54 AMERICAN JOURNAL 



REMARKS ON THE ORIGIN AND DISTRIBUTION OF 



THE OPERCULATED LAND SHELLS WHICH 



INHABIT THE CONTINENT OF AMERICA 



AND THE WEST INDIES, 



WITH A CATALOGUE OF THE AMERICAN SPECIES. 



BY THOMAS BLAND. 



In a paper "On tlie Geographical Distribution of tlie Genera 

 and Species of Land Shells of the West India Islands, with a, 

 Catalogue of the Species of each Island," (Annals of the Lyceum, 

 N. Y., VIL, 1861), I referred to Darwin's remark, that "the spe- 

 cies of all kinds, which inhabit Oceanic islands, are few in num- 

 ber, compared with those on equal continental areas," and 

 that the affinity of the inhabitants of islands is "to those of 

 the nearest mainland, without being actually the same species.'' 



I observed, that "the generic affinity of the land shells of 

 the West India Islands to those of the adjacent parts of the 

 American Continent is certainly intimate, but the existence of 

 several genera, not represented on the Continent, shows other 

 relationships, — the operation, it may be, of local causes. See- 

 ing, moreover, the greater number of both genera and species, 

 absolutely and proportionately, in the islands under considera- 

 tion, it may not unreasonably be suggested that the insular 

 stamp has rather been impressed on the fauna of the adjacent 

 Continent, than the revei'se." 



With reference to the questions above noticed, I propose to 

 offer some further observations on the relations of the land 

 shell faunas of the American Continent and the West Indies 

 to each other, and to the faunas of other countries. My re- 

 marks, for the present, will be confined to the origin and dis- 

 tribution of the operculated shells. I adopt the classification 

 of Pfeiffer (Mon., 1865), giving the total number of genera 

 and species in each Family and Subfamily, and the names 

 (with number of species) of the genera represented in America 

 and the West Indies. I indicate the numbers of species which 

 occur in North America (excluding Mexico), Mexico (exclu- 

 sive of Lower California), Central America (including Yuca- 



