening of the relatively undistorted side has also occurred, although there is no visible damage. The specimen is slightly worn, but most of the surface is still covered by a thin, dark brown, calcareous coating which retains a weak nacreous lustre towards the ventral shoulder, and elsewhere displays a brown, finely granular gloss. This brown layer bears a reticulate pattern of dark spots, which are almost black. These are slightly elongated parallel to the periphery, and a few of the best preserved (near the venter) show a central zone which is slightly lighter than the border. In these areas of best preservation there is pigmentation between the spots, forming darker peripheral lines against the brown background. At their maximum development, these spots are 1-5 mm wide (radially to the whorl), and 2 0 mm long, whilst the greatest spacing between the sets of spots is 6-0 mm radially, and 5 0 mm in the growth direction. Reference to the collections of the British Museum (Natural History) showed specimens of Asteroceras stellare which bore an analogous patterning, and Specimen C 56978 was selected for comparison. The specimen is crushed, and slightly distorted. Judging from the adherent matrix, it came from a calcareous nodule. Three whorls are visible in the damaged umbilical area. The specimen is incomplete, since it terminates at a septum, but from the septal spacing it seems probable that most, if not all, of the phragmacone is present. At the apertural septum the diameter is about 230 mm, the whorl height about 85 mm, and the whorl breadth is estimated to be about 70 mm. Much of the specimen is preserved as an internal cast in brown sparry calcite. The ribbing and sutures are occasionally well displayed. The external details [Palaeontology, Vol. 20, Part 4, 1977, pp. 913-916.] 914 PALAEONTOLOGY, VOLUME 20 TEXT-FIG. 1. Asteroceras stellare (J. Sowerby), internal cast of body chamber, demonstrating the regularity and extent of the colour markings. Specimen C 79624, x 1. of the shell have been preserved in a few places, and ornament can be seen to cover at least the outer third of the outer whorl. This ornament is of small uniform tubercles, up to 1 mm in diameter, arranged in lines parallel to the periphery. The spacing of the tubercles within the lines is extremely regular, and average figures vary steadily from a maximum of 3 0 mm at the outer end of the exposed whorl (where the line-spacing is about 2-5 mm) to a minimum of 2-4 mm at the inner end. The tubercles are rounded, and slightly elongated along the line of tuberculation. At one point on the venter, one whorl before the apertural septum, these tubercles are plainly seen to be linked within each line by a threadlet of raised calcite. On the penultimate half whorl, growth lines can be seen on the venter, especially on the keel, and these show that each period of growth started with the formation of a line of tubercles and was followed by deposi- tion of smooth shell up to the next growth line. The tubercles are most strongly developed along the keel; their diminution in strength appears due solely to preserva- tional variations. This style of tuberculate ornament has been described, within the genus, on various occasions, and seems to be a variable feature. Wright, discussing A. stellare (1881, 295 and 296, pis. 21 and 22), mentioned only that the specimens were ‘finely MANLEY: PRESERVED AMMONITE PATTERN 915 punctuated’, whilst Guerin-Franiatte (1966, 283-286, pis. 153-155; text-figs. 144 and 145), after referring to Sowerby’s type of A. stellare as ‘quadrille et ponctue’, remarked that ‘Quelques-uns de nos exemplaires presentent un test identique, celui-ci se retrouve d’ailleurs chez d’autres especes du genre Asieroceras' . Reynes (1879, pi. 36, fig. 3) illustrated very clearly the pattern of tuberculation of a specimen of A. stellare. TEXT-FIG. 2. Asieroceras stellare (J. Sowerby), surface of venter, showing the tuberculation. Specimen C 56978, x 1. Specimen C 79624 is a body chamber, as is demonstrated by the lack of sutures, the infilling by matrix material, and the distortion during diagenesis. Well-preserved body chambers of A. stellare are rare (M. K. Flowarth, pers. comm.). In these circumstances, any comparison between the body chamber of one ammonite and the phragmacone of another must necessarily be somewhat imperfect, and the inherent uncertainties must be increased considerably by the comparison of an internal cast of the one with the shell of the other. To suggest, then, a relationship between colour markings of the one and tubercles of the other must seem dubious. However, it seems, that the resemblance of the two patterns is so close that the two can be considered as two representations of the same feature. This specimen must represent a very abnormal set of conditions of preserva- tion. Colour patterns in the Cephalopoda have been noted within orthoceratids, principally by Ruedemann (1921), and, within the Ammonoidea, by such as Arkell (1957, L92 and L93, fig. 138), Greppin (1898, 22 and 23), Schindewolf (1928), Spath (1935), and Tozer (1972, pi. 126, fig. 3), but all these refer to colour manifestation in bands and stripes upon the outside of the shell. Nowhere is there any mention of pattern decipherable upon the inner surface of the body chamber, or upon the infilling matrix in contact with it, apart from Tozer’s discussion of the very different wrinkle-layer (op. cit.). 916 PALAEONTOLOGY, VOLUME 20 Acknowledgements. The author wishes to thank Mr. C. J. Burnell, who found the specimen, and Dr. M. K. Howarth, who suggested the comparison with the tuberculate specimens of the British Museum (Natural History). Dr. M. B. Hart and Mr. H. W. Bailey are also thanked for their help in preparing the manuscript. REFERENCES ARKELL, w. J. 1957. Mesozoic Ammonoidea. In moore, r. c. (ed.). Treatise on Invertebrate Paleontology, Part L, MoUnsca 4. University of Kansas Press, Lawrence, Kansas. GREPPiN, E. 1898. Description des fossiles du Bajocien Superieur des environs de Bale. Mem. Soc. Paleont. Suisse, 25, 1-52, pis. 1-5. GUERIN-FRANIATTE, s. 1966. Ammonites du Lias Inferieur de France. Psilocerataceae: Arietitidae. Tome 1 : Texte; Tome 2: Planches. Ed. du Cent. Nat. de la Rec. Sci. LANG, w. D. 1926. The Black Marl of Black Ven and Stonebarrow, in the Lias of the Dorset coast. Q. Jl Geol. Soc. Loud. 82, 144-165. REYNK, p. 1879. Monographic des Ammonites. Lias. Atlas. PI. 36, figs. 3, 4. RUEDEMANN, R. 1921. On colour bands in Orthoceras. Bull. N.Y. State Mus. Pp. 79-88. SCHINDEWOLF, o. H. 1928. Uber Farbstreifen bei Amaltheus (Paltopleuroceras) spinatum Brug. Palaont. Zeit. 10, 136-143. SPATH, L. F. 1935. On colour-markings in ammonites. Ann. Mag. Nat. Hist. (10), 15, 395-398, pi. 18. TOZER, E. T. 