i BULLETIN OF (ory THE BRITISH MUSEUM a (NATURAL HISTORY) GEOLOGY VOL. XKV 1967-1968 TRUSTEES OF THE BRITISH MUSEUM (NATURAL HISTORY) LONDON: 1970 DATES OF PUBLICATION OF THE PARTS No. No. No. No. No. No. ANEW A 26th May 13th June 24th November 12th January toth March 14th May PRINTED IN GREAT BRITAIN BY ALDEN & MOWBRAY LTD AT THE ALDEN PRESS, OXFORD 1967 1967 1967 1968 1968 1968 CONTENTS GEOLOGY VOLUME XV The palaeontology and stratigraphy of the lower part of the Upper Kimmeridge Clay of Dorset. J.C. W. Cope The correlation and trilobite fauna of the Bedinan Formation (Ordovician) in south-eastern Turkey. W.T. DEAN Burrows and surface traces from the Lower Chalk of southern England. W. J. KENNEDY A new Tempskya from Kent. M. E. J. CHANDLER Colonial Phillipsastraeidae from the Devonian of south-east Devon, England. C. T. ScRUTTON Some Strophomenacean brachiopods from the British Lower Silurian. L. R. M. Cocxs Index to Volume XV Ys "= 25 MAY. 1967 _ BULLETIN OF . (NATURAL HISTORY) Vol. 15 No. 1 hag LONDON: 1967 moe PALAEONTOLOGY AND STRATIGRAPHY OF tak EOW ERY PART OF THE UPPER KVVibRipGE CLAY OF DORSET BY eu, COPE, | Department of Geology, University College, ‘Swansea Pp. 1-79; 33 Plates; 12 Text-figures BULLETIN OF THE BRITISH MUSEUM (NATURAL HISTORY) GEOLOGY Vol. 15 No. 1 LONDON: 1967 Dae BULLE DEN (On ore BR ia Sis vuUisi WAVE (NATURAL HISTORY), instituted im 1949, is issued in five series corresponding to the Departments of the Museum, and an Historical series. Parts will appear at irregular intervals as they become veady. Volumes will contain about three or four hundred pages, and will not necessarily be completed within one calendar year. In 1965 a separate supplementary series of longer papers was instituted, numbered serially for each Department. This paper is Vol. 15, No. 1 of the Geological (Palaeontological) series. The abbreviated titles of periodicals cited follow those of the World List of Scientific Periodicals. World List abbreviation Bull. Br. Mus. nat. Hist. (Geol.). © Trustees of the British Museum (Natural History) 1967 BRU Sa SOw THE BRITISH MUSEUM (NATURAL HISTORY) Issued 26 May, 1967 Price £4 15s. fae PALAEONTOLOGY AND STRATIGRAPHY OE LOW ERCP ARI.OF THE: UPPER RIMMERTDGE CLAY OF DORSET By J. C. W. COPE CONTENTS Page I. INTRODUCTION : : ; : : : é c 4 Il. THE KIMMERIDGE SECTION : : 5 : : : : 5 III. THE NON-AMMONITE FAUNA : 9 : : : é : 10 IV. THE AMMONITE FAUNA. 6 c : : ‘ 3 : II (a) INTRODUCTION : : : ‘ : : i II (b) SYSTEMATIC DESCRIPTIONS : : j : : : 12 Genus Gravesia Salfeld 0 é : : : : 12 Gravesia gigas (Zieten) . : : : : : 12 G. cf. gravesiana (d’Orbigny) . : : ; : 14 Genus Pectinatites Buckman F : : c . 14 Sexual Dimorphism . : : é ; : 15 Interpretation of Pectinatites . c ° : : 18 The Origins of Pectinatites j : é : é 22 Subgenus Arkellites nov. F F ‘ : 24 Pectinatites (Arkellites) Pyimatie 5a, nov. . : : 2 P. (A.) cuddlensis sp. nov. 6 é 6 : : 26 P.(A.) damoni sp. nov. . , : : : > 28 P. (A.) hudlestoni sp. nov. ‘ é : : 29 Subgenus Vivgatosphinctoides Neaverson é ‘ : 30 Pectinatites (Virgatosphinctoides) elegans sp. nov. : 31 P. (V.) elegans coynigey subsp. nov. . : . ; 33 P. (V.) scitulus sp. nov. . é : ; : : 34 P. (V.) decovosus sp. nov. . ; : : : 5 36 P. (V.) major sp. nov. : : : : : : 37 P. (V.) clavellisp. nov. . : F : j : 39 P.(V.) smedmorensis sp. nov. . ; : ; P 41 P. (V.) laticostatus sp. nov. ; : c : : 43 P. (V.) grandis (Neaverson) ‘ : : ; 44 P. (V.) grandis accelevatus subsp. nov. : : F 45 P. (V.) woodwardi (Neaverson) . : : : : 45 P. (V.) wheatleyensis (N eaverson) : : ; : 40 P. (V.) wheatleyensis minor subsp. nov. 6 ; ‘ 47 P. (V.) wheatleyensis delicatulus (Neaverson) : i 48 P. (V.) pseudoscruposus (Spath) 5 ; g ‘ 49 P. (V.) veisiformis sp. nov. ; : : 50 P. (V.) veisiformis densicostatus eanee nov. : : 53 P. (V.) abbreviatus sp. nov. : : é ‘ ; 54 P. (V.) donovani sp. nov. . : é ‘ ; ; 55 P. (V.) magnimasculus sp. nov. : : E . 56 P. (V.) encombensis sp. nov. . : : : : 57 GEOL. 15, I. I 4 UPPER KIMMERIDGE CLAY OF DORSET Page Subgenus Pectinatites Buckman . ; : 59 Pectinatites (Pectinatites) inconsuetus 5. nov. : ‘ 59 P. (P.) eastlecottensis (Salfeld) . : : . ; 60 P. (P.) cf. groenlandicus (Spath) : : : : 61 P. (P.) cornutifey (Buckman) . : : : : 62 P. (P.) naso (Buckman) . 62 Genus Pavlovia llovaisky, subgenus Paani Buckman 63 Pavlovia (Pavavirgatites) cf. pavavirgatus (Buckman) . 63 V. EVOLUTION OF THE AMMONITES - 6 : c 0 : 64 VI. THE AMMONITE ZONES : ; E 66 Pectinatites (Viyeutoupiananies) alewans Zone ; E 66 P. (V.) scitulus Zone : é : 5 0 j 68 P. (V.) wheatleyensis Zone : : : : ; 69 P. (Arkellites) hudlestont Zone . : : 5 : 69 P. (Pectinatites) pectinatus Zone é : ; ; 70 VII. CORRELATIONS 0 : : : . : : : : 70 (a) Great Britain : 0 ? : : ‘ : : 70 (b) The Boulonnais . . : : : : 72) (c) East Greenland (Milne ievadl) : : 5 : ‘ 73 (d) Southern Germany (Franconia) ; ‘ : : 73 (e) Russia (Basin of the Ural and Ilek Rivers) : : : 75 VIII. REFERENCES . F : : a . : : 5 : 76 SYNOPSTS Re-examination of the lower part of the Upper Kimmeridge Clay of the type section at Kim- meridge, Dorset, has involved detailed collecting and re-measurement of the succession. The ammonite fauna of some 465 ft. of these beds is described. The ammonites belong to three subfamilies ; three genera are represented, and descriptions are given of three subgenera (one new) ; twenty-eight species (seventeen new) ; and five sub- species (four of them new). Sexual dimorphism is recognized in one genus, and is believed to be of a unique type. A revised zonal scheme is proposed, and correlations are suggested with Northern France, Greenland, and other areas of Britain. Comparisons are made with the ammonite fauna of other extra-British areas. The fauna of the Lower Tithonian rocks of Germany is shown to be quite distinct from that of the Upper Kimmeridgian of Britain, such similarities as exist being entirely due to homeomorphy. I. INTRODUCTION ExIsTInG knowledge of the Upper Kimmeridgian ammonite faunas of Britain is very imperfect. The research work which forms the basis of this account is the first stage of a planned research project, in the course of which it is proposed to study these rocks and their faunas over the whole of Britain. The lower Kimmeridgian fauna of Britain is comparatively well known and it was, therefore, considered that the best way to carry out this work was to begin at the base of the Upper Kimmeridgian (the base of the present Gravesia Zones) and work upwards to the Portlandian.! The scope of the first part of the work embraces the Gravesia, “ Subplanites”’ and basal Pectinatites Zones of the type-section. 1 The Middle Kimmeridgian of Arkell (1956: 21) has, as a result of the conclusions presented herein, no real standing. It seems most appropriate to have, therefore, two subdivisions of the Kimmeridgian Stage, the line between them being drawn at the top ‘of the Aulacostephanus autissiodorensis Zone. UPPER KIMMERIDGE CLAY OF DORSET 5 Prior to 1913 most of the ammonites from the British Upper Kimmeridgian were known under the name of Ammonites biplex—a name which embraced practically all Upper Jurassic perisphinctid ammonites. In 1913 Salfeld identified some of the British Upper Kimmeridgian ammonites with Pavlow’s genus Vzirgatites. Neaverson (1925) showed that these ammonites were not related to the Russian Volgian forms as Salfeld had supposed. Neaverson’s work, valuable though it was, fell far short of monographing the whole ammonite fauna from these beds. Neaverson did not undertake comprehensive collecting from the type-section in Dorset, which surely must be the basis for zonal subdivision. The sequence there is a thick one, and as far as is known, complete. In contrast, the sections in the Oxford district, taken by Neaverson as the basis for his zonal scheme, are incomplete and very much attenuated. As a result, parts of his zonal scheme are unsatisfactory. Spath in the early 1930’s made a collection from the Kimmeridge section (now housed in the British Museum (Natural History)), and although this was never described, references are made to it in several of his papers (e.g. 1935 : 73). He identified Neaverson’s genera Allovirgatites and Virgatosphinctoides with his genus Subplanites, proposed in 1925 for a group of ammonites occurring in Franconia; he later identified other British forms with the Tithonian genus Lithacoceras; and as a result, correlations became established between Britain and Germany based on these genera. These correlations were followed among others by Arkell (1956), and have now become generally accepted. The collections from Dorset now to be described, however, establish beyond doubt that the British Upper Kimmeridgian and German Tithonian forms are not identical, and these previous correlations are thus without real value. Many colleagues and friends have been of invaluable assistance in providing helpful suggestions and criticisms. I am particularly indebted in this respect to Professor D. T. Donovan, Dr. J. H. Callomon, and Dr. A. Zeiss. The receipt of a Research Studentship from the former Department of Scientific and Industrial Research, a grant from the British Council under the Younger Research Workers Interchange Scheme, and financial assistance from the University College of Swansea are gratefully acknowledged. Il. THE KIMMERIDGE SECTION The Kimmeridge Clay is the oldest formation exposed on the Isle of Purbeck. It appears as a long strip, approximately six miles in length and usually less than a mile wide, in the core of the Purbeck Anticline. To the north the steep escarpment of the Portland Stone effectively isolates this relatively low-lying land. The village of Kimmeridge is situated in a hollow beneath this escarpment. The outcrop of the Kimmeridge Clay on the northern limb of the Purbeck Anticline occurs in a military zone extending five miles westwards from Kimmeridge, and is for this reason inaccessible. Eastwards from Kimmeridge Bay, however, the section is well displayed for over three miles on the southern limb of the anticline. The sea erodes at a substantial rate the relatively soft shales which comprise the bulk of the succession, but has little effect on the occasional cementstone bands which stretch 6 UPPER KIMMERIDGE CLAY OF DORSET out from the base of the cliffs to form the Kimmeridge Ledges, presenting a con- siderable hazard to shipping. The cliffs, which are seldom more than 150 ft. in height, are precipitous and crum- bling. A constant trickle of shale debris down the cliffs builds up piles of talus at their foot. Occasional larger falls bring down large pieces of the cementstone bands which litter the shore at the cliff base, and break the force of the waves. It is generally only at high spring tides that the sea can reach the foot of the cliffs. At the foot of the beach at low tide small ledges or reefs of shale are exposed, and these are the only places where fossils can be satisfactorily collected. The part of the Kimmeridge section described herein embraces parts of the Kim- CLAVELL HEN CUDDLE TOWER CLIFF GRE CEMENTsTone YELLOW Lepge ese CLAVELL’S ROPE rae HARD HEA ROPE LAKE HEAD STONE BAND SPUR BELOW FRESHWATER SWYRE HEAD STEPS FRESHw, WHITE BAND sues STONE “BaD Fic. 1. Section of the cliffs from the eastern end of Kimmeridge Bay to Freshwater Steps. Modified after Arkell 1947 : 75. UPPER KIMMERIDGE CLAY OF DORSET 7 meridge Clay, whose faunas have hitherto been very imperfectly known. The lowest horizon from which collections have been made is the cementstone band which forms a prominent reef on the foreshore at the western end of Hen Cliff. This bed marks, in the Kimmeridge section, the top of the Aulacostephanus autis- siodorensis Zone, and therefore forms the junction between the Lower and Upper Kimmeridge Clay. The highest horizon studied is some twenty feet above the Freshwater Steps Stone Band. It is proposed to describe, at a later date, the highest beds of the Kimmeridge Clay, lying above this latter horizon and upwards to the Portlandian rocks. This section has been re-measured in detail, using direct measurement where pos- sible, supplemented by data acquired using an Abney level to measure the thicker lithological units, and to fix the position of the shale ledges relative to the nearest marker horizon. The system of bed numbering used is that of Blake (1875 : 198-199) who was the first to make a detailed description of this section. Although Blake numbered his beds from the top downwards (thus Bed 1 was the last to be deposited), his bed numbers are for the most part well-defined. It was found that Blake’s measurements were substantially correct, but there are several quite considerable errors, some being perpetuated by Arkell (1947 : 71-72). In the description given below, only major lithological units are described. The stratigraphical range of a species may be found more accurately by reference to the systematic description of the species, or the section on the zonal stratigraphy. Blake’s Bed Number ft. in. Pectinatites (Pectinatites) pectinatus Zone 9 Shales. : ‘ : : : : : 2620 ) Pectinatites (Pectinatites) naso, P. (P.) cornutifer, Pavlovia (Paravirgatites) paravirgatus, Ostrea bononiae, Discina latissima. Io Freshwater Steps Stone Band . : : : ce. 3 II Shales ei: ‘ 5 : : : 5 : =) 29 ) Pectinatites (Pectinatites) cornutifer, P. (P.) groenlandi- cus, P. (P.) eastlecottensis, P. (P.) inconsuetus, Ostrea bononiae, O. solitaria, Protocardia morinica, Discina latissima. 12 pars Middle White Stone Band . . . ‘ ; cee | 6 12 pars— Shales and mudstones : : 5 F : a 4) 4 20 pars Pectinatites (Pectinatites) cf. eastlecottensis, P. (? Arkel- lites) sp. indet., Ostrea sp. 20 pars White Stone Band . ; : : : ; s 38 0) 8 Blake’s Bed Number 20 pars 26 pars 26 pars 26 pars 26 pars 26 pars 26 pars 27 pars 27 pars 27 pars UPPER KIMMERIDGE CLAY OF DORSET ft. Pectinatites (Arkellites) hudlestoni Zone Shales, mudstones, hard“ dicey’”’ bands . ; : 51 Pectinatites (Virgatosphinctoides) encombensis, P. (V.) magnimasculus, P. (Arkellites) hudlestoni, Lucina miniscula, Pyrotocardia morinica, Ostrea bononiae, Discina latissima, Ichthyosaurus sp. Basalt Stone Band . : 3 : : : ee Inoceramus expansus, Ostrea sp. “Dicey’’mudstones_ . : ‘ ; ; F : Pectinatites (Virgatosphinctoides) donovam, Inoceramus expansus, Parallelodon sp. Shales. : 5 : : : : : oul Pectinatites (Arkellites) hudlestont, P. (Vuirgato- sphinctoides) reisifornus, P. (V.) veisiformis densicos- tatus, P. (V.) cf. reistformis, P. (V.) abbreviatus, P. (V.) grandis acceleratus, Ostrea bonontae, Ostrea multiformis, Ostrea sp., Protocardia sp., Discina latissima. Cementstone ; : : é , : , Shales. . : ; : : 3 . ee Pectinatites (Virgatosphinctoides) reisiformis, Ostrea bononiae, Ostrea sp. Rope Lake Head Stone Band . : : : ee 55 Pectinatites (Virgatosphinctoides) wheatleyensis Zone Shales. : ‘ : ; : ‘ : - Aes Pectinatites (Virgatosphinctoides) reisiformis, P. (V.) wheatleyensis delicatulus, P. spp. indet., Ostrea sp. The Blackstone, or Kimmeridge Oil Shale . : ; 2 Pectinatites (Virgatosphinctoides) wheatleyensis delica- tulus, P. spp. indet, Saccocoma sp., Ostrea sp., Discina latissima, Lepidotus sp. Shales’. ‘ 3 , : ; ‘ : ere Pectinatites (Virgatosphinctoides) wheatleyensis, P. (V.) wheatleyensis delicatulus, P. (V.) grandis, P. (V.) pseudoscruposus, P. (V.) cf. pseudoscruposus, P. (V.) laticostatus, P. (V.) woodwardi, Saccocoma sp., Ostrea bononiae, Protocardia morinica, Lucina miniscula, Discina latissima, Lingula ovalis, Cerithium sp. Siltstone . : 2 ; ; : : : Shales) 2 ‘ ‘ : : ‘ , : <7 Ae Pectinatites (Virgatosphinctordes) laticostatus, P. (V.) woodwardt, P. (V.) wheatleyensis, P. (V.) grandis. in. IO Io Blake’s Bed Number 27 pars 27 pars 28-30 31 32533 32 33 34 35 36 o/s 4I pars UPPER KIMMERIDGE CLAY OF DORSET Siltstone . : A : ‘ , , ; Pectinatites (Virgatosphinctoides) laticostatus, Discina latissima. Shales 5 2 : 5 : . 5 : Pectinatites (Virgatosphinctoides) grandis, P. (V.) wheatleyensis minor, Ostrea sp. “ Dicey ’’ mudstones and shales . : : F Pectinatites (Virgatosphinctoides) laticostatus, P. (V.) smedmorensis, P. (V.) clavelli, Ostrea bononiae, Proto- cardia morinica, Lingula ovalis. Grey Ledge Stone Band (Top Ledge of Spath) Pectinatites (Virgatosphinctoides) scitulus Zone Upper Cattle Ledge Shales “ Dicey ’’ mudstones Ostrea sp. Shales Opialaseuns o Cattle Ledge Stone Band Pectinatites (Virgatosphinctoides) cf. ER Lower Cattle Ledge Shales 5 : Pectinatites (Virgatosphinctotdes) SHUTS, 2p (A) ck scitulus, P. (V.) decorosus, P. (V.) major, P. (V.) cf. major, P. (Arkellites) cuddlensis, P. (A.) damont, Gravesia cf. gravesiana, Ostrea bononiae, O. multiformis, Protocardia morinica, Lucina miniscula, Modiola autis- stodorensis, Exogyra virgula, Lingula ovalis, Discina latissima, Cerithium sp., Pliosaurus sp., Thrissops sp. Yellow Ledge Stone Band . 4 : : : Pectinatites (Arkellites) cuddlensts, P. (Virgatosphinc- toides) elegans corniger, P. (V.) cf. scitulus. Pectinatites (Virgatosphinctoides) elegans Zone Hen Cliff Shales ; : Pectinatites (Virgatosphinctoides) elegans, P. (V.) elegans cormger, P. (V.) major, P. (V.) cf. major, P. (Arkellites) cuddlensis, P. (A.) primitivus, P. sp. indet., Gravesia gigas, G. cf. gravesiana, Ostrea bonomae, Ostrea multi- formis, Ostrea sp., Exogyra virgula, Trigomia pellati, Pyrotocardia morinica, Lucina miniscula, Modiola autissiodorensis, Lingula ovalis. ft. 45 51 69 in. IO 10 UPPER KIMMERIDGE CLAY OF DORSET Blake’s Bed Number if: in. AI pars Cementstone . ; : : 5 , , 2 "2 0) 41 pars Shale : : ‘ : : : : : Sy Sh 1g) Pectinatites (Arkellites) cf. primitivus. 42 Cementstone . ‘ é 4 8 Pectinatites (Arkellites) cf. primitivus. TOTAL THICKNESS. ; , ‘ : : . 464 6 Ill. THE NON-AMMONITE FAUNA The non-ammonite fauna, although often abundant in terms of individuals, is represented by few species. VERTEBRATA Pisces. Fish remains are common throughout the succession, but consist mainly of isolated scales. Fish scales are exceedingly abundant in the Pectinatus Zone. Identifiable fish remains include Thrissops sp., and Lepidotus sp. ReptTiLiA. Vertebrae and occasionally other bones occur quite commonly. The anterior part of a skeleton of Ophthalmosaurus was found 12 ft. above the Cattle Ledge Stone Band, and a skull of [chthyosaurus from 12 ft. below the White Stone Band. A posterior tooth of a Pliosaur was found 5 ft. above the Yellow Ledge Stone Band. BRACHIOPODA Discina latissima (Sow.) occurs throughout, but is more common above the Black- stone Band. Lingula ovalis Sow. also ranges through the succession, but appears to reach its maximum just above the Yellow Ledge Stone Band. ECHINODERMATA One species of crinoid (Saccocoma sp.) occurs as isolated pyritized plates. It appears to be confined to the Blackstone and the ten feet of shale immediately below. MOLLUSCA GASTROPODA: Species of Cerithiwm have been found 27 ft. above the Yellow Ledge Stone Band, and 3 ft. below the Blackstone; apart from these occurrences no other gastropods were recorded. BrvaLviA: Bivalves are the most abundant of the non-ammonite fauna. Exogyra virgula (Defrance) occurs up to 27 ft. above the Yellow Ledge Stone Band. Protocardia morinica (de Loriol) and Lucina miniscula Blake are abundant through- out. UPPER KIMMERIDGE CLAY OF DORSET II Ostrea bononiae Sauvage and O. multiformis Koch & Dunker, commonly occur attached to the undersurfaces of ammonite shells. Other bivalves include Trigonia pellatt Mun-Chal., Parallelodon sp., Inoceramus expansus Blake, Ostrea solitaria Sow., and Modiola autissiodorensis (Cott.) Nautiloids and belemnites are absent from the fauna. IV. THE AMMONITE FAUNA (a) INTRODUCTION The state of preservation of the ammonites from the Kimmeridge section leaves much to be desired from the point of view of palaeontological investigations. The nodule bed in the Rotundum Zone of the Kimmeridge Clay is well known as one horizon which yields reasonably well preserved uncrushed ammonites. The author has found uncrushed, or relatively uncrushed, specimens at two other hori- zons, both of them in the part of the section described herein. One large isolated nodule 25 ft. below the Yellow Ledge Stone Band yielded a few pyritized ammonite nuclei, none of which are determinable specifically. The other horizon, the roof bed of the Blackstone, yields ammonites preserved in solid pyrite, but in which, un- fortunately, the septa have been completely pyritized and have become destroyed. All the other ammonites from other horizons have suffered crushing to a high degree. The ribbing, however, is generally well preserved, and is the basis for identification. The suture has almost invariably been completely obliterated. Considerable problems have had to be surmounted both in the collection and the preparation of these ammonites. Fossils cannot be collected from the cliffs, owing to the fissile nature of most of the rock, and the consequent weathering of the shale along the bedding. The abundant pyrite has oxidized, and the resulting selenite crystals cover the surface of the bedding planes. The shale reefs exposed at the base of the beach at low tide are the only places where ammonites can be satisfactorily collected. At some horizons, because of the very closely-spaced joints in the mudstone bands, it is impossible to extract the ammonites. In this case a plaster cast of the ammonite impression is made in the field. The detail reproduceable with thinly-mixed plaster is excellent, and the casts so obtained are, for most purposes, as satisfactory to work with as the actual ammonites from other horizons. The ammonites as they are extracted from the rock form most unpromising-looking material from the palaeontological point of view, and careful preparation is necessary before sufficient detail is visible for any determinative work. The rib interspaces are filled with hard shale, and often the whole ammonite is encrusted with irregular pyrite aggregates. The lower surface of the ammonite (lower surface of the ammonite as it lies in the rock) is very often more or less encrusted with oysters which are impossible to remove successfully. The crushing of the ammonites has affected most of the original measurements. The diameter has been increased by the flattening of the outer whorls; the whorl height is similarly affected, whilst the whorl thickness is reduced to about one-eighth of the original dimension. The diameter of the umbilicus is, however, relatively 12 UPPER KIMMERIDGE CLAY OF DORSET unchanged. The crushing of the outer whorl has the effect of making the point of bifurcation of the ribs appear much lower on the whorl side than it is in reality. For purposes of identification and speciation, therefore, the conventional four measurements are not given (i.e. diameter, then the other three measurements ex- pressed as a percentage of the diameter). Instead the diameter and the umbilical diameter only are given. These are both given as measurements since, as mentioned above, the diameter has been increased by the crushing. Also given, where possible, are the number of primary and secondary ribs on the outer whorl, and the number of ribs at various diameters (usually at 5 mm. intervals) within the umbilicus. In most cases the macroconch of a species is designated as the holotype. Where this is not possible (i.e. when the macroconch of a species has not been found, or when no well-preserved macroconch has been obtained), the microconch is designated as the holotype. In cases where the collection of specimens can only be carried out by the making of plaster casts in the field, the macroconch casts have, not infrequently, very much obscured inner whorls. The reason for this is that the casts are made of the under- surface of the ammonites as they lie in the rock, and these under-surfaces are often encrusted with oysters. (b) SYSTEMATIC DESCRIPTIONS Phylum MoLiusca Class CEPHALOPODA Sub-class AMMONOIDEA Order AMMONITIDA Superfamily PERISPHINCTACEAE Family PERISPHINCTIDAE Sub-family AULACOSTEPHANINAE Spath 1924 Genus GRAVESIA Salfeld 1913 Type species by subsequent designation (Roman 1938): Ammonites gravesianus d’Orbigny 1850. Gravesia gigas (Zieten) (Bis re te: a) 1830 Ammonites gigas Zieten, pl. 13, fig. I. 1963 Gvravesia gigas (Zieten) ; Hahn: 97, pl. 9, pl. 10, figs. 1, 2 (see also for earlier references). MATERIAL. Two specimens. STRATIGRAPHICAL RANGE. 40-45 ft. below the Yellow Ledge Stone Band. DESCRIPTION. These two specimens, which are similar to one another, are crushed flat. Diameter 308-322 mm. Diameter of umbilicus 104-114 mm. The UPPER KIMMERIDGE CLAY OF DORSET RIB DIRECTION — ~— ae RURSIRADIATE RECTIRADIATE PRORSIRADIATE RIB WIRE SECONDARY INTERCALATORY == BIFURCATE SIMPLE POLY GYRATE POLY PLOKE VIRGATOTOME Fic. 2. Rib directions and rib types occurring in the ammonites of the Upper Kimmeridge Clay. 14 UPPER KIMMERIDGE CLAY OF DORSET original diameter was probably around 240 mm. There is a very close resemblance to the neotype (Hahn 1963, pl. 9, fig. 1), the only discernible difference being that the Dorset specimens still have quite prominent secondary ribs on the venter at the aperture. REMARKS. This species is extremely rare in Dorset, two other specimens exist in the collections of Spath in the British Museum and are also from the same horizon. Salfeld recorded “‘ numerous examples” of G. gravesiana from about this horizon (Arkell 1933 : 440). This species appears, however, to occur higher in the succession. Gravesia cf. gravesiana (d’Orbigny) (Bi tie. 2) 1850 Ammonites gravesianus d’Orbigny : 559, pl. 219, figs. 1, 2. 1963 Gyvavesia gravesiana (d’Orbigny) ; Hahn: 99, pl. 10, figs. 3, 4; pl. 12, figs. 3, 4; pl. 13, fig. 2. (See also for earlier references.) MATERIAL. Two specimens. STRATIGRAPHICAL RANGE. From 8 ft. below to 6 ft. above the Yellow Ledge Stone Band. DeEscrIPTION. Both the specimens are whorl fragments. The larger (PI. 1, fig. 2) shows the ribbing very well and is very close to G. gravesiana. The total estimated crushed diameter of this specimen would be about 160 mm. The other specimen shows only three primary ribs, with internal moulds of the secondary ribs, but is similar in rib style to the first specimen. REMARKS. Salfeld recorded Gravesia irius at about this horizon, a species which the author was not able to find. The occurrence of Gravesia above the Yellow Ledge Stone Band has not hitherto been reported, but as this genus is so rare in Dorset it is by no means certain that the newly established range of 60 feet in Dorset is the maximum range of this genus. Subfamily VIRGATOSPHINCTINAE Spath 1923 Genus PECTINATITES Buckman 1922 Type species Ammonites pectinatus Phillips 1871. DiacGnosis. Dimorphic. Microconchs generally 65-IrI0 mm. in diameter, occasionally larger. Inner whorls with sharp biplicate ribbing, becoming a little coarser on body-chamber with occasional simple and trifurcate ribs. Peristome with ventral horn. Body-chamber generally half a whorl long. Macroconchs generally 140-200 mm. occasionally larger, very rarely smaller. Inner whorls with sharp biplicate ribbing. Outer whorl very variable, usually with strong primary ribs and two to five secondary ribs to each primary rib. Peristome simple. Body- chamber generally half a whorl long. Constrictions present in some species. Upper Kimmeridgian. (Elegans to Pectinatus Zones). UPPER KIMMERIDGE CLAY OF DORSET 15 Sexual Dimorphism Detailed collecting from the Upper Kimmeridge Clay at the type-section at Kimmeridge, Dorset, has revealed many ammonites referable to species of the genus Pectinatites Buckman. Random sampling has established that the vast majority of these fall into one of two size groups. Formerly it has been considered by those who had collected ammonites from this section (e.g. Arkell & Spath), that the smaller specimens were merely young forms of the larger. However, these previous collections consist mostly of individuals from which the peristome had been broken during extraction from the rock, and examination of recent collections, consisting mainly of individuals with peristome intact, suggests a new interpretation of the size grouping. This interpretation arises from the fact that at every horizon from which collections were made, only two size groups are found. The smaller size falls into the 65-110 mm. diameter range, and the larger into the 140-200 mm. diameter range. If the ammonites of the smaller size group were the young of the larger ones it would be remarkable not to find, at some horizon, ammonites falling into the size range 110-140 mm. diameter. Evidence to show that the two groups are quite distinct follows below. Callomon (1963 : 25) has summarized the criteria by which an ammonite may be judged to be mature. These are: (a) Uncoiling of the umbilical seam. (b) Modification of sculpture near the peristome; usually a coarsening and re- or degeneration of ribbing, but often with terminal constric- tions, ventral collars, flares, horns, rostra, lateral lappets etc. (c) Approximation and degeneration of the last few septal sutures. As the ammonites are badly crushed, all traces of the septa have been destroyed. If, however, the first two of these criteria are applied, it is found that both size groups mentioned above consist of mature individuals. Species of these perisphinctid ammonites are best distinguished from one another by the density of the ribbing. If the numbers of ribs at given diameters are plotted against diameters on a graph, a curve is produced which is distinctive for any given species. The two size groups under consideration here give generally similar, but not identical curves, so that it is possible to distinguish, by means of rib curves, the larger from the smaller type, even with incomplete material. These two groups have been referred to as microconchs and macroconchs by Callomon (1957 : 62), a terminology which has become generally accepted. The microconchs, in this case, are generally small forms with a diameter of 65-110 mm., but at one horizon they range up to 185 mm. in size. In all cases the ribbing is of normal perisphinctid biplicate style and, apart from slight coarsening towards the aperture and occasional development of polygyrate ribs, shows little modification. The aperture bears a horn-like process projecting from the venter. The umbilical seam gradually uncoils over the last half whorl, so that at the aperture many forms are completely evolute. The apertural margin is sometimes devoid of ribbing and shows a smooth zone, ornamented little, save for growth lines, and the presence of the ventral horn. 16 UPPER KIMMERIDGE CLAY OF DORSET The macroconchs are usually 140-200 mm. in diameter, but occasionally are larger, or very rarely smaller, and are characterized by a smooth sinuous peristome margin. The ribbing on the inner whorls is of a simple biplicate style, but the point of bifurca- tion usually occurs slightly higher on the whorl side than it does on the microconchs. The body-chamber develops irregular ribbing and, particularly in the forms from higher horizons, has a tendency to fasciculation or virgatotomy. Uncoiling of the umbilical seam occurs only over the last half whorl. The two forms are found in association throughout the succession, although the ratio of microconchs to macroconchs varies. This ratio is usually within the limits 2:1-1:2. Where only a few specimens have been obtained from one horizon this ratio is not treated as significant. That these two groups of ammonites are very closely related is strongly suggested by their co-existence at each fossiliferous horizon, their identical stratigraphical range, and their similar rib curves. However, four specimens from one horizon (13 feet above the Rope Lake Head Stone Band) from which have been collected 32 microconchs and 34 macroconchs, show conclusively the relationship. Three of these specimens appear to be normal macroconchs, but have on their inner whorls structures resembling those of the horn of the microconch. However, this structure differs from the true microconch horn; it has negligible ventral projection, it is developed from a single rib, and it projects laterally. The fourth of these specimens is unique in that it is intermediate in size between the two groups (117 mm. diameter), has the typical microconch horn developed, but shows the beginnings of the macroconch type of ribbing associated with four further horns. The rib density of the first three of the ammonites shows them to have affinity with the macroconch group. The fourth specimen has a rib density intermediate between that of a microconch and a macroconch. The undersides of the ammonites, as they lie in the rock, are quite often encrusted with oysters, although the upper surface is generally free of them. It would, there- fore, seem that the oysters attached themselves to the ammonite conch after the death of the latter, otherwise the oysters would presumably be equally common on both surfaces. They apparently grew in the shelter provided by the umbilical space beneath the ammonite, and flourished there until continued sedimentation eventually killed them. Medcof (1955) has shown that modern oyster larvae prefer to settle on under-surfaces. In this case the ammonite shells would provide the only such surfaces available on the sea bed. Judging by the size of these oysters, a considerable time must have elapsed before they were killed by the continued influx of sediment, so that we may reasonably conclude that sedimentation was not rapid. This is also supported by lithological evidence. The rocks are a fairly uniform argillaceous series—grey and black shales and clays with occasional cementstone bands—and, apart from lamination, are devoid of sedimentary structures. Save for the very occasional juvenile forms and occasional gerontic forms, all the ammonites fall into one of the two size groups mentioned previously, and bearing in mind the evidence of slow deposition, it is likely that the ammonite faunas of the Upper Kimmeridge Clay in Dorset represent a death assemblage. UPPER KIMMERIDGE CLAY OF DORSET 17 Taking into account the evidence of maturity of the ammonites, and the fact that they represent death assemblages, it would appear evident that the difference in size of the two groups is of a fundamental nature. It seems most unlikely that current sorting of the shells, or sudden extermination of whole populations occurred. The most obvious interpretation of this size distribution is that these ammonites exhibit dimorphism. Dimorphism of ammonite shells is probably an expression of some difference which was present in the soft parts also. The most obvious differ- ence between dimorphs would appear to be a sexual one, and there is some evidence to suggest that the microconch and macroconch may represent the two sexes. Examination of the microconchs yields several important facts relating to the horn. It is never developed until a diameter of at least 60 mm. (generally more) is attained. In other words, the horn is not developed until a certain stage of growth is reached. At various growth stages beyond this diameter further horns may be developed, but the presence of a former horn or horns is always detectable. Sometimes the earlier horn is retained, and in other cases the earlier horns appear to have been shed, and to have left behind a characteristic scar on the venter. Apart from the four macroconch specimens mentioned earlier, none shows any trace on the earlier whorls of any type of horn or ventral scar. In section, the microconch horn is U-shaped, opening forwards. This suggests that it housed some part of the soft parts of the animal, and, since the horn is confined to the microconch, it is reasonable to assume that its function may have been sexual. This would explain its confinement to the microconch, and its occurrence only in nearly full-grown specimens. The four specimens showing characteristics of each group can then be explained as various degrees of intersexual specimens. Three of them are barely distinguishable from true macroconchs, but the fourth appears to be a true intersex. As mentioned above, the macroconchs and microconchs differ somewhat in the density of their ribbing. At 15 mm. diameter (the smallest diameter at which it is practicable to count the ribs accurately) the macroconchs are nearly always finer ribbed than the corresponding microconchs. The comparative density of the ribbing of the two forms, at greater diameters, is seen to vary with the species concerned. Presumably, both microconch and macroconch reached maturity at the same age, so that the rate of growth of the macroconch must have been greater than that of the microconch. This would appear to explain these discrepancies, since growth rate in each species must, to perhaps a small and varying extent, have had an effect on the density of the ribbing. Our knowledge of the soft parts of ammonites is almost entirely based on analogy with modern cephalopods, particularly Nautilus. In most living cephalopods the male of the species is smaller than the female. In Nawtilus, however, the male is slightly broader-shelled than the female, the extra breadth of the shell being utilised to incorporate the male copulatory organs, the diameter of the two shells is approxi- mately equal. It appears, therefore, that in any case of marked dimorphism in modern cephalopods the male is the smaller sex, and it therefore appears likely that in Pectinatites the microconch represents the male of the species. If this were so, the horn may have assisted in copulation. If the spadix (the copulatory organ of the GEOL. 15, I. 2 18 UPPER KIMMERIDGE CLAY OF DORSET male cephalopods) were housed within the horn, by insertion of the horn within the venter of the female shell, fertilization of the ova would be more readily assured. Dimorphism has been reported in other groups of ammonites by various authors (e.g. Callomon 1963, Makowski 1962, Westermann 1964). In many of the reported instances, the microconch aperture bears a pair of lappets developed laterally. Lappets are not present in any ammonites found hitherto from the Upper Kim- meridge Clay, while the horn of the Kimmeridgian microconchs is apparently unique to this group of ammonites. These horned Kimmeridgian forms are known outside Britain from Northern France and Greenland, and, as they appear to have evolved rapidly, promise much in precise correlations within this Upper Jurassic faunal province. Interpretation of PECTINATITES The genus Pectinatites was originally proposed for a few closely related species from the Pectinatus Zone of Oxfordshire. The Pectinatus Zone there is to be correlated with the rocks between the White Stone Band, and the base of the Pavlovia votunda Zone in the Dorset succession. As early as 1896 Hudleston (1896 : 322) had remarked on the similarity between Ammomites pectinatus and the pyritized ammonites which occur at the top of the Kimmeridge Oil Shale or Blackstone, about 150 ft. below the White Stone Band in the Kimmeridge section. Buckman, in June 1925, assigned one species of these pyritized ammonites from the Blackstone to a new genus, Pectiniformites which he placed six hemerae earlier than his Pectinatus hemera, but Neaverson (Dec. 1925) did not accept Buckman’s findings, and placed these Blackstone ammonites in the genus Pectinatites. Spath (r936 : 18) in turn placed them in his genus Subplanites proposed in 1925. Herein, I place these ammonites in the genus Pectinatites, in which I recognize three subgenera: Pectinatites (sensu stricto); Virgatosphinctoides; and Arkellites subgen. nov. Many generic attributions have been given to species of Pectinatites in the past. These generic names, for the most part, belong to quite distinct genera many of which do not occur in Britain, while others of them are either junior synonyms, or in some cases subgenera of Pectimatites. As much confusion, and many unreliable correlations have been made on the basis of misidentification of species of Pectinatites with other genera, there follows a discussion of these genera and their relationship, if any, to Pectinatites. VIRGATITES Pavlow 1892 TYPE SPECIES. Ammonites virgatus von Buch 1832. (Subsequently designated Douvillé 1970.) This genus was recorded from the horizon of the Kimmeridge oil-shale by Salfeld (1913), and 2 zone of V. miatschkovensis introduced by him for the beds between the Gravesia zones and his zone of Perisphinctes pallasianus (= modern Pectinatus Zone). The genus is characterized by virgatotome ribbing on the inner whorls, sometimes UPPER KIMMERIDGE CLAY OF DORSET 19 reverting to simple or bifurcate ribbing on the body-chamber. All the Dorset ammonites from this part of the Kimmeridge Clay have normal perisphinctid bifurcate ribs on their inner whorls, and it is only on the outer whorl that virgatotome ribbing may develop. There is now no doubt that Virgatites is much younger in age than these Kimmeridge forms, and appears to be restricted to the Volgian faunal province of eastern Europe. PSEUDOVIRGATITES Vetters 1905 TYPE SPECIES. Ammonites scruposus Oppel in Zittel 1868. Lamplugh, Kitchin & Pringle (1923 : 222) recorded the occurrence of the genus Pseudovirgatites from Dorset, and introduced a zone of Pseudovirgatites to include the horizon of the Blackstone in Dorset. This genus is often homeomorphic with the genus Pectinatites. The type species from the Lower Tithonian has similar rib-style on its outer whorl to that of some large species of Pectinatites (e.g. P. (Virgatosphinc- toides) pseudoscruposus (Spath)). Other species of Pseudovirgatites, such as some of those recently figured by Donze & Enay (1961) and Michailov (1964), are remark- ably homeomorphic with some species of Pectinatites (e.g. P. (P.) inconsuetus sp. nov. See p. 138, Pl. 30). The microconch of Pseudovirgatites does not, however, possess a ventral peristomal horn as does Pectinatites, and all records of Pseudovirgatites from Britain would appear to refer to homeomorphic forms of Pectinatites. LITHACOCERAS Hyatt 1900 TYPE SPECIES. Ammonites ulmensis Oppel 1863. The inner whorls of Lithacoceras generally bear fine bifurcate ribs which modify on the outer whorl of the macroconch to produce in the type-species widely-spaced blunt primary ribs, each giving rise to up to eight secondaries. Some species of the genus reach a very large size. There is often a considerable degree of homeomorphy between species of this genus and species of Pectinatites. Apart from peristomal differences, the microconchs of the two genera can be very similar, and the middle whorls of a macroconch of Lithacoceras sometimes very closely approach the ornament of the macroconch of Pectinatites. This homeomorphy has misled many workers in the past. In particular the species of Pectinatites from the Hen Cliff Shales have been identified in the past as Lithacoceras. (e.g. Arkell 1956 : 2r). PECTINATITES Buckman 1922 TYPE SPECIES. Ammonites pectinatus Phillips 1871. The name Pectinatites is the most senior available name for the British Upper Kimmeridgian ammonites described herein. It is distinguished from all other genera which are to varying degrees homeomorphic with it, by its type of dimorphism. As these ammonites with horned microconchs form a closely related natural group, it is here proposed to include all such dimorphic forms in this genus. 