[ 64 ] 

 IX. Proceedings of Learned Societies. 



ROYAL SOCIETY. 



[Continued from vol. xxxiv. p. 532.] 



March 8, " A DDITIONAL Observations on the Osteology of the 



1849. -^ Iguanodon and Hylaeosaurus." By Gideon Alger- 

 non Mantell, Esq., LL.D., F.R.S., V.P.G.S., &c. 



This memoir is supplementary to the author's former communi- 

 cations to the Royal Society on the same subject, and comprises an 

 account of some important additions which he has lately made to 

 our previous knowledge of the osteological structure of the colossal 

 reptiles of the Wealden of the South-east of England. 



The acquisition of some gigantic and well-preserved vertebrae and 

 bones of the extremities from the Isle of Wight, and of other in- 

 structive specimens from Sussex and Surrey, induced the author to 

 resume his examination of the detached parts of the skeletons of the 

 Wealden reptiles in the British Museum, and in several private col- 

 lections; and he states as the most important result of his investi- 

 gations, the determination of the structure of the vertebral column, 

 pectoral arch, and anterior extremities of the Iguanodon. In the la- 

 borious and difficult task of examining and comparing the numerous 

 detached, and for the most part mutilated bones of the spinal column, 

 Dr. Mantell expresses his deep obligation to Dr. G. A. Melville, 

 whose elaborate and accurate anatomical description of the vertebrae 

 is appended to the memoir. The most interesting fossil remains are 

 described in detail in the following order. 



Lower Jaw. — Since the author's communication on the lower jaw 

 of the Iguanodon, published in the Philosophical Transactions, part 

 ii. ] 848, he has discovered the right angular bone, which was pre- 

 viously unknown: from the circumstances under which this relic 

 was found, he considers it probable that it belonged to the same 

 individual as the teeth figured in Plate XVIII. of the Philosophical 

 Transactions for 1848. 



Vertebral column. — The vertebrae hitherto assigned to the Igua- 

 nodon consist of the middle and posterior dorsal and anterior cau- 

 dal, as identified by means of the Maidstone specimen in the British 

 Museum : the cervical, anterior dorsal, lumbar, and posterior and 

 terminal caudals, were previously either undetermined or referred to 

 other genera of saurians. The investigations of Dr. Melville have 

 established the important and highly interesting fact, that the cervi- 

 cal and anterior dorsal vertebrae of the Iguanodon were convexo- 

 concave— that is, convex in front and concave behind — as in the 

 fossil reptile of Honfleur termed Sireptospondylus, and in the exist- 

 ing pachyderms ; the convexity gradually diminishing, and the an- 

 terior face of the body of the vertebra becoming flat, in the middle 

 and posterior part of the dorsal region. The supposed Streptospon- 

 dylian vertebrae of the Wealden (named S.major by Professor Owen 

 in British Association Reports on fossil reptiles) are, in the opinion 

 of the author and Dr. Melville, the true cervical vertebrae of the 



