PURBECK CROCODILES. 647 



The breadth of the symphysial part of the right dentary is 15 mm. ; the length of the 

 under part of the symphysis is IS mm. At 33 mm. from the fore end the (vertical) 

 breadth of the ramus diminishes to 10 mm., beyond which it gradually increases to 

 15 mm., where the bifnrcation of the bone begins. The entire length of the part 

 preserved is 114 mm. (nearly 4^ inches). 



The exterior of the symphysial part of the dentary is pitted by numerous minute 

 subcircular depressions. As the bone contracts the depressions enlarge and elongate, 

 then take the form of longitudinal grooves of irregular depth ; but these become 

 limited to the lower half of the outer side of the dentary, the part above, which 

 forms the outer alveolar plate, being smooth, with a few faint, short, longitudinal linear 

 impressions. 



The symphysial expanse of the right dentary shows iive sockets, of which, as above 

 stated, the first, fourth, and fifth retain their teeth. The implantation of these teeth in 

 complete sockets confirms the indication by the sculpturing of the bone that the jaw has 

 belonged to a member of the Crocodilian order. 



The first tooth was the smallest ; the second and third, judging from the sockets, 

 gained in size ; the fourth is the largest, and represents, as above remarked, the tooth 

 opposing or interlocking with the premaxillary canine above ; the fifth abruptly loses 

 size. Of the succeeding teeth little more can be divined from the present specimen than 

 that they were small or, at least, slender. The convex curve, lengthwise, of the outer 

 alveolar border is very feeble, and seems to have helped to lodge the hinder teeth ; it is 

 divided by a long feeble concavity from the symphysial or incisive convexity. There is 

 no laniary rising. 



Two smooth bones {3\, x) contribute to the inner wall of the ramus, as exposed on the 

 left side. If the lower one (a^) represents the splenial, the upper one (31) would be an 

 unusually developed inner plate of the dentary. If this, however, should be, as its 

 posterior expansion indicates, according to the analogy of the modern Crocodiles, the 

 splenial element (31), then the lower bone (x), would represent an angular clement 

 unusually produced forward. The longitudinal line of demarcation between these smooth 

 inner questionable elements is not an accidental crack. 



The Crocodilian character of the present jaw is supported by the scutes (PI. 43, 

 fig. 4) and impressions (fig. 5) of scutes, by a vertebra (fig. 3), by portions of ribs with 

 a bifurcate proximal end, and by a metacarpal bone, all on the same slab of matrix. 



The vertebra is Amphicoelian ; the neurapophysial suture is unobliterated ; it is from 

 the part of the trunk where the rib articulation has risen wholly above the centrum. 

 This element is 13 ram. in length ; the non-articular surface is smooth and entire, 

 gradually and slightly expanding to the articular ends ; the one exposed being 

 subcircular, 10 mm. in diameter. 



Of the scutes preserved the largest are oblong, quadrangular, with a tooth-like 

 process from the anterior and outer angle, from the base of which is continued a raised 



20 6 



