TRIBE MACTRACEA. 4\ 
by age, margin rounded, tawny brown, with curved wrinkles.— 
Variety. (U. Transversa. Lam. 2.)—Broader than long. 1.— 
Senegal.— The muscular impressions very elongated, straight and 
resembling those of the genus Lucina, united by a simple palleal scar. 
SOLEMYA. 
Inequilateral, equivalve, transversely elongated, extremities obtuse, 
with the epidermis smooth, shining, and projecting ; beaks not 
prominent and hardly distinct ; a dilated, compressed, oblique 
cardinal tooth in each valve, slightly concave above for the re- 
ception of the ligament ; ligament partly external and partly 
internal. 
S Ausrrauis. Lam. 1.—Bl. t. 79. f. 1. Oblong, brown, 
shining, rayed ; valves notched near the beaks. 13.—New Holland. 
S. MepirerrAaNeA. Lam. 2.—Sow. G.—W. 8S. f. 1.—Poli. 
1.4.15. f. 20.—E. t. 225. f. 4.—Reeve. t. 29. f. 1. Oblong, 
brown, shining, rayed with yellow ; beaks not cleft, no callous sup- 
ports to the cartilage. 14.— Mediterranean. 
S. Borgauis. Totten. Sil. J. 26. p. 366. f. 1.—S. Vetum. 
Conrad. Am. Mar. C. t. 66. f. 16.— Gould. Mas. p 36. Fragile, 
oblong: epidermis dark brown with fifteen to twenty lighter radiat- 
ing lines: within grayish-blue, cartilage support forked, the anterior 
branch directed obliquely hindwards.—N. America.—No fissure 
at the beaks. 
S. Vetum. Say. Journ. A. N.S. Phil. 2. p. 317.—Gould. 
Mas. 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. 7,4°9.— U. States. 
AMPHIDESMA. 
Inequilateral, transverse, sub-oval or somewhat rounded ; with 
the sides slightly gaping ; hinge mith one or two cardinal teeth, 
and a narrow groove for the internal ligament ; ligament double, 
the external one short, the internal one fixed in the internal 
grooves.* 
A. VarieGAtuM. Lam. 1.—E. t. 291. f. 3.—Son. G. f. 1. 
—An. TEL. optiqua.2 Wood. G. C. t. 41. fi 1, 2.?—D. 

2 A. Donacillum. Lam. 2, Corneum 4, Glabrellum 13, are 
described under Mesodesma. A. Lacteum 3, and Lucinale 6, under 
Lucina. 
3 We have copied this figure. 
