Brise of the 'Vncniiic or Lover Co mhrid d. — M'aichell. 158 
olarians, numerous and composed of few genera (Sjfume^aria) 
and radiolarians much more elevated in organization, and less 
abundant, but distinguished by a greater number of specific^ 
forms (Xdsselhrrid). Such is the salient character of tlie 
fauna." 
"Notwithstanding the numerical superiority' of Cenosphjcra, 
that is to sa}', of the genus which counts among the most ar- 
chaic of the group, this fauna of radiolarians, considered as a 
whole, cannot be regarded as the fauna of radiolarians which 
first appeared ; it possesses a character of complexity and 
completeness, such as implies the prcexistence of several other 
faunas of radiolarians less developed/' 
"Such a fauna found at an ejioch more recent would lead us 
certainly to the conclusion that it had been preceded in time 
by more imperfect radiolarians; why then should we reject 
the same conclusion when the pre-Cambrian is concerned?" 
"We onh^ deduce from the ancient faunas the supposition 
of faunas older yet. All our efforts to exhume the most 
primitive creatures end invariably in the same result — to push 
back the date of the appearance of life on our planet." 
"It is to the study of siliceous micro-organisms that the ge- 
ologist who desires to restore the first pages of our palaionto- 
logical archives should apply himself. Experience has shown 
that the radiolarians have the quality of preserving the com- 
pleteness of their form and their composition, despite the 
metamorpliism which transforms all around them. So I be- 
lieve [saj^s Mr. Cayeux] that the last words on the most an- 
cient faunas will appertain to the microscopists." 
[CKUCIAI, PnlNTS IN THK fiEOI.CIli'i' dl' lllh; I.AKF, SUJ'KKIDR RKCION'. \l). I.] 
THE STRATIGRAPHIC BASE OF THE TACONIC 
OR LOWER CAMBRIAN. 
X. II. W'iNCili-.i.i.. Minneapolis. Minn. 
It is proposed to re-examine, in the light of present devel- 
opments, several of the points of greatest ditliculty in the ge- 
ology of the region of lake Superior. It is on these (|uestions 
that geologists have dillered. It is possible that there is less 
uncertainty, when the facts are all grouped in ii systematic 
