Cambrian Rocks in Acadia. 5 
In Europe it has been found that there is a great prepon- 
derance of species of Agnostus in the lower part of the 
Paradoxides Zone. There are in the— 
Ceratopyge limestone and shale, 2 species. 
Olenus Zone (4 in the lower part), 5 species. 
Paradoxides Zone (25 in the lower part), 29 species. 
Zone of Paradoxides (?) Kjerulfi, 0 species. 
Dr. Brégger calls the last named the Olenellus Zone, on 
account of the genetic relations of Olenellus to P. (?) Kjerulji, 
and compares the absence of the genus Agnostus at this 
horizon in Europe, with the scarcity of it in the true Olenel- 
lus Zone in America, and then shows that species of 
Agnostus are more numerous in the Acadian than the 
Georgian Series in America, as they are in the Paradoxides 
Zone, when compared with the Zone of Olenellus (?) 
Kjerulfi in Europe. Butif the Olenellus Zone of America be 
compared with the Ceratopyge beds of Europe, it will be 
seen that that group also is characterized by a paucity of 
species of Agnostus. 
One of the most characteristic genera of the Georgian 
Series is Olenellus. Of its close relationship to Paradoxides 
there can be no question, and yet it is associated with an 
assemblage of species differing widely from those of the 
Paradoxides Zone in Europe. There is the further remark- 
able feature that Olenellus is more closely related to the 
older species of Paradoxides, than to the later; indeed, so 
close is this relation to the earliest Paradoxidean form in 
Scandinavia, that this form, P. (gen.?) Kjerulfi, has been 
ealled Olenellus. As long as the pygidium remained un- 
known, there was much to sustain this view of its generic 
relations; but now that this part of the organism (a very 
important part in the economy of the trilobites) has been 
recovered, and is found to conform to that of Paradoxides, 
and not of Olenellus, it is evident that the species cannot 
be referred to the latter genus. 
On the other hand, the admirable study of’ this species 
carried out by Gerhard Holm’ shows that it differs from 
'“ Or Olenellus Kjerulfi,” in “Geol. Féren. i Stockholm,” 1887. 
