SUMMARY   OF    GENERAL   LITERATURE. 
101 
Since  this  time  Matthew  has  introduced  the  term  Etcheminian  to 
designate  certain  fossiliferous  sediments  found  beneath  the  middle 
Cambrian,  probably  belonging  to  the  more  recent  portion  of  the  pre- 
Cambrian  formations. 
In  Ontario  and  Quebec  the  oldest  granite  gneiss  may  be  styled 
Laurentian.  The  second  member  of  the  scale,  or  the  Huronian,  may 
be  made  to  include,  as  its  lowest  portion,  that  part  of  the  crystalline 
series,  once  regarded  also  as  part  of  the  Laurentian  system,  which  is 
known  locally  under  the  names  Grenville  and  Hastings  series,  the  re- 
lations of  which  to  the  Laurentian  proper  are  apparently  of  two 
kinds — a  stratigraphic  sequence,  with  a  probable  unconformity,  owing 
to  difference  in  origin,  and  a  contact  of  intrusion.  Portions  of  the 
Grenville  and  Hastings  series  correspond,  while  the  latter  is  carried 
upward  through  less  altered  sediments  to  the  upper  members  of  the 
Huronian  system. 
In  the  Lake  Superior  region  the  Huronian  is  succeeded  upward  by 
the  rocks  of  the  Cambrian,  represented  by  the  Upper  Copper-bearing 
series,  or  the  Animikie  and  Nipigon  groups ;  while  in  eastern  Ontario 
this  portion  of  the  scale  is  apparently  entirely  lacking,  the  formation 
succeeding  the  crystalline  series  being  the  Potsdam  sandstone,  which 
is  now  held  to  represent  the  lowest  member  of  the  Cambro-Silurian  or 
Ordovician  system. 
Ami,34  in  1900,  summarizes  the  geology  of  Canada  and  indicates 
the  meaning  and  correlation  of  the  principal  terms  employed  in 
Canadian  geological  nomenclature. 
Ami,35  in  1900,  briefly  summarizes  the  salient  features  of  the 
geology  of  the  principal  cities  of  eastern  Canada,  including  St.  John, 
OttaAva,  Quebec,  Montreal,  and  Toronto. 
Coleman,30  in  1902,  discusses  the  classification  of  the  Archean 
(pre-Cambrian  of  the  United  States  Geological  Survey)  and  pro- 
poses the  following: 
(Keweenawaih 
Unconformity. 
Animikie. 
Eparchean  interval. 
Laurentian = Fundamental  gneiss,  etc. 
Eruptive  unconformity. 
Upper    Huronian     or     Huronian' 
proper. 
Archean  Unconform  i  I  y . 
Huronian.  A  ("Schistose     pyro- 
Lower  Huronian 
or  Keewatin. 
elastics    and 
eruptives. 
Coutchiching. 
=Grenville    and    Hast, 
ings  series. 
Wilson,37  in  1903,  describes  the  Laurentian  peneplain  of  the  great 
pre-Cambrian  shield  of  Canada  and  adjacent  portions  of  the  United 
