SOLEMYA. 49 



Shell remarkably thin and fragile, oblong, rather broadest be- 

 hind ; very inequipartite, upper and lower margins nearly parallel, 

 ends rounded ; beaks in no degree elevated, but having a slight pit 

 in front of them ; surface of the valves radiated 

 with about fifteen slightly impressed, double lines, 

 most conspicuous posteriorly, and most widely 

 separated across the middle ; short end distinctly 

 wrinkled by the lines of growth ; epidermis light ^, ^,^;^^^^ 



yellowish-brown or chestnut-color, firm, elastic, 

 glossy, at the hinge margin connecting the valves together for nearly 

 their whole length, and elsewhere projecting far beyond the mar- 

 gin of the calcareous portion, and slit at each of the radiating 

 lines, whence the edges have a ragged, fringed appearance, the 

 angles of the lobes rounded ; hinge toothless, consisting of a large 

 triangular receptacle for the cartilage, in each valve, resting on, 

 and partly enclosed by, a whitish bony support, arched beneath, 

 the legs of the arch partly enclosing the anterior muscular im- 

 pression, and the hinder branch directed nearly across the shell. 

 Length, one inch ; height, half an inch ; breadth, three tenths of 

 an inch. 



The foot of the animal protrudes behind and expands ; is obliquely 

 truncated, and the edges expand into two lobes which are serrated 

 at the edges ; the whole foot may assume a multitude of forms, and 

 the points of the serratures be prolonged into a fringe ; there is an 

 opening in the mantle for the passage of water, the edges fringed, 

 and two of the fibrils are longer than the others ; branchiae large, 

 thick, situated far back, each leaflet with a midrib ; palpi triangular, 

 long-pointed. Dr. Stimpson states that he has seen the animal 

 leaping and swimming about in the water for some time, without 

 touching bottom. The leap is performed by suddenly drawing in 

 the umbrella-shaped foot, at the same time that water is expelled 

 from the posterior opening liy the closing of the valves. 



Found upon Chelsea, Nahant, Nantasket, and other sandy beaches, 

 generally in the early months, and some years in great abundance. 

 At Dartmouth harbor. Professor Adams found them in mud, far be- 

 yond low-water mark. Fishing Banks (^Wi//is); whole New Eng- 

 land coast (^Stimpson) . 



It is an exceedingly delicate and curious shell ; its epidermis, 



hanging over the edges like a veil, at once distinguishing it. The 



dimensions, given above, include the epidermis, and are those of a 



shell of the largest size. In the yomiger stages the border of the 



4 



