Book V.| BURIAL OF ORGANISMS. 607 
~ more than a mere fraction of the whole assemblage of life in these 
juxta-terrestrial parts of the ocean. In proportion to distance from 
land the rate of deposition of sediment on the sea-floor must become 
feebler, until in the remote central abysses it reaches a hardly 
appreciable minimum, while at the same time the solution of 
calcareous organisms by carbonic acid may become marked in deep 
water. Except, therefore, where organic deposits, such as-ooze, are 
forming in these more pelagic regions, the conditions must be on the 
whole unfavourable for the preservation of any adequate represen- 
tation of the deep-sea fauna. Hard enduring objects, such as teeth 
and bones, may slowly accumulate and be protected by a coating of 
peroxide of manganese, or of silicates, such as are now forming here 
and there over the deep-sea-bottom. Yet a deposit of this nature, if 
raised into land, would supply but a meagre picture of the life of 
the sea. 
In considering the various conditions under which marine organisms 
may be entombed and preserved, we must take into account certain 
occasional phenomena, when sudden or at least rapid and extensive de- 
struction of the fauna of the sea may be caused. LHarthquake shocks 
have been followed by the washing ashore of vast quantities of dead 
fish, and no doubt submarine volcanic eruptions must likewise be 
destructive to the denizens of the sea-bottom. Violent storms, by 
driving shoals of fishes into shallow water and against rocks, produce 
enormous destruction. Dr. Leith Adams describes the coast of part of 
the Bay of Fundy as being covered to a depth of a foot in some places 
with dead fish dashed ashore by a storm on the 24th of September, 
1867.1 Copious discharges of fresh water into the sea have been observed 
to cause extensive mortality among marine organisms. Thus, during 
the S.W. monsoon and accompanying heavy rains, the west coasts 
of some parts of India are covered with dead fish thrown ashore from the 
sea.2_ Hiven a sudden irruption from the outer sea into a sheltered and 
partially brackish inlet may cause the extinction of many of the 
denizens of the latter, though a few may be able to survive the altered 
conditions.* Such phenomena offer explanations of the probable causes 
of death in the case of fossil fishes, whose remains are sometimes 
crowded together in various geological formations. 
Of the whole sea-floor the area best adapted for preserving a 
varied suite of marine organic exuvie is obviously that belt which, 
running along the margin of the land, is ever receiving fresh layers 
of sediment transported by rivers and currents from the adjacent 
shores. The most favourable conditions for the accumulation of a 
thick mass of marine fossiliferous strata will arise when the area of 
deposit is undergoing a gradual subsidence. If the rate of depression 
and that of deposit be equal, or nearly so, the movement may pro- 
ceed for a vast period without producing any great apparent change 
1 Q. J. Geol. Soc. xxix. p. 303. 
2 Denison, Op. ett. xviii. p. 453. 
3 Forchhammer, Edin. New. Phil. Journ. xxxi. p. 69. Large numbers of salmon 
sometimes die in pools of a river during dry and hot weather. 
