Chap. V. TAILS OF MONKEYS. 307 



been made colonel of the new national guard. They 

 had been obtained with great difficulty in the forests 

 which cover the low lands, near the principal mouth of 

 the Japura, about thirty miles from Ega. It was the first 

 time I had seen this most curious of all the South Ame- 

 rican monkeys, and one that appears to have escaped 

 the notice of Spix and Martius. I afterwards made a 

 journey to the district inhabited by it, but did not then 

 succeed in obtaining specimens ; before leaving the 

 country, however, I acquired two individuals, one of 

 which lived in my house for several weeks. 



The scarlet-faced monkey belongs, in all essential 

 points of structure, to the same family (Cebidse) as 

 the rest of the large-sized American species ; but it 

 differs from all its relatives in having only the rudi- 

 ment of a tail, a member which reaches in some allied 

 kinds the highest grade of development known in the 

 order. It was so unusual to see a nearly tailless monkey 

 from America, that naturalists thought, when the first 

 specimens arrived in Europe, that the member had been 

 shortened artificially. Nevertheless, the Uakari is not 

 quite isolated from its related species of the same family, 

 several other kinds, also found on the Amazons, forming 

 a graduated passage between the extreme forms as 

 regards the tail. The appendage reaches its perfection 

 in those genera (the Howlers, the Lagothrix and the 

 Spider monkeys) in which it presents on its under-surface 

 near the tip a naked palm, which makes it sensitive and 

 useful as a fifth hand in climbing. In the rest of the 

 genera of Cebidae (seven in number, containing thirty- 

 eight species), the tail is weaker in structure, entirely 



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