2/6 The American Geologist. November. 1902 
in the first place, it presupposes a sufficient decomposition of 
the tissue to warrant its giving up its phosphate component, a 
chemical condition which, it seems to me, predicates a breaking 
down of the fibres, certainly to the degree of their losing their 
delicate striation. And we know, on the contrary, that the fibre 
structures were not decomposed, for they are reproduced in an 
amazingly perfect way. Nor can we, I believe, assume that, 
if precipitated from neighboring decomposed tissue the lime 
phosphate will be transferred bodily into the fresher fibres in 
so perfect a way as to preserve their minute details. On the 
other hand I cannot feel that it is necessary to assume that all 
of the lime phosphate was derived from the animal fossilized 
as a product of its decomposition, or that even a goodly part 
of the phosphate was thus deposited ; it is a simpler interpreta- 
tion that it came in solution from foreign sources. For in 
this way we can best understand how a tissue in a fairly fresh 
condition can be mineralized, the fibres themselves absorbing 
the dissolved phosphate in their neighborhood, accumulating 
it very much as fluorides are taken up by fossil bones, or as lime 
carbonate is accumulated by bone when placed in running 
water, conditions to which Reis himself refers. Moreover, 
from what we know of the formation of phosphates, i. e., in the 
river mouths of South Carolina, we have reason to believe that 
this material is peculiarly apt to accumulate, and that with this 
process is a phosphatizing of organic remains. Thus 
an object which ha;S normally but a small amount of phosphate 
becomes transformed, often with great histological delicacy, 
into a fossil made up largely (over 90;^) of calcium phosphate. 
This instance, however, is an extreme one, dealing, as it does, 
with a mineralizing process which extends over kilometers of 
river bottom ; simpler is the case of the present sharks in as 
much as the phosphatizing of tissue occurred in a tract whose 
area measures but a few centimeters, and whose thickness is less 
than a millemeter. Moreover, from the quantity of the fossil 
tissue preserved, we know that it is in nearly every case but a 
scale-like portion, or, better, a delicate crust of the body wall 
which has been preserved, a feature which tells, I think, in 
favor of the present interpretation. In this regard it follows 
also that the fresher the tissue to be fossilized, the better are 
its chances for accumulating phosphate : for it remains for a 
