﻿MAMMALS OF NORTHERN COLOMBIA — HERSHKOVITZ 339 



between old and new pelages. Alolt occurs through the months of 

 August, September, and October. New pelage is prime in December 

 and January. From February through July the pelage becomes 

 progressively shorter, thinner, and paler as result of wear on the dark 

 tips of the hairs. However, as compared with winter and summer 

 pelages of cottontails of middle latitudes of North America, the pelage 

 of IS eotropical forms is of uniform length and thickness the year round. 

 Subspecies. — The comparatively small area of northwestern South 

 America inhabited by cottontails varies little ecologically from place 

 to place. This condition tends to restrict subspeciation almost en- 

 tirely to macrogeographic isolation. Cottontails west of the Sierra de 

 Perija, the western bifurcation of the Cordillera Oriental, in Colombia, 

 are all rufous-naped. They segregate into two weakly defined races, 

 the northern Colombian superciliaris and the paler, smaller purgatus 

 of the upper Rio Magdalena Valley. Cottontails east of the eastern 

 bifurcation of the Cordillera Oriental, the Sierra de M^rida, in Vene- 

 zuela, are likewise rufous-naped but differ appreciably in cranial 

 characters from their Colombian relatives. Eastern Venezuelan sub- 

 species recognized are the nominal mainland forms, cumanicus, 

 valenciae, and orinoci, and the insular margaritae and avius. The 

 Lake Maracaibo Basin, between the eastern and western bifurcations 

 of the Cordillera Oriental, is inhabited by a dark-naped form, S. 

 fioridanus continentis. Cranially, continentis bridges the gap between 

 the eastern and western rufous-naped rabbits. Available material 

 does not show complete intergradation between continentis and the 

 Colombian superciliaris in one character, color of nape. On the other 

 hand, a series from Rio Tocuyo, in the highlands between the Sierra 

 de M^rida and the low plains of the coast and Lake Maracaibo, rep- 

 resents a completely intergrading population between continentis and 

 rufous-naped cottontails of eastern Venezuela. The name nigronu- 

 chalis is based on a dark-naped rabbit from Ai'uba, an island about 

 20 km. off the Peninsula de Paraguana. Absence of important 

 differences between the Aruba form and its nearest mainland relative, 

 the equally dark-naped continentis, indicates its comparatively recent 

 separation from the mainland stock. No doubt dark-naped forms 

 arose from a rufous-naped cottontail somewhere within the present 

 range of continentis. The probable dominance of a blackish nape 

 over the reddish one has permitted continentis to maintain and even 

 to extend its range. 



SYLVILAGUS FLORIDANUS SUPERaLIARIS (Allen) 



Lepus (Sylvilagus) superciliaris Allen, Bull. Amer. Mus. Nat. Hist., vol. 12, p. 



196, 1899. 

 Sylvilagus superciliaris, Allen, Bull. Amer. Mus. Nat. Hist., vol. 20, p. 445, 1904 



(Bonda; field notes by H. H. Smith). — Pocock, Proc. Zool. See. London, 



1914, p. 905, fig. lOd (facial vibrissae). 



