400 The American Geologist. June, 1S97 
of only six feet separates the two faunas, and there is no 
physical break between them. 
We think the Schmidtia ynichwitzl stock older, and imagine 
there is a parallel in the development of the olenellid stem 
similar to that which is seen in the paradoxidean, Protolenus 
is undoubtedly older than Paradoxides, but is very similar in 
structure, differing most markedly in the form of the glabella 
which is cylindrical in place of club-shaped. A similar rela- 
tion holds in Olenellus, for the branch stock which contains 
S. michwitzi, O. callavii and O. brogyeri, with cylindrical gla- 
bellas, is the only branch of the olenellids u'hich is entirely 
below Paradoxides. Protolenus, in this respect, bears the 
same relation to Paradoxides. 
Some of those branches of ,the olenellid stock (as Holmia 
h-jerulfi) with enlarged glabellas, and uniform development as 
regards the thorax, are also below Paradoxides. We may now 
inquire how far the genera of trilobites, brachiopods, etc., as- 
sociated with the olenellids throw light on their position rela- 
tive to Paradoxides. 
Criterion of the Associated Genera. 
Mr. Walcott's "Fauna of the Olenellus Zone" consists es- 
sentially of the fossils gathered from four distinct areas : 1, 
West Vermont to Labrador (and eastern Massachusetts ?); 
2, Newfoundland; 3, Eastern New York ; 4, Western America.* 
The age of the Olenelli in the 4th area will depend upon 
the decision as to the age of those of the first area. The spe- 
cies of the 2d are clearly beneath the Paradoxides beds, but 
the}^ do not belong with Olenellus, sensu stricto. The fauna 
of the 3d area, that of eastern New York, may now be con- 
sidered_ In previous publications the author has casually re- 
ferred to some of the species of this fauna, and they are in 
evidence in relation to the subject of this paper. 
Bad figures and distorted specimens for a longtime left the 
relations of Emmons' Atops trilineatus in doubt, and it was 
only when Ford's assertion that it was a Conocoryphe was sup- 
ported by Walcott's excellent figures of the better specimens, 
that the relations of this species became apparent. Conocory- 
phe, as we know, is in Europe a genus of the Paradoxides 
*Fauna of the Lower Cambrian or Olenellus Zone, p. 574. 
