TRIBE MACTRACEA. 33 



M. Elegans. Sow. Tank. Cat. t. 1. f. 3. — Desk, in Lam. 6. 

 p. 1 07. Rounded triangular, the hinge margin nearly forming a right 

 angle at the beak, whilst the ventral margin is all but a semicircle, 

 tumid, thin, anterior slope sharply carinated ; yellowish white, with 

 rounded concentric grooves : lateral teeth short small and approxi- 

 mate. — Florida. A more rounded and tumid shell than Plicataria. 



M. Yitrea. Gray. Mag. N. H. 1837. Oblong trigonal, thin, 

 white, pellucid, umbones incurved, sub-anterior ; posterior slope 

 flattened, edge waved : anterior slope compressed, its depression 

 elongated, with a slight riblike raised edge ; lunule depressed, lan- 

 ceolate : lateral teeth short, very small, and very approximate. 1£. 



M. Cygnea. Chem.f. 207—&. p. 134.— M. Cygnus. Gmel. 

 3260. — W. t.6.f. 6. Ovate triangular, ventricose, slightly wrinkled 

 transversely, solid, whitish, and anteriorly obliquely truncated : the 

 posterior slope heart-shaped and finely striated : umbones close : 

 lateral teeth smooth. \±. — China, 



M. Exoleta. Gray. Mag. N. H. 1837. Trigonal, white, 

 thin, pellucid, slightly striated concentrically, covered with thin 

 pale periostraca ; posterior slope compressed, produced, anterior 

 slope ventricose, flattened, edged with a slightly raised keel : ante- 

 rior lateral teeth very small and close, the posterior one elongated. — 

 Cape Horn. 



M. Discors. Gray. Mag. N. H. 1837. Ovate, trigonal, 

 rather solid, ventricose, white ; umbones nearly close, with two 

 diverging reddish lines ; anterior depression rather flattened, rugu- 

 lose, margined by slightly raised lines, with two or three raised con- 

 centric ones : lunule concentrically grooved : lozenge, smooth ; lateral 

 teeth subequal and moderately distant. 



M. Reevesii. Gray. Mag. N. H. 1837. Wedge-shaped, 

 thin, white, pellucid, striated concentrically : curved near the umbo : 

 lateral teeth subequal, rather long and approximate : hinge margin 

 two-edged. — China. 



M. Elongata. Quoy. Ast. t. f. Oblong-ovate, rather 

 solid, smooth pale brown, covered with a rather thin olive epidermis : 

 anterior slope slightly rugulose : lateral teeth close, rather short, 

 the posterior one notched, the other sub-triangular. 1^. — New 

 Zealand. 



M. Similis. Gray, in W. S. t. 1. f. 5. — Spisula S. Gray. 

 Mag. Nat. IT. 1837.— Beech. Z. t. 44. f. 8.— M. Ovalis. Gould. 

 p. 53 1 (fide Gould.) Oblong ovate, rather thin, pale reddish 

 white under an olive epidermis : anterior slope slightly indicated : 

 lateral teeth short, triangular, close. 2.. 3. — Van Diemen's Land. 



M. Aspersa. Sow. Tank. Cat.—M. Tenera. W. S. t. l.f. 

 4. Oblong, compressed, inequilateral, rather solid, smooth, but 

 slightly rugulose on the anterior slope, and the posterior concen- 

 trically grooved : white, speckled with dark chesnut. 2. 



