MACTRA. 139 



more than an inch ; it is a thin shell, of a pale reddish or 

 greyish brown colour, marked with whitish longitudinal rays, 

 which vary in breadth ; the hinge is central, with the 

 anterior slope gibbous, and the posterior produced, and 

 somewhat keeled in the middle ; the inside is always either 

 pale or dark purple. 



grandis. 19. Shell sub-triangular, diaphanous, 

 smooth, obsoletely radiated, with the hinge 

 not central, and the anterior end somewhat 

 produced. 

 Mactra grandis. Gmelin, p. 3259. 

 Mactra stultorum Var. Solander's MSS. 

 Mactra, No. 8. Schroeter Einl. iii. p. 84. 

 Mactra cinerea. Montagu Supp. p. 35. ? 

 Chemnitz, vi. p. 229- t. 23. f. 22S. 



Inhabits the coasts of New Jersey. Solander. 



Shell two inches and a quarter long, and three inches and, a 

 quarter broad, and differs from M. stultorum, not only in 

 its larger size and greater proportionate breadth, but also in 

 having the hinge placed rather nearer the posterior than the 

 anterior end, and the latter somewhat angulated and produced ; 

 it is of a light fawn colour, semi-transparent, marked with pale 

 longitudinal rays, and the inside has only a slight tinge of 

 purple. Mr. Montagu describes his M. cinerea, to differ 

 from M. stultorum, in having the valves more convex and 

 angulated, and adds, without mentioning the size, that they 

 are broader in proportion to the length. 



achatina. 20. Shell somewhat heart-shaped, very 

 smooth, radiated towards the margin, and 

 marked with two violet spots on the anterior, 

 and two on the posterior slope. 



Mactra achatina. Chemnitz, xi. .p. 218. t. 200. f. 1957 

 and 1958. 



Inhabits the coasts of Tranquebar, Ceylon, and the Nicobar 

 Islands. Chemnitz. 



Shell about an inch long, and an inch and a quarter broad, and 

 is variegated with whitish and pale brown, forming longitu- 

 dinal rays towards the margin, and spots towards the hinge ; 

 there are two distinct dark violet spots on the anterior, and 

 two on the posterior slope ; Chemnitz says, it has the habit 

 of a Venus, with the hinge of a Mactra. 



