366 Bulletin American Museum of Natural History. [Vol. XXVII, 



the mastoid is not exposed externally in Arsinoltherium and is barely so in 

 Hyrax. In Arsinoltherium. the post-glenoid and post-tympanic form a 

 tubular meatus which might readily be derived from the conditions in Hyrax. 

 In both genera there is an alisphenoid canal and the condyles are widely 

 separated. 



Arsinoltherium resembles the contemporary Proboscidea in the following 

 features : 



(1) The premaxillaries are excluded by the nasals from contact with the 

 frontals. 



(2) The lachrymals are widely separated from the nasals by the 

 frontals. 



(3) The post-tympanic and post-glenoid processes tend to bridge over 

 the auditory meatus. 



(4) The paroccipital process is closely appressed to the post-tympanic. 



(5) There is no condylar foramen. 



(6) An alisphenoid canal is present. 



(7) The fore arm and manus parallel those of EJephas closely in many 

 details and leave little doubt that both have been derived from forms having 

 a serial type of carpus, with a tendency toward reduction of the radius and 

 enlargement of the ulna, and with a correlated tendency toward reduction 

 of the scaphoid and broadening of the cuneiform. 



Arsinoltheriuvi resembles the Dinocerata chiefly in the ectal spreading 

 of the astragalus over the cuboid and under the fibula, and in the conse- 

 quent reduction of the calcaneum. This very likely indicates that in the 

 remote and small ancestors of Arsinoltherium the astragalus had a consider- 

 able cuboid facet and that the foot as a whole was not very different from 

 that of Pantolambda. 



In short Arsinoltherium, appears to be related to the Hyracoidea on the 

 one hand and to the Proboscidea on the other, and more remotely to the 

 stem forms of the Amblypoda, i. e., to the Pantolambdidae or Periptychidse. 



VI. The Proboscidea. 



The derivation of the later Proboscidea from forms resembling Pnlceo- 

 mastodon of the Lower Oligocene of the Faydm, Egypt, has been demon- 

 strated by Andrews (1903, 1906) and calls for no comment in this work; 

 but the position of Mceritherium (also from the Faytlm — Upper Eocene and 

 I^ower Oligocene) with reference to the later Proboscidea and Sirenia may be 

 discussed briefly. The following analysis of the characters of Mceritherium 

 is based on Dr. Andrews's excellent figures and descriptions (1906) of the 

 type and referred species. 



