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 quarr) ing 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 the 

 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. 



