Chap. XIII.] 
PEEMIAN FOSSILS. 
341 
England, and in the United States. Area striata and Clidophorus costatus are 
other characteristic species. Together with these are found species of Leda, 
Solemya, Edmondia, Myacites, Cardiomorpha, Astarte, Lima, and Pecten. 
The Gasteropods also seem to have decreased in numbers during the forma- 
tion of the Permian strata, and to have had great difficulty in accommodating 
themselves to new conditions *. In the Magnesian Limestone of Durham they 
are comparatively rare fossils, numbering 17 in a list of 58 species of Mollusca. . 
In South Yorkshire, where individuals are numerous and species few, the Gas- 
teropods number 9, and the other Mollusks 10. Turbo helicinus, prevailing 
largely there, and Turritella Altenburgensis and Pleurotomaria antrina are the 
most characteristic species of this class in England. Altogether there appear to 
be about 43 Permian Gasteropoda. Scarcely any of these have lived on from 
the Carboniferous to the Permian epoch f, though many belong to Carboniferous 
or, rather, Palaeozoic genera, such as Pleurotomaria, Murchisonia, Straparollus 
and Macrocheilus. 
The Cephalopods, which under the forms of Goniatites, Nautilus, and Ortho- 
ceras were so numerous during the Carboniferous period that more than 160 
species have been described from its strata, were greatly reduced previously to the 
commencement of the Permian era. The only species occurring in England is 
Nautilus Frieslebeni, Geinitz. Other species, belonging to the same genus and to 
Orthoceras and Cyrtoceras, have been described from the Zechstein of Germany 
and the Permian strata of the United States, making the list up to 10. 
Three Pteropods have occurred, Conularia Hollebeni being the most import- 
ant. Four species of Bellerophon occur in the Permian strata of Nebraska. 
Trilobites are entirely wanting %. In the study of the Palaeozoic Succession, 
we see that the disappearance of this race is regularly announced by a gradual 
diminution of its numbers during the preceding epochs. Appearing among the 
earliest forms of life, and having their maximum of development in the Silurian 
period, Trilobites decrease very sensibly in the Devonian strata, and in the 
Carboniferous deposits are reduced to some small species, of which Phillipsia 
and Griffithides are the last expiring forms. And here we are presented with 
one of those beautiful links in Natural History, of which the strata forming the 
earth's crust have afforded so many proofs ; for, with the final extinction of this 
family, destined never more to reappear, its place is taken by allied Crustaceans, 
foreshadowing the Limulus, the earliest of which Limuloid Crustacea (Belinurus 
and Prestwichia) were created during the formation of the Coal-measures ; and, 
represented perhaps in Permian rocks by the obscure Russian fossil known as 
the Limulus (?) oculatus of Kutorga, they were succeeded in the Secondary 
epoch by the Limulus itself; and that has survived all the numerous revolutions 
which have followed its creation, some of its species being coexistent with our 
own race §. 
The preceding remarks refer more especially to the Permian fossils of Europe. 
Only of late years have we obtained information of the Permian species of Ame- 
rica. It is interesting to find there that the same genera characterize the last 
of the Palaeozoic systems as in Europe. In Kansas, Texas, and Nebraska, 
Permian rocks occur containing Productus, Camarophoria, Strophalosia, Strep- 
torhynchus, Chonetes, Spirifer, Edmondia, Gervillia, Monotis, Schizodus, Mur- 
chisonia, Orthoceras, Bellerophon, and Fenestella. Not only are the genera the 
* See also ' Kussia-in-Europe,' vol. i. p. 209. J Phillipsia perannulata has recently been de- 
t See Mr. Kirkby's later remarks on the recur- scribed from the Permian strata of Kansas, but it 
rence of Carboniferous Forms in Permian strata, is doubtful whether it may not really belong to 
Quart. Journ. Geol. Soc. vol. xvi. p. 416; and Ann. the Carboniferous rocks. 
Nat. Hist. 3rd ser. vol. x. p. 202. § ' Kussia-in-Europe,' loo. cit. 
