112 



GREGORY: AWniARCTUS, AN AMERICAN EOCENE PRIMATE 



the long axis of the centrum, whereas in Lemur mongoz it is more inchned. The centrum is much less 

 expanded transversely than is the case in Macacus, is flatter inferiorly than that of Cehus, but is not 

 nearly so flat or wide as that of Alouatta. Very probably the transverse processes in Notharcius were 

 smaller and less extended laterally than are those of Cebus and still less than those of Macacus. 



Dorsals 2 to 8 are represented by the centra in No. 11474, which agree so closely with those of Lemur 

 mongoz that it is highly probable that the transverse processes, neural arches, and other features were 

 equally lemurine. (Plate XXXII; Fig. 27.) 



dill ^ il'\v. Xi 



ative 

 size. 



.al and luinl,a 



[■tel. 



10 



Xiithiirctii.^- and other Primates. Posterior or 



1. 8th (?) dorsal , , • . at 



, ) Nolhnrcliis osborm. Amer. Mus. No. 11474. 

 6. 3rd (?) lumbar J 



2. 8th dorsal 1 , , at >t -v^m,. 

 ,-, , , , } Lemur inonQoz. Amer. Mus. No. 2288(>. 



t . ■Ird lumbar 1 



o ^^'^^ "^'oisal j (^gJJ^^g hi/polencus Amer. Mas. No. 14016. 



8. 3rd lumbar J 



4. 7th dorsal 1 ^, . , , . 



,, , / Cebus aincidnliis. Amer. Mus. No. 30200. 



9. 3rd lumbar J ' 



5. 9th dorsal • . . , a, n- , 



., , , , , Macaraa nenicslrinns. Amer. Alus. No. 14012. 

 10. 3rd lumbar 



These lemurine dorsal vertebrae contrast with those of carnivores in having the centra more con- 

 stricted or angulate in the median line below and the neural spines very much lower, especially in the 

 anterior dorsals, the neural arches being more elongate, flatter and wider on top; the metapophyses, 

 which lie external to the zygapophyses, in the lemurs, as seen from above, are directed forward rather 

 than outward and are more protuberant and rounded; in the carnivores they are often more elongate 

 anteroposteriorly ; in the lemurs the facets for the ribs at the end of the transverse processes are larger 

 and more circular. These and other differences in the neural arches and zygapophyses are associated 

 with the markedly different shape of the thorax, which in lemurs, as in other arboreal animals, is widely 

 bowed outward and shallow vertically, whereas in carnivores the thorax is typically compressed and 

 deep. 



The dorsals of Nothnrctiis and Lemur are relatively smaller than those of Cehus and Macacus. 



