AMPHIBIA : ERYOPS n 



one species, though this cannot be positively decided without 

 further study and more material. The species is rather small for 

 an Eryops, though it must unfortunately bear the name grandis, 

 a name given to it under the misapprehension that it was a reptile. 

 Evidently Marsh had not seen the description of Eryops megacepha- 

 lus Cope at the time of the publication of his paper; otherwise 

 he would not have fallen into the error of calling his species 

 a reptile. The description of E. megacephalus is said to have 

 been published the preceding November, but of this there is 

 some doubt. That there were " various parts of the skeleton" 

 among the material studied by Marsh must, of course, have been 

 assumed, since he could not have recognized them without at the 

 same time recognizing their generic distinction from Ophiacodon 

 minis. 



A considerable number of species of Eryops have been described 

 from Texas and New Mexico, but we are almost entirely ignorant 

 yet of the real distinguishing specific characters, and their differen- 

 tiation has been, for the most part, assumed. 



In a recent paper I stated that Eryops had no uncinate processes 

 on the ribs; in this I was in error. The specimen of Eryops 

 mounted in the American Museum an excellent one has not 

 only well-developed uncinate processes, but ventral ossifications 

 as well, characters which associate the genus much more closely 

 with the European Euchirosaurus than I had supposed. In the 

 same publication I also spoke of a specimen with dilated spines 

 which I was inclined to refer to the basal caudal region of Eryops. 

 The American Museum specimen likewise shows that there were 

 no dilated spines anywhere in the vertebral series in Eryops, from 

 which it would seem certain that there is another genus of Ery- 

 opidae in Texas, possibly Anisodexis, .even more closely allied to 

 Euchirosaurus. Because of this close relation between Eryops 

 and Euchirosaurus with dilated spines, and also because of the 

 possession of the uncinate processes on the ribs, I am disposed 

 to place the genus Aspidosaurus in the same family, all of them, 

 as also various species referred in the past provisionally to Zatrachys, 

 presenting these characters and the open otic notch behind. 



