432 MOLLUSCA. MACTRAD^. Amphidksma. 



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. 96 — Tellina plana, Don. Brit. Shells, t. lii. 

 f. 1. — Ligula compressa, Mont. Test. Brit. 96 — Listera compressa, 

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



Length l T 8 5 th, breadth 2 T 3 s th inches; thin, translucent, yellowish-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, Turt. 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 projecting teeth, which extend 

 forwards, and have no lateral attachment." 



467. A. prcetenue.— Shell slightly compressed, transversely 

 ovate, and rounded at both extremities. 



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

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



Length 1 inch, breadth \\ ; 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. 



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