30 ANNUAL REPORT OF 



Probably everyone has some notion of what is meant by the 

 term fossil. Strictly defined, fossils include the remains or traces 

 of plants and animals that have lived during former periods of 

 the earth's history, and whose remains or other indications have 

 become preserved in the rocks. By the process of petrifaction, as 

 it is called, the hard parts of animal bodies, such as the shelly cov- 

 ering of mollusks, crustaceans, echinoderms (sea-urchins, star- 

 fish, etc. ) , or the internal skeleton of vertebrates, become replaced 

 by mineral matter, all organic substances being converted into 

 stone. Horney chitinous tissue undergoes a similar process ; and 

 certain other substances, such as vegetable matter, feathers, and 

 in rare instances animal integument, become carbonized. But 

 almost invariably the soft parts of dead bodies suffer decomposi- 

 tion either before or after burial in the preserving medium, thus 

 leaving no traces in the rocks. It is only under exceptionally 

 favorable circumstances that muscular fibre, dermal coverings, 

 cartilage, or internal organs (such as the swim-bladder, walls 

 of the intestinal canal, or egg-cases of cartilaginous fishes) have 

 been preserved in recognizable condition. Nevertheless, con- 

 ditions have sometimes permitted even the most delicate struc- 

 tures, such as insects' wings and impressions of jelly-fishes, to 

 become retained in the soft mud, which afterwards became 

 solidified. Localities famous the world over for the beauty and 

 delicacy of their fossil remains are the lithographic stone quarries 

 of Bavaria and the department of Ain, France. An inquiry into 

 the conditions under which these deposits were laid down sug- 

 gests with much plausibility that they represent filled-in lagoons 

 of coral atolls. 



It is worthy of remark that any investigation of fossil faunas 

 takes into account all questions relating to the environment of 

 the forms represented, the climatal and geographic conditions 

 amidst which they flourished, their food, habits, migration, and 

 genetic relations to other species. In a word, we have not only 

 to* consider the nature of organic remains which have become 

 preserved in the fossil state, but must also reconstruct as ac- 

 curately as possible the conditions that were operative during 

 their lifetime, approaching them in the same manner as we would 

 organisms of the present day. There is, therefore, no' essential 



