MAMMALIA. 567 
be traced by a continuous series of forms. Periptychus is 
also regarded by many as being at or near the point of 
origin of modern Artiodacty/a. On the other hand, many 
of the Condylarthra show structural resemblances to the 
Hyracoidea especially in the serial carpal bones. Thus 
they form the point of convergence for at least three of the 
four modern sub-orders. They are all rather small animals 
and are found in the Lower Pliocene of Europe and North 
America. \ 
Fig. 387.—THE Dasse (Ayrax capensis). 
(From Flower and LyppDEkeEr.) 
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SUB-ORDER II.—HYRACOIDEA. 
This is a small modern sub-order, comprising a few furry 
rodent-like animals of the genus Ayrax (Procavia and 
Dendrohyrax) and a third extinct genus, Phohyrax. The 
first pair of upper incisors grow from persistent pulps as in 
rodents, and the others are absent (the second pair being 
rudimentary in the young). There are two pairs of incisors 
in the lower jaw. Canines’ are absent, but the molars and 
premolars are complete, all tending to resemble each other. 
The enamel of the molars is folded, the pattern most nearly 
resembling that found in the rhinoceros. 
