FAMILY SOLENIDJE — SOLEMYA. 245 



the shell. Teeth three in the left valve ; the posterior upright ; the others directed forwards. 

 A strong broad rib passes from the beaks towards the margin, where it becomes obsolete. 

 Surface smooth and diaphanous, with minute wrinkles about the posterior end, and faint traces 

 of radiations. Epidermis smooth and shining. 



Color. Pale violaceous, passing into olive towards the margins, disposed in a radiated 

 manner ; within, bluish white, faintly iridescent ; the transverse rib white. 



Vertical axis, 0"8; transverse ditto, 1-5 -2-0. 



This is a northern species, occurring as far south as New-Jersey. On the coast of Massachu- 

 setts it is very abundant, but is more rare on our coast. 



(EXTRA-LIMITAL.) 



M. nitida. (Gould, Am. Jour. Vol. 38, p. 196; Invertebrata of Mass. p. 33, fig. 25, 26.) Shell 

 thick, slightly recurved, ovate-oblong, undulated by the lines of growth. In the left valve, three 

 teeth ; in the right, two. Color : epidermis greenish yellow, shining, corrugated at the posterior 

 end. Vertical axis, 1*25; transverse', 2*8. Massachusetts. 



GENUS SOLEMYA. Lamarck. 



Animal with the lobes of its mantle reunited in their posterior half, and terminated by two 

 short and unequal siphons. Foot proboscis-like, truncated in front by a sort of disk or 

 sucker, the edges of which are fringed. A single branchia on one side in the shape of a 

 plumule, the barbs of which are divided to the base. Vent terminal, not floating. Shell 

 equivalve, transverse, inequilateral. Epidermis thick and shining, projecting far beyond the 

 margin. Beaks inconspicuous. Hinge-margin widened and excavated to form a receptacle 

 for a cartilage, usually resting on a rib-like support. 



SOLEMYA VELUM. 

 PLATE XXX. FIG. 292. 



(STATE COLLECTION.) 



Solemya velum. Say, Jour. Acad. Nat. Sciences, Vol. 2, p. 317. 



S. id. Conrad, Am. Mar. Conchology, p. 66, pi. 16. 



S. id. Russel, Ess. Nat. Hist. Vol. 1, p. 53. Gould, Invertebrata of Mass. p. 35. 



S. id. Wheatley, Catalogue of the Shells of the U. S. p. 5. 



Description. Shell very thin and fragile, transversely oblong-elliptical ; beaks not elevated ; 

 umbones scarcely apparent ; the basal and hinge-margins parallel, ends rounded. Hinge 

 toothless, placed near the anterior end, with a slightly prominent cartilage resting on an 

 arched bony support, which is itself supported beneath by pillars which are directed across 



