98 INVERTEBRATA OF MASSACHUSETTS. 



It is a very extraordinary shell, far exceeding in size any known 

 species of the genus. Indeed, its peculiar shape, very large spoon- 

 hinge, and the teeth folded like those of Arca, entitle it to a generic 

 distinction so far as the shell is concerned ; and I believe that a knowl- 

 edge of the animal will establish its claims to one. 



NUCULA limAtula. 



Shell oblong-ovate, rostrated, very smooth and shining ; beaks 

 sub-central ; teeth twenty-two on the anterior, and eighteen on the 

 rostrated side. 



Figure 62. 



State Coll., No. 184. Soc. Cab., No. 1962. 



JNucula limatula, Say ; Amer. Conch., pi. 12. 



Shell transversely-ovate, very much elongated, thin, lines of 

 growth very minute, otherwise smooth and covered with a beauti- 

 fully glazed, light-green epidermis, with an occasional darker zone, 

 and two or three lighter radiations ; beaks nearly central, not 

 prominent, inclined backwards ; hinge margin behind rectilinear 

 nearly to the tip, compressed, the compression not reaching the 

 tip, which is a little recurved, pointed and not truncated ; an- 

 terior and basal margin almost regularly rounded, entire ; interior 

 bluish-white, somewhat pearly ; cartilage-pit small ; the series 

 of teeth, extending more than two thirds the length of the shell, is 

 slightly bent at the pit, teeth prominent, most so at the middle 

 of each side, their summits forming a regular arch, twenty-two on 

 the anterior, and eighteen on the rostrated side, excavated on 

 their outer faces ; impressions quite obvious. Length ly\ inch, 

 height y^o inch, breadth j\ inch. 



Found in various parts of Massachusetts Bay. 



This beautiful shell may be distinguished from other species of our 

 coast by its length, which is more than twice as great as its height. 

 Its posterior portion is also more narrowed than in other species. 

 The dimensions given above are those of a specimen larger than is 

 ordinarily found. But I have a single valve sent me by Dr. Mighels 

 of Portland, which he dredged in the harbour of that place, where 

 he found them abundantly, measuring 2^^ inches in length, and l^W 



