SYSTEMATIC REVISION 73 



anterior articular extremity. In this way the vertebra combines the me- 

 chanical relations of the biconcave with the opisthocoelian structures. The 

 neural arches are narrow, and directed backwards; their bases are firmly 

 coossified with the centrum, no zygapophyses appear on the portion of the 

 neurapophyses preserved, and it is probable that they were weak if existing. 

 On the inferior surface of the centrum two shallow pits occupy considerable 

 space, and indicate the existence of large, free, chevron bones. No trans- 

 verse processes. In one vertebra the floor of the neural arch is deeply exca- 

 vated; in the other it is plane and marked with a median groove." 



The remainder of the description is given up to the limb bones, which 

 were conjectured by Cope to belong to Cricotus; the association is more than 

 doubtful and it seems of no value to continue their description with that of 

 the type vertebrae. In the description. Cope had the intercentrum (which 

 he took for a centrum) inverted, and allowance must be made for this. He 

 recognized this error himself, and in his drawings of a slightly later date 

 (which were never published) he corrected it. 



In 1884 Cope added considerably to his original description: 



"Accession of additional material enables me to add several points to 

 the knowledge of the osteology of this genus, and to distinguish satisfactorily 

 three species. I have much pleasure in obtaining these additional facts, 

 since everything relating to this curious genus is of interest. 



"In the first place, the neural arches are not coossified to the centra, 

 but are readily separated from them. Their basis of attachment forms, on 

 each side of the median neural canal, an oblique triangular surface looking 

 forwards and upwards, with the apex above and behind. The ease with 

 which the neural arches separate accounts for the rarity of their occurrence 

 on separate centra. They support the diapophyses at their lower border. 

 Second, that the sacrum consists only of a centrum and an intercentrum, 

 both of which take part in furnishing a concave facet for the attachment 

 of the pelvis. Tnird, some of the ribs are two-headed, and their capitular 

 articulation is with the posterior edge of the intercentrum. Fourth, there 

 is a hyposphenal articulation, as in the genera of Jurassic Saurians, Camara- 

 saurus, Amphicoelias, etc., and in the Permian genus Empedias, among the 

 Theromorpha. The hypantrum has, however, this peculiarity: that its sides 

 are produced forwards into a process on each side below the prezygapophyses, 

 each of which is subconical in form, but with the interior face excavated to 

 receive the hyposphen, so that the section of the process is crescentic. These 

 processes I have never previously observed. I call them hypantrapophyses. 

 I find them in the Cricotus hypantricus. The neural arches of the other 

 species are either lost or in such close juxtaposition that I can not see them." 



In the "American Naturalist," in his account of the "Batrachia of the 

 Permian Period of North America," Cope gives the following account of the 

 genus: 



"In this genus the teeth are rather large, and are of subequal size in 

 the external rows. The tail is long, and was apparently useful as a natatory 

 organ. The terminal phalanges are obtuse as in salamanders, and without 

 claws. The pelvis has the character of that of the Eryopidse, but is less 

 massive anteriorly. The lower jaw has no posterior projecting angle. There 

 are mucous grooves on the skull. The abdominal scales are oblong and in 

 close contact with each other." 



Revised description: This is contained in that of the family. 



