40 ANATINID^. 



front, with a slight indentation towards the posterior side, 

 which is more or less obliquely truncated, and separated by a 

 blunt angular ridge in each valve, with an obscure intermediate 

 fold, making this side appear bicarinated; dorsal margins 

 gently curved : beaks very prominent, obliquely inflected to 

 the posterior side ; the space below them on each side is deeply 

 excavated : ligament short and cylindrical, greyish- horn colour, 

 separating the valves by an elliptical gap : cartilage yellowish, 

 contained in a narrow but solid receptacle, which lies parallel 

 with the hinge-line, and does not project far within the shell ; 

 the receptacle is supported underneath by the ordinary rib-like 

 process : hinge-line obtusely angular : hinge-plate narrow and 

 slight : ossicle as in the other species : inside yellowish ; edges 

 blunt : scars nearly marginal. L. 2. B. 2-5. 



HABITAT : 4-70 f. in suitable parts of the English, 

 Irish, Scotch, and Shetland coasts ; difficult to procure 

 on account of its habit of burrowing rather deeply in 

 muddy sand. Not uncommon in the " alluvial" deposit 

 at Belfast (Hyndman and Grainger) ; Wexford (Sir 

 Henry James) ; Coralline Crag (S. Wood) ; "glacial" 

 formation near Drontheim, 400-500 feet above the 

 present sea-level (Sars) ; Palermo (Philippi) . It has 

 been noticed as a Swedish and Norwegian species by 

 Loven, Sars, M f Andrew and Barrett, Danielssen, and 

 Malm, at various depths between 8 and 100 f . } 

 M f Andrew dredged it off Gibraltar in 45 f. ; and Martin 

 obtained it from fishermen on the coast of Provence, 

 but smaller in size than northern examples. 



This handsome shell may easily be recognized by its 

 almost globular form. The young and fry correspond 

 in shape with, the adult ; but they are white and not 

 so convex, and their dorsal margins are quite straight. 

 The ligament, as well as the epidermis are wonderfully 

 preserved in fossil specimens dug out of the clay-bed at 

 Belfast. 



Montagu described it as a large form of T. distort a. 



