WEALDEN FORMATIONS. 11 



mandible of Petrosuchus levidens to be 16 inches, or thereabouts, indicating that from 

 four to five inches are wanting at the fore part of the subject of fig. 1. 



The vertical extent of the ramus behind the mandibular vacuity (ib., fig. 3, ») is 1 inch 

 9 lines ; the vacuity itself is 1 inch 6 lines in long diameter, 6 lines in short diameter ; its 

 long axis is nearly parallel with that of the ramus. The lower, like the upper jaw, 

 appears to have been long exposed on its imbedding block of stone. Little of the outer 

 layer of the bone is preserved, and this is limited to parts of the angular and surangular. 

 It here shows a more decided reticulate sculpture, the meshes being in the form of 

 subcircular pits of from 1 to 2 lines in diameter. 



The vertical breadth of the dentary at the terminal point of the angular is 1 inch 3 

 lines ; it loses, as usual, in this diameter as it advances, but irregularly, owing to a gentle 

 undulation of the alveolar border. This is convex where it supports the anterior group 

 of teeth opposed to the premaxillary and foremost upper canine teeth ; it is then slightly 

 concave to the mid-third part, where the border is more feebly convex ; beyond this, after 

 a feeble concavity, it gradually rises to the surangular piece (29). 



Of the foremost group of teeth seven are preserved ; the third counting from the fore- 

 most being the longest and broadest, with the crown curving upward and a little back- 

 ward ; the length of this tooth is 1 inch 4 lines, its extreme breadth is 3 lines, about 

 half of the total length forms the exserted crown, but the point is not entire. The first 

 and fifth of this series are the next in size, but do not exceed an inch in length, the 

 intermediate teeth are smaller ; two or three sockets of still smaller teeth may be traced 

 in the concave part of the border. In the following eonvex part, seven teeth are 

 preserved, with shorter and relatively thicker crowns than in the foremost group ; but 

 none of them showing the robust proportions of the teeth of Goniopholis. Behind this 

 group the indications of teeth and sockets are faint. I estimate the number of teeth in 

 the present ramus at about twenty ; which is the number in the mandibular ramus of 

 Crocodilus champso'ides : a margin of two or three more or less being allowed for a 

 perpetually changing set of teeth. 



The inequality of the size of the teeth and concomitant festooned course of their 

 alveolar series is Crocodilian, as contrasted with the Gavialian and Teleosaurian types. 

 But the temporal and palatonarial openings indicate the generic distinction of Petro- 

 suchus, with its transitional character between the Teleosaurian and Tertiary Crocodiles. 



Portions of dermal scutes, with the pitting as on the mandible, but with wider intervals, 

 are preserved on the slab in which the above-described fossil is imbedded. 



