Sharks of the Clcz'claiid Slmlc. — Dean. 275 
form. Here, in general, the striae are one-third, or thereabouts, 
less numerous. And I am accordingly inclined to believe, even 
taking into account the possibilities of the relaxed condition of 
the fibres, and of artifacts due to fossilization, that the ancient 
shark had not yet attained the high degree of muscular 
specialization of its modern kindred. This conclusion is 
materially strengthened by our knowledge of other primitive 
characters of cladodonts. (For summary v. Natural Science, 
1896, vol. viii, pp. 247-253.) 
Regarding now the process of the mineralization of such 
delicate structures as muscle fibres, interesting in a somewhat 
wider aspect paleontologically, Reis has written in consider- 
able detail. '■'• He finds that in lithographic stone fossils (and 
this will hold in a general way — t. Lankester anil others — in 
the case of similar fossils from other rocks) the muscular 
masj is purely mineral, composed largely (8o7o) of calcium 
phosphate. On various grounds he concludes that the muscular 
tissue could have been but in a semi-decomposed condition 
(halbfaulen Zustand), that mineralization took place relatively 
quickly, and that the object must have been so completely and 
thickly enclosed as to prevent further disintegration. Unlike 
Owen, Reis maintains, — in this point, justly, it seems to me,^ 
that the fossilization could not have been a part of or a sequel 
to a process of adipocere-making. He further concludes that 
the phosphate is derived from the body itself, product mainly 
of muscles and blood, precipitated when the decomposing ma- 
terial is brought in contact with the lime carbonate of the sedi- 
ment of the sea bottom. As the petrified muscle has more- 
phosphate in it than the recent tissue it follows, he maintains,, 
that it has received the phosphate from the remaining" muscles,, 
and these, therefore, have not been preserved. In any event, 
final decomposition of such an organism takes place much 
more slowdy in the deep sea than one is apt to believe, and there 
is thus a better chance for the gradual mineralization of 
tissues /'. e., by precipitation of lime. 
The foregoing explanation covers^ the matter of delicate 
fossilization ingeniously, and in some ways (Satisfactorily. But 
in other regards it is, I think, open to serious objections. For, 
*89 Ueber eine Art Fossilisation der Musculatur. SB. GeseU. Morph. 
Munchen, W. 6. 
