626 



PKO>. H. Gr. SEELET 0~N THE EEPTILE 



margin, and give it a crenulate appearance, which is due to their 

 elevation. The median ridge terminates in a point, which is rounded 

 and does not project beyond the tooth-margin. The tooth is slightly 

 displaced, and leans backward towards the seventh socket. Low 

 down in the seventh socket the crown of another tooth is seen. The 

 eighth socket is empty. The ninth socket has lost the successional 

 tooth, but displays the external impression, and shows it to have 

 been marked with a median ridge and lateral finer ridges somewhat 

 radiating upward. The tenth socket appears to have been small ; it 

 is imperfectly preserved, and there is no evidence as to its form or 

 character ; but a groove, which is smooth, is placed behind the last 

 socket mentioned, and just in advance of the coronoid process. 

 Hence these teeth appear to differ from those of Iguanodon in the 

 persistent development of a powerful median ridge and in the stri- 

 ation of the external surface. Behind the alveolar border the bone 

 becomes squamous and thin, having overlapped the surangular bone, 

 though there is no trace of a separate coronoid element, from the 

 suture entering into the coronoid process. An opercular bone, or 

 its representative ossification, appears to have extended along the 

 broad subdentary groove at the base of the bone margining its upper 

 part, while the angular bone, if it were distinct from the surangular, 

 would appear to have reached far forward along the base of this 

 groove, and to have rested on a thin ledge of the dentary. The 

 submaxillary groove, in its anterior third, becomes shallow, but 

 persists to the symphysis. The region of the symphysis has no defi- 

 nite outline. 



Two separate teeth, both such as may belong to this species, have 

 been found. They are of small size, and may have belonged to 

 this individual specimen. One belongs to the lower jaw, and might 

 be the eighth tooth of the specimen described. The other is an upper- 

 jaw tooth. The tooth from the lower jaw (PL XXVII. fig. 2) shows 

 that the crown curves outward at a considerable angle to the fang : its 

 outer margin is worn, showing that the teeth worked together with 

 a scissors-like action, the lower-jaw teeth being, as usual, internal 

 to those of the upper jaw. The external surface is marked with 

 about half-a-dozen primary ridges ; between these, in the middle of 

 the tooth, are finer ridges ; and across them run transverse lines of 

 growth. There is no median external ridge. The internal aspect 

 of the crown is essentially the same as in the specimens described 

 in the jaw itself. The median ridge, however, is not prolonged 

 down the fang ; and hence there is a slight constriction at the base 

 of this ridge; and the elevated lateral ridges sharply define this 

 side of the crown from the smooth lateral areas. 



The upper-jaw tooth (PL XXYII. figs. 3, 4) has the crown simi- 

 larly curving inward from the fang. The fang is compressed from 

 side to side, so as to give a subquadrate section. There is a slight 

 constriction between the crown and the fang on the outer or cutting 

 edge, but no constriction on the inner edge. The fang is imperfect 

 at the base ; but the total length of fang and crown, as preserved, is 

 18 millim. The worn surface (fig. 4), like that aspect of the tooth 



