REPTILIA AND AMPHIBIA 201 



and that the development of. the reptilian phylum from such a primitive 

 form was to be most clearly traced in the condition of the temporal open- 

 ings of the skull. This theory assumed that two openings appeared in 

 the temporal region, separated by a narrow bar of bone and the lower one 

 bordered by an equally narrow bar below. Two lines were supposed to 

 have sprung from the primitive form; one^ in which the two openings 

 remained, either actually or potentially, and another in which the lower 

 opening disappeared by the approximation of the two bars. The rhynco- 

 cephalian Sphenodon was regarded as an archaic type, representing the 

 normal condition of the Permo-Triassic reptiles. This idea dominated 

 the minds of all paleontologists interested in the primitive reptiles for 

 many years and culminated in the important paper by Osborn, the "Rep- 

 tilian subclasses Diapsida and Synapsida and the early history of the 

 Diaptosauria.^' 



A second period of activity may be said to have started with the begin- 

 ning of collection by the University of Chicago in Texas, under the direc- 

 tion of Doctor Baur; this work has been continued and the American 

 Museum has added considerably to its material in recent years. The 

 formation of these collections attracted the attention of foreign workers, 

 and in 1895 Broili made, with Sternberg, a trip into Texas, the results 

 of which were carried to Munich. During the last summer von Huene 

 purchased a collection from Sternberg, said to be very fine, which will go 

 •to Tubingen. During the same years came the discoveries of Amalitzky 

 on the North Dwina River in Russia and the beginning of Broom's work 

 in South Africa. Amalitzky's material has not, unfortunately, been 

 worked up ; a few specimens have been cleaned and mounted, but the 

 scientific results from this most promising field are yet to come. 



The results of the second period of activity have been, first, to support 

 and later to question the theory on which most of the work was based. 

 Starting with the assumption that the rhj^ncocephalian type is primitive, 

 and so regarded as a strong guide on the path of research, many workers 

 have been forced to the conclusion that the beautiful and simple concep- 

 tion of the development of the double and single arched reptilian skulls 

 from a common ancestor can no longer be accounted sufficient. Repeated 

 examples have shown, the inadequacy of the theory, and now we can only 

 say that while the morphology of the posterior region of the reptilian 

 skull is still our most useful guide to the relationships of the reptiles, the 

 idea of the development of a primitive two-arched type directly from a 

 ' completely roofed form and then a differentiation into more specialized 

 forms is far from proven. 



