Royal Society. 551 



Laplace is true only of spheroids of a particular kind, and conse- 

 quently it is to this kind that Laplace's solution of the problem is re- 

 stricted. The method given in the present paper is not confined in 

 its operation to any particular class of spheroids ; the coefficients of 

 the series into which the required function is developed being deter- 

 mined absolutely, and without reference to the form of the spheroid 

 to which they are to be applied. The principal change consists in 

 the different manner of treating the partial differential equation ; 

 and its integration, effected by the author, renders the analysis more 

 direct, the operations more simple, and the theory complete. 



February 18 A paper was in part read, entitled, " Memoir on 



a portion of the Lower Jaw of an Iguanodon, and other Saurian 

 Remains discovered in the strata of Tilgate Forest, in Sussex." By 

 Gideon Algernon Mantell, Esq,, LL.D., F.R.S- 



February 25. — The reading of a paper, entitled, " Memoir on a 

 portion of the Lower Jaw of an Iguanodon, and other Saurian Re- 

 mains discovered in the strata of Tilgate Forest, in Sussex." By 

 Gideon Algernon Mantell, Esq., LL.D., F.R.S., was resumed and 

 concluded. 



When the author communicated to the Royal Society, in the year 

 1825*, a notice on the teeth of an unknown herbivorous reptile, 

 found in the limestone of Tilgate Forest, in Sussex, he Mas in hopes 

 of discovering the jaws, with the teeth attached to it, of the same 

 fossil animal, which might either confirm or modify the inferences 

 he had been led to deduce from an examination of tiie detached 

 teeth. He was, however, disappointed in the object of his search 

 until lately, when he has been fortunate enough to discover a por- 

 tion of the lower jaw of a young individual, in which the fangs of 

 many teeth, and the germs of several of the supplementary teeth, 

 are preserved. The present paper is occupied with a minute and 

 circumstantial description of these specimens, and an elaborate in- 

 quiry into the osteological characters and relations presented by the 

 extinct animals to which they belonged, as compared with existing 

 species of Saurian reptiles ; the whole being illustrated by numerous 

 drawings. The comparison here instituted furnishes apparently con- 

 clusive proof that the fossil thus discovered is a portion of the lower 

 jaw of a reptile of the Lacertine family, belonging to a genus nearly 

 allied to tlie Iguana. From the peculiar structure and condition of 

 the teeth it appears evident that the Iguanodon was herbivorous; 

 and from the form of the bones of the extremities it may be inferred 

 that it was enabled, by its long, slender, prehensile fore-feet, armed 

 with hooked claws, and supported by its enormous hinder limbs, to 

 pull down and feed on the foliage and trunks of the arborescent 

 ferns, constituting the flora of that country, of which this colossal" 

 reptile appears to have been the principal inhabitant. 



Some particulars are added respecting various other fossil bones 

 found in Tilgate Forest, and in particular those of the Hi/laosaurus, 

 or Wealden I^izard (of which genus the author discovered the re- 

 mains of tiiree individuals), and of several other reptiles, as the 



[* See Pliil. Mag., Second Series, vol. ii. p. 444 ; v. p. 153 ; vii. p, 54 : 

 also Third Series, vol. v. p. 77 ; and present Number, p. 568.] 



