261 



* 



On the Classification of the Reptilia. 



By Edwin S. Goodrich, F.R.S., Fellow of Merton College, Oxford 



(Received May 11, 1916.) 



It is gradually becoming recognised that the class Reptilia is not a 

 monophyletic group of diverging forms sprung from a common stem, like 

 the class Aves or the class Mammalia ; but is an assemblage containing, on 

 the one hand, the ancestors of the Mammalia, and, on the other hand, the 

 ancestors of the Birds, together with the early Amphibian-like Amniotes, 

 which became adapted to a terrestrial mode of life. In fact, the Reptilia 

 represent not a class but a grade of structure. This group includes a main 

 stem leading from the Stegocephalian type to a central point of divergence 

 of two main branches, one giving rise to the Birds, the other to the 

 Mammals (as shown in the diagram, fig. 1). In addition, there are, of 



Fig. 1. 



course, many abortive side twigs. Some day, no doubt, when the exact 

 relationship of the various living and extinct reptiles has been more 

 accurately determined, it will be necessary to split up the artificial group 

 Reptilia, assigning some to the Mammalia and some to the Aves ; but for the 



