ABT. 7 



NEW FOSSIL REPTILE GILMORE 



Skull <md lower jav>s. — The skull is entirely missing except for 

 the articular ends of the quadrate bones which remained in 

 an articulated position in relation to the lower jaw. This fact 

 leads to the conclusion that the skull was originally present. The 

 impression left by the removal of the left quadrate shows the articu- 

 lar end to have been bi-lobed. Measured across the quadrates the 

 skull had a greatest width of 48.5 millimeters and from the ante- 

 rior end of the rami to the center of the articular end of the quad- 

 rate it measures 42.5 millimeters, which allows the inference that 

 the length and width of the skull were about equal. 



The impressions left by the mandibles show them, to lie in 

 perfect relation to each other. They are broadly separated behind, 

 and in front turn strongly inward to form a relatively wide, broadly 

 rounded anterior end. The 

 two rami meet in a strong 

 sutural symphysis in which 

 apparently the splenial bones 

 did not participate. The strik- 

 ing characteristics of the man- 

 dible are the great depth of 

 the prearticular portion and 

 the transversely swollen char- 

 acter of the median portion of 

 the jaws which enclosed the 

 large Meckelian orifice. The 

 postarticular processes are 

 relatively short, thin dorso- 

 ventrally but widened trans- 

 versely, especially on the outer 

 border where a thin shelf of bone is developed that becomes gradually 

 wider in an anterior direction, reaching its maximum width slightly 

 forward of the cotylus of the jaw. This feature is clearly shown in 

 Figure 1, a sketch made from a cast of the impression left in the rock. 



Viewed externally the angular is plainly visible as a triangular 

 area interposed between the lower posterior end of the dentary and 

 the lower anterior end of the surangular. The suture separating the 

 angular from the surangular appears to pass backward nearly to the 

 extremity of the jaw. The surangular is relatively short, its anterior 

 extremity being about opposite the middle of the coronoid process. 

 The dentary as usual forms the great part of the ramus and except 

 for the dentigerous border its mold is completely preserved. 

 Although much of the bony matter of the dentaries was present 

 when the specimen was received, nowhere did I find evidence of tooth 

 roots or the presence of alveoli. This would seem to indicate that if 

 teeth were present they were not held in distinct sockets, and this 



Fig. 1. — HypsoGNATHus fbnneri, new species. 

 Type, Cat. No. 11643, U.S.N.M. Natural 

 SIZE. Lower jaws, inferior view. Drawn 



FROM a cast made FROM THE NATURAL MOLD 

 IN THE EOCK. An, ANGULAR ; G, CORONOID ; 

 D, DENTART ; SC. SURANGULAR; 8V- SPLENIAL 



