

- Boor V.] BURIAL OF ORGANISMS. : 605 
and, so to say, exceptional. They are supplied only where organic 
remains can be protected from air and superficial decay. Hence 
they may be observed in 
a. Lakes——Over the floor of a lake deposits of silt, peat, marl, 
&e., are formed. Into these the trunks, branches, leaves, flowers, 
fruits, or seeds of plants from the neighbouring land may be carried, 
together with the bodies of vertebrates, birds, and insects. An 
occasional storm may blow the lighter debris of the woodlands into 
the water. Such portions of the wreck as_are not washed ashore 
again may sink to the bottom, where they will for the most part 
probably rot away, so that, in the end, only a very small fraction 
of the whole vegetable matter cast over the lake by the wind is 
covered up and preserved at the bottom. In like manner the remains 
of yolant and wild animals swept by winds or by river floods into 
the lake run so many risks of dissolution that only a proportion of 
them, and probably merely a small proportion, would be preserved. 
When we consider these chances against the conservation of the 
vegetable and animal life of the land, we must admit that, at the 
best, lake-bottoms can contain but a meagre and imperfect re- 
ae of the abundant life of the adjacent hills and plains. 
akes, however, have a distinct flora and fauna of their own. Their 
aquatic plants may be entombed in the gathering deposits of the 
bottom. Their molluscs, of characteristic types, sometimes form, by 
the accumulation of their remains, sheets of soft calcareous marl 
(p. 463) in which many of the undecayed shells are preserved. Their 
fishes, likewise distinctly lacustrine, no doubt must often be entombed 
in the silt or marl. 
b. Peat-mosses.—Wild animals venturing on the more treacherous 
watery parts of peat-bogs are sometimes engulfed or “laired.” The 
antiseptic qualities of the peat preserve their remains from decay. 
Hence from European peat-mosses numerous remains of deer and 
oxen have been exhumed. LEvidently the larger beasts of the forest 
ought chiefly to be looked for in these localities (p. 460). 
c. Deltas at River Mouths—It is obvious that to some extent 
both the flora and the fauna of the land may be buried among the 
sand and silt of deltas (p. 388). But though occasional or frequent 
river-fioods sweep down trees, herbage, and the bodies of land 
animals, the careases so transported run every risk of having their 
bones separated and dispersed, or of decaying or being otherwise 
destroyed while still afloat, while even if they reach the bottom they 
tend to dissolution there unless speedily covered up and protected 
by fresh sediment. Delta formations can scarcely be expected to 
preserve more than a meagre outline of the varied terrestrial flora 
and fauna. 
d. Caverns.—These are eminently adapted for the preservation of 
the higher forms of terrestrial life (p. 355). Most of our knowledge 
of the prehistoric mammalian fauna of Europe is derived from what 
has been disinterred from bone-caves. As these recesses lie for the 
