182 Bulletin American Museum of Natural History. [Vol. Ill, 



specimens were taken in May, and that among them is a suckling, 

 apparently only a few days old, which has the same pattern of 

 coloration and about the same tints as the adults. These speci- 

 mens of course represent the summer or breeding pelage. 



25 Sciurus leucops (Gray]. 



Sciurus aureogaster GEOFFROY, Voyage de la Venus, Zool., 1855, p. 156, pll. 



x, xi (not S. aureogaster F. Cuvier, 1829). 



Macroxus leucops GRAY, Ann. and Mag. Nat. Hist., 3d Ser., XX, 1867, p. 427. 

 Sciurus leucops ALLEN, N. Am. Roden., 1877, p. 753. 

 Sciurus variegatus ALSTON, P. Z. S., 1878, p. 660; Biol. Centr.-Am., Mam., 



1880, p. 127, pi. xi (the " leucops type " only). 



Six skins and skulls, Tehuantepec City, State of Oaxaca, Feb. 

 3 to March 9, 1890. 



These specimens appear to typically represent the Macroxus 

 leucops of Gray, described from " Oaxaca." The material now 

 before me, taken in connection with that previously examined, 

 leads me to resume the position I took in 1877 (N. Am. Roden., 

 PP- 75~756) regarding the status of the forms then recognized 

 as S. aureogaster and S. leucops, from which I have since wavered,* 

 in deference to Mr. Alston's conclusions.! The pattern of color- 

 ation in the two forms is very different, in leucops there being 

 always a well-defined nuchal patch of rufous, and generally 

 another rufous area on the rump, the latter, however, sometimes 

 absent. While the color of the ventral surface may vary from 

 pure white, through buff and pale yellow to golden and even 

 orange rufous, it does not extend up the sides of the body at the 

 shoulders, nor encroach upon the outer surface of the limbs, as 

 in aureogaster, the line separating the colors of the dorsal and 

 ventral surfaces being a straight line at the usual point in other 

 mammals having the two surfaces differently colored. The skull, 

 while of nearly the same size in the two forms, is much heavier 

 and stronger in aureogaster, with the first premolar much larger 

 and the dentition much heavier. 



The six specimens from Tehuantepec City vary considerably 

 in color above, and greatly in the color of the ventral surface. 

 All have a large fluffy conspicuous white patch behind the ear 

 (possibly disappearing later in the season). The nuchal patch is 



* Bull. U. S. Geol. Surv., IV, 1878, p. 882. t P. Z. S., 1878, pp. 660-662. 



