TRIBE MYTILACEA. 237 



end very obtuse, its edge sloping very obliquely to tbe ventral 

 margin ; umbones very wide, beaks touching and subterminal. 

 Tonga.— \..2\. 



M. Trapesina. 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. ^. . 1. 

 Cape of G. Hope.? 



M. Plicata. Lam. 20.— Mytilus P. Gmel. 3356.— D.p. 306.— 

 W. t. 12. /. 14.— Ch.f. 733.— E. t. 221. /. 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, f. . lj. — Nicobar Isles. 



M. Elongata. 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 striae at the rounded 

 and attenuated posterior extremity ; umbones broad, touching and 

 much incurved. 



M. Arborescens— Mytilus A. Ch.f. 2016, 7.— D.p. 306.— 

 W. t. 12./. 13.— M. Picta. Lam. S.—Sow. G.— Reeve Sys t. 100 

 f. 1. — E. t. 221. /. 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 . . %\. — W. Indies. 



- M. Castanea Gray Ann. Phil. 25.— W. S. 2. Myt. f. 2.— 

 Bump. t. 46./. E.—List. t. 1055./. 9.— M. Silicula. Sow. G.— 

 Reeve Sys. t. 100./. 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 . . 3|. — Amboyna, Philippines. 



M. Cuneiformis. 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. 1 J. .4. 

 Philippines. 



