264 MOLLUSCA FROM THE CRAG. 
side the larger, and rounded; left valve much depressed ; palleal sinus of moderate size, 
rather broad. 
Length, % inch.  Herght, 2; inch. 
Locality. Red Crag, Walton Naze. 
About half a dozen perfect specimens are in my cabinet: unfortunately they are all 
the left valve. 
In comparing my fossils with a specimen of Cochlodesma Leanum, Couthouy, ‘ Bost. 
Journ. Nat. Hist.,’ vol. ii, p. 170, (a recent species from America, and its nearest 
relative,) the Crag shell appears to be less equilateral, the siphonal side being much 
the shorter of the two, and I have in consequence considered it distinct. Our shell 
may be further described as rather flatter compressed, the left valve being the more so 
of the two, judging from a fragment of the right one in my cabinet; the umbones are 
slightly prominent, and cleft by the ligament; the spoon-shaped process is broad and 
strong, projecting towards the anterior; the exterior shows merely lines of growth, 
with a slight rugosity on one side, but it is not covered with the granulated or 
shagreen surface of C. pretenue ; the palleal sinus extends inwardly, a little beyond a 
line drawn perpendicularly from the umbo. 
2. COCHLODESMA PRETENERUM, S. Wood. Tab. XXVI, fig. 4, a, 6. 
ANATINA PRETENERA. S. Wood. Catalogue, 1840. 
Spec. Char. Testa transversd, ovata, inequilaterali, inequivalvi, tenui, fragili ; antice 
votundatd convexiusculd ; postice breviore, truncata, subrostrata ; tenuissime granulata. 
Shell transversely ovate, inequilateral, inequivalved, thin and fragile, with a finely 
granulated exterior; anterior side the larger, rounded, and slightly tumid; ventral 
margin curved. 
Length, inch. Height, 5 inch. 
Locality. Cor. Crag, Sutton. 
I have about half a dozen specimens of this shell. It differs from C. pretenue in 
having the siphonal side shorter, narrower, and truncated, with a more distinct 
angular slope from the umbo to the ventral margin ; the anterior dorsal edge is very 
thin, and slightly folded over, with a small sinus at the extreme point of the umbo, 
through which the ligament was visible, and probably projected somewhat; the 
exterior is smooth to the naked eye, but under a magnifier appears finely granulated. 
The impressions by the adductor muscles indistinct ; the palleal sinus extends a little 
beyond the cartilage support. 
A small specimen in my cabinet, from the same locality, strongly resembles, and 
is probably the young state of C. pretenue, but the hinge is injured. I have. some 
fragments also of what may perhaps be another species, with a very scabrous 
