136 MOLLUSCA FROM THE CRAG. 
Shell small, roundedly ovate, oblique, subequilateral, tumid, smooth, thin, and 
fragile ; posterior side with one obsolete fold or furrow, one obtuse cardinal tooth. 
Diameter, 3th of an inch. 
Locality. Coralline Crag, Sutton. Recent, North Britain, and Aigean Sea. 
This is not an abundant fossil, and I have only met with it in the rich Depot 
at Sutton. 
When my Catalogue was compiled this species had not been recognised in the 
recent state, and the name then proposed for it being without description, or anything 
by which it could be identified, must give way to the subsequent one of Professor 
Forbes. In comparing our fossil with the specimens now obtained in the British Seas, 
no essential difference can be detected, and there is little doubt of their identity, and 
when it is considered that the recent shell has been separated into three distinct 
species, more than ordinary range in variation may be expected; the fossil is, 
however, free from the ferruginous covering which obscures some of the characters of 
the living shell; the Authors of the ‘Hist. of Brit. Moll.’ after uniting the three 
species of Mr. Jeffreys, describe their shell as entirely without a fold, but in the most 
perfect specimens of our fossil may be seen an obscure inflection upon the posterior 
side, which is here considered to constitute one of its most determinable characters, 
and has always been in my Cabinet under the MS. name of Cryptodon, from that 
resemblance. In the few specimens that I possess no great variation is observable ; 
the general form is obliquely orbicular, the diameter rather greater when measuring 
from the umbo to the ventral margin than from the anterior to the posterior side, 
and in some specimens the outline shows a decided pentangular form. ‘There is one 
obscure tooth in each valve, like that in the preceding species, and the ligament is 
placed in a depression beneath the dorsal margin, so that it must have been nearly 
hidden when the valves were united; the anterior muscle mark is large, and of 
an ovate form, and not band-like as in Zucina. This shell has much the aspect of 
Kelhia, and might, without much violence to classical arrangement, be placed there, 
or at least, judging from the characters of the shell alone, it appears to have a 
nearer relationship to that genus than to Zwciva. In the living state it has only 
been met with as a deep-water shell, both from the A‘gean and the North British 
Seas, ranging from 20 to 100 fathoms. 
Loripes,* Poli, 1791. 
Lortprs—Lonipoperma. Poli. 
TELLINA (sp.). Linn. 
AMPHIDESMA (sp.). Lam., 1818. 
THIATISA (sp.). Leach, 1819, 54, Gray: 
Licuta. Menke, 1830, if 
UneuLina. Bose., 1802. 
Taras? Risso., 1826. 
* Etym. Lorum, a strap, and pes, a foot. 
ii at 
