﻿592 
  

  

  PROF. 
  C. 
  LAPWORTH 
  ON 
  THE 
  GIRT 
  AN 
  SUCCESSION. 
  

  

  Fig. 
  15. 
  — 
  Section 
  at 
  Laggan 
  Gill. 
  

  

  E.S.E. 
  | 
  , 
  W.N.VV 
  

  

  

  Ba 
  2 
  . 
  Basal 
  zone 
  of 
  Graptolitic 
  flagstones 
  — 
  soft 
  shales, 
  with 
  Lasio- 
  

  

  graptus, 
  Cryplograptus, 
  Trachyderma, 
  &c. 
  

   Ad 
  2 
  . 
  Balclatchie 
  grits 
  and 
  flagstones. 
  

   • 
  Ad 
  1 
  . 
  Balclatchie 
  mudstones, 
  much 
  broken. 
  

   Ac. 
  Benan 
  Conglomerate. 
  

   Ballantrae 
  Rocks: 
  — 
  

  

  Sy. 
  Syenitic 
  rock. 
  

  

  L. 
  Calcareous 
  rock 
  shattered 
  and 
  altered. 
  

  

  * 
  Altered 
  breccias. 
  

  

  difficulty. 
  This 
  is 
  nevertheless 
  by 
  no 
  means 
  the 
  case 
  with 
  the 
  

   peculiar 
  transitional 
  zone 
  at 
  the 
  summit 
  of 
  the 
  group, 
  which 
  occurs 
  

   here 
  in 
  its 
  normal 
  position 
  at 
  the 
  base 
  of 
  the 
  Graptolitic 
  flagstone 
  

   series. 
  Its 
  strata, 
  although 
  greatly 
  folded, 
  are 
  crowded 
  with 
  the 
  

   characteristic 
  Graptolites 
  and 
  Brachiopoda 
  in 
  a 
  state 
  of 
  exquisite 
  

   pres< 
  rvation. 
  

  

  The 
  commonest 
  forms 
  are 
  Cryptograptus 
  triconns, 
  Carr., 
  Lasio- 
  

   graptus 
  Harhnessi, 
  Nich., 
  Climacograptus 
  bicornis, 
  Hall, 
  0. 
  Scharen- 
  

   bergi, 
  Lapw., 
  Diplograptus 
  rugosus, 
  Emm., 
  1). 
  foliaceus, 
  Murch., 
  

   together 
  with 
  species 
  of 
  Trachyderma, 
  Cy 
  there, 
  &c. 
  &c. 
  

  

  This 
  Balclatchie 
  hand 
  is 
  prolonged 
  to 
  the 
  south-eastward 
  of 
  

   Laggan 
  Gill, 
  along 
  the 
  northern 
  margin 
  of 
  the 
  conglomeratic 
  area 
  

   of 
  Dinvin 
  and 
  Dalfask, 
  into 
  the 
  neighbourhood 
  of 
  liarbae 
  and 
  Tra- 
  

   mitchell, 
  where 
  it 
  has 
  been 
  noticed 
  already. 
  

  

  0. 
  Dow 
  Hill.— 
  Upon 
  the 
  inlier 
  of 
  Dow 
  Hill 
  (see 
  map, 
  PI. 
  XXV.) 
  

   the 
  Balclatchie 
  mudstones, 
  which 
  there 
  repose 
  in 
  their 
  natural 
  place 
  

   upon 
  the 
  Benan 
  Conglomerate, 
  have 
  yielded 
  to 
  the 
  persevering 
  re- 
  

   searches 
  of 
  Mr. 
  Robert 
  Gray 
  a 
  large 
  suite 
  of 
  fossils, 
  identical 
  with 
  

   those 
  of 
  the 
  typical 
  locality 
  and 
  of 
  Ardmillan 
  Braes. 
  The 
  same 
  

   Balclatchie 
  zone 
  is 
  met 
  with 
  in 
  a 
  corresponding 
  position 
  at 
  several 
  

   spots 
  on 
  both 
  margins 
  of 
  the 
  Pinmore 
  synclinal, 
  while 
  the 
  overlying 
  

   transitional 
  seam 
  (Ba 
  n 
  ) 
  occurs 
  at 
  various 
  localities 
  within 
  the 
  same 
  

   area, 
  and 
  is 
  abundantly 
  fossiliferous. 
  It 
  is 
  needless 
  to 
  enter 
  into 
  

   further 
  details 
  of 
  these 
  exposures. 
  

  

  Summary. 
  — 
  The 
  strata 
  which 
  next 
  fall 
  to 
  be 
  described 
  are 
  the 
  

   Graptolitic 
  Flagstones 
  and 
  Shales 
  of 
  Ardwell 
  and 
  Penwhapple. 
  

   These, 
  however, 
  are 
  so 
  distinct 
  in 
  their 
  lithological 
  and 
  paheonto- 
  

   logical 
  features 
  from 
  the 
  rocks 
  already 
  noticed, 
  that 
  it 
  is 
  impossible 
  

   to 
  place 
  them 
  in 
  the 
  same 
  systematic 
  group. 
  We 
  are 
  therefore 
  

  

  