ORDOVICIAN BRYOZOA FROM THE LLANDEILO LIMESTONE 
DESCRIPTION. Zoaria are reticulate and anastomosing, only frag- 
mentary specimens have been found at Clog-y-fran. No exterior 
frontal views of the colonies are available because frontal surfaces 
are all embedded in sediment. 
Fenestrules are oval, with diameters averaging 0.78 mm by 1.67 
mm. Branches are rounded and average 0.48 mm diameter. The 
reverse side of the colony is striated. 
The exozone is distinguished by a change in the orientation of the 
autozooecia and a thickening of the zooecial walls. Rounded zooecial 
apertures are present on the frontal side of the colony. The apertures 
average 0.09 mm by 0.12 mm in diameter in the exozone. Three to 
four zooecial rows occur on each branch. 
Zooecial walls are thin and straight. Occasional basal diaphragms 
have been observed which are deflected orally at their junction with 
the zooecial walls and in some cases have laminae continuous with 
the zooecial linings. 
The microstructure is laminar, although hard to distinguish. Pos- 
sible acanthostyle-like structures are present. 
REMARKS. The specimen from Clog-y-fran is fragmentary and 
embedded in sediment, which makes identification difficult. It is 
characterised by rounded branches and oval fenestrules. Zooecial 
walls are straight in the endozone, becoming thickened in the 
exozone. Zooecial apertures are rounded and three to four rows 
occur on each branch. Occasional diaphragms are present and 
acanthostyle-like structures have been recognised. 
Phylloporina hillistensis, described from Estonia by Lavrentjeva 
(1985: pl. ii, fig. 2), has similar thick straight endozonal walls and 
occasional diaphragms but differs from the Clog-y-fran specimen in 
having more abundant zooecia per branch and lacking striae on the 
reverse of the colony. 
ACKNOWLEDGEMENTS. I would like to thank Dr. P.D. Taylor and Dr. 
J.C.W. Cope for supervising this project, which was carried out under the 
tenure of a Natural Environment Research Council Studentship. I am grateful 
to Dr. D.H. Evans and Mr. F. Cross for assistance in the field. I would also like 
to thank Mrs D.G. Evans for drafting Table | and Fig. 1, and Mrs L. Weaver 
for re-typing the manuscript. 
REFERENCES 
Astrova, G.G. 1965. Morfologiiya, istoria razvitiya i sistema ordovikskikh1 siluriiskikh 
mshanok. Trudy Paleontologicheskogo Instituta Akademiya Nauk SSSR, Moscow, 
106: 432 pp, 84 pls (In Russian). 
1978. Istoriya razvitiya, sistema i filogeniya mshanok, Otryad Trepostomata. 
Trudy Paleontologicheskogo Instituta Akademiya Nauk SSSR, Moscow, 169; 240 
pp.. 46 pls (In Russian: Engl. transl. by D.A. Brown, 307 pp, no pls.). 
— & Morozova, IP. 1956. K sistematike mshanok otryada Cryptostomata. Doklady 
Akademii Nauk Soyuza Sovetskikh Sotsialisticheskikh Republik. St Petersburg, 110: 
661-664 (In Russian). 
Bassler, R.S. 1911.The Early Paleozoic Bryozoa of the Baltic Provinces, Bulletin of the 
United States National Museum, Washington, 77: 11-137. 
1928. Bryozoa. Jn, Twenhofel, W.H., Geology of Anticosti Island, Memoirs of the 
Geological Survey of Canada, Ottawa, 154: 143-168. 
Bekker, H. 1921. The kukers stage of the Ordovician rocks of N.E. Estonia. Acta et 
Commentations Universitatis Tartuensis, Dortpat, A2: 92 pp. 
Bengston, P. 1988. Open nomenclature. Palaeontology, London, 31: 223-227. 
Boardman, R.S. 1960. A revision of the Ordovician bryozoan genera Batostoma, 
Anaphragma and Amplexopora. Smithsonian Miscellaneous Collections, Washing- 
ton, 140: 28 pp. 
, Cheetham, A.H., Blake, D.B., Utgaard, J., Karklins, O.L., Cook, P.L., 
Sandberg, P.A., Lutaud, G. & Wood, T.S. 1983. Bryozoa (revised). Jn, Robison, 
R.A. (ed), Treatise on Invertebrate Paleontology, G (1): 625 pp, Boulder, Colorado 
and Lawrence, Kansas. 
Borg, F. 1926. Studies on recent Cyclostomous Bryozoa. Zoologiska Bidrag fran 
Uppsala, 10: 181-507. 
133 
Bork, K.B. & Perry, T.G. 1968. Bryozoa (Ectoprocta) of Champlainian age (Middle 
Ordovician) from northwestern Illinois and adjacent parts of Iowa and Wisconsin. 
Part II, Homotrypa, Orbignyella, Prasopora, Monticulipora and Cyphotrypa. Jour- 
nal of Paleontology, Menasha, 42: 1042-1065, pls 133-138. 
Brown, G.D. 1965. Trepostomatous Bryozoa from the Logana and Jessamine Lime- 
stone (Middle Ordovician) of the Kentucky Bluegrass region. Journal of Palaeontology, 
Tulsa, 39: 974-1006. 
& Daly, E.J. 1985. Trepostome Bryozoa from the Dillsboro Formation 
(Cincinnatian Series) of south-eastern Indiana. Special report of the Geological 
Survey of Indiana. Bloomington, 33: 1-95. 
Buttler, C.J. 1988. Studies on Ordovician bryozoans from Wales and the Welsh 
Borderland. Ph.D. thesis. University of Wales (unpublished). 
