Complete Fossil Fi»h Fauna. 35 



acquired the certainty that these calculations are much be- 

 low the reality. With regard to birds, Crustacea, insects, 

 echinoderms, and polypes, particular difficulties at this mo- 

 ment stand in the way of all kinds of comparison of this na- 

 ture. In relation to fossil infusoria, it would be premature 

 at present to make use of the labours of one man, continued 

 only for eight or nine years, in order to estimate the profu- 

 sion with which animalculce, whose ordinary dimensions ne- 

 cessarily conceal them from our view, are disseminated 

 through the strata of the earth, especially now that we know 

 the great mass of these formations to be entirely composed 

 of microscopic animalculse. Besides, M. Ehrenberg has suc- 

 cessively revealed to us such unexpected facts, that we re- 

 quire to ponder them a while before we can appreciate all 

 their importance. 



The ichthyological fauna of the old red sandstone appears 

 in such extraordinary and fantastical forms, that the most 

 trifling remains of the beings which lived at that epoch cannot 

 fail to arrest the attention of the naturalist. In no other for- 

 mation do we find an assemblage of fishes deviating so strik- 

 ingly from all that we are acquainted with in our own day. 

 The study of no other fauna requires so many years before 

 we become sufficiently familiarised with its types to venture 

 to classify them, and fix their relations to those of other crea- 

 tions. The difficulties these researches presented were quite 

 of a peculiar nature, for it was necessary to solve them, so to 

 speak, without a term of comparison, or at least to have re- 

 course to remote approximations. In fact, comparisons with 

 the remains of anterior formations w^ould have been impos- 

 sible ; because it is in the old red sandstone that we meet, for 

 the first time, with a complete ichthyological fauna. The Silu- 

 rian formations, it is true, contain some remains of fishes ; but 

 hitherto they have been so rare, and the number of species 

 so limited, that it may be safely affirmed that it is only with 

 the Devonian formation that fishes have really acquired some 

 importance among other fossils, or, at least, that the part they 

 performed in nature becomes appreciable. What first strikes 

 one, on studying the ancient deposits is, that fishes are the 

 only representatives of the branch vertebrata which exist in 



