Wiuchell.] Z*^^ [May(i, 



&c. So the Cornifei'ous limestone holds several species which never fail 

 to declare its identity; and the Hamilton group is traced by persistent and 

 unmistakeable paleontological characters over an area tvs^o thousand 

 miles in breadth — from eastern Nevs^ York to the Rocky Mountains, and 

 from Central Kentucky to the valley of Mackenzie's river. It is incredi- 

 ble that the fauna of the Chemung sandstones, vrithout visible change in 

 physical conditions, should have undergone a total transmutation in a dis- 

 tance less than 200 miles. Were the lithological characters of the Che- 

 mung and Marshall remarkably distinct, we should expect a marked va- 

 riation in the faunas, even if contemporaneous. But we should still 

 have detected a few identical species, and a strong correspondence in 

 dominant ideas — as the Edmondias, Aviculopectens and Producti, of the 

 Chouteau limestone, are identical Avith the same genera and species of the 

 Marshall sandstone. In some portion of the hundreds of thousands of 

 square miles over which the Marshall strata have been 'extended, would 

 have existed physical conditions sufficiently similar to those of New York, 

 to have permitted the introduction of a few of the types which are domi- 

 nant at the East. 



The facts which I have already pointed out demonstrate that there was 

 a time when the fauna of Ohio and Michigan had a representation in New 

 York and Pennsylvania. Fossils even from Iowa and Missouri — fossils 

 from fine, and even from calcareous strata — have been identified in west- 

 ern New York, identified, too, in conglomeritic deposits. It is even true, 

 as de Verneuil asserts, that there is a law, however inscrutable, which 

 stamps a common and recognizable impress upon faunas of the saine age, 

 however diverse the physical conditions imder which they subsist. 



The doctrine of faunal collocations of organic beings is founded in 

 Nature, and has been made a specialty by one whose name commands 

 universal respect. We must apply this doctrine to the distribution of 

 extinct animals. It seems to me, however, there is a possibility of using 

 this doctrine as "a hobby," and of carrying it to unwarranted limits. 

 Thinking has its fashions no less than architecture and dress. Another 

 fashion of our times is to reunite varieties and species of organic remains, 

 which have been discriminated often with much study and gi-eat utility. 

 It is the fashion just now to concede a wide range to the variability of 

 species. Both these fashions tend to a relaxation of the rigor of the limits 

 which we had set to the inflasncs of external agencies. It seems to me 

 that the true philosophy leads to the practice of a judicious conserva- 

 tism in reference to the long-accepted canons of paleontological science ^ 



For these reasons I cannot, at present, consent to the parallelizing of 

 the Chemung and Marshall groups. 



VIII. Parallelism of the Catskill and Marshall. 



If the Chemung be not the eastern representative of the Marshall, 



where, it may be asked, does that representative exist ? It would be no 



reply to the argument which I have presented, if no representation of the 



Marshall were yet discovered east of Ohio. The case would not be with- 



