356 MACTRID^. 



M. ELLiPTicA, Brown. 



Elliptic, thin, quite smooth, subequilateral ; epidermis glossy ; 

 dorsal areas not grooved ; lateral teeth striated. 



Plate XXII. fig. 3, and (animal) Plate L. fig. 1. 



Mactra elliptica, Brown, Illust. Conch. G. B. p. 108, pi. 41, f. 6. — Forbes, 

 Malacol. Monensis, p. 48. — Macgilliv. Moll. Aberdeen, p. 

 288.— Brit. Marine Conch, p. 244, f. 28.— Loven, Ind. 

 Moll, Skandinavia", p. 45. 

 „ solida (partly), Donov. Brit. Shells, vol. ii. pi. 61, f. 2. 



Mactra elliptica, although bearing a very close resem- 

 blance to M. solida^ may, nevertheless, without any great 

 difficulty, be distinguished from it by its lesser solidity, 

 more produced shape, its comparatively glossy epidermis, 

 and above all by the absence of those regular sulci which 

 invariably roughen the dorsal slopes of the latter species. 

 The shape is elliptical, with a slight tendency in the adult 

 to become trigonal, owing to the greater declination of the 

 dorsal edges in the final stage of growth ; the texture is 

 but moderately solid, and the valves are subventricose in 

 the adult, but simply convex in the young ; the surface 

 is nearly smooth, being free, even upon the dorsal sloj)es, 

 from all regular striaj, sulci, or other sculpture, and merely 

 marked with a few antiquated lines at the stages of in- 

 crease, and sometimes irregular concentric wrinkles and 

 striula) towards the extremities. Beneath the smooth 

 and sometimes glossy epidermis, which in the young is 

 entirely buff-coloured, becoming ashy, except at the 

 margin, in specimens of more advanced age the shell is 

 white. The ventral edge is straightish towards the middle, 

 and convex at each end. The front dorsal edge, whose 

 slope instead of being depressed has its lips peculiarly 

 prominent, is arcuated and moderately declining ; the 

 hinder, which in the young is almost symmetrical with 



