PLESIOSAURUS. 209 
This hypothesis of Cuvier is but conjectural, 
respecting the power of the Plesiosaurus to 
change the colour of its skin ; and to the un- 
experienced in comparative anatomy, it may 
seem equally conjectural, to deduce any other 
conclusions respecting such perishable organs 
as the lungs, from the discovery of peculiar con- 
trivances, and unusual apparatus in the ribs ; 
yet we argue on similar grounds, w^hen from the 
form and capabilities of these fossil ribs, we infer 
that they were connected, as in the cameleon, 
with vast and unusual powers of expansion and 
contraction in the lungs ; and when, on finding 
the ribs and wood-work of a w^orn-out bellows, 
near the ruins of a blacksmith's forge, we con- 
clude that these more enduring parts of the 
possessing the power of altering the colour of its skin ; it must 
however be admitted that such a power would have been of 
much advantage to this animal, in defending it by concealment 
from its most formidable enemy the Ichthyosaurus, with which, 
its diminutive head and long slender neck, must have rendered 
it a very unequal combatant, and from whose attacks its slow 
locomotive powers must have made escape by flight impossible ; 
the enlarged condition of the lungs, w^ould also have been of 
great advantage in diminishing the frequency of its ascents to 
the surface, to inspire air; an operation that must have been 
attended with constant danger, in a sea thickly swarming with 
Ichthyosauri. Dr. Stark has recently observed that certain fishes, 
especially minnows, have a tendency to assume the colour of the 
vessel in which they are kept. (Proceedings Zool. Soc. Lond. 
July, 1833.) As in animals of this class there are no lungs, 
this change of colour must arise from other cause than that to 
which it has been attributed in the Cameleon. 
GEOL. p 
