van  his*,  i  DISCUSSIONS    OF    PRINCIPLES.  461 
essary  to  inquire  whether  the  new  groups  are  to  be  regarded  as  Paleo- 
zoic. All  may  be  regarded  as  Archean;  Paleozoic  may  be  carried 
down  to  the  break  between  the  Keweenawan  series  and  the  Huronian; 
Archean  may  be  restricted  to  the  gneissic  basic  series;  and,  finally, 
some  entirely  new  term  of  equal  rank  with  Paleozoic  and  Archean  may 
be  introduced  to  cover  the  formations  between  the  gneissic  series  and 
the  Cambrian.  The  apparent  relative  extent  of  the  time  intervals  be- 
tween these  several  groups  and  the  indications  presented  by  them  of 
the  existence  of  life  during  their  deposition  lead  to  the  conclusion  that 
there  should  be  introduced  a  system  term  equivalent  to  Paleozoic  and 
Archean.  In  favor  of  restricting  Archean  to  the  gneissic  basement 
teirane  are  the  facts  that  this  is  essentially  a  crystalline  schist  series, 
having  rarely  any  traces  of  fragmental  constitution,  because  it  shows 
an  amount  of  disturbance  prior  to  the  deposition  of  the  Huronian,  which 
entirely  outweighs  that  received  by  the  Huronian,  while  the  amount 
of  denudation  of  the  pre-Huronian  land  surface,  as  compared' with  that 
which  followed  /the  Huronian,  was  immensely  greater;  and  because 
many  believe  that  the  exact  conditions  which  gave  rise  to  the  pre- 
Huronian  basement  formation  has  never  been  repeated  in  later  geo- 
logical time's. 
There  is  no  satisfactory  evidence  of  the  existence  of  life  previous  to 
the  deposition  of  the  Huronian.  That  it  existed  plentifully  in  the 
Huronian  is  indicated  by  the  high  development  of  life  at  the  beginning 
of  the  Cambrian  and  its  consequent  necessary  existence  for  great  periods 
prior  to  that  time ;  by  the  occasional  discovery  of  obscure  fossil  remains ; 
by  the  abundant  occurrence  of  shales  and  slates  filled  with  organic 
matter;  by  extended  ferruginous  strata  whose  original  accumulation 
in  the  form  of  carbonate  was  certainly  dependent  upon  the  existence  of 
organic  matter.  That  the  carbon  of  the  shales  is  matter  of  genuine 
organic  origin  is  shown  by  residual  traces  of  hydrocarbons  and  by  the 
fact  that  the  carbonaceous  substance  in  character  and  occurrence  is 
entirely  similar  to  that  contained  in  the  carbonaceous  shales  of  later 
formations.  If  the  term  Paleozoic  is  to  be  used  to  cover  all  formations 
accumulated  after  the  beginning  of  the  existence  of  life,  it  should  ex- 
tend downward  over  the  groups  in  question ;  but  such  is  not  its  ordi- 
nary use,  and  to  extend  it  downward  over  the  Keweenawan  and  Hu- 
ronian strata  and  the  intervals  indicated  by  the  unconformities  between 
the  groups  already  discovered,  and  over  such  groups  as  shall  be  dis- 
covered in  the  vast  area  of  the  earth's  surface  not  yet  geologically 
known,  does  not  seem  warranted.  It  is  therefore  desirable  that  a  new 
term  shall  be  introduced  of  equal  classificatory  value,  indicating  that 
the  great  pre-Cambrian  and  post- Archean  series  are  zoic  in  character 
and  are  equal  to  or  greater  in  volume  than  the  Paleozoic.  For  this  place 
is  suggested  the  term  Agnotozoic,  but  some  of  the  writer's  colleagues 
prefer  the  more  noncommittal  term  of  Eparchean,  signifying  simply 
the  position  of  these  formations  upon  the  Archean. 