1972. Observations on the shell structure of Triassic ammonoids. Palaeontology, 15, 637-654, pis. 124-128. WRIGHT, T. 1881. Monograph on the Liassic ammonites of the British Islands. Vols. 32-39 of Pub. Palaeontogr. Soc. E. C. MANLEY School of Environmental Seiences Plymouth Polytechnie Plymouth, PL4 8AA Typescript received 11 June 1976 SYNONYMY OF THE CARBONIFEROUS TRILOBITES NAMUROPYGE AND COIGNOUINA by JOHN MILLER Abstract. The first articulated specimen of Namuropyge acanthim (Coignou, 1890) is described from the Visean of Treak Cliff, Derbyshire. This specimen confirms that cephala described as Coignouina Reed, 1943 and pygidia described as Namuropyge R. and E. Ritcher, 1939 are congeneric. Speculation that the small Visean otarionid cephalon Coignouina and the pygidium Namuropyge belong to the same trilobite is confirmed by the first articulated exoskeleton, collected by J. W. Tilsley from Treak Cliff, Derbyshire. Coignouina thus becomes a junior subjective synonym of Namuropyge. SYSTEMATIC PALAEONTOLOGY Family otarionidae R. and E. Richter, 1926 Subfamily cyphaspidinae Pfibyl, 1947 Genus namuropyge R. and E. Richter, 1939 Type species. Namuropyge demaneti R. and E. Richter, 1939, from the Namurian of Belgium. Emended diagnosis. Otarionid trilobite with cephalon bearing two marginal spine rows, the outer row short and declined, the inner row massive and inclined. Facial suture ankylosed, eyes apparently without lentiferous surface; stalked. Thorax apparently of seven segments with outwardly directed stout spines on pleurae of at least fourth and seventh segments, and a large median axial spine on penultimate segment. Pygidium with seven to fifteen axial rings, four to ten pleural ribs; posterior pleural band distinctly elevated above the anterior band; pygidial margin spinose. Namuropyge acanthina (Coignou, 1890) Text-fig. lo, b Material and locality. British Museum (Natural History) no. It 13278, apron reef facies of Bee Low Limestones, Dinantian Dj Zone; Treak Cliff, Derbyshire, England (SK 1343 8328). Preservation. Local exfoliation of cuticle has occurred, affecting mainly the genal areas, crests of the thoracic axial rings, the pleural tips, and the pygidial margin (text-fig. la). The trilobite has been twisted in a vertical plane about its sagittal axis, resulting in slight telescoping of thorax segments one to four and disarticulation of the rest of the trunk. Segments five and six have been pushed forwards and rotated in a horizontal plane oblique to the sagittal axis such that their right side pleurae lie partly under the pleurae of segments three and four. The axial ring of segment five is seen because part of the fourth ring has been broken away, and it lies somewhat [Palaeontology, Vol. 20, Part 4, 1977, pp. 917-919.] 918 PALAEONTOLOGY, VOLUME 20 forward on the articulating half-ring of segment six. Because of a sharp change in level at this point, there is little doubt that segment five is present and is not merely the articulating half-ring of the succeeding segment. Segment seven is seen on the right-hand side, having been moved forward of the pygidium and rotated so that its left pleura lies under the left anterior pleural field of the pygidium. TEXT-FIG. 1. Nanmropyge acanthina (Coignou, 1890), Treak Cliff, Derbyshire. Specimen It 13278; a, dorsal view; h, oblique lateral view; x 7. Description. The cephalon has been described by Osmolska (1967) and additional points noted by Miller ( 1 973). The only further information on the cephalon provided by the present specimen is that it shows a pair of faint ridges running from the eye to the axial furrow. Thorax apparently with seven segments, but disarticulated behind the fourth. Axis broad (tr.) and about one third total width (tr.); tapering slightly posteriorly. Each axial ring broad (sag.) with articulating half-ring and articulating furrow together at least two-fifths width (sag.) of posterior band; articulating half-ring strongly convex anteriorly. Large median spine-base on annulus of sixth axial ring. Anterior and posterior pleural bands nearly equal in width (exsag.), with broad articulating facets immediately exsagittal of lateral geniculation. Pleural tips possibly bluntly rounded. Fourth pleural band with stout spine base at geniculation, directed upwards and slightly posteriorly. Seventh posterior pleural band with similarly directed spine. Pygidium subtriangular in outline; length; width ratio 0-55 excluding spines. Axis conical ; anteriorly rather less than half pleural width, tapering posteriorly to rounded termination slightly anterior of margin; at least seven axial rings, of which at least five are distinct, becoming weaker posteriorly; rings strongly convex. Articulating MILLER; NAMUROPYGE 919 half-ring broad (sag.), strongly convex forwards. Four pairs of pleural ribs which widen slightly towards margin, with posterior pleural band elevated above the anterior and terminating in a stout spine close to the margin ; pleural furrows some- what broader than and more or less parallel with interpleural. Border narrow, steeply declined; three or four widely spaced terrace lines visible on external mould of doublure. Ornament of cephalon sparsely granulate; pygidial axis with transverse row of granules on the highest part of the ring, beeoming indistinct posteriorly. Remarks. Namuropyge acanthina has a much reduced number of thorax segments (apparently seven) compared with the typical twelve to fourteen for otarionids. The median axial spine of N. acanthina is, however, on the sixth thoracic segment as in most other members of the family. REFERENCES coiGNOU, c. 1890. On a new species of Cyphaspis from the Carboniferous rocks of Yorkshire. Q. Jl geol. Soc. Loud. 46, 421-422. MILLER, J. 1973. Coignouina decora sp. nov. and Carbonocoryphe hahnorum sp. nov. (Trilobita) from a Visean fissure deposit near Clitheroe, Lancs. Geol. Mag. 110, 1 13-124. OSMOLSKA, H. 1967. Some Otarionidae (Trilobita) from the Lower Carboniferous of Europe. Acta palaeont. Polonica, 12, 161-173. PRiBYL, A. 1947. Two new Otarionidae from the Devonian of Bohemia. Ve.stn. Krdl. Ceske Spot. Nauk. Tf. Mat.-Pfir. 1946, 1-7. REED, F. R. c. 1943. The genera of British Carboniferous trilobites. Ann. Mag. nat. Hist. 11, 10-64. RICHTER, R. and RICHTER, E. 1926. Die Trilobiten des Oberdevons, Beitrage zur Kenntnis devonischer Trilobiten, 4. Ahhandl. preuss. geol. Lamlesanst. 99, 1-314. 