20 UPPER KIMMERIDGE CLAY OF DORSET WHEATLEYITES Buckman 1923 TypE SPECIES. Wheatleyites tricostulatus Buckman 1923. This genus is characterized by finely-ribbed inner whorls, which modify to produce an outer whorl with coarse widely-spaced primary ribs; the secondary ribs gradually fade on the body-chamber. Some forms of Wheatleyites are homeomorphic with species of the Tithonian genus Pseudovirgatites. Wheatleyites is here regarded as a junior synonym of Pectinatites, it being a name applied by Buckman to macroconchs of Pectinatites having this particular type of modification of the ribs on the outer whorls. SUBPLANITES Spath 1925 (January) TyPEs SPECIES. Virgatosphinctes reist Schneid 1914. To this genus belong a complex of forms occurring in the Tithonian rocks of Europe. Characteristically their inner whorls bear fine bifurcate ribs, which are modified on the body-chamber in a fashion similar to that which obtains in many species of Pectinatites. It was for this reason that many of the British species of Pectinatites were long considered to be species of Subplanites. Vuirgatosphinctoides Neaverson (here treated as a subgenus of Pectinatites), was considered a junior synonym of Subplanites. This undetected homeomorphy led to the establishment of a number of unreliable correlations between Britain and Southern Europe. The microconchs of Subplanites bear lappets, and are for this reason easily dis- tinguishable from the microconchs of Pectinatites when material with intact peristomes is available, but in the absence of specimens with peristomes it 1s virtually impossible to distinguish the two genera. All the British forms appear to belong to Pectinatites, but in the case of such faunas as those from Russia, recently described by Michailov (1964), it is not possible to determine the genus of ammonites present owing to the incomplete nature of the material. PECTINIFORMITES Buckman 1925 (June) TYPE SPECIES (by monotypy). Pectiniformites bivius Buckman 1925. The holotype which is in the Dorset County Museum, Dorchester, is a pyritic cast from the Blackstone. The pyrite of the outer whorl has in places reached an ad- vanced state of decomposition, and the specimen is now of little value. There is also in this museum, however, a cast of the holotype made in 1925, which appears to correspond very closely in dimensions to the holotype, and which is a better specimen than the holotype in its present condition. Buckman marked on his plate of the holotype (1925, pl. 568) the position of the last visible suture, which is just one whorl back from the supposed peristome. However, the type of preservation in the Blackstone (solid pyrite) generally destroys all trace of the septa, and in the author’s opinion, the septum marked by Buckman was the last viszble, but not the last occurring septum. This view is supported by the occurrence of better-preserved ammonites having affinities with this species UPPER KIMMERIDGE CLAY OF DORSET 21 and with a short body-chamber. (E.g. Pectinatites pectinatus (Phillips) Buckman 1922, pl. 354B, which shows five-eighths of a whorl of body-chamber; and the length of the body-chamber estimated from differences in the degree of crushing of the Dorset material, which suggests a body-chamber length of between three and five- eighths of a whorl. No specimen of Pectinatites is known to the author with a body- chamber as much as one whorl in length). The ammonites from the Blackstone are largely uncrushed, but there is another, more important, difference between the ammonites from this horizon and other horizons in the Dorset succession. In the Blackstone, ammonites of all growth stages are preserved, from very small nuclei to specimens over 150 mm. in diameter. This contrasts with other horizons where mature individuals make up by far the greater part of the ammonite fauna. Furthermore, no ammonites have been collected (or preserved?) in the Blackstone with intact peristomes. This means that it is not possible, in the case of the smaller specimens, to distinguish macroconchs from microconchs, and thus that the interpretation of Pectininformites is open to doubt. Further, the Blackstone has hitherto failed to yield macroconchs with well- preserved inner worls, so that the holotype of Pectiniformites bivius cannot be com- pared to any known macroconch specimen. It is, therefore, not possible to determine to which subgenus of Pectinatites this species belongs. The rib density is such that affinity with Arkellites subgen. nov. is unlikely (approximately 55 ribs at 30 mm. diameter). It may possibly therefore be consubgeneric with Virgatosphinctoides, but there appears to be no over-riding reason why it should not equally be placed in Pectinatites, sensu stricto. This was also the view of Neaverson (1925 : 15) ‘‘ Buckman has recently instituted a new genus Pectiniformutes for ammonites of the pectinatus- type from this facies (the oil shales of Kimmeridge). There seems to be no justifica- tion for this, and Pectinzformites must be regarded as synonymous with Pectinatites ’’. Pectiniformites would thus become a junior synonym of Pectinatites, and is so treated here. KERATINITES Buckman 1925 (October) TYPE SPECIES. Keratinites keratophorus Buckman 1925. This genus was introduced by Buckman for ammonites from the Pectinatus Zone having a peristome bearing a ventral horn. These forms are the microconchs of Pectinatites, and the name Keratinites is here regarded as a junior synonym of Pectinatites. VIRGATOSPHINCTOIDES Neaverson 1925 (December) : Ir TYPE SPECIES. Vuirgatosphinctoides wheatleyensis Neaverson 1925. This genus is characterized by finely ribbed inner whorls which are modified on the body-chamber of the macroconch, often producing polygyrate, polyploke, or virgatotome ribbing. The genus was regarded by Spath as synonymous with, or at the most subgenerically different from, his genus Subplanites proposed a few months earlier (see above). Systematic collections from Dorset have now established that 22 UPPER KIMMERIDGE CEAY OF DORSET Virgatosphinctoides is dimorphic. The microconchs bear a ventral horn and are never seen to have lappets. Virgatosphinctoides is thus easily distinguished from Subplanites when material with intact peristomes is available. The presence of a horned peristome, however, shows that Virgatosphinctoides is closely related to Pectinatites. The microconchs of the two are sometimes indistinguishable, and only the characters of the macroconchs can usefully separate the two forms. For this reason Virgatosphinctoides is here treated as a subgenus of Pectinatites. ALLOVIRGATITES Neaverson 1925 (December) : 29 TYPE SPECIES. Allovirgatites woodward: Neaverson 1925. Neaverson’s basis for distinction between Virgatosphinctoides and Allovirgatites appears to have been based almost entirely on differences in the septal suture of species of the two genera. However, the rib-style and its development is very similar in these two forms, and there appears to be little justification for drawing distinction between them. Neaverson admitted similarity between the suture lines of these two genera in the young stages, and there would seem little doubt that differences between his described forms are no more than specific differences. Allovirgatites is therefore here regarded as a junior synonym of Virgatosphinctoides. SUBDICHOTOMOCERAS Spath 1925 (January) TYPE SPECIES. Subdichotomoceras lamplught Spath 1925. This genus is characterized by sharply biplicate ribbing throughout development, together with deep constrictions which are bordered by simple ribs. The aperture is without lappets. The holotype came from the Eudoxus Zone of Yorkshire, and the genus does not appear to be represented in higher Kimmeridgian deposits in Dorset. SPHINCTOCERAS Neaverson 1925 (December) TYPE SPECIES. Sphinctoceras crassum Neaverson 1925. Two species of Sp/inctoceras were described by Neaverson from the Wheatleyensis Zone of Oxfordshire. They are massive inflated forms with coarse strong biplicate ribs. There seems little doubt that SAhinctoceras is closely related to Subdichoto- moceras, the former being almost certainly the macroconch of the latter. No specimens of Sphinctoceras have hitherto been found in Dorset, but the genus is mentioned here because the conservative “‘ biplex ’’ stock to which it belongs gave rise to the pavlovids in the Pectinatus Zone. The sharp biplicate ribbing, the very high point of bifurcation of the ribs, and the absence of polygyrate ribs and any marked apertural modification make identification of these forms with more coarsely- ribbed species of Pectinatites unlikely. The origins of PECTINATITES The origins of Pectinatites are rather obscure, but there is one feature of the ribbing which must be considered of great value in deducing the origin of the genus, This UPPER KIMMERIDGE CLAY OF DORSET 23 is the presence of the polygyrate, and more rarely the polyploke rib type (Geyer rg6r, text-fig. 1). This type of ribbing, which is first found in some Upper Oxfordian ammonites, is the first new character in perisphinctid ornamentation to appear since the Bajocian, and it therefore appears very probable that all ammonites which have this rib style are related. In the Lower Kimmeridgian genus Ataxioceras, the development of polygyrate ribbing reaches its extreme. Ataxioceras is also often ribbed in a most irregular fashion, a character which is evident in many species of Pectinatites. A further character of Ataxioceras is of importance too in tracing the origin of Pectinatites. This is the apertural modification of the microconch. Most microconchs of Ataxtio- cevas appear to have well-developed lappets (e.g. Geyer 19614, pl. 14, fig. 2), but there are specimens which appear to have a horn developed (e.g. Geyer 19614, pl. 13, fig. 5). It thus appears that three of the most important characters of Pectinatites are also found in Ataxioceras. There must also be taken into account the remarkable similarity of some species of Pectinatites to species of the Tithonian genera Subplanites, Lithacoceras, and Pseudovirgatites. There can be no doubt that there was a marine connection between Britain and the Swabia—Franconia area at least for a short while after the Lower Kimmeridgian, since the genus Gvavesia is common to both areas. However, there are apparently no substantiated records of Lithacoceras or Subplanites from the Lower Kimmeridgian of Britain. (In this respect I cannot accept Arkell’s report of Lithacoceras from the Aulacostephanus zones (1947 : 73); or that of Ziegler of Sub- planites rueppellianus from the same beds (1962 : 13)). All reported instances of these genera must, in the absence of any figured evidence to the contrary, be inter- preted as occurrences of hitherto undescribed perisphinctids which in the author’s opinion do not belong either to Subplanites or Lithacoceras. The difference between Subplanites and Lithacoceras on the one hand, and Pectina- tites sensu lato on the other hand has not been recognized hitherto owing to the failure to take note of the different types of dimorphism in the two faunal provinces. As shown above, the microconchs of Pectinatites are horned, the macroconchs have a straight peristome and often a tendency towards virgatotome ribbing on the body- chamber. Subplanites and Lithacoceras both have lappeted microconchs, si) that microconchs with intact peristomes are easily distinguishable from microconchs of Pectinatites. However, several species of microconchs of Subplanites such as S. reist, S. schlossert, and S. moernsheimensis have polygyrate ribbing on their body-chamber, and are similar in adult size and rib-style to macroconchs of species of Pectinatites, but differ in that the former bear lappets whereas the latter do not. When material without intact peristomes is compared, therefore, the two forms are virtually indistinguish- able. Similarly Lithacoceras can be confused with Pectinatites when peristomes are not intact. Thus, previous comparisons of the British Kimmeridgian fauna to the Tithonian fauna have been comparisons between Kimmeridgian macroconchs and Tithonian microconchs. The similarity of the two faunas therefore must be regarded as an example of penecontemporaneous homeomorphy. However the similarity of the rib-style of the two faunas, in particular the presence 24 UPPER KIMMERIDGE CLAY OF DORSET of polygyrate ribbing, strongly suggests that they were derived from the same stock. This presumably lay in some of the less specialized of the Lower Kimmeridgian ataxioceratids, or in such a genus as the Upper Oxfordian Discosphinctes which has some polygyrate ribs on the body-chamber. This being the case it would seem that Lithacoceras should be classified together with Subplanites and Pectinatites in the same sub-family. Arkell (1957) placed Lithacoceras in the sub-family Ataxioceratinae (Buckman 1921) whilst Subplanites and Pectinatites were assigned by him to the sub-family Virgatosphinctinae (Spath 1923). Since these three genera are presumed to be derivatives of the ataxioceratid stock, and not themselves ataxioceratids, they perhaps should be all placed together in the sub-family Virgatosphinctinae. Subgenus ARKELLITES nov. Type SPECIES. Pectinatites (Arkellites) hudlestoni sp. nov. Diacnosis. Dimorphic. Microconchs fairly coarsely ribbed on inner whorls. Body-chamber generally more coarsely ribbed than inner whorls. Horn sometimes little more than an inflation of ventral part of peristome. Macroconchs with similarly ribbed inner whorls to those of microconchs. Outer whorl showing little or no variocostation, ribs little changed to the peristome. Some species showing strengthening of primary ribs with development of intercalatory secondary and unbranched primary ribs. Polygyrate ribs generally rare. Peristome simple. Constrictions if present shallow. Suture line unknown. Upper Kimmeridgian, Elegans to Hudlestoni Zones, ? Lower Pectinatus Zone. Pectinatites (Arkellites) primitivus sp. nov. (PIs nes: i. 25k 3) DiaGnosis. Macroconchs 125-150 mm. in diameter, with following rib densities: ates mith) 3032 tbs; ait 20) 32-345 025, 33=3590S0, 33-30 7=301 3enS 7 AO mae Sen 45, 37-38; 50, 39; 55, 40; 60, 41; 65, 43. Ribs rectiradiate to prorsiradiate with wide angle of furcation. Outer whorl variable but typically with frequent un- branched primary ribs. Microconchs 80-105 mm. in diameter, with following rib densities: at 15 mm. 32 ribs; at 20, 32-36; 25, 33-37; 30, 34-38; 35, 35-38; 40, 36-40. Ribs rectiradiate or slightly prorsiradiate. Outer whorl variable with bifurcate ribs predominating, sometimes with polygyrate and simple ribs, and intercalatory secondaries. Peristome slightly inflated ventrally. HoLotyPe. Macroconch C.73392. PARATYPE. Macroconch C.73393. PARATYPES (ALLOTYPES). Microconchs C.73394, C.73395. MATERIAL. Nine specimens (four macroconchs, five microconchs). Horizon. Holotype, paratype and allotype C.73394, from 25 ft. below the Yellow Ledge Stone Band. Allotype C.73395 from 55 ft. below this band. NUMBER OF RIBS UPPER KIMMERIDGE CLAY OF DORSET 25 ; Se S 40 30 45 40 \\ | LEN ‘\ : tC 30 45 40 ieee Zz S 30 eee WS} 25 35 45 55 65 DIAMETER (MM.) Fic. 3. Rib density of species of the subgenus Arkellites. Upper case letters: macro- conchs ; lower case letters: microconchs. H, h: P. (A.) hudlestoni; D,d: P. (A.) damont; C,c: P. (A.) cuddlensis; P, p: P. (A.) primitivus. 26 UPPER KIMMERIDGE CLAY OF DORSET STRATIGRAPHICAL RANGE. Upper Kimmeridgian, Elegans Zone, between 12 and 55 ft. below the Yellow Ledge Stone Band (see below). DESCRIPTION. Macroconch. Evolute shell with a diameter of 125-150 mm. Diameter of umbilicus 49-65 mm. The last whorl of the holotype has 54 primary and 76 secondary ribs, while the last whorl of the paratype has approximately 48 primary and go secondary ribs. At 20 mm. diameter there are 34 ribs; at 25, 35; 30, 36; 35, 36; 40, 37; 45, 37-38; 50, 39; 55, 40; 60, 41; 65, 43. The paratype has a similar rib-density. The ribs on the inner whorls are rectiradiate at the umbilical shoulder, then sweep forward to become prorsiradiate. (The few apparently rursiradial ribs on the holotype have been distorted by crushing.) The point of bifurcation of the ribs is high on the whorl side. The umbilical seam gradually uncoils over the last half- whorl. The ribs on the outer whorl are either bifurcate or simple. The angle of bifurcation is larger than in most of the species of this subgenus. The holotype shows no fewer than 19 simple ribs on its outer whorl. The paratype has fewer simple ribs (approximately 9) and at least one trifurcate rib. Microconch. Evolute shell with a diameter of between 80 and 105 mm. Diameter of umbilicus 32-40 mm. The last whorl of paratype C.73395 has approximately 45 primary and 103 secondary ribs. At 15 mm. diameter there are 32 ribs, at 20, S235 25), SS=Sy/s Sh SHE9 Bop Sesids ZO), =A: The ribs on the inner whorl are rectiradiate at the umbilical shoulder but curve forwards and become straight and slightly prorsiradiate for the rest of their length. The point of bifurcation of the ribs is high on the whorl side. The umbilical seam uncoils over the last half whorl. The ribs on the outer whorl gradually become straight and rectiradiate. There are three simple ribs on the last whorl of paratype C.73394, otherwise the ribs are bifurcate. The other paratype shows several poly- gyrate ribs on the last whorl. The peristome is slightly inflated ventrally. Remarks. The macroconch of this species shows features which are interpreted as being primitive characters of the genus. These include the wide angle of furcation of the ribs, the abundant unbranched primary ribs, and the relative absence of trifurcate (polygyrate) ribs. The microconchs exhibit only a feeble ventral inflation of the peristome. The outer whorl of allotype C.73395 shows resemblance in its rib-style to microconchs of species of the sub-genus Virgatosphinctoides, but the coarser ribbing of the inner whorls of the former provides easy distinction. It is possible, however, that the subgenus Virgatosphinctotdes was derived from this species. Incomplete and poorly preserved ammonites from the lowest Hen Cliff Shales, and their basal cementstone, may belong to this species. This would extend the range of the species down to 70 feet below the Yellow Ledge Stone Band. Pectinatites (Arkellites) cuddlensis sp. nov. (Bie Piss etiget) Dracnosis. Large stoutly-ribbed Arkellites. Macroconchs 160-210 mm. in diameter, with following rib densities: at 30 mm., 34—40 ribs; at 35, 37-40; 40, 38-41; UPPER KIMMERIDGE CLAY OF DORSET 27 45, 39-41; 50, 40-42; 55, 40-42; 60, 41-43; 65, 42-43. Ribs rectiradiate to slightly prorsiradiate. Outer whorl with mainly bifurcate ribs, but some unbranched primary and occasional polygyrate ribs, and intercalatory secondary ribs. Microconchs 110-128 mm. in diameter, with following rib densities: at 15 mm., 33-34 ribs; at 20, 34-36; 25, 35-37; 30, 35-38; 35, 36-39; 40, 36-41; 45, 37. Ribs of inner whorls similar in style to macroconch. Peristome with ventral horn 6—21 mm. long. HototyPeE. Macroconch C.733096. PARATYPE (ALLOTYPE). Microconch C.73397. MATERIAL. Nine specimens (five macroconchs, four microconchs). Horizon. Holotype from 18 ft. and paratype from 25 ft. above the Yellow Ledge Stone Band. STRATIGRAPHICAL RANGE. Upper Kimmeridgian, topmost Elegans to lower Scitulus Zones, 12 ft. below to 27 ft. above the Yellow Ledge Stone Band. DescripTIon. Macroconch. Evolute shell with a diameter of 160-210 mm. The holotype has a diameter of 206 mm., and an umbilical diameter of 94 mm. There are 49 primary and 107 secondary ribs on the outer whorl of the holotype. At 30 mm. diameter the holotype has 34 ribs; at 35, 36; 40, 38; 45, 39; 50,40; 55,40; 60, 41; 65, 42; 70, 43; 75,44; 80, 46; 85,47; 90, 48. The variation in rib density within the species is shown in Text-fig. 3. The ribs on the inner whorls are rursiradiate at the umbilical shoulder; they then swing forwards and become rectiradiate or slightly prorsiradiate and fairly straight. Some of the ribs on the inner whorls of the holotype are partially distorted by the crushing. The point of bifurcation of the ribs is high on the whorl-side. There is a slight uncoiling of the umbilical seam over the last half whorl. The ribs on the outer whorl become stronger and their furcation somewhat irregular, with the development of intercalatory secondary ribs, unbranched primary ribs, occasional trifurcate ribs, and occasional furcation low in the whorl-side. There do not appear to be any constrictions on the last whorl, although the rib style at one point (a trifurcate rib followed very closely by a simple rib) is very similar to that which obtains when a constriction is present. The peristome is simple. Microconch. Evolute shell with a diameter of 110-128 mm. Diameter of um- bilicus 42-47 mm. The last whorl of the paratype has 43 primary and 89 secondary ribs. At 15 mm. diameter the paratype has 33 ribs; at 30, 34; 25, 36; 30, 38; 35, 39; 40, 41. The other microconchs of this species are similar to the paratype in rib density. (Text-fig. 3). The ribs on the inner whorls are similar in style to those of the macroconch. The umbilical seam uncoils over the last half whorl, which appears to correspond to the length of the body-chamber. The ribs on the outer whorl coarsen slightly and are more or less straight and rectiradiate. There are occasional simple and trifurcate ribs on the last whorl. The aperture bears a horn which is 21 mm. long on the paratype; the other complete microconchs have shorter horns, 28 UPPER KIMMERIDGE CLAY OF DORSET REMARKS. This species has a similar, though not identical, density of ribbing on the inner whorls to that of P. (A.) primitivus, described above (p. 24). It differs, however, in adult size of both macroconch and microconch, and the density and style of ribbing of the outer whorl. It is probably, nevertheless, a derivative of this former species. Pectinatites (Arkellites) damoni sp. nov. (BES iss. 2, oe P16) Dracnosis. Macroconchs 136-160 mm. in diameter with following rib densities: at 25mm. 39 ribs; at 30, 40; 35, 40-41; 40, 41-42; 45, 41-42; 50, 42-43; 55, 43-45. Ribs rectiradiate to slightly prorsiradiate. Outer whorl with irregular ribs with fairly wide angle of furcation, occasional unbranched primary ribs. No trifurcate ribs. Microconchs 70-90 mm. in diameter with following rib densities: at 15 mm. 34-35 ribs; at 20, 35-37; 25, 30-37; 30, 36-37; 35, 37-38. Ribs generally pror- siradiate. Outer whorl with occasional unbranched primary and polygyrate ribs. Peristome with ventral ribbed horn 3-15 mm. long. HototypPe. Macroconch C.73308. PARATYPE. Macroconch C.73399. PARATYPES (ALLOTYPES). Microconchs C.73400, C.73401. MATERIAL. Sixteen specimens (four macroconchs, twelve microconchs). Horizon. Holotype and allotypes from 25 ft., paratype from 27 ft. above the Yellow Ledge Stone Band. STRATIGRAPHICAL RANGE. Upper Kimmeridgian, lower Scitulus Zone, ranging between 15 and 32 ft. above the Yellow Ledge Stone Band. DEscRIPTION. Macroconch. Moderately evolute shell with a diameter of 130-160 mm. Diameter of umbilicus 54-60 mm. The holotype has approximately 41 primary ribs on the last whorl. No macroconch of this species with a complete last whorl has been found. At 25 mm. diameter the holotype has 39 ribs; at 30, 40; 35, 40; 40, 41; 45, 41; 50, 42; 55, 43; 60, 43. The variation in rib density within the species is shown in Text-fig. 3. On the inner whorls the ribs are rursiradiate at the umbilical shoulder, they then swing forwards to become rectiradiate or slightly prorsiradiate and more or less straight. The point of bifurcation of the ribs is high on the whorl-side, and is not always visible on the innermost whorls. There is a slight uncoiling of the umbilical seam over the last half to three-quarters of a whorl. The ribs on the outer whorl are rather “ untidy” in appearance. They become coarser and have quite a wide angle of furcation. Occasional simple ribs are developed, but there is an absence of trifurcate ribs. No constrictions are visible. Although no specimen has its peristome preserved intact, it is presumably simple. Microconch. Evolute shell having a diameter of 702-90 mm. Diameter of um- bilicus 25-35 mm. The last whorl of paratype C.73400 has 42 primary and 86 secondary ribs. The density of the ribs on the inner whorls can only be approxi- UPPER KIMMERIDGE CLAY OF DORSET 29 mately determined on this specimen. Paratype C.73401 has 35 ribs at both 25 and 30 mm. diameter. Other microconchs of the species show similar rib densities (Text-fig. 3). The ribs of the inner whorls are similar in style to those of the macroconch, but tend to be more prorsiradiate. On the outer whorl the forward inclination is not so pronounced, and the ribs approach the rectiradiate condition. The point of bifurca- tion of the ribs is quite high on the whorl-side, and is not always visible on the inner whorls. The umbilical seam uncoils gradually over the last half whorl. The length of the body-chamber (estimated by differences in the degree of crushing) is usually half a whorl long, but in some specimens it appears to be only about three-eighths of a whorl in length. The ribs on the outer whorl are slightly coarser than those of the inner whorls. There may be several simple and occasional trifurcate ribs on the last whorl. The ventral part of the peristome bears a horn which varies in length from 3-15 mm. and is always quite strongly ribbed. REMARKS. The macroconch of this species shows some similarity with that of P. (A.) primitivus, described above (p. 24). It differs in the density of ribbing of the inner whorls. The respective microconchs are not likely to be confused on account of size, rib style and density, and horn development. This species may, however, be derived from P. (A.) primitivus. Adult size of both macroconch and microconch, and the very irregular ribbing of the outer whorl distinguished P. (A.) damoni from P. (A.) cuddlensis. Pectinatites (Arkellites) hudlestoni sp. nov. (BZ tie a bh 7 Piss fie. 2) Diacnosis. Large Arkellites with stout blunt ribs. Macroconchs 170-196 mm. in diameter with following rib densities: at 15 mm. there are 29-31 ribs; at 20, 4525313234; 302 32-35, 35, 34-375 40, 36-39; 45, 36-40; 50, 38-43; 55, 40-44; 60, 42-45. Ribs rectiradiate to slightly rursiradiate. Ribs on outer whorl becoming blunt and massive, with abundant intercalatory secondary ribs and occasional unbranched primary ribs. Microconchs 72-112 mm. in diameter, with following rib densities: at 15 mm., 29-32 ribs; at 20, 30-34; 25, 31-36; 30, 31-39; 35, 33-42; 40, 35-44; 45, 38-46. Ribs approximately rectiradiate, branching fairly low on whorl-side. Ribs coarser on outer whorl with occasional simple and rare polygyrate ribs. Peristome with well-developed ventral horn 4-21 mm. long. Horn ornamented only by growth lines. HototyrPe. Macroconch C.73403. PARATYPE (ALLOTYPE). Microconch C.73404. MATERIAL. Twenty-four specimens, including eleven plaster casts. Five macro- conchs, nineteen microconchs. Horizon. Holotype and paratype from shales 13 ft. above the Rope Lake Head Stone Band. 30 UPPER KIMMERIDGE CLAY OF DORSET STRATIGRAPHICAL RANGE. Upper Kimmeridgian, Hudlestoni Zone, from 12 ft. above the Rope Lake Head Stone Band to g ft. below the White Stone Band. Description. Macroconch. The dimensions given below are from the holotype which is the only reasonably complete macroconch which is well-preserved. Stoutly ribbed evolute shell with a diameter of 196 mm. Diameter of the umbilicus 93mm. There are 42 primary and 96 secondary ribs on the last whorl. At 15 mm. diameter there are 31 ribs; at 20, 32: 25, 32; 30, 333-35, 34; 40, 36; 45,36; 50; 38; 55, 40; 60, 42; 65, 42; 70, 43; 75, 44; 80, 45; 85, 46; 90, 46. The variation in rib density is shown in Text-fig. 3. The ribs on the inner whorls have a slight rursiradial curve at the umbilical shoulder; for the rest of their length they are straight and rectiradiate, or slightly rursiradiate. The point of bifurcation is high on the whorl-side apart from occasional ribs which branch near the umbilical shoulder. The umbilical seam uncoils over the last five-eighths of a whorl. On the outer whorl the ribs gradually become blunt and massive. The primary ribs branch to give only two secondary ribs; no trifurcate ribs are developed. There are, however, abundant intercalatory secondary ribs, and one or two simple ribs. The peristome is not preserved completely, but in the absence of any contrary evidence, is assumed to be simple. Miucroconch. Evolute shell with a diameter of 72-112 mm. Diameter of the umbilicus 26-45 mm. The paratype has a diameter of 98 mm. and an umbilical diameter of 44 mm. It has 55 primary and r1o secondary ribs on its outer whorl. At 15 mm. diameter the paratype has 31 ribs, at 20, 33; 25, 35; 30, 36; 35, 39; 40, 40; 45,42. The variation in rib density is shown in Text-fig. 3. The ribs on the inner whorls are of similar style to those of the macroconch, but the point of bifurcation is somewhat lower on the whorl-side. The umbilical seam uncoils over the last half whorl. The ribs on the last whorl gradually become coarser; occasional simple ribs are developed, and very rarely a trifurcate rib. The peristome is straight and has a well developed ventral horn. On the paratype the horn projects 20 mm. from the venter, but it may be asshortas4mm. The horn itself is ornamented only by growth lines, the ribs on the whorl-side fading as they approach the venter in the vicinity of the horn. REMARKS. This species is younger in age than other species of this subgenus recorded hitherto. It is distinguished by its rib-style, particularly the tendency for the ribs of the macroconch to be slightly rursiradiate. The microconch horn also tends to be free of ornamentation. On some specimens (e.g. C.73402 figured in Pl. 2, fig. 3) the venter bears scars, suggesting that earlier formed horns may have been shed. Subgenus VIRGATOSPHINCTOIDES Neaverson 1925 : II 1925 Allovirgatites Neaverson : 29. TYPE SPECIES. Vuirgatosphinctoides wheatleyensis Neaverson 1925. URPBRER IGCIMMERTEDGE CMAY OF DORSET 31 Diacnosis. Dimorphic. Macroconchs generally finely ribbed on inner whorls. Outer whorl very variable; primary ribs strong and typically with frequent poly- gyrate furcation, and often a tendency to become fasciculate or virgatotome; second- ary ribs obsolescent in some large species. Variocostation slight to pronounced. Peristome simple. Microconchs similarly ribbed on inner whorls to macroconchs. Body-chamber usually more coarsely ribbed than inner whorls. Peristome typically with well-developed ventral horn, more rarely only with ventrally inflated peristome. Constrictions commonly present, particularly in macroconchs. Upper Kimmeridgian, Elegans to Hudlestoni Zones. Pectinatites (Virgatosphinctoides) elegans sp. nov. (RISS hiesera 10. Pi) Diacnosis. Macroconchs 154—184 mm. in diameter with following rib densities: at 15 mm. diameter there are approximately 37 ribs; at 20, 38; 25, 39; 30, 39-42; 35, 40-43; 40, 41-45; 45, 42-46; 50, 43-47; 55, 44-48; 60, 45-49; 65, 46-50. Ribs slightly prorsiradiate, fairly straight. Outer whorl developing strengthened primary ribs, mainly bifurcate, but with occasional simple and polygyrate ribs and intercalatory secondaries. Microconchs 100-112 mm. in diameter with following rib densities: at 20 mm. diameter there are 39-44 ribs; at 25, 40-45; 30, 41-45; 35, 42-46; 40, 44-47. Ribs of inner whorls similar to macroconch, outer whorl slightly more strongly ribbed with occasional simple and polygyrate ribs. Peristome with ventral inflation projecting 4-8 mm. Hototyrr. Macroconch C.73405. PARATYPE (ALLOTYPE). Microconch C.73406. MATERIAL. Fifteen specimens (six macroconchs, nine microconchs). Horizon. Holotype from 18 ft. and paratype from 20 ft. below the Yellow Ledge Stone Band. STRATIGRAPHICAL RANGE. Upper Kimmeridgian, Elegans Zone, between 50 and 16 ft. below the Yellow Ledge Stone Band. DESCRIPTION. Macroconch. Evolute shell with a diameter of 154-184 mm. Diameter of the umbilicus 65-76 mm. There are 61 primary and 137 secondary ribs on the last whorl of the holotype. At 40 mm. diameter the holotype has 45 ribs, at 45, 66; 50, 47; 55, 48; 60, 48; 65, 49; 70,50. The variation in rib density is shown in Text-fig. 4. The sharp dense ribs on the inner whorls are slightly prorsiradiate and straight for most of their length, but at the umbilical shoulder are rectiradiate or rursiradiate as with other species of this subgenus. The point of bifurcation of the ribs is very high on the whorl side. The umbilical seam uncoils over the last half-whorl. The ribs on the outer whorl are similar in style to those of the inner whorls but gradually become more blunt and more widely spaced. Occasional simple and polygyrate ribs are developed on the outer whorl, but bifurcate ribs predominate. The peristome is simple. 32 UPPER KIMMERIDGE CLAY OF DORSET | ay 60 \ LTR [ \\ ‘OS ae NUMBER OF RIBS ta TAN Be Pe ae 40 Wh | TY WWE Aes |) a i Era 35 iS 25 35 45 58) 65 DIAMETER (MM.) Fic. 4. Rib density of species of the subgenus Virgatosphinctoides. Upper case letters : macroconchs ; lower case letters: microconchs. W,w: P. (V.) woodwardi; D,d: P. (V.) decorosus; S,s: P. (V.) scitulus; E, e: P. (V.) elegans. UPPER SIMMER EDGE ICLAY OF DORSET 33 Microconch. Evolute shell with a diameter of 100-112 mm. Diameter of the umbilicus (paratype) 40 mm. The paratype has 66 primary and approximately 130 secondary ribs on the last whorl. At 15 mm. diameter the paratype has approxi- mately 42 ribs; at 20, 44; 25, 45; 30,45; 35,46; 40,47. The variation in rib density is shown in Text-fig. 4. The rib style of the inner whorls is very similar to that of the macroconch. The umbilical seam uncoils over the last half whorl. No suture is visible, but differences in the degree of crushing suggest that the body-chamber is half a whorl in length. The ribs on the last half whorl become slightly coarser, and occasional simple and trifurcate ribs are developed. The peristome curves forward ventrally and is inflated on the ventral margin which projects 8 mm. on the paratype. The ribs pass uninterrupted over the projection. REMARKS. This is the earliest known species of the subgenus Virgatosphinctordes. The origin of the subgenus may have been from P. (Arkellites) primitivus described above (p. 24), the microconch of which shows a broadly similar rib style to this species, It is readily distinguished, however, by the much more finely ribbed inner whorls and the pronounced peristomal inflation. P.(V.) elegans is distinguished from later species of the subgenus by its rib-density, the peristomal development of the micro- conch and the body-chamber ornament of the macroconch. Pectinatites (Virgatosphinctoides) elegans corniger subsp. nov. (Pro) DiaGnosis. Macroconch approximately 125 mm. in diameter with following approximate rib densities: at 30 mm. 48 ribs; at 35, 49; 40, 50; 45, 5I; 50, 52. Ribs prorsiradiate, fairly straight. Outer whorl developing strengthened primary ribs with fairly frequent polygyrate ribs. Microconch 82-85 mm. in diameter with following rib densities: at 20 mm. diameter approximately 43 ribs; at 25, 45; 30, 46. Inner whorls similarly ribbed to macroconch, outer whorl slightly more coarsely ribbed with occasional simple and polygyrate ribs. Peristome with ventral horn up to 7 mm. long. HoLotypPe. Macroconch, C.73407. PARATYPES (ALLOTYPES). Microconchs. C.73408, C.73409. MaTERIAL. The holotype and two paratypes. Horizon. Holotype and paratype C.73408 from 5 ft., and paratype C.73409 from 8 ft. below the Yellow Ledge Stone Band. STRATIGRAPHICAL RANGE. Upper Kimmeridgian, topmost Elegans Zone, between 5 and 8 ft. below the Yellow Ledge Stone Band (see below). DescripTion. Macroconch. Evolute shell with an estimated diameter of 123 mm. Diameter of the umbilicus 50 mm. The last whorl has approximately 53 primary ribs. The number of secondary ribs cannot be determined since a part of the outer whorl has been broken away. At 39 mm. diameter there are 48 ribs; at 35, 49; 40, 50; 45, 51; 50, 52. GEOL, 15, I. 3 34 UPPER KIMMERIDGE CLAY OF DORSET The ribs on the inner whorls are of a similar style to those of P. (A.) elegans described above but tend to be a little more prorsiradiate. The point of bifurcation of the ribs is high on the whorl side. The umbilical seam uncoils over the last half whorl. The last umbilical whorl shows the development of occasional trifurcate and simple ribs; these become more numerous on the outer whork, where there is some degree of variocostation. Over the last half whorl the primary ribs become more widely spaced and more pronounced, and there are frequent polygyrate ribs. The peristome is not completely preserved, but is presumably simple. Microconch. Evolute shell with a diameter of 82-85 mm. Diameter of the umbilicus 28-32 mm. There are 55-63 primary and 122~130 secondary ribs on the last whorl. At 20 mm. diameter there are 43 ribs; at 25, 45; 30, 46. The rib style of the inner whorls is similar to that of the macroconch. The umbili- cal seam uncoils over the last half whorl, which appears to correspond to the length of the body-chamber, to judge by differences in the degree of crushing. The ribs on the outer whorl are of similar style to those of the inner whorls, but become slightly coarser with the tendency to develop occasional polygyrate and simple ribs. The peristome is curved forwards dorsally, and ventrally has a horn which is 7 mm. long on paratype C.73408. The secondary ribs pass uninterrupted over the horn. REMARKS. One fragment of an ammonite possibly belong to this subspecies was collected from the Yellow Ledge Stone Band, thus the stratigraphical range of the subspecies may extend upwards to the top of the Elegans Zone. The subspecies is intermediate in many respects between P. (V.) elegans (p. 31) and P. (V.) scitulus (p. 34). It is intermediate in age between the two, and shows charac- ters of both species. It is distinguished from the former species by the smaller adult size of both its macroconch and microconch, the peristomal development of the microconch, and the more strongly ribbed body chamber of the macroconch. Dis- tinction from the latter species is based on the adult size of the macroconch and microconch, the perstomal development of the microconch, and the ribbing on the body-chamber of the macroconch which is not so markedly variocostate as in P. (V.) scitulus. The rib-density of the subspecies shows a closer relationship to P. (V.) scitulus than to P. (V.) elegans; however, the subspecies is assigned to the latter species because the ornament of the body-chamber of the macroconch, and the ribbed horn of the microconch show more affinity to the developments of these characters in P.