1859.] 0WEX REPTILIAN FOSSILS. 51 



upon the upper surface of the cranium (fig. 5), quickly subsiding to 

 form the inner boundary of the temporal fossa?, and finally curving 

 outward to the back part of the orbits. There is no trace of median 

 suture between the parietaks ; these form one bone, perforated by a 

 small "foramen parietale " close to the coronal suture. The frontals 

 (n) are broader than they are long, and contribute a small share to 

 the superorbital border. Anterior to the two tuberosities of the 

 vertex the median suture between the frontals is distinct ; and the 

 suture is continued forward, between the nasals (15), beyond the 

 anterior transverse ridge upon the straight sloping part of the skull, 

 for nearly an inch, where the nasals join the premaxillary bone. 

 The superorbital prominence is developed by a large subtriangular 

 " prefrontal " (u), the outer surface of which is divided into a hori- 

 zontal facet and a sloping facet by the outer parts of the anterior 

 transverse cranial ridge. The lacrymal (73) forms the fore part of 

 the orbit, extending nearly half an inch forward upon the face ; the 

 outer surface of the premaxillary (fig. 5 22) is traversed by a low 

 median ridge dividing the upper, nearly flat, elongated surface of the 

 bone. The sides of the premaxillary (fig. 3 22) bend abruptly down 

 in front of the nostrils, at a slightly open angle with the upper sur- 

 face, to join the maxillaries about 8 lines below the angular bend. 

 The maxillaries (ib. 21) form the lower boundary of the nostrils, 

 and join above and behind with the prefrontal, lacrymal, and nasal 

 bones : their outer surface is divided by the strong ridge which has 

 suggested the subgeneric name for the fossil. This ridge, commencing 

 below the orbit, where it seems to be a forward continuation of 

 the zygoma, becomes more prominent as it extends forward, and 

 soon forms the outer angle of the three-sided socket of the canine 

 tusk. One side of this socket is formed by the upper and outwardly 

 concave surface of the maxillary, a second side by the lower and 

 equally concave surface, and the third side by the inner and inwardly 

 convex nasal plate of the maxillary. The sockets diverge as they 

 descend, with a slight curve, convex outwards. The lower jaw is 

 edentulous; it is deep and broad in proportion to its length ; it is 

 composed according to the type of the mandible in the Dioynodons 

 proper, but with the tore part of the broad symphysis more pro- 

 duced and hent upward, like the fore part of the lower mandible 

 in some Parrots. 



For the spei tea indicated by the nbove-described minium I have 

 proposed the name of Ptychognathut deelwiB. 



Ptychognathxu latirostris, <>w. 

 A second species of Ptychognaikiu is indicated by a skull which in 



in its facial part LS broader and shorter, and which has the orbits of 



a more circular form. \it presenting the uotch at the upper and back 

 part. The sloping facial pari of the skull presents the same Btraighl 



outline, and is of the same length, viz. 4 inches, B8 in /'/. d&Mvia : but 



it> breadth at the base of the canine sockets is :* inches 2 lines, 

 beyond which they slight 1\ expand; and the ridges of these Bookets 

 a to project nearer to the orbits. 



1 a 



