﻿454 
  ME. 
  S. 
  S. 
  BTJCKHAX 
  OX 
  THE 
  

  

  III. 
  The 
  Dorset-Somerset 
  District 
  (south 
  of 
  trie 
  Mendips). 
  

  

  TJie 
  Yeovil 
  Sands. 
  — 
  These 
  may 
  be 
  said 
  to 
  average 
  150 
  feet 
  in 
  

   thickness, 
  and 
  are 
  fine, 
  yellow, 
  micaceous 
  sands 
  with 
  frequent 
  bands 
  

   of 
  sand-rock. 
  They 
  rest 
  on 
  a 
  bed 
  of 
  marl 
  and 
  clay 
  containing 
  

   Lytoceras 
  jurense, 
  Lytoc. 
  Germaini 
  ?, 
  Lytoc. 
  rubescens 
  ?, 
  Pelecoceras 
  

   serrodens, 
  Oxy 
  notice 
  ras 
  discoides, 
  Hammatoceras 
  ihsigne, 
  Grammoceras 
  

   dispansum, 
  fragment, 
  Grammoceras 
  striatulum, 
  fragment, 
  Gramm. 
  sp. 
  

   (White 
  Lackington). 
  In 
  the 
  yellow 
  sands 
  are 
  found 
  Dumortieria 
  

   rJiodanica, 
  fragments 
  (Ham 
  Hill). 
  Higher 
  up 
  we 
  meet 
  with 
  about 
  

   50 
  feet 
  of 
  fine 
  sandy 
  freestone 
  — 
  a 
  mass 
  of 
  comminuted 
  shells 
  — 
  with 
  

   Rhyneh. 
  cynocephala 
  or 
  Beneckei. 
  Layers 
  of 
  sand 
  and 
  coarser 
  free- 
  

   stone 
  cover 
  this 
  for 
  some 
  thirty 
  feet 
  ; 
  and 
  these, 
  again, 
  are 
  capped 
  

   by 
  ten 
  feet 
  of 
  fine 
  yellow 
  sands 
  (Ham 
  Hill). 
  These 
  freestone 
  and 
  

   higher 
  beds 
  are 
  probably 
  represented 
  round 
  Bradford 
  Abbas, 
  Stoford, 
  

   &c. 
  by 
  bands 
  of 
  sandstone 
  sometimes 
  containing 
  a 
  mass 
  of 
  com- 
  

   minuted 
  shells 
  (see 
  Section 
  VIII.). 
  In 
  these 
  rock-bands 
  Gramm. 
  

   mactra, 
  Dumortieria 
  Moorei, 
  Bum. 
  subundulata, 
  &c. 
  have 
  been 
  

   obtained. 
  The 
  topmost 
  bed 
  of 
  the 
  sand-series 
  in 
  this 
  district 
  is 
  a 
  

   hard 
  blue-centred 
  stone, 
  the 
  " 
  Dew-bed 
  " 
  of 
  Bradford 
  Abbas. 
  

  

  At 
  Broad 
  Windsor, 
  Stoke 
  Knap, 
  and 
  other 
  places, 
  at 
  the 
  upper 
  

   parts 
  of 
  the 
  sand-series, 
  are 
  sandy 
  grits 
  containing 
  Lioc. 
  opalinum, 
  

   Terebratula 
  infraoolithica, 
  Rhynclionella 
  cynocephala, 
  Waldheimia 
  

   BlaJcei, 
  &c. 
  These 
  sandy 
  grits 
  may 
  possibly 
  be 
  partly 
  on 
  the 
  same 
  

   horizon 
  and 
  partly 
  on 
  a 
  higher 
  horizon 
  than 
  the 
  Ham-Hill 
  stone. 
  

  

  At 
  Down 
  Cliff, 
  near 
  Seatown, 
  the 
  yellow 
  sands 
  repose 
  on 
  a 
  

   bluish 
  marl 
  passing 
  into 
  micaceous 
  clay. 
  There 
  seemed 
  to 
  be 
  no 
  

   fossil-bed 
  at 
  the 
  junction, 
  and 
  the 
  blue 
  marl 
  appeared 
  barren. 
  Not 
  

   improbably 
  the 
  Striatulum-beds 
  may 
  be 
  found 
  in 
  this 
  blue 
  clay, 
  

   possibly 
  near 
  its 
  base. 
  If 
  so, 
  this 
  would 
  be 
  a 
  very 
  important 
  point. 
  

   At 
  Burton 
  Bradstock 
  about 
  150 
  feet 
  of 
  yellow 
  sand 
  is 
  exposed 
  in 
  a 
  

   fine 
  cliff. 
  From 
  fallen 
  blocks 
  Gramm. 
  mactra, 
  Gramm. 
  aalense, 
  and 
  

   Catulloceras 
  Dumortieri 
  were 
  obtained. 
  In 
  the 
  road-cutting 
  on 
  the 
  

   top 
  of 
  the 
  cliff 
  the 
  sand-rock 
  bands 
  of 
  the 
  upper 
  ten 
  feet 
  of 
  the 
  sands 
  

   are 
  characterized 
  by 
  Lioceras 
  opalinum 
  ; 
  so 
  also 
  is 
  the 
  lowest 
  bed 
  of 
  

   limestone. 
  

  

  Prom 
  the 
  analysis 
  of 
  the 
  various 
  sand-deposits 
  it 
  will 
  be 
  seen 
  

   that 
  none 
  of 
  the 
  different 
  districts 
  contain 
  the 
  same 
  Ammonite- 
  

   fauna. 
  In 
  every 
  district— 
  I. 
  A 
  & 
  B, 
  II. 
  , 
  III. 
  — 
  the 
  Ammonites 
  

   which 
  characterize 
  the 
  sands 
  are 
  not 
  only 
  specifically, 
  but 
  often 
  

   generically, 
  distinct 
  from 
  those 
  of 
  the 
  others. 
  If 
  we 
  now 
  go 
  back 
  

   to 
  the 
  first 
  district, 
  and 
  examine 
  the 
  strata 
  which 
  there 
  repose 
  upon 
  

   the 
  sands 
  — 
  that 
  is, 
  if 
  we 
  examine 
  the 
  so-called 
  Cephalopoda-bed 
  — 
  we 
  

   shall 
  be 
  able 
  to 
  find 
  out 
  the 
  exact 
  explanation 
  of 
  what 
  these 
  various 
  

   Ammonites 
  indicate. 
  

  

  The 
  Cephalopoda-bed 
  of 
  Gloucestershire 
  may 
  be 
  said 
  to 
  be 
  fully 
  

   developed 
  only 
  between 
  the 
  south 
  side 
  of 
  the 
  Stroud 
  valley 
  and 
  

   "Wotton-under-Edge 
  inclusive. 
  It 
  consists 
  of 
  brown 
  marls 
  with 
  

   dark-brown 
  grains, 
  separated 
  at 
  intervals 
  by 
  layers 
  of 
  hardened 
  

   oolitic 
  stone. 
  The 
  thickness 
  of 
  the 
  series 
  varies 
  from 
  about 
  eight 
  

  

  