1939. Ueber Namuropyge n.g. und die Basisolution der Trilobiten-Glatze. Bidl. Miis. r. Hist. nat. Belg. 15, 1-29. J. MILLER Grant Institute of Geology Typescript received 12 July 1976 Mains Road Revised typescript received 4 November 1976 Edinburgh EH9 3JW THE PALAEONTOLOGICAL ASSOCIATION Notes for Authors submitting papers for publication in PALAEONTOLOGY and SPECIAL PAPERS IN PALAEONTOLOGY PUBLICATION POLICY OF THE PALAEONTOLOGICAL ASSOCIATION Scope of publications. Manuscripts on any aspect of palaeontology, including palaeoecology and stratigraphical palaeontology, will be considered for publication. Papers on Recent material may be acceptable if their palaeontological relevance is explicit. Preference is given to manuscripts with more than local significance, and review papers are particularly welcome. A high standard of illustration is a feature of the journal. The series Special Papers in Palaeontology is for papers longer than those normally accepted for Palaeontology (see below, p. 929). 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Norsk geol. Tidsskr. 51, 25-31. ELLES, G. L. 1940. The stratigraphy and faunal succession in the Ordovician rocks of the Builth-Llandrindod Inlier, Radnorshire. Q. Jl geol. Soc. Land. 95 (for 1939), 383-445. HUENE, F. von, 1958. Nachtrage zur Kenntnis von Henodus chelyops aus dem Tubingen Gipskeuper. Palaeontographica, (A) 110, 165-169. LOEBLiCH, A. R. and TAPPAN, H. 1964. Sarcodina chiefly ‘Thecamoebians' and Foraminiferida. In moore, r. c. (ed.). Treatise on Invertebrate Paleontology. New York and Lawrence, Geol. Soc. Am., pt. C, Protista 2, 1, Cl-510a; 2, C511-900. OBUT, A. M. 1964. Podtip Stomochordata. Stomokhordovye. In orlov, y. a. (ed.). Osnovy paleontologii : Ecliinodermata, Heinichordata, Pogonophora, Chaetognatlia. Nedra Press, Moscow. 279-337. [In Russian.] Synonymies should be in the following style: 1947 Beltanella gilesi Sprigg, p. 218, pi. 6, fig. 1. 1949 Beltanella gilesi Sprigg; Sprigg, p. 81, pi. 10, fig. I. 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Proofs. Authors will normally receive one proof; this proof is for the purpose of correcting printers’ errors and not for altering the wording or substance of the paper. Authors may be charged for excessive alterations. The editors will only be responsible EXPLANATION OF PLATE X This plate has been designed to show the common defects noted in plates submitted for publication. General comment : the plate lacks balance of contrast and is poorly laid out. If your plate shows any of the defects illustrated here, it should not be submitted for publication. Top row, in general. The prints do not line up along their top and bottom edges. The gap between 1 and 2 is not parallel sided or perpendicular to the margin. Note the variable size and shape of the cut-off corners to allow the insertion of figure numbers. Fig. 1 . Low contrast showing loss of detail. Note that the print is not mounted perpendicular to the margin. Fig. 2. Moderate contrast reveals greater detail. Fig. 3. Not sharply in focus, and the appearance is therefore fuzzy. Fig. 4. Negative scratched, causing lines on the print. Fig. 5. SEM. The print is marred by scan lines caused by charging, the gold coating on the background is badly cracked and the lower part of the specimen has been trimmed off. Fig. 6. SEM. This print shows excessive contrast. Also, though the illumination should appear to come from the top or top left, the print has been mounted at right angles to the desired orientation. The specimen is dirty and not worth illustrating. Fig. 7. A hair on the negative is superimposed on the glabella. Fig. 8. The background has been inexpertly painted out with Indian ink. Note the loss of ribs below the aperture and the crude painting-out around the ribs elsewhere. The print was damaged during mounting, causing artefacts near the aperture. Fig. 9. The background has been clumsily cut away using scissors. Note the damage to the outline of the ribs and local accidental inclusion of background. Fig. 10. The unevenly illuminated specimen merges with the background. PLATE X How not to make a plate 928 PALAEONTOLOGY, VOLUME 20 for author corrections notified by return of post. Whenever possible, plate proofs will be sent to the authors with the text proofs. Offprints. Fifty offprints of each paper will be sent free of charge, and the authors may purchase further copies at prices shown on the order form which will be sent with the proofs to the author (or corresponding author in the case of multi-author papers). Deposition of data. The Association makes use of the scheme run by the British Library, Lending Division, whereby publication expenses can be saved by depositing tables of data and other reference material with the British Library rather than print- ing them. 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Prepaid coupons for such purposes are held by many technical and university libraries throughout the world’). Association policy is that neither plates nor formal taxonomic data will be considered for deposition. Authors should indicate, and separate as appendices, those parts of their papers that they propose for deposition; the Publications Committee may also recommend that part of a paper should be deposited rather than be printed. Preparation of copy for deposition. Copy must be prepared by the author according to the following specifications. Editors will not undertake the preparation of copy. (i) Copy must be camera-ready. (ii) Maximum page size for text or tables in typescript or computer printout is 330 mm high x 240 mm wide, including margins. Optimum page size is A4 size. (iii) Tabular matter should be headed descriptively on the first page, with column headings recurring on each page. (iv) Prefatory text, which should contain the abstract from the parent paper, should be included. (v) All pages must be consecutively numbered. Authors with large sections for deposition are advised to consult the Secretary of the Publications Committee for further information. NOTES FOR AUTHORS 929 SPECIAL PAPERS IN PALAEONTOLOGY Preparation of papers for this series should be in the same style as for Palaeontology, Submission. Prospective authors should consult the Editors well in advance of sub- mission, supplying as much information as possible. Cost of publication. The Association’s funds for this series are limited. Authors are asked to obtain grants wherever possible. When this cannot be done by the author, the Association may require time to seek such funds. Offprints. A small number of free offprints will be supplied and further copies may be obtained at a special reduced charge. Details will be supplied at the time by the editor concerned. GRANTS IN AID OF PUBLICATION Palaeontology has no compulsory page or plate charges. However, authors are requested to seek grants in aid of publication from their institutions or from research funds, or to apply for publication costs in research grants. Some financial support is particularly welcome, and may be necessary, for long papers. Although acceptance of a paper for publication will not be dependent on the receipt of such grants, authors will appreciate that the funds available to the Associa- tion are limited. Every grant or donation will therefore directly help the Association’s publication programme. 