NEW    BRUNSWICK,    NOVA    SCOTIA,    NEWFOUNDLAND,    ETC.      497 
tional  amount  in  the  former  of  distinctly  stratified  rocks,  such  as 
slates  and  quartzites,  and  the  absence  of  coarsely  crystalline  deposits. 
As  regards  the  Huronian  rocks,  the  greater  part  were  referred  to  as 
felstones,  clay  stones,  porphyries,  and  petrosilex  before  the  introduc- 
tion of  the  present  methods  of  petrographical  research,  and  their 
names  in  some  instances  are  probably  misapplied.  The  relations  of 
the  Laurentian  and  Huronian  systems  are  not  well  understood. 
While  the  author  does  not  doubt  that  the  clastic  and  schistose  rocks 
referred  to  the  Huronian  are  more  recent  than  the  granitoid  gneissic 
and  crystalline  limestones  regarded  as  Laurentian,  a  contrary  view 
has  been  taken  by  others. 
Matthew,25  in  1800,  states  that  in  the  Upper  Laurentian  of  New 
Brunswick  fossils  occur  at  three  horizons.  The  oldest  of  these  is  in 
a  quartzite  in  the  lower  half  of  the  system.  This  contains  hexacti- 
nellid  sponges,  allied  to  the  genus  Cyathospongia.  The  second  hori- 
zon is  in  the  upper  limestone.  It  contains  calcareous  coral-like  struc- 
tures which  bear  a  resemblance  to  Stromatopora  rugosa.  The  third 
horizon  is  that  of  the  graphite  beds,  in  which  occur  great  numbers  of 
sponge  spicules,  arranged  in  parallel  sets,  one  set  crossing  the  other 
at  an  acute  angle.  The  type  of  sponge  is  apparently  monactinellid. 
Eozoon  also  occurs  in  the  Laurentian.  Between  the  Upper  Laurentian 
system  and  the  basal  Cambrian  occurs  a  third  system  of  rocks,  the 
Coldbrook  and  Coastal,  which  has  given  conglomerates  to  the  Cam- 
brian and  has  a  great  thickness. 
Matthew,26  in  1894,  describes  the  pre-Cambrian  area  near  St.  John, 
New  Brunswick.  The  earliest  series,  or  Laurentian,  consists  chiefly 
of  granitic  and  gneissoid  rocks,  limestones,  and  quartzite,  the  two 
latter  being  confined  to  the  upper  beds.  The  strata  lie  steeply  in- 
clined in  a  succession  of  ridges  and  folds  striking  in  a  general  north- 
east-southwest direction.  Overlying  this  more  crystalline  series, 
generally  at  a  lower  dip,  are  fine-grained  flinty  rocks,  interbedded 
with  various  schists,  porphyries,  ash  rocks,  and  sandstones,  and  with 
great  masses  and  dikes  of  trap.     These  have  been  called  Huronian. 
The  old  part  of  the  Laurentian  consists  of  gneisses  proper,  accom- 
panied by  hornblende  schists  and  mica  schists,  which  in  thin  section 
show  no  trace  of  igneous  origin,  and  of  limestone  and  quartzite. 
Associated  with  the  less  crystalline  limestones  are  beds  of  fine-grained 
black  rock,  which  has  generally  been  called  argil  lite.  Much  of  the 
Lower  Laurentian  series  consists  of  granite,  diorite,  and  gabbro, 
which  are  igneous  rocks.  The  granite  intrudes  both  the  gabbro  and 
the  sedimentary  series,  as  is  shown  by  contact  effects  and  by  veins 
and  pegmatite  masses  adjacent  to  the  granite  in  the  sedimentary 
series.  As  to  the  age  of  this  intrusion,  it  may  be  as  late  as  Devonian, 
but  as  the  granite  is  cut  by  innumerable  dikes  which  also  cut  the 
Huronian  and  the  Paleozoic,  it  is  very  likely  that  the  intrusion  is 
55721— Bull.  360—09 32 
