THE UPPER TRIASSIC OF WESTERN TEXAS. 



59 



face of the skull the relation of the transverse to the pterygoid is very different in the 

 two forms. In M. planirostris and pleiningeri the transverse lies external to the process 

 of the pterygoid and articulates with it laterally instead of underlying it; the outer 

 corner of the dependent process is formed entirely by the transverse; the palatine foramen 

 is small, but lies anterior to the middle of the transverse; the quadrate process of the 

 pterygoid is shorter and articulates with an elongate process of the quadrate; the suture, 

 as figured by McGregor, lies, at least on the lower face, near to the basisphenoid process of 

 the pterygoid; there is but a small interpterygoid space and the parasphenoid process is 

 short or in large part covered by the pterygoids; the internal nares are directly beneath 

 the external nares; the inner edges of the palatines are elevated, but do not show the 

 rugosity which appears on these bones in Promystriosuchus. It is apparently this ele- 

 vated edge of the palatines which Huene 1 refers to as the median edge of the pterygoids. 



pf JL 



I •'!>;. 24. — Phytosaunis (Machcerojirosopus) , after Mehl. 



A. Lateral view of skull. 



B. Upper view of skull. 



' '. Posterior new of skull. 



1). 1'oslcrior view of skull of Miistriosuchux, after McGregor. 

 E. Posterior view of skull of I'hi/tosnurwi kappfi. 

 Lettering M usual. 



Comparison with Rhytidiodon. 8 



Most of the material representing this genus was recovered from the Triassic 

 coal-beds of Egypt, Chatham County, North Carolina. Most of the skulls, as reported 

 by McGregor, tire in a very fragmentary condition; a single skull, lacking the anterior 

 end. permits of some comparison. The antorbital opening extends beyond the anterior 

 edge of the external nares; the orbits have a considerable lateral presentation; the 

 parieto-squamosa] bar is depressed; the squamosal region extends well posterior to the 

 occipital condyle; the palatine vacuities arc at the extreme anterior end of the transverse. 



' Huene, 1". v., loo. tit., p. 17. * McGregor, J. H., loc. cit, p. 58. 



