238 MOLLUSCA FROM THE CRAG. 
Spec. Char. Testa ovata vel ellipticd, tenui, levi, inequilaterali ; latere antico majiore, 
rotundato ; latere postico angulato, subcarinato ; dentibus lateralibus parvis, tenuibus ; 
sinu palliari magno, profundo. 
Shell ovate or elliptical, thin, smooth, inequilateral ; anterior side the larger, and 
rounded; posterior angulated, and obscurely carinated; lateral teeth small, thin ; 
palleal sinus large and deep. 
Length, 4 inch. Height, 2 inch. 
Locality. Cor. Crag, Sutton. 
Red Crag, Sutton, Bawdsey, Walton Naze. 
Clyde Beds (Smith), Bracklesham (Dizon). 
Recent, British and Scandinavian Seas. 
This is abundant in the Coralline Crag, and, although a thin shell, I have found 
many specimens in the Red Crag at Bawdsey, some of which had the valves united. 
It differs from 4. ¢enwis in being less equilateral, though it is more so than the 
succeeding species, 4. fabalis, and on the siphonal side it preserves a sort of 
ntermediate character between the two, being less pointed than the one but more so 
than the other. There is an unequal tumidity in the two valves, causing thereby an 
inequality in the palleal sinus. The striz or lines of growth are somewhat more 
strongly marked in this than in the succeeding species. 
2. ABRA FABALIS, S. Wood. Tab. XXII, fig. 12, a, 6. 
Spec. Char. Testa ovatd, vel elongato-trapezoidali, inequilaterali, tenur, fragili, levi ; 
latere antico longiore, rotundato; latere postico angulato ; margine ventralt arcuato ; 
dentibus lateralibus elongatis ; foved ligamenti mediocre. 
Shell ovate, or elongately trapezoidal, inequilateral, thin, fragile, and smooth; 
anterior side the longer, and rounded; posterior angulated; ventral margin curved ; 
lateral teeth thin and elongated ; ligamental area moderate. 
Length, 2 inch. Height, $ inch. 
Locality. Red Crag, Walton Naze. 
This shell presents so great a difference to the preceding (a/éa) as to entitle it, in my 
opinion, to an isolated position; being more elongated and slender, with the posterior 
side more pointed, and it also is a thinner shell, with a more delicate and less 
pronounced dental apparatus; less elongated than A. prismatica, but intermediate 
between the two, differing, however, from 4. zztermedia in being much more inequi- 
lateral, that shell having the umbo nearly central, while in this one the anterior side is 
at least two thirds larger than the posterior one. Our shell somewhatresembles Zedlina 
longicollis, Scacchi, Erycina longicollis, Philippi; but the hinge of that species is even 
more slender, with more elongated lateral teeth, and the support for the cartilage is 
smaller. 
