246 NEW- YORK FAUNA MOLLUSCA. 



the shell. Surface covered with a stout glossy epidermis, which extends beyond the basal 

 and lateral margins, and at the hinge margin connecting the valves together for nearly their 

 whole length. On the margin where it projects, it is cleft at the ends of the radiating lines, 

 so as to produce a series of rounded lobes. 



Color. Epidermis reddish brown or chesnut-color, with light yellow radiations, which are 

 nearly equidistant, with the exception of a free space directly opposite the hinge ; within 

 bluish white : against the light, the external radiations are visible. 



Vertical axis, 0' 35-0" 5; transverse ditto, 0"8-l'0. 



This shell occurs on the shores of Massachusetts, and, according to Mr. Wheatley, on the 

 shores of Long island ; and should it prove identical, as several conchologists have suspected, 

 with the following from Rhode-Island, we may expect to find the latter variety in the waters 

 of our own State. 



(EXTRA-LIMITA L.) 



5. borealis. (Totten, Am. Jour. Vol. 26, p. 366. Couthouy, Best. Jour. Vol. 2, p. 155. Goulb, 



1. c. p. 36. Pl. 30, fig. 291 of this work.) Shell fragile, oblong, but larger and more solid than 

 the preceding. Radiations with a larger free space ; the edges of the epidermis not rounded by the 

 slits, but preserving a square form, and are everted ; the cartilage support not arched or vaulted, but 

 forked, with the hinder branch directed obliquely forwards. Color, dark blackish brown. Verti- 

 cal axis, • 8 ; transverse, 2 • 5. Mr. Couthouy noticed one with a transverse axis 4 * 5 long. 

 Rhode-Island, Massachusetts. 



Genus Panopea, Men. de la Groye. Shell equivalve, transverse, unequally gaping at the sides and at 

 the base : a small conical tooth on each valve, and a rounded callosity at each side, to which 

 the ligament is affixed. 

 P. arctiea. (Lam. 1. c. Vol. 2, p. 526. Gould, 1. c. fig. 27.) Shell oblong, subcylindrical, strongs, 

 widely gaping at both ends, rounded in front, truncated behind, traversed by two radiating wave- 

 like ridges which divide the surface into three nearly equal portions. Vertical axis, 1 • 5 ; trans- 

 verse, 2*5; diameter, 1*3. When viewed from behind, it resembles somewhat the outline of P kolas 

 erispata. Grand Banks. 



Genus Glycimeris, Lam. Shell transverse, inequilateral, greatly gaping above and below : hinge- 

 margin callous, without a tooth ; ligament external ; epidermis thick, extending beyond the 

 margin of the shell. 



6. siliqua. (Lam. I.e. Vol. 2, p. 526. Russel, Ess. Jour. Vol. 1, p. 51. Gotjld, I.e. p. 39. Pl. 



33, fig. 308 of this work.) Shell transversely oblong, compressed, heavy and solid; epidermis 

 thick and shining, and obliquely wrinkled ; beaks not prominent, eroded ; ligament large and pro- 

 minent on the shorter end. Interior with a very thick callus in the course of the palleal impression ; 

 callus of the hinge broad and prominent. Color: epidermis shining black; within ashy vfhite. 

 Vertical axis, 1 • - 1*5; transverse axis, 2 • 5 - 3 • 5. Grand Banks. A few dredged on the coast 

 of Massachusetts. Common to both sides of the Northern Atlantic. 



