CRECiORY: XOTIIMiCTrs, AN AMERICAN EOCENE PRIMATE 



75 



But these specializations cannot conceal the very evident relationshiji of structural ancestoi- and 

 descendant. 



The humerus of Chironiys enijihasizes certain featui-es already foreshadowed in Xotharctxs and is 

 also allied to the Propithecus type, but more primitive. The supinator crest ends above in an angulate 

 corner. The outer lip of the trochlea is well developed but not the inner lip, this indicating that the 

 forearm could be supinated further than it could be in Nothardus} 



In Galago crassianidala the humerus is obviously derived from a more ])rimitive X()tli<ir<iu.s-\\ke type 

 by slight changes in jii'oportions. The head is large, the delto-pectoral crest has a fairly prominent emi- 

 nence, the small entocondyle is directed partly backward. In the delicate Galago allevi the humerus 

 is elongate, with narrow upper end but sharply marked low crests. In the jiotto (Perodirticits polio) 

 the great tuberosity is low and the deltoid plane much flattened. In /.o; /,s the humerus is l(Mig with 

 abortive crest. It will be recalled that all the members of this family are good climbei's but that the 

 galagos are exceedingly acti\'e while the lorises are sluggish, clinging tightly to the branches. 



In Tarsius the humerus is rather different from any of those hitherto noted. The supinator crest 

 flares backward, abolishing the depression which in Notharctus lies between the edge of the supinator crest 

 and the shaft. The bridge over the entepicondylar foramen is nearly vertical (i. e., more neai'ly parallel 

 to the shaft than is the case in N^otharctus). The entocondyle is delicate and slightly curved downward; 

 the tuberosity for the teres major is near the upper end of the shaft. There is no distinct round pit for 

 the tendon of the teres minor; the deltoid plane is fairly well indicated. Comparison of the humerus of 

 Tarsias with those of Noihodecies and Notharcius shows that in the upjier end of the humerus Tarsius is 

 more like Nolharclus while the flaring sujiinator crest on the lower half is a point of resemblance with 

 Nolhodectes. 



Comparison of the humerus of Nolharclus with those of Hapale (Fig. 7.6), Callithrix, Lagolhrix, 

 Alouaita, Chrysolhrix, and Cebus (Fig. 7.5) shows that in these platyrrhine genera the humerus has pro- 

 gressed away beyond the primitive .Voi/m/T;M.s-like stage, in the direction of the higher primates. Cebus, 

 Chrysolhrix, Callilhrix retain the entepicondylar foramen; while in the Hapalidte it is variable and in 

 Alouatta and Lagolhrix it is absent, at least in the few specimens at hand. The humerus of Aloualla, 

 a typical platyrrhine, differs from that of Xothardiis as follows: 



(1) The shaft is long and straight. 



(2) There is a long, very flat deltoid i)lane, latei-al to the very low and barely distinct delto-pecloi'al 



ridge. 



(3) The bicipital groox'e is but faintly indicated. 



(4) The tuberosity for the teres major is not defined. 



(5) The supinator crest is barely indicated and is long and straight. 

 (()) The shaft below^ the delto-pectoral ridge becomes flattened. 



(7) The entocondyle is massive and is directed partly downward. 



(8) The entepicondylai' foramen is entireh' absent. 



(9) The inner lip of the trochlea is sharply jironounced and there is no outei' lip. 



(10) The capitellum is larger. 



(11) The trochlea extends further around on to the dorso-posterior side and the olecranal fossa is 



deeper. 



' The humerus lends no support to Dr. Wortman's view (1903, p. 411) that Chiromyn represents a separate Rraiul division of the 

 I'rimates (■onr(Unate with the I.emuroidea and the Anthrojioidea. 



