588 ZOOLOGY SECT. 



sometimes tritubercular, like those of many of the Carnivo*a ; the 

 incisors and canines also sometimes resemble those of the Carnivora. 

 The humerus differs from that of the other Ungulata, and resembles 

 that of the Carnivora in the presence of a foramen over the inner 

 condyle. The arrangement of the carpals corresponds with what 

 is observable in the Hyracoidea, and also, as in the latter group, 

 the femur has a third trochanter. The limbs are usually penta- 

 dactyle, with pointed ungual phalanges. The astragalus has, as 

 in the Carnivora, a uniformly rounded distal articular surface. 

 The fibula does not articulate with either the astragalus or the 

 calcaneum. 



Another extinct primitive sub-order of the Ungulata is the 

 Amblypoda, the members of which have been found, like the 

 Condylarthra, in the Eocene of North America and of Europe. 

 These resemble the Condylarthra and Hyracoidea in the scaphoid 

 being opposite the trapezoid ; both magnum and unciform articulate 

 with the lunar. The fibula articulates with the calcaneum ; the 

 cuboid articulates with both the astragalus and the calcaneum ; 

 the feet are short, pentadactyle, and plantigrade. Canines are 

 present in both upper and lower jaw ; the pre-molars and molars 

 are short and lophodont in type. Dinocems and Tinoceras are 

 characterised by the process of remarkable bony prominences on 

 the upper surface of the skull. In the Tertiary deposits of 

 Patagonia and Bolivia have been found the remains of another 

 group of extinct Ungulates of low organisation, the Litopterna. 

 These had the distal segments of the limbs elongated and con- 

 structed on the perissodactyle type, the number of the digits 

 varying from five to one, the third being always the largest. The 

 carpal and tarsal bones do not interlock as in the existing Ungulata 

 vera. There is no foramen above the inner condyle, and clavicles 

 are absent. A third trochanter is present. The brain-case is very 

 much smaller than in the existing Ungulata vera. The dentition 

 is complete or nearly so ; the pre-molars and molars short and 

 provided with roots. 



The Ancylopoda are another group of primitive extinct Ungulates. 

 The remains of some of these have only been found in the Pata- 

 gonian Tertiary deposits, but others had a wide range both in the 

 Old and New Worlds. They all differ from other groups of 

 Ungulates in the form of the limbs : the weight of the body appears 

 to have been borne on the outer edge of the manus and pes, and the 

 digits were evidently provided, not with true hoofs, but with pointed 

 claws. The teeth resemble those of the Perissodactyla. 



The Typotheria and Toxodontia are two groups of extinct 

 Ungulata the representatives of which have only so far been found 

 in the South American Tertiary formations. The former differ 

 from ordinary Ungulates in the possession of a clavicle and the 

 presence of a foramen above the inner condyle of the humerus. 



