Chap. XIII.] 
PERMIAN FOSSIL SHELLS. 
339 
the lamellae characteristic of the Cup-corals of the old rocks. The abundant 
Fenestella retiformis, Foss. 84. f. 3, and Synocladia virgulacea, are also of a type 
peculiar to the primeval fauna. Crinoids are rare ; but there is in England a 
species of the genus Cidaris, the earliest known representative of the modern 
Sea-urchins *. The Brachiopods offer many Producti analogous to, but chiefly 
distinct from, those of the Coal-period, and number about twelve species, in- 
cluding Productus horridus and P. Cancrini, the former being the most common 
Permian shell in Britain and Germany (Foss. 85. f. 2). These very species 
(Productus horridus and P. Cancrini), with Spirifer alatus and Sp. cristatus ?, 
have been found in blocks of limestone at Spitzbergen, and are described in 
detail by de Koninck. Of the genus Spirifer, Sp. alatus (f. 1) is the most cha- 
racteristic ; and Sp. cristatus is supposed to be common to the Carboniferous and 
Permian rocks. Of the genus Orthis, which prevails so greatly from the Lower 
Silurian to the Carboniferous inclusive, we here find no trace ; it is represented 
by Streptorhynchus pelargonatus, Schloth., and other species. The genera Stro- 
phalosia (King) and Aulosteges (Helmersen) are more especially characteristic 
of the Permian system : the former occurs in Germany, England, and the United 
States j the latter is confined to Russia. Of the few species of Terebratula 
which are known, two or three are exceedingly abundant, and one, T. elongata of 
Schlotheim, can scarcely be distinguished from a common Carboniferous species. 
Athyris Royssii is supposed to be identical with the Devonian and Carboniferous 
shell (see 1st Edit, of Siluria, p. 308) ; but my friend Keyserling considers it to 
be a distinct type, which he has named Terebratula Royssiana, and he has 
figured it in his memoir descriptive of the fossils collected by the botanist 
Schrenk f. 
Fossils (85). Permian Shells. 
1. Spirifer alatus, Schl. 2. Productus 
horridus, Sow. 3. Schizodus (Axinus) ob- 
scurus, Sow. 4. Strophalosia lamellosa, 
Geinitz. (All from the county of Durham. 
These species, except, perhaps, the Schizo- 
dus, are equally common in Germany and 
Britain.) 
[The figures are about half the natural 
size.] 
The genus Pentamerus, so characteristic of the Silurian epoch, but rare in the 
* The species of Cidaris often quoted from 
Carboniferous rocks, belong, as has been well 
shown by M'Coy, to a different family. They 
are now termed Archceocidaris. See Ann. Nat. 
Hist. ser. 2. vol. iii. p. 352. They have been found 
also in the Devonian rocks by Sandberger. 
t " Pal'aontologische Bemerkungen von A. Graf 
Keyserling," in A. Gr. Schrenk's ' Eeise zu der Sa- 
mojeder und zum arktischen Uralgebirge/ zweiter 
Theil, 1854. 
This memoir, prepared in 1848, was not pub- 
lished until 1854, and hence some of the nomen- 
clature has been set aside for other names. The 
work is highly worthy of consultation. In it the 
palaeontologist will find that the author, who has 
personally traced the Permian rocks over a vaster 
northern area than any other individual, enume- 
rates the following fossils, never before described : 
— Diastopora labiata, Strophalosia tholus, Pleuro- 
tomaria atomus, and six species of Bivalved En- 
tomostraca (mostly Kirkbyae, according to Eupert 
Jones). Count Keyserling makes the important 
observation that, as these little bivalved Crustacea 
are very generally present throughout vast spaces 
of Eussia in beds of Permian rock which contain 
no other fossil, it is essential to speak of these 
fossils as singularly characteristic of the forma- 
tion. The Permian Entomostraca are carefully 
illustrated and described by Kirkby and Jones 
in the Trans. Tyneside Nat. Club for 1859. 
z 2 
