1878.] MR. E. R. ALSTON ON NEOTROPICAL SQUIRRELS. 663 



are given above, 1 have gone beyond Mr. Allen, who divides them 

 into two species under the titles of S. hypopyrrhus and S. boothice. 

 The series of specimens to which he had access left him strongly 

 impressed with their distinctness ; but he adds that further material 

 may show that they intergrade. After a careful examination of the 

 large series contained in various Museums, and especially of that at 

 Paris, I am quite convinced that this is the case, and have even 

 grave doubts of the propriety of keeping them distinct from the last 

 species. But as I have not yet found specimens strictly intermediate 

 between S. vurieyatus and 8. hypopyrrhus in the character of the 

 pelage and the annulation of the fur, it seems uest to keep them 

 distinct. 



The opiuion has been expressed above that the differences in com- 

 parative length of tail and ears, on which Mr. Allen lays most weight 

 in separating &. boothice from S. hypopyrrhus, cannot be depended 

 011 ; and I have been totally unable to detect any constant difference 

 in general stoutness of form or. breadth of muzzle. As to colour, 

 the intergradations of the different varieties are quite complete, so 

 that it is often difficult or impossible to say to which a given spe- 

 cimen is to be referred. Each variety, however, has its own type, 

 and seems to predominate in its own immediate locality. The five 

 principal phases known to me may be thus arranged : — 



1. The hypopyrrhus type. Upper parts dark-grey, the hairs 

 black, ringed with white or pale fulvous. Lower parts either con- 

 colorous, with the upper or washed with rufous. To this variety 

 I agree with Mr. Allen in referring Bennett's S. uiyrescens ; and it 

 is to the same form that the description of Mucroxus boothice 

 in Gray's memoir of 1867 refers, although the same author's 

 Sciurus boothice of 1833 was founded on a young example of the 

 white-bellied colliai phase. The rufous-bellied specimens lead us 

 directly into 



2. The riyidus type. Upper parts usually marbled with fulvous 

 and black, tne hairs being glossy brown or black with a median band 

 of yellowish brown. Lower parts bright rufous (riyidus), or varied 

 with rufous and white, either symmetrically (intermedius) or asym- 

 metrically (nicoyanus). Iu many specimens, as observed by Mr. 

 Allen, there is a more or less marked tendency to the development 

 of a pale grizzled lateral stripe placed high on the flanks and con- 

 fining the dark dorsal area to a broad median band. From these we 

 have every gradation into the rufous phase of 



3. The dorsalis type. Upper parts with the median dorsal area 

 black, flanks and lower parts white, fulvous, or rufous. In many in- 

 dividuals the hairs of the black dorsal area will be found to have 

 concealed rings of white or fulvous ; so that we have a further tran- 

 sition into 



4. The collicei type. Upper parts much as in the riyidus form, 

 but usually less rufous ; lower parts white (collicei, adolphei) or pale 

 fulvous (varieyatoides, yriseocaudutus, j/y/adei, oculatus). Usu- 

 ally the dark coloration of the back is extended onto the shoulders, 

 hips, and limbs; but in others it is conhned to the middle of 