(V.) elegans. This subspecies appears to form a direct phylogenetic link between P. (V.) elegans and P. (V.) scitulus. Pectinatites (Virgatosphinctoides) scitulus sp. nov. (2iers) Dracnosis. Macroconchs 130-162 mm. in diameter with following rib densities: at 30 mm. diameter approximately 48 ribs; at 35, 46-49; 40, 46-49; 45, 47-49; 50, 48-49; 55, 49-50; 60, 49-50; 65, 49-51. Ribs rectiradiate to slightly prorsiradiate, straight. Outer whorl with strengthened primary ribs and variable number of UPPER KIMMERIDGE CLAY OF DORSET 35 simple and polygyrate ribs with occasional intercalatory secondary ribs. Micro- conchs 67-82 mm. in diameter with following rib densities: at 20 mm. diameter 42-44 ribs; at 25, 44-46; 30, 45-47; 35, 48. Inner whorls similar to macroconch. Outer whorl with slightly stronger ribs with tendency to be flexuous, and with occasional simple and polygyrate ribs. Peristome with feebly-ribbed ventral horn 7-16 mm. long. HototypPE. Macroconch C.7341I. PARATYPE (ALLOTYPES). Microconchs C.73412, C.73413. MATERIAL. Twenty-two specimens (ten macroconchs, twelve microconchs). Horizon. Holotype from 24 ft. above the Yellow Ledge Stone Band. Paratypes from 25 and 15 ft. respectively above this band. STRATIGRAPHICAL RANGE. Upper Kimmeridgian, lower half of Scitulus Zone, occurring in the Yellow Ledge Stone Band and up to 44 ft. above this horizon. DEscrIPTION. Macroconch. Evolute shell with a diameter of 130-162 mm. The holotype is 162 mm. diameter. Diameter of the umbilicus 50~78 mm. There are 47 primary and 99 secondary ribs on the last whorl of the holotype, other specimens have similar rib density on the last whorl. At 30 mm. diameter the holotype has 48 ribs; at 35, 49; 40, 49; 45, 49; 50, 49; 55,50; 60, 50; 65, 51; 70, 52; 75, 52. The variation in the rib density is shown in Text-fig. 4. The ribs on the inner whorls are dense and sharp. At the umbilical shoulder there is a slight rursiradial curve; the ribs then swing forwards and become straight and rectiradiate or slightly prorsiradiate. The point of bifurcation of the ribs is high on the whorl-side. The umbilical seam uncoils over the last half whorl. The outer whorl develops coarser ribs; the primary ribs become more widely spaced, and there is the development of simple and polygyrate ribs, and intercalatory secondary ribs. There appear to be several constrictions of the shell over the last whorl, but the crushing does not allow this to be definitely ascertained. There is considerable variability in the sculpture of the outer whorl, some specimens having very frequent polygyrate ribs. The peristome is simple. The length of the body- chamber is unknown. Microconch. Evolute shell with a diameter of 67-82 mm. Diameter of the umbilicus 25-32 mm. Paratype C.73413 has 45 primary and g2 secondary ribs on the last whorl; other specimens have similar rib density on the last whorl. At 20 mm. diameter there are 42 ribs; at 25, 44; 30,45. Variation in rib density ofthe inner whorls is shown in Text-fig. 4. The ribs on the inner whorls are identical in style to those of the macroconch. The umbilical seam uncoils over the last half whorl. Differential crushing suggest that the body-chamber varies in length from half to five-eighths of a whorl. The outer whorl has somewhat coarser ribs which tend to be a little flexuous. At the umbilical shoulder they are rursiradiate, then swing forwards to become slightly prorsiradiate, rectiradiate, or slightly rursiradiate. There are occasional simple and polygyrate ribs on the last whorl, which may have a few constrictions. 30 UPPER KIMMERIDGE CLAY OF DORSET The peristome has a ventral horn which varies in length from 7 to 16 mm. The horn is only feebly ribbed. REMARKS. ‘The points of distinction between this species and P. (V.) elegans and P. (V.) elegans corniger have been discussed above (p. 34). It is readily distinguished from P. (V.) decorosus described below (p. 36) by the rib density of the inner whorls. Pectinatites (Virgatosphinctoides) decorosus sp. nov. (Pi 2) Diacnosis. Macroconchs 120-140 mm. in diameter with following rib densities: at 30 mm. diameter there are 41 ribs; at 35, 41; 40, 41-42; 45, 41-42; 50, 41-42. Ribs of inner whorls fairly straight and prorsiradiate; outer whorl developing coarser more widely spaced rectiradiate ribs, with occasional constrictions followed by simple unbranched primary rib. Microconchs approximately 85 mm. in diameter with following approximate rib densities: at 25 mm. diameter there are 38 ribs; at 30, 39; 35, 42. Inner whorls ribbed similarly to macroconch, outer whorl with stronger rectiradiate ribs, occasionally simple or polygyrate. Peristome with ventral horn up to 9 mm. long. Hototyre. Macroconch C.73414. PARATYPE (ALLOTYPE). C.73415. MATERIAL. Eight specimens (four macroconchs, four microconchs). Horizon. Holotype and paratype from 15 ft. above the Yellow Ledge Stone Band. STRATIGRAPHICAL RANGE. Upper Kimmeridgian, Scitulus Zone, 15 to 30 ft. above the Yellow Ledge Stone Band. DescripTION. Macroconch. Evolute shell with a diameter of 120-140 mm. Diameter of the umbilicus 54-66 mm. The last whorl of the holotype has 43 primary and approximately 96 secondary ribs. At 30 mm. diameter there are 41 ribs; at 35, 41; 40, 41-42; 45, 41-42; 50, 41-42. The ribs on the innermost whorls are very slender and delicate; they are fairly straight and slightly prorsiradiate. An initial rursiradial curve then develops at the umbilical shoulder; the ribs then swing forwards to become prorsiradiate. The point of bifurcation of the ribs is quite high on the whorl side. The umbilical seam uncoils over the last half whorl. The ribs on the outer whorl gradually become coarser and more widely spaced, and lose most of their initial rursiradial curve to become fairly straight throughout their length. They are mainly rectiradiate, but vary from slightly rursiradiate to slightly prorsiradiate. There appear to be four or five constrictions on the outer whorl of the holotype. These are usually preceded by a polyploke rib, formed by the fusion close to the umbilical shoulder of two bifurcate ribs, and are always followed by a simple rib. Apart from these modifications, and the occasional intercalatory rib, all the ribs are bifurcate. The peristome is simple. UPPER KIMMERIDGE CLAY OF DORSET 37 Microconch. Evolute shell with a diameter of approximately 85 mm. All the measurements given are from the paratype which is the only well-preserved micro- conch. Diameter of the umbilicus 35 mm. The last whorl has 46 primary and approximately 90 secondary ribs. At 25 mm. diameter there are 38 ribs; at 30, 39; 35, 42. The rib style on the inner whorls is similar to that of the macroconch. The um- bilical seam uncoils over the last half whorl (which is estimated to be the length of the body-chamber). The ribs on the outer whorl are strong and rectiradiate; they are mainly bifurcate, but there are occasional simple and polygyrate ribs. The peristome has a ventral horn of moderate length (9 mm. on the paratype) and which is ribbed. It arises gradually as an extension of the venter, and does not project very sharply as is the case in several other species of the genus. REMARKS. The density and style of ribbing of this species render it readily distinguishable from allied species such as P. (V.) scitulus described above (p. 34). The rib density of the inner whorls shows some similarity to that of P. (A.) cuddlensis described above (p. 26), but adult size, rib style, and rib density of the outer whorl differ markedly in the two forms. Pectinatites (Virgatosphinctoides) major sp. nov. (Pin) Dracnosis. Very large Virgatosphinctoides with little varicocostation. Diameter approximately 240-320 mm., with following rib densities: at 50 mm. diameter there are 42-47 ribs; at 60, 44-48; 70, 46-50; 80, 48-51; 90, 49-53; I00, 50-55; ITO, 51-55; 120, 52-56; 130, 54-56; 140, 57. Ribs of inner whorls slender, rectiradiate to prorsiradiate; outer whorl with stronger rectiradiate ribs, with some simple and polygyrate ribs. HototyrPe. Macroconch C.73410. MATERIAL. Ten specimens (all macroconchs). Horizon. Holotype from 6 ft. below the Yellow Ledge Stone Band. STRATIGRAPHICAL RANGE. Upper Kimmeridgian, Upper part of Elegans Zone and Scitulus Zone, 20 ft. below the Yellow Ledge Stone Band up to the Cattle Ledge Stone Band. DEscriPTION. Macroconch. Evolute shell with a diameter of 240-320 mm. The diameter of the umbilicus varies from 130-150 mm. The holotype is 318 mm. in diameter, has an umbilical diameter of 140 mm., and 59 primary and 124 secondary ribs on the last whorl. At 5o mm. diameter it has 46 ribs; at 55,47; 60, 48; 65, 49; mOn5O 775,50; 80,515785, 52; 90; 53; 95, 54; 100, 55; 105,55; 110,55; 115, 55; 120, 56; 125, 65; 130, 56; 135, 57; 140, 57: The ribs on the inner whorls are slightly rursiradiate at the umbilical shoulder, and then bend forwards and become either rectiradiate or slightly prorsiradiate. The point of bifurcation of the ribs occurs fairly high on the whorl-side. The um- bilical seam uncoils over the last half whorl, The length of the body-chamber is NUMBER OF RIBS 38 UPPER KIMMERIDGE CLAY OF DORSET O DIAMETER (MM) Fic. 5. Rib density of species of the subgenus Vivgatosphinctoides. G: P. (V.) grandis ; P: P. (V.) pseudoscruposus; M: P. (V.) major; L: P. (V.) laticostatus. UPPER KIMMERIDGE CLAY OF DORSET 39 unknown, but would appear to be greater than two-thirds of a whorl, if the differential crushing is a reliable guide. The ribs on the outer whorl gradually lose their initial rursiradial curve, and become rectiradiate throughout. There is little variocostation in this species, and the ribs of the outer whorl remain predominantly bifurcate. There are, however, occasional simple and more rarely polygyrate ribs. The holo- type shows, in addition, one rib near the smooth peristome margin, which bifurcates very low on the whorl-side and again higher on the whorl, producing a total of four secondary ribs. This type of furcation (polyploke) is not seen on any other specimen of the species, otherwise the other specimens show little variation from the holotype, except that some of the specimens from higher horizons tend to develop a slightly lower point of furcation of the ribs on the body-chamber. The microconch of this species is unknown. REMARKS. The very large size of this species renders it readily distinguishable from other species of Pectinatites of the same age. It may be distinguished from other large species of the genus (all of which, described hitherto, are of younger age) by the very small degree of variocostation. Pectinatites (Virgatosphinctoides) clavelli sp. nov. (Pl. 14) Diacnosis. Macroconchs 2ro—260 mm. in diameter with following approximate rib densities: at 40 mm. diameter there are 46 ribs; at 50, 49; 60, 54-57; 70, 55-61; 80, 56-66. Ribs of inner whorls slender and rectiradiate. Outer whorl developing widely-spaced massive blunt primary ribs with frequent polygyrate furcation, and intercalatory secondary ribs. Microconchs 67-87 mm. diameter with following rib densities: at 25 mm. diameter there are 42 ribs; at 30, 43-44; 35, 44. Inner whorls similarly ribbed to macroconch. Outer whorls somewhat more coarsely- ribbed with occasional polygyrate and simple ribs. Peristome projecting ventrally by up to 5 mm. HototyrPe. Macroconch C.73432. PARATYPES (ALLOTYPES). Two microconchs, C.73433, C.73434. MATERIAL. Eleven specimens, all plaster casts (five macroconchs, six micro- conchs). Horizon. Holotype from 8 ft., and paratypes from 3 ft. above the Grey Ledge Stone Band. STRATIGRAPHICAL RANGE. Upper Kimmeridgian, lower Wheatleyensis Zone, between 3 and 28 ft. above the Grey Ledge Stone Band. Description. Macroconch. Large evolute shell with a diameter of approximately 210-260 mm. The diameter of the umbilicus varies from 104 to 130 mm. The last whorl of the holotype which is 212 mm. in diameter has 51 primary and an estimated 122 secondary ribs. The innermost whorls are not completely preserved inany onespecimen. At 60mm. diameter the holotype has 57 ribs, at 70, 62; 80, 66; 90, 69; 100, 71. The variation in rib density is shown in Text-fig. 6. NUMBER OF RIBS Ge ' : 40 UPPER KIMMERIDGE CLAY OF DORSET Tae i, ae 60 1 oe Eo | a et nade ee : K A 50 : nae Hise e pe Pile RIES AN ite a) 15 25 35 45 SS) 65 DIAMETER (MM) Fic. 6. Rib density of species of the subgenus Virgatosphinctoides. Upper case letters : macroconchs ; lower case letters: microconchs. W, w: P. (V.) wheatleyensis; C, c: P. (V.) clavelt; S,s: P. (V.) smedmorensis; m: P. (V.) magnimasculus ; E,e: P. (V.) encombensis ; A; P. (V.) abbreviatus, UPPER KIMMERIDGE CLAY OF DORSET 41 The ribs on the inner whorl are rursiradiate at the umbilical shoulder; they then swing forwards and become straight and more or less rectiradiate. The point of bifurcation of the ribs is high on the whorl-side. There is a marked uncoiling of the umbilical seam over the last half whorl. The ribs on the outer whorl become coarser, and the primary ribs become more widely spaced and irregular in their style and furcation. Some are rursiradiate, others rectiradiate or prorsiradiate. Several of the primary ribs show polygyrate furcation, and there is also a profusion of simple and intercalatory ribs on the last whorl. The peristome is simple. Microconch. Evolute shell considerably smaller than the macroconch, having a diameter of only 68-87 mm. The diameter of the umbilicus is 30-37 mm. There are 46 primary and 94 secondary ribs on the last whorl of paratype C .73434. The rib style of the inner whorls is similar to that of the macroconch. At 25 mm. diameter there are 42 ribs; at 30, 43-44; at 35,44. (Text-fig. 6). The point of bifurcation of the ribs is high on the whorl-side. The umbilical seam uncoils noticeably over the last half whorl. The outer whorls of both specimens are rather distorted by the crushing so that it is not easy to deterine the original rib direction. It would appear, however, to be rursiradiate at the umbilical shoulder, then becoming straight and rectiradiate. There are occasional simple ribs on the last whorl and a few primary ribs with three, or in one case, four secondary ribs. The ventral part of the perstome bears a short ribbed horn 4-5 mm. in length. It arises gradually from the venter and is not well preserved on either paratype. RemArRKS. The adult diameter of the macroconch and microconch, their rib density, and the development of the microconch horn, serve to distinguish this species from others. P. (V.) smedmorensis described below is considerably more coarsely ribbed than this species. As the highest beds of the underlying Scitulus Zone have hitherto yielded no ammonites, it is not possible to determine the origin of this species. The degree of variocostation of the macroconch is more pronounced than that of P. (V.) scztulus, but the general rib style of the two species shows some similarities. The very irregular costation of the body-chamber of the macroconch is a feature characteristic of many of the younger species of the subgenus Vzrgato- sphinctoides. The development of the microconch horn in this species is not, however, very typical. Pectinatites (Virgatosphinctoides) smedmorensis sp. nov. (Pl. 15, figs. 1, 2) Diacnosis. Macroconchs approximately 150 mm. in diameter with following approximate rib densities: at 60 mm. diameter there are 39-41 ribs; at 65, 39-41; 70, 40-42; 75, 41-43; 80, 42. Ribs on inner whorls slender and prorsiradiate becoming rursiradiate with strengthening of primary ribs on body-chamber. Poly- gyrate, simple and intercalatory secondary ribs occur occasionally. Constrictions developed over last two whorls. Microconchs 86-107 mm, in diameter with following 42 UPPER KIMMERIDGE CLAY OF DORSET approximate rib-densities: at 20 mm. diameter there are 34 ribs; at 25, 25; 30, 27; 35, 38. Ribs of inner whorls similar in style to macroconch, becoming a little coarser on outer whorl. Peristome bearing ventral horn up to 8 mm. long. HoLotyre. Macroconch, plaster cast C-73430. PARATYPE (ALLOTYPE). Microconch, plaster case C -73431. MATERIAL. Five specimens, including three macroconchs (two of which are plaster casts, and two microconchs (both plaster casts)). Horizon. Both type specimens are from 22 ft. below the Blackstone. STRATIGRAPHICAL RANGE. Upper Kimmeridgian, lower Wheatleyensis Zone, from 8 ft. above the Grey Ledge Stone Band, to 22 ft. below the Blackstone (A vertical range of 41 ft.). Description. Macroconch. FEvolute shell with a diameter of approximately 150 mm. Diameter of the umbilicus approximately 85 mm. At 60 mm. diameter the holotype has 39 ribs; at 65, 39; 70, 40; 75, 41; 80, 42. (Text-fig. 6). The ribs on the inner whorls are rectiradiate at the umbilical shoulder, then swing forwards to become fairly straight and prorsiradiate. The point of bifurcation of the ribs is fairly high on the whorl-side. The umbilical seam uncoils over the last half to three-quarters of a whorl. The ribs on the outer whorl gradually lose their prorsiradiate tendency and become straight and slightly rursiradiate throughout their length. The primary ribs become more widely spaced and very sharp, and the development of the secondary ribs becomes irregular. There are occasional polygyrate, simple and intercalatory ribs. There are several constrictions present. On the last half-whorl these are straight and are followed by a simple rib. The constrictions developed earlier are quite pronouncedly prorsiradiate, however. These oblique constrictions are preceded by a trifurcate rib which branches low on the whorl-side, and are followed by a simple rib. A part of the suture line is present on one specimen; it is not well-preserved, however, but does show stout saddles and lobes. Both lateral lobes appear to be trifid. The peristome is not completely preserved on any specimen but is presumably simple. Mucroconch. Neither microconch is particularly well or completely preserved. Both specimens are plaster casts. The paratype is quite evolute and has a diameter of 86 mm. The diameter of the umbilicus is 36 mm. There are an estimated 46 primary ribs on the last whorl. The ribs of the inner whorls are similar in style to those of the macroconch. At 20 mm. diameter there are 34 ribs; at 25, 35; 30, 37; 35, 38. (Text-fig. 6). The outer whorl has ribs of similar style, but they become a little coarser. There is one possible constriction present at the aperture. The ventral part of the peristome is damaged, but there is visible the basal 3 mm. of a horn, the original length of which may have been 7-8 mm. REMARKS. Most characters of this species are sufficiently distinctive to separate UPPER KIMMERIDGE CLAY OF DORSET 43 it from other species. It is distinguished from P. (V.) clavelli described above (p. 39) by the smaller adult size of the macroconch and the more coarsely-ribbed inner whorls. The microconch has a similar rib-density on its inner whorls to that of P. (V.) woodwardi (p. 45), but may be distinguished by the rib-style of both inner and outer whorls. Pectinatites (Virgatosphinctoides) laticostatus sp. nov. (Pl. x6) Diacnosis. Large Virgatosphinctoides developing massive widely-spaced primary ribs over last two whorls. Diameter 230-320 mm., with following approximate rib densities: at 20 mm. diameter there are 38 ribs; at 30, 42; 40, 45; 50, 47; 60, e270; 49-55, 80; 49-55; 90; 47-50; 100; 45-53; 110, 43-51; 120, 40-49 130, 38-45. Ribs of inner whorls rectiradiate to prorsiradiate becoming more widely spaced from ante-penultimate whorl onwards. Outer whorl extremely coarsely ribbed with abundant intercalatory secondary ribs. Microconch unknown. Hototyre. Plaster cast C.73416. MATERIAL. Six specimens, including two plaster casts (all macroconchs). Horizon. Holotype from “ dicey ” shales 19 ft. below the Blackstone. STRATIGRAPHICAL RANGE. Upper Kimmeridgian, lower Wheatleyensis Zone ranging from 3 ft. above the Grey Ledge Stone Band to 13 ft. 6 in. below the Black- stone (a vertical range of 47 ft.). DEscriIpTIon. Large evolute shell with a diameter of 232-320 mm. Diameter of umbilicus 130-180 mm. The holotype has 27 primary and approximately 68 secondary ribs on the last whorl. At 20 mm. diameter holotype has approximately 38 ribs; at 30, 42; 40,45; 50, 47; 60, 48; 70, 49; 80, 49; 90, 47; 100, 45; ITO, 43; 120, 40; 130, 38. The variation in rib density is shown in Text-fig. 5. The ribs on the innermost whorls are rursiradiate at the umbilical shoulder then swing forwards to become rectiradiate or slightly prorsiradiate. A coarsening of the ribs develops very early, and the last three whorls become progressively more coarsely ribbed. There is a gradual loss of the initial rursiradial curve of the ribs and they become straight throughout their length. The point of bifurcation of the ribs is high on the whorl-side, and the angle of furcation is somewhat larger (at least on the outer whorls), than is usual in this subgenus. The umbilical seam uncoils over the last half whorl. The outer whorl becomes extremely coarsely ribbed and abundant intercalatory secondary ribs are developed. At least two constrictions are present on the holotype, one on the penultimate and one on the antepenultimate whorl; they are both strongly oblique. In each case the constriction is preceded by a biplicate rib, which branches very close to the umbilical shoulder. A simple rib follows the constriction. The peristome is not preserved intact on the holotype, but is presumed to be simple. The microconch of this species has not been found hitherto. 44 UPPER KIMMERIDGE CLAY OF DORSET REMARKS. The very early development of widely-spaced ribs in this species is an uncommon character in this subgenus, and is therefore a very useful character for identification of this species. The problematical Virgatosphinctoides nodiferus Neaverson (1925 : 14, pl. 4, fig. 1) has a similar style of nbbing on its outer whorl, but its rib-development is not known in any detail. It is apparently geologically younger than P. (V.) laticostatus. Pectinatites (Virgatosphinctoides) grandis (Neaverson) (Pi a5 ities 35 Pie 18) 1925 Virgatosphinctoides grandis Neaverson : 13, pl. 4, fig. 2. MATERIAL. Eight specimens; seven macroconchs, one possible microconch. STRATIGRAPHICAL RANGE. Upper Kimmeridgian, upper part of Wheatleyensis Zone, between 3 and 17 ft. below the Blackstone. DeEscrIPTION. Macroconch. There is good agreement between one of the speci- mens here figured (Pl. 18) and the holotype, which came from Corton, Dorset. The former has a diameter of 365mm. The umbilicus has a diameter of 168mm. There are 24 primary and approximately 82 secondary ribs on the last whorl. At 80 mm. diameter there are 86 ribs, at go, 87; 100, 85; 110, 85; 120, 79; 130, 77; 140, 71; 150, 68; 160, 64. The variation in rib-density of the Kimmeridge forms is shown in Text-fig. 5. The ribs on the inner whorls are rursiradiate at the umbilical shoulder and gradually swing forwards, so that less than half way up the whorl-side they become prorsi- radiate. On the last umbilical whorl the ribs become more widely spaced, until on the outer whorl the primary ribs are very strong and distant from one another. There are often large numbers of secondary ribs to each primary rib. On some specimens there are regularly as many as five secondary ribs to each primary rib. The ribs become straighter on the last part of the body-chamber and slightly prorsi- radiate throughout their length. The secondary ribs tend to become less prominent and several primary ribs may be unbranched. Some intercalatory secondary ribs are usually present on the last whorl. There are several constrictions present. They are preceded by a compound rib, and followed by a simple rib. The peristome is presumably simple. Microconch. The figured microconch comes from the same horizon (17 ft. below the Blackstone) as the earliest recorded macroconch of this species. It is 112 mm. in diameter. The diameter of the umbilicus is 45 mm. There are approximately 70 primary ribs on the last whorl. At 40 mm. diameter there are approximately 68 ribs. The ribs of the inner whorl are similar in style to those of macroconch. The outer whorl is similarly ribbed, but has occasional simple and polygyrate ribs and at least one constriction. The aperture bears a horn which projects from the venter by about 7 mm. RemMArKS. There is a great disparity in size between the microconch (112 mm. diameter) and the associated macroconch (approximately 280 mm. diameter). However, it has been found that as a general rule the microconch is usually slightly UPPER KIMMERIDGE CLAY OF DORSET 45 coarser-ribbed than its macroconch at the same diameter. In this case the micro- conch has 68 ribs at 45 mm. diameter while the macroconch has approximately 70 at this diameter. No other fine-ribbed macroconchs occur at this horizon, so that there can be little doubt that this specimen is the microconch of P. (V.) grandis. The size of this species, coupled together with rib-style and density distinguish it from other species of the genus. Pectinatites (Virgatosphinctoides) grandis acceleratus subsp. nov. (Pl. 19) Diacnosis. Very large Virgatosphinctoides. General characters similar to P. (V.) grandis (Neaverson) but development of modified ornament occurring earlier. Ribs of outer whorl blunt and massive with few secondaries. Some intercalatory secondary ribs. HorotyPe. Macroconch C.73422, the only specimen. Horizon. 13 ft. above the Rope Lake Head Stone Band. (Upper Kimmeridgian, basal part of Hudlestoni Zone). DESCRIPTION. Large evolute shell with a diameter of approximately 375 mm. Diameter of the umbilicus 175 mm. There are 23 primary and approximately 60 secondary ribs on the last whorl. This subspecies is similar in most respects to P. (V.) grandis described above. It differs in that it becomes coarser-ribbed earlier in development, but the different types of sculpture present in P. (V.) grandis are repeated in the same order, but at smaller diameters. The peristome is simple. REMARKS. This subspecies is closely related to P. (V.) grandis and must be interpreted as a direct derivative of it. There is, however, a thickness of approxi- mately 35 ft. of rock between the highest recorded occurrence of P. (V.) grandis and the horizon from which this subspecies came. Most of the intervening rocks, however, are extremely poorly fossiliferous, so that collection failure is most probably responsible for the “ break ”’. No microconch of this subspecies has been found hitherto. Pectinatites (Virgatosphinctoides) woodwardi (Neaverson) (Pl. 20) 1925 Allovirgatites woodwardi Neaverson : 31, pl. 3, fig. 1. 1925 Allovirgatites robustus Neaverson : 32, pl. 3, fig. 3. 1925 Allovirgatites versicostatus Neaverson : 32, pl. 3, fig. 4. 1926 Allovirgatites woodwardi Neaverson ; Buckman, pl. 637. MATERIAL. Eleven specimens (five macroconchs, six microconchs). STRATIGRAPHICAL RANGE. Upper Kimmeridgian, Wheatleyensis Zone (just above the middle), ranging between 15 and g ft. below the Blackstone. 40 UPPER KIMMERIDGE CLAY OF DORSET DerscripTION. Macroconch. Fairly evolute shell with a diameter of 150-185 mm. Diameter of umbilicus 74-88 mm. The last whorl of the specimen here figured which is approximately 155 mm. diameter has an estimated 46 primary and 111 secondary ribs. The innermost whorls are not completely preserved in any specimen. At 50 mm. diameter there are 49 ribs, at 55,52; 60,54; 65,55; 70,56. (Text-fig. 4). The ribs on the inner whorls are rursiradiate at the umbilical shoulder, then swing forwards to become rectiradiate or slightly prorsiradiate and more or less straight. The point of bifurcation of the ribs is high on the whorl-side. The umbilical seam uncoils over the last half-whorl. (This uncoiling is not notice- able in the plate reproduced herein, owing to the crushing of the last umbilical whorl which gives an incorrect impression of the amount of this whorl exposed.) The ribs on the outer whorl become more widely spaced and stouter. The point of furcation is sometimes lower on the whorl-side. The number of secondary ribs per primary is variable, with as many as four secondary ribs to each primary rib. There are at least two possible constrictions on the outer whorl. The peristome is not preserved intact on any specimens, but is presumably simple. Microconch. Fairly evolute shell with a diameter of approximately 68-77 mm. The diameter of the umbilicus is 25~30 mm. The figured specimen has 49 primary and an estimated 92 secondary ribs on its last whorl. At 20 mm. diameter there are approximately 34 ribs; at 25, 35; 30, 36. The variation in rib density is shown in Text-fig. 4. The inner whorls are similar in rib style to those of the macroconch. The umbilical seam uncoils over the last half whorl (not well-shown on the figured microconch). The ribs of the outer whorl lose most of their initial rursiradial curve and are almost straight and rectiradiate. There is some slight variability in the rib direction, however, from slightly rursiradiate to slightly prorsiradiate. There are occasional simple and trifurcate ribs on the last whorl. The peristome is not preserved intact on any one specimen. The figured specimen shows it to be more or less straight, however. The ventral part of the peristome on this specimen projects about 2 mm. and is then broken, so that it is safe to conclude that a horn was originally present. REMARKS. The Dorset specimens agree closely with Neaverson’s figure of Allo- virgatites woodward. A. robustus Neaverson is merely an incomplete specimen of the same species, apparently a little thicker-whorled, but still very close to the former species. A. versicostatus Neaverson is also very close to this species and may possibly be the microconch. The differences do not appear to be sufficient to warrant specific distinction. The association of P. (V.) woodward: with P. (V.) wheatleyensis (Neaver- son) is also indicative of the similarity of the Dorset to the Oxford material. Pectinatites (Virgatosphinctoides) wheatleyensis Neaverson (2d Airc) 1925 Vuivgatosphinctoides wheatleyensis Neaverson : 12, pl. 1, fig. 1. 19560 Subplanites (Virgatosphinctoides) wheatleyensis (Neaverson) Arkell: 779, pl. 40, fig. 1. MATERIAL. Eleven specimens (five macroconchs, six microconchs). WWZNE NTIS TCIM LID RAID (End) (CLA 6 (Oy IDO Sl Bh 47 STRATIGRAPHICAL RANGE. Upper Kimmeridgian, Wheatleyensis Zone (just above the middle), ranging from 15 to g ft. below the Blackstone. DESCRIPTION. Macroconch. One specimen from Kimmeridge here figured, (Pl. 21, fig. 1) agrees extremely closely with the holotype figured by Neaverson. It has a diameter of 132 mm. The diameter of the umbilicus is 57 mm. There are approximately 64 primary and 156 secondary ribs on the last whorl. Another speci- men, which has well preserved inner whorls, has rib density as follows: at 25 mm. diameter there are 54 ribs, 30, 54; 35, 553 40, 57; 45, 58; 50, 58; 55, 60. The variation in rib density of the Kimmeridge specimens is shown in Text-fig. 6. The ribs on the inner whorls are rursiradiate at the umbilical shoulder, then swing forwards to become rectiradiate or slightly prorsiradiate. The point of bifurcation of the ribs is high on the whorl-side. The umbilical seam uncoils on the last half whorl. The outer whorl is very variable. The primary ribs become more widely spaced and are mostly polygyrate in some specimens. Others show the persistence of a more conservative type of ribbing, with more bifurcate than polygyrate ribs. One specimen shows the last few approximated suture lines, but as these are extremely poorly preserved, comparison with the suture line figured by Neaverson (1925, text-fig. B, 5) is not possible. However, it can be seen from these suture lines that the body-chamber is half a whorl in length. The peristome is simple and straight. Microconch. One specimen figured herein (C. 73426) has a diameter of 91 mm. The diameter of the umbilicus (which is somewhat elongated by crushing) is 36 mm. There are 56 primary and 122 secondary ribs on the last whorl. The inner whorls are badly preserved, so that it is not possible to determine the rib density accurately. There are, however, approximately 50 ribs at 35mm. diameter. The other figured specimen (C. 73427) has at 15 mm. diameter 47 ribs, at 20, 47; 25, 48; 30, 49. (Text-fig. 6). The ribs on the inner whorls are of a similar style to the macroconch. The umbili- cal seam uncoils over the last half whorl (which appears to correspond to the length of the body-chamber). The ribs on the outer whorl become slightly coarser, and there is the development of occasional polygyrate and simple ribs. The peristome bears a horn when completely preserved, and this is 17 mm. long on specimen C. 73426. It is quite strongly ribbed. ReMARKS. The horizon at which this species occurs in Dorset is much lower than that quoted by Arkell (1947 : 71). Although the ammonites from just below the Basalt Stone Band are undoubtedly somewhat similar in appearance to this species, the outer whorls are not the same. The associated fauna also confirms the identity of this species. Neaverson placed his Wheatleyensis Zone immediately above the Gvavesia Zones, which is too low in the succession. Pectinatites (Virgatosphinctoides) wheatleyensis minor subsp. nov. (Pli24 tie? 2) Dracnosis. Macroconchs small (103-108 mm. diameter) with following approxi- 48 UPPER KIMMERIDGE CLAY OF DORSET mate rib densities: at 25 mm. diameter there are 44 ribs; at 30, 48; 35, 46; 40, 48; 45, 49. Ribs of inner whorls slender and approximately rectiradiate. Outer whorl developing strengthened primary ribs, remaining approximated, with polygyrate furcation predominant. 2 HoLtotyre. Macroconch C.73429. MATERIAL. Two specimens (both macroconchs). Horizon. Both specimens from 17 ft. below the Blackstone (Upper Kimmeridgian, middle Wheatleyensis Zone). DESCRIPTION. Evolute shell with a diameter of 103-108 mm. (small for a macro- conch). Diameter of umbilicus 43-45mm. There are approximately 53 primary and 144 secondary ribs on the last whorl. In rib style this subspecies is very similar to P. (V.) wheatleyensis, but is somewhat more coarsely ribbed. At 20 mm. diameter there are approximately 44 ribs, at 30, 45; 35, 46; 40, 48; 45, 49. The point of bifurcation of the ribs is high on the whorl-side. The umbilical seam uncoils over the last half-whorl. The ribs on the outer whorl are identical in style with those of the holotype of P. (V.) wheatleyensis, being mostly polygyrate. The peristome is simple. REMARKS. The microconch of this subspecies is not known. Apart from the somewhat more coarsely ribbed inner whorls, and smaller adult size, this subspecies is similar to P. (V.) wheatleyensis. Its lower stratigraphical horizon suggests that it is a possible ancestor of this species. Pectinatites (Virgatosphinctoides) wheatleyensis delicatulus (Neaverson) (Piz7, tie. 2) 1925 Vuirgatosphinctoides delicatulus Neaverson : 15, pl. 1, figs. 2 and ?3. 1925 Allovirgatites tutcheri Neaverson : 30, pl. 3, fig. 2. 1926 Allovirgatites tutcheyi Neaverson ; Buckman, pl. 692. MATERIAL. Five specimens (four macroconchs, one possible microconch). STRATIGRAPHICAL RANGE. Upper Kimmeridgian, Wheatleyensis Zone (upper part) between 7 and 4 ft. below the Blackstone (see below). DescripTIon. Macroconch. The Dorset specimens agree closely with Neaver- son’s figure of the holotype, but are complete individuals. One specimen with a diameter of approximately 130 mm. and an umbilical diameter of 53 mm. has about 78 primary and 151 secondary ribs on the last whorl. The ribs on the inner whorl are a little finer and more dense than those of P. (V.) wheatleyensis. Some specimens have several constrictions of the last umbilical and the outer whorl. The main point of difference between this subspecies and P. (V.) wheatleyensis lies in the more finely ribbed outer whorl, and the constrictions which are usually present. The constrictions are preceded by a polygyrate or polyploke rib and are followed by a simple rib. In some cases this rib is prominent like the flare of Lyto- ceras. (As is the case with Neaverson’s examples). The peristome is simple. The body-chamber is a half whorl in length. UPPER KIMMERIDGE CLAY OF DORSET 49 Microconch. < P. hennahi ussheri x P. devoniensis No evidence P. ananas KH P. rozkowskae No evidence Frechastreaea F.. pentagona pentagona x x F., pentagona minima x x F. micrommata x F., carinata »< x F. goldfussi x x F. bowerbanki x 1 After Frech, 1885, pl. 2, fig. 5. ce similar to that described as “‘ thamnophylloid lateral”? by R6dzkowska (1960 : 31). The daughter corallite arises from the dissepimental tissue of the parent (Text-figs. 6, 7). In the early stages, the adult corallite becomes egg-shaped in cross-section with the more pointed end containing dissepimental tissue only, the septa having withdrawn from the epitheca in this area. This projection expands in size and septa begin to appear on the wall farthest from the parent. Some septa from the parent itself may extend slightly into the developing individual where the two are joined and these appear eventually to contribute to the latter’s full complement of septa. As the process continues, the daughter corallite grows more circular and forms a bilobed complex with the parent. At the same time, new septa are inserted on Fic. 6. Lateral increase in Peneckiella salternensis: a. OUM D553/p1; b. OUM D547/p1; c. OUM D547/p3 (same corallite as in 6b); d. OUM D553/pr. All x5. 196 COLONIAL PHILLIPSASTRAEIDAE FROM S.E. DEVON Bh Fic. 7. Lateral increase in Thamnophyllum caespitosum paucitabulatum: a. BM(NH) R46162d; b. BM(NH) R46163d. Both x3. both flanks of the daughter which now possesses most adult characteristics. During the bilobed stage, the two calices are wholly or partially separated by an irregular pseudotheca formed by the geniculation and mutual interference of the septa in the waist of the complex. The daughter corallite may be connected to the parent by extra-dissepimental tissue before final separation when the latter’s epitheca may be complete. In Thamnophyllum caespitosum two daughter corallites may be pro- duced at the same level but this has not been observed in Peneckiella salternensis. Thamnophyllum germanicum schoupper on the other hand displays exclusively axial increase similar to that found in many other species of Thamnophyllum. In all the specimens examined, either three or four daughter corallites are produced in each case. One specimen, in which increase is threefold, has been serial sectioned (Text-fig. 8). The parent corallite is about 5 mm. in diameter at the inception of increase which is marked by a striking change in skeletal deposition in the tabularium. After the last normal tabulae are laid down in the parent, the dissepimentarium continues to form as usual. In the tabularium, however, steeply inclined plates are secreted to form a cone (Text-fig. 8iii) which modifies upwards into a pyramid with as many sides as daughters are produced (Text-fig. 8iv, v). Upon these plates the new individuals are built up. As the cross-section of this axial structure changes in threefold increase from circular to triangular, three septa, each opposite and extending to join a corner of the triangle, become increasingly strongly developed. These delimit the areas of the new corallites. Thus each new corallite inherits roughly a third (or in fourfold increase, a quarter) of the mature septa and dissepiments of the adult. The first tabulae of each daughter are deposited between the base plate and the inherited dissepiments. Meanwhile the cross-section of the complex becomes increasingly trilobed (or tetralobed) and new septa are inserted along the inner margins of the developing corallites (Text-fig. 8vi, vii). The formation of the COLONIAL PHILLIPSASTRAEIDAE FROM S.E. DEVON a an a Fic. 8. Axial increase in Thamnophyllum germanicum schouppei: longitudinal-section after OUM D272; serial cross-sections after OUM D510/p5-10, p12-16. Spacing of sections in mm: i(p5)—0o-747—1ii(p6)—1-126—ili(p7)—0-712—iv(p8)—0-444—-v (po) 0:330—vi(p10)—0-533—vii(p12)—o-208—-viii(p13)—o-267—ix(p14)—0-495—-x(p15)— 0°574—xi(p16). All x5. GEOL, 15, 5. 