1977 Prepared by the Piihlicaliom Committee The Palaeontological Association London THE PALAEONTOLOGICAL ASSOCIATION Annual Report of the Council for 1976 Membership and Subscriptions. The record numbers achieved in 1975 for membership, subscriptions to Special Papers in Palaeontology, and sales of publication of back parts to members via the Membership Treasurer were all surpassed in 1976. Membership reached 1,554 on 31 December 1976, an increase of 31 since 31 December 1975. There were 912 Ordinary Members, an increase of 10; 255 Student Members, an increase of 21 ; and 387 Institutional Members, as in 1975. Three hundred and eighty institutions subscribed to Palaeontology through Blackwells, maintaining the record level of 1975. These numbers were achieved despite the discouraging rise in subscription rates and cover prices on 1 January 1976, and the fall in value of sterling during the year which decreased the attractiveness of the Association’s dollar rates. Subscriptions to Special Papers were paid by 165 individual and 105 Institutional Members, increases of 18 and 7 respec- tively since 31 December 1975. In addition, 144 institutions subscribed via Blackwells’ agency, as in 1975. Sales of back parts of Palaeontology to members continued the increase of former years, from 2 1 transactions in 1975 to 34 transactions in 1976. Similar sales of Special Papers also increased, from 1 10 transactions to 134 transactions. Finance. During 1976 the Association published Volume 19 of Palaeontology at an estimated cost of £22,979 (including £2,922 postage and distribution) and Special Papers 17 and 18 at an estimated cost of £7,788. Administrative expenses have been contained. Subscriptions and sales of Palaeontology have been encouraging. The Association is extremely grateful to all institutions which have made donations; these include Birkbeck College, University of Bristol, Carnegie Trust, and the American Chemical Society. We are particularly grateful to the Royal Society for providing a gift of £1,000 and a loan of £500 in support of Special Paper 18', our ability to publish large Special Papers is dependent on such grants. Publications. Four parts of Volume 19 were published during 1976; they contained 38 papers and 4 short communications and consisted of 786 pages and 1 15 plates. Two Special Papers have been published during the year. Special Paper 17, ‘Aspects of Ammonite Biology, Biogeography, and Biostratigraphy’ was published in May 1976, and Special Paper 18 ‘Ostracoderm Faunas of the Delorme and Associated Siluro- Devonian Formations, North West Territories, Canada’ was published in December 1976. Meetings. Five meetings were held during 1976. The Association is indebted to Professor B. E. Leake and Professor W. S. Pitcher for granting facilities for the meetings at Glasgow and Liverpool respectively, to the local secretaries for those meetings, and to the leaders of the field excursions. a. The Nineteenth Annual General Meeting was held in the Lecture Theatre of the Geological Society of London on 17 March 1976. Dr. R. J. G. Savage (Bristol) delivered the Nineteenth Annual Address, on ‘Evolution in Carnivorous Mammals’. b. A Field Demonstration Meeting was organized by the Carboniferous Group on the ‘Carboniferous of the Northumberland Trough’ and led by Dr. M. R. Feeder, Dr. D. V. Lrost, Dr. D. W. Holliday, Dr. G. A. L. Johnson, and Mr. A. V. Hodgson. About sixty members attended the meeting, which was held on 23-25 April 1976. c. A Workshop on the Teaching of Palaeontology, organized jointly with the Earth Science Education Methods Group of the Geological Society of London, was held at the University of Glasgow on 22-23 May 1976. About fifty members attended. The local secretary was Dr. W. D. I. Rolfe. d. A Field Demonstration Meeting on palaeoecological techniques was held in the Boulonnais (N. France) on 5-7 November 1976 and organized by Dr. Peigi Wallace (Imperial College, London). Thirty members attended. e. The Annual Christmas Meeting on ‘Constructional and Functional Morphology’ was held at Liverpool 932 THE PALAEONTOLOGICAL ASSOCIATION University on 16-18 December 1976. About one hundred and thirty members attended, including a substantial number from overseas, particularly Germany. A field excursion to the Clitheroe area was organized to examine bioherms in the Carboniferous Limestone. The local secretary was Dr. C. R. C. Paul. Council. The following were elected members of Council for 1976-1977 at the A.G.M. on 17 March 1976; President: Professor W. G. Chaloner; Vice-Presidents: Dr. J. D. Hudson, Dr. J. M. Hancock; Treasurer: Mr. R. P. Tripp; Membership Treasurer: Dr. E. P. F. Rose; Secretary: Dr. C. T. Scrutton; Editors: Dr. L. R. M. Cocks, Dr. C. P. Hughes, Professor!. W. Murray, Professor C. B. Cox; Other Members: Dr. M. C. Boulter (Circular Reporter), Dr. C. H. C. Brunton, Dr. J. C. W. Cope, Dr. G. E. Farrow, Dr. G. P. Larwood, Dr. C. R. C. Paul, Dr. J. E. Pollard, Dr. R. E. H. Reid, Dr. R. B. Rickards, Dr. A. W. A. Rushton, Dr. E. B. Selwood, Dr. G. D. Sevastopulo, Dr. P. Toghill, Dr. P. Wallace. Circulars. Four Circulars, nos. 83-86, were distributed to Ordinary and Student Members and over one hundred Institutional Members on demand during 1976. Following the computerization of the Association’s membership list, reported last year, sale of the list to publishers for the circulation of promotional leaflets, and the distribution of such leaflets with the Circular, form an additional minor but useful source of income. Council Activities. As a result of an award from the Association’s Conservation Fund, announced last year, the Shropshire Conservation Trust has now completed the purchase of Comley Quarry. Excavations there during June 1976 resulted in the exposure of a complete new section through the important Lower and Middle Cambrian sequence of this locality. The purchase of Meadowtown Quarry is delayed by unfore- seen difficulties. During the year. Council has streamlined some of its administrative procedures. To ease the increasing work-load on the Membership Treasurer, resulting from rising membership and publication sales and changing subscription rates, the new office of ‘Institutional Councillor’ was established and Dr. C. H. C. Brunton appointed to the post with effect from 1 September 1976. (The Institutional Councillor now handles sales to and subscriptions from Institutional Members, whilst the Membership Treasurer continues to deal with records and payments relating to Ordinary and Student