526  PRE-CAMBRJAN    ROCKS    OP    NORTH    AMERICA.  [bull.  86. 
however,  without  any  vestige  of  clastic  character.  Above  the  IJr- 
gneiss  follows  (2)  the  UrglimmerscMefer,  which  passes  into  (3)  the  Ur- 
thonschiefer  or  Phyllit,  and  this  contains  younger  gneiss  formations. 
This  classification  has  a  structural  basis  to  a  certain  degree,  but  seems 
to  be  primarily  lithological.  Credner,  in  the  last  (seventh)  edition  of 
his  Elemente  der  Geologie,  places  the  Urgneiss  as  the  equivalent 
of  the  Laurentian  and  the  Urschiefer,  including  here  the  Urglimmer- 
schiefer  and  Urthonscheifer  as  the  equivalent  of  the  Huronian  of 
North  America. 
In  Norway  the  director  of  the  official  survey,  Dr.  Keusch,  considers 
that  it  has  been  shown  that  there  are  in  that  country  pre-Cambrian 
elastics  which  are  overlapped  by  the  Cambrian.  De  Geer  maintains 
that  there  are  pre-Cambrian  rocks  in  Sweden  which  are  unconformably 
below  the  Cambrian.  Keusch  is  inclined  to  exclude  these  rocks  from 
the  Archean,  the  latter  being  restricted  to  the  fundamental  complex. 
If  these  results  be  accepted  it  follows  that  in  Scandinavia  there  are 
rocks  which  take  a  position  represented  in  America  by  the  Algonkian. 
The  inclination  to  limit  the  term  Archean  to  the  fundamental  com- 
plex is  rather  widespread  in  Europe,  without  reference  to  whether  pre- 
Cambrian  elastics  exist  or  not.  Many  of  those  who  hold  that  pre-Cam- 
brian elastics  occur  are  disposed  to  give  them  distinctive  names.  .  As 
in  America,  no  structural  methods  have  been  applied  to  the  funda- 
mental complex. 
Eigidly  defining  the  Archean  to  cover  the  basal  crystalline  complex 
and  excluding  from  it  all  clastic  rocks,  we  have  in  England,  France, 
Germany,  and  Scandinavia  equivalents  of  the  Algonkian  of  America, 
if  those  geologists  are  right  who  maintain  the  pre-Cambrian  character 
of  the  clastic  rocks  mentioned. 
No  attempt  has  been  made,  except  in  Great  Britain,  to  subdivide  into 
series  the  rocks  equivalent  to  the  Algonkian.  The  review  of  the  facts 
in  America  has  led  to  the  conclusion  that  it  is  not  practicable  to  make 
correlations  over  the  whole  continent  of  a  more  definite  nature  than 
Algonkian  and  Archean.  If  this  be  true,  it  is  evident  that  correlations 
can  not  be  more  definitely  made  between  European  and  American  rocks. 
The  application  of  such  American  terms  as  Huronian  and  Keweenawan 
to  European  series  is  wholly  unwarranted. 
If  the  suggestionbe  correct  that  the  Archean  is  of  a  different  char- 
acter from  any  succeeding  formation  and  has  a  continental  extent  in 
America,  it  may  be  safe  to  regard  the  fundamental  complex  of  Europe 
as  its  equivalent.  If  this  be  done  and  Cambrian  be  delimited  below 
by  the  Olenellus  fauna,  it  would  be  safe  to  say  that  the  intervening 
series  of  rocks  occupy  some  position  in  the  great  Algonkian  system. 
But  any  given  series  of  the  Algonkian  of  Europe  can  not  safely  be 
placed  opposite  a  definite  series  in  this  country  until  there  shall  be 
found  paleontological  evidence  for  so  doing. 
Even  if  the  Cambrian  in  Europe  were  rigidly  delimited  below  by  the 
