252 GEOLOGY OF CAPE COLONY 



This is a small form probably not much larger than a 

 guinea-pig with a broad box-like head. It is very 

 imperfectly known. With it apparently are a number 

 of Therocephalians of a somewhat higher type than 

 those met with in the lower beds. One genus, Scalo- 

 posaurus was probably as small as a rat. The other 

 known genera are more comparable in size to dogs of 

 various breeds. 



Above this last formation occurs a large series of beds 

 characterised by the remarkable scarcity of land forms 

 and the frequency of an aquatic Anomodont called 

 Lystrosaurus ( = Ptychognathus, Ow.). This may be looked 

 upon as a Dicynodont reptile which has become modi- 

 fied to suit a life mainly aquatic. The skull is so bent 

 and developed that the large eyes are situated near the 

 top of the head and the nostrils are also high up. This 

 was to enable the animal when lying floating to breathe 

 and to look about without moving or exposing much of 

 its head or body. Some such modification is met with 

 in almost all mammals or reptiles that became aquatic 

 in habit. The limbs are short and the joints imperfectly 

 ossified. Though Lystrosaurus probably spent most of 

 its time in the water, it no doubt frequently came on to 

 the land, on which it waddled perhaps as satisfactorily 

 as a seal. 



Succeeding the beds with Lystrosaurus are a series in 

 which so far as is known only land forms occur. Of 

 these the most noteworthy is Procolophon. This is a 

 lizard-like reptile about eighteen inches in length with 

 a broad triangular head. There is a little difference of 

 opinion as to its affinities, but it is agreed by all to be 