Members.) The new post continues the tradition of the Association whereby its business is conducted by unpaid officers acting in their spare time, so keeping administrative costs to a low level. A revision of the Association’s ‘Instructions to Authors’ for papers submitted to Palaeontology and Special Papers in Palaeontology is nearing completion, and plans are under way to improve the promotion of the sale of our journals, particularly overseas. In addition to the Association’s established annual programme of events. Council continues to review sug- gestions and opportunities for additional meetings. The organization of the International Symposium on the Devonian System to be held in Bristol in September 1978 is well advanced with some two hundred returns to the first circular. The Association will participate in the third meeting of British Geological Societies at Swansea in September 1977, and a future joint meeting is planned with the Geological Curators Group. Professor Dorothy Hill retired from her post as Overseas Representative for Australia during the year. Thanks are due to Professor Hill for her long service to the Association. Dr. B. D. Webby (University of Sydney) has been appointed to serve in her place. <■ :r«> '"4 *- ?,r » .i.ftdiii'vA' a BALANCE SHEET AND ACCOUNTS FOR THE YEAR ENDING 31 DECEMBER 1976 a 1 O (N o w-i o a^ ov ■rt r' 0^ On — ^ 'Tj- — ■ .3' ON O -'B o .£■ D. 3 OJ 5-D <>5 (L) <>3 fi o 2 i- ■c o'? CJ oo '£§ S -a S' - §« o ^ ' O &o S So ^ — Z H I (N ^ OS O ^ Os O - — fSj > O o o o H H o o o o o o S ‘S 0-3 T3 S o ~o c-/ 3 O- 3 15 O- ^ ^ ^ -a 3 *o 3 < < 3 C/3 00 O o ^ oo : ^ S' i u <3 < .3 a 5 UJ S ^ 3 « o S c3 < X) .S2 3 > 3 c/5 O ' o ' <"2 ^ s ' B i£ ^ i C a “ . OJ ^ I Cl- «u ^ . X Ci,T3 , PJ CO" 3 < 3 , cn SO O On O ON m 530 Advance payment for offprints ..... Cash at Bank: 1,045 Deposit Account ....... 4,812-28 1,149 Current Account— Sheffield ..... 7,939-48 Cost of publication of /’a/aeoH/o/ogv: 9,090 Subscriptions for 1976 ...... 17,424-96 2 I o — V) 0\ rn O O O so O O O CM O O SO so rj 1— ■ — m — Q I i c/3 Q I i .. U o O c 2 ^ Z ^ ^ c — ^ . a> 3 o 6 S . S 00^ I o c i. s o c/3 E >■ 3 § ■ SO J O w 2 35^ ■ ^ H s ON “ s On c *0 ) O o D. ' w5 3 g >.W ° O 3 3 , o i 5 : .tS O’ I U W e £ s DO r-' 1- £ 5 ^ cd o ■ o S Os 5^. On Bop XJ ® c ;:::r ^ ' ^ o CQ o g ©rs 2 . ^ ^ o xi >s o> .t; c/3 ' I « ^ rS o 3 nJ ^ D, N On I ^ £i o CJ H CO 3 . ^ o «3 o ,2^ ,/ s w) 3 X JS cd 0 H c li 1 £ c 2 ■i & • — I ,E c c 3 3 O J 3 o , Ci- O ^ X ^ Q tu 3ie (U g a 2 aj •t. o •a 5J S ^ D. — r-- so — Os On On X. 4> I *0 QJ 2 <22 ^ *o 2 S ^ (U a 3 ^ t 2 ^ “S t> O S' ^ ^ a ■Cl tC — Excess of income over expenditure .... 452 18 18,913 Balance at 31 December 1975 ..... 13,995-90 INDEX Pages 1-236 are contained in Part 1; pages 237-482 in Part 2; pages 483-714 in Part 3; pages 715-941 in Part 4. Figures in Bold Type indicate plate numbers. A Acernaspis (Eskaspis) sufferta, 125, 18, 19; (E.) wood- burnensis, 132, 19. lAhrensisporites, 14. Albian: ammonite (Ealloticeras), 793; north-west European Foraminiferida, 503. Aldabra; calcified Plectomena (blue-green algae), 33. Alethopteris lonchitica, 461, 51. Al-Furaih, A. A. F. Cretaceous and Palaeocene species of the ostracod Hornibrookella from Saudi Arabia, 483, 53-58. Algae: calcified Plectonema (a Recent Girvanella) from Aldabra, 33; Dasycladacea, 705; non-calcified from upper Silurian of mid Wales, 823. Alispira gracilis, 40. Alvin, K. L. The conifers Prenelopsis and Manica in the Cretaceous of Portugal, 387, 41-45. Ammonites: Bajocian microconch otoitids, 101; Cretaceous, 793; earliest tissotiid, 901 ; Jurassic, 675; pattern preservation, 913. Anazyga recurvirostra, 306, 37; lA. tantilla, 37. Annularia radiata, 51. Anomalocardia brasiliana, 118. Arctic Canada: Triassic spore, 581. Arenobulimina, 503; advena, 508, 59; chapmani, 508, 59; frankei, 508, 59; macfadyeni, 510, 59; cf. obliqua, 510, 59; sabulosa, 510, 59; truncata, 510, 59. Asaphus raniceps, 21, 9, 10. Ash, S. R. An unusual bennettitalean leaf from the Upper Triassic of the south-western United States, 641, 77-79. Ashgill: trilobites in Wales, 763. Asterophyllites equisetiformis, 51. Astrocrinus tetragonus, 228, 31, 32. Auslraliella cooksoniae, 183, 25. B Bajocian: microconch otoitid ammonites, 101. Bayliss, O. H. See Kennedy, W. J. and Bayliss, O. H. Belemnocystites wetherbyi, 551, 64. Bengston, S. Early Cambrian button-shaped phosphatic microfossils from the Siberian Platform, 751. Bivalves: coadaptation in the Trigoniidae, 869. Blastoids: Carboniferous of Scotland, 225. Boulter, M. C. and Wilkinson, G. C. A system of group names for some Tertiary pollen, 559. Brachiopods: Ordovician and Silurian atrypoids, 295; Stenoscismatacea from Carboniferous of Spain, 209. Brachymylus altidens, 590, 66. Brazil: Cretaceous crocodiles, 203. Bredyia, 675; crassornata, 81, 82; subinsignis, 81-84. Briggs, D. E. G. Bivalved arthropods from the Cambrian Burgess Shale of British Columbia, 595, 67-72. Britain: Carboniferous coprolites and plant debris, 59. Brongniartella, 24. Buffetaut, E. and Taquet, P. The giant crocodilian Sarcosuchus in the early Cretaceous of Brazil and Niger, 203, 28. Burbridge, P. P. See Felix, C. J. and Burbridge, P. P. C Catamites cisti, 51. Calamospora, 61, 13. Cambrian: bivalved arthropods from Burgess Shale, 595; metazoan from Burgess Shale, 623; phosphatic microfossils from the Siberian Platform, 751 ; pseud- agnostoid trilobites, 69. Camerisma (Callaiapsida) alcaldei, 211, 29; (C.) pauci- costata, 214, 29. Campanian: dinoflagellates from Montana, 179, Canada: Cambrian bivalved arthropods from British Columbia, 595; Cambrian metazoan from British Columbia, 623; entoproct-like organism from British Columbia, 833; Silurian ostracoderms from North West Territories, 661 ; Triassic spore, 581. Candona cliff endensis, 430, 46; daleyi, 432, 46. Cappetta, H. and Ward, D. J. A new Eocene shark from the London Clay of Essex, 195, 26, 27. Carboniferous: blastoids from Scotland, 225; coprolites and plant debris from Britain, 59; epiderm of Lepi- dophloios, 273; Mississippian corals, 47; ostracods, 475; plant ecology, 447; stenoscismatacean brachio- pods from Spain, 209; trilobites, 917. Carpoids: Ordovician, 529. Catazyga anticostiensis, 38; filistriata, 39; headi, 315, 37, 38; hicksi, 38. Ceratiopsis diebeli, 184, 25. Chara antennata, 1 55, 22. Charophytes: Eocene-Oligocene of the Isle of Wight, 143. Chimaeroid dentition: Oxford Clay (Jurassic), 589. Clarkson, E. N. K., Eldredge, N. and Henry, J.-L. Some Phacopina (Trilobita) from the Silurian of Scotland, 119, 18-20. Clintonellal anticostiana, 331, 40. Coadaptation: trigoniid bivalves, 869. Coignouina, 917. Conifers: Cretaceous of Portugal, 387; Cretaceous of U.S.A. and England, 715. Cooper, M. R, See Kennedy, W. J. and Cooper, M. R. Copper, P. Zygospira and some related Ordovician and Silurian atrypoid brachiopods, 295, 37-40. 