1896.] lil [Farr. 



The Milk Dentition. 



In the Princeton Collection there is a skull bearing the temporary den- 

 tition (No. 11168). In the young skull the anterior border of the orbit 

 is just between D. 4 and M. 1, so that as growth takes place the orbit is 

 forced to retreat by the elongation of the facial region of the skull, as in 

 the adult skull the anterior border of the orbit is over the interval be- 

 tween molars 2 and 3. The milk teeth agree in all essential points with 

 those of M. bairdi. 



Measiu'ements of the Superior Milk Teeth. mm. 



Length milk series 57 



D. 1 10 



" 2 18 



" 3 16.5 



" 4 17 



The lower teeth of the deciduous set agree in all their characters, ex ■ 

 cept size, witli tliose oi M. bairdi. 



There is nothing noteworthy about the vertebrae except their increase 

 in size over those of M. bairdi. Tlie limbs bear the same general pro- 

 portions as in the smaller species. The scapula is higher and narrower 

 proportionately than in M. bairdi. All the limb bones are characterized 

 by being much longer than in the smaller species. The ulna is not more 

 reduced distally than in M. bairdi, and is distinct from the radius through- 

 out. The shaft is compressed laterally and is very slender, but distallj' 

 it is stouter and has a large facet for the cuneiform. Proximally the 

 olecranon is more massive than in M. bairdi. The radius is very large 

 and is fast becoming the important bone of forearm. The carpus pre- 

 sents no important difi'erences from that of the smaller species. It is 

 still high and narrow. A rudiment of the fifth metacarpal still persists, 

 but is not so elongate as in M. bairdi, but is shorter and stouter and on 

 the way to disappearing. The lateral digits are usually more flattened 

 than in the smaller species but are not more reduced, the distal ends 

 being even more massive proportionately. The ungual phalanges of 

 the lateral digits are long, narrow and sharply pointed at the ends. 

 That of metacarpal iii is proportionately wider than that of M. bairdi. 



MM. 



Length of M. iii 155 



M. iv 138 



M. ii 143 



The ribs are characterized by their length and extreme slenderness, 

 those of the median dorsal region being especially long, not much flat- 

 tened, being almost round in cross-section. The pelvis presents few 

 characters that are new. The ilia expand even more gradually than in 

 M. bairdi. The angle rises up in a pointed process. The crest is partly 



