﻿PEGtT 
  GROUP. 
  81 
  

  

  as 
  tangible 
  horizons. 
  As 
  an 
  instance 
  of 
  this, 
  I 
  may 
  quote 
  the 
  Cytlierea 
  

   Promensis 
  bed 
  opposite 
  Prome, 
  which 
  proves 
  one 
  of 
  the 
  richest 
  fossili- 
  

   ferous 
  beds 
  in 
  the 
  group, 
  yet 
  I 
  do 
  not 
  know 
  any 
  other 
  spot 
  where 
  this 
  

   bed 
  can 
  be 
  identified 
  ; 
  and 
  though 
  interesting 
  as 
  a 
  good 
  repository 
  for 
  

   fossils, 
  its 
  use 
  as 
  a 
  stratigraphical 
  index 
  is 
  absolutely 
  nil. 
  If 
  this 
  is 
  the 
  

   case 
  with 
  a 
  bed 
  more 
  richly 
  charged 
  than 
  usual 
  with 
  fossils, 
  still 
  less 
  

   does 
  the 
  mineral 
  character 
  of 
  the 
  beds 
  aid 
  us 
  in 
  correlating 
  distant 
  sec- 
  

   tions 
  ; 
  and 
  all 
  that 
  I 
  can 
  therefore 
  offer 
  in 
  the 
  way 
  of 
  sub-division 
  of 
  

   this 
  group, 
  is 
  the 
  somewhat 
  meagre 
  arrangement 
  of 
  it 
  into 
  lower 
  and 
  

   upper 
  ; 
  the 
  lower 
  embracing 
  the 
  Sitsyahn 
  shales, 
  so 
  called 
  from 
  a 
  village 
  

   of 
  that 
  name, 
  eight 
  and 
  a 
  half 
  miles 
  above 
  Pro 
  me, 
  and 
  the 
  rest 
  com- 
  

   prised 
  under 
  the 
  term 
  Prome 
  beds, 
  embracing 
  everything 
  between 
  the 
  

   Sitsyahn 
  shales 
  and 
  the 
  fossil-wood 
  group. 
  

  

  Sitsyahn 
  shales. 
  — 
  The 
  base 
  of 
  the 
  Pegu 
  group 
  would 
  appear 
  to 
  con- 
  

   sist 
  of 
  a 
  thick 
  deposit 
  of 
  shales, 
  with 
  a 
  little 
  sandstone 
  very 
  subordi- 
  

   nately 
  developed. 
  It 
  is 
  seldom 
  that 
  any 
  good 
  sections 
  of 
  these 
  beds 
  are 
  

   seen, 
  but 
  the 
  shale 
  is 
  exposed 
  in 
  several 
  places 
  along 
  the 
  boundary 
  of 
  the 
  

   Nummulitic 
  group, 
  which 
  it 
  seems 
  to 
  overlie 
  in 
  conformable 
  sequence. 
  

   In 
  the 
  Thamula 
  section 
  of 
  the 
  Nummulitic 
  group, 
  a 
  soft 
  sandstone 
  

   takes 
  its 
  place 
  ; 
  but 
  this 
  is, 
  I 
  believe, 
  a 
  local 
  substitution 
  of 
  a 
  sandstone 
  

   at 
  this 
  particular 
  spot 
  for 
  the 
  shale 
  which 
  is 
  usually 
  found 
  overlying 
  the 
  

   Nummulitic 
  group. 
  From 
  its 
  character, 
  this 
  shale 
  forms 
  a 
  rather 
  level 
  

   tract 
  or 
  a 
  gently 
  undulating 
  country, 
  but 
  one 
  intersected 
  by 
  rather 
  deep 
  

   beds 
  of 
  streams, 
  in 
  the 
  banks 
  of 
  which 
  it 
  may 
  usually 
  be 
  seen 
  exposed. 
  

   On 
  the 
  banks 
  of 
  the 
  Irrawadi, 
  however, 
  around 
  Sitsyahn 
  it 
  is 
  unusually 
  

   well 
  exposed, 
  and 
  though 
  not 
  very 
  distinctly 
  stratified, 
  yet 
  the 
  immense 
  

   thickness 
  of 
  it 
  is 
  clearly 
  seen. 
  As 
  the 
  Nummulitics 
  on 
  which 
  this 
  

   group 
  rests, 
  do 
  not 
  come 
  down 
  to 
  the 
  river 
  at 
  this 
  spot, 
  and 
  it 
  is 
  

   nowhere 
  else 
  so 
  well 
  displayed, 
  no 
  estimate 
  can 
  be 
  formed 
  of 
  the 
  entire 
  

   thickness 
  of 
  this 
  lower 
  division 
  of 
  the 
  group 
  ; 
  but 
  I 
  think 
  that 
  close 
  

   on 
  four 
  hundred 
  feet 
  are 
  here 
  seen, 
  and 
  probably 
  twice 
  that 
  amount 
  

   would 
  not 
  be 
  an 
  overestimate 
  for 
  the 
  entire 
  thickness 
  of 
  this 
  divi- 
  

   l 
  ( 
  269 
  ) 
  

  

  