CLAS3IFICATION. 21 



CHAPTER II 



CLASSIFICATION. 



If fossils were to be regarded as merely medals or tokens of geological 

 formations, to serve the purpose only of distinguishing tlie latter from each 

 other, a knowledge of their biological relations among themselves and to 

 existing forms would be unnecessary, and their classificatiou, beyond the 

 application of convenient names, a useless and cumbersome labor. As our 

 knowledge of paleontology increases, however, the great value and impor- 

 tance which the higher groups possess in the solution of geological problems, 

 not to mention their bearing upon purely biological subjects, are more and 

 more recognized. The custom that has been prevalent of recording only the 

 generic and specific names of the fossils described has long been felt by the best 

 paleontologists to be insufficient to give full expression to the significance they 

 possess. Consequently, a more or less complete zoological grouping of them 

 has of late become more common. There seems to be no rational ground 

 between a full classification on the one hand and the mere mention of the 

 name of each species in connection with its description on the other. I 

 have, therefore, compiled a full zoological classification of the collections 

 that form the basis of this report. In doing so, I have generally adopted 

 the system used by the best specialists in each department ; and their use 

 here is merely one of present convenience, and not necessarily an expi-ession 

 of full approval. For example, an obvious reason for the adoption of Dr. 

 Gill's arrangement of the fannlies of Mollusca may be found in the fact that 

 the collections by law go to the Smithsonian Institution, where that an-ange- 

 ment has been adopted for its cabinet. This should not be understood as 

 an expression of my own views as to the systematic position of the Brachio- 

 2)oda,anj more than the use of Edwards and Haime's classification of corals 

 implies an approval of the assignment of Chcetetes and related corals to the 

 Zoantliaria, &c. 



Following is a tabular view of the classification I have adopted for the 

 collections, repeated for each of the geological periods they represent. 



