370 PETRIFACTIONS AND THEIR TEACHINGS. CHAP. IV. 



cal preparations. Reflecting on the circumstance that the 

 Enaliosaurians lived in an ocean which swarmed with pre- 

 daceous fishes and other animals, and that both genera were 

 carnivorous, and doubtless preyed on the young and the 

 feeble of their own races, it seems difficult to account for the 

 great number of entire carcasses that must have been buried 

 in the mud at the bottom of the sea, and left unmolested on 

 the spot where they died and became imbedded. 



In explanation of this fact, Dr. Buckland has suggested the 

 probability that these creatures experienced a sudden death, 

 from a diffusion of tnephitic vapours through the water, by a 

 submarine volcanic eruption ; such a phenomenon, it is in- 

 ferred, would account for the destruction of shoals of those 

 reptiles that were within the reach of the gaseous influence, 

 and at the same time prevent the approach of any predaceous 

 animals, till the carcasses were enveloped in the mud, and 

 placed beyond the reach of assailants. 



In connexion with the facts referred to, it is worthy of 

 remark that the Ichthyosauri are, for the most part, found 

 lying on the side, while the Plesiosauri are extended on their 

 backs, with the abdominal region uppermost, as in the 

 splendid fossil figured in Lign. 73. It has been very in- 

 geniously conjectured by Mr. Samuel Stuchbury,' that this 

 difference of position is referable to the form and structure 

 of the animals of the two genera. In the case of the Ple- 

 siosauri it is assumed, that after death, the gases evolved by 

 putrefaction from the abdominal viscera, were retained by 

 the tough dermal integuments and the sterno-costal arcs, and 

 the body was thus suspended with the belly uppermost, till 

 it became water-logged, and buried in the silt. Whereas the 

 fish-like form of the Ichthyosauri, the vertical diameter of 

 the body being greater than the lateral, is presumed to ac- 

 count for the lateral position of the fossil skeletons ; while 

 the frequently dislocated state of the bones is supposed to 

 have resulted from the strong integuments of the body 

 having remained entire, until the internal parts were decom- 



1 " Description of a new species of Plesiosaurus (P. megacephalus), in 

 the Museum of the Bristol Institution." By Samuel Stuchbury, Esq. 

 F.G.S. " Geolog. Journal," vol. ii. 1846, p. 411. 



