i8o Mr. Mantell on the iguanodon, 
form the subject of this communication. The existence of a 
gigantic species of crocodile in the waters which deposited 
the sandstone, is satisfactorily proved by the occurrence of 
numerous conical striated teeth, and of bones possessing the 
osteological characters peculiar to the animals of that genus ; 
of the megalosaurus, by the presence of teeth and bones re- 
sembling those discovered by Professor Buckland in the 
Stonesfield slate ; and of the plesiosaurus, by the vertebrae 
and teeth analogous to those of that animal. 
The teeth of the crocodile, megalosaurus and plesiosaurus, 
differ so materially from each other, and from those of the 
other lacertae, as be to identified without difficulty ; but in the 
summer of 1822, others were discovered in the same strata, 
which although evidently referable to some herbivorous rep- 
tile, possessed characters so remarkable, that the most super- 
ficial observer would have been struck with their appearance, 
as indicating something novel and interesting. As these 
teeth were distinct from any that had previously come under 
my notice, I felt anxious to submit them to the examination 
of persons whose knowledge and means of observation were 
more extensive than my own ; I therefore transmitted spe- 
cimens to some of the most eminent naturalists in this coun- 
try, and on the continent. But although my communications 
were acknowledged with that candour and liberality which 
constantly characterises the intercourse of scientific men, yet 
no light was thrown upon the subject, except by the illus- 
trious Baron Cuvier, whose opinions will best appear by the 
following extract from the correspondence with which he 
honoured me. 
“ Ces dents me sont certainement inconnues ; elles ne sont 
