GREGORY: XOTIfARCrirS, AN AMERICAN EOCENE PRIMATE 



109 



centra narrower and shallower, the zygapophysial processes less extended transversely; the lumbars 

 are more elongate, with wider parapophyses; the tail is very much lighter, more slender and is not pre- 

 hensile; the sacral vertebrae are smaller and less expanded laterally. In the marmosets (Hapalidse) 

 the lumbar centra are relatively narrower than those of Nothardus, but both the sacrals and the caudals 

 are in some respects intermediate in form between those of Nothardus and of Cehus. In the Old World 

 monkeys, represented by the macaciues, the dorsal and lumbar centra are much wider transversely, as 

 well as the zygapophysial processes. 



Atlas. — The atlas of Nothardus is represented by two incomplete specimens associated respectively 

 with A'", osborni, Amer. Mus. No. 11474, and N. tyrannus, No. 11478. This atlas, so far as preserved, 



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\ 



12 o 4 .5 



]m<;-. Conipiinitivc series: atlas of Noflxirdtis (1 ), Ij'iinv (2), (V/^z/.v (3, 4), Maracus (5). Natural size. 



Top row : anterior or cephalic view. 

 Middle row: posterior or caudal view. 

 Bottom row: dorsal view. 



1. Nolharctusosbonii. Amer. Mus. No. 11474. 4. Cebus hijpoleuciis. Amer. Mus. No. 1401G. 



2. Lemur mongoz. Amer. Mus. No. 22886. o. Macacus nemestrinuA. Amer. Mus. No. 14012. 

 8. Ccbus apiculatus. Amer. Mus. No. 30200. 



The general course of the vertebrarterial artery and of the suboccipital nerve in relation to the foramina of the atlas are indicated 

 by black and white threads respectiveh^ 



is clearly of the primate type, and differs from that of creodonts in ha\4ng the transverse process much 

 smaller and narrower, the neural arch narrower anteroposteriorly, and the posterior facets for the axis 

 smaller; these characters being associated Avith the less powerful neck muscles of the primates. The 

 atlas agrees closely with that of Lemur inongoz, No. 31254, except in the following points. (1) The smaller 



