Royal Society. 51 



others really wishing to compare the facts or to examine into the 

 nature of this most beautiful and interesting class of fossils, the 

 contents of my cabinet will, after August of the present year, be 

 at all times most freely open for inspection. 



J. Toulmin Smith. 



Highgate, 16th June 1848. 



PROCEEDINGS OF LEARNED SOCIETIES. 



ROYAL. SOCIETY. 



May 25, 1847. — " On the structure of the Jaws and Teeth of the 

 Iguanodon." By Gideon Algernon Mantell, Esq., LL.D., F.R.S., 

 Vice-President of the Geological Society, &c. 



The recent discovery of the right dentary bone of the lower jaw 

 of an adult Iguanodon with teeth, having enabled the author, with 

 the aid afforded by other specimens, to determine the structure of the 

 maxillary organs of that gigantic herbivorous reptile, the result of 

 his investigations are embodied in the present communication. 



The first memoir of the author on the teeth of the Iguanodon was 

 published in the Philosophical Transactions for 1825 ; but owing 

 to the fragmentary and water- worn condition in which the fossil re- 

 mains of terrestrial vertebrated animals occur in fluviatile deposits, 

 in consequence of these strata consisting of materials transported from 

 far distant lands, nearly a quarter of a century elapsed before any 

 portion of the jaw with teeth was discovered. 



The most important of the fossils described in this memoir con- 

 sists of the anterior part of the right side of the lower jaw, which was 

 discovered a few weeks since, in a quarry in Tilgate Forest, by Capt. 

 Lambart Brickenden, F.G.S., who with great liberality placed it at 

 the disposal of the author as the original investigator of the fossils 

 of the Wealden. 



This dentary bone, which is eighteen inches long, is perfect in the 

 anterior part, but is broken at the hinder extremity, and retains five 

 or six inches of the coronoid bone : the length of the jaw to which it 

 belonged is estimated at four feet. It contains two successional teeth 

 in place, the fang of a third, and the alveoli or sockets for eighteen 

 or nineteen mature molars ; the entire number of teeth on each side 

 the lower jaw was about twenty. 



The mature teeth, which, when abraded by use in mastication, 

 resemble the worn molars of herbivorous mammalia, appear to have 

 been arranged in a close- set series. The lower teeth had their ena- 

 melled striated face parallel with the alveolar plate, and fronting the 

 inside of the mouth ; but the upper were placed in a reverse position, 

 that is, with the enamelled facet of the crown external; and the 

 teeth in the upper and lower jaws were arranged subalternate or in- 

 termediate in relation to each other, as is the case in the ruminants. 



But a still more remarkable character presented by this specimen 



4* 



