1897.] Fossils and Fossilization. 25 
members of the surrounding marine fauna. In this connec- 
tion the important observation recorded in Lyell’s Principles 
(Vol. II, p. 583), that upon the north coast of Ireland—the 
Rockhall Bank—“ a bed of fish bones was observed extending 
for two miles along the bottom of the sea in ten and ninety 
fathoms of water,” is of interest. Lyell,in the same place, also 
speaks of fish bones occurring in extraordinary profusion east- 
ward of the Faroe Islands. This “bone bed” was three miles 
and a halfin length and forty-five fathoms under water, and 
contained a few shells intermingled with the bones. 
In the cranial plates of Acanthaspis pustulosus, one of the fishes 
of the Devonian of Ohio, the space between the outer hard bony 
walls are filled with carbonate of lime which has infiltrated 
and consolidated the intra-mural cellular tissue, while the 
clavicle of Onychodus sigmoides presents internally a granulated 
area of carbonate of lime similarly formed and Prof. Claypole 
speaks of the second layer of the shield of his placoderm fish 
from the Upper Silurian of Pennsylvania as having its cells 
“ filled with infiltrated calcareous matter which, under the ac- 
tion of the weather, is dissolved out, leaving an exceedingly 
brittle cellular mass to represent the original shield”. These 
bones probably retain their phosphate of lime, since fish bones 
and teeth in the Old Red Sandstone in Lievland (?) according 
to Bischoff, have lost but very little of the original percentage 
of this salt. 
It must, however, be remembered that normal calcium 
phosphate is soluble in ammoniacal salts, sodium nitrate, com- 
mon salt and other salts; that its abstraction from buried 
bone may be quite rapid, and the cavities left by its absorption 
may become filled with mineral matter. An exchange may 
be effected between carbonates of alkalies and the phosphates 
in bone by which carbonate of lime remains and the phos- 
phoric acid is removed, and solution may be effected by aque- 
ous carbonic acid alone. The turtles of the Miocene of Ne- 
braska, which are so numerous, are represented by their joined 
carapaces and plastrons, and these are filled with the porous 
marl or earthy limestone of the White River beds. The bone 
of these parts presents a finely reticulated structure, and 
