. 



Ervii.ia. MOLLUSCA. MACTRAMJ. 431 



Gen.CXVII. ERVILIA. — Shell oval, equi valve, inequilateral, 

 closed ; hinge with a single strong erect cloven tooth in 

 one valve, closing into a deep cleft between two small la- 

 minar divergent elevations in the other, 



— 461. E. nitens. — Beaks prominent, rounded at both extre- 

 mities, regularly and finely striated concentrically. 



Mya nitens, Laskey, Wern. Mem. i. 375, t. viii. f. 4. Mont. Test. Brit. 

 Sup. 165 Ervilia nitens, Turt. Biv. Brit. 5C, t. xix. f. 4 — At Dim- 

 bar, Mr Laskey. 



Length nearly a quarter of an inch, a little more in breadth ; flattish, a 

 little tapering at the longest side ; colour glossy pink ; margin entire. 



Gen.CXVIII. AMPHIDESMA.— Shell inequilateral; hinge 

 with a projection for the support of the internal cartilage 

 in each valve, and one or two small adjacent teeth. 



* No lateral teeth. 



— 462. A. comvexum. — Shell convex, transversely ovate, round- 

 ed anteally, truncate retrally. 



Mya declivis, Don. Brit. Shells, t. lxxxii — Anatina con. Turt. Biv. Brit. 

 44. t. iv. f. 1, 2 — Sandy bays, rare. 



Length l£, breadth nearly 24 inches ; very convex, thin, and brittle, of a 

 rusty white colour ; irregularly wrinkled concentrically, with two or three ob- 

 solete longitudinal folds ; support for the ligament narrow. 



— 463. A. pubescens. — Shell slightly compressed, transverse, 



anteally rounded, retrally broadly truncate ; surface rough. 



Mya pubescens, Pult. Dorset. 27- Mont. Test. Brit. 40 — Anatina pub. 

 Turt. Biv. Brit. 45. t. 4. f. 3 — Southern shores of England. 



Length 2, breadth 2^ inches ; white, the surface of the shell closely cover- 

 ed with minute tubercles, giving it a rough aspect ; slightly wrinkled by the 

 lines of growth, ventral margin and the dorsal one behind the beaks nearly 

 straight, the latter with a contiguous ridge ; support for the ligament broad, 

 with an elevated retral margin. This is probably the Mya declivis of Pennant, 

 Brit. Zool. iv. 7'J. and the young state of which, seems to be the Tellinafra- 

 gilis of the same author, lb. 86. t. xlvii. f. 26. 



464. A. truncatum. — Convex, wedge-shaped, anteal end 



short, obliquely truncate. 



Anatina truncata, Turt. Biv. Brit. 46. t. iv. f. 6. — In cavities of rocks. 

 — Torbay. 



Length J, breadth fths of an inch; rough, striate transversely; anteally, 

 the dorsal margin slopes rapidly, the retral margin is truncate ; the retro- 

 dorsal and ventral margins nearly straight. 



In the three preceding species, the support for the ligament is triangular, 

 and the point of attachment is the centro-umbonal margin ; in the remain- 

 big species, the point of attachment is on the flat surface of the tooth, which 

 is parallel with the mesial plane. 



