264 MOLLUSCA FROM THE CRAG. 



side the larger, and rounded ; left valve much depressed ; palleal sinus of moderate size, 

 rather broad. 



Length, -| inch. Height, T ° T 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 

 maybe 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. pratenue ; the palleal sinus extends inwardly, a little beyond a 

 line drawn perpendicularly from the umbo. 



2. Cochlodesma pr^teneuum, S. Wood. Tab. XXVI, fig. 4, a, b. 

 Anatina pkjstenera. S. Wood. Catalogue, 1840. 



Spec. Char. Testa transversa, ovatd, inaquilaterali, incsquivalvi, tenui, fragili ; antiee 

 rotundatd convexiusculd ; postice breviore, truncatd, subrostratd ; tenuissime gramdatd. 



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, \ inch. 



Locality. Cor. Crag, Sutton. 



I have about half a dozen specimens of this shell. It differs from C. pratenue 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. pratenue, but the hinge is injured. I have some 

 fragments also of what may perhaps be another species, with a very scabrous 



