THE UPPER TRIASSIC OF WESTERN TEXAS. 15 



they do not lie upon definite bones so certainly as to be entirely dependable criteria for 

 the determination of the homology of the bones with those of the fish skull. This is 

 particularly noticeable in the posterior part of the course of the temporal canals and their 

 relation to the tabulare. In comparison with the course of the canals in Metoposaurus, 

 as given by Moodie, the differences are quite similar to those noted in comparison with 

 AnascMsma. 



The lower surface of the skull. In this region the skull shows very decided differences 

 from AnascMsma. Branson states that in Anaschisma each palatine bone bears only a 

 single tooth, and this has been confirmed by a reexamination of the skull by Mr. Paul 

 Miller. It is also stated by Branson that there are four teeth on the anterior edge of 

 each prevomer (vomer), but no mention is made of a row of teeth on the inner edges of 

 the narial openings. It may be that these rows are obscured by the condition of the 

 specimen in the University of Chicago. The vomers are shown in Anaschisma as ter- 

 minating behind in long points which extend down the side of the parasphenoid. The 

 transverse bones are shown as large elements. The character of the articulation of the 

 parasphenoids with the exoccipitals is very different in the two forms. Mr. Miller has 

 reexamined this region and assures the author that there is a median suture as shown by 

 Branson and interpreted by him as the meeting of the exoccipitals and that there is a 

 large union of the parasphenoid with the pterygoids. The parasphenoid-exoccipital 

 suture is reported as uncertain, but it could not be far from the position given it by Bran- 

 son. The long median suture shown by Branson is one of the most interesting points 

 about the skull of Anaschisma; if it is formed by the meeting of the exoccipitals for any 

 considerable distance (the posterior portion of the skull is restored in plaster), it is 

 unique among the Stegocephalia, for in no other form is there a meeting of the posterior 

 ends of the exoccipitals for any considerable distance, if at all. 



In Buettneria the premaxillaries are short, with large openings through which a 

 small part of the external nares can be seen from below. At the point of the union of 

 the premaxillaries with the vomers there is a small irregular depression in the median 

 line which may be significant or may be due only to imperfect ossification at the meeting- 

 point of the four bones. There are 13-13 teeth on the premaxillaries. 



The vomers are large flat plates; the anterior outer part forms the floor of the external 

 narial opening when seen directly from above. The anterior outer corners support large 

 tusks on each side; these were placed in pairs in which the tusks were alternately func- 

 tional; on the left side the anterior one was in use and on the right the posterior one 

 at the time of the death of the animal. On the anterior edges of the bones between 

 the tusks there is a nearly straight row of fairly large teeth. There are 5 teeth on each 

 side, the outer one smaller than the others. On the inner edge of the internal narial 

 openings there is a row of small teeth, 18 to 20 in number; the rows terminate posteriorly 

 at the palatine-vomer suture; anteriorly they are separated from the tusks by a short 

 vacant space. Within the inner edge of the internal nares there is a small cluster of 

 very small teeth; these point toward the center of the opening in the specimen. 



The palatines are separated from the maxillaries by a long, straight suture, and from 

 the premaxillaries and the vomers by clearly defined sutures, as shown in figure 1 B, 

 and plate 1, fig. B. External to the posterior half of the internal nares there are large 

 paired tusks; as in the vomerine tusks, the functional teeth of the pairs are alternate in 

 position. Just posterior to the internal nares is a small cluster of irregular teeth. 5 to 6 

 in number. The long row of teeth on the outer edge begins just posterior to the tusks and 

 is continuous to the extreme posterior end. The teeth are very closely set and diminish 

 to exceedingly small size towards the rear; many of the teeth are represented by empty 

 spaces and were apparently not functional at the time of death. There are 36 to 38 

 teeth on each side. The palatine joins the pterygoid by an oblique suture. 



