TEETH OF THE IGUANODON. 



42o 



the base was indented, not broken off; proving that the 

 shank had been removed by absorption from the pressure 

 of a new tooth, which had grown up, and caused the old 

 one to be thrown off. 



Lign. 103. — Tooth of the Igttanodon : from Tilgate Forest, fnat. size.) 



Fig. 1. Front aspect, showing the longitudinal ridges, and denticulated margins of 

 the crown : a, the denticulated margin ; b, apex of the crown partly worn by use i 

 c, transverse fracture of the fang, exposing a section of the medullary cavity 

 occupied by the ossified remains of the pulp ; d, the base of the denticulated 

 border. 



Fig. 2. The inner aspect of the same. 



In the series of teeth before us (Ligns. 102, 103, 104), we may trace every 

 gradation of this change ; from the pointed, angular, perfect crown and 

 fang {Lign. 102, fig. 2), and the partially worn specimen (figs. 4, 5), 

 to the mere stump (figs. 1,3): in which the summit is ground flat, and 

 the shank entirely absorbed from the pressure of a successional tooth. 

 The perfect teeth of the Iguanoclon are distinguished by their prisma- 

 tic form ; the presence of from two to four or five ridges, which extend 

 down the front ; and the denticulated lateral margins of the crown 

 (Lign. 102, fig. 6). The latter appear as simple serrations in the 

 figure, Lign. 103,a ; but when viewed laterally (Lign. 102, fig. 6), are 

 found to consist of denticulated plates. 



