Barrande— Origin of Paleozoic Species. 187 
vertical thickness of a few calcareous layers of our formation 
E. These distinct forms reach the number of 746, representing 
the proportion of 0°46, 7. e., nearly half, of the 1622 species of 
Cephalopods to-day known in the Silurian world. 3. If the 
Song study, there has arisen no new type, either cosmopolite or 
ocal, during all the continuance of the Devonian, Carboniferous 
and Permian faunas. * * Still, as a whole, these faunas present 
4 number of species of Cephalopods at least as considerable as 
that of the second Silurian fauna, during which there appeared 
17 generic types. In this case, neither time, nor space, nor the 
— of specific forms, failed to favor the production of some 
ew ty e, 
tt ie ahen the very power of variation or transformation 
that has itself been wanting. If this pretended force really 
48 a continuous action, and one inherent to the nature of 
characters, from the Silurian period, without producing a single 
“arg and distinct type, in spite of the number of their 
ific forms, in every country and i 
faunas, If the type of Cephalopods * * had been gradually 
constituted by transformations, up to their normal form, the 
be 
s, whose 
examples showing the exact form which we, find. 
transition forms are nowhere found in Silurian countries. 
