160 



GREGORY: NOTHARCTUS, AN AMERICAN EOCENE PRIMATE 



The fossse on the surface of the occiput below the lambdoidal crest probably mark the insertion of the 

 deep muscles which run to the spine of the axis and raise the head, namely, the rectus capitis posticus 

 major; while to the region above the foramen magnum may have been attached the atloido-occipitalis, 

 which arose from the stout arch of the atlas. The large and protuberant mastoids probably gave attach- 



Fig. 57. Neck muscles of Propithccu.s, 

 after the removal of the rhomboideus and 

 trapezius, showing the complexus (/v, L) 

 and the rectus capitis posticus major. 



ment dorsally to the trachelo-mastoid (running along 

 the side of the neck vertebra), to the cleido-mastoid, 

 sterno-mastoid and digastric. Above the mastoid 

 and below the lambdoid crest the obliquus capitis 

 superior was probably attached. From the sharply 

 ridged character of the occiput even in the female 

 Notharctus it seems likely that although these neck 

 muscles were less thick transversely than in Adapts 

 they were yet vigorously developed. (Figs. 56, 57.) 



The mastoid process is much larger and more 

 protuberant in the male A^. crassus than in the female 

 N. osborni; as compared with that of Adapts, it is 

 more swollen below and tapers rapidly to a dorsal 

 point while in Adapisit extends dorsally as a wide strip. 

 The jugular or paroccipital process of the exoccipital 

 embraces the inner side of the mastoid as it does in 

 Adapts. Above the exoccipital is a slit or foramen 

 at the bottom of the fossa for the rectus capitis pos- 

 ticus major (?), which recalls the similarly located 

 foramen in Adapts. StehUn (1912, p. 1200) suggests that this foramen may have served to give entrance 

 to the "Arteria meningea posterior," a branch of the occipital artery. The mastoid foramen near the 

 posterior border of the mastoid is prominent. It is not located between the mastoid and the exoccipital 



Fig. 50. Occipital view of skull. Natural 



size. 



Amer. Mas. No. 11466. 

 After Stehlin. 

 After Stehlin. 



Notharctus osborni. 

 Adapts parisiensis. 

 Adapis parisiensis. 



J, jugal; P.gL, postglenoid process; T.h., tym- 

 pano-hyal insertion; i/j, exoccipital ; M., mastoid; Au, 

 auricular meatus; F.p., postglenoid foramen; B, au- 

 dital bulla; Or., fossa for neck muscle, leading to " fora- 

 men arteriae meningeae posterioris " ? 



1 Not to be confused with the posterior meningeal branch of the pharyngeal artery. 



