The Edinburgh New Philosophical Journal. 259 



" We can no longer affirm, with M. Agassiz, that Fitzinger has done 

 wrong in separating Cyprinus from Cobitis. We shall not here discuss 

 the reasons which determined the latter to effect this separation, but 

 it is certain that the microscopic inspection of the scales justifies it 

 completely, and that this difference alone authorizes a distinction to 

 be made between these two genera. 



" We shall not say more in this place in confirmation of our opinion. 

 The examples adduced already demonstrate sufficiently, that the detail- 

 ed study of scales by the aid of the microscope, can alone reveal their 

 forms. Of this we find a convincing proof in the incomplete results 

 M. Agassiz obtained by studying them with the naked eye. His vast 

 knowledge, and the care with which he conducted his researches, could 

 not compensate for the insufficiency of his means of observation. 



" Another question here arises ; how far can the scales afford marks of 

 distinction between species, genera, and families ? It will be readily 

 understood, that the detailed and continued study of a great num- 

 ber of well preserved individuals, can alone decide this. It may 

 even be found that the same form reappears in different families, and 

 that the other characters must concur in effecting a classification, in the 

 same manner as the same form of crystallization recurs in minerals 

 altogether different. Hitherto, we have found the forms very distinct 

 and characteristic in each family. If we have not been able to prose- 

 cute our researches to the distinction of genera and species, it is for 

 want of a sufficient number of individuals ; at the same time we do not 

 believe that we will require to renounce the attempt altogether. Our 

 ulterior observations will throw light on this subject. Meanwhile we 

 have been able to establish differences between families, whose scales 

 M. Agassiz considered identical, as has been proved in the preceding 

 pages." 



The following observations on Microscopic Animals in 

 Cretaceous Rocks, by Professor Ehrenberg, we give entire. 



On the Calcareous and Siliceous Microscopic Animals which form the chief 

 component parts of Cretaceous Rocks. By Professor C. G. Ehrenberg.* 



" In the year 1836, the author communicated to the Academy, that, in 

 the course of his examination of chalk and other limestones, he had 

 found a characteristic feature in the smallest grains of chalk, which, if 

 not identical with, was very similar to crystallisation, and consisted 



* From the Reports of the Royal Prussian Academy. Translated from PoggendorlF's 

 Annalen, 1839, No. 7. 



2m 



