lYO INTRODUCTION. 



Natural History of Cuba, we cannot forbear making use 

 of some of the interesting information that it affords, 

 and also of facts contained in the memoir of Dr. Pfeiffer 

 on the pneumobranchiate mollusks of the same island. 

 In this connection also, the results of the observations of 

 M. D'Orbigny in Sovith America, in their relation to the 

 distribution of the terrestrial species on this continent, 

 gain an additional importance. We compare therefore 

 the genera of Cuba, and of South America, with those 

 of the United States. It is not to be supposed that 

 these lists are equally complete with that of the United 

 States ; indeed it may be taken for granted that they 

 are much less so. Being the work of foreign travellers, 

 who resided but a short time in those countries, many 

 species must have necessarily escaped notice, however 

 careful their researches may have been ; and whenever 

 the subject shall be resumed by native naturalists, the 

 gleanings may be expected to equal in number the first 

 harvest. But they probably represent pretty nearly the 

 proportion in which the respective genera prevail, and 

 may, therefore, serve our present purpose. 



It is proper to observe, before introducing the follow- 

 ing table, that the researches of M. D'Orbigny were 

 mostly confined to that part of South America which 

 lies north of the twenty-fifth degree of south latitude, 

 and that a large majority of his species appear to have 

 been collected in Bolivia, Peru, and Colombia, on the 

 western side of the continent. 



