154 WORMS. TESTACEA. 40. Mac'ra. 



grooves; the margin slightly crenate : beak central, pointed, turn- 

 ing to one side. 



235. C. corneum. Suborbicular, convex, thin, pellucid, 

 with fine concentric striae, one of which is Very dis- 

 tinct. 



2. Twice as large, without the prominent groove. 

 Br. Zool. t. 49./. 36, Donov. t. 96. Tellina. 



Shell about 4 lines long and fomewhat broader, white or bluish, 

 often covered with a horn-colour skin, within bluish-white, with 

 tranfverfe black curves, one of which is more distinct ; beak cen- 

 tral, obtufe : primary -teeth hardly any ; lateral-ones remote, 

 laminate. 



236. C. amnicum. Oblique, suboval, convex* somewhat 

 pellucid, transversely grooved. 



Don. t. 64,/. 2. Linn. Trans, iii. t. 13./. 37. 38, Tellina. 



S/te//f mailer than the last, horn-colour, with the beak placed near 

 one side : teeth one in one valve with 2 lateral ones, in the other 

 2, oblique, with a single lateral-one. 



237. C. lacustre. Subrhonibic, thin, pellucid, smooth, 

 flattish, with an acute projecting beak. 



Chemn.Conch. vi. t. 13/. 135. Tellina. 



Shell 3 lines long, 4 broad, greyish-brown with a white margin, 

 rather compressed : beak central, very prominent : teeth one in 

 each valve, one of which is cloven, with a lateral tooth each side,. 

 and 2 minute laminae in one valve. 



40. MACTRA. 



938. M. solida, Sfrong, opake, slightly triangular, with 

 a few concentric ridges and zones. 



Br. Zool. t. 51./. 43. A. Donov. t.61. Da Cost. t. 15./. 1. 



Shell an inch and a half long, an inch and 3 quarters broad, yel- 

 lowish-white with often yellow or bluish bands, glossy-white 

 within, equal at the sides: beak central. 



239. M. subtruncata. Strong, subtriangular, yellowish- 

 white, transversely striate, slightly truncate on both 

 sides. 



Donov. t. 126. Br. Zool. t. 52./. 42. M. Stultorum. 



Shell 3 quarters of an inch long* an inch broad, a little produced 

 on one side, with fometimes a few ridges, yellowish-white within, 

 the sides near the beak much turned in : beak large, prominent. 



240. M. Stultorum. Thin, semipellucid, faintly striate, 

 slightly triangular, pale rufous with lighter radia- 

 tions, within pale purple. 



Donovan t. 106. Br. Zool. t. 49./. 30. Tellina.. 



Shell an inch and a half long, an inch and 3 quarters broad, 

 yearly equal at the sides, often covered with a thin skin, irregu- 

 larly radiate with broad and narrow whitish lines : beak central, 

 prominent, often purplish. 



241. M. radiata. Thin, brittle, somewhat triangular, 

 produced at one end, whitish with regular pale testa- 

 ceous rays. 



Donovan Brit. Shells, v. tab. 161. 



Shells, inches and a half long, nearly 3 wide, thin, brittle, dirty 

 white with a dull rufous tinge, and radiate with numerous equi- 

 distant narrow teftaceous rays, finely striate tranfverfcly : beak 

 prominent, rather oblique. 



242. M. dealbata. Oval, thin, brittle, pellucid^ white, 