22 198 COLONIAL PHILLIPSASTRAEIDAE FROM S.E. DEVON new horizontal structural elements proceeds from the periphery towards the axial area of the complex and by the time the process is close to completion, vertical growth has passed the apex of the base plates and the daughters are in intimate contact (Text-fig. 8vii). Subsequently, the newly formed sections of the dissepimentaria acquire adult characteristics with distinct traces of horseshoe dissepiments in cross- section (Text-fig. 8ix, x) and the new corallites complete their epithecae. Evidently no extra-dissepimental tissue (caenogenetic tissue of Soshkina 1953) is formed in Thamnophyllum germanicum schoup pet, for as soon as the normal dissepimental tissue is developed, the daughters become phaceloid (Text-fig. 8xi). (c) Variation. (i) Introduction. Sufficient material is available of many of the taxa described here to allow their variation to be studied in some detail. The statistics are grouped with the individual species and subspecies as part of their characterization but their great interest is in the general trends they show which are commented upon here. There are certain problems in the statistical treatment of south Devon material. Only one of the samples—Thamnophyllum germanmicum schoupper from Dyer’s Quarry—is demonstrably from a population preserved more or less in position of growth. In all other cases the faunas from which collections have been made have apparently suffered some post-mortem movement, the extent of which is difficult to assess. The coral colonies are broken and disorientated, in most cases preserved in massive limestones which have suffered more or less from tectonic stresses and recrystallization. The collections thus consist of fragmentary coralla which preclude ontogenetic study. The influence of ontogeny on the data obtained from these corals, however, appears to be small. Longitudinal-sections of corallites in the massive colonies show tabularium diameters to be virtually constant over most of their vertical growth. In this respect, they appear to behave in the same way as the phaceloid colonies, in which the influence of ontogeny is minimal in the extensive cylindrical parts of the corallites. All measurements have been made in cross-sections. In many colonial corals, a large number of corallites are unavoidably cut at varying degrees of obliquity, resulting in elliptical sections. As the corallites in the phaceloid colonies and the tabularia in all the colonial corals considered here are circular in sections normal to their axes, diameter measurements have been made along the minor axis of the ellipse. Care has been taken to separate ellipticity due to oblique section from that resulting from crushing or tectonic distortion. Corallites which appear to have been deformed in this way have not been measured. The following dimensions were recorded for each corallite: d corallite diameter. Measured only in phaceloid colonies and recorded to the nearest o-I mm. dt tabularium diameter. All of the corals described here have a clearly defined tabularium junction: recorded to the nearest 0°I mm. n number of major septa. Counts of the number of major septa were recorded with the corresponding d and/or dt value. COLONIAL PHILLIPSASTRAEIDAE FROM S.E. DEVON 199 The following were calculated in the case of all massive coralla: A average corallite area ina colony. As it is not possible to measure corallite diameter in a massive colony, the average corallite area in a colony was measured to facilitate comparison of corallite and tabularium size. Values of A were obtained by counting corallite numbers in a cross-sectional area measured by means of a transparent graticule divided into squares of o-5cm. side. The number of corallites was then divided into the corresponding area and the result recorded in square centimetres. Care was taken to calculate A from those corallites whose tabularia were also measured. This value is subject to some error due to the inclusion in its calculation of some obliquely sectioned corallites. At average tabularium area in a colony. Calculated from dtx (the mean tabularium diameter) of each colony by the formula for the area of a circle and recorded in square centimetres. From the above basic data, the following ratios were calculated: dt/d tabularium, corallite diameter ratio. This ratio could only be calculated for phaceloid colonies. n/d or n/dt septal or septal-tabularium ratio respectively. The septal ratio as normally applied to corals is the number of major septa divided by the corresponding corallite diameter, which in the present work could only be calculated for the phaceloid colonies. In the massive corals, the ratio of the number of major septa to the tabularium diameter, called the septal-tabularium ratio, was calculated. This ratio behaves in a similar way to the septal ratio but is not directly comparable with it. It will, of course, have higher values than corresponding septal ratios and may vary differently with size, depending on the variation in the dt/d ratio. At/A tabularium to corallite area ratio. This ratio is the approximate counterpart in massive corals of the dt/d ratio in phaceloid corals. The At/A ratio, however, has only been calculated as an average for each colony and not for individual corallites because of the difficulty of measuring accurately the area of an irregularly polygonal corallite. For the dimensions and ratios mentioned above, the following standard statistics were calculated: N sample size. The number of corallites in the sample, with the number of colonies given in parentheses. In the case of A, At, and the ratio At/A, N is the number of colonies. O.R. overall range. i mean value. s standard deviation. C.V. coefficient of variation. S.E.m standard error of the mean. These elementary statistics are dealt with in many books and their application to zoology and palaeontology is discussed in Mayr, Linsley & Usinger (1953) and 200 COLONIAL PHILLIPSASTRAEIDAE FROM S.E. DEVON Simpson, Roe & Lewontin (1960). Reference has been made to both these texts during the present work but principally, the writer has followed Imbrie (1956). The latter gives a clear and concise account of all the biometric techniques used here. It was found necessary, however, in view of the large size of most of the samples, to calculate the statistics for all characters except A, At and At/A by grouping the data in class intervals corresponding to the o-I mm. intervals in which the diameters were measured. The statistics calculated for each species and subspecies and the representative colonies are given in tabular form with the systematic descriptions (Tables 4-16). The colonies selected for individual treatment were those in which the most corallites could be measured. Usually it was possible to use colonies with 50 or more corallites but in cases of species with large calices, smaller numbers had to be used. The colony with the least data is Colony 1 of Thamnophyllum germanicum schouppei with 23 measured corallites. The data are also illustrated graphically (Text-figs. q-21). Inthe plots of dt against d, n against d or dt, n/d against d and n/dt against dt, diameter is recorded along the abcissa to the nearest o-I mm. As stated above, the character on the ordinate was averaged and plotted as a single point in each o-I mm. class. Thus points in the middle of the ranges of values on these graphs were based on many more observa- tions than those at either end. On all the graphs, the scatter of points approximated fairly closely to a straight line. When similar graphs are plotted for complete ontogenetic studies, it has been shown that the points usually fall on a curve of quite complicated form (see Voynovskiy-Kriger 1954). In the present case, however, the influence of ontogeny is thought to be slight and the data representative of the mature growth stages. Voynovskiy-Kriger’s curves approximate very closely to straight lines in maturity (his ‘“mature”’ plus “‘old’”’ stages), as is shown by the present results. Thus straight lines have been calculated from the data represented by the scatter of points on each graph. For ease of comparison, the lines only are illustrated in the text-figures. After Imbrie (1956), the reduced major axis was chosen as the most suitable line for problems of relative growth. For each line, the formula is given in the data tables as follows: r correlation coefficient a “ growth ratio ” b “initial growth index Where statistical discrimination has been used between congeneric species and subspecies, the procedure followed is again that detailed by Imbrie (1956). (ii) Variation in diameters. The assessment of size in these corals is mainly through the analysis of tabularium diameters as corallite diameters can only be measured in the phaceloid colonies. Variation in size may be the result of genetic, ontogenetic or ecological influences. Because of the parts played by the latter two factors, which are often not easy to assess, care must be taken in the significance placed on size differences and relative variation between colonies and species. In the present case, ecological control is largely an unknown factor although the influence of ontogeny may be regarded as minimal. | line of the form y = ax + b COLONIAL PHILLIPSASTRAEIDAE FROM S.E. DEVON 201 The variation in tabularium diameter in each of the taxa considered here is fairly similar (see Table 2). Values of C.V. range from 7°73 for the sample of I’vechastraea bowerbankz to 14°79 for the sample of Thamnophyllum germanicum schouppet. Varia- tion in the former, however, is almost certainly underestimated as only four incom- plete colonies were available for measurement. Values of C.V. for the other species of Frechastraea are all about ro. These figures are close to those obtained by Oliver (1960 : 83, table 7) for solitary cylindrical coral species and much lower than the variation he found in conical forms. From the present data it is impossible to say if massive corals are more or less variable than phaceloid forms. Although Thamnophyllum germanicum schouppet has the highest C.V. value, those for T. caespitosum paucitabulatum and Peneckiella salternensis are much the same as the values for many of the massive corals. In fact, the C.V. figure for the Barton Quarry sample of Haplothecia pengelly1, a massive marisastrid (see Scrutton 1967 : 274, table 2), is 15°75, which is higher than that for T. germanicum schoupper. On the other hand, there is a general tendency for C.V. values to be higher with increase in mean tabularium diameter. In the phace- loid corals, variation in corallite diameters is roughly the same from species to species, although always lower, than in the corresponding tabularium diameters. Oliver’s results with six solitary corals do not show such consistency and tabularium diameters are less variable than corallite diameters in two instances. Variation in size within colonies, with only two exceptions, was found to be less than that in the total samples of the same species or subspecies from the same locality. One exception is Colony 1 of Frechastraea bowerbanki (Table 12) which species has already been explained to be probably inadequately sampled. The other exception is Colony 1 of Phillipsastrea hennahi hennahi from Lummaton (Table 4). In this case, the C.V. value for dt in the colony only slightly exceeds that for the total Lummaton sample and is less than that for the sample from nearby Barton. There is usually a considerable range in the C.V. values for colonies of the same species or subspecies, even when the number of measured corallites in each colony is the same or nearly so. This can be illustrated with reference to Frechastraea goldfusst (Table 11) in which the C.V. values for ro colonies range from 10-01 to 4°12, the value for the total sample from Ramsleigh Quarry being Io-ro. As coral colonies are ideally the result of asexual reproduction from one sexually produced individual, variation would be expected to be lower in a single colony than in a sample of several colonies. From the results obtained here this is generally substantiated. The wide range in colonial variability may be due in part to several factors. Microenvironmental and general ecological influences undoubtedly exercise some control on variation but their effects cannot be easily assessed. In the case of phaceloid colonies, high C.V. values may be the result of the intergrowth of two or more colonies which have been sampled as one. As Oliver (1960 : 74) pointed out, it is virtually impossible to detect intergrowth when collecting material, and this may well have been responsible for the high C.V. values in the colonies of Thamno- phyllum germanicum schouppet (Table 13). Another factor for consideration is the fusion of several sexually produced polyps at an early stage of colony formation, COLONIAL PHILLIPSASTRAEIDAE FROM S.E. DEVON 202 Ib. €z I€- LI Z1-Q7@ Sto-o z¥o-o €90-0 Lz.€ 89-1 €v.z {9-0 L9-0 tg-0 69-I1 91-8 16-8 Cz.G zo. 91-9 gZ-8 FE.L 1S.Z GE.€ og-€ g6-€ co-€ Iz. Iv.Z Zo-€ 68-2 Lo-€ Z6- QI 16-61 zS.g1 Z6-Z1 L9-Z1 oh.z1 8g-O1 Zg-O1 62.41 Lz-€% €1I-O1 IQ-O1 ol. € IS.€ 69-2 CY.z CAS OCG to.z 99-6 II-O1 go-F1 g9-S gz-S 61-V Ni 0 is} nH Ses) Ss % — es Su S8§y SSFSVsgssy 25 2 2s SS ier Ss mwSee gs: gS Va 3 SS YS ss BSS 3. >= SS & eS & 3.8 8.8. eS, iS = SS 3 €1-9 $S0.0 1yuvqaa@nog eh PL. Lt OI-o ZS. QI-II OI-O1 €¢. assnf{pjos 4 I el €9-gI 640-0 Grig Z1-O1 get-6 60.1 puosvjuag puosvjuad “al g9-41 £90-0 Lo-Z£ DIDUIADI al IZ-Z1 z90-0 or-9 Co.o1 DuUUiM puosnjuagd “al “pyaryseuag = ‘q iwnykydoumpyT, = “I ‘vagsvsdyjyd = Yq “vanysvyreaq = “J “XIp SuIseoioUr JO Jopio Ur posuere ore soroedsqns pue sateds += ‘posATeue exe} pu S10} OeILYO [[e IOJ UOTZELIVA Jo s}USTOyZE09 pue suvoul oATye1edwI0j—z ATaV Viiv p/3p 3p COLONIAL PHILLIPSASTRAEIDAE FROM S.E. DEVON 203 recorded in Recent corals by Stephenson (1931 : 124). The effect of this phenomenon would generally be to increase the variation displayed by the colony. It is very difficult to separate the effects due to these different factors but it seems likely from the wide range in C.V. values shown, for example, by the colonies of F. goldfussi, that primary polyp fusion could be an important factor. The investigation of colonial variation described here differs from that made by Oliver (1960 : 73 ef seg.) through the latter comparing septal ratio C.V. values for individual colonies with those for populations of solitary cylindrical corals. In addition, Oliver analysed the total sample of Tvyplasma fascicularia from colony means rather than the basic corallite data. (iii) Variation in septal number and the septal ratios. With the exception of Thamnophyllum germanicum schouppe, the C.V. values for septal number are very similar in all the total samples. There appears to be no relationship between the degree of variation and the mean septal number (Table 2). It has long been known that septal number depends to some extent on calice size. When one is plotted against the other for both colonies and total samples, n shows a general increase with increasing d or dt in every case. Correlation coefficients in the total samples are usually about 0-9. The figure in individual colonies is slightly lower but much the same from colony to colony. Only rarely does the correlation coefficient drop below 0-7. These figures reflect the strength of the linear relation- ship between n and d or dt in mature individuals. A correlation between septal number and diameter is still reflected to a large extent in Table 2 as taxa with larger mean diameters have, with few exceptions, greater mean values for n. This relationship had led to the use of the septal ratio (septal coefficient of Voynovskiy-Kriger 1954) as a useful diagnostic criterion in coralspecies. Rdozkowska (1957) particularly, has used a form of this ratio, her Ms, in a detailed statistical study of species of Thamnophyllum and Macgeea from Poland. She showed (p. 9r and Table 6) that successively younger species and subspecies of Thamnophyllum have lower Ms values and similarly, fewer septa at a given diameter. A com- parison of Rozkowska’s figures with the thamnophyllids described here is shown in Table 3. It can be seen that the n values at d = 6 mm. for the English material follow the same trend as for the Polish specimens but do not fit exactly into the latter’s scale. On the other hand, the English Ms values (the English data has been recalculated for direct comparison with R6zkowska’s figures) are quite different from their approximate age equivalents in Poland and do not fit into a stratigraphical trend. It is interesting, however, to arrange the same taxa in order to increasing mean corallite diameter. This produces a series of decreasing Ms values somewhat less perfect than before for the Polish specimens but into which the English figures fit quite well. The values of n, however, show somewhat less perfect ordering than when arranged in stratigraphical series. Turning to the massive corals in Table 2, the mean n/dt figures for the representa- tives of Frechastraea and Phillipsastrea show a perfect series of decreasing values with increasing mean tabularium diameter. Furthermore, just such correlation exists, this time between mean d and mean n/d, in the corals described by Oliver 204 COLONIAL PHILLIPSASTRAEIDAE FROM S.E. DEVON TABLE 3.—Series in Ms and n (at d = 6mm.) for English (E) and Polish (P) thamnophyllids. Polish figures from Rdzkowska (1957 : 91 and table 6). Horizon Name Country Ms_ n (at d—6 mm.) 8 Middle T. superius 1p 2°20 15 a S fy Lower T. kozlowski 12 2°30 17 Upper T. caespitosum paucitabulatum E 3°50 19°35 a T. caespitosum caespitosum 12 3101 7/ 20 2 (I. germanicum pajchelae) P (3:60) (21) 2 Middle T. caespitosum E 3°15 20 0 T. germanicum germanicum 12 3°42 Bit T. gerymanicum skalense 1B 3°64 22 T. germanicum schoupper E 4°16 20°28 xd 4°11 T. geymanicum pajchelae 1p 3,60 21 4°14 T. germanicum schouppei E 4°16 20°28 5:36 T. geymanicum skalense P 3°64 22 5:68 T. caespitosum paucitabulatum E 3:50 19°35 (ca.) 6-00 T. caespitosum caespitosum 12 Bonz 20 6-17 T. caespitosum E 3°15 20 7:00 T. germanicum gerymanicum 12 3°42 21 9°28 T. superius 12 2°20 15 10-03 T. kozlowski 12 2°30 17 (1960). Thus the correlation between mean size and mean septal ratio is quite strong. The stratigraphical series in Ms values obtained by Rézkowska may simply reflect the tendency in her material for larger species and subspecies of Thamno- phyllum to occur at higher horizons. Between conspecific colonies, the septal or septal-tabularium ratio behaves in the same way. Colonies with greater mean diameters have, with very few exceptions, smaller values for the mean septal ratio. This trend is related to the fact that the septal ratio is not constant throughout ontogeny but decreases in value (see Voynovskiy-Kriger 1954) with increasing corallite diameter. When septal ratio is plotted against diameter, the relationship is more or less linear for mature corallites. In the present case correlation coefficients for the total samples range between — 0-90 and — 0-94 for phaceloid and — 0-96 and — 1-0 for massive corals. C.V. values for septal number and the septal or septal-tabularium ratio in con- specific colonies may show a considerable range. Furthermore, the relative variation in these characters and d or dt between colonies is usually different, although there is a slight tendency for the colony with the highest C.V. value for diameter to have high C.V. values for septal number and the septal ratio as well (see for example COLONIAL PHILLIPSASTRAEIDAE FROM S.E. DEVON 205 Table rr). In the case of n, the C.V. value reflects to some extent the rate of septal insertion as well as the amount of variation in diameter, and this masks any inde- pendent variation in the septal number. Colonies with similar variation in diameter, for example, show a strong correlation between a, the growth ratio, in graphs plotting n against d or dt and C.V. values for n. Similarly, C.V. values for n/d or n/dt in conspecific colonies also correlate roughly with values of a for graphs plotting n/d or n/dt against d or dt, and inversely with values of a for the plots of n against d or dt. (iv) Variation in size ratios. In the phaceloid forms, tabularium diameter increases evenly with increase in corallite diameter. The relationship between the two is strongly linear, reflected in the high values for the correlation coefficient (r > 0-95 inallcases). Only three phaceloid colonies have been analysed individually, those of Thamnophyllum germanicum schouppei. Their correlation lines on the graph plotting dt against d are virtually superimposed (Text-fig. 20). The ratios of tabularium to corallite diameter have very low C.V. values, partially reflecting the fact that they are virtually unaffected by changes in diameter. Measurements are confined, however, to mature corallites. Oliver (1960 : 71) has shown that during ontogeny in Siphonophrentis variabilis and Pseudoblothrophyllum helderbergium, this ratio decreases with increasing diameter. In his analyses of mature individuals, on the other hand, the ratio remains relatively constant with increasing diameter, as is shown in the present material. The relationship between tabularium and corallite size in massive corals is con- sidered in terms of their respective areas and is restricted to total samples. Analyses of A, At, and the At/A ratio show these characters to have high C.V. values. In the same sample there may be a considerable difference between the C.V. value for A and that for At, for example in the case of Phillipsastrea hennahi ussheri in which the former figure is more than double the latter (Table 5). This is undoubtedly due in part to the difficulty in calculating accurately the value of A. In most cases, however, the two figures are more nearly comparable. When At is plotted against A, there is always a clear tendency for the former to increase with increase in the latter (Text-figs. 12, 19). The scatter of points, how- ever, is considerable and is reflected in the low values for the correlation coefficient. Calculations using the formulae for the fitted lines show that the At/A ratio may increase or decrease slightly with increasing corallite area. Thus the analyses suggest that this ratio behaves similarly, if not so regularly, as the dt/d ratio and is largely independent of size in mature colonies. Vets None MAE C DESC RT Pa LO NiS The family name Phillipsastraeidae was erected by Roemer (1883 : 389) to include the genera Phillipsastrea and Pachyphyllum. It has, however, been little used until recently and taxonomists have usually classified the nominal type genus in the Disphyllidae. Hill (1939 : 224) erected the Disphyllidae to include both the typical Disphyllum and the related Prismatophyllum (considered by Lang, Smith & Thomas 1940 : 104 as a junior synonym of Hexagonaria) as well as Phillipsastrea (inter- preted by Hill 1939 : 236 to contain species both with and without horseshoe 206 COLONIAL PHILLIPSASTRAEIDAE FROM S.E. DEVON dissepiments) and the exclusively horseshoe bearing genera, Thamnophyllum, Macgeea and Trapezophyllum. Hill’s concept of the Disphyllidae was largely influenced by Lang & Smith’s (1935) discussion of these genera. Many subsequent workers followed Hill’s combination of horseshoe and non- horseshoe bearing forms in the same family. Stumm (1949 : 31) extended the range of genera included in the Disphyllidae but divided them among three subfamilies, the Pachyphyllinae, Disphyllinae and Eridophyllinae, characterised respectively by the presence and absence of horseshoe dissepiments and the development of an aulos. He considered Piillipsastrea to lack horseshoe dissepiments and placed it with Disphyllum, Hexagonaria and Bullingsastraea in the Disphyllinae. The Pachy- phyllinae included Pachyphyllum, Macgeea, Thamnophyllum and Trapezophyllum. Soshkina (1949), on the other hand, distributed the genera and species here included in the Phillipsastraeidae among three new families on the basis of morpho- logical and ontogenetic considerations. Genera she considered to develop horseshoe dissepiments and a “hexacoralloid’’ microstructure—Pachyphyllum, Macgeea, Thamnophyllum and Synaptophyllum—Soshkina (1949 : 76) grouped in the Thamno- phyllidae, equivalent to Stumm’s Pachyphyllinae. She placed Phillipsastrea, erroneously quoting (I95I : 95) P. radiata as type species and interpreting the genus as lacking horseshoe dissepiments, with Neocolumnaria and Schluteria in the Neo- columnariidae (1949 : 145). The third new family, the Peneckiellidae (1949 : 141) included Peneckiella and Megaphyllum. The latter was considered by Hill (1956 : 280) to be a synonym of Disphyllum. Soshkina (1951, 1952, 1954) continued to use this classification with the introduction of further genera to the latter two families and (1954 : 44) replacing the name Neocolumnariidae by Neocampophyllidae. Spassky (1960) followed Soshkina’s (1954) classification. Wang (1950 : 217) further enlarged the Disphyllidae by incorporating the acantho- phyllids into the family. He based his classification on a consideration of coral microstructure, defining the family chiefly on the development of one or more fan systems in the septal trabeculae. Wang’s use of the subfamily Phacellophyllinae (septal trabeculae with a marked area of divergence) corresponds very closely to the scope of the Phillipsastraeidae as interpreted herein. Like Lang & Smith (1935) and Hill (1939), however, he included species both with and without horseshoe dissepiments in Phillipsastrea. Rodzkowska (1953 : 8 et seq.) considered the three different classifications of Stumm (1949), Wang (1950) and Soshkina (1951). She decided that coral microstructure was of particular diagnostic importance and for this reason followed Wang’s classi- fication in principle. She did, however, remove the Acanthophyllinae from the Disphyllidae. In addition, she used the subfamily Pachphyllinae sensw Stumm in preference to the Phacellophyllinae sensw Wang as the former was conceived as exclusive of the genus Phillipsastrea. This genus Rézkowska interpreted as lacking horseshoe dissepiments and placed in the subfamily Disphyllinae. Hill (1954a, b) reintroduced the family name Phillipsastreidae (sc) effectively as a senior synonym of her (1939 : 224) Disphyllidae. Although the 1954 papers contain no familial diagnosis, this classification was later given in full by Hull COLONIAL PHILLIPSASTRAEIDAE FROM S.E. DEVON 207 (1956 : 179). She considered Phillipsastrea to lack horseshoe dissepiments and thus placed all the genera with disphyllid and marisastrid dissepimentaria in the Phillip- sastraeinae, and the horseshoe bearing genera in the Phacellophyllinae. Schouppé (1956) discussed at length the classifications of previous authors. He stressed the importance of the so-called ‘“‘ hexacoralloid ” microstructure developed in these corals with strongly reflexed dissepimentaria, and advocated their clear systematic separation. Two years later, Schouppé (1958) published a classification on this basis, stressing at the same time the presence of horseshoe dissepiments in the lectotype of Phillipsastrea hennali. He placed all the genera with an area of divergence in their septal trabeculae, usually but not always associated with horseshoe dissepiments, in the Phillipsastraeacea (sic.). Thus he elevated what had previously been a family or even a subfamily concept to the level of a suborder. Schouppé subdivided the Phillipsastraeacea into the Macgeeidae, with subfamilies Macgeeinae and Peneckiellinae, and the Phillipsastraeidae. He placed the genera Phillipsastrea and Bullingsastraea together in the Phillipsastraeidae and listed (1958 : 233) the family characteristics as massive astraeoid form, with a pseudotheca and never an epitheca between adjacent corallites, and with a broad dissepimentarium often developing horseshoe dissepiments. Phillipsastrea and Billingsastraea, how- ever, are not considered to be closely related (Oliver 1964 : 2; Scrutton 1967 : 276). Furthermore, Schouppé placed Haplothecia Frech, Pachyphyllum sensu Rozkowska (x953) and Pseudoacervularia sensu Rozkowska (1953) in his synonymy for Phillip- sastrea, all of which include species with a partial or complete epitheca around some or all corallites. The Macgeeidae sensu Schouppé, on the other hand, was defined by the presence of horseshoe and usually also flat dissepiments in a narrow dissepi- mentarium, with an epitheca surrounding individual corallites. All the genera included in this family by Schouppé, with the exception of Synaptophyllum, belong to the Phillipsastraeidae as defined herein. R6zkowska (1957 : 82) rejected her earlier classification in favour of that proposed by Soshkina (1949) to the extent of placing all horseshoe dissepimentate genera in the Thamnophyllidae. R6zkowska referred to Schouppé’s (1956 : 151) views but decided to separate those forms with horseshoe dissepiments from those without among the group with trabecular fans. Rdzkowska (1965 : 261), however, accepted almost completely Schouppé’s (1958) classification and erected a new family, the Marisastridae, for Phillipsastraeacea with an epitheca but no horseshoe dissepiments (see Scrutton 1967). On the other hand, Strusz (1965) rejected Schouppé’s (1958) familial and ordinal groupings, placing all genera with horseshoe dissepiments in the Phacellophyllidae. Genera with trabecular fans but no horseshoe dissepiments he included in the Disphyllidae. Strusz (1965 : 523) drew attention to a distinction between forms with “half fans” and full “ disphylloid fans’ within this family but placed no particular taxonomic significance upon it. The confused classification of this group of corals reflects the difficulty of distinguishing clear phylogenetic relationships between the genera involved. Mor- phology is extremely variable, particularly in massive forms, and results in general gradations between the characters considered diagnostic of different family and sub- 208 COLONIAL PHILLIPSASTRAEIDAE FROM S.E. DEVON family groups. A particular feature of more recent classifications resulting from this is the uncertainty in placing corals lacking horseshoe dissepiments but having a fan shaped arrangement of the septal trabeculae. Schouppé (1958) grouped them with the horseshoe bearing forms whilst Strusz (1965) grouped them with the disphyllids sensu stricto. All workers are agreed, however, that horseshoe dissepiments and the related trabecular fans must be considered of particular importance in taxonomy. Horseshoe dissepiments are unique to this group of Devonian corals and great stress has been laid, particularly by Soshkina (1949), Schouppé (1956) and Rdzkowska (1957) on the development of a pseudohexacoralloid trabecular pattern. The trabecular arrangement alone, however, has, in the writer’s opinion, been somewhat overstressed and does not justify the rank of suborder sensu Schouppé (r958). On the other hand, the development of specialized dissepimental types (horseshoe and peneckielloid dissepiments), with their related trabecular structure, defines with relative clarity a group of corals whose general morphological character- istics support a close family relationship. This group includes the genus Phillip- sastrea (as defined herein) and should be classified as the Phillipsastraeidae. The writer does not agree with Strusz (1965 : 524) concerning the use of this family name. It must be noted that the generic name Phillipsastrea has been used far more often in a disphyllid sense than the corresponding family name. The genus, however, should not be suppressed simply because its type species has been imperfectly known in the past and in this case, the change in concept of the family name will naturally follow that of the genus. The genera with reflexed dissepimentaria lacking horseshoe or peneckielloid dissepiments but possessing an open fan shaped arrangement of the trabeculae form a group of their own, intermediate in character between the Phillipsastraeidae as defined herein and the disphyllids sensu stricto. This is formalized in the family Marisastridae sensu Scrutton (1967). Finally, the Disphyllidae is here restricted to forms in which the trabeculae are arranged in half fans, or in a sub-parallel sense throughout on non-reflexed dissepimentaria. This family, in the writer’s opinion, should be interpreted to conform strictly to the dissepimental pattern of the type genus Disphyllum. Family PHILLIPSASTRAEIDAE Roemer 1883 1883 partim 1922 partim 1929 partum 1939 partim 1939 partim 1939 partim 1940 partim 1942c partim 1949 partim 1949 partim 1949 partim 1949 partim 1950 partim 1951 Phillipsastraeidae Roemer 389. Campophyllidae Wedekind 3. Pexiphyllidae Walther 117. Campophyllidae; Soshkina : 12. Cyathophyllidae; Sanford : 408. Disphyllidae Hill 224. Disphyllidae; Hill : 258. Disphyllidae; Hill : 186. Disphyllidae; Stumm : 31. Thamnophyllidae Soshkina : 76. Peneckiellidae Soshkina : 141. Neocolumnariidae Soshkina : 145. Disphyllidae; Wang : 217. Disphyllidae; Taylor : 183. COLONIAL PHILLIPSASTRAEIDAE FROM S.E. DEVON 209 partim 1952 LDisphyllidae; Lecompte : 470. partim 1953 Disphyllidae; Rézkowska : 9. partim 1954a Phillipsastreidae; Hill : 14. partim 1954b Phillipsastreidae; Hill : 107. partim 1955 Colummnariidae; Glinski : 86, partim 1956 Phillipsastraeidae; Hill : 279. 1957 Thamnophyllidae; Rézkowska : 83. partim 1958 Macgeeidae; Schouppé : 218. partim 1958 Phillipsastraeidae; Schouppé : 232. partim 1959 Disphyllidae; Middleton : 152. partim 1959 Phillipsastraeidae; McLaren : 22. partim 1960 Thamnophyllidae; Spassky : 44. partim 1961 Phillipsastraeidae; Semenoff-Tian-Chansky : 294. 1962 Thamnophyllidae; Soshkina : 308. partim 1962 Disphyllidae; Soshkina & Dobrolubova : 334. partim 1962 Phillipsastraeidae; Soshkina & Dobrolubova : 336. 1964 Phacellophyllidae; Pedder : 366. 1965 Phacellophyllidae; Strusz : 554. 1966 Phacellophyllidae; Pedder : 183. TYPE GENUS. Phillipsastrea d’Orbigny 1849 : 12. Diacnosis. Solitary, dendroid, phaceloid or massive rugose corals. Septa of two orders, major and minor, more or less dilated at the tabularium boundary which is usually sharply defined. Characterized by an area of divergence in the septal trabeculae centred on a complete or incomplete series of horseshoe dissepiments, peneckielloid dissepiments or a series of highly globose dissepiments occasionally modified to a horseshoe form. DIsTRIBUTION. Lower and particularly Middle and Upper Devonian of Europe, Asia, Australia and North America. Discussion. Of the genera assigned to this family, all but two have a more or less well developed series of horseshoe dissepiments. The exceptions are Peneckiella and Frechastraea gen. nov. Peneckiella may show considerable variation in dissepimental form but is charac- terized by the development of peneckielloid dissepiments. Frequently these are accompanied by sigmoidal, horseshoe and flat dissepiments in varying proportions. R6dzkowska (1960 : 32, 48, 50) who named the Peneckiella dissepimental types con- sidered them to be the breakdown products of a typical Thamnophyllum dissepi- mentarium, and that Peneckiella evolved from this genus. The species and subspecies of Frechastraea develop rare horseshoe dissepiments against the tabularium junction. This genus is thought to have evolved from Phillipsastrea principally through the gradual loss of horseshoe dissepiments and thus should be classified with the Phillipsastraeidae. The full list of genera here included in the Phillipsastraeidae is as follows: Phillipsastrea VOrbigny 1849 (Synonyms Smithia, Pachyphyllum, Medusae- phyllum, ?Streptastrea, Pseudoacervularia and ? Keriophylloides). Macgeea Webster 1889 (Synonyms Pexiphyllum and Protomacgeea). Thamnophyllum Penecke 1894 (Synonym Phacellophyllum). Trapezophyllum Etheridge 1899. 210 COLONDALY PHTE DLR SAS daRIASE ED PACH SERIO Sree. vaOiNi Peneckiella Soshkina 1939 (Synonyms Acinophyllum and Sudetia). Sulcorphyllum Pedder 1964. Bensonastraea Pedder 1966. Frechastraea gen. nov. (see p. 231). Synaptophyllum Simpson 1900 was long considered to develop horseshoe dissepi- ments and to belong to this group of corals. McLaren (1959), however, has shown that this genus had been wrongly used due to the misinterpretation of the type species. The genera fall roughly into two groups. Phillipsastrea, Sulcorphyllum, Bensonas- tvaea and Frechastraea usually have several rows of normal dissepiments as well as the modified ones, whilst Macgeea, Thamnophyllum, Peneckiella and Trapezophyllum commonly have only two series of dissepiments, one horseshoe or peneckielloid and the other usually flat. Both Schouppé (1958) and R6zkowska (1965) regarded the presence (in the second group) or absence of an epitheca between corallites as an additional criterion when they advocated a division at the family level along these lines. R6zkowska has particularly stressed wall structure as important in familial classification. Unfortunately, there are several exceptions to this grouping which mitigate against even subfamily status. Species of Phillipsastrea are known which have an epitheca around some corallites (Scrutton 1967 : 266) whilst a topotype of Tvapezophyllum elegantulum (B.M. (N.H.) R4600r) is pseudocerioid at least in part. The number of rows of dissepiments can be very variable in some species of Thamnophyllum (for example T. soshkinae (R6zkowska)) and Frechastraea (for example F. goldfussi (de Verneuil & Haime)). Further, a classification based on dissepimental rows would place Sulcorphyllum in a different group to Tvapezophyllum whereas the two genera appear to be closely related. Thus it is preferred not to recognize subfamily divi- sions in the Phillipsastraeidae. Genus PHILLIPSASTREA dOrbigny 1849 1849 Phillipsastrea d’Orbigny : 12. partim 1850 ©Lithostrotion; d’Orbigny : 106. partim 1850 Favastraea; d’Orbigny : 107. partim 1850 PLATE 8 Frechastraea pentagona (Goldfuss) minima (Rézkowska) Fic. 1. Cross-section (peel). GSM PF4031 (taken from GSM 73118); Lower Frasnian, Ramsleigh Quarry. X4. Fics. 2, 3. Longitudinal-sections (slide). GSM PF4032 (cut from GSM 73118); Lower Frasnian, Ramsleigh Quarry. x8. Frechastraea micrommata (C. F. Roemer) Figs. 4, 5. Cross- and longitudinal-sections (slides). Geol.-Pal. Inst. Bonn 34 (cut from lectotype); Frasnian, Ferques near Boulogne, France. X4. PLATE 8 Bull. By. Mus. nat. Hist. (Geol.) e. ee, a ns ” yy + bs BBS vy 3 ODD in PLATE 9 Frechastraea carinata sp. nov. Fic. 1. Cross-section (slide). OUM D3090 (cut from holotype); Lower Frasnian, road cutting 80 yds. west of Ramsleigh Quarry entrance. x6. Fic. 2. Cross-section (peel). BM(NH) R5634; Lower Frasnian, Ramsleigh Quarry. x6. Fic. 3. Longitudinal-section (slide). 0UM D300d (cut from holotype); Lower Frasnian, road cutting 80 yds. west of Ramsleigh Quarry entrance. x6. PLATE 9 Mus. nat. Hist. (Geol.) 15, 5 Bull. Br. as igs 7 By F ie Pep . i Sap eS F58 “ae Th ra 24 M Ww y yf my * 8 4 ¢ FY rer C Ug . ‘ 3 . ; ‘ 5 i ‘ 2 4 ta ae s Pay Yates pee BS PLATE 10 Frechastraea goldfussi (de Verneuil & Haime) Fic. 1. Cross-section (slide). OUM D540/pz. 5. Fics. 2, 3. Cross-sections (slide). OUM D539/p2. X5. Fic. 4. Longitudinal-section (slide). OUM D541/pz. x6. Fic. 5. Longitudinal-section (slide). OUM D540/p1. x8. All Lower Frasnian, Ramsleigh Quarry. Jed ‘5 tet. | SS. (7 By he) ay, re ia Hy EG aele FIG. 2. RIE, 3, PLATE 11 Frechastraea goldfussi (de Verneuil & Haime) Longitudinal-section (slide). OUM D540/pr. x8. Cross-section (peel). TM(JB) 318. x7. Figs. 1 and 2 both Lower Frasnian, Ramsleigh Quarry. Frechastraea bowerbanki (Edwards & Haime) Cross-section (peel). TIM 136/7; Lower Frasnian, Ramsleigh Quarry. x10. PReAWE n1 re a Bull. Br. Mus. nat. Hist. (Geol.) 15, 5 a Bh = > a? rey 4 . ae? Nes \ ¥ \ % ¥ a 29 GEOL. 15, 5 PLATE 12 Frechastraea bowerbanki (Edwards & Haime) Fic. 1. Cross-section (peel). TM 136/7. 3. Fic. 2. Longitudinal-section (slide). BM(NH) R46373. x6. Fic. 3. Longitudinal-section (slide). TM 136/7. x6. All Lower Frasnian, Ramsleigh Quarry. PEALE 12 Bull. By. Mus. nat. Hist. (Geol.) 15, 5 Wey Paar ittaye Pony there tt ert . ": Far oainpe yD ne We Papa tenp sma ore mele BSD {48 BaRMAEOD TAT HEE Oyen ee SL ietalet troy ty tuned ES alle tastier + RhOTP oestagsy rein Dearne PLATDE 13 Thamnophyllum germanicum schouppei nom. nov. Fic. 1. Cross-section (slide). OUM D509/p1; lower Givetian, Dyer’s Quarry. X50. Fic. 2. Cross-section (slide). Pal. Inst. Graz UPG 327 (cut from holotype); Middle Devonian, Torquay. X4. Fic. 3. Cross-section (peel). OUM D507/3/p1. x4. Fic. 4. Cross-section (slide). OUM D509/pt1. x4. Figs. 3 and 4 both lower Givetian, Dyer’s Quarry. Bull. By. Mus. nat Hist. (Geol.) 15, 5 PAE ors ie ~ PLATE 14 Thamnophyllum germanicum schouppei nom. nov. Fics. 1, 2. Longitudinal- and cross-sections (slide). OUM D509/p1. 