666 MR. E. R. ALSTON ON NEOTROPICAL SQUIRRELS. [June 18, 



ing ; tail black, washed with bright-red orange, often very bushy. 

 Pelage rather harsh and sparse, ears high and narrow. 



Here, again, the greater amount of material at my disposal 

 compels me to go beyond Mr. Allen in the identification of nominal 

 species. Most of the above synonyms were brought together 

 by him. under the name of S. variabilis; but S. gerrardi and S. 

 Um^u^ - -yjiy^. . mfo - nigcr were kept separate under the former title. The principal 

 points on which he rested were the smaller size and shorter ears 

 of S. gerrardi ; but on examination of a sufficient series, I have 

 not been able to find any constancy in the proportions of the ears, 

 while the difference in size totally disappears, as is shown by the 

 following series of measurements — 9^0, 9*75, 1000, 1025, 1075, 

 11, 1150, 11-75, 12-00, 12-75, 1300. The smaller specimens 

 (8. variabilis, S. gerrardi, &c.) appear to prevail towards the north : 

 but this is not constant ; for a Santa-Martha example measures over 1 2 

 inches, while others from Brazil are under 10 in., although evidently 

 adult. Nor is it constantly connected with any of the numerous 

 varieties of coloration — rufous, grizzled, and melanistic specimens 

 occurring of all sizes. 



The range of these variations of colour is not nearly so great as 

 in S. hypopyrrhus ; and they seem to resolve themselves into three 

 primary groups, namely : — 



1. The morio type. Upper and lower parts black, only slightly 

 ringed with rufous or fulvous, tail black, either entirely or slightly 

 washed with red. Of this melanistic form no two specimens agree 

 exactly in the proportion of red ; and every step is present leading 

 into 



2. The variabilis type. Upper parts red, more or less varied with 

 black — but the rufous tint prevailing, especially on the flanks ; lower 

 parts pure white, fulvous, or pale rufous ; tail (either narrow or bushy) 

 black, strongly washed with bright rufous or orange. Here we have 

 an endless series of minor variations, from the very brilliant black 

 and red specimens sent from the Rio Napo to the British Museum, 

 and the bright rufous Columbian form, through more and more 

 greyish red specimens, till we find ourselves in 



3. The langsdorffi type. Upper parts reddish or yellowish griz- 

 zled, the hairs being pretty uniformly ringed with black and red or 

 black and yellow ; lower parts and tail as in the last. 



Each of these styles appears to prevail in certain localities : thus 

 the melanistic form has been found on the Upper Amazous by Mr. 

 Bates and by Castelnau and Deville, the rufous type on the Bio 

 Negro and Bio Madeira by Natterer, and the grizzled in North- 

 western Brazil by Spix. But there seems to be no regularity in their 

 distribution ; and I have seen both grizzled and red specimens from 

 Panama, Venezuela, Columbia, and North-eastern Peru. 



The oldest name, and therefore the one here adopted, is S. varia- 

 bilis, given in 1832 by Isidore Geoffroy to small red specimens from 

 Columbia, and strictly synonymous with Gray's S. gerrardi ; while 

 S. igniventris and S. pyrrhonotus were MS. names of Natterer' s, 

 applied by Wagner to other varieties of the rufous type. S. langs- 



