438 J. W. HTJLKE ON IGUANODON PKESTWICHU 



Upper Teeth (PI. XVIII. fig. 7). — The crowns of these are narrower 

 in the antero-posterior direction, and the primary ridge in their 

 outer stoutly enamelled surface is stronger than in the lower teeth, 

 characters noticed hy Melville, Mantell, and also by Owen, which may 

 serve to distinguish these teeth when detached from the jaw. This 

 ridge divides the outer strongly enamelled surface unequally, being 

 much nearer to the anterior margin. At the free end of the unworn 

 crown it ends angularly at the meeting of the anterior and posterior 

 borders. Of these the former is nearly straight, whilst the latter 

 bends towards the angle in a full sweep. The most prominent part 

 of the ridge is nearly at the mid-length of the crown, and from here 

 it declines towards a cingulum, which marks off the crown from the 

 fang. The outer surface between the primary ridge and the front 

 straighter border of the crown has the form of a wide, deep, smooth 

 groove, whilst the space between it and the distant posterior curved 

 border is sculptured by several minor longitudinal ridges, which 

 start from the minuter cusps of the terminal serrature, and are 

 separated from one another by narrow grooves. These secondary 

 ridges are fewer, and the grooves between them narrower towards 

 the middle of the crown, and they subside towards the cingulum. 

 The serrature is limited to the free end and the front and posterior 

 border of the distal half of the crown. In the half next the fang 

 these borders are smooth uninterrupted ridges. The cingulum is a 

 sinuous inconspicuous line crossing the outer surface of the tooth in 

 a double curve, the two ends of which are convex towards the fang. 

 One of these corresponds to the basal end of the primary ridge ; and 

 the other is nearer the distant border of the crown. The cusp be- 

 tween the curves is nearly equidistant from the two borders, but 

 slightly nearer the primary ridge. In a tooth which has descended 

 so far beyond the outer alveolar border that the cingulum is 5-5 to 

 6 millims. distant from it (Eo. 5 in I. 2, fig. 7), the outer surface of 

 the exposed part of the fang is covered by wavy lines. The inner 

 surface of the crown is gently convex, smooth, and even, and un- 

 sculptured, the terminal marginal serration being scarcely prolonged 

 upon it. In a favourable light faint transverse markings are appa- 

 rent on it. A longitudinal swelling subdivides this surface un- 

 equally ; the correspondence of its position to that of the primary 

 ridge on the outer surface makes this the thickest part of the 

 crown. 



The loiuer teeth (PI. XYIII. fig. 6) have much broader crowns than 

 the upper. In the angulation of the hinder margin of the crown, the 

 curve and greater length of the anterior margin, the unequal division 

 of the thickly enamelled inner surface by a primary ridge, they 

 prefigure the teeth of Iguanodon from the Wealden-beds in S.E. Eng- 

 land and the Isle of Wight. They differ, however, from these in one 

 detail, the character of the serrature. The free edge of the small 

 plate-like cusps of this is in such Wealden teeth minutely mamil- 

 lated ; but in these Cumnor teeth the margin of the lamella is even. 

 I found this difference in teeth of very nearly the same size. Perhaps 

 in relative simplicity of sculpturing the Cumnor Iguanodon's teeth 



