684 



PROF. T. H. HUXLEY OBSERVATIONS 



into which the end of the premaxillary beak is received when the 

 mouth is shut. These mandibular rostral processes were probably 

 clothed, like the premaxillary rostrum, with horn; and, with the 

 interlocking premaxillary beak, must have constituted a pair of pincers 

 of great strength. Behind this forked mandibular beak, the upper 

 contour of each ramus is strongly concave upwards, in correspondence 

 with the maxillo-palatal convexity, and its close-set teeth are worn to 

 a sharp scissor-edge, which fitted into the fore part of the mandi- 

 bular groove of the upper jaw. Throughout the symphysial region, 

 the two rami lie close together and form a parallel-sided body of the 

 width of the fore part of the palate ; but, behind, the rami diverge, 

 sweep outwards in a curve which corresponds, at first, with that of 

 the mandibular groove in the broad part of the palate, and then pass 

 to their articulation with the quadrate. The angle of the ramus 

 appears to have extended considerably behind this articulation, but 

 its exact length and shape cannot be determined. 



The alveolar edges of the rami begin to show teeth rather behind 

 the middle of the symphysis, and the series of teeth extends for 60 

 millim. behind this point. In the front part of the series, the teeth 

 are so close-set as to form a palisade-like continuous ridge, worn 

 upon the two faces to a sharp edge. There are about 6 teeth in a 

 length of 10 millim., and each tooth is 5 millim. high, but at about 

 7 millim. from the hinder end of the series the teeth become separate. 

 Here they present rounded summits and their outer surfaces are 

 convex and unworn (Plate XXVI. fig. 6). 



Measurements of parts of the Skull of Hyperodapedon in millimetres. 

 Nasal aperture, 27 long by 24 broad at the base. 

 Orbit, 48 long, 35 wide. 

 Narrowest part of interorbital region, 40. 

 Supratemporal fossa . . 50 long, 45 wide. 

 Parietal region 20 wide. 



Lateral temporal fossa . 23 wide, 41 in perpendicular depth. 

 Premaxillary rostrum . 25 thick at the base from before back- 

 wards. 



„ 30 broad from side to side. 



„ „ 35 in a straight line from base to apex. 



Extreme width of dentigerous area 93 



length „ „ 82 



Width of alveolar face of posterior end of maxilla .... 14 



„ „ „ „ palatal 24 



Diameter of the bases of teeth 3 to 4 



Length of symphysis of mandible 56 



Breadth of middle of symphysis of mandible at narrowest \ ^ 

 between the anterior parts of the dentary edges .... J 



Depth of the rami at this part 30 



Length of each half of the mandibular rostrum from base. 20 

 Greatest depth of ramus from the dentary edge to the \ 



lower border j 



Total length of ramus, probably 190 



Posterior nares 6 wide by 4 long. 



