VIII. Notice on the Iguanodon, a newly discovered fossil reptile, from the sandstone of Tilgate, in Sussex. By Gideon Mantell, F. L. S. and M. G. S. Fellow of the College of Surgeons, &c. In a letter to Davies Gilbert, Esq. M. P. V. P. R. S. &c. &c. &c. Communicated by D. Gilbert, Esq