138 Wortman — Studies of Eocene Mammalia in the 



fact, not only characteristically Primate, but one considerably 

 advanced. 



In one specimen the head of a humerus is associated with 

 a fragment of a lower jaw, which is apparently the proper size 

 for Hemiacodon gracilis. The character of this bone is dis- 

 tinctly Primate. Among the living forms, it bears a closer 

 resemblance to the humerus of Projpithecus and Avahis than to 

 any other with which I have compared it. This is particularly 

 evident in the relatively great development of the lesser tuberos- 

 ity and its inward and backward projection from the articular 

 head. In this respect it also resembles the humerus of Tarsius, 

 Hapale, and Cebus, although not so closely as it does that of 

 the genera above mentioned. The large size of the lesser 

 tuberosity is likewise a conspicuous- feature of the humerus 

 of Zimnotherium, from which it may be concluded that it is a 

 primitive character. 



Professor Marsh has given the following measurements of 

 the type : 



Longitudinal extent of the nine lower teeth 20*5 mm 



Extejat of premolar and molar series 11 '2 



Extent of true molars 11*0 



Antero-posterior diameter of last lower molar 4-0 



Transverse diameter of last lower molar. _ 2 # 4 



Depth of jaw below last lower molar 6*3 



The type specimen was found near Henry's Fork, by Mr. G. 

 G. Lobdell, Jr. The other specimens of the collection are 

 from the same horizon. 



Hemiacodon pygmceits sp. no v. 



A second species of this genus is indicated by a single 

 superior molar, figure 132. Under ordinary circumstances, I 

 1S o should deprecate the proposal of a 



new specific name upon such an 

 incomplete specimen, but in the 

 present instance the relationship is 

 so clearly indicated and the differ- 

 ences are so patent, that I do not 

 Figure 132.-Superior molar hesitate to follow ^ this otherwise 

 of Hemiacodon pygmceus Wort- reprehensible practice. 



man ; crown view ; four and The tooth in question displays 

 one-third times natural size. .^ undoubted affini ties with^ the 



molars of Hemiacodon gracilis, in 

 its quadrate outline, its relatively great transverse extension, 

 and the general arrangement of the cusps. The external cusps 

 are somewhat more conical than those of H. gracilis, but the 

 intermediate and internal cusps are practically the same as in 

 that species. The great difference is seen in the size, H. 

 pygmams being but little more than one-half as large as H. 



