136 AMERICAN JOURNAL 



REMARKS ON THE ORIGIN AND DISTRIBUTION OP 



THE OPERCULATED LAND SHELLS WHICH 



INHABIT THE CONTINENT OF AMERICA 



AND THE WEST INDIES. 



(Continned from p. 58.) 

 BY THOMAS BLAND. 



Before discussing in detail tlie relations of the "West Indian 

 Islands inter se, and with the adjacent Continent, as shown by 

 the distribution of operculated and also inoperculated land 

 shells, I desire to explain the difference in the character and 

 extent of the distribution of the two classes. 



That difference is not, it appears, peculiar to the region 

 under consideration, inasmuch as fully two-thirds of all the 

 known operculated species are peculiar to Islands, while more 

 than one-half of the inoperculated are peculiar to Continents. 



The facts with reference to the distribution of genera and 

 species in America and the West Indies are as follows : — 



American Continent. West Indies. 



Operculated genera, 14 22 



" species, 151 603 



2 genera (3 species) peculiar to the Continent. 

 10 " (215 " ) " " Islands. 



12 " common, with 149 species on the Continent and 

 388 on the Islands. 



American Continent. West Indies. 



Inoperculated genera, 23 18 



species, 1251* 737 



5 genera (15 species) peculiar to the Continent. 

 1 genus (If " ) " " Islands. 



17 genera common, with 1236 species on the Continent and 

 736 on the Islands. 



* The number of inoperculated continental species is rather approximate 

 than absolutely correct. For general purposes, I use the classification of 

 the Helicea adopted by Pfeiffer in his Monograph, but in a subsequent part 

 of this paper I shall refer to the sub-genera of Ilellv, Bulimus, Sj-c. 



t Ennea Mcolor, Gould, found in St. Thomas and Trinidad; also in the 

 East Indies. The genus belongs to Africa. 



