GREGORY: NOTHAHCTUS, AN AMERICAN EOCENE PRIMATE 



183 



THE SYSTEMATIC POSITION OF yOTlIARCTUS 



The general systematic relationships of Notharctus, as understood by the writer, are as follows. 



Order Primates 

 Suborder Lemuroidea 

 Scries Lemuriformes ' 



1. Postorbital process of malar joining p()st()rl)ital process of frontal, l)ut not extending inward 

 as a partition separating orbit from temporal fossa. 



2. Malar either touching lacrymal or barely separated from it by a narrow strip of the maxillary. 



3. Mid-cranial region long or not greatly shortened; pterygoid plate of alisphenoid extended ob- 

 liquely posteroexternally and joining glenoid and bulla; true pterygoid usually nearly in contact with 

 bulla. 



4. Expanded auditory bulla enclosing the tympanic membrane and tympanic annulus. Inflated 

 portion of bullse not greatly produced forward and inward toward the midline. 



5. Main branch of internal carotid typically of small size, running in osseous carotid canal over 

 the cochlea (except in Chirogaleinse) and piercing the basisphenoid. 



6. Pterygoid plate of alisphenoid pierced by "foramen pterygospinosum." 



7. Dental formula primitively If Ct PI Mf; variously reduced in specialized forms. 



8. Molars typically erupting early: m\ nr, m\ and nii, m2, nia in place with all the deciduous teeth. 



Family Adapidae 

 Eocene Lemuriformes of Europe and North America. 



Dental formula: Is Cj Pf Mf. Deciduous dental fornuila i)robably ' Dli DC-} DPf. Incisors 

 and canines not abnormally modified (lower canine more or less caniniform or premolariform, not pro- 

 cumbent or styliform; second low^er premolar not subcaniniform, not opposing upper canine). Central 

 upper incisors (i^) with compressed crowns. Lower incisors not sharply procumbent, wdth more or less 

 truncate-spatulate crown. Protoconule of ui)pei- molars forming with the protocone a prominent obliciue 

 crest (protoloph)! Metaconule, when distinct, tencUng to connect metacone and protocone. Upper 

 molar cingula well marked. Hypoconulid of ni;! distinct. Brain-case small or not greatly expanded. 

 A marked constriction of the skull l)ehind the orbits. Orl)its of moderate size. Lacrymal not expanded 

 on face but lying within the orbit; lacrymal foramen marginal. Zygomatic arches stout; masseteric 

 tubercle of malar well marked. Sagittal and lambdoidal crests typically high; occiput triangular. Mid- 

 cranial region long; pterygoid plate of alisphenoid large. Mastoid forming a backwardly directed 

 tuberosity, partly embraced by the paroccipital process of the exoccipital. Entrance of internal carotid 

 at posteroexternal angle of bulla. 13rain macrosmatic with large olfactory lobes, small frontal lobes and 

 small cerebellum. 



1 Gregory, K. 1915. On the classifieation and phylogeny of the Lemuroidea. Proc. Paleontol. Soc. Bull. Geol. Soc. America, 

 XXVI, pp. 423-442. 



- Only partially known in Nolhnrdus. 



