﻿620 
  PROF. 
  C. 
  LAPWOETH 
  ON 
  THE 
  GIEVAN 
  SUCCESSION. 
  

  

  the 
  Trilobites 
  they 
  have 
  afforded. 
  They 
  consist 
  of 
  pale-blue 
  or 
  

   greyish-green 
  mudstones 
  of 
  the 
  same 
  general 
  type 
  as 
  these 
  at 
  the 
  

   summit 
  of 
  the 
  subgroup 
  ; 
  but 
  they 
  are 
  harder, 
  and 
  often 
  contain 
  a 
  

   a 
  notable 
  proportion 
  of 
  sandy 
  material. 
  

  

  In 
  the 
  section 
  shown 
  upon 
  the 
  burn-side 
  opposite 
  the 
  farmsteading 
  

   of 
  South 
  Thraive 
  Mr. 
  and 
  Mrs. 
  Gray 
  have 
  collected 
  : 
  — 
  

  

  Trinucleus 
  seticornis, 
  His. 
  

   Arupyx 
  rostratus, 
  Sars. 
  

   Solenocaris 
  solenoides, 
  Young. 
  

  

  Dionide 
  Lapworthi, 
  E. 
  Eth.jun. 
  

   Bellerophon 
  bilobatus, 
  Sow. 
  

   Dicellograptus 
  anceps, 
  Nick. 
  

  

  Where 
  the 
  succeeding 
  plantation 
  comes 
  upon 
  the 
  stream-course 
  

   similar 
  beds 
  are 
  seen 
  containing 
  numerous 
  fossil 
  forms. 
  Here 
  I 
  

   have 
  myself 
  distinguished 
  : 
  — 
  

  

  Diplograptus 
  truncatus, 
  Lapw. 
  

   Trinucleus 
  Bucklandi, 
  Barr. 
  

   Illaenus 
  Bowmanni, 
  Salt. 
  

  

  Bellerophon 
  bilobatus, 
  Sow. 
  

  

  trilobatus, 
  Sow. 
  

  

  Holopella 
  obsoleta, 
  Sow. 
  

  

  Midway 
  between 
  Thraive 
  and 
  Drummuck, 
  beds 
  a 
  little 
  lower 
  in 
  

   the 
  succesion 
  are 
  shown. 
  These 
  Mrs. 
  Gray 
  found 
  to 
  be 
  prolific 
  in 
  

   beautifully 
  preserved 
  specimens 
  of 
  

  

  Ampyx 
  rostratus, 
  Sars. 
  | 
  Trinucleus 
  seticornis, 
  His. 
  

  

  At 
  the 
  farm 
  of 
  Drummuck 
  itself 
  the 
  Trinucleus-'beds 
  are 
  admirably 
  

   shown 
  in 
  a 
  small 
  stream 
  running 
  parallel 
  to 
  the 
  roadway 
  to 
  the 
  

   south 
  of 
  the 
  steading. 
  Here 
  fossils 
  are 
  not 
  so 
  numerous 
  as 
  in 
  the 
  

   former 
  localities 
  cited 
  ; 
  but 
  occasional 
  Brachiopoda 
  are 
  found 
  beauti- 
  

   fully 
  preserved. 
  

  

  The 
  oldest 
  strata 
  of 
  the 
  Drummuck 
  Beds 
  seen 
  in 
  this 
  locality 
  are 
  

   exhibited 
  in 
  a 
  small 
  stream 
  crossing 
  the 
  roadway 
  a 
  quarter 
  of 
  a 
  mile 
  

   south 
  of 
  the 
  farmhouse, 
  and 
  again 
  in 
  a 
  small 
  quarry 
  near 
  the 
  head 
  

   of 
  Drummuck 
  Burn 
  itself. 
  In 
  both 
  these 
  localities 
  we 
  recognize 
  

   the 
  greenish 
  thin-bedded 
  lower 
  shales 
  of 
  Quarrel 
  Hill, 
  and 
  identify 
  

   within 
  them 
  an 
  occasional 
  fossil. 
  

  

  Westward, 
  the 
  Trinucleus-Btrbta, 
  are 
  buried 
  beneath 
  recent 
  accu- 
  

   mulations 
  and 
  surface-soil; 
  and, 
  except 
  in 
  two 
  small 
  exposures, 
  ODe 
  

   at 
  the 
  little 
  pond 
  near 
  the 
  toll-bar 
  at 
  Trochraive, 
  and 
  another 
  on 
  the 
  

   north-west 
  corner 
  of 
  the 
  enigmatical 
  rock-area 
  of 
  Craighead 
  Hill, 
  

   nothing 
  further 
  is 
  known 
  of 
  their 
  extension 
  in 
  that 
  direction. 
  

  

  This 
  prolific 
  subdivision 
  of 
  Trinucleus-miidstones 
  and 
  shales 
  is 
  

   denominated 
  the 
  Drummuck 
  Beds, 
  after 
  the 
  name 
  of 
  the 
  farm 
  in 
  

   the 
  neighbourhood 
  of 
  which 
  its 
  strata 
  are. 
  most 
  effectively 
  displayed. 
  

   The 
  subdivision 
  forms 
  the 
  highest 
  member 
  of 
  the 
  Graptolitic 
  flag- 
  

   stone 
  or 
  Ardmillan 
  group 
  of 
  our 
  Girvan 
  succession, 
  being 
  succeeded 
  

   by 
  the 
  basal 
  zone 
  of 
  a 
  superior 
  group 
  of 
  rocks, 
  totally 
  distinct 
  both 
  

   in 
  lithological 
  features 
  and 
  in 
  organic 
  remains. 
  Before 
  proceeding 
  

   to 
  notice 
  these 
  higher 
  strata, 
  it 
  will 
  be 
  advisable 
  to 
  give 
  a 
  short 
  

   summary 
  of 
  the 
  several 
  bands 
  of 
  rock 
  that 
  constitute 
  our 
  complete 
  

   Ardmillan 
  group 
  as 
  we 
  now 
  understand 
  it, 
  together 
  with 
  the 
  names 
  

   of 
  the 
  several 
  localities 
  where 
  their 
  strata 
  are 
  typically 
  laid 
  open 
  for 
  

   investigation 
  : 
  — 
  

  

  

  

  