I 7 Bulletin American Museum of Natural History. [Vol. XIV, 



predicated on the basis of the present collection, while doubtless 

 others will be made known later when a much larger amount of 

 material, covering more completely the range of the group, and 

 embracing proper series from a large number of localities, be- 

 comes available for elaboration. None of the names above cited 

 can refer to any of these forms, but should the animal of the west 

 coast of Mexico prove to be separable from that of the interior, 

 as seems not improbable, Bennett's name calif ornica may be em- 

 ployed for it, as it seems likely that Bennett's specimens were 

 obtained there by Douglass. 



Relationships. It seems preferable to treat the Mexican D. 

 marsupialis group as specifically separable from D. virginiana of 

 the United States, although the characters that distinguish the 

 two are mainly differences of degree, or comparative rather than 

 absolute. The chief features of distinction between the two 

 forms, are (i) the greatly increased length of tail in the D. mar- 

 supialis group, with the basal half, instead of only the extreme 

 basal portion, black; (2) absence of white on the toes; (3) ab- 

 sence of white on the ears, although a slight white edging seems 

 liable to crop out sporadically throughout the range of the 

 species; (4) the increased width of the apical black zone of the 

 underfur, which gives even in the gray phase a darker general 

 effect to the coloration; and (5) the grayish dusky color of the 

 whole front of the head, including the top and sides of the nose, 

 and the presence of a well developed ocular stripe. In respect 

 to the characters of the skull, the Texas specimens of the D. 

 marsupialis group do not seem to differ appreciably from specimens 

 of D. virginiana from central and northern Texas and elsewhere 

 in the United States. 



The relationship of D. marsupialis to the southern forms of the 

 genus cannot be satisfactorily determined, owing to insufficient 

 material from Central America. A series of four specimens from 

 Nicaragua, however, and a few from Costa Rica, indicate an ani- 

 mal quite different from D. marsupialis, through its more slender 

 form, as shown in the total length of the animal, in the higher 

 ratio of tail length to that of the head and body, and in the nar- 

 rower and longer skull, and also in the pointed form of the pos- 

 terior border of the nasals. (See Plate XXIII, Fig. 5, and Plate 

 XXIV, Fig. 3.) 



