Art. VIII.— Paleoiitolog^ical Papers No. 10: Condi- 

 tioiis of Preservation of Invertebrate Fossils. 



By C. A. White, M. D. 



During the prosecution of his field-work, the paleontologist often ob- 

 serves certain interesting relations, not only between the lithological 

 character and composition of the different kinds of fossiliferous rocks 

 and the condition in which their contained fossils are preserved, but 

 also between the lithological composition of those strata and the fauual 

 characteristics of their fossils. In the latter instances, the case is largely 

 one of original character and condition of the sea-bottom sediments as 

 the ground of the habitat of those animals, while they were living, whose 

 fossil remains they as rockj^ strata now inclose. It is proposed to make 

 this latter subject the basis of a future paper, but the present one will 

 be devoted to a discussion of some of the conditions of fossilization and 

 preservation of invertebrate remains as they are found in the various 

 kinds of stratified rocks of the different geological ages, and to institute 

 some comi^arison of their mineral composition as fossils with that which 

 they possessed in the living state, assuming that of the latter by the 

 known composition of their present living representatives. It would 

 add greatly to the interest and scope of this subject if a series of careful 

 chemical analyses of these substances, both fossil and recent, could form 

 a part of the basis of its discussion, but no opportunity has yet occurred 

 for accomplishing such a task. Although detailed chemical analyses do 

 not enter into the data for these discussions, a consideration of the min- 

 eral composition of the fossil remains as they now exist, and a compari- 

 son of that composition with what it was in the living state, necessarily 

 forms the basis of a considerable part of the present i)aper. Such com- 

 parisons, while they show a close similarity in a very large i^roportion 

 of cases, always exhibit at least some degree of contrast; and in some 

 cases, a total change of mineral composition is found to have taken i)lace. 

 Many of the facts herein stated are patent to every collector of fossils,, 

 but the subject to which they relate is seldom discussed in paleontological 

 writings, and the few references that are made to it are usually of a 

 special or local character. Therefore in view of the somewhat extended 

 field observations of the writer in the median portion of ISTorth America, 

 it has been thought advisable to embody some general observations upon 

 this subject in the present pajjer. 



In a general way we may divide the substances which in life consti- 

 tuted the skeletal i^arts of invertebrate animals, which parts alone have 



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