What is the Olenellas Fauna? — Matthew. 397 
whether they contain that genus or not,* the present seems an 
opportune time to inquire how far such a practice is advisable, 
in view of the wide range that has been given to that fauna 
by the addition of numerous faunas, mostly pre-paradoxidean 
in Europe, America, and elsewhere. f It is not known that all 
these branches of the Olenellus stem preceded Paradoxides, 
nor is it known that even the type species preceded this 
genus. 
That Olenellus is older than Paradoxides is altogether a mat- 
ter of inference, based partly upon the constitution of the Ole- 
nellus fauna itself, and partly upon the fact that related subge- 
nera are found below Paradoxides. Yet such is the effect of the 
strong plea that has been made for the greater antiquity of 
Olenellus, that faunas older than Paradoxides;]; have unhesi- 
tatingly been referred to the Olenellus horizon, though no spe- 
cies of Olenellus has been found in them. Why, then, should 
they be referred to the Olenellus zone? 
Let us see if we can gather any information on this still 
obscure question, the age of Olenellus, from the pre-Paradox- 
idean faunas. There are two aspects of proof available from 
the olenellid faunas themselves which may throw light upon 
the matter. One is the individual form and development of 
the several olenellid species; the other is the associated spe- 
cies found in the several faunas. 
Criterion of Structure and Development. 
Among the olenellid trilobites which have been found ac- 
tually to precede Paradoxides, there are two principal types, 
one represented by Ilolmia kjernlti and the other by 0. ( Calla- 
iu,a)^ brogr/eri and 0. (Schmidtia) michwitzi; and although the 
latter is separated to another sub-genus on account of its tho- 
rax, if we regard the head-shield, and especially the glabella, 
we shall be inclined to associate it with the second of the 
above species rather than with the first. And this is probably 
* I confess to haviugbeen influenced by this tendency myself in for- 
mer years, as we then had not come to appreciate the individuality of 
the pre-Paradoxidean genera as we now do. 
tThe Fauna of the Lower Cambrian or Olenellus Zone. Extract from 
the 10th Annual Rep(jrt, U. S. Geol. Survey, pp. 572 to 575. 
Jin Bohemia, France and Spain. 
§1 propose this subgoneric name for O. brotfgeri and O. callavii be- 
cause the glabella differs from O. (H.) kjerulfi, etc. 
