CATARHINES. 441 



first premolar below continues longest prominent, and resembles a 

 small canine. (1) 



The premolars are implanted by two connate fangs, those above 

 becoming separate, and diverging near their extremities. The first 

 and second true molars above have three fangs ; the last has two 

 in Mycetes, and one in Cehus. Each of the lower true molars is 

 implanted, in Mycetes, by two fangs ; but the last has only one 

 fang in Cehus. 



All the platyrhine Monkeys have four more teeth in their 

 first dentition than the catarhine or old-world Quadrumanes 

 possess ; the deciduous formula being : — 



Incisors — : canines — ; molars — : = 24. 



2—2 ' 1—1 ' 3—3 



171. Catarhines. — In this division of the Order the first or 

 deciduous dentition consists, as in Man, of: — 



Incisors — : canines — ; molars — ^ : = 20. 



2—2 ' 1—1 ' 2—2 



The milk molars are displaced and succeeded vertically by the 

 bicuspid premolars, and are followed (2) horizontally by three true 

 molars on each side of both upper and lower jaws ; the perma- 

 nent formula in all the old-world Quadrumanes being : — 



Incisors — : canines — : premolars — : molars — : = 32. 



2—2 ' 1— 1 ' *^ 2—2 ' 3—3 



If a speculative morphological view were to be given in explana- 

 tion of the transition from the Platyrhine to the Catarhine type of 

 dentition, it might be said that the third premolar of Cebus had 

 been developed into a true molar, and the last true molar reduced 

 so low as to be confluent, as a fifth posterior tubercle, with the 

 second molar, now become the last true molar, in order to form 

 the dentition of the Baboons and Semnopitheques, at least of the 

 lower jaw (PL 116, fig. 2, m. 3) : the small size of the first true molar 

 in the Baboons, (ib. fig. 2, m. 1) would seem to give further counte- 

 nance to such an hypothesis ; but this tooth, like the other true 



(1) Duvernoy in Cuvier's Lemons d'Anat. Coinp. t. iv, (1836) p. 297. 



(2) This word refers to position in the jaw, not to time of appearance. 



