DICYNODONTIA. 259 



perforated by a small " foramen parietale " close to the coronal 

 suture. The frontals (3 b, «) are broader than they are long, 

 and contribute a small share to the superorbital border ; their 

 median suture is distinct, and is continued forward, between 

 the nasals (15), beyond the anterior transverse ridge upon the 

 straight sloping part of the skull, to where the nasals join the 

 premaxillary bone (22). The superorbital prominence (3 a, h) 

 is developed by a large subtriangular prefrontal (14). The 

 lacrymal (13) forms the fore part of the orbit, extending 

 nearly half an inch forward upon the face. The sides of the 

 premaxillary (ib. 22) bend abruptly down in front of the 

 nostrils, to join the maxillaries (ib. 21) ; these 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 sub- 

 generic 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. The rami of the lower jaw augment in depth 

 from the angle to the symphysis, where they are confluent. 

 The angle projects a very little way beyond the articulation. 

 The articular surface is moderately concave, and looks 

 obliquely upward and backward. The elements of the pos- 

 terior half of the ramus, answering to the articular, angular, 

 and surangular in lizards, appear to form one piece (3 a, 30). 

 A thin vertical splenial plate, on the inner side of the 

 ramus, begins about an inch in advance of the angle, and 

 extends forward to the symphysis, at the back part of which 

 it appears to become confluent with its fellow. The part 

 answering to the angular diverges from the surangular, and 

 forms the hind boundary of an oblong vacuity at the middle 

 of the side of the ramus, the fore part of which vacuity is 

 formed by a bifurcation of the dentary element (32). The 



