TRIBE MYTILACEA. 237 
end very obtuse, its edge sloping very obliquely to the ventral 
margin; umbones very wide, beaks touching and subterminal. 
Tonga.—1. . 24. 
M. Traresina. Lam. 17.—Del. t. 13. f. 7. Ovate-subtrapezi- 
form, moderately ventricose, thin, smooth, whitish under a yellow 
cuticle ; beaks touching, oblique; ligamental edge convex, slightly 
raised: ventral incurved near the posterior termination (which is 
much compressed) and almost forming a rectangle with it. 2.. 1. 
Cape of G. Hope.? 
M. Puicata. Lam. 20.—Mytitus P. Gmel. 3356.—D. p. 306.— 
W. t. 12. f. 14.—Ch. f. 733.—E. t. 221. f. 3. Rhomboidal, very 
thin, transparent, pale fulvous, rounded posteriorly, dilated and an- 
gulated anteriorly, transversely striated, with concentric pliciform 
wrinkles on the anterior extremity: beaks rather prominent and 
inflected ; silvery within. 2..14.—/icobar Isles. 
M. Exoneata. Swainson, Ex. Con. 2nd Ed. p. 31. t. 8. Trans- 
versely elongated, subrhombic, subcylindraceous, the dorsal edge 
quite straight, anteriorly rather elevated, depressed and angulated 
so as almost to appear auriculated ; white under a rich yellowish 
chesnut glossy smooth cuticle, a few transverse striz at the rounded 
and attenuated posterior extremity ; umbones broad, touching and 
much incurved. 
M. Arporescens—Myrtitus A. Ch. f. 2016, 7.—D. p. 306.— 
Wt. 12.f. 13.—M. Picra. Lam. 8.—Sow. G.—Reeve Sys. t. 100 
f. 1—E. t. 221. f. 2. Subcylindrical, thin, becoming but slightly 
broader anteriorly ; ligamental edge very long, scarcely at all raised ; 
the ventral not incurved, nearly straight; cuticle pale yellow, divi- 
ded diagonally into two portions, of which one is plain and the 
other ornamented with minute blackish or dark brown irregularly 
branched lines. 1..24.—W. Indies. 
M. Castanea Gray Ann. Phil. 25.—W. 8S. 2. Myv. f. 2.— 
Rump. t. 46. f. E.—List. t. 1055. f. 9—M. Stricuta. Sow. G.— 
Reeve Sys. t. 100. f. 2. Closely allied to Vagina, but altogether 
larger, much broader and when full grown by no means dilating 
anteriorly as in that species, the ventral edge being all but straight 
and subparellel to the dorsal in the adult; cuticle rich chesnut. 
2..33.—Amboyna, Philippines. 
M. Cunrirormis. Nobis Zool. P. 1844. Elongated, wedge- 
shaped, moderately ventricose, thin, smooth, yellowish chesnut 
with a very indistinct paler ray running along the posterior side of 
the umbonal ridge; posterior side narrow, rounded and very short ; 
dorsal edge elevated, straight, very elongated, forming an angle 
with the nearly straight anterior margin, which slopes suddenly to 
the compressed and rounded anterior extremity: ventral edge 
scarcely incurved ; beaks narrow: inside nacreous white. 14..4. 
Philippines. 