4. Fic. 3. Longitudinal-section (peel). OUM D507/2/pi. x4. Fic. 4. Longitudinal-section (peel). OUM D508/4/p2. 4. All lower Givetian, Dyer’s Quarry. PLATE 14 Bull. Br. Mus. nat. Hist. (Geol.) 15, 5 PLATE 15 Thamnophyllum caespitosum paucitabulatum subsp. nov. Fic. 1. Cross-section (slide). BM(NH) R46163b; upper Givetian, Lummaton Quarry. ie Thamnophyllum caespitosum (Goldfuss) sensu lato Fic. 2. Longitudinal-section (slide). BM(NH) R46168a. x4. Fic. Cross- and longitudinal-sections (slide). BM(NH) R46171a. x4. Fic. 4. Cross-section (slide). BM(NH) R46168a. x4. Figs. 2-4 all middle Givetian, Wolborough Quarry. ee PLATE 15 Bull. By. Mus. nat. Hist. (Geol.) 15, 5 Fic. Fic. 2 Fia. Fic. Fic. Fic. Fie. NANA WwW PLATE 16 Thamnophyllum caespitosum (Goldtfuss) sensu lato Cross- and longitudinal-sections (slide). BM(NH) R46168a. x1. Longitudinal-section (slide). BM(NH) R46175b. x4. Both middle Givetian, Wolborough Quarry. Thamnophyllum caespitosum paucitabulatum subsp. nov. Cross-section (slide). BM(NH) R46163b. x1. Cross-section (slide). BM(NH) R46165a (cut from holotype). x1. Cross-section (slide). BM(NH) R46165a (cut from holotype). x4. Longitudinal-section (slide). BM(NH) R46165c (cut from holotype). Longitudinal-section (slide). BM(NH) R461656 (cut from holotype). Figs. 3-7 all upper Givetian, Lummaton Quarry. x4. PLATE 16 Bull. Br. Mus. nat. Hist. (Geol.) 15. 5 A ot ote gees, fy x Ne. ee ee To. 6 gts, a ae ‘<< iedeas Oe ae S, s np ae ow ae ge ee ~ PLATE 17 Thamnophyllum caespitosum paucitabulatum subsp. nov. Fic. 1. Cross-section (slide). BM(NH) R46165a (cut from holotype). x4. Fic. 2. Longitudinal-section (slide). BM(NH) R46163c. x4. Fic. 3. Longitudinal-section (slide). BM(NH) R46164d. x4. All upper Givetian, Lummaton Quarry. Peneckiella minor minor (F. A. Roemer) Fic. 4. Cross-section (slide). x3. Fic. 5. Longitudinal-section (slide). x6. Figs. 4 and 5 both Bergakad. Clausthal-Z. 117 (cut from holotype); Frasnian, Winterburg near Bad Grund, Germany. PLATE 17 Bull. By. Mus. nat. Hist. (Geol.) 15, 5 Fic. Fic. Fic. Fic. AWN PLATE 18 Peneckiella salternensis sp. nov. Cross-section (slide) OUM D546/pr. x3. Cross-section (slide). OUM D548/pr. (cut from holotype). x3. Longitudinal-section (slide). OUM D548/p3 (cut from holotype). Longitudinal-section (slide). OUM D546/p3. x4. All Frasnian, main Peneckiella horizon, Saltern Cove. x 4. PLATE 18 Bull. Br. Mus. nat. Hist. (Zool.) 15, 5 tet she ae = ¥ BY ADLARD AS bcs ee 15 May 1966 Za SOME STROPHOMENACEAN ak BRACHIOPODS FROM THE BRITISH LOWER Hi SILURIAN gy wos” L. R..M. COCKS - BULLETIN OF JE BRITISH MUSEUM (NATURAL HISTORY) EOLOGY on Vol. 15 No. 6 LONDON: 1968 Soc oo ci AAR AA “iy SOME STROPHOMENACEAN BRACHIOPOD FROM THE BRITISH LOWER SILURIAN BY LEONARD ROBERT MORRISON COCKS _ / De oe British Museum (Natural History) Pp. 283-324; 14 Plates; 1 Text-figure BULLETIN OF THE BRITISH MUSEUM (NATURAL HISTORY) GEOLOGY Vol. 15 No. 6 LONDON : 1968 THE BULLETIN OF THE BRITISH MUSEUM (NATURAL HISTORY), iistituted in 1949, 1s issued tn five series corresponding to the Departments of the Museum, and an Historical series. Parts will appear at irregular intervals as they become veady. Volumes will contain about three or four hundred pages, and will not necessarily be completed within one calendar year. In 1965 a separate supplementary series of longer papers was instituted, numbered serially for each Department. This paper ts Vol. 15, No. 6 of the Geological (Palae- ontological) sertes. The abbreviated titles of periodicals cited follow those of the W orld List of Scientific Periodicals. World List abbreviation : Bull. Br. Mus. nat. Hist. (Geol.). © Trustees of the British Museum (Natural History) 1968 LRUSE Ee Bs Or THE BRITISH MUSEUM (NATURAL HISTORY) Issued 14 May 1968 Price £2) 0s SOME STROPHOMENACEAN BRACHIOPODS FROM THE BRIEISH LOWER SILURIAN Biri ie ME COCKS CONTENTS I. INTRODUCTION ; é c C , : : ; ; 286 II. SYSTEMATIC DESCRIPTIONS . : é é é : F 6 286 Superfamily Strophomenacea King . ! : : : . 286 Family Strophomenidae King : : 5 : ‘ ; 288 Subfamily Strophomeninae King ‘ - : : ‘ 289 Genus Pentlandina Bancroft . j : : ; : 289 Pentlandina tavtana Bancroft . 2 ; . : 289 Pentlandina parva Bancroft . ; : ‘ : 291 Pentlandina parabola sp. nov. . é ; : : 292 Pentlandina sp. . i é ; 5 : 293 Subfamily Furcitellinae W Akers : : : ; 293 Genus Katastrophomena nov. : ; : ; 293 Katastrophomena woodlandensis (Reed) : : : 295 Katastvophomena scotica (Bancroft) . ‘ : : 296 Katastrophomena penkillensis (Reed) , ; ; 207 Katastrophomena sp. 9 : 3 : : 298 Subfamily Leptaeninae Hall & Clarke : 2 3 ; 299 Genus Leptaena Dalman : : : 3 ; : 299 Leptaena martinensis sp. nov. . : c : . 302 Leptaena haverfordensis Bancroft. : : ; 304 Leptaena valida Bancroft : ; : : F 305 Leptaena urbana Bancroft : P : : : 305 Leptaena conteymina sp. nov. . : j : : 306 Leptaena valentia sp. nov. : : : : 307 Leptaena valentia mullochensis Snes, nov. ; ; 309 Leptaena zeta Lamont . : : ¢ : ; 309 Leptaena rveedi sp. nov. . ; ‘ : : ; 310 Leptaena ziegleri sp. nov. : : : : : 311 Leptaena quadvata Bancroft . ; : : : B12 Leptaena purpurea sp.nov. . : : : > 313 Leptaena sp. ‘ : : : ; : 314 Genus Cyphomena @oones : ; : : . : 315 Subgenus Cyphomenoidea nov. . F 316 C. (Cyphomenoidea) wisgoriensis (L sso & Gilbert) : 316 Subgenus Laevicyphomena nov. . : . 2 317 C. (Laevicyphomena) feliciter sp. nov. : , : 317 Genus Mackerrovia gen. nov. ‘ F : 319 Mackerrovia lobatus (Lamont & Gilbert) ; : : 319 Genus Bellimurina Cooper. : : : : , 321 Bellimurina sp. . : : : : : : 321 Il]. AckKNOWLEDGMENTS : : ‘ : ‘ : : : 322 IV. REFERENCES . j : : F : : F 322 GEOL. 15, 6. 30 280 BRITISH LOWER SILURIAN SYNOPSIS The brachiopod family Leptaenidae is relegated to subfamilial rank within the Strophomenidae. All the known British Lower Silurian (Llandovery) species from the revised family Stropho- menidae are described and figured. Two new genera are erected: Katastvophomena, type species Stvophomena antiquata var. woodlandensis Reed 1917, and Mackeryovia, type species Brachyprion avenaceus var. lobatus Lamont & Gilbert 1945. Two new subgenera are erected within the genus Cyphomena Cooper 1956 (hitherto thought to be confined to the Ordovician) : Cyphomenoidea, type species Leptaena wisgoriensis Lamont & Gilbert 1945, and Laevicyphomena, type species C. (L.) felicitey sp. nov. Eight new species and one subspecies are erected, and the ecological communities of all the species recorded. i, INTRODUCTION THREE families of the superfamily Strophomenacea occur in the British Lower Silurian. One, the Stropheodontidae, has already been considered (Cocks 1967), and thus the present paper is concerned exclusively with representatives of the other two families, the Strophomenidae and the Leptaenidae. Strophomenids are widely distributed in the Lower Silurian of Britain, but are sporadic and rare at most localities. They have been recorded under the name ‘ Strophomena antiquata’ in most faunal lists. Leptaenids are rather commoner and have usually been referred to ‘ Leptaena rhomboidalis’. Although the Wenlock species of both families have been figured for many years, notably by Thomas Davidson in various works, the Llandovery species have remained for the most part poorly described. The stratigraphy and correlation of the British Llandovery is at the present time under review, and a joint paper by Dr. A. M. Ziegler, Dr. W. S. McKerrow and the present author is in course of preparation. Correlation between the various areas and the type area of Llandovery itself has been effected mainly by the use of evolving brachiopod lineages such as those of Stvicklandia (Williams 1951) and Eocoelia (Ziegler 1966). it, SYSTEMATEC DP SERIP TIONS Superfamily STROPHOMENACEA King, 1846 Classification In the recent Treatise (Williams et al. 1965), the classification of the Stropho- menacea is as follows: Superfamily Strophomenacea King 1846 (L.Ord.-L.Carb.) Family Strophomenidae King 1846 (L.Ord.-L. Dev.) Subfamily Strophomeninae King 1846 (M.Ord.-U.Sil.) Furcitellinae Williams 1965 (M.Ord.-L.Sil.) Rafinesquininae Schuchert 1893 (M.-U.Ord.) Glyptomeninae Williams 1965 (L.-M.Ord.) Oepikinae Sokolskaya 1960 (M.-U.Ord.) Leptaenoideinae Williams 1953 (U.Sil.-L.Dev.) Family Foliomenidae Williams 1965 (U.Ord.) Family Christianiidae Williams 1953 (Ord.) Family Leptaenidae Hall & Clarke 1894 (M.Ord.-L.Carb.) Family Stropheodontidae Caster 1939 (U.Ord.-U.Dev.) STROPHOMENACEAN BRACHIOPODS 287 The Stropheodontidae is divided into seven subfamilies which are outside the scope of the present paper; the family is distinct in possessing denticles, and was held with some justification to possess superfamilial status by Sokolskaya (1960 : 213). Of the remaining families, the Foliomenidae and the Christianiidae are confined to the Ordovician, leaving the Strophomenidae and Leptaenidae to be considered here. There is some doubt as to whether these two families are validly separable. Apart from the undiscussed list at the end of Hall & Clarke (1894 : 353-354), which divided what are now known as the suborders Strophomenidina and Triplesiidina into a rather arbitrary division between Strophomenidinae and Leptaenidae (thus creating the latter family), the two families were not divided again until 1956 in Cooper’s great work on the Chazyan brachiopods. Thus Williams in his paper on stropho- menoid classification (1953) did not mention the Leptaenidae: he divided the Strophomenacea into three families, the Strophomenidae, Stropheodontidae and Christianiidae, and the Strophomenidae was divided into only two subfamilies, the Strophomeninae and the Leptaenoideinae. In fact he specifically cited the Rafinesquinidae and Strophomenidae as synonymous (1953 : 8). Cooper (1956) divided the Chazyan Strophomenacea into three families, Leptaen- idae, Christianiidae and Strophomenidae. He briefly defined the three families as follows—Leptaenidae: “Compressed to faintly lenticular Strophomenacea with large apical foramen’ (1956 : 820); Christianiidae: ‘Smooth or finely costellate Strophomenacea having 4 prominent septa in the brachial valve’ (1956 : 859); and Strophomenidae: ‘ Strophomenacea having either normal or reversed convexity of the valves and a small foramen in the pedicle valve’ (1956 : 866). Thus, by those definitions, the only difference between a leptaenid and a strophomenid of normal convexity lies in the size of the foramen. As many species of Leptaena itself, e.g. L. salopiensis Williams, possess a foramen which is ‘ small, commonly sealed in adult shells’ (Williams 1963 : 461), this definition cannot be used in the type genus of the family. Even the geniculation and disc rugae may be seen on some genera, for example Luaia RoOmusoks 1956, ascribed to the Strophomeninae by Williams (1965 : H384). However, there does occur a group of strophomenaceans which are normally geniculate and often possess rugae over most of the disc, and which may conveniently be grouped with Leptaena itself. But, bearing in mind the wide differences between the Strophomenidae, Christianiidae and Stropheodontidae, familial recognition as the Leptaenidae seems an unwarrantedly high taxonomic rank. In this paper they will be treated as a subfamily within the Strophomenidae, the Leptaeninae, although even this separation may not be valid, and some of the subfamilies may be inter-phyletic. Although only three are considered in this paper, this arrangement leaves a total of seven subfamilies within the Strophomenidae, and their relative phylogenies leave much scope for discussion. Certainly the morphology of the two genera in the Leptaenoideinae, Leptaenoidea and Leptaenisca, seem to indicate descent from leptaenids rather than from other strophomenids, and this is supported by their known stratigraphical range. 288 BRITISH LOWER SILURIAN Ecological occurrence The species described in this paper are distributed as follows in the animal com- munities established in the British Llandovery (Ziegler 1965, Cocks 19674, Ziegler, Cocks & Bambach 1968). The list omits Leptaena urbana Bancroft, whose community is unknown. No strophomenids have yet been found in the Lingula community, which is thought to have been the shallowest. Eocoelia Pentamerus Stricklandia Clorinda Community Community Community Community Pentlandina tartana Bancroft : ; —= —- , x Pentlandina parva Bancroft ‘ 5 —- ~- x Pentlandina parabola sp. nov. b ; —- — — Katastvophomena woodlandensis (Reed) . — —- Katastvophomena scotica (Bancroft) : _- —- x — Katastvophomena penkillensis (Reed). ~ —- Leptaena martinensis sp. nov. : : —- -— — Leptaena haverfordensis Bancroft . ’ --- — Leptaena valida Bancroft. ; : - -- ‘ — Leptaena contermina sp. nov. ; : x » — Leptaena valentia sp. nov. . : : = z x = Leptaena zeta Lamont : F 5 — —- — Leptaena reedi sp. nov. 3 : 3 - —- . —- Leptaena ziegleyri sp.nov. . : : —- -— : — Leptaena quadvata Bancroft : ; = -- -— x Leptaena purpurea sp. nov. . c : = — —- C. (Cyphomenoidea) wisgoriensis (Lamont & Gilbert) : : ; -- y x ? C. (Laevicyphomena) felicitey sp.nov. . — — ™ — Mackerrovia lobatus (Lamont & Gilbert) — - : — Family STROPHOMENIDAE King, 1846 Apart from the Leptaeninae, there are only two groups of Strophomenidae which have so far been found in rocks of Llandovery age, as recognized by Williams (1951 : 115), who at that time referred them provisionally to Strophomena Rafinesque and Holtedahlina Foerste. The two groups are here referred to Katastrophomena gen. nov. and Pentlandina Bancroft 1949. These are placed in different subfamilies, the Furcitellinae and the Strophomeninae, and are the only post-Ordovician genera known in either sub- family. The chief subfamilial difference (Williams 1965 : H384, H386) is that the Strophomeninae are unequally parvicostellate and the Furcitellinae are costellate, but in fact later species of Katastrophomena (such as K. penkillensis (Reed) described below) become unequally parvicostellate. Thus in the two genera concerned, the chief differences in Silurian species lie in the internal structures of the brachial valve, and the usual presence of a strong fold and sulcus in Pentlandina, STROPHOMENACEAN BRACHIOPODS 289 Subfamily STROPHOMENINAE King, 1846 Genus PENTLANDINA Bancroft, 1949 1949. Strophomena (Pentlandina) Bancroft : 11, 13. 1965. Pentlandina Bancroft Williams : H384. 1966. Pentlandina Bancroft; Boucot et al. : 25. DiAGNosIs: Biconvex to convexo-concave small stophomeninids with prominent fold and sulcus, often with an ornament of parvicostellae interrupting broken rugae. TYPE SPECIES (by original designation); Stvophomena (Pentlandina) tartana Ban- croft 1949 from the Upper Llandovery of Deerhope Burn, Pentland Hills, Scotland. Species assigned : Strophomena (Pentlandina) tartana Bancroft 1949 : 13. Upper Llandovery, Pent- land Hills, Scotland. Strophomena (Pentlandina) parva Bancroft 1949 : 13, pl. 1, fig. 9. Upper Llan- dovery, The Frolic, Haverfordwest, Pembrokeshire. Pentlandina parabola sp. nov. Upper Llandovery, Purple Shale, Shropshire. Strophomena /urundo Barrande 1879, pl. 47, figs. I-32 pars. Wenlock, Bohemia, Czechoslovakia. Leptaena loveni de Verneuil 1848 : 339, pl. 4, fig. 5. Visby Marl (Upper Llan- dovery) Gotland, Sweden. Leptaena parvula Kindle 1915 : 14, pl. I, figs. 5-9. Stonewall Limestone, Sas- katchewan, Canada. Leptaena sinuosus Kindle 1915: 13, pl. I, figs. 1-4. Stonewall Limestone, Saskatchewan, Canada. ?Leptaena lewist1 Davidson 1847 : 59, pl. 12, figs. 22-24, Lower Wenlock, Rushall Canal, Staffordshire. Discussion. Pentlandina was raised to generic level by Williams (1965) and placed within the Strophomeninae. Boucot et al. (1966) recently removed the genus to the Leptaenidae on account of the pedicle muscle field and brachial processes and adductor plates (= trans-muscle septa?). It is, however, quite impossible to agree with this point, as each of the cited structures in Pentlandina is firmly attributable to the Strophomeninae rather than to the Leptaeninae. In fact the morphology of Pentlandina tartana, the type species described below, is not like any member of the leptaeninids. Taken with a shape so typical of the subfamily, there can be no doubt that the genus lies within the Strophomeninae. Gumnnarella Spjeldnaes 1957 has a similar ornament to Pentlandina, but is geniculate as opposed to biconvex and sulcate. Pentlandina tartana Bancroft (Pl. 1, figs. 1-6) 1868. Stvophomena antiquata (J. de C. Sowerby); Davidson : 17, pl. 2, figs. 21-23. 1871. Strophomena antiquata (J. de C. Sowerby); Davidson : 299 pars, pl. 44, figs. 7-9 only. 1949. Strophomena (Pentlandina) tartana {Lamont MS) Bancroft : 13, on pl. 1, fig. To. 290 BRT SIO Were Re Sie Waa AGN D1aGnosis: Small strophomeninid with prominent fold and sulcus. Fine orna- ment of differentiated parvicostellae which break irregular small weak rugae. DeEscrRIPTION. Exterior. Biconvex to slightly resupinate with a semicircular outline and small ears. Large sulcus in pedicle valve with corresponding fold in brachial valve. Fine ornament of differentiated parvicostellae, and very weak irregular rugae of small wavelength distributed over all the shell. Interarea of variable size, larger in the pedicle than in the brachial valve. Large delthyrium closed at the apex by a small pseudodeltidium (Plate 1, fig. 4). Information un- certain as to the chilidium, there is at least a small one developed, but it is not clear whether or not part of the delthyrium remained open. Pedicle interior. Straight hingeline with prominent teeth connected to the posterior end of a strong pair of short muscle bounding ridges which project anteriorly as much as dorsally. Short median septum starting close to the apex and dividing the muscle bounding ridges before stopping abruptly, leaving an inclined slope about 2 mm. long at its anterior end, which merges with the valve floor. Diductor scars short, leaving concentric growth ridges. Adductor scars elongate, close to, and partially on, the median septum. Shell thick posteriorly with prominent pseudo- punctae, thin anteriorly, often with an interior reflection of the exterior ornament. Brachial interior. Widely divergent prominent socket plates which curve slightly posteriorly at their lateral extremities. They are joined medianly to the bilobed cardinal process lobes, which are directed ventrally and slightly posteriorly. The process lobes are connected to a weak shaft, which in some specimens bifurcates anteriorly, in others reunites to form a weak median septum. Trans-muscle septa variably developed, but including in all specimens a prominent anterior pair stronger than and subparallel with the median septum. These septa are often slightly flared ventro-laterally. Owing to the mass of structures in the brachial valve presumably mainly used for the support of adductor muscles (although some could have been rudimentary brachiophore supports) the scars and shape of the muscles are not readily distinguishable. Thick shell with prominent taleolae antero-laterally. LECTOTYPE (here selected). BB 31447 (Plate 1, figs. 1, 2), a brachial valve in the Davidson collection. One of a number of specimens which made up the material for the composite figures cited by Bancroft. With the specimens there is a label in Davidson’s handwriting ‘ Strophomena antiquata Sow. bed D. Wenlock Shale, Pentland Hills, found by Mr. Henderson.’ The specimens are from an horizon now known to be of Upper Llandovery age in the North Esk Inlier of the Pentland Hills, Scotland (Mitchell & Mykura 1962 : 12 e¢ seq.). DIMENSIONS (in cm.—all specimens from type locality) il. Ww. BB 31447 Lectotype. Brachial valve . 0-QI approx. 1:6 B 8485 Brachialvalve . : : 0:92 broken BB 31450 Brachial valve. ; : 0-86 1°39 B 13614 _ ~+Pedicle valve ; , : OV72 129) BB 31448 Pedicle valve : 5 : 0°93 approx. I°5 STROPHOMENACEAN BRACHIOPODS 291 Discussion. In erecting the species, Bancroft (1949 : 13) quoted those of David- son’s figures of Strophomena antiquata which came from the Pentland Hills. He also figured a specimen (Plate 1, fig. 10) which is of part of a pedicle internal mould. This specimen is not in the Sedgwick Museum and Mr. A. G. Brighton informs me (im litt. March, 1967) that its whereabouts are unknown. In many copies of Ban- croft’s privately published paper, Dr. A. Lamont has deleted reference to the figure in the species description, and substituted ‘S. cf. penkillensis’ as the caption for Plate 1, fig. 10, and indeed the specimen is probably of the latter species and may be attributed to Katastrophomena of the present paper. Thus, to stabilize the identity of Pentlandina, Davidson’s figures have been selected as lectotypes of the type species by Havlicek (1968 : 75). The original specimens used by Davidson are selected above. Apart from the Pentland Hills, the species has not been found in form identical with the type. There is, however, a larger form, represented as yet by only one pedicle and one brachial valve, probably attributable to P. tavtana, found in one locality in the southern Welsh Borderland. This is at Cullimore’s Quarry, Charfield Green, Gloucestershire, which lies in Tortworth Beds of C, age, part of the Tortworth Inlier. The dimensions are as follows (in cm.). Il. Ww. BB 31470 Pedicle valve . : approx. 1:3 approx. 2-2 BB 31471 Brachial valve. : : 1°39 approx. 2-3 The larger size may well be a phenotypic feature, as there seem to be no differences in ornament, internal structures or general proportions between the Tortworth and Pentland Hills specimens. Pentlandina parva Bancroft (Rip wriesa7. 3) 1949. Strophomena (Pentlandina) parva Bancroft : 13, pl. 1, fig. 9. 1951. Holtedahlina parva (Bancroft) Williams : 118, pl. 7, figs. 8-10. Discussion. A full description of the species is given by Williams (1951), and photographs of it are included in the present paper only for completeness and for comparison with P. tartana and P. parabola. The species is rare, it has so far been recorded only from the type locality, in Uzmaston Beds (Upper Llandovery) of the Frolic, south-west of Uzmaston Farm, Haverfordwest, Pembrokeshire. This is the same locality (Locality K of O. T. Jones on Sedgwick Museum labels) from which comes Leptaena quadrata, dealt with later in this paper, and it is interesting to note that neither species has been found except at the type locality. To judge from the figures, the species seems to have a close relative in North America, the P. cf. parva of Boucot et al. (1966 : 25, pl. 6, figs. 16-18, pl. 7, figs. 1-10). The American species is, however, twice the size of the Welsh, no mention is made of any prominent fold and sulcus, and the arrangement of the brachial interior seems closer to P. parabola than to P. parva; all these features give a definite impression of specific difference. BRITISH LOWER SILURIAN 1S) Ne} Ww Pentlandina parabola sp. nov. (Pl. 1, figs. 9-12) Diacnosis. Alate Pentlandina with pronounced fold and sulcus, and two pairs of converging muscle ridges in the brachial valve. DeEscrIPTION. Exterior. Outline semicircular but laterally alate. A deep ven- tral sulcus and dorsal fold are present, but lateral to these, minor frills are some- times developed at the valve margin. Ornament of parvicostellae, with fine threads between them, more prominently developed in the median plane. New ribs arise by intercalation. In addition, small, even concentric rugae, broken by the parvi- costellae are present, forming an irregular pattern. Medium-sized interarea, with an open delthyrium, bounded laterally by plates (Pl. 1, fig. 10) and a vestigial chilidium. Very small supra-apical foramen, atrophied in adult specimens and not always on the median plane. Pedicle interior. Straight hingeline with prominent teeth which form the posterior end of a pair of muscle-bounding ridges of diamond shape, although they only some- times meet at their anterior, enclosing a small diductor muscle scar which is weakly impressed. No information on the size and shape of the adductor muscle scars. Weak, broad median septum not extending anteriorly of the bounding ridges. Interior reflection of the ornament usually seen. Thin shell with no prominent taleolae showing. Brachial interior. Divergent socket plates, curving antero-laterally. Small ven- trally directed cardinal process lobes. Scarcely visible platform and weakly im- pressed muscle scars, but bounded laterally by two pairs of plates starting posteriorly at the lateral ends of the socket plates and set diagonally so that they converge anteriorly (but do not meet). Each plate is convex laterally and set at an angle to the valve floor. A very weak median septum runs for a short distance anterior of the bounding ridges. HoLotyPe. OUM Cr13507, a partly exfoliated pedicle valve from the Purple Shale (Upper Llandovery) of Domas, Shropshire. Grid Ref. SJ/5936 0062. DIMENSIONS (in cm.—all specimens from Domas) 1. Ww. OUM C13507 Holotype Pedicle valve . 0-89 1007/0) OUM C13504 Paratype Pedicle valve . 0:68 1322 OUM C13505 Paratype Brachial valve . broken 2 OUM C13509 Paratype Brachial valve . 0-26 0-51 Discussion. Length measurements were made in the median plane, but in old individuals there is some shell antero-laterally to this. In the small specimen (OUM Cr13509) the fold has not yet started to develop. The species is known only from the Purple Shale of Shropshire and is rare, although it occurs as 2°% of the population at the type locality. Single specimens are known STROPHOMENACEAN BRACHIOPODS 293 from two other localities, Boathouse Coppice [Grid. Ref. SJ/6205 0398] and Devil’s Dingle [Grid Ref. SJ/6392 0547). P. parabola differs from P. parva (Pl. 1, figs. 7, 8) in having a still more pronounced fold and sulcus, less distinct ornament and in better differentiated alae (without, however, being more transverse). In addition the strength, proportion and arrange- ment of the brachial internal structures are dissimilar in the two species. From P. tartana the new species differs in being more apsacline, more alate, and in having a frilly margin, in having a relatively smaller total muscle area and a differently shaped socket arrangement and muscle area in the brachial valve. In addition the rugae are more prominent, the interior less strongly papillose and the whole shell less thick. Pentlandina sp. (RIs, fieear3)) In one block from the Bog Mine, West Shropshire [Grid Ref. SO/3510 9815), there is a single broken pedicle valve, BB 31299, which may be referred without doubt to Pentlandina, on its general shape, particularly its prominent sulcus, and also on the character of the muscle field and bounding ridges. It seems fairly closely related to Pentlandina parabola but its shell is rather more irregular; in addition no trace of the distinctive ornament may be seen, but this could possibly be due to the coarse quartzite matrix. The length is 1-02 cm. and the estimated width approximately 1-6 cm. The specimen is significant in being the earliest representative of the genus so far known, with an age of Middle Llandovery. Subfamily FURCITELLINAE Williams, 1965 Genus KATASTROPHOMENA nov. DracGNosis. Resupinate strophomenid with an ornament of irregular subequal costellae in early stocks, but may be parvicostellate in later stocks. With dental plates and weak trans-muscle septa. TYPE SPECIES. Strophomena antiquata var. woodlandensis Reed 1917. SPECIES ASSIGNED: Strophomena antiquata var. woodlandensis Reed 1917 : 902, pl. 18, figs. 20, 21, pl. 19, figs. 1-5. Middle Llandovery, Woodland Point, Girvan, Ayrshire, Scotland. Orthis antiquata J. de C. Sowerby in Murchison 1839 : 630, pl. 13, fig. 13. Wen- lock Shale, Woolhope, Herefordshire. Strophomena dura Bancroft 1949 : 15, pl. 1, fig. rr, Wenlock Limestone. Strophonella penkillensis Reed 1917 : 900, pl. 18, figs. rr-13. Upper Llandovery, Bargany Pond Burn, Girvan, Ayrshire. Orthis scabrosa Davidson 1847 : 61, pl. 13, figs. 14, 15. Wenlock Limestone, Benthall Edge, Shropshire. 294 BRITISH LOWER SILURIAN Strophomena scotica {and var. alveata| Bancroft 1949 : 12, pl. I, figs. 4-7, non fig. 3. Gasworks Mudstone (Lower Llandovery) Haverfordwest, Pembrokeshire. Strophomena woodlandensis geniculata [Bancroft MS nom nud.\ Williams 1951 : 117, pl. 7, figs. 5-7. Upper Llandovery (C,), Llandovery, Carmarthenshire. Strophonella costatula Hall & Clarke 1894 : 359, pl. 84, figs. 15, 16. Niagara Group, Louisville, Kentucky, U.S.A. Strophomena radiireticulata Twenhofel 1928 : 192, pl. 17, figs. 1-3. Jupiter Formation (Upper Llandovery-Wenlock), Anticosti Island, Canada. ?Strophomena sibirica Andreeva in Nikiforova & Andreeva 1961 : 183, pl. 38, figs. I-7. Species possibly congeneric : Strophomena rugata Lindstrom 1860 : 371, pl. 13, fig. 14. Visby Marl (Upper Llandovery) Gotland, Sweden. (Possibly a young strophomenid). Strophomenar pectenoides Andreeva in Nikiforova & Andreeva 1961 : 184, pl. 39, figs. 1-6. Middle Llandovery, Siberian Platform, U.S.S.R. Strophomena lindstronu Gagel 1890 : 43, pl. 3, fig. 12, Upper Silurian, east Baltic. (May be a davidsoniacean). Discussion. Unfortunately the genera of Upper Ordovician Strophomenidae have not yet been evaluated as a whole, and several are not yet comprehensively illustrated. It is probable, however, that the fairly compact group in the Silurian may be classified together in one genus to include all species not in Pentlandina or the Leptaeninae. All these species are resupinate and have a distinctive irregu- larly costate ornament, at least in the early Silurian. In addition, their internal characters, although often dissimilar at the specific level, clearly indicate their congeneric nature. The new genus here erected to include these species is placed in the Furcitellinae, mainly owing to the similarities with Furcitella Cooper 1956 itself, particularly in the ornament and internal morphology, but the Chazy genus is biconvex and has a large foramen. Whether the two subfamilies Strophomeninae and Furcitellinae really require separation is another matter; the division (Williams 1965) seems to have been made mainly on ornamental grounds. In fact, although they are here left in separate subfamilies, Katastrophomena shows much resemblance to Stropho- mena itself in morphology, especially shape, differing mainly in the presence of dental plates and in the ornament, although, as mentioned above, Katastrophomena has end members with differentiated parvicostellae. The only other strophomenid with which the new genus may be compared is Microtrypa Wilson 1945, from the Upper Ordovician of Ontario, Canada, which is particularly poorly known, but which appears to differ in ornament and brachial interior. In the British Llandovery there are thus three species, K. woodlandensis and its subspecies geniculata, K. scotica and Kk. penkillensis, each of which will now be reviewed. STROPHOMENACEAN BRACHIOPODS 295 Katastrophomena woodlandensis (Reed) (Pl. 2, figs. I-10) 1883. Stvophomena antiquata (J. de C. Sowerby); Davidson : 193, pl. 15, figs. 12-14. 1917. Strophomena antiquata (J. de C. Sowerby) var. woodlandensis Reed : 902, pl. 18, figs. 20, 21, pl. 19, figs. 1-5. 1949. Strophomena woodlandensis Reed Bancroft : 11. 1951. Stvophomena aff. woodlandensis Reed; Williams : 118, pl. 7, fig. 4. Diacnosis. Katastrophomena with coarse, irregular costae, variable shape, and variable brachial internal characteristics. DeEscrIPTION. Exterior. Variably resupinate, ranging from flat to almost geniculate. Ornament of thick irregular costae of subequal size. New costae arise mainly by intercalation, but sometimes by branching. Prominent growth lines seldom developed. Large interarea. Delthyrium completely closed by large pseudodeltidium and chilidium. Pedicle interior. Straight hingeline with prominent teeth which form the posterior end of a pair of muscle-bounding ridges of variable shape but which generally curve inwards without meeting anteriorly. Median septum variably developed, on either side of which are faintly impressed blade-like adductor muscle scars inside the more strongly developed diductor scars upon which may be seen both faint concentric growth lines and also radiating striae. Fairly thick shell, particularly posteriorly, but large taleolae not developed. Brachial interior. Strong pair of widely divergent socket plates quite separate from the small erect bilobed cardinal process. Very variable minor platform and muscle area structures (compare Pl. 2, fig. 6, 8, 9). A median septum is usually present, which bifurcates to a greater or lesser degree, trans-muscle septa are occa- sionally present. LectotyPE, here selected. B 54490, a pedicle valve, figured by Reed (1917, pl. 18, fig. 21) from the Middle Llandovery of Woodland Point, Girvan, Ayrshire, Scotland. Gray Collection. DIMENSIONS (in cm.—all specimens from Woodland Point) If WwW. B 54490 Lectotype. Pedicle valve . Pay Bron B 73012 Brachial valve . 3 : 2°05 SielGy7/ BB 31420 Brachial valve . ; : 1°54 2°25 BB 31422 Brachial valve. : : 1-78 2°27 Discussion. There is a large amount of variability in Katastrophomena wood- landensis, particularly in two respects; the degree of valve convexity, and the development of internal brachial structures. Both points may be seen in Pl. 2; where figs. 5-7 show specimens in which the valve direction has changed in the median plane by more than go degrees, whereas figs. 8 and 9 show specimens which are only slightly concave. Similarly the contrast in the brachial interiors between figs. 8 and g is self-evident. 296 BRITISH LOWER SILURIAN K. woodlandensis is not common except at the type locality, but the species is also present in the Middle Llandovery of the type area. Two specimens have been found, SMA 30006 (Williams 1951 : 118, pl. 7, fig. 4) and BB 31409, collected by the author from B; mudstones in a small disused roadside quarry [Grid Ref. SN/ 760 300]. A subspecies has also been erected, K. woodlandensis geniculata {Bancroft 1949 nom nud.| Williams (1951 : 117, pl. 7, figs. 5-7), whose type specimens are refigured here for convenience (pl. 3, figs. 1, 2). This is another rare form from C, beds in the Llandovery area. It is best left as a separate subspecies, as, although the brachial valve could well be identified as K. woodlandensts (s.s.), the form of the pedicle muscle field shows some affinity with K. scotica described below. Further collecting at the type locality has failed to produce more material. The chief differences between K. woodlandensis and K. scotica are in the shapes of the pedicle muscle field and bounding ridges and in the stronger median septum usually present in Kk. scotica. The chief difference between these two species and K. penkillensis les in the differentiated ornament of the latter. Katastrophomena scotica (Bancroft) (Pl. 3, figs. 3-9) 1871. Strophomena antiquata (J. de C. Sowerby); Davidson pars : 299, pl. 44, figs. 21, 22 only. 1949. Strophomena scotica Bancroft : 12, pl. 1, figs. 4, 5, non fig. 3. 1949. Strophomena scotica var. alveata Bancroft : 13, pl. 1, figs. 6, 7. 1951. Stvophomena scotica Bancroft; Williams : 116, pl. 7, figs. 1-3. Diacnosis. Katastrophomena with irregular costae. Pedicle muscle field diamond-shaped posteriorly with bounding ridges drawing out anteriorly to become sub-parallel in extreme cases. DEscRIPTION. Exterior. Variably resupinate. Ornament of thick, irregular costae of subequal size. New costae arise by bifurcation and intercalation. Promi- nent concentric growth-lines often developed. Large interarea, with at least a small pseudodeltidium and possibly a large, entire one. Large chilidium. Pedicle interior. Straight hingeline with prominent teeth which form the posterior end of a pair of variably developed muscle bounding ridges of curved to diamond shape, not meeting anteriorly, but sometimes drawn out and extending sub-parallel for a short distance anteriorly. Weak median septum running from the apex to approximately the ends of the muscle bounding ridges. On either side of this septum are sometimes impressed the pair of small blade-like adductor muscle scars. Strongly impressed diductor muscle scars on which concentric growth lines are often seen. Brachial interior. Large pair of strongly divergent socket plates on either side of, and distinct from, the erect bilobed cardinal process. Between the lobes is sometimes preserved a small thin blade. Median septum usually strong, variably bifurcate. Other structures very variable, trans-muscle septa and muscle bounding ridges are sometimes weakly developed. STROPHOMENACEAN BRACHIOPODS 207 LecToTyPE, here selected. SMA 32194, a pedicle internal mould, figured Ban- croft (1949, pl. 1, fig. 4) from the Gasworks Mudstone (Lower Llandovery), cutting opposite entrance to gasworks, Haverfordwest, Pembrokeshire. Turnbull Collection. DIMENSIONS (in cm.—all specimens from type locality) Il. Ww. -62 approx. 3:7 46 approx. 3°5 SMA 32194 Lectotype, pedicle valve SMA 32193 Pedicle valve BB 31435 Pedicle valve 2 3°05 BB 31412 Brachial valve : 35 approx. 2°8 BB 31443 Brachial valve . 3 0-90 122 no Ww WN N Discussion. The second specimen figured by Bancroft has been chosen as lectotype because the first (1949, pl. 1, fig. 3) is the counterpart to the figured ex- ample of ‘ Strophomena’ agrestis from the Slade Beds (SMA 32040), and was pre- sumably illustrated as S. scotica in error. Bancroft also erected a variety, S. scotica var. alveata, without giving any differences from the nominal subspecies. As the localities are the same and the types of both subspecies virtually identical (refigured here Pl. 3, figs. 4-8) and within the range of variation found in the Gasworks Mud- stone, no subspecies of K. scotica seem necessary. Williams (1951 : 116) selected a specimen from the Gasworks Mudstone of the Frolic section as type for the species, but as this is not one of Bancroft’s originals the selection is not valid. Williams’ specimen (refigured here Pl. 3, fig. 9) is, how- ever, clearly conspecific with the type material from the entrance to the gasworks at Haverfordwest. Katastrophomena penkillensis (Reed) (Pl. 4, figs. 1-6) 21871. Strophomena antiquata (J. de C. Sowerby); Davidson pars pl. 44, fig. 5 only. 1917. Stvophonella penkillensis Reed : goo, pl. 18, figs. 11-14. Diacnosis. Katastrophomena with differentiated parvicostellate ornament. DeEscripTIon. Exterior. Gently resupinate. Ornament of fairly fine differen- tiated parvicostellae, the smaller type mere threads. New ribs arise by intercala- tion. Large ventral interarea, but smaller on brachial valve than other species of the genus. No information on extent of pseudodeltidium. Chilidium present. Occasional prominent growth lines sometimes seen on valve exterior. Pedicle interior. Straight hingeline with prominent teeth which form the posterior end of a pair of muscle bounding ridges of approximately diamond shape, although they do not meet anteriorly. Median septum running from the apex to a position level with, or just anterior to, the ends of the muscle bounding ridges. On either side of the anterior end of the septum are a pair of bladelike adductor scars, which themselves may run anterior to the end of the bounding ridges. Diductor scars strongly impressed, sometimes with radiating striae and concentric growth ridges. Shell of variable thickness with large postero-median taleolae not developed. 298 BRITISH LOWER SILURIAN Brachial interior. Fairly straight socket plates widely divergent. Normal erect bilobed cardinal process. Variably developed muscle field structures; trans-muscle septa sometimes seen (Pl. 4, fig. 3, but not in Pl. 4, fig. 1). Broad, faint platform between two more or less circular muscle scars which are weakly impressed. LEcTOTYPE (here selected) B 73013, a brachial internal mould, figured by Reed (1917, pl. 18, fig. rr) from the Upper Llandovery of Bargany Pond Burn, Girvan, Ayrshire, Scotland. Gray Collection. DIMENSIONS (in cm.—all specimens from Bargany Pond Burn) ie Ww. B 73013 Lectotype, brachial valve . H+57 Ze gA BB 31432 Brachial valve . ; : Ty approx. 