CONCHACEA. MOLLUSCA. ASTARTE. 77 



slope nearly straight, with a long, narrow, lanceolate depression ; 

 basal margin regularly rounded, thick ; surface very slightly undu- 

 lated at the stages of growth, covered with a thick, chestnut-color- 

 ed epidermis, wrinkled and stained with black posteriorly, with 

 alternately paler and darker zones ; ligament small and feeble. 

 Hinge very strong, the hinge margin very broad, bearing on the 

 right valve one stout tooth, with a pit on each side ; on the left 

 valve two teeth somewhat diverging, with a deep pit between 

 them for the reception of the opposite tooth ; cavity small ; mus- 

 cular impressions deep, elongated, united by a direct palleal im- 

 pression ; margin in adult shells regularly crenulated. Length 1 

 inch, height 1 inch, breadth |i inch. 



Found abundantly in Provincetown harbour, west and north of 

 the light-house, at low-water mark. Occasionally, specimens are 

 picked up on Chelsea Beach. It is more abundant along the 

 coast of the Middle States. 



The foot of the animal is of a bright vermilion-color, and when 

 seen protruded, one would hardly persuade himself that a red 

 wafer was not embraced by the valves. 



This shell appears to be a well characterized species, quite distinct 

 from any species inhabiting the British coast. The species most 

 nearly allied to it is Venus (Astdrte) compressa, of Montagu. 



Its remarkable points are, its height being usually greater than its 

 length, its prominent central beaks curved so as to give the shell a 

 somewhat kidney-shaped appearance, the broad, excavated lunule be- 

 fore them, and the smooth, chestnut-colored surface. The blackening 

 of the posterior region of the shell is very peculiar. Some specimens 

 look as if this portion had been dipped in tar. 



The varieties in form and coloring are very numerous ; one or two 

 of which may be designated. 



Var. A. picea, is large and solid, surface with a few wrinkles without 

 waves, and the epidermis of a dark tar-color. All the specimens I liave 

 found upon Chelsea Beach are of this variety. In specimens found 

 about Sandy Hook, New York harbour, the epidermis partakes of this 

 dark appearance, of about the color of Mr. Say's figure in the " Amer- 

 ican Conchology," though the surface is undulated. Hence I infer 

 that the oceanic specimens are of the dark variety, while those which 

 lie in quiet, sandy localities, like Provincetown harbour, have rather a 



