390 VENEIIID^. 



lower angle is, however, always rounded off) becomes only 

 obsoletely so in the more aged examples ; from a similar 

 rounding off of the upper angle, the hinder margin is con- 

 vex and oblique. The ligament is large, yellowish-brown, 

 and not elevated above the dorsal line. The lunule is lan- 

 ceolate, moderately large, but neither profoundly impressed 

 nor sharply defined ; it is often of an uniform liver-colour. 

 The umbones are not at all prominent, but are much in- 

 clined forwards, the beaks are obtuse, and curve both in- 

 wards and anteriorward. The inner surface is white or 

 stained with pink ; the pallial sinus semi-elliptic. The 

 teeth are divergent, the extremes forming at least a right 

 angle ; the central of the left valve, and the posterior and 

 the central of the right valve are bifid. 



The ordinary run of specimens do not generally exceed 

 an inch and a half in length, and half an inch less in 

 breadth ; we have, however, an individual now before us 

 which has the large dimensions of nearly two inches and 

 a-half in length, and almost an inch and three-quarters in 

 breadth. Young examples are perfectly smooth. The 

 variety termed Sarniensls, by Dr. Turtou, is usually of a 

 coarser texture, lighter colour, and rather more ventricose ; 

 its concentric strise are generally closer, and their tendency 

 to become more remote posteriorward is consequently less 

 distinctly manifested. These characters are, however, 

 rarely all evident in the same specimen, the union be- 

 tween the type and the variety being perfect in gradation. 

 There is a great bluntness or absence of angularity in the 

 outline of virginea, as compared with that of its British 

 congeners. 



The animal of T. virginea resembles, in most of its cha- 

 racters, that of the other forms of the genus. It is entirely 

 of a cream- white hue, except the extremity of the branch- 



