1905.] PRIMITIVE REPTILE PROCOLOPHOISr. 217 



1904) that Ifesosaurics is not a Plesiosaur, mainly because the 

 Plesiosaurs seem to have sprung from a land ancestor which had 

 lost its precoracoid and had the Sjyhenodon type of pelvis, whereas 

 Mesosaurus has evidently sprung fi-om a land-form which retained 

 its j)recoracoid and had a plate-like pelvis. As Mesosaii,7'us lived 

 in Lower Permian times, it is evident that true reptiles of the 

 Diapsidan phylum existed at a very early period. Only a few 

 of them have so far been discovered, and at present we can only 

 imagine what the structure of many of the early forms was like 

 from what we know of the specialised descendants. Procolofhon 

 I believe to be a slightly modified descendant of one of the early 

 Permian Diapsidan types such as that which gave rise to Meso- 

 saurus. The beds in which Procoloj^hon occurs are either Middle 

 or Lower Triassic, but there is reason to believe that 8ai(,rosternon 

 is an alHed form, and this occurs in beds which are most probably 

 Upper Permian. So that the Procolophonia probably originated 

 in Permian times. The beds in which Televpeton occurs in 

 Scotland are considerably younger than the Procolophon-h^^^ of 

 S. Africa, being probably Upper Triassic, Rhjetic, or possibly 

 even Liassic. 



I hope shortly to give a complete account of the structure of 

 Procoloplion, and it is to be desired that one of the American 

 workers will do the same for one or other of the Ootylosaui'ians. 

 We shall then be in a position to realise more clearly what are tbe 

 relationships of these primitive types to each other. 



More important Literature. 



1. Owen, R. — Catalogue of the Fossil Reptiles of S. Africa. 



London, 1876. 



2. Seeley, H. G. — " On new Species of ProcolopJion, (fee." 



Q.J.G.S. vol. xxxiv. 1878. 



3. Seeley, H. G. — " On Pareiasauriis hombidens (Owen), &c." 



Proc. Roy. Soc. 1888. 



4. Cope, E. D. — " On the Homologies of some of the Cranial 



Bones of the Reptiha, &c." P. A. A. A. S. xix. p. 13. 



5. ZiTTEL, K. V. — Handbuch der Palseontologie. Vol. iii. 



6. Lydekker, R. — Catalogue of the Fossil Reptilia and Amphibia 



in the British Museum. Pt. iv. London, 1890. 



7. Seeley, H. G. — " Further Observations on PareiasauvusT 



Phil. Trans. 1892. 



8. Broom, R. — " On the Remains of Procolophon in the Albany 



Museum." Rec. Alb. Mus. vol. i. no. 1 (1903). 



9. OsBORK, H. F. — " The Reptilian Subclasses Diapsida and 



Synapsida, &c." Mem. Amer. Mus. Is^at. Hist. 1903. 



10. BouLENGER, G. A. — " On the Characters and Affinities of the 



Triassic Reptile Telerpeton elginense." P. Z. S. 1904, vol. i. 

 pt. 2. 



11. Woodward, A. S. — Outlines of Vertebrate Palaeontology. 



1898. 



