FIEST PAL/EOZOIC PERIOD. 



deposits, and it is probable that if land Vertebrates had existed, 

 remains of them would be found. 



265. The seas, however, abounded with life, including animals 

 of all the principal divisions, Vertebrata, Annulata, Mollusca, and 

 Radiata. 



In the following table we have given the genera of the animal 

 kingdom during this period, exclusive of the Annulata. 



266. Synopsis of the Animal Kingdom (exclusive of the Annulata) in the 

 First Palaeozoic Period. 



267. Eighteen genera of Trilobites existed in the first Palaeozoic 

 period, of which seven never re-appeared in any future period, 

 and are consequently characteristic of the Cambrian stage. Some 

 individual examples of other Annulata have been found, one of 

 the most remarkable of which is the Nereites Cambriensis, fig. 5, 

 36. The number of species of the Mollusca and Radiata alone, 

 exclusive of the other divisions, which are ascertained to have 

 lived in this period, is 426. These have been catalogued and 

 described by M. d'Orbigny,* 



268. The duration of this first world of animal and vegetable 

 life may be estimated with some degree of approximation by 

 the thickness of the deposits produced in its seas, which has 

 been found in many places so much as 13000 feet. 



Its close is marked by the discordances of stratification which 

 prevail between the Cambrian and the Silurian strata, and it is pro- 

 bable that the convulsion by which it was terminated, was that 

 which raised the Morbihan system of mountains of M. Elie de 

 Beaumont (208). 



Prodrome de Paleontologie, vol. i. p. 1 26. 



43 



