GEOLOGICAL DISTRIBUTION OF SHELLS. 437 
the English student, Mr. Morris’s “Catalogue of British 
Fossils,” of which an enlarged edition is in the press, will 
be the most valuable for reference. In the works which we 
have especially recommended for reference (ante, p. 10), 
figures are given of some of the characteristic shells from 
each formation, as follow; commencing with the most 
ancient deposits. 
SILURIAN System. Jy. p. 350. 
-Orthis orbicularis; Zy. fig. 409. 
grandis ;—fig. 427. 
Terebratula navicula ;—fig. 410. 
—— Wilsoni ;—fig. 413. 
Pentamerus Knightii ;—fig. 411. 
————. levis ;—fig. 426. 
Atrypa reticularis ;—fig. 414. Wond. p. 786. 
Lingula Lewisii; Zy. fig. 412. 
Strophomena depressa ;—fig. 421. 
DEVONIAN System. Jy. p. 342. 
Calceola sandalina; Ly. fig. 403. 
Stringocephalus Burtini ;—fig. 404. 
Megalodon cucullatus ;—fig. 405. 
“The Sinurran System,” by Sir R. I. Murchison, a splendid work 
on the rocks and fossils of the above formations, contains numerous 
figures of the shells peculiar to each group of strata; and many 
other species are delineated in the Memoir on the Devonian deposits 
of Devonshire and Cornwall, by Sedgwick and Murchison, Geol. Trans. 
New Series, vol. v. plates liii—lvii. A Memoir on the Paleozoic Rocks 
of Germany and Belgium, by the same distinguished geologists, is 
also accompanied by many figures of fossil shells belonging to the 
same geological epochs. (Geol. Trans. New Series, vol. vi. 
See also Prof. M‘Coy’s “Silurian Fossils of Ireland,” and his De- 
scription of the British Paleozoic Fossils in the Woodwardian 
Museum at Cambridge, in Prof. Sedgwick’s “Synopsis oF THE CLAs- 
SIFICATION OF THE British Patwzozoic Rocks,” of which two Parts 
are already published. 
