672 



PROF. H. Gr. SEELE1' OX THE REPTILE 



out reaching back to the articular region. The jaws converge 

 forward to the symphysis, where the contraction ceases, and there 

 is a slight anterior expansion before the lanceolate anterior termi- 

 nation. The greatest width of this slight expansion is 2| centim. ; 

 and the width of the diverging rami at 10 or 11 centim. from 

 the anterior termination is over 5 centim. ; thus the jaw is re- 

 markably pointed. The lateral contour of the alveolar margin 

 is convex from before backwards in the region of the symphysis and 

 concave in length behind the symphysis. The symphysis is 3 cen- 

 timetres long, and is made up in the anterior and inferior part by the 

 dcntarybone, and in the posterior and superior part by the opercular 

 bone, which, on the alveolar aspect, forms half the symplrysis, while 

 interiorly it only constitutes the hinder fifth. In Crocodiles the oper- 

 cular bone does not enter, into the symphysis. The anterior part of 

 the jaw in the symphysial region is excavated in a. spoon-shape, 

 owing to the remarkable and vertical elevation of the alveolar margin, 

 an elevation which appears to have relation to the straightness and 

 vertical position of the teeth ; so that the fangs could not have made an 

 angle with the crown. The whole inner side of the ramus is formed, 

 as in crocodiles, by the opercular bone, which, as Biinzel remarks, 

 is smooth and slightly rounded at its inferior and superior margins, 

 and extends back beyond the alveoli, only showing in its anterior 

 part two or three nutritive foramina. The external surface of the 

 bone is formed of the dentary element, except, it may be, towards 

 the hinder superior border, where a suture appears to indicate on 

 the inner side a coronoid bone. On the under surface the jaw is 

 flattened at the symphysis, but the flattened area rounds up an- 

 teriorly to the alveolar margin ; but where the rami begin to diverge, 

 there is a distinct sharp angle between the base of the jaw and its 

 side, and this ridge is prolonged backwards for a large part of the 

 region through which the teeth extend : and here the base of the 

 ramus is slightly convex from side to side till, with the fading of 

 the angle into the upper surface, it becomes more rounded and nar- 

 rower. The suture for the opercular bone runs along the inner 

 third of the base. In ornament, the anterior expanded end of the 

 snout is pitted much after the pattern of crocodile^, and evidently 

 with similar relation to a vascular condition : but interiorly the 

 ramus is marked with rough, short, irregular longitudinal ridges, 

 which extend round onto the side but do not rise to the alveolar 

 region, Avhich is comparatively smooth and marked with a row 

 of relatively large foramina, about seven or eight in number, 

 and placed above the middle of the lateral margin in a concave 

 line or groove. As they extend backwards they rise nearer to the 

 alveolar margin, and form the basis of a slight compression of the 

 bone above them. Posterior to the symphysis the depth of the 

 jaw increases : it is about 9 millim. in front, 17 millim. at the 

 last tooth-socket, and 3 centim. in the coronoid region ; so that 

 it increases in depth more rapidly behind the teeth. It is 

 difficult to count the exact number of sockets ; for some of 

 the fangs are preserved, and in other cases the teeth have fallen 



