216 NEW-YORK FAUNA MOLLUSCA. 



GENUS CYTHEREA. Lamarck. 



Animal as in Venus. Shell inequilateral, rounded. Hinge with four primary teeth in one 

 valve, one of which is remote from the others ; three in the other valve : no lateral teeth. 



Cytherea convexa. 



PLATE XXVII. FIG. 279. a. bight valve ; B. left. 



(STATE COLLECTION.) 



Cytheria convexa. Say, Jour. Acad. Nat. Sciences, Vol. 4, p. 149, pi. 12, fig. 3, 

 C. id. Conkad, Jour. Ac. Nat. Sc. Vol. 6, p. 261. 



C. id. Gould, Invertebrata of Mass. p. 84, fig. 49. 



Description. Shell moderately solid, ventricose, subcordate ; beaks elevated, directed for- 

 wards. Anterior lunule heart-shaped, distinctly marked by a simple line. Surface distinctly 

 marked by the stages of growth. In the left valve, the two middle teeth contiguous, divergent ; 

 the one behind these, thin, lamellar ; the anterior, conical, subacute : in the right valve, the 

 posterior bifid. Basal margin smooth within. 



Color. Epidermis dingy white ; beneath which opake white. 

 * Vertical axis, 1*4; transverse ditto, 1-7. Diameter, l - 0. 



This shell occurs from New-Jersey to Maine, and perhaps farther north. It is usually 

 found on muddy bottom, and is popularly known among the fishermen on Long Island as the 

 Little He-clam. It was first described as a fossil species from the the tertiary of Maryland, 

 by Mr. Say. 



(EXTRA-LIMITAL.) 



C. occulta. (Say, Ac. Sc. Vol. 2, p. 274 ) Suborbicular, thick, with numerous obtuse transverse and 

 longitudinal elevated lines, nearer to each other than their own diameters : the latter not visible to the 

 naked eye. Lunule destitute of the longitudinal lines. Color, yellowish white, with a few large 

 brown spots ; lunule and ligament slope transversely spotted with reddish brown. Length and 

 breadth, 0-5. Rare. Southern Slates. 



C. concent rica. (Lam. Am. sans vert. Vol. 2, p. 601. Ed. Brux. Conrad, Am. Mar. Conch.pl. 12.) 

 Shell orbicular, convex, depressed, subcquilateral, with numerouc crowded concentric stria?; lunule 

 heart-shaped, impressed, smooth; hinge with a large oblong fosset under the beaks; muscular im- 

 pressions very large. Color : epidermis brownish yellow, tinged with rusty. Virginia to Florida. 



C. giganiea. (Lam. Am. sans vert. Vol. 2, p. 597.) Shell large, ovate, smooth, slightly angulated 

 on the anterior side : posterior depression oblong-ovate, a little impressed on its sides and keeled in 

 the middle. Teeth of the hinge compressed. Color, pale livid, with numerous bluish longitu- 

 dinal rays, generally interrupted. Length, 3-25; Width, 6-0. Coast of the Southern Slates. 



