On a neiv Agouti from British Guiana. 259 



XXVIII. — A neio Agouti from the Moon Mountains, Southern 

 British Guiana, with Notes on other Species. By Old- 

 FiELD Thomas. 



(Published by permissiou of the Trustees of the British Museum.) 



The agouti of the Moon Mountains, Southern British Guiana, 

 seems to represent a new subspecies of I), aguti, L., a name 

 under ■vvliicli I propose to place all the orange-rumped agoutis 

 with the exception of the small insular JJ. rubrata of 

 Trinidad. 



The members of this group from the coast-region of 

 North-eastern Venezuela and Northern Guiana are probably 

 all referable to a single form, ranging from Cumana to 

 Cayenne. The earliest name for them is D. a. Jlavescens, 

 Thos., the later names lucifer and cayennce being probably 

 due to the great variation which our now considerable 

 series from Demerara shows the animal to be liable to. 

 Normal specimens from this area are dark-coloured, with 

 blackish nape and darkened withers, the yellowish of the 

 rump dark fulvous, and the under surface brown, with but 

 little mesial lightening ; the feet usually black. In individual 

 specimens, however, all parts, and especially tlie rump, may 

 be very much lighter. 



In Brazil, on the otlier hand, the true D. aguti is always 

 much lighter, the nape and withers without blackening, the 

 under surface with a broad and distinct mesial line of white 

 or yellow running its whole length from chest to inguinal 

 region, the feet more or less grizzled with orange. 



But from the Moon Mountains a series of specimens differ 

 from both, and may be described as 



Dasyprocta aguti lanarisj subsp. n. 



Nape and fore back grizzled olivaceous grey, without any 

 blackening. Rump ociiraceous orange, generally darkened 

 by incons])icuous blackish subterminal bands on the hairs — ■ 

 the colour fairly unifoim in the series available. Flanks, 

 sides of rump, and legs grizzled olivaceous, the orange not 

 extending downwards on to them. Under surface scarcely 

 lighter than sides, without median light stripe on chest, 

 though there is generally an irregular whitish lightening on 

 the belly and inguinal region. Hands brown, blackish, or 

 grizzled. Feet grizzled olivaceous, only darkening to 

 blackish terminally. 



