10 



THE HISTORY OF THE PELYCOSATJKIA, WITH 



rugose, as in the Crocodiles. The crowns of the teeth are striate at the base, and the 

 latter is furrowed vertically. The teeth are not so thickly set as in the smaller species, 

 and the hases of the; crowns are somewhat transverse. 





" Measurements. 



MM. 



Space occupied by ten anterior lower teeth 140 



Depth of lower jaw at symphysis 129' 



Anteroposterior extent of symphysis 25' 



Depth of dentary bone below seventh tooth 80' 



Width of dentary at this point 20' 



"The present species was about tea feet in length, and the largest reptile yet found 

 in this fauna,. The remains are from New Mexico." 



The Ophiacodon mirus is one of the Clepsydropidse, and 0. grandis might be 

 Eryops Cope. 



The families " Nothodontidce" and " Sphenacodontidaz" arc, like the genera, 

 established without diagnosis. 



To this paper Cope 7 replied in The American Naturalist, June, 1878. He says that 

 the four species of reptiles are characterized by Marsh in a very insufficient manner. Be 

 should not regard his article as suitable for notice in The Naturalist but for certain 

 assertions which it contains, and some circumstances connected with its publication. 

 The assertion that "hitherto no Permian vertebrates have been identified in this country, 

 although not uncommon in Europe," he declares the reverse of the; fact, referring to his 

 paper in the Proceedings of the Academy of Natural tScienc.es of Philadelphia for 1.875, 

 pp. 393-424, where some of the leading characters of tins reptiles are pointed on!,; to his 

 papers in the Proceedings of the American Philosophical Society for May, L877, pp. 52- 

 (;:>, where several new species arc described, and in the same journal for November, 1877, 

 in which Other species are added, making the whole number up to twenty-one. lie 

 then continues : "These papers Prof. Marsh has had the opportunity of seeing. Two 

 further notices of the vertebrates of the American Permian appeared on April 22, of 

 the present year (1878), in the May number of this journal, pp. '.)\\) and 327. As the 

 corresponding number of the Am. Journ. AW. and Arts was not issued before May 5 

 (perhaps a, day or tw r o sooner), Prof. Marsh had the opportunity of seeing these 

 also. They include references to seven new genera, for most: of which the characters are 

 clearly pointed out. 



"The features common to the genera of the Permian, described by Marsh, are stated 

 by him to be those characteristic of the order Rhynchocephalia ; as 1 have already shown to 

 be the case with the forms described by me in the earliest as well as later papers of those 



