432 MOLLUSCA. MACTRAD^E. 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. 96 — Tellina plana. Bon. 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 1/oth, breadth 2x^gth 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 inches ; slightly compressed, white, minutely sha- 
green ed, beak nearest the retral extremity ; anteal extremity broad, round- 
ed. This species nearly resembles the A. puhescens., but is distinguished, ac- 
cording to Dr Turton, “ by the large oval projecting teeth, which extend 
forwards, and have no lateral attachment.” 
467. A. prcetcnue.—~^\\e\\ slightly compressed, transversely 
ovate, and rounded at both extremities. 
Mya prsetenuis, 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 4 ; rough, retral extremity longest. It is distin- 
guished from the preceding by its rounded retral extremity. 
468. A. 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, hi 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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