566 CHORDATA. 
progressive changes, be noticed the gradual assumption of a 
digitigrade method of walking from the primitive planti- 
grade. Special allusion has been made to most of these 
points in dealing with the horse and ox. The intestine is 
always long, the uterus is usually of the bicornuate type and 
the placenta is non-deciduate and either zonary, diffuse, or 
cotyledonary. 
SUB-ORDER I.—CONDYLARTHRA. 
The members of this sub-order are all extinct and they 
represent the very lowest point of the ungulate stock. They 
have the typical eutherian dentition of 344% and the molars 
Fig. 386.—LATERAL VIEW OF SKULL OF DAMAN 
(Ayrax syriacus). 
Note the rodent-like incisors, absence of canines and long row of seven 
grinding premolars and molars. The malar bone is seen to extend 
back to the glencid cavity. 
were of simple brachydont structure. The limbs were planti- 
grade, with five toes, and the carpal and tarsal bones were 
serial. The fibula and ulna were not reduced, though the 
latter had already lost its connection with the calcaneum. 
The femur had a third trochanter, as in modern Perissodactyla. 
The tail was long. The humerus, contrary to that of other 
Ungulata, had an entepicondylar foramen, resembling that 
of Carnivora. The toes appear to have borne blunt claws 
rather than hoofs. Phenacodus is the best known genus 
to which the modern horse, and hence Perissodactyla, can 
