Shaler.] 414 [Dec. 7, 



result would necessarily be that friction would occur between the 

 floor and the overlying water. This would tend to stir up the in- 

 coherent material on the bottom of the sea and to make the water 

 unsuitable for the use of organic life. It is a well-known fact that 

 the greater portion of our marine animals are singularly intoler- 

 ant of muddy water, even if the quantity of dissolved mud be rel- 

 atively inconsiderable. The forms which normally live on mud 

 bottoms are to a great extent provided with contrivances which en- 

 able them to meet such accidents by peduncles or stems which lift 

 their bodies some distance above the floor, by siphons, or by shells 

 which may be closed during the period when they are subjected 

 to risks of this sort. In the deeper seas, these provisions do not 

 generally exist and the animals dwelling on the bottom are, there- 

 fore, very likely to be overwhelmed by such catastrophes. I am, 

 therefore, inclined to believe that the sudden terminations in the 

 organic contents of our layers, in stratified rocks formed on floors 

 in the deeper seas are to be in the main accounted for by the ac- 

 tion of earthquakes in stirring the mud. Some portion of the de- 

 structive influence may be exercised through the direct effect of the 

 shock itself. It is a well-known fact that an earthquake shock is 

 competent to destroy our fishes. The effect of jar on the inverte- 

 brate animals has never been investigated, but it seems not im- 

 probable that they too may be destroyed by such accidents. In 

 the case of fishes the destruction effected by earthquake shocks is 

 often extremely extensive, as has been noted by various observers. 

 Several bone-beds, composed of fish remains which occur at vari- 

 ous points in the geological section, may, perhaps, be explained 

 in this manner. It is difficult, indeed, in any other way to ac- 

 count for such a deposit of bones as that which occurs in the 

 Rhaetic deposits of Europe, where over an area of several hun- 

 dred thousand square miles we find a bone-bed at a particular level 

 which appears to indicate a widespread and simultaneous destruc- 

 tion of these forms. 



It is very desirable that we should secure a series of experi- 

 ments designed to determine the effect of explosive shocks on in- 

 vertebrated animals, but it is not necessary for our purpose, for 

 the reason, that the muddying of the water which would inevita- 

 bly result from a powerful shock will be quite sufficient to ac- 

 count for the destruction of organic forms which we seek to ex- 

 plain. Nearly every part of the sea bottom has considerable amount 



