Xlainmals from the Lower Amazon. 85 



CaJlilhrix argentata, L. 

 J. 1, 2. Maraiu, Ilio Tapajoz, near Santarem. 



CalUthrix santaremensis, Matscli. 

 S • 14. Boim, Rio Tapajoz (Friiulein E. Snethlage). 



Leontocebus martinsi, sp. n. 



c? . 1, 2 (young), 3, 31 (young) ; ? . 5. Faro, Lower 

 \aiuundji River {Oscar Mar(i'if<). 



Precisely like L. bicolur, except that the head and fore 

 limbs are of normal coloration, corresponding to the rest of 

 tiie animal, not sharply contrasted white. 



Head (in adult) naked from crown to chin, the skin black. 

 Scanty hairs of back of crown and the nape black or brownish 

 black. General colour of back and sides Isabella, darkened 

 along the dorsal area^ the middle posterior back almost 

 blackish. Under surface tawny ochraceous, duller ante- 

 riorly, richer posteriorly. Ears quite naked, black. Arms 

 proxinially isabella, buffy yellowish on forearms, hands 

 cream-butf or rather more yellowish ; whole inner side of 

 aims ochraceous. Hind limbs externally isabella, becoming 

 suffused with tawny towards ankles ; inner aspect rich 

 ochraceous, tending towards ochraceous rufous. Feet 

 yellowish buffy. Tail black above nearly to the tip ; under- 

 side and end shar|)ly defined ochraceous. 



Young specimens with the crown well-haired, blackish 

 mixed with greyish ; face and chin thinly haired, greyish ; 

 ears with black hairs about half an inch in length. 



kSkuU and teeth essentially as in L. bicolor. 



Dimensions of the type (measured in the flesh) : — 



Head and body 208 mm. ; tail 366 ; hind foot 61 ; ear 31. 



Skull: occiput to gnathion 51; basion to gnathioa 36; 

 zygomatic breadth 35'5 ; breadth across orbits 28*8 ; breadth 

 of brain-case 27*5 ; length of upper cheek-tooth-series 10. 



Type. Adult male. B.M. no. 11. 12. 22. 2. Original 

 number 3. Collected 27th April, lUll. 



This beautiful and interesting new marmoset, which I 

 have much pleasure in naming after its discoverer, is an 

 exact replica of L. bicolor in its naked head and in its colora- 

 tion posterior to the head and fore limbs. But instead of 

 having these, as in L. bicolor, conspicuously contrasted pure 

 wiiite, they are coloured quite normally in correspondence 

 Avith the rest of the animal. It might therefore have been 

 presumed that the present was a more ancestral form, frop' 



