904 The American Naturalist. [November, 
neighborhood of Neu Braunfels, Exogyras and Gryphaeas, are 
thickly strown over the ground, disengaged by sub-aerial 
weathering and surface waters from their enclosing marls (F. 
Roemer, Kreidebildungen von Texas, etc., p. 14, et seq.). 
Indeed, under some circumstances inhumation quickly destroys 
fossil remains from the acidic qualities of the soil, as in the 
neighborhood of Cumanacoa, Venezuela, S. A., as reported by 
Humboldt? (Travels in Equinoctial Regions of America, Vol. 
I, p. 228, Bohn’s Edit.), and we think that, in many instances, 
fossils have undergone silicification more rapidly when brought 
under surface conditions where exposed to mineral waters, 
than they would have if covered in completely, and so re- 
moved from the influences of terrestrial circulation.’ 
Yet the word fossil is, of course, a distinct reference to a crea- 
ture living in the past, and, as such, very properly implies en- 
tombment of some sort, and, as a fact, fossils are generally 
embedded in rocks or alluvial and diluvial beds, in clay banks 
or thinly aggregated beach sands. They may be subsequently 
exposed by weathering and by removal, but they indicate some 
sort of initial burial. Their chronological significance indi- 
cating the successive phases of animal life in geological time 
implies a stage-like superimposition with the earliest fossils at 
the bottom and the latest at the top. As, in fact, such super- 
imposition is only partially, and then locally, perfect—no sec- 
tion of the earth’s surface revealing a sheer and consecutive 
ascension of all the known strata, containing fossils—we con- 
stantly find the fossil-bearing rocks forming the surface of wide 
2 Dr. Schwernfurth, in his “Heart of Africa,” mentions a soil in which the 
natives bury their drums, stouls, ete., “to give them a permanent. blackness.” 
The vegetable acids developed by decomposition in such areas would act more or 
less corrosively on bone. Mr. J. Richardson tells me that in one year the entire 
carcass of a cat buried in rich soil had completely disappeared. On the other 
hand, “the fossil bones of the megatherium of the elephant and of the mastodon, 
which travelers have brought from S. A., have all been found in the light soil of 
the valleys and table-lands.”” Humboldt. 
3 Dr. Otto Kuntze (Nature, Vol. 19, p. 314) has insisted that his observations 
show that silicified trunks of trees “originate only in air; the siliceous water rises 
by capillary attraction in the stem, but only on the outside of the trunk does the- 
siliceous solution become solid by drying in the air; from the outside the silicifi- 
cation of the wood cells enters very slowly to the inner part,” 
