MAXILLARY BONE OE A NEW LINOSATJB. 441 



corresponding to them have already been obliterated, owing to ab- 

 sorption of their lower borders ; and it seems to me probable that the 

 hinder foramina may have been similarly obliterated with age, the 

 new teeth differing from the nsual snccessional type of Reptiles by 

 being on the outside instead of on the inside of the old tooth. 



The tooth-sockets give no other indication of their existence ex- 

 ternally; but on the inner side of the jaw are eighteen semiovate 

 sockets, largest in the middle and becoming smaller towards the two 

 ends (fig. 2). The last socket of all displays the basal attachment of 

 a tooth to the socket, and shows the socket of the successional tooth 

 in front of it. The sockets are separated from each other by narrow 

 intervals of bone, indicating that the teeth were scarcely so crowded 

 as in Iguanodon, but in this better resembled Scelidosaurus. JSTo 

 specimen shows the fang ; but the crowns of the teeth are like those 

 of Echinodon, Scelidosaurus, and Acanthopholis. The tooth is more 

 compressed from within outward than in Echinodon, and differently 

 implanted ; while it appears to differ from that genus and from Sceli- 

 dosaurus in not having large terminal lateral denticles ; and the 

 maxillary bone in the two has entirely dissimilar forms. 



Of Acanthopholis no evidence of jaws is published except the teeth 

 referred to that genus by Prof. Huxley (Geol. Mag. vol. iv. p. 65) ; 

 but while I have no reason to doubt the excellence of that deter- 

 mination, it may be remembered that no similar teeth have been 

 found in the Cambridge Upper Greensand, in which Acanthopholis 

 is far from rare, and in which its jaws occur. On the other hand, 

 no scutes similar to those of Acanthopholis are recorded from Wealden 

 beds, or from the Great Oolite. The teeth of Priodontognathus re- 

 semble those figured by Prof. Huxley so well that the differences 

 are chiefly limited to those of the present fossil being relatively 

 narrower, having only from five to seven denticles on each serrated 

 side of the crown, wanting the thickening at the base of the crown, 

 terminating in a sharp point, and having a greater inflation in the 

 median line of the tooth, more like that seen in Echinodon and 

 Scelidosaurus. These small points, together with our ignorance of 

 the facial characters of the Greensand and Chalk-marl fossil seem to 

 me to suggest the desirability of the two types being located in 

 separate genera. The only other genus which it resembles is Hylaio- 

 saurus; but of that genus also the maxillary bone is unknown; and the 

 reference of the teeth named Hylcwsaurus to that genus is so hypo- 

 thetical that they may, with almost equal probability, be referred to 

 any other genera of Wealden Dinosaurs of which the dentition is 

 unknown. The crown, moreover, is of different form from that of 

 this fossil ; and though Hylwosaurus has lateral serrations, they are 

 so fine and numerous as not to be a prominent character. 



The maxillary bone terminates anteriorly in a nearly vertical 

 smooth bevelled surface, which is from \ to \ inch wide, and looks 

 forward and outward (figs. 1 & 3, a) ; against this surface the pre- 

 maxillary bone abutted, much after the manner of many mammals 

 and Lizards. 



The superior limit of the maxillary bone in its anterior inch is 



