SUPPLEMENT (No. I IT) 



TO THE 



MONOGRAPH 



ON THE 



IGUANODON 



Mandible of a young Iguanodon (Tab. X). 



I have been favoured by the Rev. W. Fox, M.A., Rector of Brixton, Isle of 

 Wight, with the inspection of a portion of the left mandibular ramus of an 

 Iguanodon (Tab. X, figs. 1 — 4), including the entire series of alveoli. These are 

 fifteen in number, and are clearly indicated by the angular risings of the outer 

 alveolar wall, forming the intervals or divisions of the alveoli (fig. 4, 1—15). 

 Between the summits of the angular processes the upper margin of the socket is 

 deeply concave, and, the sockets being contiguous, a strongly marked crenate 

 character is given to the border of the outer alveolar wall. 



The longitudinal extent of the alveolar portion of the present ramus is 4 inches 

 3 lines. About an inch of the edentulous fore part of the ramus is preserved, but 

 the symphysial end is broken away. At the opposite part of the fragment it has 

 broken off, about three lines behind the last alveolus, from the rest of the jaw. 



The teeth which occupied the alveolar depressions of the outer wall are gone. 

 The germs of three successional teeth (ib., figs. 1 and 2, 6, 12, 14) are preserved. The 

 summit of the hindmost (14) has risen to the level of the opening of the antepenulti- 

 mate socket ; the next in advance (12) has risen half way towards the outlet of the 

 twelfth socket ; the crown of the third just shows at the bottom of the sixth socket, 

 counting from before backward. Each of these germ-teeth has the inner surface 

 exposed of the summit of the crown, the anterior one showing the least proportion 

 of the tooth. The primary longitudinal ridge (fig. 5, a ) and the marginal serra- 

 tions ( cc') are boldly and beautifully marked on the dark, lustrous enamel, the 

 serrations being continued by grooves, some way upon the exposed inner side of 



