PERMO-CARBONIFEROUS VERTEBRATES FROM NEW MEXICO. IS 



last near the middle of the skull or about 50 mm. in front of the anterior border 

 of the post-temporal vacuity. Two are placed close together in the posterior, one 

 of which is about 2 7 mm. in front of the last tooth in the series. Others are probably 

 present but hidden by the matrix. They are stout, conical teeth, more or less 

 recurved, averaging about 9 mm. at the base, and are about 19 mm. long. Cross- 

 sections show their labj^rinthine structure. 



A single vertebra was found crushed into the palate of the specimen (fig. 6). 

 The centrum is about 25 mm. in diameter and 24 mm. long. The general pro- 

 portions and even the details are very similar to those of Diadectes, with the 

 exception that the hyposphene of Diadectes is not present. From Diasparactiis it 

 apparently differs only in that the latter has a rounded, somewhat longer spine, 

 while the present specimen has a quadrangular section with the diagonals directed 

 antero-laterally and transversely and with somewhat concave sides. It is pos- 

 sible that the vertebra belongs to Nothodon. In short, it is distinctly of the Dia- 

 dectid type. 



To assign to Chenoprosopus a definite systematic position among the Permian 

 vertebrates would be mere speculation at best, till more is known of the skeleton; 

 but one is justified in considering the genus as belonging to the Temnospondyli, 

 in spite of the fact that it has certain rejDtilian aspects. The vertebra found in 

 association with the skull has all the appearances of that of a cotylosaurian, and 

 its size and the amphibian nature of the skull show that the association must 

 have been accidental and that the two could not belong to the same type. The 

 narrow inter-pterygoid opening and the small parasphenoid that must have been 

 present are not unknown among the Temnospondyli. In Cacops, while the inter- 

 pterygoid space is wide, the parasphenoid is exceptionally narrow and in Tre- 

 matops * it is vestigial or even wanting. Then, too, the irregular pitting of the 

 skull, the probable mucus canals, and the large, conical teeth of the palate show 

 its amphibian character. 



Of the American Permian Amphibia, Chenoprosopus resembles Cacops most 

 nearly, perhaps. It differs from Cacops, however, in the smaller nares, not only 

 relatively but absolutely, and in their posterior position in Chenoprosopus; in the 

 much narrower inter-pterygoid space of the latter, and in many minor points. The 

 differences from Trematops are even greater: Trcmatops has an unpaired mucus 

 canal or opening in the anterior part of the rostrum, large anterior nares con- 

 fluent with the antorbital vacuities, and a wide palatal opening, none of which 

 are present in Chenoprosopus. In general appearances the skull very much resem- 

 bles that of the European Archegosaurus.'f Both are comparatively long and 

 tapering and in neither are the nares terminal. Even the arrangement of the 

 cranial elements in the two forms, so far as it has been made out in Chenoprosopus, 

 is similar. The posterior borders of the skulls, however, if the present interpreta- 

 tion of Chenoprosopus be correct, are very different. In Archegosaurus the border 

 is indented by an otic notch, while in Chenoprosopus the posterior border is evi- 

 dently formed by a bar that closes the ear notch, as described above. The wide 

 inter-pterygoid space and the narrow pterygo-palatines of Archegosaurus X are also 

 strikingly different from the condition found in Chenoprosopus. Besides these, 

 there are many minor differences, such as the antero-posteriorly elongate nares 

 and the more or less upward directed orbits of Archegosaurus, which are in con- 

 trast with the laterally directed orbits of Chenoprosopus and the nares that are 



* Williston, Jour. Geol., vol. 17, No. 7, Oct.-Nov. 1909, p. 642. 

 t Jaekel, Zeitschr. d. d. Geol. Gesellsch., vol. 48, 1896. 

 X Credner. 



