1902.] Allen, Opossums of the Genus Didelphis. 259 



striction, n (11-11.5); occipital breadth, 29; breadth at canines, 18.7 

 (17-20); upper toothrow, 33.9 (33-35.3); molar series, 19.3 (19-20). 



The above description is based on an adult male, from Better 

 Hope, Demerara. Three other specimens from the Kanuka Moun- 

 tains (alt. 300 feet) , Guiana, agree in coloration and skull characters, 

 except that one is in the gray phase with whitish overhairs, the others 

 being in the black phase. A specimen from Mapures, Venezuela, is 

 also similar, but has the underfur stained basally with ochraceous 

 brown or gamboge, and the long overhair is mostly white, but some 

 of it is apically black, as in the black phase. 



Specimens examined: 



Guiana: Better Hope, Demerara, i specimen; Kanuka Mountains, 

 altitude 300 feet, British Guiana, 3 specimens. 



Venezuela: Mapures, i specimen. 



Total, 5 specimens, coll. British Museum. 



The true marsupialis of Guiana and the Lower Orinoco 

 region differs markedly through its lighter coloration, absence 

 of decided markings on the head, and its generally whitish 

 color, smaller size, and longer tail from any of the forms of 

 northern South America, and still more from D. aurita of 

 southern Brazil, as will be noticed later. 



Didelphis marsupialis insularis, subsp. nov. 



Didelphys marsupialis THOMAS, Journ. Trinidad Field Nat. Club, I, 



April, 1893, n. 

 Didelphis marsupialis ALLEN & CHAPMAN, Bull. Am. Mus. Nat. 



Hist. V, 1893, 230. 

 Didelphis karkinophaga ALLEN & CHAPMAN, Bull. Am. Mus. Nat. 



Hist. IX, 1897, 23 (Trinidad), 30 (Dominica). ALLEN, ibid. 



XIV, 1901, 1 86 (measurements). 



Type, No. |ff, $ ad., Caparo, Trinidad, March 19, 1894; coll. 

 Frank M. Chapman. 



Head almost wholly yellowish white to nape, with a very narrow 

 brownish eyering; in fresh long pelage the hairs on top of head slightly 

 tipped with dusky, giving a slight dingy tone, and sometimes tending 

 to form a dusky median band over the top of the head. Underfur 

 almost wholly yellowish white, a few of the coarser fibres tipped with 

 blackish, mainly along the middle of the back; at base over nape and 

 shoulders brownish ochraceous; long stiff overhair wholly white in 

 some individuals, wholly black in others, or black and white mixed 

 in still others. Below pale yellow or yellowish white, the tips of 

 a few of the longest hairs blackish, but so few as scarcely to affect the 

 general coloration. Fore limbs from elbows, and hind limbs from 

 knees, blackish brown, proximal portion like the body. Ears blackish 



