NO. 2 A STUDY OF MENISCOTHERIUM — GAZIN 5'I 



highly concave anteroposteriorly and the glenoid or posterior border 

 is turned sharply outward. The concave glenoid surface is nearly 

 oval but somewhat compressed or acuminate at the proximally directed 

 anterior extremity. The coracoid process here exhibits a strong medi- 

 ally deflected flange or hook which is separated from the glenoid sur- 

 face by a distinct groove or notch, much as described by Cope for 

 Phenacodus. 



The most striking feature of the Meniscotherium scapula is the 

 very high but posteriorly deflected spine with its prominent antero- 

 proximally directed acromion and strongly recurved but posteriorly 

 directed metacromion. The spine apparently maintains nearly its 

 maximum height from the acromion to about its midpoint and distally 

 from there it tapers to the suprascapular border. The spine was 

 evidently broken off the various scapulae of Phenacodus available 

 to Cope, but an equivalent development of the acromion and meta- 

 cromion was observed on the Phenacodus skeleton exhibited at 

 Princeton University. 



There is apparently no evidence for a clavicle in either Menisco- 

 therium or Phenacodus. 



HUMERUS 



The limb bones of Meniscotherium appear to be relatively a little 

 smaller, in proportion to the size of the skull for example, and some- 

 what less robust than in Phenacodus. The humerus (see pis. 6 

 and 7) is slender and gently curved, more noticeably in the smaller 

 M. chamense, but shows, nevertheless, a prominent and elongate 

 deltoid ridge extending from two-thirds to nearly the entire length 

 of the shaft, giving the proximal portion of the shaft a somewhat 

 flattened (anteromedial-posterolaterally) appearance (see Cope, 

 1884b, pi. 25g, fig. 12). The development of this crest together with 

 the height of the spine and development of the acromion on the 

 scapula testify to the importance and leverage afforded the deltoid 

 muscle in abducting the forelimb. The proximal portion of the 

 humerus is characterized also by a prominently projecting crestlike 

 greater tuberosity, whereas the lesser tuberosity shows very little 

 proximal projection, although its medial prominence exhibits a notice- 

 able dorsomedial facet or scar for the subscapularis muscle. The tuber- 

 osities are separated by a broad bicipital groove but are closely joined 

 to the head, leaving little or no anatomical neck. Cope (1884b, p. 

 502) noted that there were no bicipital ridges, but these may be 

 weakly developed on some specimens. He also described a teres 



