186 ON REMAINS OF AN EXTINCT SAURIAN, 
From a second, and as far as regards the articular cavity, 
perfect example of this part of the mandible we learn that the 
thickening and flattening of the upper surface of the surangular 
is an effect of age, and that the post-glenoid surface of the 
articular piece is at an early age concave both transversely and 
longitudinally, and is divided by a mesial ridge which is seen 
commencing faintly far beyond the lip of the cavity. 
LEFT PREMAXILLARY OF AN ADULT. 
Prate XI., Fie. 1. 
The present subject yields frequent proofs of the non-identity 
of the fossil reptile with either of the existing species of 
crocodiles, but less certain information respecting its affini- 
ties. By the fracture of the lower surface of the bone we 
are deprived of the opportunity of tracing the exact course of 
the maxillo-premaxillary suture, so important as an aid in the 
classification of the crocodilia. The suture, however, is distinct 
on the edge of the fracture, midway between the longitudinal 
palatine suture and the notch, and yet nearly opposite 
the notch, therefore its direction could not have had 
much, if any, convexity caudad as in most of the crocodilide ; 
but whether it were straight or convex forwards is more 
than we can gather. The suture may be traced somewhat 
dubiously to the foramen opposite the notch, from that point 
outwards and upwards it is totally obliterated. On the upper 
surface the’bone has been partially separated by disarticulation, 
the edge of the resulting sutural surface leaves that of the 
external nares at a very open angle, and is but feebly convex 
backwards. There is no sign that the nasal bones entered into 
the external narial aperture; both the external nares, and the 
anterior palatine foramen appear to have been situated far 
back on the snout, and the shape of the former subcircular, and 
much wider posteriorly than in C. porosus. The notch is entire, 
neither perforated nor emarginated on the edge; the anterior 
two teeth with their sockets are broken away; behind and 
