﻿II 
  6 
  PKOCEEDLNGS 
  OF 
  THE 
  GEOLOGICAL 
  SOCIETY. 
  

  

  divisions 
  form 
  the 
  Lower 
  Calcareous 
  Grit. 
  The 
  succeeding 
  series 
  

   consist 
  of 
  Oolites 
  and 
  Marls, 
  which 
  include 
  the 
  " 
  Osmington 
  Oolite" 
  

   or 
  the 
  " 
  Trigonia-be&a" 
  with 
  T. 
  clavellata 
  and 
  Cidar 
  is 
  florig 
  em/ma. 
  

   Above 
  the 
  main 
  limestones 
  at 
  Weymouth 
  succeeds 
  40 
  feet 
  of 
  clay 
  (the 
  

   " 
  Sandsfoot 
  Clay") 
  overlain 
  by 
  ferruginous 
  sands 
  and 
  grits 
  with 
  large 
  

   spongious 
  growths, 
  containing 
  Lima 
  pectiniformis, 
  Cidaris 
  florigemma, 
  

   Lingula 
  ovalis, 
  Littorina 
  muricata, 
  and 
  Astarte 
  supracorallina. 
  These 
  

   are 
  well 
  shown 
  at 
  Abbotsbury. 
  A 
  peculiar 
  Upper 
  Coral 
  Rag 
  is 
  

   developed 
  above 
  these 
  grits 
  at 
  Eingstead 
  Bay 
  and 
  below 
  the 
  Kim- 
  

   meridge 
  Passage-beds. 
  The 
  Abbotsbury 
  Ironstone 
  is 
  upon 
  a 
  higher 
  

   horizon. 
  No 
  true 
  Coral-reef 
  occurs 
  within 
  this 
  area 
  ; 
  but 
  the 
  

   changes 
  in 
  the 
  character 
  of 
  the 
  deposits, 
  on 
  the 
  whole 
  thick, 
  are 
  

   exceptionally 
  numerous. 
  

  

  North 
  Dorset. 
  — 
  The 
  Corallian 
  series 
  varies 
  considerably 
  in 
  this 
  

   area, 
  the 
  Lower 
  Calcareous 
  Grit 
  being 
  scarcely 
  represented 
  in 
  the 
  

   southern 
  part 
  — 
  Marls, 
  and 
  Pisolites 
  replacing 
  the 
  Grits, 
  much 
  false- 
  

   bedding 
  succeeding 
  these. 
  In 
  the 
  northern 
  portion 
  the 
  Lower 
  Cal- 
  

   careous 
  Grit 
  is 
  well 
  developed, 
  especially 
  near 
  Cucklington 
  and 
  Gil- 
  

   lingham, 
  where 
  they 
  gradually 
  merge 
  into 
  the 
  Oxford 
  Clay. 
  The 
  

   Limestones 
  also 
  prevail, 
  but 
  are 
  impure 
  in 
  character 
  ; 
  at 
  Mappowder 
  

   and 
  Marnhull 
  the 
  false-bedded 
  series 
  are 
  economically 
  used, 
  being 
  

   burnt 
  for 
  lime. 
  

  

  Wiltshire 
  and 
  Oxfordshire 
  Range. 
  — 
  The 
  Lower 
  Calcareous 
  Grit 
  is 
  

   the 
  most 
  constant 
  member 
  of 
  the 
  many 
  types 
  that 
  occur 
  in 
  this 
  

   long 
  belt 
  of 
  deposits 
  ; 
  the 
  iron-ore 
  beds 
  at 
  Westbury 
  in 
  the 
  

   southern 
  part, 
  like 
  those 
  of 
  Abbotsbury, 
  occupy 
  the 
  extreme 
  top 
  of 
  

   the 
  series. 
  At 
  Steeple-Ashton 
  and 
  Calne 
  the 
  Lower 
  Calcareous 
  Grit 
  

   is 
  well 
  developed 
  ; 
  the 
  chief 
  feature 
  at 
  Calne 
  is 
  the 
  non-development 
  

   of 
  any 
  beds 
  but 
  those 
  containing 
  Cidaris 
  florigemma. 
  

  

  At 
  Highworth 
  the 
  chief 
  feature 
  is 
  the 
  development, 
  below 
  the 
  

   Coral 
  Rag 
  with 
  Cidaris 
  florigemma, 
  of 
  highly 
  fossiliferous 
  limestones 
  

   with 
  Trigonia 
  Meriani, 
  Lima 
  rigida, 
  and 
  Ammonites 
  plicatilis. 
  These 
  

   shell-beds 
  thin 
  out 
  or 
  disappear 
  near 
  Oxford. 
  At 
  Heddington 
  ano- 
  

   ther 
  shell-bed, 
  with 
  abundance 
  of 
  Cidaris 
  florigemma, 
  occurs 
  in 
  the 
  

   Coral 
  -Rag. 
  

  

  The 
  Cambridge 
  Reef. 
  — 
  This 
  remarkable 
  outlier 
  is 
  composed 
  en- 
  

   tirely 
  of 
  the 
  Coral 
  Rag, 
  containing 
  a 
  rich 
  and 
  special 
  fauna, 
  the 
  

   characteristic 
  Cidaris 
  florigemma 
  determining 
  its 
  true 
  character. 
  

   The 
  authors 
  believe 
  the 
  Elsworth 
  rock 
  to 
  be 
  an 
  exceptional 
  develop- 
  

   ment 
  of 
  the 
  Lower 
  Calcareous 
  Grit. 
  The 
  Rev. 
  T. 
  G. 
  Bonney, 
  in 
  

   his 
  'Cambridgeshire 
  Geology,' 
  has 
  carefully 
  described 
  this 
  "reef," 
  

   and 
  gives 
  a 
  list 
  of 
  the 
  characteristic 
  fossils 
  obtained. 
  No 
  less 
  than 
  

   58 
  species 
  are 
  known 
  — 
  Ccelenterata 
  7, 
  Echinodermata 
  7, 
  Annulosa 
  4, 
  

   Brachiopoda 
  1, 
  Pelecypoda 
  23, 
  Gasteropoda 
  11, 
  Cephalopoda 
  5 
  

   species. 
  

  

  The 
  Yorkshire 
  Basin. 
  — 
  The 
  Lower 
  Calcareous 
  Grit 
  is 
  the 
  most 
  

   constantly 
  developed 
  of 
  all 
  the 
  Corallian 
  deposits. 
  In 
  the 
  Howardian 
  

   hills 
  at 
  Grimston 
  and 
  Walton 
  it 
  is 
  about 
  60 
  feet 
  in 
  thickness 
  ; 
  in 
  

   the 
  western 
  and 
  northern 
  hills 
  (Hambleton 
  and 
  Newtondale) 
  it 
  in- 
  

   creases 
  to 
  100 
  feet. 
  The 
  fauna 
  of 
  the 
  Lower 
  Limestone 
  has 
  much 
  

  

  