58 AMERICAN JOURNAL 



The facts regarding the distribution of the operciilated land 

 shells most certainly do not support the statement of Darwin, 

 that "the species of all kinds which inhabit Oceanic islands 

 are few in number, compared with those on equal continental 

 areas;" but they do lead to the conclusion, in the case under 

 consideration, that the insular stamp, as I have elsewhere ob- 

 served, has rather been impressed on the fauna of the adjacent 

 continents, than the reverse. 



I have not closely examined the subject, but believe that 

 the distribution of operculated species in other islands or 

 groups of islands (for example, Madagascar and Ceylon) show 

 the same connection with the continents adjacent to them, as 

 exists between the West Indies and America. The question 

 is suggested. Are the faunas of the islands more ancient than 

 those of the continents? 



It is a noticeable fact, bearing on the relationship of the 

 American and West Indian operculated shell faunas, that the 

 identical species common to both are very few. 



The following are the only examples known to me : — 



Cijdotus translucidus^ Sowb., Columbia and Ins. Trinidad, 



Chondropoma dentahim, Say, Florida and Cuba. ' .' 



Helicina suhglohulosa, Poey, " " 



" Dysoni, Pfr., Honduras and Ins. Trinidad. 



Several species of Truncatella are common to both faunas, 

 but the habits of that genus are rather maritime than terres- 

 trial. 



On a future occasion I may attempt a similar inquiry rela- 

 tive to the origin and distribution of the inoperculated species. 



