VENUS. 403 



and are preceded by a rather large heart-shaped hmule, 

 which is well defined by being laterally sunken, though 

 elevated in the middle, and is concentrically substriated, 

 and usually tortuous at the suture. The ligament, which 

 is rather large when not concealed by the overlapping of the 

 hinder dorsal lips, is seated in a tolerably ample and some- 

 what shallow lanceolate excavation, which is smooth, and 

 in the left valve, where it is more manifest, is adorned with 

 a few more or less flexuous cross-bars of a livid smoke- 

 colour. The interior is of an uniform white ; the edge is 

 obtuse, and distinctly but not coarsely crenated, except 

 posteriorly, where it is usually more or less entire. The 

 hinge-margin is broad, and is furnished in each valve with 

 three divergent teeth, of which the anterior in the right 

 valve is very short (not reaching to the margin), and the 

 central only subbifid ; the two front teeth of the opposite 

 valve are generally more or less cloven when young. 



The fry, being far more angular in shape, and having the 

 ridges thinner, the radiating costellEe more' apparent, and 

 the tubercles not yet developed, has erroneously been con- 

 dered a distinct species, and separated under the name of 

 cancellata. The shell so named in Donovan, and which is 

 referred by Montagu to the present species, seems to bear 

 an at least equal resemblance to striatula. 



We possess foreign examples which are two inches and a 

 half in length, and two inches and a third in breadth ; but 

 know of no British specimens approaching these dimensions. 



The animal is suborbicular, very thick, and of a pale 

 yellowish-white colour. The mantle is freely open from 

 the tubes to the anterior adductor muscles ; its edges are 

 serrated or fringed, presenting more or less of a furbelowed 

 aspect. The siphons are short, but well separated, and of 

 a yellowish-white colour, with tawny specks or dark grey 



