104 INVERTEBRATA OF MASSACHUSETTS. 



State Coll., No. 185. Soc. Cab., No. 1963. 



Nucula proxirna, Say ; Journ. £cad. Nat. Sc, ii. 270. 



Shell small, thick and solid, very oblique, triangular, the outline 

 and angles a little rounded ; the anterior side nearly vertical, and 

 about two thirds the length of the posterior side, forming some- 

 thing less than a right angle with it ; beaks somewhat elevated, 

 inclined forwards ; anterior slope with a large, ovate area, defined 

 by an angular ridge ; posterior edge broad and flattened ; surface 

 crossed with somewhat coarse lines of growth, and by very mi- 

 nute, radiating lines ; epidermis light olive-color, with darker 

 zones ; interior pearly, the margin very finely crenulated ; car- 

 tilage pit very small ; series of teeth twelve before and eighteen 

 behind the beaks, including the very small ones near the pit, 

 short and broad, the two series nearly at right angles with each 

 other. Length ^^f inch, height near anterior side ^^ inch, breadth 

 2 inch. 



Found not uncommonly in the stomachs of fishes taken near 

 Nahant. Professor Adams found it abundantly at Dartmouth, in 

 mud taken up beyond low-water mark ; and Dr. Yale sent it to 

 me collected on the shores of Holmes's Hole. 



By many, this shell has been supposed identical with the N. nucleus 

 of Englisli authors, — the N. margaritacea of Lamarck. But actual 

 comparison shows a wide difference. The N. nucleus is less trian- 

 gular, the posterior tip broadly rounded ; its proportional diameter is 

 not more than half as great, the epidermis is firm and darker, the 

 teeth are ten and twenty, and the whole shell is double the size of 

 ours. It is much more closely allied to, if not identical with, a shell 

 sent me by Mr. Sowerby under the name of N. nitida. The number 

 and arrangement of teeth is the same ; and if there be any difference, 

 it is that the British shell is smoother, narrower, the angle made by 

 the anterior and superior margins is greater, and the shape less ob- 

 liquely transverse. The strise are very obvious under the epidermis. 

 In young specimens a series of transverse indentations may be seen 

 along each side of the posterior hinge margin. 



