PERMO-CARBONIFEROUS VBRTEBRATES FROM NEW MEXICO. 73 



is between the orbits, due to the projecting, overhanging, and somewhat upwardly 

 curved roof of the orbits, which is convex on its margin and thinned. The parietal 

 region is narrower, but certainly less narrow than in the genotype specimen, and 

 is concave transversely. The parietal foramen is situated rather far back. In 

 front of the orbits the skull rapidly narrows triangularly, nose-like, and is convex 

 in outline, terminating in a thin, median, prominent ridge, which descends con- 

 vexly between the closely approximated nares. The side of the skull is conspicuous 

 for the large, oval, single temporal vacuity, lying immediately back of the orbit, 

 but higher posteriorly, and narrowed in front. It has the thickened lateral margin 

 of the parietal above, the thickened and short postorbital bar in front, the convex 

 border of the parietal arch behind, and a rather slender temporal bar below. The 

 quadrate, covered by a temporal bone, descends far below the arcade posteriorly, 

 leaving a large open space in the articulated skull between the temporal bar and 

 the upper margin of the mandible. If any quadratojugal bone is present in the 

 arcade it must occupy an anomalous position. There is but a single temporal 

 arch and a single temporal opening, in the formation of which it is quite evident 

 the squamosal bone must participate, and into which it seems quite as evident 

 that the quadratojugal does not enter. If this vacuity be, as is urged by Huene 

 and Broom, the lateral temporal vacuity, and not the upper one, the relations 

 of the bones have become sadly mixed. In all probability the temporal bar is 

 formed exclusively by the squamosal and jugal, and it is also not at all improbable 

 that the squamosal reaches toward, if it does not actually join with, the postorbital. 

 By this we do not mean to say that we believe the opening is the upper vacuity, 

 but simply that the attempt at present to differentiate the upper and lateral vacui- 

 ties in the reptilian single-arched skull is premature and unreliable. 



The orbit is subrotund in shape, a little longer in the oblique diameter from 

 above downward anteriorly. Its roof is very prominent, projecting horizontally 

 and a little upward, its border gently convex. Below, it is separated by a short, 

 slender bar from the vacuity above the mandible in the articulated skull. The 

 face in front of the orbit is somewhat cpncave on its upper part. The external 

 narcs are small, round in shape, situated close to the front margin at a considerable 

 distance above the alveolar margin. 



Posteriorly the skull is deeply concave between the parietal projections. On 

 either side there is a concavity above the stout suspensorium, which articulates 

 with the quadrate a little above the level of the temporal arch. Doubtless there is a 

 post-temporal vacuity between the parietal bar and the paroccipital, but it can not 

 be distinguished in the specimen. On the right side, lying back of the downwardly 

 curved parietal process, and reaching inwardly to the middle line, there is a long, 

 rather slender, and curved bone, which seems to be distinct.. If so, it must corre- 

 spond to that figured and described by Case as the " ? epiotic" in the type specimen 

 of the genus. Broom, however, doubted its presence. If the bone be really distinct, 

 and it seems to be, it can hardly be the tabulare, inasmuch as we know of no verte- 

 brate skull in which the tabularia meet in the middle line. Its relations seem to be 

 more those of the postparietal ; but even this interpretation is open to doubt. 



The mandibles, as seen from the side, are very broad posteriorly. The tooth- 

 border is nearly straight. From the rounded and not at all prominent coronoid 

 angle the thin upper border descends obliquely to the articulation for the quadrate. 

 In front, the two sides meet in a very firm symphysis, the front border of which 

 is thinned and convex in outline, descending below the mandibular border back 

 of it, where the mandible is the narrowest, its width not half that oppo.site the 

 coronoid elevation. 



