DISSOROPHUS COPE 533 



fication. The remarkable characters of Trematops also justify the 

 creaJ;ion of a family for its reception, with possibly Acheloma as an 

 alhed genus. Of the other American genera of temnospondyles, 

 Eryops has long been considered of family rank, as also Trimero- 

 rhachis. None of these genera, so far as my knowledge goes, possessed 

 either dermal or ventral armature, other than the carapacial develop- 

 ment of the Dissorophidae and Zatrachydidae. Dermal plates have 

 been accredited to Trimerorhachis, but I believe wrongly, since several 

 specimens in the Chicago collection although including almost all 

 parts of the skeleton give not the slightest indication of such. Nor 

 were there any dermal plates, ventral or dorsal, in either Tremaiops 

 or Eryops, and I am convinced that none will be found in Zatrachys, 

 when better known. That there were amphibians in the American 

 Permian with isolated dermal scutes is, I believe, certain from the 

 evidence furnished by the Orlando bone bed, though perhaps they 

 were all small animals. Thevenin has discovered dermal ossifications 

 in Euchirosaurus, which he believes to be identical with Actinodon, 

 and, furthermore, from his figure and descriptions of the ribs in that 

 genus, it is quite certain that its relationship with Eryops is not nearly 

 so close as has been thought, and as Thevenin believes. Similarly 

 expanded ribs are characteristic of Aspidosaurus, apparently. 

 Furthermore, we have no evidence so far, among the American forms, 

 of a long tail, unless it be in Trimerorhachis, which differs so much in 

 many ways from the other temnospondyles that it may well be it had 

 also a long tail. Thevenin gives the number of presacral vertebrae 

 in Euchirosaurus as twenty-two or twenty-three, I have determined 

 the same numbers in Trematops, while in Cacops the number is posi- 

 tively fixed at twenty-one. Branson^ gives the number for Eryops as 

 twenty-five or twenty-six, though he found in no specimen more than 

 twenty-four in a continuous series. Perhaps there is some variation 

 in the various genera, but evidently the number never greatly exceeded 

 twenty-two. Branson speaks of a small isolated arch in the atlas; if 

 he be correct, the atlas differs materially from those of Trematops, 

 Cacops, and Dissorophus. But I believe it will be found that the 

 Eryops atlas was of like structure, that is, with co-ossified neuro- and 

 hypocentra, with the sides of two neurocentra separated above. Bran- 



^ Journal of Geology, VIII, 607,. 