938 INDEX Coprolites: Carboniferous from Britain, 59. Corallian: benthic associations from England and Normandy, 337. Corals: Mississippian, 47; significance of coiled proto- coralla, 47; structure and incremental growth in Desmophyllum from North Atlantic, 1 . Cordaitanthus sp., 460, 50. Cordaites principalis, 461, 50. Corvaspis cf. C. arctica, 669, 80. Cretaceous: Albian ammonite, 793; Albian Foramini- ferida of north-west Europe, 503; conifers from Portugal, 387; conifers from U.S.A. and England, 715; crocodiles from Brazil and Niger, 203; dino- flagellates from Montana, 179; ostracods from Saudi Arabia, 483. ICristalisporites, 13. Crocodiles: Cretaceous of Brazil and Niger, 203. Crustacea: Austropotamobius pallipes, 23, 10; Hoploparia longimana, 23, 10. Cupressinocladus valdensis, 742, 97. Cushmanidea haskinsi, 439, 47; stintoni. 440, 47; wightensis, 441. 47. Cyathaxonia tantilla, 47, 12. ICyclogranisporites, 14. Cyclonephelium distinctum, 182, 25. Cypria dorsalta, 46. Cypridopsis hessani hantonensis, 46. Cyrolexis grand, 217, 29, 30. Cylherura pulchra, 44 1 , 47. D Dalingwater, J. E. and Miller, J. The laminae and cuticular organization of the trilobite Asaphus raniceps, 21, 9, 10. Deflandrea montanaensis, 184, 25; cf. pirnaensis, 185, 25. IDenosporites, 14. Desmophyllum cristagalli, 1, 1-8. Devonian: homalonotid trilobites, 159. Dictyopyxidia sp., 182, 25. Dinoflagellates: Cretaceous of Montana, 179. Dinomischus isolatus, 834, 112. Dipoloceras bouchardianum, 105; cf. pseudaon, 105. E Echinoderms: Ordovician, 529. Echinoids: Turonian and Senonian of England, 805. Edwards, D. A new non-calcified alga from the upper Silurian of mid Wales, 823, 110, 111. Egorovitina kirssanovi, 478, 52. Eldredge, N. See Clarkson, E. N. K., Eldredge, N. and Henry, J.-L. Elliott, G. F. A consideration of the tribe Thyrso- porelleae dasyclad algae, 705. Emileia (Emileia) subcadiconica, 17; (Otoites) sp., 17; (O.) douvillei, 103, 17. Encrinurus sp., 862, 114; diabolus, 858, 114; rosenteinae, 860, 115; variolaris, 850, 113. England : Corallian benthic associations, 337 ; Cretaceous conifers, 715; Eocene shark from London Clay of Essex, 195; evolution of Palaeogene charophytes of the Isle of Wight, 143 ; Liassic ammonite from Dorset, 913; Turonian and Senonian echinoids, 805; Upper Eocene ostracods of the Hampshire Basin, 405. Eocene: charophytes from the Isle of Wight, 143; ostracod assemblages and depositional environments, 405; shark from London Clay, 195. Eoginkgoites davidsonii, 647, 77-79. Eotrigonia subundulala, 116. Epiaster, 805; laxoporus, 808, 109; michelini, 806, 107. Epiderm: Lepidophloios, 273. Europe: Albian Foraminiferida, 503. See also Britain, England, France, Portugal, Scotland, Spain, Wales. Evolution: Albian Foraminiferida, 503; carnivorous mammals, 237. F Ealloticeras, 793; proteus, 800, 104, 105; aff. proteus, 105; sp , 105. Feist-Castel, M. Evolution of the charophyte floras in the Upper Eocene and Lower Oligocene of the Isle of Wight, 143, 21, 22. Felix, C. J. and Burbridge, P. P. A new Ricciisporites from the Triassic of Arctic Canada, 581, 65. Fish : Eocene shark from Essex, 195 ; Jurassic chimaeroid, 589; Silurian ostracoderms from Canada, 661. Flourensina intermedia, 508, 59. Foraminiferida: Albian of north-west Europe, 503. Erammia, 847; arctica, 115. France: Corallian benthic associations from Normandy, 337. Erenelopsis, 387, 41-44; alata, 388, 41, 42, 730, 89, 92; occidentalis, 402, 45; oligostomata, 392, 43; ramo- sissima, 736, 93-97. Fiirsich, F. T. Corallian (Upper Jurassic) marine benthic associations from England and Normandy, 337. G Gass, K. C. See Tripp, R. P., Temple, J. T. and Gass, K. C. Gavelinella, 503; baltica, 514, 60; cf. baltica, 514, 60; cenomanica, 516, 60; intermedia, 516, 60; intermedia var. A, 516, 60; rudis, 516, 60. Girvanella, 33. Gow, C. E. Tooth function and succession in the Triassic reptile Procolophon trigoniceps, 695. Grambastichara tornata, 154, 22. Gramm, M. N. A new family of Palaeozoic ostracods, 475, 52. Grovesichara distorta, 146, 21. H HadroblastusG) benniei, 234, 32. Hallucigenia sparsa, 624, 73-76. Harland, R. Dinoflagellate cysts from the Bearpaw Formation (? upper Campanian to Maastrichtian) of Montana, 179, 25. Harrischara tuberculata, 150, 21; vasiformis, 150, 21; v.-tuberculata, 152, 21. Hazelina indigena, 48. INDEX 939 Hedbergella, 503; brittonensis, 519, 61; delrioensis, 519, 61; infracretacea, 519, 61; planispira, 520, 61. Henry, J.-L. See Clarkson, E. N. K., Eldredge, N, and Henry, J.-L. Homalonotid trilobites: classification and phylogeny, 159. Hornibrookella. 483; cuspidata, 490, 53; cyclifossata, 485, 53; cyclopea, 486, 54; divergens, 491 , 55; episcelis, 492, 56; posterisella, 496, 57; qidnquecellulosa, 498, 58. 1 ? Idiocythere bartoniana, 47. lowacystis sagittaria, 539, 62-64. J Jell, J. S. See Sorauf, J. E. and Jell, J. S. Jones, B. See Loeffler, E. J. and Jones, B. Jurassic: ammonites, 675; Bajocian otoitid ammonites, 101 ; chimaeroid fish, 589; Corallian benthic associa- tions from England and Normandy, 337. K 1 Kallostrakon, 672, 80. Keen, M. C. Ostracod assemblages and the depositional environments of the Headon, Osborne, and Bembridge Beds (Upper Eocene) of the Hampshire Basin, 405, 46-49. Kennedy, W. J. and Bayliss, O. H. The earliest tissotiid ammonite, 901, 120. Kennedy, W. J. and Cooper, M. R. The micromorph Albian ammonite Falloticeras Parona and Bonarelli, 793, 104, 105. Kolata, D. R., Strimple, H. L. and Levorson, C. O. Revision of the Ordovician carpoid family lowa- cystidae, 529, 62-64. L Laevitrigonia manseli, 119. Lagenicula subpilosa, 60, 13. Lepidodendron mannabachense , 33. Lepidophloios, 273, 33-36; acadianus, 289, 36; acerosus, 280, 34, 35; grangeri, 286, 36; laricinus, 275, 33, 34; macrolepidotus, 284, 35. Levorson, C. O. See Kolata, D. R., Strimple, H. L. and Levorson, C. O. Liassic: ammonite from Dorset, 913. Loeffler, E. J. and Jones, B. Additional late Silurian ostracoderms from the Leopold Formation of Somerset Island, North West Territories, Canada, 661, 80. Loxoconcha sp., 47. Lycospora, 60, 14. Lyriomyophoria elegans, 119. M Maastrichtian : dinoflagellates from Montana, 179. McNamara, K. J. See Ward, D. J. and McNamara, K. J. Macurda, D. B., Jun. Two Carboniferous blastoids from Scotland, 225, 31, 32. Mammals: evolution of carnivorous forms, 237. Manica, 387, 44; parceramosa, 397, 44. Manley, E. C. Unusual pattern preservation in a Liassic ammonite from Dorset, 913. Mariopteris mwicata, 51; art', sauveri, 461, 51. Martinez-Chacon, M. L. New Carboniferous steno- scismatacean brachiopods from Oviedo and Leon, Spain, 209, 29, 30. Megascvliorhinus cooperi, 