BIVALVIA. 289 
the shell is full grown. There is a small sinus in the mantle-mark, and the impressions 
of the adductors are very distinct. Within these, on both sides, a ridge diverges from 
beneath the umbo; that on the anterior side is the more prominent. The ligament 
appears to have been supported upon a prominent fulcrum, while the cartilage was 
placed in a depressed line upon the dorsal edge, and there is a small gape on the 
siphonal side. 
The shell above referred to, in the ‘Hist. of Brit. Moll.’ may possibly be the 
descendant of our fossil, as [ had supposed when compiling my Catalogue, (Ann. 
and Mag. of Nat. Hist., 1840, p. 245, cvfra), but several dead valves of the recent 
species, since obtained from the beach on Stone Point, at Walton Naze, cast a doubt 
upon that identification, the recent shell having the siphonal side much broader than 
the anterior, and is not quite so flat. 
I have no doubt of our fossil being distinct from Savicava arctica, nor do I think 
there is any good reason for believing it to be the fry of some larger species. It is 
difficult to determine where it ought to be placed, but it appears to conform more 
nearly with the diagnosis of Sawicava than with any other existing genus. I would 
have adopted drcinel/a, proposed by Philippi for the succeeding species, but that this 
name had been twice previously used in the class Mollusca ; and Sphenia, the genus in 
which I had provisionally placed it, has a different hinge with an internal ligament 
like that of J/ya, placed upon a spatulate projection. 
3. SAXICAVA? CARINATA? Brocchi. Tab. XXIX, fig. 5, a—e. 
MytiLus carinatus? Broc. Coq. Foss. Subap., p. 585, t. 14, fig. 16. 
_ — ? Goldf. Pet. Germ., p. 179, pl. 13], fig. 14. 
ARCINELLA CARINATA. Phil. En. Moll. Sic., vol. ii, t. 16, fig. 9. 
SpHENTA anGuLaTA. S. Wood. Catalogue, 1840. 
Spec. Char. Testd minutd, transversd, oblonga, valde inequilaterali, tenui, fragili ; 
antice brevi, postice carinatd, angulatd, productd, granulosd ; cardine unidentato. 
Shell minute, transverse, oblong, very inequilateral, thin, and fragile ; anterior side 
short, posterior angulated, carinated, and produced, with a granular surface; hinge 
with one tooth. 
Length, 5 inch. Height, ¢ inch. 
Locality. Cor. Crag, Sutton. 
A few specimens only of this species have come under my observation, and those 
are all in my own cabinet. 
The shell it most resembles is the preceding, from which, however, it differs in 
having the siphonal side much more angular, pointed, and carinated, with also a 
roughened or shagreen-like exterior, most distinctly visible on the posterior slope. 
38 
