270 



/. CULVER HARTZELL 



We find the same organisms preserved in all manner of conditions, 

 and only by a careful comparative study of the exterior and interior 

 markings are misinterpretations to be avoided. 



Fossils of the same species have been referred to different species, 

 and the same genera to different genera. For example, Miche- 

 linia clappii, Hall,' was misinterpreted by Edwards and Haime, 

 and referred to ChonostegUes clappii^ and also to Emmonsia ( ?) 



cylindrica,^ and by 

 Billings to Haimeophyl- 

 lum ordinatum^ and also 

 to Michelinia intermit- 

 tens.^ (See Figs, i, 2, 

 3. 4, S, 6, 7.) This 

 misinterpretation was 

 due to the peculiar 

 ways in which this 

 genus occurs. At times 

 the walls are coated 

 with silica, and then 

 filled in with calcite. 

 At times only the silice- 

 ous coatings are left, which give a mold of the inner walls. Then 

 again we find that they were filled with calcite, the walls having 

 disappeared; and in this case we have a solid mold instead of a 

 hollow one. At times the form is partly destroyed, leaving molds, 

 casts, and parts of the original in the same specimen. 



We find fossils of the same species preserved {a) in their original 

 condition, (&) as casts, and (c) as molds. In regard to the first 

 condition little difficulty will present itself. The second and third, 

 however, may lead to confusion, for they may not exhibit the exter- 

 nal form. 



Fig. I. — Chonostegites clappi 

 and Haime.) 



(After Edwards 



I Hall, Geology of the State of New York (1876), "Illustrations of Devonian 

 Fossils," Plate XVII. 



= Edwards and Haime, Pal. Eos. d. Ten. Pal. (1851), p. 299, Plate XIV.Eigs. 4, 4a. 



3 Ibid. 



4Bimngs, Can. Jour. U. S., Vol. IV (1859), p. 139. 



5 Ibid., p. 113. 



