342 M. Agassiz on Fossil Fishes. 



fact are as new as they are bold ; for they tend to nothing less 

 than to prove, that fishes are in some sort the primitive trunk 

 from which, in the course of time, the different other <jlasses 

 of the vertebrata have been detached. It is, indeed, curious 

 to observe, that fishes have been, during the whole Transition 

 period, the only representatives of the vertebrata. There is, 

 in particular, a type of voracious fishes, which arrives at its 

 apogee in this period; namely, that of the Sauroids, which 

 seems to have then shared with the sharks the empire of the 

 seas, in so much that this period may be justly called the reign 

 of fishes. 



Only at a later date, during the Triassic period, reptiles ap- 

 peared, and they soon became, in their turn, the lords of the 

 creation, principally in the Jurassic formation, when the Ich- 

 thyosauri and the Plesiosauri inhabited the scarcely formed 

 coasts of Europe, It was then the reign of reptiles. A mul- 

 titude of fishes belonging to new species existed along with 

 these reptiles, but they lost the pre-eminence ; and if many 

 of them attract observation by their large size, they are still 

 far from equalling the power of the great Sauroids of the car- 

 boniferous epoch. 



With regard to mammifera and birds, M. Agassiz makes 

 their reign commence only with the tertiary epoch ; and here, 

 perhaps, his system is open to criticism, for he is not ignorant 

 that there exist mammifera of the Jura period (the fossil Didel- 

 phis of Stonesfield) ; and we believe that he has distinctly ad- 

 mitted that it is to the type of the mammifera that these sin- 

 gular remains ought to be referred. If he takes no account of 

 them in his system, it is, no doubt, because he regards them as 

 an exception ; and, in fact, it is curious that we meet with no 

 other remains of mammifera in the subsequent strata of the 

 Jura formation and of the chalk formation, while they appear 

 suddenly in extraordinary abundance, and of colossal dimen- 

 sions, in the tertiary epoch. With regard to birds, M. 

 Agassiz has himself informed us that unquestionable traces of 

 them exist in the slates of Glaris. Now, while we acknow- 

 ledge the ingenuity of regarding the succession of types in 

 this manner, it would still be of much importance, in the in- 

 terest of the system, that neither mammifera nor birds were 



