242 TESTACEOUS MOLLUSCA. 



Ovate-elliptical, thin, convex, posteriorly with a few radiating rib- 

 like striae, elsewhere smooth and glossy ; the anterior surface raised 

 and dilated, its end rounded ; cuticle brownish, or yellowish, §. . 1. 

 North Pole — General shape of Impattus. 



M.Discrepans* Gould Mas. p. 129-—TurtBiv. — Mytilus D. 

 Mont. p. 169— D. p. 319— W. t. 12. /. 38. Oval-oblong, com- 

 pressed, greenish fulvous, becoming green at the edges, thin ; an- 

 terior area marked with minute radiating simple striae and elevated 

 as it were above the smooth central surface ; posterior end with a 

 few rather distant radiating grooves, obtuse ; dorsal line elevated 

 and arcuated ; ventral edge with a distinct sinus at the commence- 

 ment of the anterior area, and convex in the middle of the central 

 area, f . — N. Seas. 



M. Nigra.* Brit. Mar. Con. — Mytilus Disckepans. Mont. Sup 

 t. 26./. 4.— Sow. G.f. 3. (good)— Reeve Syst. t. 100. /. S.— Ch.f 

 767. — M. Discors var Suecica Otlio. Fab* Dankse V. S. Sk. 3. 

 (1788.) Oblong or elongated- oblong, arched, rather thin, convex, 

 with a blackish cuticle becoming tawny towards the edges ; anterior 

 half of the shell not elevated but covered with numerous raised 

 subcrenulated sulci, the central area smooth and the posterior end 

 with several radiating costellae, and rather prominent ; hinge margin 

 but slightly elevated, much arcuated ; ventral edge incurved in the 

 middle, dilated anteriorly ; beaks obtuse. 1-^. — Sweden fy Scotland 1 



M. Faba.— Mytilus F. Gmel. 3359.— Ch.f. 761.— W. t. 12. /. 

 41.- — D. p. 320 — Mod. Arctica. Leach m Ross Voy. Roundish- 

 oval, ventricose, white under a reddish or olive cuticle, with rather 

 distant radiating striae : inside pearly, the ventral edge rounded and 

 crenated. J. — N. Seas. 



M. Pectinula Gould Mass. f. 85. Small, ovate, ventricose, 

 with about forty equal rounded radiating ribs : epidermis dark gam- 

 boge yellow ; beaks prominent, projecting as far as the posterior 

 margin : within livid or leaden pearly. \. . T 7 ^. — N. America. 



M. Nexa. Gould. Mass. p. 128./. 86. Small, ovate, thin, rusty 

 brown with shades of olive, sculptured by a network of very mi- 

 nute crowded lines of growth and very numerous fine indented 

 radiating lines which are obsolete in the middle and strongest ante- 

 riorly, where a very fine line divides each into two ; while above 

 these on the compressed portion a beautiful network of hexagonal 

 indentations is formed : beaks prominent and placed considerably 

 before the posterior end : nacre livid, -fa . ,-f-Q. — U. States. 



1 I observed in the Museum at Paris under the name of Depressa 

 a species from Newfoundland, closely allied to this, but quadruple 

 the size, less narrow, the ventral edge scarcely incurved, and the 

 radiating striae distinctly crenulated and infinitely more crowded 

 and delicate. 



