16 ANIMALS OF THE PAST 



soft mud. For just as a plaster cast boiled in oil becomes 

 thereby denser and more durable, so the oily and other 

 matter coming from decomposing fish operated on the 

 surrounding sand or mud so as to make it more com- 

 pact." 



It may not be easy to explain how it came to pass that 

 fishes dwelling in salt water, as these undoubtedly did, 

 were thus deposited in great numbers, but we may now 

 and then see how deposits of fresh-water fishes may have 

 been formed. When rivers flowing through a stretch of 

 level country are swollen during the spring floods, they 

 overflow their banks, often carrying along la,rge numbers 

 of fishes. As the water subsides these may be caught in 

 shallow pools that soon dry up, leaving the fishes to 

 perish, and every year the Illinois game association 

 rescues from the "back waters" quantities of bass that 

 would otherwise be lost. Mr. F. S. Webster has 

 recorded an instance that came under his observation in 

 Texas, where thousands of gar pikes, trapped in a lake 

 formed by an overflow of the Rio Grande, had been, by 

 the drying up of this lake, penned into a pool about 

 seventy-five feet long by twenty-five feet wide. The 

 fish were literally packed together like sardines, layer 

 upon layer, and a shot fired into the pool would set 

 the entire mass in motion, the larger gars as they 

 dashed about casting the smaller fry into the air, a 

 score at a time. Mr. Webster estimates that there must 

 have been not less than 700 or 800 fish in the pool, from 

 a foot and a half up to seven feet in length, every one 

 of which perished a little later. In addition to the fish in 

 the pond, hundreds of those that had died previously 

 lay about in every direction, and one can readily im- 

 agine what a fish-bed this would have made had the 

 occurrence taken place in the past. 



