No. 586] THE COAL MEASURES AMPHIBIA 



039 



The following elements of the stegoeephalan cranium are homologous 

 with the same elements in (the erossopterygian) fishes: premaxillae, 



frontal*. The epioties and supraoecipitals of the Stegocephala are 

 homologous with the supratemporal elements of fishes. The quadrato- 

 jugal is homologous with the subopercular of fishes. The supratem- 

 poral is homologous with the preopereulum (8). 



Wilder has commented on the close relationship of 

 these two groups and even goes so far as to say: "that 

 terrestrial vertebrates were originally derived from a 

 single form, perhaps a single species" (i. e., of the Cros- 

 sopterygia) (9). It will be interesting in this connection 

 to give a brief resume of the geological history of the two 

 groups of vertebrates. The history of the Amphibia is 

 briefly this : 



Devonian: Thinopus antiquus Marsh, footprint from 

 Pennsylvania. 



Mississippian : Footprints from eastern North America. 



Pennsylvanian : Five orders of Amphibians represented 

 by hundreds of more or less complete skeletons from 

 Europe and North America. 



Permian : Four orders of Amphibia, known from an abun- 

 dance of material from Europe, Africa, Asia, and 

 North America. 



Triassic : Two orders of Amphibia, the species of which 

 may be compared very favorably with modern spe- 

 cies ; North America and Europe. 



Comanchean : None known in North America. 



Cretaceous: Caudata known from imperfect fragments, 

 North America. 



Eocene to Recent: Frogs and salamanders as in modern 

 times. 



Recent: Salientia, Caudata, Gymnophiona. 



The geological history of the Crossopterygia is briefly 

 summarized by Huxley 1 in the following: 



The group of Crossopterygidae as thus established appears to me to 

 have many remarkable and interesting zoological and paleontological 

 relations. Of the six families which compose it, four are not only 

 Paleozoic, but are, some exclusively and all chiefly, confined to rocks of 



i Scientific Memoirs, II, p. 445. 



