MOKRIS— BRITISH FOSSILS. 



237 



Sedgwick, noticed in the last section, are considered to form the base 

 of the Upper Silurian series, not only by their fossil contents, but it 

 being difficult to draw any well-defined line between them and the 

 overlying Wcnlock beds — thus constituting, with the Lower Llan- 

 dovery, an intermediate zone between the underlying and overlying 

 Silurian rocks. 



The fossils of this group are nearly all marine, and belong chiefly to 

 the Invertebrata ; the Vertelrata being represented by a few remains 

 of fishes (Placoid), and those found in the uppermost beds of the 

 scries. On the other hand, the Invertebrata are fully represented ; of 

 the Zoophytes there are many genera and species of the four-starred 

 corals ; of the Crustacea, many Trilobites, and some higher forms, as 

 the Pterygotus and allies in the Upper Ludlow ; of Mollusca, numerous 

 species of Cephalopoda, Erachiopoda, Lamellibranchiata, and Holo- 

 stomatous Gasteropods ; of the Echinodernata. are many crinoids and 

 some star-fishes ; of the Annelida, are remains of sea- worms. Traces 

 of plants (Lycopodiaceoe) have been found in the Upper Ludlow. 



Principal Characteristic Genera. — Zoopliyta: Aulacophyllum, Cceaiies, 

 Cladocora, Cystiphyllum, Goniophyllum, Omphyma, Palceocyclus, 

 Thecia. JBryozoa : Fenestella. Bracliiopoda : Obolus, Siphonotreta, 

 Athyris, Orthis, Eetzia. LamelUhr and data : Cardiola, Ciidophorus, 

 Ctenodonta, Grammysia, Orthonota. Gasteropoda : Holopella, ^klur- 

 chisonia. JEchiyiodermata : Apiocystites, Crotalocrinus, Echinoencrinus, 

 Enallocrinus, Dimerocrinus, Eucalyptocrinus, ]\Iarsupio3rinus, Paleaster, 

 Palasterina, Prunoc5^stites, Pseudocrinus, Palseocoma. Crustacea : 

 Deiphon, Proetus, Pterygotus, Cyphaspis, Eacrinurus, Ceratiocaris, 

 Leperditia. 



FOSSILS OF THE UPPEII SILUELVx/ 



Actinophyllum pUcatum. Fhil. M. GI-. Chondrites regularis, G. J. 11. p. 473. 



S. 2, 386. Lycopodiaceae, Hoohei\ Gr. J. 9. p. 8. 



Chondrites antiquus, Brong^ Hist. p. 



A:moephozoa. 



Acatithospongia Siluriensis, JfCoy, S. Cliona antiqua, Portl, Gr. R. p. 360. 

 F. p 67. Cnemidium tenue, Z/0W5t?. S. S.p. 



ZooPHYTA (Anthozoa). 



Acervularia anana?, Linn. Sil. 243. Clysiophyllum vortex, M'Coy, P. F. 52 



Alveolites Bechei, Edw. Sil. 132, Coenites intertextus, Eichw. 



fibrosa, Lonsd.S. S. 681. juniperinus, Eichw. Sil. 133. 



Grayi, Edw. Arch. Mus. 5. 258. labrosus, Ediv. Arch. 5. S02. 



oculata, Goldf. Pet. t. C5. linearis, Edic. Arch. 5. 302. 



Arachnophyllum typus, JECoy, P. F. 38. strigatus, 31' Coy, P. F. 22. 



difluens, Edw. Arch. Mus. 5. 431. Cyathaxonia Siluriensis, M'Coy, P. F, 



Aulacophyllum mitratum, His. sj). Leth. 36. 



Suec. p. Cjathophyllum articulatum, Wahl. Sil. 



Aulopora=Syringopora. 243. 



Chaetetes Bowerbanki, Edw. Arch. Mus. Loveni, Edw. Arch. Mus, 5. 364. 



5. 272. rccurvum, Edw. Arch. 5. 368. 



Fletcheri, Edw. Arch. Mus. 5, 271. truncatum, Linn. 5/;, Sil. 243, 



pulchellus, Edw. Arch. Mus. 5. 271. augustura, Lonsd. S. S, t. 16. 



Cladocora sulcata, Lous. S. S. 



