SIOKRIS — BRITISH FOSSILS. 
237 
Sedgwick, noticed in the last section, arc 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 Wenlock bods — thus constituting, with the Lower Llan- 
dovery, an intermediate zone betwocu the underlying and overlying 
Silurian rocks. 
The fossils of this group are nearly all marine, and belong chiefly to 
the Inrcrtebrata ; the Vertehrata being represented by a few remains 
of fishes (Placoid), and those found in the uppermost beds of the 
series. On the other hand, the luvertebrata 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 MoUusca, 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 (Lycopodiacetc) have been found in the Upper Ludlow. 
Principal Characteristic Genera. — Zooplujta: Aulacophyllum, Ca^uiies, 
Cladocora, Cystiphyllum, Goniophyllum, Omphyma, Palajocyclus, 
Thecia. Bnjo7,oa : Fenestella. Brachiopoda : Obolus, Siphonotreta, 
Athyris, Orthis, Retzia. Lamellibranchiata : Cardiola, Clidophorus, 
Ctenodonta, Grammysia, Orthonota. Gasteropoda : Holopella, Mur- 
chisonia. Uckinodermata : Apiocystites, Crotalocrinus, Echinoencriuus, 
Enallocrinus, Dimerocrinus, Eucalyptocrinus, Marsupiocrinus, Paleaster, 
Palasterina, Prunocystites, Pseudocriuus, Palasocoma. Crustacea : 
Deiphon, Proetus, Pterygotus, Cyphaspis, Eacrinurus, Ceratiocaris, 
Leper ditia. 
FOSSILS OF THE UPPER SILURIAX. 
PlAJi'T^. 
Actinophylluin plicatum. Phil. M. G. Chondrites rogiilaris, G. J. 11. p. 473. 
S. 2, 380. LycopodiaceEe, Hooker, G. J. 9, p. 8. 
Chondrites antiquus, Bronj, Uist. p. 
AlIOHPUOZOA. 
Acaiithospongia Siluriensis, M'Coij, S. Cliona antiqua, Porll. G. R. p. 360. 
F. p 67. Cnemidium teuue, Xci«6'c?. S. S.p. 
ZooPHTTA (Anthozoa). 
Acervularia ananas, Linn. Sil. 243. 
Alveolites Bechei, Edw. Sil. 132. 
fibrosa, Lo7isd,S. S. 681. 
Grayi, Edw. Arch. Mus. 5. 258. 
oculata, GoUf. Pet. t. Go. 
Clysiophyllum vorlox, M'Coy, P. F. 52 
Coenites intertextus, Eichw. 
Arachnophyllum typus, J/'Coy, P. F.38. 
difluens, Edw. Arch. Mus. 5. 431. 
juniperinus, Eiclur. Sil. 133. 
labrosus, Edw. Arch. 5. 302. 
linearis, Edtr. Arch. 5. 302. 
strigatus, M'Coy, P. P. 22. 
Cyathaxonia Siluriensis, 31' Coy, P. F. 
Aulacophyllum mitratum. His. q). Letb, 
36. 
Suec. p. 
Cyathophyllum articulatum, WahL Sil. 
Aulopora= Syringopora. 
Chsetetes Bowerbanki, Edw. Arch. Mus. 
5. 272. 
Fletcheri, Edw. Arch. Mus. 5. 271. 
pulchellus, Edw. Arch. Mus. 5. 271. 
Loveni, Edw. Arch. Mus. 5. 364. 
recurvum, Edw. Arch. 5. 368. 
truncatum, Linn. sp. Si!. 243. 
angustum, Lonsd. S. S. 1. 16. 
Cladocora sulcata, Lons. S. S. 