196, 26, 27; miocaenicus, 198, 27. Megalrigonia conocardiifonnis, 119. Micraster, 805; coranguimim rostratus, 809, 108; c. simpsoni, 810, 109; corbovis, 810, 106; decipiem, 810, 108; leskei, 812, 108; normanniae, 812, 107; wesllakei, 814, 109. Microfossils : Cambrian from the Siberian Platform, 751. Micromorphs: Falloticeras, 793. Miller, J. Synonymy of the Carboniferous trilobites Namuropyge and Coignouina, 917. Miller, J. See also Dalingwater, J. E. and Miller, J. Mississippian : corals, 47. Mojsisovicsia, 105; ventanillensis, 105. Morris, S. C. A new metazoan from the Cambrian Burgess Shale of British Columbia, 623, 73-76. Morris, S. C. A new entoproct-like organism from the Burgess Shale of British Columbia, 833, 112. Myebiocystites crossmani, 554, 64; natus, 553, 64. Myopliorella clavellata, 119. N Nalivkinia (Nalivkinia) gruenewaldtiaeformis, 326, 40. Namuropyge, 917. Neoagnostus araneavelatus, 16; aspidoides, 16; bilobus, 16; canadensis, 16; davits, 16; [Flyperagnostus] binodosus, 16; [Trinodus] priscus, 16. Neocyprideis colwellensis, 434, 48. Neolrigonia margaritacea, 116, 119. Neuropteris cf. loslii, 51; pseudogigantea, 461, 51. Niger: Cretaceous crocodiles, 203. Nitellopsis (Tectochara) aff. aemula, 146, 22; (T.) latispira, 22. Nomenclature: Tertiary pollen, 559. North Atlantic: Recent ahermatypic coral, 1. Notes for authors, 921. O Oedogonium sp., 11. Oligocene: charophytes from the Isle of Wight, 143. Ordovician: atrypoid brachiopods, 295; carpoids, 529; homalonotid trilobites, 1 59 ; pseudagnostoid trilobites, 69; trilobite laminae and cuticle, 21. Ostracoderms: Silurian from Canada, 661. Ostracods: Cretaceous and Palaeocene species from Saudi Arabia, 483 ; new Palaeozoic family, 475 ; Upper Eocene ecology in Hampshire Basin, 405. Oxfordian: see Corallian. Oxytropidoceras, 105. 940 INDEX P Palaeocene; ostracods from Saudi Arabia, 483. Palaeocystodinium golzowense, 1 86, 25. Palaeoecology : Carboniferous plant assemblages, 447; Corallian benthic associations, 337 ; Eocene ostracods, 405. Palaeopehdiniiim pyrophorum, 188, 25. Palaeozoic; new family of ostracods, 475. Parsons, C. F. Two new Bajocian microconch otoitid ammonites and their significance, 101, 17. Pentlandella haswelli, 39; pentlandica, 39; tenuistriata, 321, 39. Perspicaris dictynna, 597, 67-69; recondita, 606, 69-72. Plaesiacomia hughesi, 163, 23; vacuvertis, 164, 23, 24. Plant debris: in Carboniferous coprolites from Britain, 59. Plants : Carboniferous ecology, 447 ; Cretaceous conifers from Portugal, 387; Cretaceous conifers from U.S.A. and England, 715; epiderm of Lepidophloios, 273; pre-depositional formation of leaf impressions, 907; Triassic bennettitalean leaffrom south-western U.S.A. , 641 ; Triassic spore from Canada, 581. Platycoryphe dyaulax, 169, 24. Pteclonema gloeophilum, 33, 11. Podowrinella siraitonensis, 134, 20. Pokornyella osnabrugensis, 48. Pollen: Tertiary group names, 559. Portugal; Cretaceous conifers, 387. Powysia bassettii, 824, 110, 111. Price. D. Species of Tretaspis (Trilobita) from the Ashgill Series in Wales, 763, 98-103. Price, R. J. The evolutionary interpretation of the foraminiferida Arenobulimina, Gavelinella, and Hedbergella in the Albian of north-west Europe, 503, 59-61. Procolophon trigoniceps, 695. Prosogvrotrigonia timorensis, 118. Pseudagnostus, 69, 15, 16; (Pseudagnostina) contracia, 15; (Pseudagnostus) ampullatus, 15; (P.) bulgosus, 15; (P.) communis, 15; (P.) cyclopyge, 15; (P.) josepha, 15; (Sulcatagnostus) securiger, 15. Pseudofrenelopsis parceramosa, 720, 85-87; varians, 726, 88-91. Pseudotissotia inopinata, 902, 120; (P.) galliennei, 120. Psilochara aff. conspicua, 21. Psilotrigonia beesleyana, 118. Pterotrigonia etheridgi. 118. ? Pustulatisporites, 14. R Raistrickia. 14. Recent: algae from Aldabra, 33; structure and growth in North Atlantic coral, 1. Reptiles: Triassic, 695. Rhaptagnostus bifax, 16; clarki, 15; convergens, 16. Ricciisporites, 581; umbonatus, 582, 65. Riding, R. Calcified Plectonema (blue-green algae), a Recent example of Girvanella from Aldabra Atoll, 33, 11. Ruggieria semireticulata, 48. Rutitrigonia dunscombensis, 118. S Samaropsis pyriformis, 460, 51. Sando, W. J. Significance of coiled protocoralla in some Mississippian horn corals, 47, 12. Sarcosuchus, 203; hartti, 203, 28; imperator, 203, 28. Saudi Arabia: Cretaceous and Palaeocene ostracods, 483. Savage, R. J. G. Evolution in carnivorous mammals, 237. 1 Savitrisporites, 14. Scalenocystites strimplei, 547, 63, 64. Schopfipollenites, 14. Schuleridea (Aequacvtheridea) perforata headonensis, 438, 49. Scotland; Carboniferous blastoids, 225; Carboniferous plants from Strathclyde, 447; Silurian phacopinid trilobites, 1 19. Scott, A. C. Coprolites containing plant material from the Carboniferous of Britain, 59, 13, 14. Scott, A. C. A review of the ecology of Upper Carboni- ferous plant assemblages, with new data from Strath- clyde, 447, 50, 51. Senegalinium magnificum, 188, 25; tricuspis, 188, 25. Senior, J. R. The Jurassic ammonite Bredyia Buckman, 675, 81-84. Senonian; echinoids from England. 805. Shark: Eocene of Essex, 195. Shergold, J. H. Classification of the trilobite Pseud- agnostus, 69, 15, 16. Silurian: atrypoid brachiopods, 295; homalonotid trilobites, 159; non-calcified alga from mid Wales, 823; ostracoderms from Canada, 661; phacopinid trilobites from Scotland, 119; Encrinurus species, 847. Sorauf, J. E. and Jell, J. S. Structure and incremental growth in the ahermatypic coral Desmophyllum cristagaUi from the North Atlantic, 1, 1-8. Spain: Carboniferous stenoscismatacean brachiopods, 209. Sphaerochara subglobosa, 148, 21. Sphenophyllum cf cuneifolium, 461, 51. Spicer, R. A. The pre-depositional formation of some leaf impressions, 907. Spores: Carboniferous from Britain, 59. Stanley, S. M. Coadaptation in the Trigoniidae, a remarkable family of burrowing bivalves, 869, 116- 119. Stenoscisma winkleri, 2 1 8, 29, 30. Stokes, R. B. The echinoids Micraster and Epiaster from the Turonian and Senonian of England, 805, 106-109. Strimple, H. L. See Kolata, D. R., Strimple, H. L. and Levorson, C. O. Synonymy: Carboniferous trilobites, 917. T Taquet, P. See Buffetaut, E. and Taquet, P. Temple, J. T. See Tripp, R. P., Temple, J. T. and Gass, K. C. Tertiary: pollen nomenclature, 559. Thomas, A. T. Classification and phytogeny of homalonotid trilobites, 159, 23, 24. INDEX 941 Thomas, B. A. Epidermal studies in the interpretation of Lepidophloios species, 273, 33-36. Tolypelepis leopoldensis, 664, 80. Trachycardium egmontianum, 1 18. Tretaspis, 763; brachystichus, 779, 101, 102; cf. calcaria 786, 103; cf. distichus, 781, 102, 103; hadelcmdica, 779, 101, 102; cf. latilimhus, 781, 102, 103; moeldenensis, 764, 98, 99; m. moeldenensis, 770, 99, 100; aff. radialus, 775, 101; cf. radialis, 772, 100; cf. sortita, 784, 103; sp. indet. A, 778, 101; sp. indet. B, 785, 103. Triassic: bennettitalean leaf from south-western U.S.A., 641 ; reptile dentition, 695; spore from Arctic Canada, 581. Trigonia papillata, 117. Trigonocarpus sp., 51. Trilobites: Ashgill Series in Wales, 763; Carboniferous, 917; classification and phylogeny of Homalonotidae, 159; classification of Pseudagnostus, 69; laminae and cuticular organization, 21; Silurian, 847; Silurian Phacopina from Scotland, 119. Trilobiticeras (Emileites) malenotatus, 17; (T.) cricki, 106, 17. Trimerus cylindricus, 24. Tripp, R. P., Temple, J. T. and Gass, K. C. The Silurian trilobite Enchnurus variolaris and allied species, with notes on Erammia, 847, 113-115. Tuberculatisporites mammilarius, 60, 13. Turonian; echinoids from England, 805. Tuvaella rackovskii, 323, 39. Tuzoia? parva. 