TRIBE MACTRACEA. 41 



by age, margin rounded, tawny brown, with curved wrinkles. — 

 Variety. (U. Transversa. Lam. 2.) — Broader than long. ], — 

 Senegal. — The muscular impressions very elongated, straight and 

 resembling those oj" the genus Lucina, united by a simple palleal scar, 



solp:mya. 



Ineqtdlateral, equivalve, transversely elongated, extremities obtuse, 

 with the epidermis smooth, shining, and projecting ; beaks not 

 prominent and hardly distinct ; a dilated, compressed, oblique 

 cardinal tooth i?i each valve, slightly concave above for the re- 

 ception of the ligament ; ligament partly external and partly 

 internal. 



S. AusTRALis. Lam. 1. — Bl. t. 7^. f. 1. Oblong, brown, 

 shining, rayed ; valves notched near the beaks, 1 f . — New Holland. 



S. Mediterranea. Lavi. 2. — Sow. G. — W. S.f. 1. — Poll. 

 1. t. 15./. 20.— E. t. 22b. f. 4.— Reeve, t. 29. /. 1. Oblong, 

 brown, shining, rayed with yellow ; beaks not cleft, no callous sup- 

 ports to the cartilage. H. — 3Jediterranean. 



S. BoREALis. 2'otten. Sil. J. 26. p. 366. f. 1.— S. Velum. 

 Conrad. Am. Mar. C. t. 66. f. 16.— Gould. 3Ias,p 36. Fragile, 

 oblong : epidermis dark brown with fifteen to twenty lighter I'adiat- 

 ing lines : within grayish-blue, cartilage support forked, the anterior 

 branch directed obliquely hindwards. — N. America. — No Jissure 

 at the beaks. 



S. Velum. Say. Journ. A. N. S. Phil. 2. p. 3\7.—Gotild. 

 3Ias. p. 35. Oblong, very thin, dorsal and ventral edges straight 

 and parallel, rounded at each end, rather longer posteriorly, rayed 

 with about fifteen double lines which are sparse about the middle of 

 the shell, the cuticle pale yellowish-brown : inside purplish-white ; 

 the hinge without teeth, with a slightly prominent cartilage, and an 

 internal elevated cartilage support, which is arched and the points 

 directed across the shell, ''^h''^'~ ^* Sf(ff<^s. 



AMPHIDESMA. 



Inequilateral, transverse, sub-oval or somewhat rounded; with 

 the sides slightly gaping ; hinge with one ur two cardinal teeth, 

 and a narrow groove for the internal ligament ; ligament doiible, 

 the external one short, the internal one Jixed in the internal 

 grooves.- 

 A. Variegatum. Lam. \.—E t. 291. /. 3.— Sow. G. f. 1. 



—An. Tel. osLiauA.a Wood. G. C. t. 41. /. 1, 2.?— />. 



2 A. Donacillum. Lam. 2, Corneum 4, Glabrellum 13, are 

 described under Mesodesma. A. Lacteum 3, and Lucuiale 6, under 

 Lucina. 



^ We have copied this figure. 



