l8 PERMO-CARBONIFEROUS VERTEBRATES FROM NEW MEXICO. 



but enough has been made out to render certain the points here described. The 

 top was destroyed previous to fossilization, so that it is impossible to give the 

 exact height, but the length and width are correct within a few millimeters. In 

 general the skull resembles that of the members of the family Diadectidee. It 

 may be best compared with the skulls of DiaJccics Iciitus Marsh and Animasaunis 

 carinatus described by us in the American Journal of Science.* It resembles the 

 latter in the width of the posterior end, the narrowed occipital portion, and the 

 fact that the posterior ends of the quadrates and the tips of the squamosal or 

 tabulare bones are about on a line with the occipital condyle. It is also probable 

 that the quadrates had the same backward and inward inclination of the outer 

 faces as in Animasaurus rather than a position nearly parallel to the sides of the 

 skull as in Diadectcs. Other comparisons with the two genera are given in the 

 description of the lower surface. The nares and orbits are similar in form and 

 position to those of the other members of the family ; the pineal foramen can not be 

 made out, owing to the destruction of the upper part of the skull, but certain indi- 

 cations point to the fact that it had the same relatively large size. The outlines 

 of the various bones of the skull can not be determined, owing to the condition 

 of the surface. 



The maxillaries have the usual form, semi-crescentic, on the ventral surface, 

 with the concavity on the outer side. The alveolar surface is broad, accommo- 

 dating the laterally expanded roots of the cheek teeth. Fourteen teeth are indi- 

 cated in the maxillaries and premaxillaries, but as the last of the maxillary teeth 

 is still somewhat expanded laterally, though smaller than the others, it is probable 

 that there was a fifteenth tooth, small, conical, and almost rudimentary, as in 

 Diadectes. This is the usual number in the family. The teeth of the premaxil- 

 laries were elongated and probably had chisel-shaped cutting edges, as in Dia- 

 dectes, but as the incisor teeth of both the upper and lower jaws are badly weathered, 

 only the central portion is preserved and this point may be in doubt. Some of the 

 better-preserved ones seem to suggest a possibly conical form. The roots are very 

 elongate, at least twice as long as the crowns. There is a distinct radial arrange- 

 ment of the dentine around the pulp cavity, very clearly shown in several of the 

 teeth. In none of the cheek teeth is the crown preserved, so that it is impossible 

 to say more than that they were of the type common in the Diadectidag. 



The posterior part of the skull is preserved, in part, on the right side, showing 

 the position and a part of the outer face of the quadrate. This bone was inclined 

 so strongly inward that it looks even more backward than outward, resembling 

 Animasaurus in this respect. The posterior edge of the quadrate is nearly fiat 

 and there is no trace of a quadrate foramen, but this may be due to the condition 

 of the specimen. The prosquamosal reached down to the lower edge of the quad- 

 rate and then extended forward in a nearly horizontal line rather than rising some- 

 what abruptly, as in Diadectes phaseolinus. 



The lower surface of the skull (fig. 8) shows the general form of the palate 

 common in the diadectids, but combines characters of both Diadectes and Ani- 

 masaurus. 



Resemblances to Animasaurus: The anterior end of the palate narrows rapidly, 

 due to the narrow muzzle; the prevomers and the anterior portion of the ptery- 

 goids are shown only by the broken edges, but it is apparent that they must have 

 met in the median line and in all probability formed a high median keel which 

 extended back to a small opening just anterior to the basisphenoid ; the posterior 

 end of the skull is broad across the quadrates, but narrowed in the occipital region; 



* Am. Jnl. Sc, vol. xxxiii, April 1912, p. 339. 



