FROM THE KIMMEEIDGE CLAY. 437 



Jaws. — Other very instructive pieces are fragments of both 

 m axillae and of both rami of the mandible. Of the maxillary frag- 

 ments, ISTo. I. 2 is the most important. Its outer alveolar border, 

 77 millims. long, has in this space the sockets of 9 teeth. Imme- 

 diately above this free border the bone rapidly swells, acquiring 

 greater bulk mainly by expansion of the outer wall, which in its 

 ascent slants outwards as high as the level of the upper ends of the 

 tooth-fangs, above which it again falls inwards towards the mesial 

 line. The inner dentary wall, a thin plate, rises nearly vertically 

 as high as the tops of the tooth-fangs, above which it bends out- 

 wards, and joins the outer wall of the bone. 



Above the alveolar border the outer surface of the maxilla is 

 pierced by a row of conspicuous foramina, as in Megalosaurus and 

 Teratoscmrus. 



Yiewed from above, this piece of the upper jaw shows at the inner 

 side the smooth surface overlying the ends of the tooth-fangs, and 

 outside this a broken edge. Nearly in the middle of this edge, 

 sunken in the substance of the base, outside the tooth-fangs, is a 

 remarkable oval pit, 13 X 7 millims. across at its mouth, and 

 7 millims. deep. Its surface is perfectly smooth. The outer 

 margin of this pit is a thin smooth lip, which apparently formed the 

 lower border of a conjugate anteorbital foramen. Behind, at its inner 

 side in the dry skull, the pit seems to have freely communicated 

 with the naso-buccal cavities. Behind the pit is a narrow groove, of 

 which the outer border is a thin natural edge. I am disposed to 

 view this as the sutural groove for the reception of the front margin 

 of the jugal bone, which fixes this as the hinder part of the jaw, and 

 shows it to belong to the left side. In front of the pit is another, 

 wider groove, the significance of which is less obvious. In the piece 

 No. I. 5, the corresponding part of the right maxilla, this groove 

 descends from the pit forwards in the substance of the jaw outside 

 the teeth. Near its origin it is joined by a lesser channel, which 

 begins not far from the jugal groove near the back of the jaw, and 

 passes forward skirting the inner border of the pit. Do this pit 

 and the wide groove proceeding from it represent the glandular 

 grooves which tunnel the hinder part of the maxilla in the crocodile? 

 May the lesser groove have transmitted a branch of the 5th nerve ? 

 Less imperfect materials must answer these questions. 



The fossils No. I. 3, 4, are considerable portions of the mandibular 

 rami. They have the well-known Iguanodont form, and do not 

 need particular description. 



Dentition. — In every piece of maxilla or mandible holding teeth, 

 the crowns of all which were in full wear at the animal's death 

 have been broken off and lost; in most instances this damage is 

 quite recent ; but their fangs and the germs of many successional 

 teeth remain, and these afford very complete information respecting 

 the perfect form of the mature upper and lower teeth, and also of 

 the manner of succession. 



The crown has the compressed, ridged, serrate form characteristic 

 of the family Iguanodontidae. 