2°3 BB 31472 Pedicle valve : E } I+ 40 2:86 Discussion. Despite the localities being given by Reed as (1) Penkill (2) Bargany Pond Burn, all his figured specimens come from Bargany Pond Burn, where the species is, however, rare. Reed put the species into Strophonella as he described the hingeline as ‘ finely crenulated’, but there is no doubt that the hingelines of the specimens to hand, which include all Reed’s syntypes, are smooth. It is surprising that Reed made this mistake, especially as Davidson had already labelled some of the specimens as S. antiquata (fide Reed 1917 : gor, no Davidson label is with the type lot today). Katastrophomena penkillensis also occurs rarely in the higher Llandovery horizons in Shropshire, for example a pedicle valve (BB 31408) from the Minsterley Formation (pl. 4, fig. 6) and a brachial valve from the Purple Shale of the Onny River, GSM 11693. Thus so far the species seems confined to the top half of the Upper Llandovery, and to judge both from their ornament and general aspect, it is probable that the Wenlock species of the genus were derived direct from some earlier form such as K. woodlandensis rather than from K. penkillensis, despite its wide geographical range. Katastrophomena sp. (Pl. 4, figs. 7, 8) In the material from Shropshire there are, in addition to the specimens of K. penkillensis from the upper beds, two brachiopods referable to Katastrophomena from the lower horizons in the northern Longmynd-Shelve outcrop. These consist of a pedicle valve from the Venusbank Formation of The Corners, near Betton (Grid Ref. SJ/314 025] and a brachial valve from the Bog Quartzite of Bog Mine [Grid Ref. SO/3510 9815]. The latter is poorly preserved (BB 31451, Pl. 4, fig. 7), but clearly shows the furcitellinid bifurcation of the median septum. The pedicle valve (BB 31407, Pl. 4, fig. 8) is a large specimen for the genus and has a more angularly pentagonal muscle field than the contemporary KX. woodlandensis geniculata, perhaps more similar to some specimens of Kx. scotica from the Lower Llandovery ; STROPHOMENACEAN BRACHIOPODS 299 however the short median ridge does not extend anteriorly of the muscle bounding ridges as in the latter species. There is no doubt as to the generic identity of these Shropshire specimens, and thus they are provisionally described here until more material comes to light. Both specimens show marked differences from the named species of Katastrophomena. It is noteworthy that no material ascribable to this genus has so far come to light in any part of the southern Welsh Borderland. Subfamily LEPTAENINAE Hall & Clarke, 1894 The relationships and status of the leptaenids have been discussed above under the heading of the superfamily. Three genera attributable to the subfamily have been found in the British Lower Silurian, Leptaena, Cyphomena and Mackerrovia gen. nov. A fourth genus, Bellimurina, is represented by a single specimen. It is possible that some species here treated as Leptaena might be put into such later genera as Bracteoleptaena Havlicek 1963 from the Bohemian Wenlock, but in the Llandovery the variation is not enough to separate such species from Leptaena itself. Genus LEPTAENA Dalman, 1828 Type species. L. rugosa Dalman 1828 from the Upper Ordovician Dalmanitina Beds of Fa dalaberg, Vastergotland, Sweden. A lectotype was selected and the species figured by Spjeldnaes (1957, p. 173, pl. 7, figs. 1, 2, 4), and also by Williams (1965, fig. 252, figs. 5a, 5b). The species problem in Leptaena seems more acute than in most other genera of brachiopods. After the mid-Ordovician radiation, the subfamily Leptaeninae grew smaller in terms of generic numbers, and thus by Llandovery times the genera were reduced to approximately five, and all save Leptaena itself are rare and sporadic. On the other hand there is some variation in the form of Leptaena between nearly every locality in which one finds it. This bears out the assertion of Imbrie (1956, p. 219): ‘ Study of living populations has shown that if sufficiently rigorous methods are employed, significant morphological and genetic differences between two popu- lations can be demonstrated. Hence species and subspecies must be considered as collective categories, in the sense that they are composed of local populations no two of which are identical.’ Thus a very large number of specific or subspecific names could have been erected in the present work, but these would have served only as a smokescreen to hide the basic truth of the ‘ Leptaena rhomboidalis’ concept. Here was a successful stock, essentially unchanged from the Ordovician to the Carboniferous, which remained firmly established in an apparent variety of ecological niches. However there are some differences upon which species have already been erected, and in many of these cases the differences do persist in many populations from many localities. Thus their taxonomic expression is a positive step towards their recognition and understanding. GEOL. 15, 6. 31 300 BRITISH LOWER SILURIAN Havlicek (1968) has referred several Silurian species to Leptagonia on the grounds that their morphogeny has proceeded nearer that genus than to typical Leptaena. In this paper all the Silurian forms are retained in Leftaena until the Devonian and Carboniferous stocks become better known. There now follows a list of previously erected species of Leptaena of Ashgill, Llandovery and Wenlock age, followed by a list of species previously referred to the genus, but which are here considered distinct from it. Ashgill and Silurian species assigned. Leptaena rugosa Dalman 1828 : 106, pl. I, fig. 1. Dalmanitina Beds (Ashgill) of Vastergotland, Sweden. Anomites rhomboidalis Wahlenberg 1821 : 65. ?Wenlock of North German drift. Producta depressa J. de C. Sowerby 1823 : 86, pl. 459, fig. 3. Wenlock Limestone of Dudley. Leptaena tenuistriata J. de C. Sowerby im Murchison 1830 : 636, pl. 22, fig. 2. Wenlock of Marloes Bay, Pembrokeshire. Leptaena depressa var. vulgaris Barrande 1848 : 84, pl. 22, figs. 6, 7. Wenlock/ Ludlow of Bohemia, Czechoslovakia. L. quadrilatera Shaler 1865 : 65. Ellis Bay Formation, Anticosti Island, Canada. L. schmidti Gagel 1890 : 50, pl. 5, fig. 28. Lyckholm Fm (Upper Ordovician) East Baltic. L. richmondensis Foerste 1909 : 211, pl. 4, fig. 10. Richmond Group, Ohio, U.S.A. L. richmondensis var. precursor Foerste 1909 : 211, pl. 4, fig. 11. Richmond Group, Ohio, U.S.A. L. rhomboidalis ‘ var. B’ Reed 1917 : 872, pl. 13, fig. 1. Whitehouse Group, Girvan, Ayrshire. L. rhomboidalis ‘var. y’ Reed 1917 : 872, pl. 13, figs. 2, 3. Drummuck Group, Girvan, Ayrshire. L. rhomboidalis ‘ var. 6’ Reed 1917 : 872, pl. 13, fig. 4. Mulloch Hill Sandstone (Lower Llandovery), Girvan, Ayrshire. (Here described as L. valentia mullochensis.) L. rhomboidalis ‘ var. €’ Reed 1917 : 872, pl. 13, figs. 5, 6, non fig. 7. Woodland Point (Middle Llandovery), Girvan, Ayrshire. (Here described as L. valentia sp. nov.) L. rhomboidalis var. nana Chernychev 1937 : 67, pl. 2, figs. 16-18. Wenlock of Mongolia. L. zeta Lamont 1947 : 200. Penkill Group (Upper Llandovery), Girvan, Ayrshire. L. haverfordensis (and var. contracta) Bancroft 1949 : 6, pl. I, figs. 18-24. Gas- works Mudstone (Lower Llandovery), Haverfordwest, Pembrokeshire. L. valida Bancroft 1949 : 6, pl. 1, fig. 25. Upper Llandovery (C,), Llandovery, Carmarthenshire. L. urbana Bancroft 1949 : 6, pl. 2, figs. 1, 2. Upper Llandovery (C,), Llandovery, Carmarthenshire. L. elongata Bancroft 1949 : 7, pl. 1, figs. 26, 27. Upper Llandovery (C,), Llan- dovery, Carmarthenshire. L. quadrata Bancroft 1949 : 7, pl. 1, figs. 28-30. Upper Llandovery, The Frolic, Haverfordwest, Pembrokeshire. STROPHOMENACEAN BRACHIOPODS 301 L. ? tennesseensis Amsden 1949 : 54, pl. 5, figs. 11-15. Brownsport Formation (Wenlock/Ludlow), U.S.A. L. delicata Amsden 1949 : 55, pl. 5, figs. 11-15. Brownsport Formation (Wenlock/ Ludlow), U.S.A. L. oklahomensis Amsden 1951 : 85, pl. 16, figs. 29-35. Henryhouse Formation (Wenlock/Ludlow), U.S.A. L. acuteplicata Sokolskaya 1954: 60, pl. 4, figs. 1-4. Porkuni Stage (Upper Llandovery), Estonia, U.S.S.R. ? Productus twamleyir Davidson 1848 : 315, pl. 3, fig. 1. Wenlock Limestone, Dudley, Worcestershire. [The original specimen is not now to be found, but David- son (1871 : 282) later put the species into synonymy with L. rhomboidalis. | Species excluded from Leptaena Leptaena sinuosus and L. parvula Kindle 1915. See Pentlandina. L. wisgoriensis Lamont & Gilbert 1945. See Cyphomena. L. centervillensis Foerste 1923. Brassfield Limestone, Ohio. L. julia (Billings 1862). See Cyphomena. L. loveni de Verneuil 1848. See Pentlandina. L. bella Williams 1951 : 119, pl. 7, figs. 14, 15. Middle Llandovery, Llandovery. Probably an undescribed genus, but the small amount of material at present avail- able does not warrant redescription. Three groups within Leptaena are recognizable in the British Llandovery. (a) Large species with more or less oval-sided pedicle muscle scars. (b) Large species with more or less parallel-sided pedicle muscle scars. (c) Small species, which as at present known are a rather less well-knit group than either of the other two, and which will probably be found to be an amal- gam of further groups when more material becomes available. In the Lower and Middle Llandovery the first two groups of species seem to have been confined to the Scottish area and the Anglo-Welsh area respectively, and this remains substantially true for the Upper Llandovery, but in late Upper Llandovery time there was some admixture of the two groups; thus rare L. zeta occurs in the Purple Shale of Shropshire, and the leptaenid found in Deerhope Burn has the oval muscle-scar outline. The first two groups could thus have shared a mutual ecological niche, as they have not so far been found occurring together. On the other hand, representatives of the third group, the small species, do sometimes occur with members of one or other of the larger groups, examples of this being at Woodland Point, Girvan, where L. valentia and L. reedi occur side by side in apparent harmony, and at locality H-G-A in the Malverns where L. contermina and L. zieglert also occur together. Thus at least two separate ecological niches may be inferred for species of Leptaena in level bottom communities at this time, although for the most part only one or other of them was occupied, and the genus is absent from many localities. Whether this scheme holds good for other parts of the world during the Lower Silurian has not yet been established. The only foreign species of Leptaena so far 302 BRIELLE WO We Re Ser WRT AWN: described from beds of Llandovery age, L. acuteplicata Sokolskaya 1954 from Estonia, has not yet been illustrated with interior views, so that its relationship with British species remains unknown. Some consideration has been given to the possibility of formal subgeneric recog- nition of the three groups, but this has been withheld as taxonomic splitting of this kind does not seem justified in a generic group which remains extremely well-knit, and whose phylogeny is at the moment not completely understood, although some relationships are clear. Another possibility would be to have one species name for each of the groups, with various subspecies, but this would unite the various small forms of the third group under one specific name, which would certainly obscure the true situation, in which most of them are definitely more than subspecifically separable. The British Llandovery species will now be described in the three groups as follows: (a) L. martinensis sp. nov., L. haverfordensis Bancroft 1949, L. valida Bancroft 1949, L. urbana Bancroft 1949, L. contermina sp. nov. (b) L. valentia sp. nov., L. valentia mullochensis subsp. nov., L. zeta Lamont 1947. (c) L. veedi sp. nov., L. ziegleri sp. nov., L. quadrata Bancroft 1949, L. purpurea sp. nov. Their possible phylogeny is shown in Text-fig. 1. Upper Llandovery L. zeta C4 -6 L. purpurea L. ziegleri L. urbana | L. quadrata Upper Llandovery Cy _3 L.contermina Y L. valida | ! Middle Llandovery L. valentia L.reedi L, haverfordensis Lower Llandovery | L. valentia L. martinensis mullochensis FiG. 1. Leptaena martinensis sp. nov. (Pl. 4, figs. 9-13, Pl. 5, figs. 1-3) 21949. Leptaena martini Bancroft : 6, non. pl. 1, fig. 18 nomen nudwn. Diacnosis. Leptaena with strong rugae and well defined ornament. Poorly developed muscle bounding ridges of variable shape. DESCRIPTION. Exterior. Shape semicircular to quadrate with alae. Genicu- lation between 70 and go degrees. Ornament of well-defined, subequal parvicos- STROPHOMENACEAN BRACHIOPODS 303 tellae. Rugae strong with a particularly large ruga at the knee. Small interarea with delthyrium mainly closed by a small chilidium. No information on the foramen, but probably small. Pedicle interior. Widely divergent teeth with fairly prominent thin dental plates. Muscle bounding ridges are poorly developed for the genus and of variable shape, sometimes oval, sometimes angular; they do not meet anteriorly. No information on the shape of the adductor scars which are not impressed at all on the material to hand. No median septum. Central talaeolae, though not large, are more prominent than on the trail. Brachial interior. Large divergent cardinal process lobes, mounted on a platform. The postero-lateral parts of the latter serve as the anterior ends of the sockets. The platform is trilobed anteriorly, partly enclosed subcircular adductor muscle scars. Median septum usually absent, but in a few specimens a very faint ridge may be seen about halfway to the edge of the disc. Occasional prominent pseudo- punctae in the central region outside the muscle field. HoLotypPe. SMA 31865 a pedicle valve (both interior and exterior are preserved) from Cartlett Beds (Lower Llandovery), St. Martin’s Cemetery, Haverfordwest, Pembroke. Turnbull Collection. DIMENSIONS (in cm.—all specimens from St. Martin’s Cemetery). Note that in all the following measurements of species of Leptaena the term 14 signifies the distance from the umbo to the knee measured along the median plane; as the trail of the various species differs so much, both in form and angle with the disc, a normal measurement of length is meaningless for comparative purposes. la W. SMA 31865 Holotype pedicle valve : I-50 approx. 3:2 SMA 31859 Paratype pedicle valve ‘ 0:62 1°22 SMA 31860 Paratype pedicle valve : 0:97 2°04 SMA 31864 Paratype brachial valve. 1:68 approx. 3°3 SMA 31861 Paratype brachial valve. 0°53 approx. 0-9 Discussion. In his paper, Bancroft (1949 : 6) erected ‘ Leptaena martini sp. nov.’ giving St. Martin’s Cemetery as the type locality, but referring the reader to his pl. r, figs. 18, 23. These two figures are, in fact, of L. haverfordensis from the Gasworks Mudstone of the gasworks, Haverfordwest (SMA 32161 and 40512). Thus the species is without illustration, or reference to a previous illustration, and thus a nomen nudum, according to the rules of nomenclature. Bancroft mentions two species present at the St. Martin’s Cemetery, a large one and a small one, but this is not borne out by the material in the Turnbull Collection or in subsequent collections made by the author. Possibly Bancroft was misled by the small individuals present in the Turnbull Collection, but these are all immature as shown by the lack of geniculation (pl. 5, figs. I-3). The Cartlett Mudstones are the oldest representatives of the Silurian in South Wales, and indeed almost certainly span the Ordovician-Silurian boundary, as the 304 BRITISH LOWER SILURIAN writer has found Tvetaspis at their base (kindly confirmed by Dr. W. T. Dean) in a temporary (1965) exposure in the foundations for a housing estate behind St. Martin’s Cemetery itself. L. martinensis is probably an ancestor of L. haverfordensis, but differs from it in the more prominent ornament and rugae, and in the more variably shaped and less developed pedicle valve muscle bounding ridges. Leptaena haverfordensis Bancroft (Pl. 5, figs. 4-15) 1949. Leptaena haverfoydensis Bancroft : 6, pl. 1, figs. 19-20, 23, 24. 1949. Leptaena haverfordensis var. contyacta Bancroft : 6, pl. 1, figs. 18, 21-22. DiaGnosis. Large Leptaena with oval-sided pedicle valve muscle area. Socket plates variably present. DEscRIPTION. Exterior. Shape semicircular with alae. Angle of geniculation between 75 and go degrees. Ornament of numerous fine but well-pronounced, sub-equal parvicostellae. Well-developed regular rugae, of relatively small wave length for the genus (observed range on the pedicle valve = 10-15 in adult speci- mens). At the knee there is always a prominent ruga and just posterior to this an unusually pronounced trough. One or two rugae sometimes seen on the upper half of the trail. Medium-sized interarea; no information on foramen, but probably small. Pedicle interior. Prominent teeth and dental plates merging with muscle bounding ridges of oval shape; these flare outwards from the valve floor and sometimes meet anteriorly, and sometimes are open. Prominent pair of lanceolate adductor scars between the diductor scars which often have prominent radiating striae across them. Median septum not developed except as a ridge dividing the muscles. Prominent taleolae sometimes developed centrally outside the muscle field. Brachial interior. Prominent erect slightly divergent cardinal process lobes between widely divergent socket plates. Irregular platform developed often tri- lobed anteriorly to enclose the pair of suboral adductor scars. The central lobe extends further anteriorly to form a very thin, usually faint, median septum. Pro- minent taleolae on the disc outside the muscle field. LECTOTYPE, here designated. SMA 32163 a pedical valve (figured Bancroft 1949, pl. 1, fig. 20) from the Gasworks Mudstone (Lower Llandovery) opposite entrance to the gasworks, Haverfordwest, Pembrokeshire. DIMENSIONS (in cm.) ihe W. SMA 32163 Lectotype, pedicle valve Dovart approx. 3°5 BB 31355 __—~Pedical valve 1-60 2-96 BB 31326 Pedicle valve +54 3°45 BB 31363 Brachial valve . 1°63 approx. 2:6 BB 31341 Brachial valve . 1°84 approx. 3°4 STROPHOMENACEAN BRACHIOPODS 305 Discussion. Bancroft erected L. haverfordensis var. contracta from the same locality, based on a single specimen (SMA 40512) which is refigured here (PI. 5, fig. 14). From large collections made from the Gasworks Mudstone, it is clear that there are all intergrades between this specimen, with its well impressed musculature and vascular system, and the typical form, so that no sub-species seems warranted. The species occurs in the Lower Llandovery of Pembrokeshire and also in the type area of Llandovery, but has not yet been discovered elsewhere, which is not very surprising as these two areas represent the most fossiliferous Lower Llandovery in the Welsh area. In Girvan, the same ecological niche was occupied at this time by Leptaena valentia mullochensis subsp. nov. Leptaena valida Bancroft (Pl. 6, figs. 1-5) 1949. Leptaena valida Bancroft : 6, pl. 1, fig. 25. 1949. Leptaena elongata Bancroft : 7 pl. 1, figs. 26, 27. DiaGnosis. Large Leftaena with oval-sided pedicle muscle field which may be bilobed anteriorly. A few larger parvicostellae antero-medianly. LectotyPE, here selected. SMA 35690, a pedicle valve, external and internal mould (figured by Bancroft 1949, pl. 1, fig. 25) from C, beds (Upper Llandovery), O. T. Jones collection, his locality 26 SE/E Ar13, River Sefin, 400 yards south-east of Llety’r-hyddod, Llandovery, Carmarthenshire. DIMENSIONS (in cm.) la w. SMA 35690 Lectotype, pedicle valve. 20 approx. 4°3 SMA 35691 Pedicle valve . . ‘ 1°83 _— Discussion. The specimen of Leptaena valida, one pedicle valve, and the speci- mens of L. elongata, two pedicle valves, both come from the same locality, i.e. the C, shales full of Stvicklandia lens progressa by the side of the River Sefin, Llandovery. All are clearly the same species, but the lectotype has been preserved with its disc oblique to the bedding plane, and has thus been distorted to give a greater apparent width than the other two specimens. Subsequent collecting at the locality has resulted in another crushed pedicle valve, but the brachial valve is still unknown. The species is striking in that several parvicostellae are distinctly larger than the rest in the antero-median region of the valve, giving an impression of differentia- tion over this small area only. Leptaena urbana Bancroft (Pl. 6, figs. 6, 7) 1949. Leptaena urbana Bancroft : 6, pl. 2, figs. 1, 2. LectotyPE, here selected. SMA 35693 a pedicle internal mould, (figured Ban- croft 1949 pl. 2, fig. 1) from C, Beds (Upper Llandovery), O. T. Jones collection, 306 BRT Se OWE Ra Sree) Onkole AGN his locality 27 NW/E A8, quarry 500 yards north-east of Cefn Cerig, Llandovery, Carmarthenshire. DIMENSIONS (in cm.) la Ww. SMA 35693 Lectotype, pedicle valve. approx. 2°5 approx. 4:2 SMA 35694 Brachial valve . : : 2°25 approx. 4°5 Discussion. The two specimens figured by Bancroft are the only representatives of the species in the Sedgwick Museum and further collecting from the type locality has not produced more material. The species is distinct in its pedicle muscle field shape and size and in the weak- ness and irregularity of its rugae. It thus appears to have a valid specific concept, but in the absence of more material, further consideration to it will not be given here. Leptaena contermina sp. nov. (Pl. 6, figs. 8-13, Pl. 7, figs. 1-11) 1871. Strophomena rhomboidalis (Wilckens); Davidson, pl. 39, fig. 17 only. DiaGnosis. Transverse Leftaena with interior encircling ridges in both valves, and regular rugae. DEscrRIPTION. Exterior. Mucronate and sharply geniculate. Apart from the large ears, the shell shape is approximately semicircular, although rather transverse. Equally parvicostellate ornament, with ribs increasing slightly in size anteriorly. Occasionally new ribs arise either by intercalation or more commonly by bifurcating (OUM Cg153 shows both methods on a single brachial valve, an external mould). Rugae regular and continuous. The number of rugae on the disc varies between six and ten within a population. The geniculation occurs at different lengths within a population, but usually between I-0 and 1-4 cm. The angle between the disc and trail is between 75 and go degrees. Open delthyrium, prominent chilidium. The pedicle foramen has not been observed on any specimen. Pedicle interior. Teeth and dental plates small for the genus and fused to a small anterior extension of the hingeline. Large, prominent and evenly curving muscle boundary ridges, nearly meeting anteriorly and fusing posteriorly with an extension of the dental plates. A small median ridge divides the lanceolate adductor scars, which are usually very poorly impressed. In some specimens, the diductors com- pletely enclose the adductors, in others they just fail to do so. Striae are developed on the muscle field, particularly on the diductors. The more coarsely pustulate disc and some of the trail are bounded by a nearly semicircular ridge which runs round the trail anteriorly but laterally crosses the geniculation and merges posteriorly with the hingeline at a low angle near the dental plates. The internal reflection of the ornament is much stronger outside this ridge. Coarse pseudopunctae postero- medianly, except on the muscle field, but not so prominent as in the brachial valve. Brachial interior. Cardinal process lobes prominent, between them a much smaller narrow blade-like process. Socket plates variably developed and widely divergent, with rarely-preserved striae on their anterior side. Running anteriorly and laterally is a three pronged platform which bounds the posterior edge of the STROPHOMENACEAN BRACHIOPODS 307 adductor scars, and the middle prong of which divides them, forming a short, broad median ridge. This line is marked discontinuously anteriorly as a fine ridge until near the edge of the disc, and in many specimens is more pronounced near its anterior end. As with the ventral valve a ridge runs laterally from the hingeline posterior of the sockets to the edge of the disc, but instead of crossing the geniculation as with the pedicle valve, it stays on its edge, thus making a wall on the anterior edge of the brachial valve which is not reflected on the exterior. Except in the muscle field, there are prominent pseudopunctae which are random posteriorly, but anteriorly are arranged in lines parallel to the external ornament. They are smaller and less well defined outside the encircling ridge. HoLotyPe. OUM Cor168 a pedicle valve from the Venusbank Formation (Middle Llandovery), Hope Quarry, Shropshire. Grid Ref. SJ/3551 0208. Author’s col- lection. DIMENSIONS (in cm.) la w. OUM Co168 Holotype, pedicle valve Hope Quarry aT 2°24 OUM Co155_ Paratype, brachial valve Hope Quarry iKop mE — OUM Cro50r Paratype, brachial valve Bog Mine Teel 2°90 BB 31280 Paratype, pedicle valve Bog Mine 1°34 2:81 BB 31289 Paratype, pedicle valve Bog Mine I+ 24 2:46 Discussion. There is no mistaking this species from any yet described. It is much more transverse than most species of Leptaena, and the rugosity is much more regular than average, yet not obscuring the ornament. As may be seen from the illustrations, there is some variation of the muscle pattern and relative dimen- sions, but the species is extremely homogeneous between the various localities. Its nearest probable relative is L. haverfordensis from the Gasworks Mudstone, which it resembles in the general configuration of the muscle pattern (except in the strength of the adductor scars), but it does not have the raised rim to the disc of that species, nor is the rugae pattern the same. From L. valida and L. quadrata and L. urbana, all from the Upper Llandovery, it differs in diductor muscle con- figuration, rugae pattern, and also in ornament, the first two species having more prominant costellae near the median plane, and the third being almost without ornament. From the later, Wenlock, species it differs in the relative shortness and regularity of its trail, the presence of the ventral encircling ridge, and the less massive teeth and chilidium. In Shropshire the species is confined to the Bog Quartzite and Venusbank Forma- tion. It also occurs in the Cowleigh Park Beds of the Malverns, the Wych Beds of the Malverns and the Yartleton Beds of May Hill, the last two occurrences being substantially the younger. Leptaena valentia sp. nov. (Pl. 8, figs. 1-8) 1917. Leptaena rhomboidalis (Wilckens) var. ¢ Reed : 872, pl. 13, figs. 5, 6 non fig. 7. Diacnosis. Large Leptaena with sub-parallel muscle bounding ridges. 308 BRITISH LOWER SILURIAN DEscRIPTION. Exterior. Shape semicircular with more or less prominent alae. Geniculation between 70 and go degrees. Ornament of subequal parvicostellae, which arise by bifurcation or intercalation. Rugae fairly regular, with a particularly large ruga developed at the knee. Medium-sized interarea with prominent growth lines. Delthyrium almost entirely closed by the large chilidium, but there is a very small pseudodeltidium at the delthyrial apex. Foramen not seen, but probably small and closed. Pedicle interior. Fairly small grooved teeth and dental plates for the genus, the latter joined to a pair of strong muscle bounding ridges which flare outwards from the valve floor. The form of the bounding ridges is variable, but they usually diverge widely posteriorly with the socket plates, then change direction sharply by up to 45 degrees becoming subparallel, continuing anteriorly until they merge with the valve floor from between half and two-thirds way to the knee. The two bounding ridges never meet. Very small median ridge on either side of which are the poorly impressed lanceolate adductor scars. The diductor muscle scars are strongly im- pressed within the bounding ridges and often have striae impressed upon them. Coarsely pustulate in the central region of the valve, outside the muscle area. Brachial interior. Prominent, erect, bilobed cardinal process, the two lobes diverging slightly laterally. Immediately anterior to these is a prominent platform consisting of a pad of secondary calcite. The posterior edge of the pad on either side of the cardinal process forms the anterior edge of the sockets and has grooves to fit the teeth. The anterior edge of the pad is trilobed, forming half or more of the boundary of the roughly circular adductor muscle scars. The adductor scar area has various secondary ridges, but they are never so well developed as to form trans-muscle septa. Completely anterior of the muscle field there is usually a very fine short median septum. As with the pedicle valve the anterior is very coarsely pustulate, the individual taleolae standing up to 0:5 mm. above the valve floor. HoLotyrPe. B 73340 a complete shell with both valves (figured Reed 1917, pl. 13, fig. 5) from the Middle Llandovery of Woodland Point, Girvan, Ayrshire, Scotland. Gray Collection. DIMENSIONS (in cm.—all specimens from Woodland Point) la Ww. B 73340 Holotype, pedicle valve measured 1932 approx. 3:6 BB 55621 Paratype, pedicle valve E35 2 AQZ, BB 55637 Paratype, pedicle valve : 23) 2°74 BB 55653 Paratype, pedicle valve 0-98 Py; BB 55705 Paratype, brachial valve 1-18 2°37 BB 55706 Paratype, brachial valve : 1°25 3:60 Discussion. This species is common at the type locality, and seems to have been one of the more successful leptaenids in the Llandovery. It is clearly a direct descendant of its subspecies L. valentia mullochensts, described below, which inhabited the same area in the lower Llandovery. Woodland Point is also of interest in that it is one of the localities where both large and small species of Leptaena are found side by side, in this case L. valentia and L. reed. STROPHOMENACEAN BRACHIOPODS 309 Leptaena valentia mullochensis subsp. nov. (Pl. 8, figs. 9-15) 1917. Leptaena rhomboidalis (Wilckens) var. 6 Reed : 872, pl. 13, fig. 4. HoLotyPe. B 73384, a partly exfoliated pedicle valve figured by Reed (1917, pl. 13, fig. 4) from Lower Llandovery beds, Mulloch Hill, Girvan, Ayrshire, Scotland. Gray Collection. DIMENSIONS (in cm.) la Ww. B 73384 Holotype, pedicle valve I*44 approx. 3:2 BB 31375 Paratype, pedicle valve ao 3°34 BB 73379 Paratype, pedicle valve : 0°95 I-Q2 BB 31386 Paratype, brachial valve : 1-28 2°26 BB 31388 Paratype, brachial valve : 120) 1°94 Discussion. This form seems best considered as a subspecies of L. valentia as the two are very close in most morphological details, particularly in the internal structures within both valves. There are, however, various minor differences which enables Reed’s separation to be confirmed. Rugae counts on pedicle internal moulds give the following results (number of rugae visible up to geniculation). Rugae Number Woodland Point Mulloch Hill 4 2 0) 5 18 3 6 15 8 7 2 5 8 0) 2 i = 37) i, == Ite) Reed (1917 : 872) noted differences between the two ‘ varieties’ of the angle at which the rugae meet the hingeline, but this is not supported by the present inves- tigation. The rugae are however, less regular in L. valentia mullochensis than in, the typical subspecies, often being interrupted, particularly laterally. The pedicle valve length of disc/width ratios of the two subspecies are virtually the same, having a mean of 42:8° for Mulloch Hill (n = 21, OR 31-3-57-4) and 41:9% for Woodland Point (n = 53, OR 29:0-52:8). The variability of the pedicle valve muscle field for the whole species is demonstrated by PI. 8, figs. ro, 23, 14. Leptaena zeta Lamont (Pl. 9, figs. 1-6) 1871. Strophomena rhomboidalis (Wilckens); Davidson : 281 pars, pl. 39, fig. 20 only. 1917. Leptaena rhomboidalis (Wilckens) var. € Reed : 872, pl. 13, figs. 8, 9. 1947. Leptaena zeta Lamont : 200. Diacnosis. Very large Leptaena with mainly parallel-sided muscle area. DESCRIPTION. Exterior. Shape semicircular with variably pronounced alae. Geniculation between 70 and go degrees, and trail proportionately shorter than is 310 BRITISH LOWER SILURIAN usual for the genus. Ornament of subequal parvicostellae and rugae which are usually continuous but are often irregular. Medium-sized interarea with prominent growth lines. Delthyrium mainly closed by large chilidium which appears bilobed as it wraps round the cardinal process lobes. Small foramen plugged by adventi- tious material. Pedicle interior. Strong grooved teeth and widely divergent small dental plates, the latter joined to a pair of muscle bounding ridges which flare outward from the valve floor. The ridges are usually subparallel but occasionally curve inwards anteriorly, though never meeting and usually completely open (Pl. 9, figs. 2, 3). Very small median ridge sometimes developed in the muscle area between the small lanceolate adductor scars, themselves inside the strongly impressed diductor scars which often have radiating striae across them. The central area outside the muscle field is coarsely pustulate. Brachial interior. Strong erect cardinal process lobes very close to the chilidium with faint blade between them. The lobes rest on the posterior end of a strong platform pad, which is often grooved postero-laterally to act as a socket plate. The platform anterior edge is trilobed, surrounding on three sides the pair of promin- ent subcircular adductor scars. A faint extension of the central platform sometimes extends further anteriorly to become a very small median septum. The central area which merges laterally with the platform is coarsely pustulate. LEcToTyPE, here designated. B 73355 (the original of Reed 1917, pl. 13, fig. 8), a pedicle exterior from Penkill, Girvan. Gray Collection. DIMENSIONS (in cm.) ihe w. B 73355 Lectotype, pedicle valve Penkill TOY, approx. 4°4 BB 31305 Pedicle valve Penkill 2°29 approx. 4°7 B 73364 Pedicle valve Bargany Pond Burn 2:38 approx. 5:8 B 73365 Pedicle valve Bargany Pond Burn 2-10 approx. 5:2 BB 31469 Pedicle valve Minsterley Lane approx. 2-3 6:58 BB 31468 Brachial valve Muinsterley Lane 2°05 3°42 Discussion. This is the largest species of Leptaena found in the British Llan- dovery (though not the largest in the Silurian—this is probably the undescribed species in the Woolhope limestone). It seems confined to the highest beds at Girvan—the Penkill group, and also to the Minsterley Formation of Shropshire. It is not common at any locality. From the general aspect, particularly the shape of the pedicle and brachial muscle field, it is probably a descendant of Leptaena valentia sp. nov. also from the Girvan area. Leptaena reedi sp. nov. (Pl. ro, figs. 1-14) 1917. Leptaena rhomboidalis (Wilckens) var. e (young shell) Reed : 872, pl. 13, fig. 7. Dracnosis. Small Leptaena, transverse, thick shelled, with large area and pseudodeltidium. STROPHOMENACEAN BRACHIOPODS 311 DeEscripTiIon. Exterior. Shape transverse with large alae, sometimes quadrate anteriorly. Geniculation often more than go degrees with the trail sometimes bending back under the disc. Ornament of subequal parvicostellae, coarser on the disc than on the trail. Symmetrical rugae on the disc, but no trace on the trail. Large interarea, particularly in the pedicle valve. Delthyrium closed partly by pseudodeltidium, partly by chilidium. Small supra-apical foramen plugged in most specimens. Pedicle interior. Strong grooved teeth attached to a pair of distinct bilobed muscle bounding ridges which sometimes meet anteriorly, but which are sometimes divided by a small median septum. Diamond shaped adductor scars on a ridge raised between the triangular diductor scars, which are sometimes grooved. Coarse taleolae on the disc outside the muscle field. Thick shell. Brachial interior. Erect, posteriorly directed bilobed cardinal process. Raised platform with variably developed trans-muscle septa. Short median septum some- times developed but often absent in the muscle field. Interior reflection of rugae but not ornament. Sharp geniculation usually present, inside which is a well developed taleolae field. HorotyPe. B 73341, a complete shell (figured by Reed 1917, pl. 13, fig. 7) from Woodland Point, Girvan, Ayrshire. Gray Collection. DIMENSIONS (in cm.) la w. B 73341 Holotype, pedicle valve : 0°51 approx. I°5 BB 31457 Paratype, pedicle valve : 0°75 1°72 BB 31461 Paratype, brachial valve : 0:68 1°81 B 73342 Paratype, brachial valve : 0-66 TEOR Ys) Discussion. Reed mistook this species for the young of L. valentia and they occur mixed intimately (e.g. Pl. ro, fig. 10) but the two are clearly distinct in nearly every feature. L. rveedi is rare at the type locality, although the Gray Collection contains about thirty specimens, and has not been found elsewhere than at Woodland Point. Its affinities are uncertain. No other species of Leptaena resembles it, and the large interarea is unique amongst Silurian strophomenids. The brachial muscle field is more reminiscent of Cyphomena or some of the strophomenids than of other species of Leptaena. Leptaena ziegleri sp. nov. (Pl. x1, figs. I-5) DiaGnosis. Small Leptaena with oval pedicle muscle field, and possessing strong socket plates. DEscripTION. Exterior. Shape semicircular, occasionally quadrate with small alae. Geniculation usually at right angles. Ornament of faint subequal parvi- costellae, rugae symmetrical and numerous but faint. Interarea small. Delthyrium probably mainly open, but no information on possible chilidium. Foramen not seen. 312 BRITISH LOWER SILURIAN Pedicle interior. Prominent teeth and dental plates joined to strong muscle bounding ridges. The latter are of oval, almost circular shape, but not quite meeting anteriorly. Adductor scars are not seen, diductor scars are poorly impressed within the muscle bounding ridges. Faint median septum in one specimen only (OUM C4147) otherwise absent. Brachial interior. Small, erect, bilobed cardinal process ankylosed to strong pair of socket plates. Brachial muscle field not impressed and details of muscalature not known. Very faint trace of median septum seen in some specimens only. Raised rim at edge of disc. HoLotyPe. OUM C4146, a pedicle valve internal mould from the Wych Beds (Upper Llandovery), Malvern Hills, Herefordshire. Grid Ref. SO/7612 3811. DIMENSIONS (in cm.) la w. OUM C4146 Holotype, pedicle valve. 0-64 1°05 OUM C4147 Paratype, pedicle valve. 0°54 1°25 OUM C4137 Paratype, brachial valve . 0:58 approx. 1:9 OUM C4136 Paratype, brachial valve . 0-64 approx. 1-4 Discussion. The species is known only from its type locality. It is distinctive in pedicle and brachial internal structures and in its shape and ornament. The species is named after Dr. A. M. Ziegler, who collected the material. Leptaena quadrata Bancroft (Pl. x1, figs. 6-r0) 1949. Leptaena quadvata (Reed MS) Bancroft 1949 : 7, pl. 1, figs. 28-30. DiacGnosis. Small quadrate Leptaena with many fine rugae. DeEscRIPTION. Exterior. Shape quadrate with small but pronounced alae. Small trail after geniculation of approximately 80 degrees. Ornament of fine symmetrical rugae and faint subequal parvicostellae. Interarea of average size. No information on possible pseudodeltidium; small chilidium present. Foramen not known, but probably small. Pedicle interior. Small divergent teeth joined to variably developed muscle bounding ridges. The latter are long and sub-parallel, sometimes merging anteriorly with the valve floor (Pl. 11, fig. 6), sometimes swinging round in an irregularly bilobed fashion (Pl. 11, fig. 10). A pair of elongate adductor scars between the impressed long diductor scars. Median septum absent. Brachial interior. Erect bilobed cardinal process. Weak platform posteriorly acting as socket plates, anteriorly enclosing weakly impressed adductor muscle field of approximately oval shape. Sometimes very thin median septum weakly de- veloped. LECTOTYPE, here selected. SMA 32437 a_ edicle valve internal and external mould (figured Bancroft 1949, pl. 1, fig. 28) from Uzmaston Beds (Upper Llandovery), STROPHOMENACEAN BRACHIOPODS 313 O. T. Jones Collection, ‘ locality K, below path south west of Uzmaston,’ The Frolic, near Haverfordwest, Pembrokeshire. DIMENSIONS (in cm.) la W. SMA 32437 Lectotype, pedicle valve. 