138 AMERICAN JOURNAL 



In the last number of this Journal (pp. .54-58) I stated the 

 origin of the Families and Sub-families of operculated Shells, 

 showing, from the distribution of species, the extent of African, 

 Asiatic, and West Indian influences in the Islands generally, 

 and in diiferent parts of the Continent. 



The following table explains how those influences, estimated 

 from similar data, are manifested in the different West Indian 

 sub-provinces. 



As might be expected from the result on the Continent, it 

 appears that the Asiatic influence has its maximum, and the 

 West Indian its minimum, in the group of islands (Guade- 

 loupe, &c.) which is nearest to, and, as I shall show, has most 

 relationship with South America.* 



There is another view, however, which deserves notice, of 

 the relationship of the operculated shell faunas of the Continent 

 and Islands, derived from the distribution of genera in con- 

 nection with the question of origin of the Families and Sub- 

 families. 



In the analyses in the preceding part of this paper (p. 57), 

 I dealt with the operculated shells generally, but the distribu- 

 tion of genera and species belonging to the three Families is, 

 in reality, very different. 



Aciculacea. Omitting TruncateUa (the distribution of which 

 in the Islands is imperfectly known), the other two genera, 

 Geomelania and Chittya, are not only West Indian, but pecu- 

 liar to Jamaica. 



Gyclostomacea. Of the QQ Continental species, 42 belong to 

 sub families of Asiatic, 1 of African, and 23 of West Indian 

 origin, which species are distributed as follows : — 



Origin. No. of Sp. in N. Am. Mexico. C. Amer. S. Amer. 



African, 1 



Asiatic, 5 9 28 



West Indian, 1 4 11 7 



The distribution in the insular sub-provinces is as follows: — 



Origin. No. of Sp. in Cuba, &c. Jamaica. Haiti. Porto Rico, Guade- 



&c. loupe, <S-c. 



African, 10 31 8 2 3 



Asiatic, 15 34 3 3 9 



West Indian, 123 29 26 14 3 



Helicinacea. This Family is of West Indian origin. 



* In connection with the distribution of operculated shells, the term 

 South America refers' especially to the intertropical parts of the Southern 

 Continent. 



