Sharks of the Cleveland Shale. — Dean. 277 
longer time passive and the osmotic changes^ can better be felt 
in even its minutest texture. During- decomposition, on the 
other hand, the petrifying tissue would have broken down, 
first in its cytoplasmic structures, later in its membranes, 
through processes whose energetic operation could hardly have 
been favorable for the depositing of accurate casts, or for the 
action of continuous and unaltered osmosis. In the present 
specimens one also notes that the phosphatizing of the 
muscles occurs only at favorable points of the fish's body and 
only on one side of the body, judging in the latter regard 
from sections. This fossilized region I am led to identify as 
that portion of the animal which was in closest contact with 
tiie phosphatizing sediment. For if a solution containing such 
a sediment be prepared artificially and recent tissue introduced, 
the latter is found to lie on the surface of the sediment, and, 
decomposing, leave a crust where its mass has been in closest 
contact. 
As far as Reis's further conclusions go, one can, I thinlc, 
safely agree with him regarding the matter of slowness of 
decomposition under conditions of marine deposits, fide, re- 
cently,the results of the Siboga expedition ; indeed, even in 
shallow water, recalling Moseley's experiments, disintegration 
may take place slowly enough to enable a delicate object to 
become saturated with phosphate if placed under suitable con- 
ditions, a circumstance to be borne in mind in the case of the 
Cleveland shale, which as probably not a deep water deposit. 
We can also reasonably conclude with Reis that the muscular 
tissue mineralized relatively quickly. 
The foregoing considerations, it seems to me, add an item 
or two to oru- knowledge of the primitive status of the Cleve- 
land shale. From evidence contributed by Newberry and 
others it has been regarded as an estuary deposit ; add to this 
now a condition which caused its vertebrate reinains to become 
delicately phosphatized, and we picture it as a sediment 
similar to that which was deposited in the early tertiary 
in the river-fed estuaries of South Carolina. If again, the 
phosphatizing of the muscular tissue took place at or near 
the surface of the bottom-sediment, as I think there is good 
reason to conclude, we have an interesting note as to the 
consistency of the sediment, for it was then soft enough 
