THE UPPER TRIASSIC OF WESTERN TEXAS. 17 



The exoccipitals meet the tabulare and the dermsupraoccipitals by strong, finely 

 interdigitating sutures. On the left side there is preserved a portion of a thin process 

 extending inward, which, with its fellow of the opposite side, forms a more or less com- 

 plete shelf dividing the foramen magnum from the space left by the disappearance of 

 the supraoccipital cartilage. The articular surfaces of the condyles face backward and 

 inward. 



On either side of the exoccipitals the posterior rising processes of the pterygoids 

 extend outward to the quadrates. The processes rise toward the upper edge of the 

 squamosal, but do not reach to it in the specimen, ending in a thin and broken edge on 

 both sides. Anterior to this process the posterior face of the anterior rising process 

 may be seen through the great otic vacuity. Between the two rising processes is received 

 the descending process of the squamosal. The otic vacuity lies between the exoccipital, 

 the tabulare, the squamosal, and the posterior rising process of the pterygoid (fig. 1 c). 



The quadrate foramen is relatively larger than in Anaschisma. 1 



The ophisthotic is completely covered by the descending process of the dermsupraoc- 

 cipital and the tabulare. The general similarity between the posterior surfaces of the 

 skulls in the two forms, Anaschisma and BueUneria, is obvious from a comparison of the 

 figures, but it is equally obvious that there is one great difference: in the latter form 

 there are no post-temporal fenestrae; the place of each fenestra is taken by a deep pit 

 with an imperforate bottom. The resemblance is even greater to Metoposaurus diag- 

 nosticus as figured by Watson. 2 It is probable that the part which he has called the 

 epipterygoid (E. Pt. ?) is a part of the descending process of the squamosal. In corre- 

 spondence, Doctor Watson suggests that the space between the two ascending processes 

 of the pterygoid was filled with a "persistent ptery go-quadrate cartilage that is essen- 

 tially an epipterygoid," and suggests that the part described in this paper is an ossifica- 

 tion of that cartilage; but it is clearly a process from the squamosal, as the broken edges 

 in the specimen were clean and fitted perfectly. His figure shows but a slight develop- 

 ment of the posterior rising process of the pterygoid, which in Anaschisma and BueUneria 

 reaches nearly to the upper edge of the squamosal. In the place of a large post-temporal 

 fenestra he shows a small foramen on the dermsupraoccipital-tabulare suture, a condition 

 approaching very closely to that found in BueUneria. 



The upper (inner) surface of the basicranial bones. The condition of the specimen 

 was such that it was possible to remove the matrix completely from the brain-case and 

 the inner side of all the bones, leaving them as clean and intelligible as the outer side 

 (fig. 2 A). 



The anterior portion of the parasphenoid is marked by a deep, flat-bottomed groove 

 with thin, abrupt borders; opposite the anterior edges of the palatine vacuities this 

 groove is nearly equal to the width of the bone (23 mm.), but it contracts gradually and 

 regularly to the rear, and opposite the posterior edges of the palatine vacuities it is 

 not more than 5 mm. in breadth; at the same time the groove becomes much shallower, 

 due to the gradual thickening of the bone. The edges become more rounded and lower 

 as they thicken to the rear, and finally disappear about opposite to the center of the 

 broad posterior portion of the parasphenoid. On either side of the center of ossification 

 and a little to the rear there are openings which extend obliquely outward and backward 

 and are inclosed by a low arch of bone, so that they do not lie within the substance of 

 the parasphenoid, but rather upon its surface, covered by the arch. The outer end of 

 the arch is slightly wider than the inner and terminates in an irregular edge, as if it had 

 been covered with cartilage during life. The length of the arch is 32 mm. The meaning 



1 Branson, E. B., Journal of Geology, vol. xm, No. 7, fig. 3, 1905. 



2 Watson, D. M. S., Transactions Royal Society of London, vol. 209, Series B, fig. 10, 1919. 



