The Lithosphere 



their own which differentiate them from the other 

 members of the family. 



The groups are called genera and the individuals 

 species. Thus the generic name of the cat family is 

 Felis y while its different members, such as the lion and 

 the tiger, are designated Felis leo, Felis tigris, and so on. 



In many instances both the generic and specific 

 names are descriptive of the animal, but in others they 

 indicate the place from which they came, the geological 

 formation in which they are found, or the name of their 

 discoverer. As an example of a descriptive name we 

 may take Pterinopecten papyraceus, a bivalve shell which 

 is found as a fossil in the Coal Measures. Pterinopecten 

 means the winged comb shell, and papyraceus indicates 

 the fact that it is paper-like, the rock in which it occurs 

 containing so many shells that it splits up like sheets of 

 paper. 



The science of palaeontology, which deals with the 

 classification and evolution of fossils, is too vast a subject 

 to be treated of in the present volume, and the various 

 fossils mentioned in the succeeding chapters may be 

 looked upon merely as indicators of the geological 

 formations in which they are found. They are all of 

 common occurrence, and will be found figured or described 

 in any text-book of general geology. 



Armed now with the Doctrine of Uniformity and 

 Smith's principle that " rocks may be identified by their 

 fossil contents," let us take the advice of Petrus Severinus, 

 who in 1571 addressed the thinkers of his day as 

 follows : " Buy yourselves stout shoes, get away to the 

 mountains, search the valleys, the deserts, the shores of 

 the sea, and the deepest recesses of the Earth ; mark 



