152 



REVISION OF THE PELYCOSAURIA. 



teeth in each premaxillary which are badly worn, but were apparently furnished with 

 a strong terminal cutting edge, something like that of the modern rodents or the 

 ancient Placodus. The teeth projected slightly forward from the edge of the jaw. 

 The posterior edge of the bone forms the anterior edge of the nares. 



The maxillary is a broad plate extending upward somewhat obliquely and unit- 

 ing with the nasals above and the premaxillary anteriorly. The anterior edge forms 

 the posterior edge of the nares and the posterior end lies below the middle of the eye- 

 socket. There are fourteen teeth in the bone ; the anterior five are thin triangular 

 plates that had originally well-developed anterior and posterior cutting edges, but 



these have been largely destroyed by decay. 

 The posterior nine teeth are conical. All 

 the teeth are in sockets and rest against 

 the outer edge of the bone which descends 

 lower than the inner. 



The nasals are broad, flat plates, em- 

 bracing the premaxillaries anteriorly and 

 extending between the frontals posteriorly. 

 The /ronlals are very broad and flat ; 

 they meet the parietals posteriorly in a 

 wide suture and form the major portion 

 of the upper edge of the orbit. 



The prefrontals form the upper an- 

 terior corner of the orbit. 



The lachrymals are short bones, 

 rounded anteriorly and extending back 

 on the floor of the orbit to the anterior 

 third of the lower edge. 



The parietals are flat anteriorly with 

 a good-sized parietal foramen, but the 

 posterior portion is somewhat convex. 



Fig. 66.-Diagram of the upper surface o( the skull of £<^apAo- /pj^^ hontS of the tWO sideS meet in a 



sauruspogoniaa. , , ., n .l sHght depression, so that the crown of 



rig. o7. — Diagram or the lower surlace ot the same. Both ° '■ ' 



the skull is arched antero-postenorly and 

 depressed in the mid-line. The outer 

 edge is concave and forms the upper 

 border of the superior temporal vacuitj'. 

 From the posterior outer corner a process 



Paqf.\ 



X 



fmx. premaxillary; mx. maxillary; «a. nasal; 

 /. lachrymal; pr.f. prefrontal; /"*•. frontal ; po.f. 

 postfrontal; po.o. poslorbital ; ji(. jugal; fa. 

 parietal ; sq. squamosal ; qj ^ quadrato-jugal ; 

 q. quadrate; /.'^(/Z prosquamosal ; pi. palatine; 



ft. pterygoid ; fv. prevomers ; bs. basisphenoid ; curvcs gently outward and downward to 



bo. basioccipital ; stp. stapes ; p.oc. paroccipital ; UuitC with the SquamOSal. 



f.vo. exoccipital ; ;>. interparietal ; <;/o. epiotic. The interparietal: Between the 



parietals posteriorly is a small diamond-shaped bone which extends downwards beyond 

 the parietals and separates the pair of bones below. 



The postfrontal is represented by a fragment of bone between the frontal and 

 parietal whose posterior edge forms the anterior edge of the superior temporal vacuity : 

 the lower edge is missing. 



The postorbital and jugal are not distinct. 



The quadrate resembles that of the other Pelycosauria ; the upper portion is thin 

 and plate-like and the lower end carries two large condyles, the outer somewhat more 



