54 INVERTEBRATA OF MASSACHUSETTS. 



Found at the Bank fisheries, in the stomachs of fish. The 

 young, from a fourth of an inch to an inch in length, are found 

 abundantly in fish caught in Boston harbour. At least, they differ 

 from the young of M. solidissima, and correspond in external 

 proportions and appearance to our shell, and the teeth are slender 

 and without striae. 



This shell is inferior in size to the M. solidissima only. The 

 largest valve I have seen measures 4-i- by 2f inches. In general it is 

 found smaller than the dimensions given. Such specimens have a 

 straw-colored epidermis. 



Its size, shape, and surface distinguish it from M. grandis, CHEMN. 

 M. solida, and all other known species except M. solidissima. Com- 

 pared with that more common shell, it differs in its coarser surface, its 

 thick, dusky epidermis, its less elevated beaks and less convex valves, 

 the longer and narrower anterior portions, the rough, oval portion be- 

 hind the beaks embracing more of the shell, the more feeble hinge, 

 the stout and firm V tooth, and the deep sinus of the palleal im- 

 pression. 



I have very little doubt that this is the shell described by Deshayes 

 as M. grandis. The descriptions correspond well. But, as it is not 

 figured or quoted by other authors, and the habitat was not known to 

 him, it is impossible to decide with certainty. Singularly enough too, 

 Deshayes himself does not cite it in his new edition of Lamarck. 

 Provided it be the same, however, the specific name must necessarily 

 be changed, as his name was previously given to a different species by 

 Chemnitz. 



This appears to be the same species, a small specimen of which is 

 figured by Mr. Gray in the Appendix to Beechey's Voyage, under the 

 name of M. similis. This name is pre-occupied by Mr. Say. 



MACTRA LATERA'LIS. 



Shell small, triangular, very convex, nearly equilateral ; beaks 

 elevated, the spaces before and behind them broad heart-shaped. 



FIGURES 34, 35. 

 State Coll., No. 227. Soc. Cab., No. 2325. 



Mactra laterals, SAY ; Journ. Acad. Nat. Sc., ii, 309. CONRAD ; Am.tr. Mar. 

 Conch., 62, pi. 14, f. 4. 



