170 
MARINE SAURIANS. 
another in the general principles of their con- 
stniction, and the possession of those peculiar 
organs, in which I shall endeavour to point out 
the presence of mechanism and contrivance, 
adapted to their habits and state of life. As 
it will be foreign to our purpose to enter on 
details respecting species, I shall content myself 
with referring to the figures of the four most 
common forms (Plates 7, 8, 9.)* 
Head. 
The head, which in all animals forms the most 
important and characteristic part, (see PI. 10, 
* PI. 7, is a large and nearly perfect specimen of the Ichthy- 
osaurus Platyodon, from the lias at Lyme Regis, being one of 
the splendid series of Saurians, purchased in 1834 of Mr. 
Hawkins by the British Museum. Portions of the paddles, and 
many lost fragments, are restored from the corresponding parts 
which are preserved ; a few vertebrae, and the extremity of 
the tail are also restored conjecturally. Beautiful and accurate 
lithographed figures of this specimen, and of the greater part of 
this collection, are published in Mr. Hawkins's Memoirs of 
Ichthyosauri and Plesiosauri, London, 1834. PL 8. Fig. l,is a 
small specimen of the Ichthyosaurus Communis, from the lias 
at Lyme-Regis, belonging to the Geol. Soc. of London. PI. 8, 
Fig. 2, a small Ichthyosaurus Intermedins, from the lias at Lyme 
Regis belonging to Sir Astley Cooper. PI. 9, Fig. 1, an Ichthy- 
osaurus Tenuirostris, from the lias of Street, near Glastonbury, in 
the collection of Rev. D. Williams. Fig. 2 is the continuation 
of the tail, and Fig. 3, the reverse of the head. The teeth in 
this species arc small, and in due proportion to the slender 
character of the snout. 
