26 
FOSSIL REPTILIA OF THE LOWER LIAS. 
to have had the chief share in the removal and displacement of so large a proportion 
of its coat of mail. Subsequent cosmical violence has been concerned in the 
fracture, the crushing, and in a certain amount of displacement of the constituent 
parts of the skeleton. Lastly, further fracture of the fossil bones has been due to 
the quarrying operations, by which the specimen was brought to light. 
Conditions of imbedding and deposit. 
The general condition of this almost entire skeleton of a reptile, organized, as 
seems by the structure and proportions of the hind foot, for terrestrial rather than 
aquatic life, or at least for amphibious habits on the margins of a river rather 
than for pursuit of food in the open sea, I infer that the carcass of the dead 
animal has been drifted down a river, disemboguing in the Liassic ocean, on the 
muddy bottom of which it would settle down when the skin had been so far 
decomposed as to permit the escape of the gases engendered by putrefaction. In 
that predicament the carcass would attract large carnivorous marine fishes and 
reptiles, and portions of the skin, with prominent parts not too strongly attached 
to the trunk, -would probably be torn away before the weight of the bones had 
completely buried the carcass in the mud. In this way, perhaps, we may account 
for the loss of much of the dermo-.skeleton and of the two fore paddles. The 
larger hind limbs with their stronger muscles and ligaments, would offer better 
resistance to such predatory attacks ; and they, at any rate, have been preserved. 
The agitation to which the body must have been subject in its course down the 
stream, and before it finally sunk and settled out of sight, would be attended, after 
a certain amount of decomposition of the flesh, ligaments, and other soft parts, 
with such an amount of dislocation as the ribs and other parts of the vertebral 
column exhibit along the otherwise well-preserved and completely consecutive 
series of the bony segments, from the skull to near the end of the tail. But tlie 
oblique compression of the skull, the flattening of the thorax, squeezed between 
the approximated piers of the scapular arch, attended with fracture of one of the 
coracoids, and other indications in the rest of the trunk, plainly bespeak the 
enormous pressure to which the fossil has been subject after its imbedding, and 
which must have been attended with still more injury and destructive obliteration 
of anatomical characters had it not been for the surrounding uniform support 
afforded by the matrix, compactly hardened around the petrified skeleton before 
those cosmical movements commenced to which the change in the position of the 
old Liassic sea-bottom has been due. 
