404 TELLINID.E. 



dorsal margin on the anterior side long and sloping but not 

 curved, that on the posterior side being much shorter, diver- 

 ging from the other at considerably more than a right angle, 

 and nearly straight : beaks small, pointed, incurved, and 

 turned towards the posterior or ligamental side : ligament very 

 short, partly prominent, the lower half being imbedded in the 

 hinge-plate, horncolour : corselet long, rather deep, with thick- 

 ened and projecting edges : hinge-line obtusely angular : hinge- 

 plate thick, much longer but narrower on the anterior than on 

 the posterior side, abruptly truncate at the end of the liga- 

 ment : teeth, in the right valve a triangular and cloven car- 

 dinal immediately below the beak, flanked on each side by a 

 longer and laminar cardinal, the anterior of which is set ob- 

 liquely and the posterior or larger one in a line with the liga- 

 ment ; laterals in this valve two on each side, receiving be- 

 tween each pair the single lateral of the opposite valve ; the left 

 valve has two diverging cardinals and an intermediate minute 

 tooth or denticle ; the laterals (one on each side) in that valve 

 are short and sometimes tubercular: inside highly polished 

 and usually glossy, more or less stained with violet, especially 

 on the posterior side ; margin finely and regularly notched 

 from the anterior end to the ligament; the posterior dorsal 

 margin is more closely notched or crenulated, and the other 

 dorsal margin is quite smooth : pallial scar slight, with an 

 oval and rather small sinus : muscular scars strongly marked, 

 of an irregular shape. L. 0-6. B. 1-1. 



Var. 1. turgida. Shell larger, ventricose, longer in propor- 

 tion to its breadth, and nearly lustreless except in the young. 

 L. 1. B. 1-6. 



Yar. 2. nitida. Shell somewhat smaller than usual and 

 more convex, broader in proportion to its length, of a brilliant 

 lustre. 



HABITAT : Large sandy bays, from low-water mark 

 to a few fathoms within the Laminarian zone. Var. 1. 

 Stornoway in the outer Hebrides (Barlee). Var. 2. 

 Dredged in 18 fathoms, ten miles off Shields (Da- 

 mon) ; and on the Dogger bank in 12-15 fathoms, 

 thirty miles from Scarborough (Leckenby) . This spe- 

 cies is fossil in the Belfast deposit (Millen) ; Wexford 

 (James); Ayr (Smith); Moel Tryfaen, Carnarvonshire, 



