22 ATELEUS 



with an unshakable firmness anything and everything it may touch, and 

 fulfilling in the highest degree and with an admirable service, the 

 purposes of a fifth hand. By it, fruits or other desirable objects other- 

 wise unattainable are seized and brought within reach of the mouth 

 or hands, and it also can hold its possessor suspended in the air, and 

 allow the hands and feet to act with complete freedom. While mem- 

 bers of other genera of the Order possess prehensile tails, in com- 

 parison with that of Ateleus they perform but a restricted service. 

 Another feature of this group is the absence of the thumb, existing in 

 a rudimentary condition in one or two forms, and this probably is an 

 advantage to the animal as it travels through the forest, permitting 

 without hindrance the long hand to slide over and grasp the branches 

 in its swift progress, which the opposing thumb, might at times prevent. 

 Against this theory, however, is the fact that the members of Hylo- 

 BATEs, of the Old World Apes, which are strictly arboreal animals, 

 and whose flight through the forest can only be compared in ease and 

 swiftness to the passage of a bird, possess very long thumbs. The 

 limbs of Ateleus are long, the arms exceeding the legs in length ; the 

 body is comparatively small, with the stomach protruding, and 

 covered with rather coarse long hair, but without any woolly under 

 fur. The lumbar region of the skeleton is short, but the dorsal segment 

 attains a greater relative length than in any other Monkey. 



The tail has twenty-three vertebrje, flattened beneath, and with 

 processes present for the attachment of muscles for increasing its 

 efficiency as a prehensile organ. A median air sac is situated in the 

 back of the larynx, but there is no such provision for increasing the 

 power of the voice as witnessed in the vocal apparatus of the Howling 

 Monkeys. 



LITERATURE OF THE SPECIES AND SUBSPECIES. 



1758. Linnsus, Sy sterna Naturce. 



Ateleus paniscus described as Simla paniscus. 

 1777. Erxleben, Systema Regni Animalis. 



In the list here given one species, Ateleus paniscus, is included 



in the genus Cebus. 

 1806. E. Geoffroy St. Hilaire, in Annales du Museum d'Histoire 



Naturelle, Paris. 



In this Memoir five species are included in the genus Ateleus, 



viz. : Le Chamek, A. pentadactylus = A. paniscus ; La Coaita, 



A. paniscus; L'arachnoide, A. arachnoides = Brachyteleus 



