and of its Dejk nek nei< s. 388 



ter the Gulf of Mexico), of which 15 are confined to theextreme 



north of it; 37 are common to the Atlantic and Boreal provin- 

 ces, of which 10 are almost confined to the first, and 12 to the 

 last; 57 are common to all three provinces, of which 35 only 

 reach the extreme northern part of the Atlantic province. 



Ninety-four species in all are found on both sides of ('ape 

 Cod, or 64 per cent, of the entire number. This would at first 

 seem to indicate a much less degree of distinctness between the 

 molluscan fauna north and south of Cape Cod than really 

 exists; but as 10 of these are southern species, extending only 

 to Massachusetts Bay, and 47 northern one-, passing only a 

 short distance south of the Cape, the remaining 35 species more 

 truly represent the degree of similarity between the two pro- 

 vinces. 



Twenty two species occur in Europe. 



With regard to nomenclature, in the enumeration of the 

 marine and fluviatile species, we have followed, with but one 

 or two exceptions, that adopted by Stimpson, in his " Shells of 

 New England." We are well aware that improvements might 

 be made in the same, as this work has been published quite a 

 number of years;* but so many changes have been made of 

 late in nomenclature — some for the better, and very many more 

 for the worse — that, for the present at least, we have determin- 

 ed to adhere to Stimpson's system. The land shells have been 

 classed in accordance with t thc recent publication of Binney 

 and Bland. f 



We will here remark, that our type- of the species enumer- 

 ated in the following list have been placed in the Museum of the 

 School of Mines, of Columbia College, N. V. : the numbers ap- 

 pended to the names of the species in the list correspond with 

 those placed on the specimen-, in the Museum. We have also 



* 1851. 



f Smith. Misc. Coll., 194. L. & P.W. BheHfl <rf X. A. Pt. 1. Pttlmonata 

 Geophila. W. G. Binney and T. Bland. 1869. 



