MACTRA. 143 



ing remote and lamellated lateral teeth in one valve ; and from 

 the young of the other preceding species, by its having none 

 in the other valve. 



boys ii. 28. Shell subtriangular ovate, compressed, 

 and glabrous ; hinge with lateral teeth in only 

 one valve. 



Mactra Boysii. Montagu Test. p. 98. t. 3. f. 7. Maton 

 and Racket, in Lin. Trans, viii. p. 72. Dorset Cat. p. 

 33. t. 12. f. 7. 

 Mactra alba. Wood, in Lin. Trans, vi. p. 165. t. 18. f. 9 

 to 12. 

 Inhabits the coasts of Britain. Wood, fyc. 

 Mr. Montagu describes this shell to be rather more than half an 

 inch long, and three quarters of an inch broad, but it is 

 commonly much smaller ; it is thin, pellucid, glossy, and 

 white, marked only with a few distant obsolete concentric 

 striae; the hinge is placed considerably nearer the posterior 

 than the anterior end, and has broad elevated lateral teeth 

 in one valve. 



triangularis. 29. Shell sub-triangular, minute, 

 strong, opake, with the umbones prominent, 

 and the margin crenated. 



Mactra triangularis. Montagu Test. p. 99. t. 3. f. 5. Ma- 

 ton and Racket, in Lin. Trans, viii. p. 72. 



Inhabits the coasts of the West of England. Montagu. 



Shell one eighth of an inch long, and the length rather exceeds 

 the breadth ; strong, opake, white, with the umbones ob- 

 tuse and prominent, and the margin strongly crenated ; Mr. 

 Montagu says the hinge has a large bifid tooth in one valve, 

 with two small ones separated by a triangular cavity in the 

 other valve, and depressed lateral teeth. 



MiNUTissiMA. 30. Shell sub-triangular, minute, 

 with the umbones prominent, and the mar- 

 gin entire. 



Mactra minutissima. Montagu Supp. p. 37. 



Inhabits the sea in corallines. Montagu. 



Mr. Montagu says this is one of the most minute of bivalve 

 shells, and might easily be mistaken for M. triangularis, was 

 it not for the margin in that species being crenated ; it is, 

 however, not quite so angulated, nor so long in proportion to 

 its breadth, nor has it ever occurred so large as that shell. 



