CONCHIFERA. 



273 



foot, a light green glutinous matter was poured out with 

 such rapidity that in less than five minutes the animal was 

 fixed. When detached it opened its valves, laying them 

 on each side nearly flat, and marched across the saucer by 

 means of its foot with such rapidity that ten could scarcely 

 be counted : it seemed to be considerably assisted by the 

 large margins of the mantle." M. Mittre states that it 

 lives on the roots and leaves of fuci at a depth of three to 

 four fathoms, and looks like beautiful pearls when seen 

 beneath the water.* 



Family 13. — AST ART ACE A. 



The animal has an almost entirely cloven mantle with 

 only one opening for the passage of the water, &c. ; the 

 foot hatchet-shaped, and no byssus. The shell is round, 

 slightly triangular, perfectly closed, the hinge teeth two 

 in each valve, with sometimes indications of lateral teeth ; 

 generally an external ligament, and the pallial impression 

 has no sinus. — Marine. 



Astarte. Low. (Tridonta Schum. ; Crassina Lam. ; 

 Nicania Leach ; Goodallia Turton ; 

 Mactrina Brown ; Thetis Adams.) 

 — Shell equivalve, inequilateral, 

 nearly orbicular, but somewhat 

 transverse ; two diverging teeth in 

 the right valve, with one distinct, 

 and one obsolete tooth in the left ; 

 covered with a brown epidermis; 

 one of the muscular impressions 

 is divided into two ; ligament external ; there is no sinus 



* Forbes's British Moll. 

 T 