618, 72. U U.S.A.: Cretaceous conifers, 715; dinoflagellates from Montana, 179; Triassic bennettitalean leaf, 641. U.S.S.R.: Cambrian phosphatic microfossils from Siberian Platform, 751. V Vaiigonia (V.) literata, 117. Virgatocypris edwardsi, 47. W Wales: Ashgill trilobites, 763; non-calcified alga from upper Silurian, 823. Ward, D. J. See Capetta, H. and Ward, D. J. Ward, D. J. and McNamara, K. J. Associated dentition of the chimaeroid fish Brachymylus altidens from the Oxford Clay, 589, 66. Watson, J. Some Lower Cretaceous conifers of the Cheirolepidiaceae from the U.S.A. and England, 715, 85-97. Wilkinson, G. C. See Boulter, M. C. and Wilkinson, G. C. Y Yaadia nodosa, 117. Z Zygatrypa mica, 37; paupera, 310, 37. Zygospira, 295; modesta, 303, 37; hchmondensis, 37. THE PALAEONTOLOGICAL ASSOCIATION The Association was founded in 1957 to further the study of palaeontology. It holds meetings and demonstrations as well as publishing Palaeontology and Special Papers in Palaeontology. Membership is open to individuals and to institutions on payment of the appropriate annual subscription : Institutional membership .... £25-00 (U.S. $50.00) Ordinary membership .... £8 00 (U.S. $16.00) Student membership .... £5 00 (U.S. $10.00) There is no admission fee. Institutional membership is only available by direct application, not through agents. 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Hughes, Department of Geology, Sedgwick Museum, Cambridge CB2 3EQ Professor J. W. Murray, Department of Geology, The University, Exeter EX4 4QE Professor C. B. Cox, Department of Zoology, King’s College, Strand, London WC2R 2LS Dr. M. G. Bassett, Department of Geology, National Museum of Wales, Cardiff CFl 3NP Other Members of Council Dr. M. C. Boulter, London Dr. P. J. Brenchley, Liverpool Dr. C. H. C. Brunton, London Dr. J. C. W. Cope, Swansea Dr. G. E. Farrow, Glasgow Dr. R. A. Fortey, London Dr. G. P. Larwood, Durham Dr. S. C. Matthews, Bristol Dr. I. E. Penn, London Dr. R. E. H. Reid, Belfast Dr. R. B. Rickards, Cambridge Dr. E. B. Selwood, Exeter Dr. G. D. Sevastopulo, Dublin Dr. P. Toghill, Church Stretton Overseas Representatives Australia: Professor B. D. Webby, Department of Geology, Sydney University, Sydney, N.S.W., 2006 Canada : Dr. B. S. Norford, Institute of Sedimentary and Petroleum Geology, 3303-33rd Street NW., Calgary, Alberta India : Professor M. R. Sahni, 98 Mahatma Gandhi Marg, Lucknow (U.P.), India New Zealand: Dr, G. R. Stevens, New Zealand Geological Survey, P.O. Box 30368, 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, University of California, Berkeley 4, California Eastern U.S. A. : Professor J. W. Wells, Department of Geology, Cornell University, Ithaca, New York South America : Dr. O. A. Reig, Departamento de Ecologia, Universidad Simon Bolivar, Caracas 108, Venezuela Palaeontology VOLUME 20 PART 4 CONTENTS Some lower Cretaceous conifers of the Cheirolepidaceae from the U.S.A. and England J. WATSON Early Cambrian button-shaped phosphatic microfossils from the Siberian Platform S. BENGTSON Species of Tretaspis (Trilobita) from the Ashgill Series in Wales D. PRICE The micromorph Albian ammonite Falloticeras Parona and Bonarelli W. J. KENNEDY and M. R. COOPER The echinoids Micr aster and Epiaster from the Turonian and Senonian chalk of England R. B. STOKES A new non-calcified alga from the upper Silurian of mid Wales D. EDWARDS A new entoproct-like organism from the Burgess Shale of British Columbia S. CONWAY-MORRIS The Silurian trilobite Encrinurus variolaris and allied species, with notes on Frammia R. P. TRIPP, J. T. TEMPLE and K. C. GASS Coadaptation in the Trigoniidae, a remarkable family of burrowing bivalves S. M. STANLEY The earliest tissotiid ammonite W. J. KENNEDY and O. H. BAYLISS The pre-depositional formation of some leaf impressions R. A. SPICER Unusual pattern preservation in a Liassic ammonite from Dorset E. C. MANLEY Synonymy of the Carboniferous trilobites Namuropyge and Coignouina J. MILLER Notes for authors submitting papers for publication in Palaeontology and Special Papers in Palaeontology Palaeontological Association Report and Accounts for 1976 Index to Volume 20 715 751 763 793 805 823 833 847 869 901 907 913 917 921 931 937 Printed in Great Britain at the University Press, Oxford by Vivian Ridler, Printer to the University o r: O ■’^i^"' CJ x;^ai£5^>^ Q R I es^smithsonian“'institution NoiiniiiSNi~'NviNosHims S3iavdan’^LiBRARi Es^ Smithson) z [3 z [: > 2 r- 2 ^ #4 liSNi NviNOSHilws SBiavyan libraries Smithsonian institution NoiiniiiSNi nvinoshii: ^ ^ ^ 5 ■* ^ ^ Z * 00 2 z -I d z H z z (/) o z >■ S: .\r’ ^ 2 • > z to ' z CO '■'“ z RIES SMITHSONIAN INSTITUTION NOliniliSNI _ NVINOSHII WS SaiaVaaiT LIBRARIES SMITHSONI, (O ::= 2 \ ^ ^ to z liSNI NVINOSHillAiS SaiBVaail LIBRARIES SMITHSONIAN INSTITUTION NOliniliSNI NVINOSHIII ^ r- _ z r- RIES SMITHSONIAN INSTITUTION NOliniliSNI NVlNOSHillMS Saiavaail LIBRARIES SMITHSONI 3> nWjuis^ * Z — CO liSNi NviNOSHilws saiHvaa CO X I Z CO Z CO n LIBRARIES SMITHSONIAN INSTITUTION NOliniliSNI NVINOSHil ~ CO ~ CO — . _ ✓'^C* LiJ - _ /^v\SOa7!\ 1 1 1 . — TCjcvaT^^ CO o z RIES SMITHSONIAN INSTITUTION NOliniliSNI NVINOSHillAiS S3iavaail LIBRARIES SMITHSONI 2. •“ Z <2 y z I- 2 liSNI NVINOSHimS S31HVaan LI 2 CO Z I i i fcii - m z m to ' = CO BRARIES SMITHSONIAN INSTITUTION NOliniliSNI NVINOSHil ^ ^ z » to z ” ■ ^ § ■%% - » § ^ Z . /■■' _ z _ R I ES”'SMITHSONIAN INSTITUTION NOliniliSNI _ NVINOSHil WS" S 3 I H V a a IT LIBRARIES SMITHSONI CO z to \ to — CO > Z liSNi NviNOSHiiws saiavaan libraries smithsonian institution NoiiniiisNi nvinoshii I O XQy p c>^ _ O q ^ O ITUTION NOIinillSNl“'NVlNOSHillAIS S 3 I d V H 8 1 1 L I B R A R I E S^ SMITHS0NIAN“*1NST1TUTI0N MOlinj 2 r*, 2 r- 2 []^ 2 CD \ ^ :aD m ^ m Xl^osv^}:/ (/) ' “ c/> _ c/^ BRARIES SMITHSONIAN INSTITUTION NOIinillSNI NVINOSHIIIAIS SBIdVdail LI - CD Z. 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