THE REPTILES OF THE KARROO FORMATION 245 



we only know enough to give merely a general account 

 of the commoner forms found at the different periods. 



The earliest reptile met with occurs in the Upper 

 Dwyka shales, and is called Mesosaurus. It is a small 

 aquatic form about eighteen inches in length with a long 

 narrow pointed head, a very long tail, and feeble limbs. 

 By most European authorities it has been looked upon 

 as a primitive sort of Plesiosaur, but Osborn, Cope, 

 Baur and McGregor, in my opinion, are right in regard- 

 ing it as an early type of Bhynchocephalian in no way 

 nearly related to the Plesiosaurs, and in many points 

 of its structure it resembles Procolophon hereafter men- 

 tioned. Whatever be its affinities, it is agreed by all to 

 be a true reptile, and one which has undergone con- 

 siderable specialisation. As in no part of the world has 

 any reptile ever been discovered in beds earlier than 

 Permian, we seem justified in concluding that the Upper 

 Dwyka shales are not older than Lower Permian. 

 Mesosaurus is of further interest in that an almost 

 identical form occurs in Brazil. 



In the 2,000 to 3,000 feet of strata above the Dwyka 

 which have been called the Ecca series reptilian remains 

 are very rare. So far only two genera have been described, 

 Archceosuchus, a large carnivorous form perhaps allied to 

 Titanosuchus mentioned below and Eccasaurus, a huge 

 rhynchocephaloid reptile by far the largest known. 

 The imperfect remains of at least two other animals are 

 known but have not yet been described. 



Immediately above this comparatively barren series of 

 strata we come to beds in which fossil reptiles are rela- 

 tively plentiful, and sufficient is known to give a fair 



