EXTERNAL CHARACTERS OF THE SOUTH AMERICAN MONKEYS. 91 



9. On the External Characters of the South American 

 Monkeys. By R. I. PococK, F.R.S. 



[Received February 23, 1920 : Read March 16, 1920.] 



(Text-figures 1-13.) 



Contents. 



Pag-e 



Introduction 91 



The Nostrils 92 



The Ear 94 



The Hands and Feet 97 



The Tongue 104 



The External Genitalia of the Male 109 



The External Genitalia of the Female 105 



The Tail 112 



Introduction. 



The observations recorded in this paper are based mainly upon 

 the Platyrhine Monkeys that have died in the Zoological Gardens 

 during the past ten years* ; and the subject-matter is treated on 

 the lines adopted in my paper on the Lemurs and Tmsius (P. Z. S. 

 1918, pp. 19-53). Since I described the hands and feet and the 

 ears of the Hapalida? in 1917 (Ann. Mag. Nat. Hist. (8) xx. 

 pp. 247-258), my notes, so far as that family is concerned, are 

 in the present case restricted for the most part to the externa] 

 genitalia, the species examined being Hapale jacchus, Mystax 

 ursidus, midas and mysta,v, CEdipomidas ctdipus, and Leontocehus 

 rosalia. 



Of the Cebida?, I have seen examples of all the admitted genera, 

 except Pithecia and Brachyteles ; but 1 have not seen both sexes 

 in all cases, and in many instances immature specimens only have 

 been available. These defects ai-e regrettable, since the external 

 genitalia promise to yield valuable diagnostic characters for the 

 genera. 



The immaturity of specimens also makes their specific identity 

 doubtful. Very little indeed appears to be known of the range 

 of variation in colour and structure within specific limits. It 

 is not an uncommon event, for instance, to receive in our 

 Zoological Gardens immature examples of Ateles exhibiting 

 characters of at least two admitted species and assuming perhaps 

 those of a third with growth. 



I have examined examples of the following genera. Where the 

 species are doubtful they are marked with an interrogation, 



* I am indebted, however, to Prof. J. P. Hill, F.R.S., for the opportunity to 

 examine adult examples of Callicehus personatus nigrifrons collected by himself 

 at Minas Geraes. 



