230 NEW-YORK FAUNA — MOLLUSCA. 



This is the largest of our bivalve shells, and is familiarly known on the shores of Long 

 island as the Beach Clam and Dipper Clam. They are esteemed as an article of food. They 

 occur buried in the sand, and the largest I have seen had a transverse length of nearly seven 

 inches. 



Mactra lateralis. 



plate xxix. fig. 287. 

 (state collection.) 



Mactra lateralis. Say, Journ. Acad. Nat. Sciences, Vol. 2, p. 309. 



M. id. Conrad, Aimer. Marine Conehology, p. 62, pi. 14, figs. 4,5. 



Mulinia. Gray, Loudon Mag. Nat. Hist. New series, Vol. 1, p. 376. 



M. lateralis. Gould, Invertebrata of Mass. p. 54, figs. 34, 35. 



Description. Shell small, triangular, very convex, polished, smooth or at least with very 

 minute wrinkles, nearly equilateral. Beaks tumid, nearly central, contiguous, directed for- 

 wards : areas before and behind the beaks broad, flattened, sometimes concave, heart-shaped, 

 and bounded by slightly elevated ridges. A stout prominent v tooth, and a strong lateral tooth 

 on each side of it, in the left valve. 



Color. Epidermis thin, rusty brown ; beneath which, bluish white ; within polished white. 



Vertical axis, 0*3 -0' 7; transverse ditto, - 7 - - 9. 



This is not a very common species, although it is occasionally found on the shores of Long 

 island. It has been found at Glass-house point a few miles above the city, and also by 

 dredging near Rye, Westchester county. 



(EXTRALIMITAL.) 



M. ovalis. (Gould, Op. cit. p. 53, fig. 32.) Shell large, thick, coarse, covered with a tough corru- 

 gated epidermis : beaks but little elevated ; v tooth strong ; lateral teeth short and slender, not 

 striated. Color: epidermis dusky brown. Vertical axis, 2*5; transverse ditto, 3*5. Stomachs 

 of fishes on the Northern Coast. 



M. similis. (Say, Jour. Acad. Nat. Sc. Vol. 2, p. 309.) Shell almost as large as solidissima, trian- 

 gular, smooth or very slightly wrinkled : beaks nearly central ; lateral teeth strongly and regularly 

 crenated on the side next the recipient cavity. Vertical axis, 1*15; transverse ditto, 1.4. Rhode- 

 Island, and frobably this Slate. Conrad supposes it to be the young and half grown of solidis- 

 sima. 



M.fragilis. (Chemnitz, pi. 24. M. oblonga, Say, lb. Vol.3, p. 310. Conrad, pi. 14.) Shell 

 oblong-oval, transverse, very slightly wrinkled except upon the margins; umbo hardly prominent: 

 two strong distant lines or folds drawn from the apex to the anterior extremity of the shell. Color, 

 dull whitish, hardly polished ; umbo slightly tinged with ferruginous; within white, high polished. 

 Vertical axis, 0'45; transverse ditto, 1*9. Coast of Georgia. 



