1878.] MR. E. R. ALSTON ON NEOTROPICAL SQUIRRELS. 661 



Upper parts grey or reddish grey, the hairs black, tipped or 

 ringed and tipped with white or red. Pelage somewhat soft, with 

 a good deal of under-fur ; lower parts deep red, orange, or white. 

 Tail black, washed with white, the hairs usually rufous at their base, 

 with black rings and white tips. 



Under this name I feel myself obliged to bring together two Mexican 

 Squirrels of which typical specimens are very different in appearance. 

 Mr. Allen has kept them separate under the names of $. aureigaster 

 and (S 1 . leucops, remarking that the difference in coloration leaves 

 little doubt of their distinctness, but adding that " more abundant 

 material may show that they are not specifically separable " {op. cit. 

 p. 755). The colour-variation is not nearly so great as we shall find 

 it to be in the next species ; and after a careful examination of a great 

 number of specimens, especially of the fine series in the Paris Museum, 

 I have been unable to find a single distinctive character which is 

 constant. 



Typical specimens of the two forms may be thus described : — 



1. The aureogaster type. Upper parts dark grey, the hairs 

 black, finely tipped with white. Lower parts deep red, which 

 is usually more or less washed over the grey on the shoulders and 

 flanks. 



2. The leucops type. Upper parts lighter grey, with a peculiar 

 golden lustre, the hairs being finely ringed with bright rufous and 

 tipped with white ; nape and rump more strongly rufous. Lower 

 parts bright red, orange, or white. 



Many specimens, however, which have the general appearance of 

 aureogaster show the rufous subterminal ring of leucops on some 

 part of the dorsal surface ; and in others we find the red nape and 

 rump-patches gradually appearing. I am therefore compelled to 

 return to the view long ago expressed by Isidore Geoffroy l , and to 

 regard them as varieties of the same species. 



With regard to distribution, all the specimens which I have seen 

 with authenticated localities are from Mexico ; but Mr. Allen mentions 

 one from Guatemala in the Washington Museum. Specimens in 

 the British Museum are labelled as being from Columbia ; but 

 there can be little doubt that this is an error. S. aureogaster is stated 

 by Prof. Sumichrast (as quoted by Mr. Allen) to be " the common 

 species of Sciurus of the tierra caliente of the east coast " of 

 Mexico ; and both forms are found in the States of Oaxaca and Te- 

 huantepec. 



Turning to the question of synonymy, I must briefly explain why 

 I have retained Erxleben's name for this species. Mr. Allen con- 

 siders it to apply rather to the next species, but rejects it altogether, 

 on the ground that it is based partly on Buffon's " Coquallin " 

 (S. niger, L.), and partly on the " Coztiocotequallin " of Hernandez. 

 It is, however, primarily founded on the latter, Buffon's name being 

 only quoted as a synonym ; and Erxleben's diagnosis and description 

 appear to me to be quite characteristic of the leucops form of the 



1 Voy. de la V6nus, Zool. pp. 156-163. 



