210 Report on the Geology, Zoology, $c. [No. 135. 



which we must do, as the observations are based upon incontrovertible 

 data, we are not to admit that if we find strata connected with a parti- 

 cular system, and occupying the same position as they do in Europe and 

 elsewhere, and composed of the same rocks, that they, because their 

 organic remains differ, are not of contemporaneous formation. Thus 

 for instance in the limestone rock, which we consider as the equiva- 

 lent of the mijschelkalk, we meet with a coral nearly allied to the 

 Eunomia radiata, a fossil met with in the oolite. Agassiz, an autho- 

 rity of the highest order, has asserted, that no species occur in two 

 geological formations, or even in two different parts of one formation ; 

 and he says, that he has come to this conclusion, not only from 

 an examination of the species of Trigonia, but that it has been 

 confirmed by his examination of fossil fishes and echinodermata.* His 

 statement, based upon ample researches, and a profound knowledge 

 of the subjects investigated, will go far to check that rage which 

 now exists among geologists, of identifying species found in different 

 parts of a formation with each other ; but we agree with Brown, that 

 there are species which pass from one subdivision of a formation to 

 the other, and even from one formation into another. Agassiz, to throw 

 aside all observations which have been made by his predecessors, 

 asserts, that no so-termed character — that is, no observable mark — can 

 be so striking as to indicate an absolute specific distinction ; but at the 

 same time it should never be regarded so trifling as to point to absolute 

 identity ; that characters do not mark off species, but that the combined 

 relations to the external world in all circumstances do.f How are 

 varieties to be distinguished ? Is the influence of the relations of the 

 external world uniform ? Undoubtedly not, and as Brown says, many 

 of the distinctions adhering to individuals are the mere result of such 

 an influence, or in other words, Agassiz wishes to prove, that until the 

 geognostical and geological relations are examined, the species cannot 

 be determined, following an extreme course in opposition to those 

 fossil geologists who maintain, that by an examination of a few fossils, 

 they can tell the age of any deposits. 



Many of the fossils met with in the limestone which we consider 

 as the equivalent of the muschelkalk, are nearly allied to those met 



* Edinb. New Phil. Journ. No. 63, page 97. 

 f Edinb. New Phil. Journal, No. 63, p. 97. 



