400 CRETACEOUS REPTILES. 
The tooth may be a variety of the Plesiosaurian type, or it may have belonged 
to a Steneosauroid Crocodilian. It was obtained from the same chalk-pit, at 
Houghton, near Arundel, as the vertebra of the Plestosaurus Bernardi. 
Genus IcHTHYOSAURUS™*. 
Species. Ich. communis? (Tab. XXXIX. fig. 10.) 
These teeth were found in Kent, and are now in the museum of William 
Harris, Esq., F.G.S. Other teeth of the same species are preserved in the well- 
arranged and instructive cabinet of the Rev. Thomas Image, M.A., rector of 
Whepstead, Suffolk: these were discovered in the chalk near Cambridge. Mr. 
Dixon had informed me that he was not aware of any specimen of Ichthyosaurus 
having been found in Sussex. 
The group of teeth figured in Tab. XX XIX. fig. 10. belong unquestionably 
to the genus Ichthyosaurus, and so closely correspond in form and size with 
those of the Ichthyosaurus communis, that I cannot presume, in the absence of 
any knowledge of the characters of the vertebre or paddles, to pronounce them 
to belong to a distinct species. 
Order PTEROSAURIA, Owen. 
Genus PreroDACTYLUS. 
Within the last few years several new species of ‘ Pterodactyle’ have been dis- 
covered in the secondary strata from the lias to the chalk inclusive. The form 
of these extinct flying Lizards is so extraordinary as to have given rise to differ- 
ent conjectures or theories respecting their nature and affinities ; some palzon- 
tologists supposing them to have been a kind of Bat, others a modified Bird ; 
but the conclusions to which Cuvier finally arrived are those now generally 
adopted, viz. that, on account of the construction of the skull, the compound 
lower jaw supported by tympanic pedicles, and the teeth inserted into distinct 
sockets, the Pterodactyle was a Saurian reptile or Lizard ; but with the bones of 
the fore-arm and hand singularly elongated like those in the bat, and the bones 
light and hollow, as in the bird, thus adapting the creature to powerful and rapid 
flight, with probably the power of swimming. Remains of specimens equalling 
* The reader who may desire to be made acquainted with the general characters of this extinct 
Sea-lizard is referred to the excellent ‘ Bridgewater Treatise’ by Dr. Buckland. 
