92 Allen Mammals of Margarita Island. 



species, of which 4 had not previously been recorded from the 

 island, and one, a squirrel, proves to be new. As might be ex 

 pected, the native mammalian fauna appears to have been de 

 rived almost wholly from South America. It is interesting to 

 note that the influence of the insular environment has been to 

 fade out, to a greater or less degree, the colors of several of 

 the species as compared with the colors of their nearest repre 

 sentatives of the continent and of Trinidad. The greater area 

 of the island of Trinidad and the heavier growth of vegetation, 

 with the consequent increase in humidity seem to have afforded 

 conditions more like those of the mainland, and hence there is 

 not so pronounced a tendency to paling out of the deeper colors 

 such as is seen notably in the Murine opossum and the squirrel 

 of Margarita Island, and also in several of the birds from the 

 island, which have been described as new. From its compara 

 tively small area, partial sterility, and greater isolation, Mar 

 garita is more open to the bleaching effects of sun and sea- 

 wind. Whether the bleaching of colors in the case of certain 

 pale insular forms is due to the direct action of exposure to the 

 elements, or is acquired as an adaptation to a more or less barren 

 environment, is an interesting question in this connection, and 

 it is possible that both causes often interplay to produce a com 

 bined result. 



A list of the mammals at present known from Margarita 

 follows: 



' i. Marmosa robinsoni Bangs. Robinson Murine Opossum. 



Didelphys murina Robinson, Proc. U. S. Nat. Mus., XVIII, p. 651, 189C. 

 Marmosa robinsoni Bangs, Proc. Biol. Soc. Washington, XII, p. 95-96, 

 1898. 



Five specimens of this opossum were collected in 1895, by Capt. Rob 

 inson, and are characterized as forming a pallid insular species. 



> 

 2. Caluromys philander (Linnaeus). Woolly Opossum. 



A single specimen was brought in to Mr. Clark at El Valle, on July 

 12, 1901. This was an adult female within whose pouch were three 

 young clinging to the mammas, and as yet hardly more than 3 cm. in 

 total length. I have been unable to compare the adult specimen with 



