TRIBE MACTRACEA. 33 



M. Elegans. Sow. Tank. Cot. t. 1. /. 3. — Desk, in Lam. G. 

 •p. 107. 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 moi-e rounded and iumid shell than PUcataria. 



M. ViTREA. Grai/. 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.— -D. p. 134.— M. Cygnus. Gmel. 

 3260. — W. t. 6. /. 6. Ovate triangular, veutricose, slightly wrinkled 

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

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

 lateral teeth smooth. 14. — China. 



M. ExoLETA. Graij. Mag. N. II. 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 latei'al teeth very small and close, the postei'ior one elongated. — 

 Cape Horn. 



M. DiscoRS. Gray. ISIag. N. II. 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. 3Iag. 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. I. f. 5. — Spisula S. Gray. 

 Mag. Nat. H. 1837.— Beech. Z. t. 44./. 8.— M. Ovalis. Gould, 

 p. 53? C/ide Gould.) Oblong ovate, rather thin, pale reddish 

 white under an olive epidermis : anterior sloj^e slightly indicated : 

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



M. AspERSA. &om. Tank. CaL—M. Tenera. W. S. t. \. f. 

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

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

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



