AST ARTE. 123 



slitrlit anterior incurvation iiist in front of tlio beaks, so that the an- 

 terior end is broadly and uninterruptedly rounded ; the interior is 

 cretaceous, and the surface sometimes nearly smooth ; at others hav- 

 ino; more or less remote rather laro-c waves over some part of the 

 disk ; in A. lactea the shell is more solid, the anterior dorsal margin 

 excavated so as to make the anterior end much more acute than the 

 posterior; the beaks are elevated, the hinge very robust, the interior 

 ivory-like (though a little bluish), more uniformly covered with 

 • finer ridges. It is sometimes rather tumid and again very much 

 compressed. Very many forms occur, and, like Sowerby, one feels 

 compelled to admit each one as a species, or unite them in one. 



Astarte quadrans. 



Fig. 48. 



Shell triancrular, slightly oblique, anterior part longest ; surface smooth ; epider- 

 mis yellowish-olive; hinge with a marginal tooth on the anterior margin. 



Astarte quadrans, Gould, Invert. 1st eel. 81. — Sowerby, Thesaur. ii. 782, pi. 167, fig. 

 ^. — Stimpsox, Shells of New England, 18. 



Shell small, triangular, solid, nearly equipartite, dorsal margins 

 bounded by straight lines, the anterior somewhat longer and more 

 oblique than the posterior ; basal edge very sharp and 

 regularly rounded, so that the whole shell is nearly a ^'"- ^^'^• 

 quadrant ; beaks pointed, and not inclined to either side, 

 generally eroded ; lunide lance-shaped, slightly impressed, 

 and a broader and longer areola behind the beaks ; sur- ^ uadrans 

 face smooth, very slightly wrinkled by the lines of growth ; 

 epidermis light yellowish-olive ; interior glossy bluish-white ; hinge- 

 margin narrow, with a small lateral tooth on the left valve, about 

 half-way along the anterior margin, and a groove to receive it on 

 the right valve ; muscular impressions rather shallow ; inner mar- 

 gin not crenulated. Length, nine twentieths of an inch ; height, 

 eight twentieths of an inch ; breadth, two twentieths of an inch. 



Several specimens of this small and very distinct species have 

 been furnished me for description by Dr. Prescott of Lynn, and by 

 Dr. D. H. Storer of Boston. They were taken from the stomachs 

 of fish caught in Massachusetts Bay. Laminarian and Coralline 

 Zone, from Stonington to Casco Bay ; on a stone, St. George's 

 Baiik ( Stimpson) ; Eastport, one dead ( Cooper^ ; Salem Harbor, 

 in f jur fathoms, white sand ( Wheatland and Stimpson} ; Grand 

 Maiian, rarely (^Stimpson). 



