36 INVERTEBRATA OF MASSACHUSETTS. 



the hinge margin connecting the valves together for nearly their 

 whole length, and elsewhere projecting far beyond the margin of the 

 calcareous portion, and slit at each of the radiating hnes, whence 

 the edges have a ragged, fringed appearance, the angles of the 

 lobes rounded ; hinge toothless, consisting of a large triangular re- 

 ceptacle for the cartilage, in each valve, resting on, and partly 

 inclosed by, a whitish bony support, arched beneath, the legs of 

 the arch partly inclosing the anterior muscular impression, and the 

 hinder branch directed nearly across the shell. Length 1 inch, 

 height I inch, breadth y\ inch. 



Found upon Chelsea, Nahant, Nantasket, and other sandy 

 beaches, generally in the early months, and some years in great 

 abundance. At Dartmouth harbour, Professor Adams found them 

 in mud, far beyond low-water mark. 



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

 ing over the edges like a veil, at once distinguishing it. The dimen- 

 sions, given above, include the epidermis, and are those of a shell of 

 the largest size. In the younger stages the border of the epidermis 

 is entire. The bony substance of the valves is so thin, that the lighter- 

 colored radiations are quite obvious within. 



Its special distinguishing marks will be more particularly pointed 

 out in the description of the next species. 



SOLEMYA BOREa'lIS. 



Shell fragile, ohlong ; epidennis darh-broivn, with fifteen to 

 twenty lighter radiating lines ; within grayish-blue ; cartilage- 

 support forked, the hinder branch directed obliquely forwards. 



State Coll., No. 221. Soc. Cab., No. 1739. 



Solemy^a borealis, Totti:n ; Slllhnans Journ., xxvi. 36(), fig. 1. 

 Solemy'a velum, Coxrad ; Jlmcr. Mar. Conch., pi. C6, f. ]G. 



This shell would be described in terms so similar to those em- 

 ployed for the preceding species, that a notice of those points in 

 which they differ will be the best description. 



It greatly excels in size, — the smallest that has been noticed 

 exceeding the largest S. velum. The valves are less convex, 

 and very much more solid, and their color within is always a 

 grayish-blue or lead-color ; the basal margin is a little arched up- 

 wards ; the ends are a little scolloped, there being a slight pro- 



