94 MOLLUSCA FROM THE CRAG. 
Jordan Hall; all the specimens I have seen from these Deposits are small, scarcely 
exceeding half an inch in length, while the one from Bridlington has nearly twice 
that diameter. 
This appears to differ but very slightly from the more elongated variety of 
L. caudata, considered a different species by our British Conchologists, as well as by 
Dr. Lovén, the principal difference is in the strie, which in this shell is finer or 
more numerous. 
6. LepA TRUNCATA, Brown. Tab. X, fig. 14, a—dé. 
Nucuna truncata. Brown. Ilust. Conch. Gr. Brit., pl. 25, fig. 19, 1827. 
— — Smith. Mem. Wern. Soc., vol. viii, p. 42, 1838. 
Spec. Char. Testd transversd, ovatd ; concentrice striata, tumidd, subequilatera ; 
antice votundatd, postice truncatdé vel subsinuatd ; umbonibus prominulis ; margine 
integerrimo. 
Shell transverse, ovate, subequilateral, tumid, concentrically striated; anterior 
side rounded, posterior truncate or subsinuated ; umbones slightly prominent ; margin 
smooth. 
Length, Zths of an inch nearly. Hezght, 3 an inch. 
Locality. =” 
This shell has been rejected by the authors of the ‘ Hist. of British Mollusca’ as 
an existing British species, and although not found in any of our Crag Deposits, 
belongs undoubtedly to the Upper Tertiaries of England. It is an animal still living 
in the Arctic Seas, but is no longer an inhabitant of our own. 
The specimen figured was obtained by Robert M‘Andrew, Esq., who has 
obligingly permitted me the use of it for the purpose of description: it was, he says, 
in company with other, supposed extinct, species as Pecten Islandicus, &c., and 
dredged from the depth of 40 to 60 fathoms, off the North Western Coast of the Isle of 
Skye. It is ornamented with close-set strize, that appear independent of lines of growth, 
as they occasionally bifurcate, and are not, therefore, quite parallel to the margin; its 
most peculiar character is on the posterior side, where there is a somewhat angular 
ridge or keel from the umbo to the projecting beak-like termination, forming above 
a large and elongate lunule-like space between it and the margin of the shell; below 
is another obtuse ridge extending from the umbo to the posterior part of the ventral 
margin, and between this and the pointed termination, the shell is flattened or slightly 
contracted at the margin, from which it is presumed it received its name: the shell is 
tumid, the umbones somewhat curving over, so that the ligamental area projects 
inwards; there are from 12 to 18 teeth on each side, while the smus in the mantle is 
not very deep: the specimen is a full grown or aged individual, as the interior is 
irregularly thickened, and more especially rugose between the margin of the shell 
and the line of attachment by the mantle. 