1991a. Bryozoans from the Llanbedrog Mudstones (Caradoc), north Wales. 
Bulletin of British Museum of Natural History (Geology Series), London, 47: 153- 
168. 
1991b. Studies on Ordovician bryozoan fauna from the Slade and Redhill Beds, 
South Wales. Palaeontology, London, 34: 77-108. 
Coryell, H.N. 1921. Bryozoan faunas of the Stones River Group of central Tennessee. 
Proceedings of the Indiana Academy of Sciences, Brookville, 1919: 261—340, 14 pls. 
Cummings, E.R. 1908. The Stratigraphy and Palaeontology of the Cincinnati Series of 
Indiana. Annual Report. Indiana Department of Geology and Natural Resources, 
Indianapolis, 32 (for 1907): 605-1188, 55 pls. 
Dreyfuss, M. 1948. Contribution a l’etude geologique et paleontologique de 
!’Ordovicien superieur de la Montagne Noir. Memoires de le Societe Geologique de 
France. Paleontologie, Paris, 58: 63 pp. 
Dybowski, W. 1877. Die Chaetetiden der ostbaltischen Silurformation. Verhandlungen 
der Russisch-Kaiserlichen Mineralogischen Gesellschaft zu St. Petersburg, St. 
Petersburg, 14: 1-134. 
Ehrenberg. C.G. 1831. /n, Hemprich, FG. & Ehrenberg, C.G., Symbolae physicae, seu 
icones et descriptiones animalium evertebratorum. 4 (Evertebrate 1). 126 pp., 10 pls. 
(1828), Stockholm. 
Eichwald, E. 1856. Beitrag zur geographischen Verbeitung der fossilenThiere Russland. 
Bulletin de la Societe Imperiale de Naturalistes de Moscou. Moscow, 29: 91-96. 
— 1860. Lethaea rossica ou Paleontologie de la Russie. Ancienne Periode. Stuttgart, 
1: 355-419, 434-435, 450-452, 475495. 
Elias, R.J. & Condra, G.E. 1957. Fenestella from the Permian of West Texas, Memoirs 
of the Geological Society of America, Washington, 70: 158 pp. 
Foerste, A.F. 1887. The Clinton Group of Ohio, Pt.UI, Bulletin of the Scientific 
Laboratories of Denison University, Granville, Ohio, 2: 140-176. 
Foord, A.N. 1883. Contribution to the micropalaeontology of the Cambro-Silurian 
rocks of Canada. Geological and Natural History Survey, Canada, Ottawa, 26 pp. 
Fortey, R.A., Harper, D.A.T., Ingham, J.K., Owen, A.W. & Rushton, A.W.A. 1995. 
A revision of the Ordovician series and stages from the historical type area. 
Geological Magazine, 132: 15-30. 
James, J.F. 1893. Manual of the palaeontology of the Cincinnati Group. Journal of the 
Cincinnati Society of Natural History, Cincinnati, 15: 144-159. 
Karklins, O. 1983. Ptilodichtyoid Cryptostomata Bryozoa from the Middle and Upper 
Ordovician rocks of Central Kentucky. Journal of Paleontology, Tulsa, 57: (Memoir 
14); 1-31. 
1984. Trepostomate and cystoporate bryozoans from the Lexington Limestone 
and Clays Ferry Formation (Middle and Upper Ordovician) of Kentucky. Profes- 
sional Paper, United States Geological survey, Washington, 1066-1: 105 pp. 
Lavrentjeva, V.D. 1979. Novii portirad paleozoishich mshanok. Paleontologicheskii 
Zhurnal, Moscow, 9-68. (In Russian). 
— 1985. Mshanki Podotryada Phylloporinina. Trudy Paleontologicheskogo Insti- 
tute. Akademiya Nauk SSSR. Moscow, 214: 102 pp. 
Miller, S.A. 1889. North American Geology and Palaeontology, Western Methodist 
Book Concern, Cincinnati, 664 pp. 
Modzalevskaya, E.A. 1953. Trepostomaty Ordovika Pribaltiki i ikh stratigragicheskoe 
znachenie. Trudy Veseouznogo Neftyanogo Nauchno-Issledovatel ‘skogo Geologo- 
Razvedochnogo Instituta, (VNIGRI), Leningrad & Moscow, Y 78: 91-167, 14pls (In 
Russian). 
Nekhorsoheva, L.V. 1970. (Ordovician bryozoans from the north of Pai-khoi, Vaigach, 
and the south of Novaya Zemlya). In, Bondarev, V.I. (ed.), Opornyi razrez Ordovika 
Pai-khoya, Vaigacha i yugo Novoi Zemli: 63-95, 9 pls. Leningrad, Izd-vo NIIGA, (In 
Russian). 
Nicholson, H.A. 1879. On the Structure and Affinities of the ‘Tabulate Corals’ of the 
Palaeozoic Period with Critical Descriptions of Illustrative Species. 342 pp, Edin- 
burgh. 
Orbigny, A, d’ 1850. Prodrome de paleontologie stratigraphique universelle. 1: 394 
pp-, Paris. 
Owen, DE. 1962. Ludlovian Bryozoa from the Ludlow District. Palaeontology, 
London, 5: 195-212. 
1965. Silurian Polyzoa from Benthall Edge, Shropshire. Bulletin of the British 
Museum of Natural History (Geology), London, 10: 95-117. 
1969. Wenlockian Bryozoa from Dudley, Niagara and Gotland and their 
palaeogeographic implications. Palaeontology, London, 12: 621-636. 
Pushkin, V.I. 1976. Novye vidy mshank iz Ordovika i Silura brestskoi vpadiny. V Kn.: 
