122 The Ottawa Naturalist. [Jan. 



regarded as only one of several objects to be attained through 

 the collection and study of fossils. The description of fossils 

 is in fact only the first step in their use for the purpose of corre- 

 lation in palaeogeography, attacking the far-reaching problems 

 of evolution. 



It is worth while recalling here that Wm. Smith, the father 

 of stratigraphic palaeontology, made excellent use of certain 

 fossils even before they were named in tracing the formations 

 which they characterized over a great part of England. 

 • Smith's discovery of the value of fossils in correlation enabled 

 him to prepare the first geological map of which we have any 

 record. The fundamental importance of fossils to the geologist 

 in enabling him to recognize or identify the same beds in dif- 

 ferent areas has been universally recognized since the days of 

 Wm. Smith. It is for this purpose that the fossil collections 

 of the field geologist are generally made. They necessarily 

 often represent a great many localities, and frequently a small 

 number of specimens from the individual localities which may 

 or may not be as large as the conditions incident to the work 

 will permit, and the preparation of stratigraphic sections in 

 connection with them is most important. 



Progress in stratigraphic palaeontology in recent years has 

 been largely along the Hne of increasing our knowledge of the 

 range and distribution of faunas, and of the individual species 

 composing them. The important bearing of this class of knowl- 

 edge upon questions concerning the evolution and dispersal of 

 faunas is evident. Its. interest to the general geologist Hes 

 chiefly in the fact that the accuracy with which fossils can be 

 used in correlation is in direct proportion to the completeness 

 of our knowledge of their range. The presence in certain areas 

 of recurrent faunas or faunas which re-appear at higher levels 

 after completely disappearing for a considerable interval from 

 a series of beds, sometimes introduces for particular regions a 

 new and difficult factor into the use of fossils in correlation 

 until the inter-relations of the recurrent with the associated 

 faunas has been worked out. Such areas require an amount 

 of collecting and careful comparison of faunas and sections 

 which would be unnecessary in ordinary regions. The recur- 

 rence in the Devonian section of southern New York of Tropi- 

 dolepins carinaius in the Chemung, 2,000 feet above its dis- 

 appearance at the top of the Hamilton formation, is an example 

 of this phenomenon.* (See fig. 2.) We learn from it and 

 similar examples that the disappearance of a fossil from a sec- 

 tion may not mean that it has become extinct, but that it has 

 changed its habitat. 



*E. M. Kindle. Jour. Geol., vol. XIX, pp. 346-347, 1911. 



