﻿68 
  THEOBALD 
  : 
  GEOLOGY 
  OF 
  PEGU, 
  

  

  S 
  U 
  g. 
  Crocodilus. 
  

  

  Tapir.* 
  Leptorhynchus. 
  

  

  Ox. 
  Em 
  ys- 
  

  

  Deer. 
  Trionyx. 
  

  

  Antelope. 
  Colossochelys. 
  

  

  Silty 
  underclay. 
  — 
  Below 
  the 
  last-described 
  sand 
  occurs 
  a 
  deposit 
  of 
  

   very 
  uniform 
  character, 
  which 
  from 
  its 
  relation 
  to 
  the 
  most 
  characteristic 
  

   member 
  of 
  the 
  group, 
  may 
  be 
  termed 
  the 
  under-clay. 
  This 
  bed 
  is 
  a 
  clay 
  

   of 
  a 
  very 
  uniform 
  silty 
  character, 
  and 
  appears 
  to 
  have 
  been 
  deposited 
  under 
  

   tranquil 
  conditions 
  ; 
  as 
  beyond 
  a 
  very 
  few 
  small 
  pebbles, 
  which 
  are 
  more- 
  

   over 
  very 
  rare, 
  no 
  extraneous 
  ingredients 
  have 
  been 
  detected 
  by 
  me 
  in 
  the 
  

   deposit. 
  I 
  So 
  not 
  remember 
  ever 
  detecting 
  either 
  a 
  fossil 
  b 
  one 
  or 
  piece 
  

   of 
  wood 
  in 
  this 
  bed 
  ; 
  and 
  as 
  it 
  is 
  well 
  and 
  largely 
  exposed 
  within 
  the 
  

   area 
  of 
  the 
  fossil-wood 
  group, 
  it 
  is 
  pretty 
  certain 
  that 
  no 
  such 
  remains 
  

   occur 
  in 
  it. 
  This 
  is 
  the 
  more 
  singular, 
  from 
  the 
  abundance 
  of 
  silicified 
  

   wood 
  in 
  the 
  sand 
  immediately 
  above 
  it 
  ; 
  and 
  I 
  am 
  inclined 
  to 
  think, 
  that 
  

   this 
  deficiency 
  may 
  possibly 
  be 
  due 
  to 
  the 
  absence 
  of 
  those 
  conditions, 
  

   during 
  its 
  accumulation, 
  to 
  which 
  the 
  preservation 
  of 
  the 
  wood 
  in 
  the 
  

   newer 
  deposit 
  was 
  due 
  ; 
  or, 
  in 
  other 
  words, 
  that 
  the 
  means 
  of 
  rapid 
  silici- 
  

   fication 
  were 
  not 
  then 
  present, 
  as 
  during 
  a 
  later 
  period. 
  Silicified 
  wood 
  

   occurs 
  sparingly 
  in 
  beds 
  below 
  this, 
  which, 
  on 
  the 
  supposition 
  of 
  the 
  silica 
  

   being 
  supplied 
  from 
  springs 
  dependent 
  on 
  volcanic 
  action 
  in 
  the 
  neigh- 
  

   bourhood, 
  would 
  seem 
  to 
  imply 
  that 
  the 
  deposition 
  of 
  the 
  bed 
  of 
  silty 
  

   underclay 
  marked 
  a 
  period 
  of 
  abeyance 
  of 
  volcanic 
  action, 
  during 
  which 
  

   the 
  supply 
  of 
  silica 
  was 
  arrested, 
  and 
  wherein 
  consequently 
  no 
  silicified 
  

   trunks 
  were 
  preserved. 
  What 
  few 
  quartz 
  pebbles 
  occur, 
  are 
  found 
  asso- 
  

   ciated 
  with 
  little 
  strings 
  of 
  sand 
  of 
  very 
  insignificant 
  extent. 
  The 
  

   thickness 
  of 
  this 
  bed 
  may 
  be 
  forty 
  feet 
  or 
  thereabouts 
  ; 
  and 
  it 
  is 
  per- 
  

   haps 
  nowhere 
  better 
  seen 
  than 
  South 
  of 
  Thanat-ua 
  between 
  Alan-mio 
  

  

  * 
  The 
  Tapir 
  is 
  unknown 
  to 
  the 
  well-investigated 
  Sivalik 
  Fauna, 
  as 
  Falconer 
  observes. 
  — 
  

   " 
  The 
  Tapir 
  alone 
  of 
  the 
  large 
  existing 
  Pachydermata 
  being 
  without 
  a 
  representative," 
  

   (Falconer's 
  Palaeontological 
  Memoirs, 
  Vol. 
  1, 
  page 
  296). 
  It 
  may 
  have 
  been 
  therefore 
  

   erroneously 
  determined 
  by 
  Mr. 
  Clift, 
  as 
  Falconer 
  makes 
  no 
  mention 
  of 
  it 
  among 
  the 
  

   Ava 
  fossils 
  which 
  he 
  examined 
  and 
  described. 
  

  

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  ) 
  

  

  