﻿MAMMALS OF NORTHERN COLOMBIA — HERSHKOVITZ 335 



brasiliensis is thick, soft, quite lax, and obviously adapted for preser- 

 vation of body heat. Pelage of S. aquaticus more nearly resembles 

 that of palustris but is not so highly specialized. The nuchal patch, 

 nearly suppressed in palustris, is well defined in aquaticus and tropical 

 races of hrasiliensis. In Temperate Zone tapitis, color of the long, 

 thick nuchal pelage tends to merge with that of sm-rounding parts. 

 Normally there are eight mammae in palustris and aquaticus, six in 

 hrasiliensis. 



Important cranial characters, apart from gross differences in size, 

 separate hrasiliensis from palustris and aquaticus. Basisphenoid in 

 S. hrasiliensis is subtriangular in outline, with only anterior third 

 nearly parallel-sided; ventral sphenopalatine plates latcrad of basi- 

 sphenoid slightly or not at all imperforate. In palustris basisphenoid 

 is funnolform in outline with one-half or more of anterior portion 

 nearly parallel-sided; sphenopalatine vacuities usually strikingly large 

 and may extend beyond nearly parallel-sided portion of basisphenoid. 

 Bullae of palustris are approximately twice the bulk of those of 

 brasiliensis. Occipital condyles of palustris are widely separated from 

 each other, the distance between ventral posterior edges of each 

 condylar ridge greater than width of sphenooccipital synchondrosis. 

 In brasiliensis the condyles are more approximated, the distance 

 between them usually less than width of sphenooccipital synchon- 

 drosis. Posterior projecting process of zygomatic bone short and 

 obtuse in brasiliensis; longer, more tapering in palustris. In hrasilien- 

 sis angular process of mandible is comparatively weak, articular 

 surface of condyloid process relatively short, coronoid process small; 

 in palustris angular process relatively longer, stronger and more 

 rounded, articular surface of condyloid relatively longer, coronoid 

 process comparatively well developed. Sylvilagus aquaticus agrees 

 with hrasiliensis in most cranial characters separating the latter from 

 palustris. The basisphenoid and sphenopalatine plates of aquaticus 

 are as in brasiliensis; bullae smaller than those of palustris; posterior 

 angle of supraorbital process normally completely fused with frontal 

 in aquaticus, is less completely fused in palustris, entirely free or 

 partially, seldom completely, fused with frontal in brasiliensis. Den- 

 tal characters show considerable range of variation in the species 

 concerned and offer nothing of diagnostic value. 



Sylvilagus insonus Nelson is a large species with a superficial 

 resemblance to >S'. aquaticus. The status of insonus cannot be deter- 

 mined definitely on the basis of the type and topotype, the only 

 specimens available. However, insonus does not appear to be a 

 tapiti, nor does it show any of the peculiarities of S. palustris. It is 

 best treated as a distinct species of the typical section of the genus. 



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