164 MYAD^. 



vi. p. 8, pi. 1, f. 1,2. — Spengl. Skrivt. Naturh. Selskab. vol. 

 iii. p;irt 1, p. 28. — "Wood, General Conch, p. 90, pi. 17, f. 1, 

 2. — DiLLW. Recent Shells, p. 42 — Lam. Anim. s. Vert. ed. 2, 

 vol. vi. p. 73. — Burrows, Conch, pi. 4, f. 1, 2. — Ind. Testae, 

 pi. 2, Mya f. 2.— Crouch, Introd. Conch, pi. 3,f. 6, 7.— Sow. 

 Conch. Manual, f. 71.— Desh. Elem. Conch, pi. 8, f. 2.— 

 Hanl. Recent Shells, p. 19, pi. 2, Mya f. 2.— Gould, Invert. 

 Massac, p. 42.— Dekay, New York Mollusc, p. 240, pi. 29, 

 f. 289. 



C/iama truncaia,!) A Costa, Brit. Conch, p. 233, pi. 16, f. 1. 



Afi/a ovalis, (immature.) Turt. Dithy. Brit. p. 33, pi. 3, f. 1, 2. 



Spluznia Stvainsoni, (fry.) Turt. Dithy. Brit. p. 37, pi. 19, f. 2.— Flem. Brit. 

 Anim, p. 466. — Brit. Marine Conch, p. 57. 



Myc ironqute, Chenu, Trait6 Elem. p. 48, f. 152. 



Ency. Meth. Vers. pi. 229, f. 2. 



This Jincient and well-known shell is of a sub-oval form, 

 which is at times produced, but more generally abbre- 

 viated, subequilateral, more or less solid, opaque, and ven- 

 tricose. This latter characteristic is, however, chiefly- 

 manifested towards the rounded end, there being a con- 

 siderable degree of flattening of the central surface, which, 

 after a slight retusion, again swells out at the truncated 

 tips of the posterior extremity, of which latter the hiatus is 

 extremely large, more or less oval in shape, and not ex- 

 tending below beyond the ventral margin ; the lips of this 

 gape are reflexed, and there is not any tendency to stric- 

 ture. A loose, yellowish-grey epidermis (which is con- 

 tinued posteriorly beyond the shell to the animal,) covers 

 the entire valves, which beneath it are of a more or less 

 squalid dull uniform white, and concentrically traversed by 

 irregular but very distinct wrinkles, which are often almost 

 pliciform at the sides, where they are always most deve- 

 loped. The dorsal and ventral margins are almost parallel; 

 the latter is more or less straight, a little refuse at or be- 

 hind the middle, more convex in front, and more ascending 

 posteriorly. The former, immediately adjacent to the um- 

 bones, is subrctuse in front, and not at all declining ; but, 