0:73 0:86 SMA 32444 Pedicle valve . : f 0°55 0-86 SMA 32438 Brachial valve . : : 0-63 I*02 SMA 32441 Brachial valve . j 0°53 0:93 Discussion. This species is known only from its type locality where it occurs in a slightly crushed greenish siltstone. Its associates are Amp/luistophia whittardi Cocks, Pentlandina parva Bancroft, Dicoelosia cf. alticavatus (Whittard & Barker), Coolinia sp., Atrypa sp., Eospirifer sp. and Eoplectodonta millinensts (Jones), which indicate on balance a Cloyinda community, although no pentamerids have been seen. The usual leptaenid in the Welsh Borderland Clorvinda community is L. purpurea sp. nov., and Bancroft’s species may be related to it. L. purpurea has, however, a completely different muscle field disposition in both pedicle and brachial valves, and different overall proportions. It is also larger. Leptaena purpurea sp. nov. (Pl. 12, figs. 1-6) 1932. Leptaena sp. nov. Whittard, table facing p. 896. DiaGnosis. Small quadrate Leptaena with usually oval-sided pedicle muscle bounding ridges. DESCRIPTION. Exterior. Shape quadrate with small ears. Sharply geniculate with approximately a right angle between disc and trail, but the angle varies between obtuse and acute. Ornament of fine, subequal parvicostellae, with new costellae arising by intercalation. Rugae cover the whole disc on both valves; they are fairly regular and have a small wavelength. Small external rim on the ventral knee and a small groove on the dorsal knee. Open delthyrium, large chilidium, but rather smaller interarea than is common for the genus. No information on the pedicle foramen, except of a very young specimen (OUM C13141) in which it is supra-apical and probably, at that stage, functional. Pedicle interior. Straight hingeline with open delthyrium flanked by relatively large dental plates, considering the small size of the species which are combined in part with a raised posterior extension of the muscle bounding ridges. Faint muscle grooves often seen on the muscle field. Diductor scars bilobed and surrounded laterally by pronounced bounding ridges which in some specimens curve round anteriorly to form an w shape, although they do not quite meet in the centre. Small lanceolate adductor scars, though seldom seen, are separated by a fine median ridge which in a few specimens continues anteriorly of the muscle bounding ridges. In completely preserved specimens there is a ridge running about half-way down the trail and nearly all the way round it, but postero-laterally crossing the geniculation and merging at a low angle with the hingeline, although on many specimens the ridge is very faint. Pseudopunctae coarse near the umbo, except where absent in the 314 BRITISH LOWER SILURIAN muscle field. They are apparently randomly distributed near the umbo, but antero-laterally they tend to be arranged in lines parallel to both the rugae and the ornament. Brachial interior. Raised cardinal process with two stout lobes directed ventrally. Large chilidium fused close to the base of the cardinal process. Anchor shaped platform present, the haft of which forms a median ridge dividing the two pairs of oval adductor muscle scars, which are separated from each other by the pair of low short ridges running laterally from each side of the haft. Disc surrounded by raised rim, which is reflected to a lesser extent by the exterior groove, indicating a local thickening of the shell material. Mantle canals visible occasionally (Pl. 12, fig. 3) coming from the floor of the disc, up over the rim and fading towards the valve margin. No bifurcations seen. Pseudopunctae very noticeable postero- medianly, but scarcely visible on rim or trail. HoLotyPE. BB 31465, a pedicle internal mould from the Purple Shale (Upper Llandovery) of Domas, Shropshire. Grid Ref. SJ/5936 0062. DIMENSIONS (in cm.). la 2 BB 31465 Holotype, pedicle interior Domas 0°52 I-06 BB 31466 Paratype, brachial interior Hughley 0-51 T-1O OUM Cr2062 Paratype, pedicle interior Onny River 0°54 1-08 OUM C13480 Paratype, brachial exterior Domas 0°43 I-15 OUM C13478 Paratype, brachial exterior Domas 0°47 TAN OUM C13477 Paratype, brachial exterior Domas 0°45 I+20 OUM C13482 Paratype, pedicle interior Domas 0-41 0°79 OUM Cr3141 Paratype, brachial exterior Wall-under-Heywood 0-20 0:29 Discussion. Although leptaenids are to be found in nearly every collection from the Purple Shales, they are never common, but those that do occur are usually attributable to this form. The species is small, and thus only strictly comparable with L. quadrata Bancroft from the Upper Llandovery of the Frolic, Haverfordwest, from which it differs in its larger teeth, encircling muscle ridges and the character and strength of the rugae. One specimen of a leptaenid of comparable size, 1-35 cm. wide, has been collected (Bristol University Museum 12101) from the contemporary Damery Beds (C;) of Tortworth by Dr. M. L. K. Curtis. -The specimen, a pedicle valve (PI. 12, fig. 6), differs from L. purpurea in the indented shape of the muscle bounding ridges and also in the almost complete absence of internal ornament or rugae, but in general shape and size it is similar. Without further material, particularly brachial valves, any definite attribution seems unwarranted. Leptaena sp. (Bly 12, tisse 74 8) EXTERIOR DESCRIPTION. Shape quadrate and alate. Ornament of subequal, fine parvicostellae. Small rugae, uneven round the disc, but giving the illusion of not STROPHOMENACEAN BRACHIOPODS 315 being so. At least eighteen rugae_of subequal wavelength (except near the umbo) on the ventral disc and sixteen on the dorsal. Geniculation less than right angles on the ventral valve, but the trail curves into a steeper angle, meeting the anterior margin at an acute angle with the disc. Small external rim on the ventral knee, and small external groove on the dorsal knee. Prominent interarea. Open del- thyrium, large chilidium, with growth-lines persisting to the interarea. Small foramen about 0:2 mm. diameter. Locatity. Purple Shales, ‘near Harley’, Shropshire. DIMENSIONS. width = 3-6 cm. approx., length = 1-73 cm., length of disc = I:43 cm., height of trail = 1-2 cm. Discussion. In the late Professor Whittard’s collection there is one complete specimen (BB 31467) of Leptaena which cannot be assigned with confidence to any described species, but until interior details are known, to name a new species would be premature. Though too big for Leftaena purpurea it is sufficiently close to it for the possibility of a sport not to be ruled out completely, despite its large disc and overall size. Its shell thickness, interarea, and general proportions are much finer and more delicate than the Wenlock L. depressa. It may, however, be related to a large, undescribed species of Leptaena present in the Woolhope Limestone of Crickley Common, Herefordshire and elsewhere. Genus CYPHOMENA Cooper 1956 TYPE SPECIES. Leptaena homostriata Butts 1942 from the Oranda Formation (Middle Ordovician) of Virginia, North America. Discussion. When Cooper (1956 : 840) erected Cyphomena he put into it three species (and tentatively a fourth), all from the Middle Ordovician of North America. Subsequently Williams (1962 : 203) recognized one of them in the Scottish Caradocian. These are the only published records. The interior disposition and external form of the various species of Cyphomena, so well figured by Cooper, leave no doubt of the close relationship between them and some species present in the Llandovery. In particular the gradually curving pedicle valve and sharply geniculate brachial valve, the proportions and disposition of the musculature and denticulation in both valves, and the small curved pseudo- deltidium not completely filling the delthyrium, above which is developed a suffi- ciently large pedicle foramen for it to be considered functional, are identical in Ordovician and Silurian specimens. There is, however, one point of difference in that Cooper’s genus ‘ never developed the concentric wrinkling of the visceral region ’ (1956 : 841). It is true that complete rugae of the type found in Leftaena are not seen in the Silurian forms, but interrupted, sometimes zig-zag, rugae between the costellae are often well-developed, for example in C. wisgoriensis. This is in contrast to the simple costellae of the Caradocian species. This zig-zag type of ornament occurs many times in the Strophomenida and must be polyphyletic, perhaps the best-known example being the plectamboni- tacean Ptychoglyptus. In addition there occurs ir the Llandovery a form, described GEOL. 15, 6. 32 316 BRITISH LOWER SILURIAN below, which apparently lacks ornament of any kind, but has interior and general form very close to the Ordovician species. Thus to satisfactorily represent the close relationship between all these forms, but also to bring out their inherent differences, two new subgenera of Cyphomena are proposed here, one, Cyphomenoidea, to include forms with interrupted rugae, and the other, Laevicyphomena, to include forms, only one of which is at present known, which lack exterior ornament of any kind. CYPHOMENA (CYPHOMENOIDEA) subgen. nov. DiaGnosis. Cyphomena with parvicostellate ornament, the major ribs interrup- ting small, irregular rugae over the whole shell. TYPE SPECIES. Leptaena wisgoriensis Lamont & Gilbert 1945. RANGE. Llandovery, ?Wenlock Series. Discussion. The same type of ornament as appears on Cyphomenoidea may also be seen on many species of Pentlandina, for example the contemporaneous Pentlandina lovent (de Verneuil 1848) from the Visby Marl of Gotland. It is seen again on Strophomena julia Billings 1862 from the Jupiter Formation (Upper Llan- dovery) of Anticosti Island, Canada, but in this case illustrations of the interior are not available. A topotype in the British Museum (B 76891), a complete shell with both valves joined, has the correct profile for the new subgenus, but the species may be a strophomeninid and cannot be referred to Cyphomenoidea with confidence until the interior is known. Cyphomena (Cyphomenoidea) wisgoriensis (Lamont & Gilbert) (Pl. 12, figs. 9-12) 1945. Leptaena wisgoriensis Lamont & Gilbert : 660, pl. 3, figs. 10-14. 1951. Leptaena wisgoriensis Williams : 119. TYPE LOCALITY. Sunken track through Coneygore Coppice, near Alfrick, Wor- cestershire [Grid Ref. SO/7464 5111). Discussion. A full description of the species may be found in Lamont & Gilbert (1945 : 660-662). Although a large collection in the Oxford University Museum by Dr. Ziegler from the type locality failed to produce specimens of C. wisgoriensis, good material was found at Grid Ref. SO/7430 5152, less than a third of a mile away and at the same stratigraphical horizon, and some is illustrated here. A comparison of Pl. 12, fig. 10 with pl. 224, fig. 21 of Cooper (1956) reveals that the interior of the brachial valves of C. wisgoriensis and C. angulata Cooper are virtually identical, apart from the smaller size, more pronounced reflection of the ribbing (or possibly pallial sinuses) and slightly larger anterior median ridge of the latter species. In particular the distinctive shape of Cooper’s species, with a sharp geniculation and raised rim in the brachial valve and much more gentle curve without geniculation in the pedicle valve, together with the close similarity of internal structures in both valves, pronounce them to be close relatives. STROPHOMENACEAN BRACHIOPODS 317 The major difference between the two lies in the nature of the ornament, as men- tioned in the discussion of the genus. All three species described by Cooper have more or less equally costellate ornament, whereas C. wisgoriensis has a subequal parvicostellate ornament, upon which is superimposed small irregular rugae separated from each other by the larger ribs, forming a regular zig-zag pattern (Pl. 12, fig. 12). The species has been recognized only from the Wych Beds (C;_, in age) of the North Malverns and Ankerdine Hill, but a solitary external mould of a brachial valve from the Purple Shale of Hughley, Shropshire, has a similar ornament and may tentatively be referred to C. wisgoriensis. CYPHOMENA (LAEVICYPHOMENA) subgen. nov. DiaGnosis. Cyphomena with no shell ornament. TYPE SPECIES. Cyphomena (Laevicyphomena) feliciter sp. nov. RANGE. Middle to Upper Llandovery Series. Discussion. The new subgenus has as yet only one species attributed to it. Although it is fairly certain that the latter has no ornament, it has admittedly been found so far only in sandstone matrices, and it is possible that some sort of very fine ornament might have escaped detection. Cyphomena (Laevicyphomena) feliciter sp. nov. (Pl. 12, figs. 13-14, Pl. 13, figs. I-9) 1932. Styvopheodonta funiculata (M’Coy); Whittard pars, table facing p. 896. DiaGnosis. Smooth Cyphomena with laterally concave ridges in the brachial valve. DeEscrRIPTION. Exterior. Shape trapezoidal, varying sometimes to semicircular, particularly in the outline of the brachial geniculation. Sometimes slightly alate. Pedicle valve has a gradual convexity, always less than a total of 90 degrees, but brachial valve flat apart from its geniculation. No visible ornament, but fine growth-lines have been observed on the trail only of a few specimens, and the shell surface may be slightly buckled (rugate would be too definite a term) near the lateral extremities only. Interarea medium-sized to small for a leptaenid. Small chilidium. Functional foramen at apex of pedicle valve, below which is a small pseudodeltidium apparently not entirely covering the delthyrium. Pedicle interior. Thickened hinge line, the anterior edge of which diverges laterally away from the umbo until it reaches the edge of the trail, where it thins and becomes flush with the main shell. Prominent dental plates (but short in a dorsal direction) diverge at an angle of go degrees or more, and continue anteriorly as muscle bound- ing ridges which persist for a short distance in the same direction, but then swing through an angle of 60-80 degrees to converge again, though they do not meet. Thus the pedicle muscle field is somewhat similar to that of a strophomeninid, except when the species becomes gerontic (PI. 13, fig. 7), and an anterior fold connects GEOL. 15, 6. 328 318 BRITISH LOWER SILURIAN the two bounding ridges, overriding the median septum which in young specimens divides them. Rarely (e.g. Pl. 13, fig. 1) the muscle field presents a rather more bilobed appearance, with the median septum poorly developed except anteriorly. No trace of pseudopunctae seen. Brachial interior. Straight hinge line, to which is fused a pair of widely divergent socket plates. Two small cardinal process lobes approximately at right angles to the valve floor. Small platform, ending anteriorly with a very short, small median ridge, a trace of which may often be seen again in the anterior part of the disc, although it is never continuous. From approximately the antero-lateral end of the socket plates, and usually separated from them by a short gap, run a pair of ridges, subparallel to the median plane but concave outwards. The degree of concavity varies, and a small proportion are almost straight. These ridges bound the anterior pair of adductor muscle scars, which are particularly elongate. The posterior pair are smaller, approximately round, and situated immediately anterior of the socket plates. They are occasionally separated from the anterior adductors by two poorly-developed small nodes, which are just posterior of the point of closest proximity of the two bounding ridges. The geniculation is sharp (in contrast to the pedicle valve) and often associated with a marked interior rim, which is not reflected on the exterior. No trace of pseudopunctae observed. Ho.otyPe. BB 31346, a pedicle valve from the Bog Quartzite of Bog Mine, Shropshire [Grid Ref. SO/3510 9815]. Other localities (all in Shropshire): Napp Outlier [SO/3493 9922], Josey’s Wood [SJ/3653 0221] and Bank Outlier [SJ/3821 0418}. DIMENSIONS (in cm.) 1 w. BB 31346 Holotype, pedicle valve Bog 0:62 I°45 BB 31345 Paratype, pedical valve Bog 0-74 PF OP OUM Co895_ Paratype, pedicle valve Bog 0-70 I-40 OUM C10988 Paratype, pedicle valve Josey’s Wood 0-78 1°52 BB 31348 Paratype, brachial valve Bog OF 7 I-96 OUM Co893 ~Paratype, brachial valve = Bog 0:68 — BB 31347 Paratype, brachial valve Bog 0:69 neo BB 31352 Paratype, brachial valve Napp Outlier On 7 evan Discussion. It is unfortunate that this distinctive species should be preserved only in fairly coarse matrices, so that fine details of possible ornament or arrange- ment of pseudopunctae cannot be observed. So far the species is confined to the Bog Quartzite and Venusbank Formation of Shropshire; only two specimens (OUM Crog88 from Josey’s Wood and BB 31354 from Bank Outlier) have been recovered from the latter horizon, and the species does not occur above 1 % in any collection. C. feliciter is not far removed from C. wisgoriensis and other older species of Cyphomena, but differs from them in many ways—the lack of distinctive ornament, the development of the brachial ridges, and the general proportions and shape of the valves. However there are sufficient characteristics in common, particularly the general internal arrangement, the open foramen and small pseudodeltidium, SETROPHOMENACEAN BRACHIOPODS 319 and the geniculation angles in both valves, to enable the new species to be included in Cyphomena with a fair degree of confidence. Genus MACKERROVIA nov. DiaGnosis. Irregularly geniculate leptaenid with long diductor scars in the pedicle valve, bounded laterally by high irregular ridges, and partially mirrored in the brachial valve by long anterior adductor scars, bounded by less pronounced ridges. Shell surface often irregular. Very faint, often invisible ornament of differentiated parvicostellae. Pedicle atrophied in adults. TYPE SPECIES. Brachyprion arenaceus var. lobatus Lamont & Gilbert 1945 emended below, the only known species. Discussion. Mackerrovia is quite different from any genus yet described, and its attribution to the leptaeninids rather than to any other subfamily within the Strophomenidae is based mainly upon the geniculation. The most distinctive feature is the long muscle scars bounded by high ridges in the pedicle valve (and corresponding traces in the brachial valve). This is paralleled only by a homoeo- morphic development in the Stropheodontidae, namely Shaleria and to a lesser extent some species of Amphistrophia, but in these genera the ridges are much more uniform. The present genus is not a stropheodontid, despite its previous ascription to Brachyprion, and the whole internal structure is quite different, in addition to there being no trace of denticles on the hingeline. As well as possessing the long scars, Mackerrovia differs from other leptaeninid and strophomeninid genera in the usual absence of rugae and also the highly irregular shell surface, which is more reminiscent of some Upper Palaeozoic davidsoniaceans. The genus, known so far only from the higher part of the Upper Llandovery in the Welsh Borderland, is named after Dr. W. S. McKerrow. Mackerrovia lobatus (Lamont & Gilbert) (Pl. 13, figs. 10-15; Pl. 14, figs. 1-8) 1871. Strophomena avenacea {Salter MS] Davidson pars, pl. XLII, figs. 7-8, non fig. 6. 1945. Bvrachyprion avenaceus var. lobatus Lamont & Gilbert : 667, pl. VI, fig. 6, pl. VII, fig. 2. 1945. Byvachyprion arenaceus var. geniculatus Lamont & Gilbert : 669, pl. VI, figs. 1-5, pl. VII, fig. 3. 1953a. Brachyprion arenaceus var. geniculatus Lamont & Gilbert; Williams : 23. Diacnosis. As for genus. Description. Exterior. Shell shield-shaped with no alae. More or less sharp geniculation occurs at a variable length (occasionally, e.g. Pl. 13, fig. 15, two geni- culations are visible). Shell surface uneven and irregular in detail. Some speci- mens show well-developed growth lines. Ornament of extremely faint parvicos- tellae with even smaller stripes between them, but this is not seen on most specimens. Hingeline straight, but immediately anterior to it the shell often curves up (viewed from the posterior) from the umbo, Pseudodeltidium closes the delthyrium flush 320 BRITISH LOWER SILURIAN with the interarea, the latter being of variable size and sometimes scarcely developed at all in the brachial valve. No trace of a foramen observed. Pedicle interior. Thickened hingeline with medium-sized teeth that protrude anteriorly as well as ventrally. Long diductor muscle scars are of irregular shape and enclose long adductor scars separated by a small but persistent median ridge. Round the scars, posteriorly as an extension of the teeth, are long, high bounding ridges of variable shape, subparallel, concave or convex, or a mixture of the three. Sometimes they converge anteriorly (Pl. 14, fig.1), sometimes they diverge (Pl. 14, fig. 7). They usually double back round the anterior end of the diductors, but are always prevented from meeting by the median ridge. Usually the bounding ridges are not at right angles to the valve floor, but are directed dorso-laterally. The whole muscle area is not always in the median plane, and may be directed anteriorly either to right or left. Fairly large pseudopunctae visible on most specimens everywhere except on the muscle field. Brachial interior. Prominent cardinal process lobes directed ventrally, but diverge anteriorly. Long narrow sockets diverge at just over go degrees, bounded anteriorly by slender socket plates whose posterior half lies latero-posteriorly, and very close, to the cardinal process lobes. The socket is bounded posteriorly by a slight elevation of the hingeline. Very weak platform ends anteriorly in a broad, weak median ridge dividing the posterior pair of adductor muscle scars. The ridge bifurcates and then closes together again, leaving a faint pit (Pl. 14, fig. 5), after which it becomes narrow but more pronounced, dividing the anterior adductors and continuing, in some cases, nearly to the edge of the disc. No muscle bounding ridges near the umbo, but about a third of the way to the trail they suddenly appear, to persist strongly anteriorly for 5-10 mm., though never so pronounced as in the pedicle valve. Fairly large pseudopunctae visible everywhere except in the muscle field. LEcTOTYPE, here selected. GSM 11461, a pedicle valve from Wych Beds (Upper Llandovery), Gunwick Mill, Malvern Hills, Worcestershire. DIMENSIONS (in cm.). l w. Bristol 12143 Pedicle valve . 2-00 157 Bristol 12144 Pedicle valve . 1°93 2°46 Bristol 12159 Pedicle valve . 2°42 approx. 2:7 Bristol 12180 Pedicle valve . Zag, 3°08 Bristol T.1 Pedicle valve . : : Z2S3H0) approx. 2°5 OUM C652 ~=—- Tortworth pedicle valve . 2:08 I-92 OUM C654 +‘ May Hill sst.’ pedicle valve 2°50 approx. 2:7 OUM C5649 H-M-B pedicle valve T72 20% OUM C5641 H-M-B brachial valve length of trail . : rar a ar6 approx. I-I The widths quoted are those of the hingeline, which is by no means always the widest part of the valve. Discussion. Lamont & Gilbert did not fully describe their varieties, but gave good illustrations of the pedicle valves (although no brachial valves were shown), STROPHOMENACEAN BRACHIOPODS 321 and there is no doubt of the shells they had in mind, which are the same as that figured by Davidson (1871, pl. XLII, figs. 7, 8). The systematic situation surround- ing this species and Brachyprion arenacea has been discussed elsewhere (Cocks 1967 : 257). Lamont & Gilbert’s two ‘ varieties ’ are considered to be one homogeneous species, although this shows a remarkable range of variation in many details. They (1945) enumerated two differences between the varieties: (1) lobatws was more or less evenly curved, whereas geniculatus was geniculate, (11) they had found no specimens of lobatus with concave muscle boundary ridges, although they admitted that convex forms were to be seen in both varieties. In fact a collection from Gunwick Mill shows all variations of geniculation in a single rock band, and a specimen from collection T-R-A, OUM C3690/1, shows a lobatus (sensu Lamont & Gilbert) shell shape with concave ridges. Lamont & Gilbert (1945, p. 668) selected two syntypes, BU 397 and GSM 11461. As the first comes from 1030 feet down the Cooperative Society’s borehole at Walsall, I propose to select the second specimen as lectotype. This is also the first specimen figured by Davidson (1871, pl. XLII, fig. 7) and comes from Gunwick Mill [Grid Ref. SO/7430 5152], a locality in which the species occurs up to 5°% and may be procured easily today. In addition the Birmingham specimen is poorly preserved and incomplete, whereas the lectotype is well preserved and shows the typical musculature. The species is not common (never more than 5°%) at any locality, but has been found in the top part of the Upper Llandovery in beds of C; and C, age at Tortworth, May Hill, the Malverns, Ankerdine Hill, Shropshire, Rubery and Walsall, but has not so far been recovered outside the Welsh Borderland. BELLIMURINA Cooper, 1956 Bellimurina sp. (Pl. 14, figs. 9, 10) A single specimen in the British Museum, B 8490, not accurately localized, but from ‘Deerhope, Pentland Hills, Scotland,’ may be referred to Bellimurina, a genus not so far recorded apart from Cooper’s original description (1956) from the Middle Ordovician of America, and a record in the Caradocian of Girvan (Williams 1962). The specimen is a natural mould of an exterior of a brachial valve, and the attached cardinal area of a pedicle valve. Also on the same slab is a specimen of Eoplecto- donta which confirms the late Llandovery age of the specimen. The ornament of the leptaeninid is typical of Bellimurina; differentiated parvicostellae, the larger of which separate the pattern of broken rugae. The shell is much larger (length 1-83 cm.) than contemporary Cyphomenoidea, which has a similar ornament, and the irregular shell shape and rough geniculation with the frilly lamellae on the gerontic trail have not been found in the latter subgenus. Thus the stratigraphical range of Bellimurina is significantly increased. 322 BRL DTS LOW ERS DE UR WAN III. ACKNOWLEDGMENTS I would lke to thank Mr. J. M. Edmonds and Mr. H. P. Powell of the Oxford University Museum (OUM) for the curation of the collections from Shropshire which I made whilst at Oxford and for access to those of Dr. A. M. Ziegler from the southern Welsh Borderland, with the latter’s ready consent. Thanks also to Dr. A. W. A. Rushton of the Geological Survey & Museum (GSM), Mr. A. G. Brighton of the Sedgwick Museum, Cambridge (SM) and Dr. M. L. K. Curtis of the Bristol City Museum for the loan of other specimens. Most of the material is in the British Museum (Natural History) (B and BB). I am grateful for valuable advice on aspects of the systematic work from Professor Alwyn Williams, and thank also Dr. W. S. McKerrow. I have had useful discussion with Dr. V. Havli¢ek, who in addition generously allowed me access to his recent (1968) monograph before its publication. IV. REFERENCES AmMSDEN, T. W. 1949. Stratigraphy and paleontology of the Brownsport Formation (Silurian) of Western Tennessee. Bull. Peabody Mus. Nat. Hist., New Haven, 5 : 1-138, pls. 1-34. 1951. Brachiopods of the Henryhouse Formation (Silurian) of Oklahoma. /. Paleont. Tulsa, 25 : 69-96, pls. 15-20. Bancrort, B. B. 1949. Welsh Valentian Brachiopods and the STROPHOMENA ANTIQUATA group of fossil bvachiopods. 15 pp., 3 pls., privately printed. Mexborough. BARRANDE, J. 1848. Uber die Brachiopoden dey Silurischen Schichten von Boehmen. part 2. 104 pp., pls. 16-23. Vienna. 1879. Systeme silurien du centve de la Bohéme. \ere partie; volume V. Classe des Mollusques. Ordre des Brachiopodes. 226 pp., 153 pls. Prague & Paris. Boucot, A. J., JoHnson, J. G., Harper, C. W. & WatmMsLey, V. G. 1966. Silurian brachio pods and gastropods of Southern New Brunswick. Bull. geol. Suvv. Can., Ottawa, 140: 1-145, pls. 1-18. CHERNYCHEV, B. B. 10937. The Silurian brachiopods of Mongolia and Tuva (in Russian and English). Tvudy Mongolian Comm., 29. Izdatelstvo, Akad. sci. USSR., Moscow, 1-94, pls. 1-5. Cocxs, L. R. M. 1967. Llandovery stropheodontids from the Welsh Borderland. Palaeon- tology, London, 10 : 245-265, pls. 37-309. 1967a. Depth patterns in Silurian marine communities. MJarine Geol., Amsterdam, 5: 379-82. Cooper, G. A. 1956. Chazyan and related brachiopods. Smithson. Misc. Coll., Washington, 127 : 1-1245, pls. 1-269. Darman, J. W. 1828. Uppstallning och Beskrivning af de i sverige funne Terebratuliter. K. Svenska Vetensk. Akad. Hand., Stockholm, for 1827 : 85-155, pls. 1-6. Davipson, T. 1847. Observations on some of the Wenlock-limestone Brachiopoda, with descriptions of several new species. Lond. geol. Jl., 1 : 52-65, pls. 12, 13. 1848. Mémoire sur les Brachiopodes du systeme silurien supérieur d’Angleterre. Bul. Soc. géol. Fry., Paris, (2) 5 : 309-338, pl. 3. 1868. On the Upper Silurian Brachiopoda of the Pentland Hills, and of Lesmahagow, in Lanarkshire. Tvans. geol. Soc. Glasgow (Pal. Ser.) 1 : 1-24, pls. 1-3. 1871. British fossil Brachiopoda, 3, Part 7, no. 4, Silurian. Palaeontogy. Soc. |Monogy.], London, 24 : 249-397, pls. 38-50. 1883. Supplement to the fossil Brachiopoda, 5, Part 2, (Silurian). Palaeontogy. Soc. (Monogy.|, London, 37 : 135-142, pls. 8-17. STROPHOMENACEAN BRACHIOPODS 323 ForerstE, A. F. 1909. Preliminary notes on Cincinnatian fossils. Bull. sci. labs Denison Univ. 14 : 209-228, pl. 4. GAGEL, C. 1890. Die Brachiopoden der Cambrischen und Silurischen Geschiebe im Diluvium der Provinzen Ost-und Westpreussen. Betty. Naturk. Preuss, 1onigsberg, 6 : 1-79, pls. I-5. Hat, J. & CLARKE, J. M. 1894. An introduction to the study of the Genera of Palaeozoic Brachiopoda. Part 2. Palaeontology of New York 8 : (xvi) 1-394, pls. 21-84. Albany. HAvLiceK, V. 1963. Familie Leptaenidae (Brachiopoda) im Béhmischen Altpaléozoikum. Cas. Ndvodntho Muz. Odd., Prague, 82 : 220-225, pls. 1, 2. 1968. Brachiopoda of the suborder Strophomenida in Czechoslovakia. Rozpr. Ustr. Ust. Geol., Praha, 33 : 1-225, pls. 1-52. IMBRIE, J. 1956. Biometrical methods in the study of invertebrate fossils. Bull. Am. Mus. nat. Hist., Washington, 108 : 211-246. Kinpie, E. M. 1915. Notes on the geology and palaeontology of the Lower Saskatchewan River Valley. Bull. geol. Surv. Can. Mus., Ottawa, 21 : 1-25, pls. 1-4. Lamont, A. 1947. Gala-Tarannon Beds in the Pentland Hills, near Edinburgh. Geol. Mag., Lond., 84 : 193-208, 289-303. —— & GILBERT, D. L. F. 1945. Upper Llandovery Brachiopoda from Coneygore Coppice and Old Storridge Common, near Alfrick, Worcestershire. Ann. Mag. nat. Hist., London, ser. 11, 12 : 641-682, pls. 3-7. Linpstr6m, G. 1860. Bidrag till kannedomen om Gotlands Brachiopoder. Ofvers. K. Vetens. Akad. Férh., Stockholm, 17 : 337-382, pls. 12, 13. MircHeLt, G. H. & Myxura, W. 1962. The geology of the neighbourhood of Edinburgh. Mem. geol. Surv. U.K., London, 32 : 1-159, pls. 1-4. Murcuison, R. I. 1839. The Silurian svstem founded on geological vesearches in the counties of Salop, Hereford, Radnor, Montgomery, Caermarthen, Brecon, Pembroke, Monmouth, Glouces- ter, Worcester, and Stafford; with descriptions of the coal fields and overlying formations. 768 pp., pls. 1-37. London. Nixirorova, O. I. & ANDREEVA, O. N. 1961. Stratigraphy of the Ordovician and Silurian of the Siberian Platform and its palaeontological basis. (Brachiopods). Biostratigvaphiva Palaeozoya Sibirskov Platformy, Leningrad, 1 : 1-412, pls. 1-56. Reep, F. R. C. 1917. The Ordovician and Silurian Brachiopoda of the Girvan district. Trans. voy. Soc. Edinb., 51 : 795-998, pls. 18-22. SHALER, N.S. 1865. List of the Brachiopoda from the island of Anticosti sent by the Museum of Comparative Zoology to different institutions in exchange for other specimens, with annotations. Bull. Mus. comp. Zool. Havv., Cambridge, 1 : 61-70. SoxorsKAyA, A. N. 1954. Strophomenids of the Russian Platform (in Russian). Tvudy palaeont. Inst., Moscow, 51 : 1-191, pls. 1-18. 1g60. Order Strophomenida. In Osnovy Palaeontologu; Mshanki, brakhiopody, vol. ed. T. G. SarycHEva, Moscow : 1-324, pls. 1-75. SoweErRBy, J. de C. 1823-25. The Mineral Conchology of Great Britain, 5 : 171 pp., pls. 408— 503. London. SPJELDNAES, N. 1957. The middle Ordovician of the Oslo Region, Norway. 8. Brachiopods of the Suborder Strophomenida. Norsk geol. Tidssky., Bergen, 37 : 1-214, pls. 1-14. TWENHOFEL, W.H. 1928. Geology of AnticostiIsland. Mem. geol. Surv. Brch Can., Ottawa, 154 : 1-481, pls. 1-60. VERNEUIL, P. E. P. de, 1848. Note sur quelques Brachiopodes de Vile de Gothland. Bull. Soc. géol. Fr., Paris, (2) 5 : 339-353, pl. 4. WAHLENBERG, G. 1821. Petrificata Telluris Svecanae examinata. Nova Acta R. Soc. Scient. Upsal., 8 : 1-116, pls. 1-7 (for 1819). Wuittarpb, W. F. 1932. The stratigraphy of the Valentian rocks of Shropshire. The Long- mynd-Shelve and Breidden outcrops. Q. Jl geol. Soc. Lond., 87 : 859-902, pls. 58-62. Wirtiams, A. 1951. Llandovery brachiopods from Wales with special reference to the Llan- dovery district. Q. Jl geol. Soc. Lond., 107 : 85~136, pls. 3-8. BRI PSE TOW ERSTE UR TAN nN 324 1953. The classification of the strophomenoid brachiopods. jJ. Wash. Acad. Sci., 43 : I-13. 1953a. North American and European stropheodontids: their morphology and system- atics. Mem. geol. Soc. Am., New York, 56 : 1-67, pls. I-12. 1962. The stratigraphy and brachiopod faunas of the Barr and Lower Ardmillan Series (Caradoc) of the Girvan district of S.W. Ayrshire. Mem. geol. Soc. Lond., 3 : 1-267, pls. 1-25. —— 1963. The Caradocian brachiopod faunas of the Bala District, Merionethshire. Bull. By. Mus. nat. Hist. (Geol.), London, 8: 329-471, pls. 1-16. —— et al. 1905. Tveatise on Invertebrate Paleontology, Part H, Brachiopoda. Ed. R. C. Moore, Univ. Kansas and Geol. Soc. Am.: 1-297, figs. 1-746. ZIEGLER, A. M. 1965. Silurian marine communities and their environmental significance. Nature, London, 207 : 270-272. 1966. The Silurian brachiopod Eocoelia hemisphaerica (J. de C. Sowerby) and related species. Palaeontology, London, 9 : 523-543, pl. 83, 84. ——, Cocks, L. R. M. & BamBacn, R. K. 1968. The Composition and Structure of Lower Silurian Marine Communities. Lethaia, Oslo, 1: 1-27. DESCRIPTIONS OF PLATES Unless otherwise stated, all the specimens are coated with ammonium chloride. About half the photographs were taken by the author, the remainder by Mr. C. Keates. Specimens are in the British Museum (Natural History) (B and BB), Oxford University Museum (OUM), Sedgwick Museum, Cambridge (SMA) and Geological Survey and Museum (GSM) IIL ANID 1B, a Pentlandina tartana Bancroft Upper Llandovery, Bed D, Pentland Hills, Scotland. Collected by Mr. Henderson, now in the Davidson Collection. Fics. 1, 2. BB31447. Lectotype. Brachial internal mould and latex cast of it. 2:0. Fics. 3, 4. BB 31448. Pedicle internal mould and latex cast of it. 2:0. Fics. 5, 6. B8485. Brachial internal mould and latex cast of it. Note pallial sinuses. x 2:0. Pentlandina parva Bancroft Upper Llandovery, The Frolic, Haverfordwest, Pembrokeshire. Fic. 7. SMA 30013. Pedicle internal mould. x1-9. Fic. 8. SMA 30012. Holotype. Brachial internal mould. x 2:1. Pentlandina parabola sp. nov. Upper Llandovery, Purple Shale, Domas, Shropshire. Grid Ref. SJ/5936 0062. Author’s Collection. Fic. 9. OUM C13507. Holotype. Partly exfoliated pedicle valve. x 3:0. Fic. 10. OUM C13501. Complete specimen viewed posteriorly, although damaged at the apex and laterally. 06-6. Fig. 11. OUMCr13512. Brachialinternal mould. x 3:7. Upper Llandovery, Purple Shale, Boathouse Coppice, Shropshire. Grid Ref. SJ/6205 0398. Author’s Collection. Fic. 12, OUMC12856. Pedicle internal mould. x 4:5. Pentlandina sp. Middle Llandovery, Bog Quartzite, The Bog, Shropshire. Grid Ref. SO/3510 9815. Author’s Collection. Fig. 13. BB31299. Pedicle internal mould. x 2:0. Bull, By. Mus. nat. Hist. (Geol.) 15, 6 PAs GEOL. 15, 6. 33 Pea 2 Katastrophomena woodlandensis (Reed) Middle Llandovery, Woodland Point, Girvan, Ayrshire. Gray Collection. Fics. 1,2. B54490. Lectotype. Internal view of pedicle valve and latex cast of it. 1-5. Figured Reed 1917, pl. 18, fig. 2r. Fic. 3. B73012. Paratype. Figured Reed ror 7, pl. 19, fig. 4. External view of pedicle Walye, SK 15, Fic. 4. B54478. Paratype. Figured Reed ror 7, pl. 19, fig. 3. Brachial internal mould. x15. Fic. 5. BB31452. Posterior view of two conjoined valves. 1°5. Fics. 6, 7. BB 31426. Brachial internal mould, showing strong convexity and also pallial sinuses near the anterior margin. x 1°5. Fic. 8. BB 31420. Brachial internal mould which is Meadthyatla tamu ye lane Fic. 9. BB 31425. Brachial internal mould. x 1:5. Fic. to. BB 31427. Pedical internal mould. Note encrusting epizoon on inner surface. X15. Bull. Br. Mus. nat. Hist. (Geol.) 15, 6 PLATE 2 PLATE 3 Katastrophomena woodlandensis geniculata (Williams) Upper Llandovery, C, beds, Sefin River, Llandovery, Carmarthenshire. Grid Ref. SN/7418 2817. Fic. 1. SMA 30008. Holotype. Pedicle internal mould. x 1°5. Fic. 2. SMA 30007. Paratype. Brachial internal mould. x1°5. Katastrophomena scotica (Bancroft) Lower Llandovery, Gasworks Mudstone, opposite entrance to gasworks, Haverfordwest, Pembrokeshire. Grid Ref. SM/9588 1533. Fic. 3. SMA 32451. Brachial internal mould, figured Bancroft 1949, pl. 1, fig. 5. 1-0. Figs. 4-7. SMA 32193. Internal mould, external mould, latex of internal mould and latex of external mould of pedicle valve. Paratype. Figured Bancroft 1949, pl. 1, figs. 6,7. 1.5. Turnbull Collection. Fic. 8. SMA 32194. Lectotype. Pedicle internal mould, figured Bancroft 1949, pl. 1, fig. 4. <1°5. Turnbull Collection. Lower Llandovery, Gasworks Mudstone, quarry a few yards south of boathouse, midway between the springs, The Frolic, Haverfordwest, Pembrokeshire. Fic. 9. SMA 30000. Pedicle internal moulds, the right hand one figured Williams 1951, Dl WWW B36 wR, Pa AWE 3 Bull. Br. Mus. nat. Hist. (Geol.) 15, © PDE ACE Katastrophomena penkillensis (Reed) Upper Llandovery, Bargany Pond Burn, Girvan Ayrshire. Gray Collection. Fic. 1. B73013. Lectotype. Brachial internal mould, figured Reed 1917, pl. 18, fig. 11. S105}. Fic. 2. BB 31433. Pedicle internal mould. x 2:0. Fic. 3. BB 31432. Brachial internal mould. x 2:0. Fic. 4. B54480. Brachial external mould, figured Reed 1917, pl. 18, fig. 13. 1-5. Fic. 5. B73014. Pedicle internal mould, figured Reed 1917, pl. 18, fig. 12. 2:0. Upper Llandovery, Minsterley Formation, Minsterley-Habberley Lane, Shropshire. Grid Ref. SJ/3803 0487. Author’s Collection. Fic. 6. BB31408. Pedicle internal mould. x 2:2. Katastrophomena sp. Middle Llandovery, Bog Quartzite, The Bog, Shropshire. Grid Ref. SO/3510 9815. Author’s Collection. Fic. 7. BB31451. Brachial internal mould. x 3:0. Upper Llandovery, Venusbank Formation, The Corners, near Betton, Shropshire, Grid Ref. SJ/3141 0252. Author’s Collection. Fic, 8. BB31407. Pedicle internal mould. X1°5. Leptaena martinensis sp. nov. Lower Llandovery, Cartlett Mudstones, St. Martin’s Cemetery, Haverfordwest, Pembrokeshire. Turnbull Collection. lias. g-11. SMA 31865. Internal mould, external mould, and latex cast of external mould of pedicle valve. Holotype. x1°5. Pic. 12. SMA 31854. Brachial internal mould. x1°5. Fic. 13. SMA 31864. Internal mould of both valves, showing part of the brachial interior and part of the pedicle exterior. 1°5. Bull. Br. Mus. nat. Hist. (Geol.) PLATE 4 IL NTIS 5 Leptaena martinensis sp. nov. Lower Llandovery, Cartlett Mudstones, St. Martin’s Cemetery, Haverfordwest, Pembrokeshire. Turnbull Collection. Fics. 1-3. SMA 31859. Internal mould, external mould, and latex cast of external mould of pedicle valve of young individual. x 3:0. Leptaena haverfordensis Bancroft Lower Llandovery, Gasworks Mudstone, opposite entrance to gasworks, Haverfordwest, Pembrokeshire. Grid Ref. SM/9588 1533. Fic. 4. SMA 32163. Lectotype. Pedicle internal mould figured by Bancroft, 1949, Pl. 1, fig. 20. %1°5. Turnbull Collection. Fic. 5. BB 31327. Pedicle internal mould. %1°5. Author’s Collection. Fics. 6-9. BB 31355. External mould, internal mould, latex of internal mould and latex of external mould of pedicle valve. 1-5. C. P. Nuttall Collection. Fics. 10, 13. BB 31359. Internal mould and latex of pedicle valve. x1°5. C. P. Nuttall Collection. Fic. 11. SMA 32162. Pedicle internal mould figured Bancroft 1949, pl. 1, fig. 24. X15. Fic. 12. BB 31363. Latex of brachial external mould. 2:0. Author’s Collection. Fic. 14. SMA 40512. Pedicle internal mould, figured by Bancroft 1949, pl. 4, figs. 21, 22 {as L. haverfordensis var. contvacta| 16. Turnbull Collection. Fic. 15. SMA 32161. Brachial internal mould figured Bancroft 1949, pl. 1, fig. 23. 1°'5. Bull. By. Mus nat. Hist. (Geol.) 15 ball t Datars hy 5 iin , acim Hedge nr PLATE 6 Leptaena valida Bancroft Upper Llandovery, C, beds, Sefin River, Llandovery, Carmarthenshire. Grid Ref. SN/7418 2817. O. T. Jones Collection. Figs. 1-3. SMA 35690. Holotype. Internal mould, external mould, and latex of external mould of pedicle valve. Figured Bancroft 1949, pl. I, fig. 25. %1°5. Fic. 4. SMA 35691. Pedicle internal mould. Figured Bancroft 1940, pl. 1, fig. 26 [as L. elongata]. 1-5. Fic. 5. SMA 35692. Pedicle internal mould. Figured Bancroft 1949, pl. 1, fig. 27 [as L. elongata]. X1°5. Leptaena urbana Bancroft Upper Llandovery, C, beds. O.T. Jones Collection ‘ Locality 27 NW/E 48, quarry 500 yards NE of Cefn Cerig ’, Llandovery, Carmarthenshire. Fic. 6. SMA 35693. Lectotype. Pedicle internal mould. Figured Bancroft 1949, pl. 2, Gf, It, © $< 1107). Fic. 7. SMA 35694. Brachialinternal mould. Figured Bancroft 1949, pl. 2, fig.2. XTI-o. Leptaena contermina sp. nov. Middle Llandovery, Venusbank Formation, Hope Quarry, Shropshire. Grid Ref. SJ/3551 0208. Author’s Collection. Fiaes. 8, 11. OUM Co168. Holotype. Pedicle internal mould and latex of it. x 2-0. Fics. 9, 12. OUM Cor47. Internal mould and latex of brachial valve. x 2-0. Fics. 10, 13. OUMCg9155. Two views of brachial internal mould, the former oblique to show details of cardinalia. Bull. Br. Mus. nat. Hist. (Geol.) 15, © PLATE 6 PLATE 7 Leptaena contermina sp. nov. Middle Llandovery, Bog Quartzite, The Bog, Shropshire. Grid Ref. SO/3510 9815. Author’s Collection. Fic. 1. BB 31280. Pedicle internal mould. 