﻿DEVOJs 
  T 
  0-SILTJEIAN- 
  FORMATION. 
  205 
  

  

  grounds, 
  but 
  towards 
  the 
  south 
  merging 
  into 
  the 
  waters 
  of 
  the 
  open 
  

   sea, 
  in 
  which 
  were 
  being 
  simultaneously 
  formed 
  over 
  the 
  Devon- 
  

   shire 
  area 
  the 
  fossiliferous 
  Middle 
  and 
  Lower 
  Devonian 
  beds, 
  with 
  

   their 
  numerous 
  marine 
  forms 
  of 
  life. 
  

  

  No 
  one 
  has 
  ever 
  been 
  able 
  to 
  discover 
  any 
  traces 
  of 
  a 
  barrier 
  of 
  

   older 
  rocks 
  which 
  could 
  be 
  supposed 
  to 
  have 
  separated 
  the 
  Devonian 
  

   region 
  from 
  that 
  lying 
  to 
  the 
  north 
  of 
  the 
  Severn 
  and 
  along 
  the 
  

   Wye; 
  and 
  I 
  do 
  not 
  believe 
  that 
  any 
  existed. 
  On 
  the 
  other 
  hand, 
  

   the 
  lower 
  beds 
  of 
  the 
  series 
  contain 
  Lingulce 
  in 
  abundance, 
  as, 
  for 
  

   instance, 
  at 
  Bedw 
  Llewd, 
  in 
  Brecon 
  — 
  and 
  the 
  upper 
  beds 
  Serpulce, 
  as 
  

   in 
  Caldy 
  Island. 
  The 
  red 
  colour 
  of 
  the 
  strata 
  may 
  be 
  due 
  to 
  depo- 
  

   sition 
  either 
  within 
  the 
  bounds 
  of 
  an 
  estuary 
  or 
  in 
  those 
  of 
  a 
  lake 
  ; 
  and 
  

   in 
  Belgium, 
  as 
  Professor 
  Dewalque 
  has 
  pointed 
  out 
  *, 
  red 
  marls 
  and 
  

   sandstones 
  occur, 
  separating 
  large 
  masses 
  of 
  marine 
  limestones 
  of 
  

   the 
  Devonian 
  period 
  f. 
  

  

  The 
  difference 
  in 
  character 
  of 
  the 
  beds 
  in 
  Devonshire 
  on 
  the 
  one 
  

   hand, 
  and 
  in 
  South 
  Wales 
  &c. 
  on 
  the 
  other, 
  need 
  offer 
  no 
  impedi- 
  

   ment 
  to 
  the 
  acceptance 
  of 
  my 
  view, 
  because 
  the 
  original 
  horizontal 
  

   distance 
  was 
  very 
  much 
  greater 
  than 
  at 
  present. 
  In 
  order 
  to 
  find 
  

   this 
  out, 
  we 
  must 
  restore 
  all 
  the 
  highly 
  inclined 
  strata 
  of 
  South 
  

   Wales 
  and 
  the 
  rocks 
  under 
  the 
  Severn, 
  with 
  their 
  numerous 
  flexures 
  

   to 
  the 
  horizontal 
  position 
  ; 
  and 
  by 
  this 
  means 
  the 
  horizontal 
  distance 
  

   will 
  be 
  increased 
  by 
  perhaps 
  one 
  third. 
  This 
  would 
  allow 
  space 
  for 
  

   the 
  gradual 
  changes 
  of 
  character 
  observable 
  between 
  the 
  beds 
  of 
  

   North 
  Devon 
  and 
  their 
  representatives 
  in 
  South 
  Wales, 
  Hereford, 
  &c. 
  

  

  On 
  all 
  these 
  grounds 
  I 
  venture 
  to 
  recommend 
  the 
  adoption 
  of 
  the 
  

   term 
  " 
  Estuarine 
  Devonian 
  " 
  for 
  the 
  series 
  lying 
  above 
  the 
  Passage- 
  

   beds 
  in 
  the 
  country 
  bordering 
  the 
  Wye, 
  the 
  Mon, 
  and 
  the 
  Usk. 
  

  

  (d) 
  Ireland, 
  South. 
  — 
  " 
  Dingle 
  beds 
  and 
  Glengariff 
  Grits 
  and 
  

   Slates" 
  (Jukes). 
  A 
  series 
  of 
  grey, 
  green, 
  and 
  purple 
  grits 
  and 
  con- 
  

   glomerates, 
  with 
  intervening 
  red, 
  grey, 
  and 
  green 
  slates 
  of 
  great 
  

   thickness 
  (estimated 
  at 
  from 
  10,000 
  to 
  12,000 
  feet), 
  passing 
  downwards 
  

   into 
  the 
  Upper 
  Silurian 
  beds 
  in 
  the 
  Dingle 
  promontory, 
  and 
  uncon- 
  

   formably 
  overlain 
  either 
  by 
  the 
  Old 
  Red 
  Sandstone 
  or 
  (in 
  the 
  ab- 
  

   sence 
  of 
  that 
  formation, 
  owing 
  to 
  conformable 
  overlap) 
  by 
  the 
  Lower 
  

   Carboniferous 
  beds 
  ±. 
  The 
  only 
  fossils 
  they 
  have 
  yielded 
  are 
  stems 
  

   of 
  plants 
  and 
  fucoidal 
  markings. 
  The 
  plants 
  are 
  allied 
  to 
  Carboni- 
  

   ferous 
  forms 
  (vascular 
  Cryptogams). 
  

  

  These 
  beds 
  are 
  placed 
  by 
  Murchison 
  in 
  the 
  "Lower 
  Devonian 
  

   series," 
  a 
  very 
  close 
  approximation 
  to 
  what 
  I 
  conceive 
  to 
  be 
  their 
  true 
  

   position 
  ; 
  but 
  if 
  (as 
  I 
  suppose) 
  they 
  represent 
  the 
  Foreland 
  Grits 
  and 
  

   Slates 
  of 
  North 
  Devon 
  and 
  the 
  " 
  Passage-beds" 
  of 
  South 
  Wales 
  &c, 
  

   they 
  occupy 
  a 
  position 
  just 
  below 
  the 
  fossiliferous 
  Lower 
  Devonian 
  

   beds 
  of 
  which 
  the 
  " 
  Lynton 
  Slates 
  and 
  Limestones 
  " 
  are 
  the 
  repre- 
  

   sentatives. 
  After 
  an 
  examination 
  of 
  the 
  fine 
  sections 
  at 
  the 
  extre- 
  

  

  * 
  Brit. 
  Assoc. 
  Eep. 
  1877, 
  Trans. 
  Sect. 
  p. 
  69. 
  

  

  t 
  Namely, 
  the 
  Calcaire 
  de 
  Givet 
  from 
  the 
  Calcaire 
  de 
  Frasne. 
  

  

  \ 
  The 
  evidence 
  for 
  this 
  statement 
  I 
  have 
  given 
  in 
  former 
  papers 
  — 
  Quart. 
  

   Journ. 
  Geol. 
  Soc. 
  vol. 
  xxxv. 
  (1879), 
  and 
  Proc. 
  Roy. 
  Dub. 
  Soe. 
  vol. 
  i. 
  new 
  series 
  

   (1880). 
  

  

  