432 MOLLUSCA. MACTRADiE. Amphidesma. 



465. A. compressum. — Triangularly ovate, compressed, 

 rounded at both extremities. 



Concha tenuis, List. An. Ang. 174. Conch, t. cclii. f. 88. — Venus borea- 



lis, Penn. Brit. Zool. iv. 1)6 — Tellina plana, Dmi. Brit. Shells, t. lii. 



f. 1. — Ligula compressa, Mo?it. Test. Brit. 9G — Listera compressa, 



Turt. Biv. Brit. 51. t. v. f. 1. — In the naud of estuaries. 



Length 1/gth, breadth 2 /jjth inches; thin, translucent, yeUowish-white, 



finely but irregularly striated by the lines of growth ; beaks very small ; a 



single tooth in one valve locking into a bifid tooth in the opposite, adjacent 



to the ligament. 



466. A. declive. — Compressed, oval-oblong, angular, trun- 

 cate;, and open retrally. 



Mya declivis, Mont. Test. Brit. t. i. f. 2 — Anatina declivis, Tnrt. Biv. 

 Brit. 47 — Torbay, Dr Turton. 

 Length 1, breadth 1^ inches ; slightly compressed, white, minutely sha- 

 greened, beak nearest the retral extremity ; anteal extremity broad, round- 

 ed. This species nearly resembles the A. pubescens, but is distinguished, ac- 

 cording to Dr Turton, " by the large oval pi-ojecting teeth, which extend 

 forwards, and have no lateral attachment." 



467. A. 2J^^i^'>^ue. — Shell slightly compressed, transversely 

 ovate, and rounded at both extremities. 



Mya praetenuis, Pult. Dorset. 28, Mont. Test. Brit. 41 — Anatina 

 prset. Turt. Biv. Brit. 48. t. iv. f. 4 — Southern shores of England. 

 Length 1 inch, breadth 1^ ; rough, retral extremity longest. It is distin- 

 guished from the preceding by its rounded retral extremity. 



468. A. distortum. — Convex, suborbicular, wrinkled. 



Mya distorta, Mont. Test. Brit. 42. t. i. f. 1.— Anatina dist. Turt. Biv. 

 Brit. 48. t. iv. f. 5. — In crevices of rocks, rare. 



Diameter nearly an inch ; variable in form from confined situations in 

 which it occurs ; rough, wrinkled by the layers of growth ; distinguished 

 readily from the preceding by the rounded projecting support for the liga- 

 ment. 



** Hinge, with a lateral tooth on each side, in one of the 



valves. 



469- A. prismaticum. — Transversely oblong, rounded an- 

 teally, pointed retrally. 



Mya prismatica, Laskey, Wern. Mem. i. 377- Mont. Test. Brit. Sup. 

 23. t. xxvi. f. 3.— A. prism. Turt. Biv. Brit. 52. t. v. f. 3 — Sandy 

 bays. 

 Length half an inch, breadth an inch ; thin, transparent, glossy, and iri- 

 descent ; obsoletely striated concentrically, ventral margin slightly rounded ; 

 a single erect tooth in both valves, with corresponding pits for their recep- 

 tion. A specimen, presented to me by Mr Laskey, by whom the shell was 

 first discovered, is greatly more obtuse at the retral extremity. 



470. A. album. — Transversely ovate, subtriangular ; round- 

 ed at both ends, the beak nearest the retral extremity. 



