MK. J. W. HULKE ON THE MAXILLA OF IGTIANODON. 435 



36. On the Maxilla of Igtjanodon. 

 By J. W. HuLKE, Esq., F.R.S., F.G.S. (Read May 12, 1886.) 



[Plate XIV.] 



So few cranial remains of Iguanodon have been recorded in this 

 country that two fine fragments representing nearly the entire left 

 maxilla have seemed to me deserving of being brought under the 

 notice of the Geological Society*. They derive an additional 

 interest in having been found at Cuckfield, the locality rendered 

 famous by Dr. Mantell's discovery there of a tooth f, the first of 

 that grand series of remains on which, jointly with Dr. Melville, he 

 established the genus. The combined lengths of the two pieces 

 amount to 29 centim., but a small intermediate fragment is missing, 

 and if we estimate this at 1 centim., the length of the entire maxilla 

 will have been not under 30 centim. The maximum vertical 

 measurement in the present state of the jaw is Q-2 centim. These 

 proportions show the form of jaw to be relatively longer and more 

 slender than that of Hypsilophodon, from which it also differs in the 

 bluntly rounded, not tapering, shape of its posterior extremity. 



The external surface of the jaw slopes outwards as it ascends 

 towards the upper border, and in the articulated skull would over- 

 hang the outer alveolar margin. It is perforated by a series of 

 conspicuous vascular foramina. The inner surface of the bone is 

 nearly plane in its posterior, and gently concave in its anterior half. 

 I do not find any indication of palatal expansions. The upper border, 

 the stoutest part of the bone, exhibits a deep sunken groove, which 

 begins in a shallow pit (prelacrymal fossa) opening on the outer surface 

 of the maxilla at 4*5 centim. from its posterior extremity. This 

 groove contracts at a short distance from the external opening, and 

 then, dilating vertically, it passes forward along the bone, and 

 becoming much wider and shallower in the anterior half seems to 

 have led here into the nasal passages. I found indications of this 

 canal in the maxilla of /. Prestivichii. Anteriorly the upper border 

 becomes compressed and thinned, and there is evidence that, as in 

 Hypsilophodon, the thinned bifid end was overlapped by the body of 

 the premaxilla, an outer ascending or maxillary process of which 

 was received in the wide shallow anterior part of the groove just 

 mentioned. Posteriorly the upper border was overlapped by the outer 

 border of the nasal, and behind this by the lacrymal bone, which 

 contributed with the maxilla to form the prelacrymal opening. 



The outer lip of the dentary border is crenated by the openings of 

 19 alveoli ; and assuming that the missing piece contained 3, the 

 number of teeth in the working line would be 22, a number agreeing 

 fairly with that in /. hernissm-tensis %• The teeth exhibit the 



* I offer ray best thanks to Dr. Willett for most courteously affording me 

 an opportunity of studying these fossils and bringing them under your notice. 



t About the year 1820. 



\ Dollo, Quatrieme note, in Bulletin du Mus. d'Hist. Nat. de Belgique, t. ii. 

 (1883). 



