32 



\1W REPTILES AND STEGOCKl'HALIAXS I'HiiM 



upper posterior portion of the temporal opening, which carries slight rugosities and 

 may indicate the location of the suture between the epiotic and prootic. The epiotic, 

 if ever a distinct element, is fused with the opisthotic in the specimen. The edge of 

 the anterior half of the posterior ridge is elevated and behind it is a groove which is 

 continuous with the groove on the side of the basisphenoid. On the inner end of the 

 opisthotic there are two openings — an upper, the otic opening, and a lower, the jugular 

 foramen. 



The position and form of the quadrate is one of the puzzling features of the skull. 

 Between the distal end of the opisthotic and the quadratojugal is a deep pit, partly 

 cut off in front by a ridge which runs from the inner side of the posterior end of the 

 jugal-quadratojugal bar to the opisthotic. The quadrate apparently occupies the bottom 

 of this pit, and the articulation with the lower jaw must have been formed by the con- 

 cave surface, but no distinct articular surface is visible. If this interpretation is correct, 

 the quadrate fills a small triangular area between the distal end of the opisthotic and 

 quadratojugal, forms the bottom of the pit described, and runs forward for a short 

 distance on the inner side of the opisthotic and for an uncertain, but not great, distance 

 on the cranial wall. At best it must have been a relatively small and inconspicuous 

 bone. 



opo 



pt.f? 





mx 



_J Fie. 8. — Restoration of skull of Deematosuckut. 



After ideas suggested by Watson and von 

 Huene. Dotted portions are supposed 



to have ljeen lost. 

 opo., distal end of the Opisthotic. Other lettering 

 as usual. 



In comparing the skull with that of other forms, it is at once apparent that its 

 closest relations lie with the Parasuchia, but the differences are so fundamental that 

 it can not be placed in that order. The most notable differences are the single temporal 

 foramen, the lateral and anterior position of the nares, and the extremely reduced 

 condition of the quadrate bone. The last is the most fundamental. The lateral 

 position of the nares is found in the Pseudosuchians and in some primitive Parasuchians. 

 The development of the upper temporal opening is so irregular, though constantly 

 present, in the two groups that its complete disappearance would be no great step in 

 specialization; or its absence might be regarded as of primitive character, since it has 

 become apparent that the presence of two temporal openings and arches is not the 

 primitive condition of the Reptilia. The great reduction of the quadrate is a character 

 which does not appear outside of the South African phyla, which can hardly be com- 

 pared with this form, for in those phyla the reduction of the quadrate is accomplished 

 in an entirely different manner. In most of the Reptilia the quadrate has a greater or 

 less vertical extent upon the side of the skull and is not always closely associated with 

 the bones of the brain-case, its main associations being with the bones of the suspensorial 

 region. Only in the Crocodilia (sens, lot.) does the quadrate extend far inward, having 

 relations with the wall of the brain-case and the bones of the otic region. It is not 

 possible in the specimen to determine whether the quadrate has the relations figured 

 by Huene for the I'arasuchia (Geolog. u. Paleont. Abhdlg., vol. x, N. F., Hft. 1, p. 31, 

 fig. 20), permitting the squamosal, epiotic, and prootic to appear in the posterior lateral 



