METHODS — PAL^ONTOLOGICAL 37 



River by breaking through the ice, when they attempted to 

 cross at times when the ice had not attained its winter thickness, 

 or was weakened by melting in the spring. No doubt, the bed 

 of that river contains innumerable bones of the Bison. Fre- 

 quently, too, animals are caught in quicksands and, unable 

 to escape, are buried in the soft mass ; fossil skeletons which 

 are preserved in sandstones in an erect or standing position 

 are usually to be interpreted in this manner. 



The sedimentary accumulations formed in lakes and ponds 

 sometimes yield fossil bones or skeletons in considerable 

 numbers, which have, for the most part, been derived from the 

 carcasses of animals carried into the lake by streams. A newly 

 drowned mammal sinks to the bottom and, if sufficient sediment 

 be quickly deposited upon it, it may be anchored there and 

 fossilized as a complete skeleton. Otherwise, when distended by 

 the gases of putrefaction, the body will rise and float on the 

 surface, where it will be attacked and pulled about by croco- 

 diles, fishes and other predaceous creatures. As the bones 

 are loosened in the course of decomposition, they will drop 

 to the bottom and be scattered, now here, now there, over a wide 

 area. 



Land mammals are rarely found in marine rocks, or such 

 deposits as were made on the sea-bottom ; but the remains 

 of marine mammals, whales, porpoises, dolphins, seals, etc. 

 are often found in large numbers. In principle, the method 

 of entombment is the same as in the case of lakes, but currents 

 may drift to some bay or cove multitudes of carcasses of these 

 marine mammals. At Antwerp, in Belgium, incredible quanti- 

 ties of such remains have been exposed in excavations and in 

 all probability were drifted by currents into a quiet and shal- 

 low bay, which was subsequently converted into land. 



While the foregoing account by no means exhausts the 

 various methods of accumulation and burial of the skeletons 

 and scattered bones of mammals, it covers the more important 

 of these methods sufficiently for a general understanding of 



