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XVI. On the Pelorosaurus ; an undescrihed gigantic terrestrial reptile whose remains 
are associated with those of the Iguanodon and other Saurians in the Strata of 
Tilgate Forest, in Sussex. 
By Gideon Algernon Mantell, Esq., LL.D., F.R.S., F.L.S., 
Fice- President of the Geological Society, 8fc. 
Received November 22, 1849, — Read February 14, 1850. 
I HAD for a long while entertained the idea that among the fossil remains collected 
from the Wealden deposits of the South-East of England, there were indications of an 
enormous Lizard entirely distinct from the Iguanodon, Megalosaurus, Cetiosaurus, 
and other genera which have been named and more or less accurately determined ; 
and I have at length obtained such evidence in support of my opinion, as induces me 
to submit to the Royal Society the data which appear to establish the existence of a 
terrestrial reptile contemporary with the Iguanodon, and which equalled, if not sur- 
passed in magnitude, that colossal herbivorous Saurian. 
I shall not on the present occasion enter upon those minute anatomical details 
which are indispensable for the solution of many of the difficult problems which but 
too often perplex and bewilder the palaeontologist, but content myself with faithful 
descriptions and figures of such facts as will suffice to establish my proposition ; in 
the hope that these guesses at truth, which recent investigations have suggested to 
my mind, may serve to direct future labourers in the right path of inquiry, and tend 
to enlarge our knowledge of that remarkable fauna which prevailed in the islands and 
continents of the Cretaceous, Wealden, and Oolitic ages. 
The occurrence of very large isolated vertebrae, and portions of femora with medul- 
lary cavities, indicating animals of terrestrial habits, and of great size, and which, 
though assigned to the Cetiosaurus, could not properly be included in a genus of 
aquatic marine reptiles with solid bones like the Cetaceans, first suggested to me 
the probability of there having existed another genus of Saurians contemporary with 
those previously mentioned, and to which some of the supposed Cetiosaurian remains 
might belong. This idea, though vague, seemed to offer an explanation of certain 
discrepancies between some of my statements and those of other cultivators of this 
branch of comparative anatomy. 
The stupendous humerus or arm-bone of a terrestrial reptile from the strata of 
Tilgate Forest, in Sussex, which I have now the honour to place before the Royal 
Society, will, I believe, establish the correctness of that opinion. 
This splendid fossil was obtained from the locality in which was situated the 
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