Barrande— Origin of Paleozoic Species. 185 
Cephalopods, were already previously manifested in the first 
appearance of the Trilobites. They seem to have been even 
more exaggerated in what concerns this tribe of Crustaceans. 
al. 
IIT. Hvolution of Cephalopods.—The evolution of Cephalo- 
pods, during the continuance of the second and third Silurian 
dueed b enera, in our band g’, succeeds immediately the 
absolute maximum of 11 types, represented only by 86 species, 
mour band g*. Th facts, well ascertained, suffice to 
ec untry. 
The appearances of the 26 types of this order are mainly con- 
centrated in three principal epochs, which correspond to the 
