Barrande—Origin of Paleozove Species. 189 
immigration of foreign species] are entirely new, and represent 
the effect of gradual renewal. These three sources united have 
furnished only about 84 per cent. of the species of Cephalopods 
in any fauna whatever. * * There remain, then, about 66 per 
It remains for us to call the attention of our scientific readers 
to the harmony which exists between the results of this study 
pon the ual renewal of species and the results of the 
parallel established above between the zodlogical and the chron- 
Slogical evolution of Cephalopods. In considering the chron- 
3 ypes, parallel has 
brought us to recognize that the generic and specific forms 
= the Silurian Cephalopods cannot be regarded as gradually 
ved 
More simple to the more compli 
the successive evolution of the Cephalo, cannot be attri- 
