358 INTRODUCTION TO CONCHOLOGY. 



and the ligament is external; in some instances a fixed 

 testaceous appendage^ called the fulcrum, is obvious under 

 the umbo of each valve. There are eight genera — Solerij 

 Soleciu'tus, PanojJcea, GlycimeriSj Solemya^ Solenella, Glau- 

 conome, and Fholadomya. 



The animal inhabitant of the Solen^ though incapable 

 of moving forward horizontallj, digs a hole nearly two feet 

 deep in the soft sand, into which he can descend at 

 pleasure. This is effected by means of a fleshy and cylin- 

 drical leg, which is capable of being drawn out to a con- 

 siderable length, sharp at one side, terminating in a point, 

 and alternately assuming the shape of a hook and a spade ; 

 one serving the purpose of shovelling out the sand, the 

 other to assist the wary animal in his descent. When the 

 Solen wishes to change his place of abode, the leg is put 

 in requisition, then taking the shape of a ball, it is 

 stretched as wide as possible. The ball prevents the 

 creature from slipping back, while the reaction of the 

 muscles throws him forward. He has, also, a kind of 

 mantle in front, — a curtain before the opening of his cell, 

 which enables him to exclude the rough beating of the 

 tide ; he is furnished, moreover, with two united breathing- 

 tubes, about three or four inches in length, from the upper 



