§41. 



HORN OF THE IGUANODON. 



431 



Horn of the Iguanodon. The Iguanas are distinguished 

 among the lacertian reptiles, for their exuberant dermal 

 appendages. Some have serrated processes or spines on 

 the back ; others on the tail ; while many have conical 

 warts or horny protuberances on the head and snout, 

 of which the Iguana cornuta is a remarkable example.* 

 A fossil possessing the form and structure of these 

 nasal tubercles, was found, many 

 years since, in the grit of Tilgate 

 Forest ;f another specimen, about 

 one-third the size, has also been 

 discovered. It is composed of bone, 

 and has that singular disposition of 

 the osseous fibres that prevails in 

 the dermal bones of certain reptiles. 

 Its surface shows the impressions of 

 the vessels of the integument by 

 which it was originally covered. 

 It is four inches high ; and the 

 base, which is of an irregular ellip- 

 tical form, is 3.2 inches by 2.1. 

 Though there is no evidence to prove that this process 

 belonged to the Iguanodon, there can be no doubt of its 

 being a horn, or nasal tubercle, of one of the large reptiles 

 with whose bones it was found collocated. It may possibly 

 be referable to the Hylasosaurus, in which the dermal appen- 

 dages appear to have been enormously developed ; but in the 

 absence of all proof, and from the close resemblance which 

 the fossil bears to the horn on the snout of the Iguana 

 cornuta, we would provisionally refer it to the Iguanodon. 



41. Femur, &c. of the Iguanodon. — Several specimens 

 of the femur or thigh-bone, of the bones of the hind legs, 

 and of the metatarsal, phalangeal, and ungueal bones, have 



* See Philos. Trans, for 1841, PI. IX. fig. 3. 



t It is figured in Fossils of Tilgate Forest, PI. XX. fig. 8. 



Lign. 106. — Horn of the 

 Iguanodon ; from Tilgate 

 Forest. 

 (One-third natural size.) 



