WEALDEN FORMATIONS. 9 



The dental character of Nannosuchus is more fully exemplified by smaller specimens, 

 of which two, forming parts of the lower jaw, will be first noticed. 



The subject of fig. 8, PI. II, includes the dcntary and angular elements, partially 

 dislocated, of the right mandibular ramus. Two of the molary series of teeth are in siiuy 

 showing long, slender, feebly recurved crowns, each 5 mm. in length ; other teeth of 

 similar shape and with finely striate enamel are on the same slab. 



In a smaller dentary (PI. II, fig. 9) the sockets of eighteen teeth are visible. The 

 proportions and outer markings agree with those of the larger specimen. 



The humerus (fig. 10), preserved near the jaw, shows the usual Crocodilian characters, 

 with more slender proportions than in Crocodilus niger ; it rather resembles that of the 

 Gavial.^ ; 



The characters of Nannosuchus yielded by the foregoing specimens are supplemented 

 by those of the skull represented of the natural size in PI. Ill, fig. 1. The teeth 

 preserved in situ and detached, but in contiguity with the alveolar border, are gcnerically 

 those to which they would be opposed assuming the skull to be that of a Nannosuchus. 

 The inferiority of size is not shown by any other distinctive character to indicate a 

 species other than that founded on the lower jaws above described. 



As in those, the teeth of the upper jaw are divided by intervals usually greater than 

 their basal breadth. Each premaxillary (fig. 1, 22) had four teeth at least; the maxillary 

 had not fewer than ten teeth. 



The characters of length and slenderness of crown in the teeth of this small Crocodile 

 suggested a comparison of its skull with that of Petrosuchus^ but the differential 

 characters exceed in importance those of size. The upper jaw of Nannosuchus does 

 not contract so rapidly, or in so great a degree in advance of the orbits, as in Petro- 

 suchus ; it is also shorter as well as broader ; no amount of growth could have 

 converted it into the slender elongate shape which approximates Petrosuchtis to the 

 gavial-like Crocodilus cataphractus. 



The hind border of the parieto-mastoid platform is undulate ; gently convex at the 

 middle, where it is formed by the parietal (ib., 7), concave on each side, where it is (jarried 

 out by the mastoids (ib., s). 



In Crocodilus niger this border is straight ; in Croc, palustris it is undulate, but the 

 middle parietal convexity is much less than the lateral, concave, mastoidean curves, 

 owing to the relatively narrower extent of the parietal bone. The lateral borders of the 

 supra-cranial platform, due to the mastoids (ib., 8) and post-frontals (ib., 12), present, in 

 Naimosuchus, a gentle sigmoid curve. In most modern Crocodilia these borders are 

 straight, running parallel in Croc, niger^ slightly convergent forwards in Croc, cata- 

 phractus and Croc, intermedius. 



The breadth of the platform is to that of the skull, taken across and including the 



1 ' Catalogue of Osteology, Mus. Coll. Chir.,' 4to, 1853, p. 153, No. 691. 



2 Supplement (No. viii) ia Palaeontographical Soc. Volume for 1878, Plate VI. 



11 



