1907.] 



MONKEYS FROM THE AMAZONIAN REGION. 



89 



Midas thomasi, sp. n. (1905). 



[Labelled in the British Museum : " Midas rufiventer, S , 

 ' The red-bellied Tamarin,' Upper Amazonia. W. Bates. 

 Exp. 1857 a, Tunantins, north side of Amazons."] 

 Dorsal aspect. — Anterior half of a dark, deep blackish-brown 

 colour (somewhat like the half-grown J/. fuscicoUis), extending 

 from behind the ears as far as the middle of the back. Hinder 

 half of the same brown, the tips of the hairs being however 

 mottled with a lighter greyish-brown, but in a much less pro- 

 nounced degree than in the typical M. rufiventer. 



Head (text-fig. 20) black, with an insignificant median small 

 light spot beginning just between the ears, behind the vertex ; 

 a still less noticeable lightish dash, consisting only of a few 

 greyish hairs, almost forming an anterior continuation, is per- 

 ceptible in the same median line just in front of the former. 

 Details of the region of mouth and nose as in the type of 

 M. rufiventer. 



Text-fig. 20. 



Back view of head, of 3Iiclas thomasi. 



Arms dark blackish -brown, passing into a true black towards 

 the hands, not being, however, a brilliant black as in the 

 M. rufiventer type. 



Legs. Exterior side of thighs of the same coloui- as the posteiior 

 half of the back, turning to black toward the feet. 



Tail black. 



Yentral aspect. — Anteriorly a cross-zone of light reddish- 

 yellow (viz., inside of arms and a band across the breast as wide 

 as the insertions of the arms). Rest fi-om there backwards reddish 

 rust-yellow (lighter than in the new species M. griseoveriex G., 

 and mvich lighter than in M. rufiventer type). 



The light under side is abruptly separated in the region of the 

 neck and breast from the black of the neck and head. (This 

 light abdominal colour cannot be attributed to fading of an old 



