SUMMARY   OF   GENERAL  LITERATURE.  91 
Montalban,  and  Taconian  terranes  are  all  found,  the  outcrops  of  the 
Taconian  have  been  confounded  with  those  of  the  Huronian  terrane 
by  Murray  and  other  observers.  In  1873,  however,  the  author,  dis- 
tinguishing between  the  two,  gave  to  the  Taconian  terrane  in  this 
region  the  provisional  name  Animikie  series.  Not  until  later  did  he 
recognize  the  fact  that  this  series,  which  in  certain  localities  rests  un- 
conformabty  on  the  Huronian  terrane,  is  the  Taconian.  Emmons,  on 
the  contrary,  who  knew  the  existence  in  this  region  of  what  he  called 
the  Lower  Taconic,  thought  that  the  terrane  to  which  in  1855  the 
author  had  given  the  name  Huronian  was  identical  with  this  same 
Lower  Taconic  or  Taconian.  The  differences  between  the  two  ter- 
ranes in  the  basin  of  Lake  Superior,  indicated  first  by  Logan  and 
afterward  by  the  author,  appear  very  clearly  from  the  recent  studies 
of  Kominger.  On  the  various  crystalline  terranes,  including  the 
Taconian,  there  rests  in  this  region  unconf  ormably  an  enormous  series 
of  sandstones  and  conglomerates,  with  contemporary  plutonic  rocks, 
the  whole  being  remarkable  for  its  content  of  metallic  copper.  This 
series,  which  had  been  alternately  confounded  with  the  Huronian  and 
Taconian  terranes  on  the  one  hand  and  with  the  trilobitic  sandstones 
of  the  Cambrian  on  the  other,  was  for  the  first  time  separated  by  the 
author  in  1873  under  the  name  Keweenaw  group,  a  term  which  he  in 
1876  converted  into  Keweenian  terrane.  It  still  remains  to  be  deter- 
mined whether  this  series,  on  which  these  same  trilobitic  sandstones 
rest  unconf  ormably,  should  form  part  of  the  Cambrian  terrane  or 
whether  it  should  form  a  distinct  terrane  between  the  Taconian  and 
the  Cambrian. 
Dawson,20  in  1889,  presents  a  brief  note  on  Cryptozoon  and  Arch- 
eozoon  found  in  the  pre-Cambrian.  A  general  discussion  is  given  of 
the  biological  affinities  of  the  Cryptozoon  and  Archeozoon,  and  de- 
scriptions are  quoted  of  younger  forms  which  may  be  the  successors  of 
the  pre-Cambrian  forms. 
Bell,21  in  1889,  characterizes  the  Huronian  as  the  great  metallifer- 
ous series  of  Canada.  While  rocks  of  igneous  origin  constitute  a 
marked  feature  in  the  Huronian  system,  a  large  proportion  of  it  is 
made  up  of  rocks  of  an  undoubted  sedimentary  character.  On  the 
other  hand,  it  is  questionable  if  the  great  bulk  of  the  Laurentian  rocks 
can  be  proved  to  have  been  deposited  from  water.  It  is  supposed  by 
many  that  the  foliation  of  much  of  the  gneiss  may  have  been  pro- 
duced by  pressure  and  some  kind  of  flowing  movement  in  an  igneous 
mass.  Whatever  view  we  may  take  of  the  origin  of  the  common 
Laurentian  gneiss,  which  forms  the  surface  of  the  country  over  so 
vast  an  extent  of  the  Canadian  half  of  North  America,  the  commence- 
ment of  the  Huronian  period  marks  a  great  change  which  then  came 
over  the  earth — a  change  characterized  by  widespread  volcanic  out- 
bursts and  by  evidence  of  the  existence  of  water  (perhaps  the  first) 
