44 Fossil Fishes. 



I 



ular development of all created beings, in fixed relation to all the 

 different conditions of existence which are realized on the surface of 

 the globe, at the conclusion of those changes to which it has itself 



been subjected. 



" According to all these facts, I perceive in these series of all the 

 geological formations two grand divisions, which have their limits at 

 the greensand. The former, and more ancient, includes only the 

 Ganoides and Placoides; the latter, more closely allied with the 

 existing species, comprehends forms and organizations much more 

 diversified ; and these are principally the Ctenoides and the Cycloi- 

 des, and a very small number of the species of the two preceding 

 orders, which insensibly disappear, and the living resemblances of 

 which are very considerably modified. As I do not find in the fish- 

 es of the first grand period the differences which correspond to those 

 which we now observe between fresh-water and marine fishes, it ap- 

 pears we perhaps go farther than facts warrant when we admit in 

 the oolite series, and in those which are lower than it, distinct for- 

 mations of fresh and salt water. I rather think that the waters of 

 these remote periods, confined in less secure basins, did not then 

 present the same striking differences which we observe in our own 

 days. 



" Such is a very meagre sketch of a history of the deepest inter- 

 est, and full of curious episodes, which are, however, somewhat dif- 

 ficult to relate. The exposition of the details which it includes will 

 be the task of my life." 



The fifth number contains chiefly histories and descriptions of 

 genera and species met with in the formations of England and Scot- 

 land.* The plates in this number are even more admirably execu- 

 ted than those in the fourth livraison. The following enumeration of 

 the new British species may prove acceptable to our geological rea- 

 ders : — 1. P al<zonisc\is . Of this genus the following species are 

 described : 1. P. Robisoni, found in the limestone of Burdiehouse, 

 near Edinburgh, and by Professor Jameson in the Burntisland dis- 

 trict. 2. P. striolatus, found at Burdiehouse and in Fifeshire. 3. 

 P. ornatissimus , in the limestone of the Burntisland district. 4. P. 

 elegans, in the magnesian limestone of Durham. 5. P. comatus, 

 Durham. 6. P. glaphyrus, magnesian limestone. 7. P. macroph- 





* Although the fifth livraison is not yet published, we have, through the kind- 

 ness of the author, obtained a sight of it. 



