238 MOLLUSCA FROM THE CRAG. 



Spec. Char. Testa ovatd vel ellipticd, tenui, lavi, incequilaterali ; latere antico majiore, 

 rotundato; latere postico angidato, subcarinato ; dentibus lateralibus parvis, tenuibus ; 

 sinu palliari magno, pro/undo. 



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, | inch. Height, f- inch. 



Localitg. Cor. Crag, Sutton. 



Red Crag, Sutton, Bawdsey, Walton Naze. 

 Clyde Beds (Smith), Bracklesham (Dixon). 



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 A. tenuis in being less equilateral, though it is more so than the 

 succeeding species, A. 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 striae 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, b. 



Spec. Char. Test a ovatd, vel elongato-trapezoidali, incequilaterali, tenui, fragili, Icevi ; 

 latere antico longiore, rotundato ; latere postico angidato ; margine ventrali arcuato ; 

 dentibus lateralibus elongatis ; fovea 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, f inch. Height, \ inch. 



Localitg. Red Crag, Walton Naze. 



This shell presents so great a difference to the preceding (alba) 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 A. intermedia 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 somewhat resembles Tellina 

 longicollis, Scacchi, Ergcina 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. 



