CYPRINA. 443 



The hinge-margin is moderately broad, and is furnished in 

 the right valve in addition to its remote, and not much pro- 

 jecting posterior lateral lamina, with four primary teeth, of 

 which the hinder is very oblique, acutely edged, and much 

 shelving anteriorward, the two middle are simple (not 

 bifid), and do not extend to the extreme margin, whilst the 

 fourth, which is a mere denticle, is adjacent to the interior 

 edge, and looks rather like a somewhat divergent inter- 

 rupted continuation of the preceding one, than a distinct 

 and separate tooth. 



In the left valve there is no lateral tooth, and of the 

 three primary ones, the front is short and rather divergent, 

 the middle one, which is nearer to the former than to the 

 succeeding, is long and bifid, and the posterior is produced 

 oblique and very narrow. 



The Iceland specimens which have been held distinct 

 by one of our most eminent Conchologists, who has conse- 

 <|uently reserved the specific name Islandica for them 

 alone, appear to us not to differ from the British examples 

 in essentials, but only in such points as are invariably sub- 

 ject to modification through difference of climate. Their 

 form is rounder, their hinder dorsal edge more sloping, and 

 somewhat convex at its extremity, which almost or entire- 

 ly destroys the slight angularity observable at the hinder 

 termination of our own specimens ; their epidermis looser, 

 and of a reddish cast. We know not whether these 

 features be permanent or not in this variety, as it is of 

 rare occurrence in the museums of England. The ex- 

 amples still preserved in the cabinet of Linna3us are exactly 

 identical with our British ones. 



This is one of our largest shells, measuring occasionally 

 four inches and a half in breadth, and an inch more in 

 length (Brown) ; the ordinary size is not, however, beyond 



