ANIMALS DKSTROVEn SUDDENLY. 
122 
lation of certain strata, accompanied by the 
sudden destruction, not only of testacea, but also 
of the higher classes of the then existing inhabi' 
tants of the seas. We have analogous instances 
of sudden destruction operating locally at the 
present time, in the case of fishes that perish froio 
an excessive admixture of mud with the water ol 
the sea, during extraordinary tempests ; and also 
from the sudden imparting of heat, and noxious 
gases, to water in immediate contact with the 
site of submarine volcanoes. A sudden irrup' 
tion of salt water into lakes or estuaries, pre' 
viously occupied by fresh water, or the suddeU 
occupation of a portion of the sea, by u*’ 
immense body of freshwater from a burstiUt? 
lake, or unusual land flood, is often fatal to large 
numbers of the inhabitants of the waters the® 
respectively interchanged.* 
The greater number of fossil fishes present ue 
appearance of having perished by mechanic^* 
violence ; they seem rather to have been deS' 
troyed by some noxious qualities imparted 1^* 
the waters in which they moved ; either by 
sudden change of temperature,! or an adini^' 
• tb® 
* See account of the effects of an irruption of the sea into 
freshwater of the lake of Lowestoffe, on the coast of Suffo 
Edinburgh Philosophical Journal, No. 25, p. 372. 
tb^ 
t M. Agassiz has observed that a sudden depression to 
amount of 15“ of the temperature of the water in the river G 
which falls into the lake of Zurich, caused the immediate 
of thousands of Barbel. 