1-5. Note also fragment of Leonaspis sp. Fic. 2. BB31289. Pedicle internal mould. x 2:0. Fics. 3, 4. OUMCros5o0r1. Brachial internal and external moulds. x 1°5. Fic. 5. BB 31283. Brachial external mould. x 2:2. Fic. 6. BB 31281. Pedicle internal mould. x1°8. Upper Llandovery, Yartleton Beds, May Hill, Gloucestershire. Grid Ref. SO/6936 2271. A. M. Ziegler Collection. Fics. 7, 8. OUMC2805. Brachial internal mould and latex cast of it. x 1-7. Upper Llandovery, Cowleigh Park Beds, Ankerdine Hill, Worcestershire. Grid Ref. SO/7376 5696. A. M. Ziegler Collection. Pies. 9-11. OUM C7390. Two views of pedicle internal mould and also a latex cast of it. X 2:0. Bull. Br. Mus. nat. Hist. (Geol.) 15, 6 PEATE 7 PLATE 8 Leptaena valentia sp. nov. Middle Llandovery, Woodland Point, Girvan, Ayrshire, Scotland. Gray Collection. Fics. 1-3. B 73340. Holotype. Complete shell, figured Reed 1917, pl. 13, fig. 5. 1-5. Fics. 4, 5. BB55620. Latex cast and internal mould of pedicle valve. 1-5. Fic. 6. BB55718. Latex cast of brachial external. 2-0. Fies. 7, 8. BB55688. Latex cast (x 1-6) and internal (x 2-0) of brachial valve. Leptaena valentia mullochensis subsp. nov. Lower Llandovery, Mulloch Hill, Girvan, Ayrshire, Scotland. Gray Collection. Fic. 9. B 73384. Holotype. Partly exfoliated pedicle valve, figured Reed 1917, pl 13, ft Car Ante 15) Fics. 10, 11. B 73379. Internal mould of both valves viewed from either side. x 2:0. Fic. 12. BB 31375. Pedicle internal mould. x 2-0. Fic. 13. BB31383. Pedicle internal mould. x 2:0. Fic. 14. B 73381. Pedicle internal mould. x 2:0. Fic. 15. BB 31386. Brachial internal mould. x 2:0. PLATE 8 Bull. By. Mus. nat. Hist. (Geol.) 15, 6 Fic. Fic. Fic. Fic. Fia. 5. WN H PLATE 9 Leptaena zeta Lamont, 1947 Upper Llandovery, Penkill, Girvan, Ayrshire, Scotland. Gray Collection. B 73355. Lectotype. Pedicle valve, figured Reed 1917, pl. 13, fig. 8. X1°5. BB 31302. Pedicle internal mould. x1-8. BB 31305. Pedicle internal mould. x 1-8. BB 31303. Pedicle internal mould. x1-8. Upper Llandovery, Bargany Pond Burn, Girvan, Ayrshire, Scotland GSM 4108. Brachial internal mould. x1°8. Upper Llandovery, Minsterley Formation, Minsterley-Habberley Lane, Shropshire. Fic. 6. Grid Ref. SJ/3803 0487. Author’s Collection. BB 31468. Brachial internal mould. x 2:2. Bull. By. Mus. nat. Hist. (Geol.) 15, 6 PLATE 9 GEOL. 15, 6. 34 PLATE to Leptaena reedi sp. nov. Middle Llandovery, Woodland Point, Girvan, Ayrshire. Gray Collection. Fic. 1. B 73341. Complete shell, figured Reed 1917, pl. 13, fig. 7. Holotype. x 3-0. Fics. 2, 3. B 73345. Pedicle valve. x 3-0. Fics. 4, 5. BB31460. External mould of brachial valve and pedicle interarea, and latex Cast Of them: x 2:0) Fic. 6. BB 31459. Brachial internal. x 3-0. Fic. 7. BB 31458. Pedicle internal mould. 3-0. Fic. 8. B 73342. Brachialinternal. x 2-0. Fics. 9-12. BB 31457. Two views each of pedicle internal mould and latex cast of it. Note close association with L. valentia. 2-0. Fic. 13. BB31461. Brachial external mould. 3:0. Fic. 14. B 73346. Complete shell. 3:0. Bull. Br. Mus. nat. Hist. (Geol.) 15, 6 IRL NADIE, ae (0) Pi Agr ear Leptaena ziegleri sp. nov. Upper Llandovery, Wych Beds, Malvern Hills, Herefordshire. Grid Ref. SO/7612 3811. A.M. Ziegler Collection. Fics. 1, 2. OUM C4146. Pedicle internal mould and latex of it. Holotype. x 3:3. Fics. 3-5. OUM C4136. Internal mould, latex of it and external mould of brachial valve. MK BB. Leptaena quadrata Bancroft Upper Llandovery. O. T. Jones locality ‘Loc. K, below path SW of Uzmaston’, The Frolic, near Haverfordwest, Pembrokeshire. Fics. 6-8. SMA 32437. Internal mould, external mould, and latex of external mould of pedicle valve. Lectotype. Figured Bancroft 1949 pl. 1, fig. 28. x 3:0. Fic. 9. SMA 32438. Brachial internal mould, figured Bancroft 1949, pl. 1, fig. 29. 3:0. Fic. 10. SMA 32439. Pedicle internal mould, figured Bancroft 1949, pl. 1, fig. 30. ™ 3:5. Bull. Br. Mus. nat. Hist. (Geol.) 15, © ID NARA ert PLATE 12 Leptaena purpurea sp. nov. Upper Llandovery, Purple Shale, Shropshire, various localities. Collected W. F. Whittard and author. Fic. 1. BB 31465. Holotype. Pedicle internal mould, also pedicle internal mould of Glassia obovata (J. de C. Sowerby). Domas. Grid Ref. SJ/5936 0062. x 2°5. Fic. 2. BB31463. Pedicle internal mould. Gippols Dingle. Grid Ref. SO/5727 9937. x 2:5. Fic. 3. BB 31466. Brachial valve, also Aegivia grayi (Davidson). Hughley. Grid Ref. SO/5639 9809. x 3:0. Fic. 4. OUMC12062. Pedicle internal mould. Onny River. Grid Ref. S/O4260 8532. X 3:0. Fic. 5. BB 31464. Pedicle internal mould. Hughley. Grid Ref. SO/56379795. x2°5. Leptaena ci. purpurea sp. nov. Upper Llandovery, Damery Beds, eastern bank of railway cutting, immediately north of road bridge, Charfield Station, Gloucestershire. M. L. K. Curtis Collection. Fic. 6. Bristol University Museum 12101. Pedicle internal mould. x 1°8. Leptaena sp. Upper Llandovery, Purple Shale, ‘ Harley ’, Shropshire. W. F. Whittard Collection. Fics. 7, 8. BB31467. Complete shell viewed dorsally (x 1-6) and posteriorly (x 2:5). Cyphomena (Cyphomenoidea) wisgoriensis (Lamont & Gilbert, 1945) Upper Llandovery, Wyche Beds, Malvern Hills, Herefordshire. Grid Ref. SO/7430 5152. A. M. Ziegler Collection. Fic. 9. OUM C5638. Pedicle internal mould. x 1-7. Fic. 10. OUM C5631. Brachial internal mould. x 1-9. Fic. 11. OUMC5615. Brachial internal mould. x 2-0. Fic. 12. OUMC5612. Brachial external mould. x 2:8. Cyphomena (Laevicyphomena) feliciter sp. nov. Middle Llandovery, Bog Quartzite, The Bog, Shropshire. Grid Ref. SO/3510 9815. Author’s Collection. Fics. 13, 14. BB 31346. Holotype. Pedicle internal mould and latex cast of it. x 3:0. 2 I 4 PIA Bull. Br. Mus. nat. Hist. (Geol.) 15, 6 PAV S63 Cyphomena (Laevicyphomena) feliciter sp. nov. Middle Llandovery, Bog Quartzite, The Bog, Shropshire. Grid Ref. SO/3510 9815. Author’s Collection. Fic. 1. OUM C9895. Pedicle internal mould. x 2:3. Fic. 2. BB 31347. Brachial internal mould. x 2-7. Fic. 3. BB31351. Brachial internal mould. x 2-6. Fic. 4. BB 31348. Brachial internal mould. x 2:0. Fics. 5, 6. OUM C9893. Brachial internal and external moulds. x 2°5. Middle Llandovery, Venusbank Formation, Josey’s Wood, Shropshire. Grid Ref. SJ/3653 0221. Author’s Collection. FIG. 7. OUM C10988. Pedicle internal mould. x 2:2. Middle Llandovery, Bog Quartzite, Napp Outlier, Shropshire. Grid Ref. SO/3491 9932. W. F. Whittard Collection. Fics. 8, 9. BB 31352. Pedicle internal mould (x 2-0) and latex cast of it ( x 3:0). Mackerrovia lobatus (Lamont & Gilbert, 1945) Upper Llandovery, Damery Beds, old working about 260 yards W 25° N of Damery Bridge, near Tortworth, Gloucestershire. M. L. K. Curtis Collection. Fics. to-12. Bristol University Museum 12180. Pedicle internal mould and latex cast of it. X15. Upper Llandovery, Damery Beds, Ironmill Grove, Damery, near Tortworth, Gloucestershire. M. L. K. Curtis Collection. Fics. 13-15. Bristol University Museum 12143. Internal mould, latex cast and external mould of pedicle valve. 1-5. Bull. By. Mus. nat. Hist. (Geol.) 15, 6 PLATE 14 Mackerrovia lobatus (Lamont & Gilbert, 1945) Upper Llandovery, Damery Beds, Tortworth Inher, various localities. M. L. K. Curtis and A. M. Ziegler Collections. Fics. 1, 2. Bristol University Museum 12159. Avening Green. Pedicle internal mould and lennesc CASE OH TE, SK 1095), Fic. 3. Bristol City Museum Tl. Western end of Ironmill Wood, Damery. Pedicle internal mould. xX 1-7. Fic. 4. Bristol University Museum 12144. Field, 200 yards NW of Avening Green. Pedicle internal mould. x 1-4. Fic. 5. OUM C3686. Railway cutting 60 yards NW of railway bridge at Charfield Station. Brachial internal mould. x 2:0. Upper Llandovery, Wych Beds, Malvern Hills, Herefordshire. Grid Ref. SO/7430 5152. A.M. Ziegler Collection. Fic. 6. OUMCs5649. Pedicle internal mould. x 2-0. Fic. 8. OUM C5641. Brachial internal mould. x 2-0. Upper Llandovery, in Oxford University Museum with old label ‘May Hill Sandstone ’ only. The lithology is probably that of the May Hill Inlier, Gloucestershire. Fic. 7. OUM C654. Pedicle and brachial internal moulds. 1-2. Bellimurina sp. Upper Llandovery, Deerhope Burn, Pentland Hills, Scotland. Fics. 9, 10. B8490. External mould and latex cast of brachial external and pedicle interarea. X I°5. Bull. By. Mus. nat. Hist. (Geol.) 15, 6 \ "\ INDEX TO VOLUME XY New taxonomic names and the page numbers of the principal references are printed in Bold type. An asterisk (*) denotes a figure. acanthophyllids 206 Acanthophyllinae 206 Acanthophyllum 188 Acervularia 211-13, 231 baltica 212 coronata 213-15, 220 goldfussi 231, 236, 247-9, 253 limitata 248-9, 253 macrommata 213 pentagona 233, 248 voemevyi 212, 214-5, 220 Seviaca 253, 257 troscheli 228 ? Acervularia voemeri var. B concinna 243, 245 Acinophyllum 271-73 simcoense 272 Actinocyathus 212 hennahii 214 ‘algae’ 136, I5I, 161 Aegivomena 88-92 Allovirgatites 5, 22 vobustus 45-6 tutcheri 48-9 versicostatus 45-6 woodwardi 22, 45-6 Alveolites 188 AMMONITES I-79 Evolution 64—66 Homeomorphy 19-20, 23, 66, 75 Intersex 54 Kimmeridgian faunas 4-5, 66-76 Rib characters 22-3, 25, 32, 38, 40, 51 Sexual Dimorphism 15-18 Ammonites biplex 5 gigas 12 gravesianus 12, 14 pectinatus 14, 19, 59 scyuposus 19 ulmensis 19 virgatus 18 AMMONOIDEA see Cephalopoda Amphistrophia 319 whittardi 313 Ampyx 93-4 abnormalis 95 camurus 94 linleyensis 94 nasutus 94 nitidus 86, 88, 93, 94-95 ; Pl. 5, figs. 5, 8-11 virginiensis 94 Anomites rhomboidalis 300 Avachnophyllum 211 hennahi 214 Arkellites 8, 9, 18, 21, 24, 25, 64, 65* Asaphidae 121 Asaphid gen. & sp. indet. 91, 121, 122 ; Pl. 10, figs. 2, 5 Aschemonia 132 gigantea 134 Astraea hennahit 212, 214 intercellulosa 214, 215, 220 pentagona 233 “ Astrea hennahii’ 184, 212, 214-15 parallela 212 Astrea (Favastrea) pentagona 233, 247, 253 Astrea (Sidevastrea) hennahi 214 Ataxioceras 23 ataxioceratids 24 Aulacostephanus 68 Aulina 212 Barton Quarry, Devon (Middle Devonian) 186-187, 188, 201 samples 217, 218, 220, 225 Bedinan Formation, Turkey 85, 86*, 87*, 88, 89, 91, 97 faunas, age of 91 relationship 91 Bellimurina 299, 321 Bellimurina sp. 321 ; Pl. 14, figs. 9, 10 Bensonastraea 214 Billingsastraea 206, 207, 213, 231, 232 ? battersbyi 186 goldfussi 248 verneuili 232 Bilobites 153 Bornes, trace fossils 156, 161 BRACHIOPODA 283-324 homeomorphy 319 lineages 286, 299, 302*, 315 phylogeny 286, 299, 302*, 315 stratigraphical Great Britain Upper Ordovician 294, 299, 300, 315 326 INDEX Silurian (283-324), 286, 294, 299, 300, 315 CEPHALOPODA Landovery 286, 288, 291-294, 298-301, 302* Kimmeridgian 10 Turkey, Ordovician 88, 90, 92 Brachyprion 319 avenacea 321 avenaceus var. lobatus 319, 321 var. geniculatus 319, 321 Bracteoleptaena 299 Brongniartella 92, 118-120 bisulcata 119 cavadocia 119 imexpectata 119, 120 levis 88, 118, 119, 120 ; Pl. 8, figs. 2, 3, 6 platynota 92, 119 sp. 88 ; Pl. 8, figs. 1, 5 Burrows, Trace fossils. See also Thalassinoides, Ammonoidea 1-79 Collecting techniques 11 Evolution 64-66 Homeomorphy 19, 20, 23, 66, 75 Intersex 54 Kimmeridgian 11-13 faunas 4—5, 66-76 Microconch horn 17-18 lappetts 18 Palaeoecology 16 Preservation 11 Ribs 11-13*, 15, 17 tib characters 22-23, 25, 32, 38, 40, 51 rib direction 13 tib types 13 Sexual Dimorphism 15-18 Chondrites, Spongeliomorpha and ‘Terebrella’. CHALK, Lower 125-167 Association with hardgrounds 147-8 laminated structures 133, 138-41 burrowing organisms 137, 138, 147-161 branching 131, 136, 142, 147 callianassid burrows 130-132, 137 comparable assemblages 161 controls, phobotactic 149 geotropic 150 crustacean burrows 130-32, 136-7, I5I, 156, 158, 161 dimensions 132, 134, 136, 140-142 Bottom conditions 129 Burrows in 130-34, 137, 140, 142-43, 146, 149, 150, 152-4, 156, 160 composition of 129 depth of deposition 129-30 fauna 161-62 Mollusca 129 occurrence 128 preservation of burrows 131, 137 sedimentation 128-29 Trace fossils 154-55, 161 explanations of 149-158, 160-162 CHANDLER, M. E. J. 169-179 laminated structures 133*, 138*, 139-141, Cheirurid gen. & sp. indet. 88, 114, 115 ; Pl. ro, 155 ; Pl. 1, fig. 4 ; Pl. 5, fig, r ; Pl. 8, fig. 3 fig. 3 patterns of 132, 133*, 134, 135*, 142, 143*, Chondrites 148-150, 161 146*, 147 Pellets in ; sand 130 ; faecal 130, 137-8 problematic burrows 158 scratch marks 151, 153, 155-56 walls 147, 149, 158 worm burrows 151, 158, 160 Burrow type A 156 157*, 158 type B 157, 158 type C 158, 159*, 160 type D 160, 161 ; Pl. 5, fig, 4; Pl. 7, figs. I, 4, 5 ; Pl. 9, fig. 5 type E 161 ; Pl. 2, fig. 3 associations 149, 150 branching 148, 149 ; Pl. 9, fig. 1 ; Pl. 5, fig. 3 diagnostic features 148 dimensions 149 feeding 150 interpretation 148, 150 occurrence 149, 150 patterns 148, 149 phobotactis 149 size range 148 tunnels 149, 150 walls 149 Buthrotrephis 148 Chondrites sp. 149, 150 ; Pl. 2, figs. 2-4 ; Pl. 5, fig. 3 ; Pl. 9, fig. x Christianiidae 286, 287 Calcidelectvix 161 Cladcova antiqua 2606 Callianassa major 130, 137 Climacograptus sp. 89, 91, 92 sp. I31, 162 Cliona 161 callianassids 162 Clorvinda community (Silurian, Lland.) 288, 313 association with trace fossils 131-32 Cocks, L. R. M. 283-324 Calymenacea 118 Codites neocomiensis 161 Calymene biymanica 117 COELENTERATA see also under Phillipsastraeidae Cambarus carvolinus 156 CaMBRIAN, Turkey 84, 85 Campophyllidae 208 Cerithium 10 biometric techiques 199-200 cerioid corals 194 Classification 205-208 Devonian 181-281 INDEX 327 Dissepiments dissepimental form 184, 207-209, 280 horseshoe type 184, 190, 198, 205-206, 207-209, 281 in classification 206-208 peneckielloid 208—209 fan-systems 206-208 Increase in colonial Phillipsastraeidae 193-97 axial increase 193*, 194, 195-197*, 198 intercalcinal 193*, 194 intermural 194 lateral 193*, 194, 195*, 196* thamnophylloid & lateral 195, 196 polyp fusion 201-203 massive corals 192-94, 199, 201, 203, 205, 207, 280 microstructure of, 190-93 phaceloid corals 194, 198, 199, 201, 205 plocoid corals 193, 194 pseudocerioid corals 194 Septa function 192 holotheca 193 microstructure 190, 206 pseudotheca 192, 196 septal insertion 193 septal size 203-4 variation in septal number 203-4 septal ratio 203, 204, 205 septal size 205 Standard statistics of, 199-200 Terminology cerioid 192, 194 plocoid 194 pseudocerioid 192* 194, 280 Trabeculae development of carination 190 septal trabeculae 206-8 trabecular fans 206-8 trabecular structure 190, 191* Variation in colonial corals average corallite area 199-200 average tabularium area 199-200 dimensions 198-9 general trends 198-204 septa-tabularium ratio 199, 202, 204 standard statistics I9g9—200 tabularium : corallite area ratio 199-200 tabularium : corallite diameter ratio 199,202 variation in diameter 200, 201-2 septal number 203 septal ratio 203 size 201-203 tabularium 201 Colpocoryphe 120 grandis 120 sp. 85, 88-90, 120 ; Pl. 9, figs. 5, 6,9, 10 Columnariidae 209 Conodonts, Upper Devonian 189 Coolinia 313 CopgE, J. C. W. 1-79 Corals, see Coelenterata Corophioides 150 CRETACEOUS Germany 132, 158 Great Britain, Southern England 125-167 Chalk Marl 130 Glauconitic Marl 128, 140, 149, 152-3 Lower Chalk see under Chalk Paradoxia Bed, trace fossils 142, 144-47 Plenus Marls, burrows in, 128, 154-5 Red Chalk 144-5, 147 Totternhoe Stone 128-9, 137, I40-I, 149- 50, 152 Weald Clay 151 Tempskya 171, 177 Trace fossils 125-167 CRUSTACEA brachyurous crustaceans 162 callianassid burrows 130-23, 137 callianassids 162 crustacean borings 156 crustacean burrows 136-7, 151, 156, 158, 161 decapod burrows 156 feeding traces 139, 155 fossil crustacea 162 fossil crustacean burrows 129, I5I laminated structures 139 Lower Chalk crustacea 161-2 macrurous crustaceans 162 scratch marks 151, 153, 155 Cruziana 153 Cryptolithinae 95, 97 Cryptolithus 92, 95-6, 102, 107 cf. inopinatus 108 tesselatus 95 ? Cryptolithus bedinanensis 88, tor, 104, 105-9; Pl. 3, figs, 1-7, 9 ; Pl. 4, figs. 2-9 cf. bedinanensis 107 inferus 88, ror, 102, 103-4, 108 ; Pl. 2, figs. 6-8 cf. inferus 88, 102-3 ; Pl. 2, figs. 2, 4, 7, 12 Sp bly2 ieecOn) Plies fie. “Cryptolithus’ sp. 108 Cyathophyllidae 208 Cyathophyllum ananas 228, 247, 249, 253 caespitosum 266 caespitosum trigemme 260 minus 273 pentagonum 231, 233, 236 Cylindrites 136 vimosus 161 Cylindrites saxonicus 134 spongioides 134, 136-37, 145, 158 suevicus 140 Cyphomena 299, 301, 311, 315, 316-19 angulata 316 (Laevicyphomena) 317 328 INDEX feliciter 288, 317, 318 ; Pl. 12, figs. 13-14 ; Pl. 13, figs. 1-9 Cyphomenoidea 316, 321 (Cyphomenoidea) wisgoriensis 288, 315, 316, 317-18 ; Pl. 12, figs. 9-12 CZECHOSLOVAKIA Correlation with Ordovician, Bohemian faunas QI-2, 95, 108-9 Stratigraphy 91-2 Trilobita 109, 112, 114 Dadas Formation, Turkey 88 Dalmanitidae 112 Dalmanitina 86, 88, 90, 112, 113 proaeva cilinensis 112 grandis 112 proaeva 88, 91, 112, 113 ; Pl. 6, figs. I-9, 11-13 ; Pl. 7, figs. 4-5 Socialis 112-13 davidsoniaceans 319 DEAN, W. T. 81-123 DEVON Devonian localities 185, 186*, 187-8 Fossil coelenterates 181-281 DEVONIAN Fossil coelenterates/corals 181-281 variation in 198-204 Great Britain Devonian 185, 187 Middle 188 Upper 189 Localities 185, 186*, 187 Frasnian 189 fossil markers 188 cordatum Zone 189 holzapfeli Zone 189 lunulicostata Zone 189 Givetian Middle 185-7 Upper 188 Diaulax 162 Dicoelosia cf. alticavatus 313 Dictyoporus 161 Dionide 109, 111-112 asiatica 112 aiva 112 Dionide euglypta var. quadvata 112 formosa 91, 109, 110 anatolica 90-1, 109, 110-12 ; Pl. 5, figs. 1-4 On7au2 formosa 11-12 hybride 112 jubata 110, 112 turbulli 112 Dionididae 109 Diphyphyllum minus 261, 272 Diplograptus sp. 89, 92 Discina latissima 7-10 Discosphinctes 24 Disphyllidae 205-209 disphyllids 207-8 Disphyllinae 206 Disphyllum 205, 208, 258, 271 Disphyllum (Phacellophyllum) 257 caespitosum 266 DORSET Upper Kimmeridge Clay ammonites 1-79 Dorsoplanitinae 63 Dyers Quarry, Devon (Middle Devonian) 185 186*, 198 Dysidea 150 ECHINODERMATA Kimmeridgian, crinoid 10 ENGLAND Devonian corals 181-281 Devonian localities, Devon 185-187 Dorset, Kimmeridgian ammonites 1-79 Upper Kimmeridge Clay 70-71 Lower Chalk, trace fossils 125-167 Silurian, brachiopods 288-315 Enoploclytia 129, 162 EOCENE Trace fossils Australia 132 France 151 Great Britain 158 Eocelia 286 Eocelia community (Silurian, Llandovery) 288 Eohomalonotidae 118 Eoplectodonta 321 millinensis 313 Eospivifey sp. 313 Evismatilithus Madveporites vadiatus 212 Erodophyllinae 206 Exogyra virgula 9, 10, 69 Fascicularia caespitosa 266 Favastraea intercellulosa 214 Felixium 150-51 Filuroda 161 Foliomenidae 286, 287 FRANCE Trace fossils, Eocene 151 Upper Kimmeridgian, Boulonnais 72-73 Frechastraea 192, 195, 201, 203, 209, 213, 230, 231, 232-57 bowerbanki 189, 192, 195, 201, 202, 240, 246-47, 253, 254-57 ; Pl. 11, fig. 3 ; Pl. 12, figs. 1-3 carinata 189-91*, 192, 195, 202, 241, 242, 243-47 ; Pl. 9, figs. 1-3 goldfussi 189, 192*, 193*, 195*, 201-203, 246, 247, 248-253, 280 ; Pl. 10, figs. 1-5 ; Pl. 11, figs. I-2 micrommata 193, 195, 240, 241-42 ; Pl. 8, figs. 4,5 pentagona 280 minima 189, 193*, 195*, 202, 236, 237-40, 245-47, 257, 281, Pl. 8, figs. 1-3 INDEX 329 pentagona 189, I91*, 192, 195* 202, 233, 234*—-36, 240, 245-47, 253, 281 ; Pl. 6, fig. 5; Pl. 7, figs. 1-5 Fucoides targionii 148 fucoids 132, 136, 151, 161 Furcitella 294 Furcitellinae, (Strophomenidae) 286, 288, 293, 204 geotropic control, Trace fossils 150 GERMANY Southern (Franconia) Upper Kimmeridgian 73-75 Tithonian 5, 73-75 Trace fossils 132, 134, 140, 151, 156, 158, 161 Glauconitic Marl, burrows in 128, 140, 149, 152, 153 Glyphea willeti 162 Glyptomeninae 286 GRAPTOLITES Turkey, Ordovician 92 Gravesia 23, 66, 68, 72, 75 cf. gravesiana 9, 14 ; Pl. 1, fig. 2 gravesiana 14, 66, 68-69 gigas 9, 12*, 14, 68 ; Pl. 1, fig. 1 ivius 14, 66, 68 GREAT BRITAIN Devonian 185-187 Devonian corals 181-281 Lower Chalk, trace fossils 125-167 Silurian Brachiopoda 283-324 GREENLAND Upper Kimmeridgian 73 Gunnarella 289 Gyrolithes 132, 137, 150 dewalquei 161 Halymenites cylindricus 136 Haplothecia 207, 213 filata 213 ogwellensis 189 pengellyi 187-88, 201 Heliophyllum cf. limitatum 248 troscheli 228 Hexagonaria 205-206, 231-32 jirthi 192* hexagona 232 Holtedahlina 288 parva 291 Houghton Regis, (Cenomanian) trace fossil locality 127, 133, 137, 149, 152 Hunstanton, Cretaceous trace fossils 128, 143-6, 157 Hypothyridina procuboides 188 Ichnology, see Trace fossils 125-167 Ichthyosaurus 8, 10 Ilovaiskya 75 Inocevamus 129 expansus 8, It IRAQ Ordovician, Sinat Shales 91 JURASSIC Ammonites, Dorset 1-79 Stratigraphy, Kimmeridgian 1-79 see also under Kimmeridge Clay Trace fossils 132, 135, 161 Katastrophomena 288, 291, 293, 294-98 penkillensis 288, 291, 294, 296, 297, 298 ; Pl. 4, figs. 1-6 scotica 288, 294, 296, 297 ; Pl. 3, figs. 3-9 woodlandensis 288, 294, 295, 296, 298 ; Pl. 2, figs. I-10 woodlandensis geniculata 294, 296 ; Pl. 3, figs. Tyce sp. 298-99 ; Pl. 4, figs. 7 & 8 Keckia ? sp. 131, 155 KENNEDY, W. J. 125-167 Keratinites 21, 59 cornutifer 62 kevatophorus 21 naso 62 nasutus 62 ? Keriophylloides 209, 211 Kimmeridge Clay 1-79 Blackstone 8, 18, 19, 21 Cattle Ledge Shales 9, 68-9, 71 Grey Ledge Stone Band 9, 68, 69 Hen Cliff Shales 9, 71 Kimmeridge Oil Shale—see Blackstone Rope Lake Head Stone 9, 69 Yellow Ledge Stone Band 9, 66, 68 Upper Kimmeridge Clay 1-79 Ammonite faunas 66-76 Blake’s bed numbers 7-10 East Greenland 73 France 72-73 Germany 73-75 Great Britain 70-72 Kimmeridge-Portlandian boundary 75 Russia 75-76 Zones 66—70 Kimmeridgian 1-79 Lower 4 Upper 1-79 elegans Zone 64-5, 72-3 hudlestoni Zone 65, 73 pectinatus Zone 18, 65, 73 scitulus Zone 65, 68, 72-3 virgatites Zone 72 wheatleyensis Zone 47, 65, 69, 73 Zones 4—5, 7-10, 66-70 Aulacostephanus Zone 67-8, 72-3 Aulacostephanus autisiodorensis Zone 7 33° INDEX Gravesia spp. Zones 67-8, 72 Gravesia gigas Zone 67-8 gravesiana Zone 67-8 irius Zone 67 Pectinatites pectinatus Zone 67 Pectinatites (Arkellites) hudlestoni Zone 8, 67, 69-71* (Pectinatites) pectinatus Zone 7, 67, 70, 71* (Virgatosphinctoides) elegans Zone 9-10, 66, 67, 71 scitulus Zone 9, 67, 68, 71* wheatleyensis Zone 8-9, 67, 69, 71 Perisphinctes pallasianus Zone 18, 67, 70 Subplanites grandis Zone 67 ? vimineus Zone 67, 69 wheatleyensis Zone 67 Virgatites miatschkovensis Zone 18, 67, 69 nodiferus Zone 67 wheatleyensis Zone 67, 69 Kloucekia 86, 88, 90, 113 phillipsii 91, 113, 114 phillipsui euroa 91, 113, 114 ; Pl. 6, fig. ro ; PT 7p gs i310 7,1 O ne Laevicyphomena 316, 317 Lasiograptus 89, 91 Lennea 160 Lepidocoleus 89, 92 Lepidotus 10 Leptaena 287, 299, 300-302*, 304-305, 307, 310-11, 315 Associations 301, 308, 313 Distribution and ecology 299, 301, 305, 313 Groups in British Llandovery 301, 302, 310 Ordovician and Silurian spp. 300-301 Relationships 301, 302, 310, 313 Leptaena acuteplicata 301, 302 bella 301 centervillensis 301 contermina 288, 301, 302, 306, 307 ; Pl 6, figs. 8-13 ; Pl. 7, figs 1-11 delicata 301 depressa 315 var. vulgaris 300 elongata 300, 305 haverfordensis 288, 300, 302-3, 304, 305, 307 ; Pl. 5, figs. 4-15 var. contvacta 300, 304, 305 homostriata 315 julia 301 lovenit 289, 301 martini 302, 303 martinensis 288, 302, 303, 304 ; Pl. 4, figs. 9-13 ; Pl. 5, figs. 1-3 oklahomensis 301% parvula 289, 301 purpurea 288, 302, 313, 314, 315; Pl. 12, figs. 1-6 cf. purpurea Pl. 12, fig. 6 quadrata 288, 291, 300, 302, 307, 312, 313, 314; Pl. 11, figs. 6-10 quadrilatera 300 reedi 288, 301, 302, 308, 310, 311 ; Pl. 10, figs. I-14 vhomboidalis 299 var. B 300 var. y 300 var. 6 300, 309 var. € 300, 307, 310 var. € 309 var. nana 300 vichmondensis 300 var. precursor 300 vYUgOSA 299, 300 salopiensis 287 schmidti 300 sinuosus 289, 301 ? tennesseensis 301 tenuistriata 300 urbana 300, 302, 305, 306-7 ; Pl. 6, figs. 6, 7 valentia 288, 300-302, 307, 308, 310-11; Pl. 8, figs. 1-8 mullochensis 300, 302, 305, 308, 309 ; Pl. 8, figs. 9-15 valida 288, 300, 302, 305, 307 ; Pl. 6, figs. 1-5 Leptaena wisgoriensis 301, 316 zeta 288, 300, 301, 302, 309, 310 ; Pl. 9, figs. 1-6 ziegleri 288, 301-2, 311, 312 ; Pl. 11, figs. 1-5 sp. 314, 315 ; Pl. 12, figs. 7-8 sp. (large Woolhope Limestone specimens) 310, 315 ? Leptaena lewisii 289 Leptaenidae 286-7, 289 leptaenids 286-7, 289, 299, 301, 314, 319 Leptaeninae, (Strophomenidae) 287-89, 294, 299 leptaeninid 319, 321 Leptaenisca 287 Leptaenoidea 287 Leptaenoideinae 286, 287 Leptagonia 300 Lingula sp. 8, 9 ovalis 8, 9, 10, 69 Lithacoceras 5, 19, 23-4, 72, 75 Lithodendron caespitosum 258, 259, 266 Lithostvotion 211-2 antiquum 266 hennahi 214 cf. portlocki 194 Lloydolithus 108 Lucina miniscula 8-10 Luhaia 287 Lummaton Hill, Middle Devonian, Devon 186, 187, 201 Lummaton Shell Bed 187-8 Macgeea 206, 209, 258-60, 268 Macgeea (Macgeea) 258-60 caespitosa 266 Macgeea (Thamnophyllum) 257-60, 271 caespitosa 266 INDEX 331 var. minus 261. 263 caespitosum 266 var. minus 263 minima 261, 263 trigemina trigemina 260 Macgeeidae 207, 209 Macgeeinae 207 Mackerrovia 299, 319 lobatus 288, 319, 320-21 ; Pl. 13, figs. 10-15 ; Pl. 14, figs 1-8 macroconchs, Ammonoidea see under Sexual dimorphism Madrepora ananas 212 Marisastridae 208 Marisastrum 232 Marrolithus anomalis 95 Marvrolithoides 90, 92, 95, 96, 101 arcuatus 101 laticirrus 88, 99, roo-1, 109 ; Pl. 2, figs. 1, 3, 5,9, 11, 13 orthogonus 91, 96, 97-101 ; Pl. 1, figs. 1-9 simplex 101 sp. 88,101, 102 ; Pl. 4, fig. ro Marvolithus 95, 101 Medusaephyllum 209, 211 Megaphyllum 206 microconchs, Ammonoidea refer to Sexual dimorphism Microtrypa 294 MIOCENE, trace fossils Austria 131 Borneo 137 Spain 150-51 Modiola autissiodorensis 9 MoLiusca Kimmeridgian, Great Britain 10 Ordovician, Turkey 92 Necrocarcinus 162 Neocampophyllidae 206 Neocolumnaria 206 Neocolumnariidae 206, 208 Neseuretinus 115 Neseuretus 115, 117, 118 biymanicus 117 Neseuretus (Neseuretus) 92, 117 biymanicus 92, 117-118 turcicus 85, 88, 91, 115, 116-7 ; Pl. 7, figs. 8, 10, 11 ; Pl. 9, figs. 1-4 Oepikinae 286 Onnia 108 ornatus 109 Ophiomorpha 136-7, 151, 161 nodosa 136 Opthalmosaurus sp. 9, 10 ORDOVICIAN Brachiopoda 299-300, 315, 321 Caradoc Series 88, 91-2, 315 Faunas 91-2 Anglo-Welsh 92 Bohemian affinities 91-5, 108-9 Encrinurella fauna 92 Tethyan 92 Llandeilo 91-2, 107 Llanvirn 92, 107 North America, Brachiopoda 315, 321 Stratigraphy 92 Trilobita 91-2 Turkey 83-4, 85, 86-90 Orvionastraea 212 Orthis antiquata 293 scabrosa 293 Ostrea bononinae 7-9, 11 multifoymis 8-10 solitavia 7, 11 Oxford area, Upper Kimmeridge 70, 71*, 72 oysters 16 Pachyphyllinae 206 Pachyphyllum 205-7, 209, 211, 213-14, 280-81 bouchardi 214, 281 devoniense 226, 228 ? Pachyphyllum bowerbanki 254 PALAEOBOTANY Ferns, Tempskya 169-179 PALAEOECOLOGY Ammonoidea, Kimmeridge 16 Devonian, Corals environment 185 growth position 198 influences on variation in Phillipsastraeidae 201 Lower Chalk bottom conditions 129 burrows 130-150 fauna 161-62 trace fossils 130-32, 137, 150, 153 Oysters 16 Silurian Strophomenacea (Brachiopoda) 288— 301 PALAEONTOLOGY see under separate Phylla Collecting techniques 11 Paradoxica Bed, trace fossils 142, 144-47 Parallelodon 11 Payravirgatites 63-4 kimmeridgensis 64 paravirgatus 63 Pavlovia 63, 70, 75 (Paravirgatites) 63 paravirgatus 7 cf. paravirgatus 63, 64 “pavlovids’ 22 Pectinatites 14, 15-18, 19, 20-24, 39, 60, 64-66, 68, 75-6 Evolution of 64-66, 68 Interpretation of 18 Origin of 22—24 332 INDEX Pectinatites aulacophorus 60-61 pectinaius 21, 63 Pectinatites (Arkellites) 8,9, 18, 24, 68 cuddlensis 9, 25, 26, 27-29, 37, 65, 68 ; Pl. 4; Pl. 5, fig.1 damoni 9, 25, 28, 29, 65 ; Pl. 5, figs. 2, 3 ; Pl. 6 hudlestoni 8, 24, 25, 29, 30, 64, 65, 69, 70 ; IAL 2, ites 3} 8 IAL 7 8 JeMs fh, iver, primitivus 9, 24, 25*, 26, 28-9, 33, 64-5, 68 ; IEE A, eS, ui, 2 G8 Vell, 3} cf. primitivus 10 sp. indet. 7 Pectinatites (Pectinatites) 18, 59, 60, 66 cornutifer 7, 62, 63, 65, 70 ; Pl. 25, fig. 3 ; Pl. 26, fig. 2 eastlecottensis 7, 60, 61, 65, 70 ; Pl. 26, fig. 1 cf. eastlecottensis 7 groenlandicus 7, 65 ; Pl. 31 cf. groenlandicus 61, 62 inconsuetus 7, 19, 59, 60, 65, 75 ; Pl. 30 naso 7, 62, 63, 65, 70 ; Pl. 32 proboscide 72 Pectinatites (Kevatinites?) groenlandicus 61 Pectinatites (Virgatosphinctoides) 18, 65, 66 abbreviatus 8, 40, 54, 55, 65 ; Pl. 26, fig. 3 clavelli 9, 39, 40-1, 65, 69 ; Pl. 14 decorosus 9, 32, 36, 37, 65 ; Pl. 12 donovani 8, 51, 55, 56, 64-5, 70 ; Pl. 25, figs. 1&2 elegans 9, 31, 32-34, 64-6, 68 ; Pl. 8, figs. ra, 1b; Pl.9 elegans corniger 9, 33, 34, 36, 64-5, 68 ; PI. nite) encombens 8, 40, 57, 58-59, 65-6, 70 ; Pl. 27, fig. r ; Pl. 28 grandis 8. 9. 38, 44, 45, 65, 69, 75 ; Pl. 15, fig. 3; Pl. 18 grandis acceleratus 8, 45, 65 ; Pl. 19 laticostatus 8-9, 38, 43, 44, 65, 69 ; Pl. 16 magnimasculus 8, 40, 56, 57, 65, 70 ; Pl. 29 major 9, 37, 38-9, 65 ; Pl. 13 cf. major 9 pseudoscruposus 19, 38, 49, 50, 65, 69 ; Pl. 17 cf. pseudoscruposus 8 reisiformis 8, 50, 51-2, 54, 59, 65, 69 75 ; Pl. 23, fig. 3 cf. veisiformis 8, 51 reisiformis densicostatus 8, 53, 65; Pl. 23, figs. 1, 2 ; Pl. 24, fig. 2 scitulus 9, 32, 34, 35-37, 41, 65, 69 ; Pl. 11 cf. scitulus 9 smedmorensis 9, 40, 41, 42, 65, 69 ; Pl. 15, figs. 1&2 wheatleyensis 8, 40, 46, 47-49, 52, 56, 65, 69 ; IPM, Zain wheatleyensis delicatulus 8, 48, 49, 61, 65, 69 ; Pl. 27, fig. 2 wheatleyensis minor 9, 47, 48, 55, 65 ; Pl. 24, fig. I woodwardi 8, 32, 43, 45, 46, 64, 65, 69 ; Pl. 20 Pectinifoymites 20, 21 bivius 20 ? Pectiniformites 59 Peneckiella 189, 191, 206, 209-10, 271, 272-3 achanaiensis 274 boreensis 275 lateseptata 273, 274 mesa 273, 275 MINOY 272, 273 minor kuntht 273, 275 minor minor 274-5 ; Pl. 17, figs. 4 & 5 nalivkini 274 salternensis 190, 193-96, 201-2, 269-70, 273, 274-75 ; Pl. 18, figs. 1-4 Peneckiellidae 206, 208 Peneckiellinae 207 Pentamerus community (Silurian, Llandovery) 288 Pentlandina 288, 289, 291, 294, 301, 316 loveni 316 parva 288, 291, 293, 313 ; Pl. 1, figs. 7, 8 cf. parva 291 parabola 288, 289, 291, 292, 293 ; Pl. 1, figs. 9-12 tarvtana 288, 289, 290-91, 293 ; Pl. 1, figs. 1-6 sp. 293 ; Pl. 1, fig. 13 Perisphinctidae 12 Pevisphinctes eastlecottensis 60 Pexiphyllidae 208 Pexiphyllum 209 Phacelophyllum 257 Phacellophyllidae 209 Phacellophyllinae 206, 207 Phacellophyllum 257-60, 272 Phacellophyllum caespitosum 258, 266 Phacellophyllum (Phacellophyllum) 257, 271% Phacellophyllum (Thamnophyllum) 257 Phacops phillipsii 114 proaevus 112 Phillipsastvaea bowerbanki 236, 240, 254, 257 goldfussi 248 limitata 248 pentagona 233, 248, 253 pentagona var. micrommata 189, 240, 242 var. minima 231, 236 sanctacrucensis 231 Phillipsastraeacea 207 Phillipsastraeidae 190-205, 280 classification 184 colonial 193-97 increase in, 193, 194-97 microstructure of, 190, 191-93 phylogenetic relationships 207-9, 232 systematics of, 205, 206—209 variation in, 198, 199-205 phillipsastraeids 280 Phillipsastraeinae 207 Phillipsastvea 184, 191, 195, 203, 205-11, 212, 213-21, 227-32, 280-1 INDEX 333 ananas 189, 195, 213, 228, 229, 231, 248, 253; PI 5; figs: 1-4 bouchardi 227 cantabrica 214 chenouensis 213 devoniensis 186, 195, 213, 226, 227-29 ; Pl. 4, figs 1-4 hennahi 187-8, 207, 213-15, 224-25, 227, 229, 232, 280-81 hennahi hennahi 187-8, 191*, 192* 195, 201, 202, 214, 215-21, 224-26, 229, 281 ; Pl. 1, figs. 1-6 ; Pl. 2, figs. 1-4 hennahi ussheri 189, 195, 202, 205, 221, 222*— 25*, 226, 229, 281 ; Pl. 3, figs. 1-3 hennahii 214, 215 ibergensis 213, 227, 228 macrommata 229, 231 pentagona var. micrommata 240-43 pentagona 233, 240, 248 vadiata 206 rozkowskae 189, 195, 229, 230, 231-32 ; Pl. 6, figs. 1-4 smithi 231 ‘ Phillipsastrea cantabrica ’ 220 pentagona 194 Phillipsastvea (Pachyphyllum) 211 devoniense 226 phobotactic behaviour 149 Pholeus 156 abomasiformis 156 Pisces, Kimmeridgian 10 Placoparina 115 Platycoryphe 120 ? sp. 88, 120 ; Pl. 8, fig. 4 Plumites sp. 89, 91, 92 Plenus Marls 128, 154, 155 burrows in Pl. 5, fig. 4; Pl. 6, fig. 2; Pl. 7, fig. 3 POLAND Coelenterates, Devonian 203—4 POLYCHAETES tube systems 158 PORTLANDIAN 74 Prismatophyllum 205, 231 pentagona 231, 233 prisma 232 Problematicum sp. 154 Producta depressa 300 Protocallianassa 132 antiquua 137 Protocavdia morinica 7-10 Protomacgeea 209 Pseudoacervularia 209, 211, 213 ananas 228 voemert 215 Pseudobilobite 153 Pseudobilobites 153, 154-5 “« Pseudobilobites ’’ 153 Pseudobilobites jefferiesi 153, 154, 155 ; Pl. 6, fig. t ; Pl. 7, fig. 3 ; Pl. 8, fig. 4 ; Pl. 9, figs, 3, Hig, (8) Pseudovirgatites 19, 20, 23 60, 75 Pseudoblothrophyllum helderbergium 205 Rafinesquinidae 287 Rafinesquininae 286 Ramsleigh Quarry, Devon (Upper Devonian) 186*, 188, 189, 201 Raphiophoridae 93 Red Chalk, trace fossils 144-45, 147 Redonia sp. 91-2 REpTILIA, Kimmeridge 10 Rhizocovallium 150-51, 161 glaseli 151 gldseli 151 “ Rhynchonella ”’ cuboides 188 Ribeiria sp, 89, 91-2 Rogerella 161 Saccoma 8, to Saltern Cove, Devon (Upper Devonian) 186*, 189 Schizocrania sp. 89 Schluteria 206 scratch marks I51, 153, 155, 156 ScruTTon, C. T. 181-281 Sedimentation Lower Chalk 128-9 Selenopeltis 121 buchi 91, 121 ineymis 121 ineymis angusticeps 86, 91, 121 ; Pl. ro, figs. itis, Zh5 Gy Fy (2) ineymis ineymis QI, 121 Sexual dimorphism, Cephalopoda criteria 15 evidence 16-17 reasons 17-18 terminology 15 Shaleria 319 Sheppey, Kent (Eocene) 171, 178 Shropshire Silurian, Brachiopoda 288—298, 301, 307, 314-5 SILURIAN Brachiopoda 283-324 Great Britain communities 288, 313 Llandovery 286, 288, 291, 293-4, 298-302* 305, 310, 316, 321 strophomenids 311 Wenlock 286, 307 Trilobita 304 Sinuites (s.l.) sp. 89, 91-2 pavadoxica 145, 147 Siphonia pyriformis 145 tulipa 144-5 Siphonophrentis variabilis 205 Smithia 209, 211, 231 bowerbanki 231, 253, 254, 257 hennahii 214, 215 micrommata 231, 240-43 ? Smithia boloniensis 231 334 INDEX Sosink Formation 89, 90 scotica var. alveata 294, 296-7 SPAIN woodlandensis 295 Trace fossils, Miocene 150 aff. woodlandensis 295 Palaeozoic 153 woodlandensis geniculata 294 Sphinctoceras 22, 69 Strophomena (Pentlandina) 289 CYaSSUM 22 parva 289, 291 “ Sponges ” 131-2, 136, 150-2, 161 tartana 289 Spongelia 150 ? Strophomena sibirica 294 Spongeliomorpha 141, 147, 150, 151, 156, 161 Strophomenacea 283-324 associations 151 classification 286, 287 branching patterns 151 distinguishing features feeding 153 inter area 311 internal structure 153 muscle scars 301, 306, 310-11, 313, 319 interpretations 150-53 ornament 296, 315-18, 321 occurrence 150-151 Tugae/rugosity 287, 293, 304, 306-7, 309, ornamentation 151, 153 315-16 outer surfaces 151, 153 Strophomenidae 286, 287, 288, 294, 319 surfaces ridges 151, 153 Strophomenidina 287 Spongeliomorpha ? annulatum 152, 153, 157* ; Strophomenidinae 287 JEN Ae ity oe LEM, Ey, tikes 5 strophomenids 286, 311, 315 ibevica 150-52 Strophomeninae 286-89, 294 saporvtai 151 strophomeninid 316, 319 Spelo2i we leagetione Strophonella 298 “ Spongeliomorpha ’ iberica 151 costatula 294 Spongelites 151 penkillensis 297 Spongia pavadoxica 142, 144, 145, 147 Subdichotomoceras 22 pertusa 132 lamplughi 22 sudolica 147, 151 Subplanites 5, 18, 20, 21, 23-4, 75 Spongiliomorpha 150 moernsheimensis 23 Spongites 132 pseudoscruposus 49 gigas 134 vest 23 pertusus 132 vyueppellianus 23 SaxONOCUS 134, 135*, 136-7 schlossevi 23 suevicus 140 siliceus 75 suevicus quenstedti 140 (Virgatosphinctoides) wheatleyensis 46 ? Streptastvea 209 Sudetia 272-3 longivadiata 215 Sulcorphyllum 210, 214 Stricklandia 286 Svobodana 88, 90-2 Stvicklandia community (Silurian, Llandovery) Swindon area, Kimmeridge Clay 70, 71*, 72 288 Synatophyllum 206-7 Stringophyllum 186 Synhomalensis biyrmanica 117 Stropheodonta funiculata 317 Synhomalonotidae 115 stropheodontid 319 Syvingophyllum 212 Stropheodontidae 286, 287, 319 cantabricum 220 “ Stvophomena’ agrestis 297 ? cantabricum 214-15, 220 antiquata 286, 289-91 Strophomena 288-9 antiquata 295-7 Taonurus 151 antiquata var. woodlandensis 293 ultimus 151 avenacea 319 Teichichnus 139 dura 293 Tempskya 171, 176, 177 hivundo 289 evosa 171, 178 julia 316 gvandis 171, 173, 177-8 lindstvomi 294 knowltoni 175 ? pectenoides 294 vossica 174 cf. penkillensis 291 superba 173-4, 178 vadiwveticulata 294 wesselit 174 vhomboidalis 306, 309 sp. nov. [= Kent Tempskya] 171, 172-79 ; rugata 294 Pls. 1-12 scotica 294, 296 affinities of, 176-78 INDEX 335 origins of, 177-78 siliceous preservation 178-9 structure of ; “false ’ stem 172, 174, 176 ; Pl. 1 leaf gaps 173-5 ; Pls. 5-7, 9 leaf traces 174, 175, 178 ; Pls. 1-9 meristeles 172, 174-5, 178 ; Pls. 4,7, & 8 petioles 172 ; Pls. 1 & 2 ramentae 172-74 roots 174, 176-7; Pls. 2 & 3 scales 174 ; Pls. 2&7 steles 172-5 ; Pls. 3, 4, 8, & 10 stem 172, 173, 174-8 ; Pls. 5-7, & 9 tissues endodermis 173-4; Pls. 11 & 12 epidermis P]. 12 inner cortex 173, 177 ; Pl. 12 parenchyma 173-8, Pl. 1o phloem 173, 176 sclerenchyma 172-78 ; Pls. 5, 7, 10, 11 Kylemi173> 074, £70,177 ; Pls. ro& rr Tempskyaceae 176 Terebella lewesiensis 155, 160 “ Terebella’ 155, 156 cancellata 131, 155, 156, 160, 161 ; Pl. 8, figs. 1 & 2 harefieldensis 131, 156 ; Pl. 7, fig. 2 lewesiensis 161 terebellids 131 Teredina amphisbaena 129 TERTIARY Tempskya 178 Trace fossils, Miocene 131, 137, 150-51 Thalassinoides 131, 132, 134, 147, 151, 161, 162 Thalassinoides associations 132 branching 131, 136, 142, 147 burrows 137-8, 147-8 diagnostic features 132 interpretations 136-37, 139-41 laminated structures 138*, 139,; Pl. 8, fig. 3 mounds 136 occurrence 132, 137, 140-41, 144-45, 147 ornamentation 140-41 outer surface 136-37, 141, 143 pellets 137-8 protuberances 142 systems 133, 135, 142, 143, 146-47 tunnels 140-42, 148-9 “turn-arounds ’ 136-7, 141 walls 147, 149 Thalassinoides callianassae 131% ornatus 138, 141, 151 ; Pl. 6, fig. 4 ; Pl. 7, fig. 6 pavadoxica 142, 143*, 144—46*, 147, 151, 158 ; Pies sel oye. 53; Elo, tig. 2 saxonicus 133*, 134, 135*, 136-40 ; Pl. 1, fig. 1 ; Pl. 5, figs. 2 & 3 ; Pl. 6, figs. 3 & 4 suevicus 140 cf. suevicus 140-41 ; Pl. 1, fig. 2 visurgae 135*, 140 SP. 133*, 135*, 146*, 157* Thamnophyllidae 207-8 thamnophyllids 203-4 Thamnophyllum 185, 187, 191, 196, 206, 209, 257, 258-71, 273 caespitosum s.1. 186, 193-4, 196, 204, 266, 267, 270-1 ; Pl. 15, figs. 2-4 ; Pl. 16, figs. 1-2 caespitosum caespitosum 204, 268, 271 caespitosum paucitabulatum 187, 193, 196*, 201, 202, 204, 267, 268-71 ; Pl. 15, fig. x ; Pl. 16, figs. 3-7 ; Pl. 17, figs. 1-3 germanicum group 265-6, 271 germanicum germanicum 204, 258, 260, 261-5 germamcum kozlowskii 265 germanicum pajchelae 204, 262, 264-5 germanicum schouppei 185, 193, 196-97*, 198, 201-5, 261, 262-6 ; Pl. 13, figs. 1-4 ; Pl. 14, figs. I-4 germanicum skalense 204, 262, 264-5 germanicum superius 265 hornesi 266 Rozlowskit 204, 265 Rozlowskii superius 265 monozonatum 266 stachei 258-60 Thamnophyllum superius 204 cf. trigeminum 261 trigeminum 258, 260-1 trigeminum trigeminum 260-1 sp. 271 Thamnopora 188 Thrissops 9-10 Tithonian, Germany 5, 73-5 Totternhoe Stone, trace fossils 128-9, 137, 140-1, 149-50, 152 ; Pl. 1, fig. 1 TRACE FOSSILS 125-167 see also under Chondyrites, Thalassinoides, Spongeliomorpha, Pseudobilobites, Terebella Burrows and Borings. associations I3I—2, 137 associated with hard grounds 147-8 Feeding 138, 150, 153, 155 fossil records, Great Britain 132-34 Interpretations 136-37, 140, 144, 147-53, 155-6 Jefferies Collection 131, 154 Kennedy Collection 131 Lower Chalk 125-167 Nomenclature 137 ornamentation 140-41, I51 surface traces 130, 155 Trapezophyllum 206, 209, 214 Trematis ? sp. 89 Tretaspis 304 TRILOBITA Ordovician 91-2 Anglo-Welsh faunas 92, 101, 107-8 Bohemian faunas 91, 95, 108-9 Turkey 101, 107, 109, IIT, 114 Turkey 83-120 336 TRIAS Trace fossils Keuper, Dorset 132 Muschelkalk, Germany 140, 156 Trigonia pellati 9, 11 Trinucleidae 95 Trinucleus bureaui 101 goldfussi 109 ornatus 109 ultimus 109 Triplesiidina 287 Tryplasma fascicularia 203 “tubulures ’ 148 TURKEY 83-120 Palaeontology Brachipoda 88, 90 Graptolites 92 Trilobita 91-120 Stratigraphy Cambrian 84-5 Ordovician 85, 91-2 Palaeozoic 84 Bedinan Formation 85, 86-8, 91 Dadas Formation 88 Sosink Formation 89, 90 S.E. Turkey 84*, 90 Bedinan 84, 85, 86*, 87-8 Derik 85 Mardin 85 Sosink 85-6, 89, 90*, g1—2 Ziyaret 89-90 Urechis 130, 158 WeSsAS Brachiopoda, Ordovician 315, 321 Tempskya 177 Wyoming, Upper Cretaceous 171, 177 INDEX VERMES Annelids 151 Arenicolites 158 Chondrites 148-150, 161 fossil worm burrows 158, 160 polychaete burrows 158 Urechis 130, 158 Virgatites 5, 18 miatschkovensis 18 virgatus 18 Virgatosphinctes reisi 20 Virgatosphinctinae 24 Virgatosphinctoides 5, 18, 20, 21, 22, 26, 30 , 31, 32*, 33-37, 38*, 39, 40%, 41-50, 51*, 52-57, 64, 65*, 66, 70 grandis 44 nodiferus 44 wheatleyensis 21, 30, 46 Vomacispongites 132 Wealden Beds 171, 178 Wedekindella brilonense 188 Wheatleyites 20, 59 eastlecottensis 60 tricostulatus 20 “ Wheatleyites ’ veductus 62 Wolborough Quarry, Devon (Mid.-Devonian) 185, 186*, 188 Woolwich Beds 171, 179 Xenohelix saxonica 137 Yorkshire area, Kimmeridge Clay 72 Zapfella 161 Zaraiskites 75 “ Zoophytes ’ 131 hb, Tae hgh 4 Py fade tone Cie On a be , | PRINTED IN BY ADLARD & son RESS, by 2 = ee 7 iairinesseee tres sy