254 GEOLOGY OF CAPE COLONY 



Beaufort series, there is an extensive and fairly well- 

 known fauna characterised mainly by the relative 

 abundance of Cynodont reptiles. The Cynodonts for- 

 merly were not clearly distinguished from the Theroce- 

 phalians, the two groups being both included in the order 

 Theriodontia. There is little doubt that the Cynodonts 

 are descended from Therocephalian ancestors, and one 

 genus (Bauria) is known which to some extent forms a 

 connecting link, but the two groups can be readily dis- 

 tinguished. The Therocephalians, as has been pointed 

 out, have an open palate and a single occipital condyle, 

 and are exclusively confined to Permian beds. The 

 Cynodonts, on the other hand, are much more mammal- 

 like. The palate is formed as in mammals by secondary 

 plates from the maxillary and palatine bones and the oc- 

 ciput had two condyles. The quadrate is very small, 

 and the articular, angular and surangular bones of the 

 lower jaw also small. The dentary forms almost the 

 whole of the jaw and almost articulates with the small 

 quadrate. The molar teeth are in some forms cusped 

 like the middle premolars of the dog ; in other types 

 they have flattened tops with usually two large cusps 

 and numerous small ones. The general arrangement 

 of the bones of the head is strikingly like that of the 

 lower mammals, such as the polyprotodont marsupials. 

 The shoulder girdle is not unlike that of the Anomodonts, 

 but there is apparently no cleithrum. The carpus has 

 still two centralia, but the radial one is very minute. 

 The pelvis resembles the mammalian type and differs 

 from that of all other reptiles in having an expanded 

 anteriorly directed ilium, and a large obturator foramen . 



