646 BRITISH FOSSIL REPTILES. 



Genus — Nannosdchus,^ Oioen. 



Species — Nannosuchus gracilidens, Ow. Crocodilia, Plate 43, figs. 1 — 10 ; Plate 44, 



figs. 1 and 2. 



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In this genus the teeth have long, slender, sharp-pointed crowns, slightly recurved, 

 mostly sub-circular in transverse section, impressed by a few linear or narrow and shallow 

 grooves. The dental series is pretty uniform as to size and shape of crown, but less so 

 than in the Teleosaur and Gavial ; the teeth are also less numerous and wider apart. 



The claim to generic distinction indicated by the armature of both upper and lower 

 jaws was established by an additional dental character revealed in the following 

 specimen. 



The fore part of the mandible (Plate 43, fig. 1) exhibited a tooth in situ (fig. 1 c and 

 fig. 2 enlarged), answering to that termed the 'anterior canine' in Crocodilia, but 

 presenting characters which I had not before observed in those or other BeptiUa. 



The crown is long in proportion to the basal breadth, conical, recurved, and pointed. 

 It is traversed along the middle of the outer surface by a ridge, or rather a low angle of 

 the enamel, simulating a ridge ; between this and the trenchant hind border is included 

 one third of the outer surface of the crown. This tract is smooth, and, transversely, is 

 feebly depressed or concave, giving a trenchant character to the hinder longitudinally 

 concave edge of the crown. The two thirds of the outer, transversely convex, surface of 

 the crown is traversed by close-set linear grooves, and intervening ridges, which mostly 

 subside at the apical half of the crown, leaving about one third of the apex smooth. 

 This tooth appears to be the fourth counting backward ; the length of the crown is 

 10 mm., the basal breadth 3 min. An enlarged view is given of the outer side of the 

 crown in fig. 2. 



The foremost tooth, also preserved (fig. 1,;), shows a coronal length of 5 mm., a 

 basal breadth of 1 mm. 



The crown of a fifth tooth rises close behind that of the fourth, with a basal breadth 

 of 2 mm , and a length of 5 mm. ; it is conical, but is straight. The outer side, 

 uniformly convex, is traversed along the basal half by fine ridges and intervening grooves ; 

 it may be that the whole of this crown has not emerged. 



The portions of mandible, the subject of fig. 1, consist of the right and left dentary 

 elements, of which the major part is preserved, the rest indicated by impressions on the 

 matrix. The presei'ved parts include the symphysial expansion, the joint being slightly 

 dislocated through pressure, which has acted obliquely. The right dentary shows its 

 outer side, the left dentary its lower border, and beyond the symphysis a small 

 proportion of the outer surface, while the inner one is partly covered by the smooth 

 splenial element (31). 



' vHvi'os, dwarfish, 5!oii^i;s, an Egyptian name of the Crocodile. 



