HISTORICAL REVIEW 3 



ments, the superior of which are not united above the neural canal, and the 

 inferior (intercentrum), divided on the middle line into two segments. 



"Genera: A, Basioccipital bone without condyles: Trimerorhachis Cope; 

 Archegosaurus v. Meyer. A. A, Basioccipital condyles two : Actinodon Gaudry ; 

 Rhachitomus Cope; Eryops Cope. 



"All the above genera have well-developed neural spines except Trime- 

 rorhachis" 



In the same paper was described as new, Ectosteorhachis nitidus. This 

 was classified as "Tribe Crossopterygia; family Rhombodipteridce Traquair; 

 subfamily Saurodipterini Huxley," 



In the "American Naturalist" for 1880 (27), in a comment on Fritsch's 

 "Fauna der Gaskohle und der Kalksteine der Performation Boehms," Cope 

 suggests the formation of a new suborder to contain the genus Cricotus, 

 which he calls Embolomera and defines as follows: "Centra and intercentra 

 subequally developed as vertebral bodies, a single neural arch supported by 

 one of each, forming a double body. Chevron bones supported only by inter- 

 centra. Basioccipital vertebral articulation cup-like, connected with the first 

 vertebra by an undivided discoid intercentrum. 



"Thus the peculiarity of the vertebral column in general is carried into 

 the cephalic articulation, and we have, instead of the complex articulation 

 of the Ganocephala, a single body connecting the occipital condyle and the 

 first vertebra. This body represents, in all probability, the single occipital 

 condyle of the Reptilian skull. This part, as is well known, remains cartilag- 

 inous in the lizard long after the basioccipital is ossified, and is a distinct 

 element. The structure of Cricotus shows that it is a connate intercentrum. 

 We have now removed the last difficulty in the way of the proposition that 

 the Reptilia are derivatives of the Batrachia, viz, the difference in the cranio- 

 vertebral articulation. But the former have not been derived from the 

 Labyrinthodontia as has been suggested, nor from the Ganocephala, but from 

 the Embolomera, as I shall call the new order, or suborder. The order of 

 Reptilia which stands next to it is, of course, the Theromorpha, which presents 

 so many Batrachian characters, including intercentra, as I have for the 

 first time pointed out in the paper above quoted. Besides Cricotus, Fritsch 

 describes a genus from Bohemia under the name Diplovertebron, which I sus- 

 pect to belong to the Embolomera." 



In 1881, in "Bulletin of the U. S. Geological and Geographical Survey 

 of the Territories" (27), Cope described Pantylus cordatus as an amphibian; 

 this he corrected later (30). 



In February of 188 1 Cope published his first catalogue of the vertebra ta 

 of the Permian formation of the United States (28), including: 



Pisces : 



Crossopterygia: _ 



Ectosteorhachis nitidus. 

 Dipnoi: 



Ctenodus fossatus, C. gurleianus, C. periprion, C. porrectus, C. dialo- 

 phus, C. pusillus, Ptyanodus vinslovii, P. paucicristatus. 



