288 



CONCHIFERA. 



Fam. '2. UNIONISE. 



Animal. Mantle lobes free all round except at the 

 back, the hinder edge forming, when in conjunc- 

 tion, two holes, for the passage of the water, food, 

 and rejectamenta, the upper (f. b.) small simple, 

 the lower one (f. a, *, a**) of which is bearded 

 on the edge; foot (f. c.) compressed, ovate, sub- 

 quadrate. 



Shell oblong-elongate, equivalve inequilateral, 

 solid, internally pearly, covered with a hard 

 olive or black horny periostraca ; hinge without 

 any true cardinal teeth, with irregular ante- 

 riors, and long laminar posterior lateral teeth, 

 or toothless ; muscular scars numerous ; ligament 

 and cartilages external, elongate, strong. 



ANODON CYGNEUS. 

 a, Lower siphon ; a*, a**, magnified._6. Upper siphon, c. The foot. 



