86 



(;he(i<)Ry: xotiim^cti's, an American eocene primate 



3. The blade of the ihuin of lemurs, in side view, is narrow, and the gluteal fossa is deeply exca- 

 vated, while in the Cebida^ it is flatter and considerably more expanded, the gluteal fossa being shallow. 



4. Immediately in front of the acetabulum in Noiharctus and in the lemurs there is a very promi- 

 nent process, homologous with the anterior inferior spine of the ilium of man; it is elongated antero- 

 posteriorly, compressed laterally and roughened along its summit; in recent lemurs this process serves 

 for the attachment of a strong ligament that runs forward and is attached to the anteroinferior process 

 of the iliac crest; this ligament extends the area of origin of the gluteal and of the iliacus muscles, and 

 also gives the partial attachment to the sartorius muscle. The process itself also gives attachment in 

 part to the sartorius muscle, and immediately behind this to the powerful rectus femoris muscle. The 

 anterior border of the process runs forward into the sharp concavity of the lower border of the ilium. 

 In the Hapalidse this anterior inferior process is still present, although less defined than in Notharctus. 

 In the Cebidse it is confluent with the anterior border of the ilium; in the ('ercopithecidse it is barely or 

 not at all visible. Vestiges of it may be seen in the gibbons and in some old gorillas and chimpanzees; 

 it is practically absent in a young gorilla; it is a little better developed in the orang. The enlargement 

 of the process in man is no more to be regarded as a primitive character than is the wide expansion of 

 the ilium. (Fig. 13.) 



5. The articular surface for the sacrum, on the inner side of the ilium, which is best shown in No. 

 11479, is almost identical in form with that of the Lemur, and is much shorter than that of the Cebidffi, 

 since it articulates only with a single vertebra. (Fig. 12.) 



(). The pubis of Notharctus is not preserved, but from the close similarity of both the iliiuu and the 

 ischium to those of lemurs, it is cjuite likely that the j^uliis was less extended anteroposteriorly than 

 it is in Cehus, and that the anterior pelvic opening, or ])eh'ic inlet, was more restricted dorsoventrally. 

 The anterior opening or inlet of the pelvis in Notharcliis and in the lemurs is also l)()unded by a sharp 

 rim on the ilium, which is reduced in South American monkeys. (Fig. 12.) 



7. The ischium resembles those of lemurs, especially Lepilemur, except that it is larger; it differs 

 markedly from the ischium of the New World monkeys in not having the ischial tuberosity widely averted, 

 because the lemurs do not sit upright. A small ischial spine is present, similar to that of Lepilemur. 

 It probably gave attachment on the inner side to the ischio-coccygeus and on the outer side to the gem- 

 melli (cf. the dissection of Propithecus, Milne Edwards, PI. 68, fig. 3) as it does also in other primates, 

 including man. (Figs. 13, 14.) 



8. The acetabulum with regard to both form and position closely resembles that of Lemur, and 

 differs from those of the Cebidse in that the anterior and posterior lips of the acetabulum are elevated, 

 and the contour as a whole is less circular. (Fig. 12.) 



The whole configuration of the pelvis of Notharctus indicates that the animal was an arboreal ciuad- 

 ruped which did not sit fully upright but leaped about on all fours among the branches. 



With regard to the musculature of the pelvis, the form of the ilium shows that the gluteal series 

 and the iliacus, in form and projjortion, were like those of modern lemurs. The narrow lower face of 

 the blade of the ilium indicates corrresponding proportions for the iliacus and psoas muscles, the areas 

 for which are much wider in monkeys. The widely everted anterior blade of the ilium, which leaves a 

 wide space between the blade and the lumbar centra, gives space for the widely extended transverse 

 processes of the lumbars and for bulky quadratus lumborum, psoas, erector spinse, superior and inferior 

 sacro-coccygeal muscles. In Cehus the blade is not everted and the transverse processes of the lumbars 

 are less extended transversely. The marked prominence of the anteroinferior proe;\ss of tlie ilium is a 

 primitive lemuroid character present also in the Menotyphla; it implies the presence of a strong ligament 



