136 MACTRA. 



Inhabits the coasts of Tranquebar, and the Nicobar Islands. 

 Chemnitz. 



Shell about ten lines long and twelve broad, and is of the same 

 colour, and striated in the same manner as M . violacea ; from 

 which it differs not only in its much smaller size, but also in 

 having the anterior end abruptly truncated, and the margin 

 crenulated on the inside. 



rotundata. 11. Shell triangular, somewhat round- 

 ed, narrower at the anterior end, and trans- 

 versely striated, except at the margin. 



Mactra rotundata. Gmelin, p. 3257. 



Mactra, No. 16. Schroeter Einl. iii. p. 87. t. 8. f. 1. 



Lister Conch, t. 263. f. 99- 



Inhabits 



Schroeter, on whose authority this species rests, describes it to 

 be an inch and a quarter long, and an inch and three-quarters 

 broad, and to be nearly allied to M. glabrata, but more 

 rounded, and narrower at the anterior end ; the colour 

 whitish, with the umbones violet, marked with a white band, 

 and the anterior slope and margin also tinged with violet. 



glabrata. 12. Shell glabrous, thickish, diaphan- 

 ous, with the umbones very smooth, and both 

 the slopes striated. 



Mactra glabrata. Linnaus Syst. Nat. p. 1125. Schroeter 



Einl. iii. p. 75. Gmelin, p. 3258. 

 Mactra polita. Chemnitz, vi. p. 222. t. 22. f. 2 16 and 217. 

 Gualter, t. 71. f. A. 



Inhabits the African Ocean. Linnaus. Coasts of Tranquebar. 

 Chemnitz. 



Shell an inch and a half long, and two inches broad, somewhat 

 shining, and transversely striated, except towards the um- 

 bones, which are perfectly smooth ; the ■ outer surface is 

 fawny white, and the inside white, with two or three large 

 purple stains. 



nitida. 13. Shell glabrous, thick, diaphanous, 

 smooth, with both the slopes striated, and 

 the anterior one distinctly keeled. 



Mactra nitida. Schroeter Einl. iii. p. 88. t. 8. f. 2. Gme- 

 lin, p. 3258. 



Inhabits 



This species rests on the authority of Schroeter, who describes 



