92 DR. E. A. GOELDI ON MARMOSET [Jan. 15, 



Having now j&uislied these explorations of the treasures stoi'ed 

 np in the British Museum as an essential preliminary and 

 solid basis for the discussion of the respective questions that arise, 

 I will proceed to the detailed description of the two new species 

 of Marmoset Monkeys of the Purus Region, mentioned at the 

 beginning of the present article. 



Midas griseo vertex, sp, n. 



In general aspect closely similar to M. rufiventer Gi'ay and 

 M. thomasi Goeldi, in the sharp contrast between the bright 

 rusty-coloured abdominal side and the dark colouring of the 

 dorsal aspect, but distinguishable at a glance by the greyish- 

 white, good-sized rounded frontal patch. 



Among the collections made in the Purus and Acre Regions 

 by our Museum Expeditions (1903-1904) there are seven indi- 

 viduals of this most interesting and well characterised species of 

 Marmoset Monkey (skins, skulls of all and trunks of some), 

 4 being males and 3 females. One mounted pair ( c? § ) remained 

 in the Mviseum at Berne, labelled as above ; three mounted indi- 

 viduals ( J' , 5 , and a half- grown young one) are kept in the Para 

 Museum ; and the remaining pair of skins ( cJ $ ) are intended for 

 the British Museum. 



Dorsal aspect. — General colour deep blackish-brown, excepting 

 head, hands, feet, and tail, which are positively black. This 

 colour remains pure from the nape of the neck backwai'd for 

 one-third of the length of the back. The hinder two-thirds of 

 the back shows a mottling due to the light greyish tips of the 

 hairs, which terminal points measure about \ of the entire length 

 of the hair and are slightly longer toward the hips ; the intensity 

 of the mottling increasing gradually backwards, being most pro- 

 nounced in the sacral region, presenting even a whitish appearance, 

 when seen from certain oblique dii-ections. 



On separating the fur in the region of the shoulders, the 

 impression of colour is in general the same as the exterior, that 

 is deep blackish- brown, excepting that the lower third of the 

 hairs towards the roots forms a slightly lighter zone, especially 

 laterally to the median line. Making the same examination in 

 the region of the hips, the light zone is scarcely apparent, the fur 

 being of the genei\al colour almost down to the roots. 



Head. Genei-al colour sooty-black. A narrow zone of whitish 

 hairs bordering the whole extent of the mou.th. In the i-egion 

 of the upper lip the white zone rises in a very conspicuous 

 triangular zone, with its broad base resting on the circular white 

 band of the mouth. One very noteworthy feature of this 

 triangular zone is that the lateral oblique lines cross exactly 

 the middle of the nostrils, so that the exterior half of each 

 falls in the blackish region, the interior half in the whitish 

 triangle. 



At the vertex, from a line connecting the anterior borders 

 of the ears, commences a whitish patch (text-fig. 22), occupying 



