Barrande— Origin of Paleozove Species. 188 
multiplicity of specific forms, the Trilobites are far from possess- 
Ing so marked a predominance. * * Although the Trilobites 
maintain some numerical superiority, as regards species, in all 
the three faunas, it has not been very noticeable. But, 1f we 
consider only the second and third faunas, the predominance of 
the Cephalopods becomes, on the contrary, very great. On the 
whole, in spite of the privileges which seem to assure the first 
rank to the Trilobites, in the whole of the Silurian faunas, the 
Cephalopods possess exclusively certain advantages, W ich 
assured their domination during the continuance of the second 
and third faunas. The total number of Silurian species enume- 
tated in the “Thesaurus Siluricus,” in 1868, reached 9,030. 
Adding about 800 Bohemian species, the names of which are 
hot yet published, and the new species announced in Canada 
and elsewhere, the sum total of forms known in the Silurian 
Il. First appearance of Cephalopods.—W hat is most inexpli- 
cable to us is alia eet abruptness with which the Cephalo- 
hearly half the total number of types of this order, which is 20. 
. as a whole, present the — forms 
