GREGORY: NOTHARCTUS, AN AMERICAN EOCENE PRIMATE 



217 



CX)MPARIS()X OF XOTIIARCrrs WITH THE PLATYRRHIXI 

 Plates XLVI, XLIX, L, LIX 



All the existing South American monkeys are highly speciahzed and even the Santa Cruzian genus 

 Homunculus is of modernized type, so that there is no direct pateontological evidence as to the characters 

 of the stem form of this relatively compact, but fairly diversified, natural group. After prolonged, 

 repeated comparisons of all views of the skull of the platyrrhine genera it is here adopted as a working 

 hypothesis that the common ancestral form had the following characters in contrast with Nothardus 

 (P., progressive; Prim., primitive, R., retrogressive, reduction) : 



Brain and Brain-case 



Face 

 Orbits 



Frontals 

 Parietals 



Postorl)ital Constriction 



Interorbital N^asal Region 

 Zygoma 



Lacrymal Duct 



Lacrymal 



Lacrymal Foramen 

 Malar 



Zj'gomatic Process of Malar 

 Jaw 



Mandibular Symphysis 

 Motion of Jaw 

 Occiput 



Mastoid 



Crista Petrosa 



Petrosal behind int. aud. 

 meatus 



Nothardus 



Small, with sagittal and lanilx 

 crests 



Long, nearly in line with l)rain-ci 



Directed partly outward 

 Xot closed posteriorly 



Expanded between orbits, posterior 



extension over I)rain small 

 Normal 



Marked 



Wide (macrosmatic) 

 Elongate, ele^■ated 



Probably sloped gently toward nasal 

 opening 



At anterior corner of orbit behind 



crista anterior 

 Immediately behind crista anterior 

 X'early or quite in contact with 



lacrymal 



Probably ending in middle of zygo- 

 matic arch 

 Elongate, with narrow angle 



Suture distinct on surface 

 Chiefly ental 



Narrow and pointed above 



Bearing a prominent tuberosity, 

 which is more or less cancellous. 



Excluded from brain-cavity by peri- 

 otic 



Not developed 

 Short 



Cieneralized Platyrrhine 



(/') Large, ex])anded A ertically, transversely and 

 anteroposteriorly. Much produced poste- 

 riorly, without sagittal and lambdoid crests 



[P) Short, depressed and deepened below brain- 

 case 



(P) Mo\ ed forward, lateral borders protruding 



(P) Closed posteriorly by a flange from the malar 

 which grows inward between the temporal 

 muscle and the orbits 



(P) Restricted between orbits; posterior exten- 

 sion over brain large 



(7^) Extended forward, often gaining contact with 

 postorbital lamina of malar and separating 

 the frontal from the alisphenoid 



(P) Nearly obliterated by expansion of frontal 

 region of brain 



{R) Restricted (microsmatie) 



(P) Short, robust, widely arched outward, sharply 

 decur^'ed and depressed 



(P) Steeply inclined. Duct enlarged 



(P) Same, but deepened A'crtically 



Same, or piercing middle of lacrymal (P) 

 (P) Moved away from lacrj'mal (separated from 



it by wide exposure of maxilla) 

 {Prim.) Ending in middle of zygomatic arch 



(P) Very short and deep with much expanded 



angle (correlated with robust masseter) 

 (P) Opposite rami completely coalesced 

 (Prim.) Ental to Orthal 



(P) Very wide above, with broad exposure of 



supraoccipital and interparietal 

 (P) Greatly expanded, thin, without tuberosity, 



forming part of lateral wall of brain-cavity 



(P) Forming a wide septum, in the tentorial plane 

 (P) INIuch expanded 



