216 B. L. Mo'odie — Ancestors of the ReptiUa. 



generally, and it is a matter for regret that the geological surveys of 

 most other countries are so far behind that onhehalf of which so much 

 valuable material has been brought together. 



YI. — The Microsauria, Ancestors of the Keptilia. 

 By EoY L. MooDiE, the University of Kansas. 



ONE of the most interesting and most vexed questions in vertebrate 

 palaeontology at the present day is the one which concerns the 

 origin and development of the reptiles. The progress of research has 

 shown the Reptilia to be a wonderfully diverse class, and nearly 

 thirty orders of animals have heen assigned to the group. With all 

 this diversity of structure there is, of course, associated a great 

 diversity of habit. We know all kinds of extinct reptiles from the 

 semi-aquatic to the aquatic, from the flying to the fossorial, from the 

 arboreal to the suhterranean, and many are the varying degrees of 

 structure which are associated with these various hahits of life. 



Recent investigations into the anatomy of the Carboniferous Micro- 

 sauria of North America have led the writer to the conclusion that 

 the Microsauria could easily have been the ancestors of all the later 

 reptiles. The idea that the Microsauria stood ancestrally to the Keptilia 

 is not at all new. Gadow expressed it very clearly when he placed 

 the Microsaurians in the Prosauria. Boulenger has expressed his 

 opinion as to this idea. Baur and others have all agreed that the 

 Microsauria stood ancestrally to some of the reptiles, but no one has, so 

 far as I know, claimed that they might be the ancestors of all the class. 

 It shall be the purpose of this essay to point out briefly the main 

 anatomical features of the Microsauria, and to show in what way 

 they may be homologized with the structures exhibited by the reptiles. 

 A more extended discussion of this matter and a more detailed 

 account of the anatomy of the Microsauria are to be contained in a 

 work to be shortly published on the Carboniferous Amphibia of North 

 America. 



It has been now a little more than half a century since the first 

 Microsaurian was discovered and described, and during that time the 

 additions to our knowledge of these forms have been many. Cope 

 and Dawson have described the Microsaurian fauna of North America, 

 Fritsch has investigated very closely the fauna of Bohemia, Huxley 

 has given us the history of the forms from the British Isles, and 

 Credner has studied the forms from Saxony. Taken as a whole the 

 literature on the group is extensive though not of a monumental 

 character. Excepting for the works of Fritsch and Credner the 

 publications in regard to the Microsauria are widely scattered and 

 difiicult of access, some of the works having been published privately. 



The Microsauria may be defined as reptile-like amphibians with 

 limbs well developed ; usually longicaudate ; skull bones sometimes 

 sculptured with pits and grooves which not infj-equently take the 

 form of lateral line canals called ' slime grooves ' ; skull with horns 

 on the epiotic, supratemporal, or without horns ; branchia never 

 persistent, if present at all ; sclerotic plates present ; vertebrae 



