708 ELEPHANTS xxix. 3- 



and Oligocene ungulates. The gait is plantigrade, with four anterior 

 and three posterior digits, carrying somewhat hoof-like nails, except 

 for a sharp bifid claw, used for toilet purposes, on the inner hind toe 

 (Fig. 472). There is a single pair of continually growing incisors in the 

 upper and two in the comb-like lower jaw. There is a diastema and 

 seven grinding molariform teeth of bunoselenodont type, with trans- 

 verse ridges, recalling those of brontotheres. The lower jaw is very 

 deep, for the attachment of the masseter muscle, and, as is usual in 



Fig. 472. Skeleton of Procavia. 



ungulates, the post-orbital bar is nearly or quite complete. There is a 

 serial carpus with a centrale, an unusually primitive feature for an 

 ungulate. The intestine provides chambers for digestion by symbionts. 

 In the large median caecum are found enormous ciliates (Pycnothrtx), 

 up to 5 mm long, and a fauna of cellulose-splitting bacteria. Beyond 

 this lies a further pair of caeca. 



The brain is of macrosmatic type. As in the elephants, the testis 

 fails to descend and remains close to the kidney, there being no sign 

 of a scrotum or inguinal canal. The uterus is paired, and the placenta 

 at first covered with foetal villi, later restricted to a zonary arrange- 

 ment, superficially similar to that of carnivores, but with a haemo- 

 chorial structure with a resemblance to that of Tarsius. There is a 

 single pair of pectoral mammae. 



Various species of Procavia are common throughout Africa (not 

 Madagascar), Arabia, Palestine, and Syria, living in desert regions in 

 colonies under rocks. They do not dig burrows, the feet being flat- 

 tened and well suited for moving over smooth rock surfaces. The 



