294 BRITISH FOSSIL REPTILES 



there is no appearance of a sutural attachment in its longitudinal extent, with a pai-allel 

 and co-extensive squamosal bone, as in the Crocodilia : the points of connection seem 

 to have been restricted to the two expanded extremities. 



Loioer Jaw of the Iguunodon. Plates 16, 17, 18. Nat. size. 



At the beginning of the year 1848, Mr. George B. Holmes, of Horsham, obtained 

 from the Stammerham stone-pit, or quarry, of Wealden, near that town, the right 

 ramus of the lower jaw of a young Iguanodon, which is figui'ed of the natural size in 

 Plates 16 and 17. 



The accurate and beautiful drawings made by his daughter. Miss G. M. Holmes, 

 from w^hich these plates are engraved, were most liberally transmitted to me, at that 

 time, for description. Learning, however, from Dr. ^Mantell, when I was about to 

 communicate that description to the Geological Society, that he also had just received 

 from Captain Brickenden, of Warrainglid, Sussex, the lower jaw of a larger Iguanodon 

 which he was desirous to describe for the Royal Society of London, I declined to use 

 the materials with which Mr. Holmes had favoured me, until Dr. Mantell's observations 

 had appeared. His Memoir was accordingly published in the ' Philosophical Transac- 

 tions,' Part II, 1848. 



The most remarkable conclusion to which the author of that Memoir arrived, after 

 a study of the above materials, was, that the Iguanodon had been endowed, not only 

 with fleshy or muscular lips,* hitherto believed to be the peculiar characteristic of the 

 mammalian class amongst air-breathing vertebrate animals, but with such lips greatly 

 developed.! 



The correlation or association of such muscular and sensitive appendages to the 

 jaws with the necessity of deriving lacteal nourishment by the act of suction, during the 

 infancy of the animal, has hitherto been so constant and exclusive in the air-breatliing 

 vertebrates, that a transition from the Reptilian to the Mammalian class, by the con- 

 junction of fleshy lips with a scaly skin and cold blood, would be a most unexpected and 

 extreme exception to one of the best established generalizations in Comparative Anatomy. 



I shall, first, give a description of the portion of jaw from Stammerham, then 

 compare it with the larger jaw obtained from Tilgate Forest, and finally endeavour to 



* "The great size and number of the vascular foramina, &c., indicate the great development of the 

 integuments and soft parts with which the lower jaw was invested." Phil. Trans. 1848, p. lOT. 



t " The sharp ridge bordering the deep groove of the symphysis, in which there are also several 

 foramina, evidently gave attachment to the muscles and integuments of the under lip ; and there are strong 

 reasons for supposing that the latter was greatly produced, and capable of being protruded and retracted, 

 so as to constitute, in conjunction with a large fleshy prehensile tongue, a powerful instrument," &c., p. 197. 

 The author proceeds to infer from "the edentulous and prolonged symphysis, and the great development 

 of the lower lip and the integuments of the jaws, as indicated by the number of vascular foramina, a striking 

 analogy to the edentata." lb., p. 198. 



