218 



GREGORY: NOTHARCTUS, AN AMERICAN EOCENE PRIMATE 



Fenestra Cochlea? (f. rotunda) 



Auditory l)ulla 

 Hypotympanic Sinus 

 Tympanic 



Carotid Foramen 



Carotid Canal ("arteria pro- 

 montorii") 



Stapedial Canal 

 Foramen Ovale 

 Foramen Lacerum Posterius 

 Foramen Civininii (pterygo- 

 spinosum ) 

 External Pterygoitl Plate 



Temporal Flange of Squamosal 

 Postglenoid Foramen 



Notch between Vertical Plate 

 of Palatine and Alveolar Re- 

 gion of Maxilla 



Pterygoid Fossa 



Palate 



Upper Dental Arch 

 Dental Formula 

 Probable Deciduous Formula 

 Arrangement of Upper Incisors 

 Central Upper Incisors 



Upper Canine 



Lower Incisors 



Lower Canine 



I'pper Premolars 



Lower Premolars 



Upper Molars (m\ nr) 



Notharctus 



Concealed by the post-tympanic pro- 

 cess from a view from the outside 

 through the tympanic ring 



Small, subcircular 



Enlarged, empty 



Slender, within bulla 



At posterolateral angle of bulla 



RuuTiing along lateral surface of 

 cochlea (promontory), piercing basi- 

 sphenoid, probably emerging lateral 

 to sella turcica 



Present 



Small 



Small 



Piercing external pterygoid plate 



Producetl postero-externally to con- 

 nect with anterolateral process of 

 bulla and entoglenoid process of 

 squamosal above Eustachian fora- 

 men 



Elongate anteroposteriorly, with 



sharp supra-audital crest 

 Prominent 



Open 



Slight (pterygoid closely appressed 



to ext. pterygoid plate) 

 Moderately elongate 

 Moderateh- elongate 

 If Ci P| M| 

 DI| DC^ DP| 

 /\ shaped 

 (Jompressed 



Subcaniniform 



Small, gently procumbent, with 



truncate spatulate crowns 

 Subcaniniform 



P^ present, p'-, p^ p^ successively 



more complex 

 Pi present, po, ps, p4 successi-\'ely 



more complex, p4 with incipient 



trigonid and talonid 



Quadritubercular with well de\el- 

 oped external cingulum anfl meso- 

 style 



Generalized Platyrrhine 



(P) Plainly visible, after the remo\ al of the tym- 

 panic membrane; lying below and behind 

 fenestra ovalis 



(P) Elongate anteromedially 



(P) Reduced, cancellous 



(P) Expanded medially, lateral to bulla, which 

 it overlaps 



(P) Shifted medially, opening at posteromedial 

 end of bulla 



(P) Deeply buried in the petrosal, not piercing 

 basisphenoid, emerging at posterolateral 

 angle of sella turcica 



(P) Absent (Tandler) 

 (P) Large 

 (P) Large 

 (P) Absent 



(P.P.) Separated from anterolateral process of 

 bulla and entoglenoid process of squamosal 

 by a wide vacuity 



(P) Abbre^'iate, with faint supraorbital crest 



(P) Typically reduced or absent, occasionally 



prominent 

 (P) Converted into a tunnel 



(P) Moderate 



(P) Short and wide 

 (P) Abbreviate 

 (P) If C^ P| M| 

 {Prim) DI§ DC^ DPf 

 (P) n shaped 



(P) Enlarged, witli transversely widened trun- 

 cate crown 



(P) Small, not tusk-like; often becoming tusk- 

 like 



(P) Often with wider crowns, but essentially 

 similar to those of Notharctus 



(P) Subcaniniform with short crown. Tusk-like 

 canines secondary (P) 



(P) Pi absent, p=, p^ p* typically bicuspid (P) 

 (more primitive in Callithrix) 



(P) Pi absent, po typically larger than p3 (P), 

 with vertically extended pro toconid,, oppos- 

 ing upper canine, and well marked internal 

 cingulum; ps, p4 bicuspid (P) with much 

 reduced talonid (P) 



(P) Quadritubercular wtih . reduced external 

 cingulum and mesostyle. Tribubercular 

 groundplan preserved in Callithrix, Nydi- 

 pithccus; mesostyle present in Mycetes 



