UNGULATA. 307 



have lived in great numbers in the Arctic Regions, its tusks having been 

 collected from time immemorial on account of the commercial value of the 

 ivory. The extinct species does not appear to have exceeded the modern 

 Indian elephant in size ; and that it was contemporary with man in 

 western Europe is proved not only by the association of its remains with 

 flint implements, but also by a rough sketch of its outward hairy form on 

 a fragment of tusk discovered with other traces of man's handiwork in a 

 cavern in Dordogne, France. 



Sub- Order 5. Ancylopoda. 



Another primitive sub-order of Ungulata which had an 

 extraordinarily wide geographical range in the Miocene and 

 Pliocene periods, but then became extinct, is characterized by 

 the structure of the feet, which exhibit considerable resemblance 

 to those of the extinct ground-sloths of America and the existing 

 pangolins (Manis) of the Old World. When the limbs alone 

 were known, they were indeed referred to the Edentata. The 

 weight of the body in walking seems to have been mainly 

 supported by the outer side of the twisted foot, while the 

 phalanges of each digit curve upwards on highly-developed 

 ginglymoid facettes (see fig. 177) and are terminated each by a 

 cleft, pointed, claw-shaped bone hence the sub-ordinal name 

 ANCYLOPODA or ANCYLODACTYLA. The dentition resembles 

 that of some of the Perissodactyla, when worn even suggesting 

 that of the rhinoceroses, and the anterior teeth are sometimes 

 similarly lost by specialization ; but the dental crowns are 

 always distinctly buno-lophodont before use. The most 

 generalized forms (Homalodontotherium and its allies) occur 

 in the Pyrotherium and Santa Cruz Formations (early Tertiary) 

 of Patagonia; the more specialized genera (Macrotherium, 

 Chalicotherium, and their allies) seem to have ranged throughout 

 the greater part of Europe, Asia, and North America. 



Homalodontotherium (fig. 177). The skull is short and massive, with 

 the narial opening very large and the premaxillary region extending far in 

 advance of the nasals. The orbit communicates with the temporal fossa, 

 but there is a considerable postorbital process of the frontal region. The 



i. 3, c. 1, pm. 4, m. 3 



dentition is complete, the formula bein' r . _ , and the 



6 i. 3, c. 1, pm. 4, m. 3 



teeth form a regular close series, there being neither a diastema nor any 

 enlargement of a canine or incisor. The incisors and canines are small, 



202 



