SOLEN. 



Another circumstance which induces us the more 

 readily to adopt this view, is, that the teeth in these, 

 which may be not improperly termed typical species, are 

 so variable that no dependance can be placed on them for 

 generic characters, almost every species being different. 

 It is remarkable that typical species of this genus are found 

 in all parts of the world, and that the resemblance between 

 those which inhabit the shores of Europe, South America, 

 and Australia, is so great that it is difficult to point out 

 good distinguishing characters. Several species are com- 

 mon on the coasts of Britain, of these the SiUqua grows 

 to the length of more than ten inches in the neighbourhood 

 of Belfast. The animal is remarkable for an enormous 

 muscular foot which probably aids it in burrowing in the 

 sand, which it frequently does to the depth of two feet in 

 a perpendicular direction, and it seems to take its station 

 habitually near the upper extremity of its hole, and upon 

 the slightest disturbance it retreats with amazing rapidity 

 to the lower end. 



Very rarely found in a fossil state in the Calcaire 

 grossier, and in the London clay. 



