SUMMAKY   OF    GENERAL   LITERATURE. 
87 
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  char- 
acter and  are  in  volume  equal  to  or  greater  than  the  Paleozoic.  For 
this  place  is  suggested  the  term  Agnotozoic,  but  some  of  our  col- 
leagues prefer  the  more  noncommittal  term  Eparchean,  signifying 
simply  the  position  of  these  formations  upon  the  Archean. 
The  following  table  shows  alternative  classifications  suggested  by 
the  above: 
System. 
Group. 
System. 
[Carboniferous 
1  Devonian 
(Cambrian 
|  Keweenawan 
Agnotozoic  or  Eparchean 
<  Huronian 
Archean 
Laurentian  (including  Upper  Laurentian) 
Hunt,19  in  1888,  summarizes  the  results  of  his  work  on  the  arrange- 
ment, subdivision,  and  nomenclature  of  the  pre-Cambrian  terranes  as 
follows : 
(1)  Laurentian.  Under  this  name,  proposed  and  adopted  by  the 
author  in  1854,  is  comprised  the  old  gneissic  terrane  found  especially 
in  the  Laurentide  and  Adirondack  mountains,  as  well  as  in  the  great 
Atlantic  chain  and  in  the  Rocky  Mountains  of  the  center  of  North 
America.  To  this  same  series  the  author  has  also  annexed  the  similar 
gneisses  of  Great  Britain  and  Scandinavia,  as  well  as  the  old  or  cen- 
tral gneiss  of  the  Alps.  From  the  time  of  our  first  studies  in  Canada, 
in  1847,  we  had  pointed  out  the  existence,  in  this  gneissic  terrane,  of 
two  subdivisions,  one  lower,  of  granitoid  gneiss  which  blends  with 
the  fundamental  granite,  to  which  succeeds  with  unconformable  strati- 
fication a  series  of  gneisses,  also  granitoid,  frequently  amphibolic, 
interspersed  with  quartzites  and  crystalline  limestones,  with  serpen- 
tine. These  two  subdivisions,  which  we  may  provisionally  name 
Lower  and  Upper  Laurentian,  have  been  called  respectively  the 
Ottawa  gneiss  and  the  Grenville  series.  In  order  to  avoid  all  error 
it  is  necessary  to  note  that  the  title  Upper  Laurentian  was  for  some 
time  given  by  Logan  to  the  terrane  designated  afterward  Labra- 
dorian  and  Norian.  It  is  therefore  through  misunderstanding  that 
some  have  wished  to  retain  as  a  designation  of  the  upper  division  of 
the  Laurentian  terrane  the  term  Middle  Laurentian. 
(2)  Norian.  The  terrane  thus  designated  by  the  author  in  1870  is 
in  large  part  composed  of  those  stratified  rocks  that  have  an  anorthic 
feldspar  base  to  which  the  name  norite  has  been  given.  This  terrane, 
however,  includes  intercalated  beds  of  gneiss,  quartzite,  and  crystal- 
