TRIBE MACTRACEA, 39 
ERYCINA. 
Transverse, sub-inequilateral, equivalve, rarely gaping ; with two 
primary teeth, unequal, diverging, witha pit inter posing ; lateral 

J. 9,0, 1. Crassatenza Ovata. W. S. Mact. f. 11. Ovate-ob- 
long, transverse, subeequilateral, thick, solid, greenish-yellow, 
smooth; interior white, hinge thickened, ligamental pit deep and 
produced at the base, teeth nearly equal. 24.—dustraha? 
M. Donacitia.* Desh.—Ampuipesma D. Lam. 2,—Donax 
Pieper, Mont. t. f. 5. f.2.—D. p. 102.—W. t. 6. f. 10,—Ery- 
cina P. Sow. Gf. 3.— Reeve. t.45. f. 5. Ovate triangular, wedge- 
shaped, smooth, glossy; posterior side very short and obtuse; variable 
in colouring, being sometimes yellow, pale with three or four ches- 
nut or dark rays, and often yellow with a broad central white ray, 
edged with chesnut, inside yellowish. 4.—Mediterranean, Gulf of 
Tarentum. 
M Cornea. Desh.—Amrpnipesma C. Lam. 4.— Del. t. 4. f. 
5. Ovate-triangular, reddish horn-colour, unspotted, posterior side 
very short. 1.—Mauritius 
M. Guasetia. Desh.—AmpuipesmMa G. Lam. 13.—Bl. t. 78. 
J. 6. Suboval, white, semitransparent, small and transversely 
striated ; anterior side the shorter and obliquely truncated. 3. .. $. 
—WNew Holland. 
M. Sotenorpes. Gray.—Erycina 8. King in Z. J.4.—Grif. 
Cuv. mol. t. 22: f. 1. Elongated-subelliptic, thin, obtuse at both 
extremities, and much produced, closely substriated concentrically, 
whitish under a greyish brown epidermis: ligamental pit project- 
ing much below the hinge margin. 44. .2.—S. America. 
M. Arctrata. Gould. Mas. f. 39.—Macrra A. Conr. Jour. A. 
N.S. Phil. 6. t. 11. f. 1.— Reeve. t. 45. f. 3. Wedge-shaped, sub- 
ovate, smooth, thick, compressed; anteriorly very short, obtusely trun- 
niated directly, posteriorly produced with the end margin rounded, 
ventral edge areuated ; cuticle golden yellow, reflecting a metallic 
lustre ; cartilage pit triangular and profound ; lateral teeth striated 
transversely, the posterior one elongated. #4. .1{.—JZassachussets. 
M. Deaurata.—Mactra D. Turt. Biv. ¢t. 5. f. 8. p. 71.— 
Mac. Denticutata. W.S. f. 9.—Grif. Cuv. mol. t. 22. f. 
2.—An. Mes. Jauresit of Mag. de Z. and Gould Mas. Elon- 
gated, wedge-shaped, convex, thick, dirty white with ridges of 
growth under a tawny and hornlike epidermis, which usually reflects 
metallic colours: elongated side rounded, shorter side obtusely, 
but not directly truncated: muscular scars of teeth very strong, 
the latter and their receptacles strongly striated. 
Compare with these the British Donax Castanea (Mont. t. 17. 
f. 2.—D. p. 152.—W. t. 6. f. 10.) which evidently belongs to this- 
genus. We have copied the figure of Montague. 
