﻿ANNIVERSARY 
  ADDRESS 
  OF 
  THE 
  PRESIDENT. 
  211 
  

  

  only 
  genus 
  out 
  of 
  the 
  21 
  that 
  is 
  represented 
  by 
  so 
  many 
  as 
  5 
  species. 
  

   The 
  Oxford 
  Clay 
  and 
  Corallian 
  beds 
  arc 
  allied 
  through 
  9 
  genera 
  and 
  

   14 
  species, 
  and 
  3 
  species 
  range 
  into 
  the 
  Kimmeridge 
  Clay, 
  viz. 
  Tri- 
  

   gonia 
  clauellata, 
  Jlodiola 
  bipartita, 
  and 
  Oardium 
  striatulum. 
  There 
  

   is 
  an 
  estuarine 
  element 
  in 
  this 
  horizon, 
  shown 
  by 
  a 
  certain 
  facies 
  

   in 
  the 
  Mollusca, 
  and 
  the 
  genera 
  possessing 
  this 
  character 
  are 
  the 
  

   most 
  numerously 
  represented 
  — 
  Gorbula 
  3 
  species, 
  Cyrma 
  6, 
  Pota- 
  

   momya 
  3, 
  Uaio 
  1. 
  This 
  is 
  more 
  evident 
  in 
  the 
  Dimyarian 
  than 
  the 
  

   Monomyarian 
  genera 
  ; 
  it 
  is 
  equally 
  manifest 
  in 
  the 
  Gasteropoda, 
  

   Cerithium, 
  Hydrobia, 
  Littorina, 
  Neritina, 
  Jlelania, 
  and 
  Valvata 
  

   being 
  suggestive 
  of 
  estuarine 
  conditions. 
  In 
  Scotland, 
  at 
  Loch 
  

   Staffin 
  (Isle 
  of 
  Skye) 
  an 
  estuarine 
  condition 
  was 
  long 
  ago 
  deter- 
  

   mined 
  by 
  Prof. 
  Forbes 
  *. 
  In 
  his 
  paper 
  Forbes 
  speaks 
  of 
  the 
  Staffin 
  

   area 
  as 
  follows: 
  — 
  "The 
  succession 
  of 
  events 
  indicated 
  by 
  the 
  section 
  

   I 
  have 
  described 
  is 
  of 
  no 
  small 
  interest, 
  when 
  considered 
  in 
  its 
  

   bearing 
  on 
  the 
  physical 
  geography 
  of 
  our 
  area 
  during 
  the 
  Oolitic 
  

  

  epochs 
  But 
  at 
  the 
  termination 
  of 
  the 
  deposition 
  of 
  the 
  

  

  middle 
  oolitic 
  strata, 
  we 
  have 
  indications 
  of 
  most 
  important 
  changes, 
  

   and 
  of 
  the 
  conversion 
  of 
  the 
  bed 
  of 
  the 
  Hebridean 
  oolitic 
  sea 
  into 
  

   an 
  estuarine 
  and 
  terrestrial 
  area, 
  which 
  after 
  a 
  considerable 
  lapse 
  

   of 
  time 
  became 
  submerged 
  under 
  oceanic 
  conditions 
  and 
  had 
  a 
  new 
  

   series 
  of 
  marine 
  strata 
  deposited 
  upon 
  it 
  " 
  (Joe. 
  tit. 
  p. 
  108). 
  

  

  Gasteropoda. 
  — 
  Only 
  10 
  genera 
  and 
  17 
  species 
  occur, 
  of 
  which 
  9 
  

   species 
  are 
  confined 
  to 
  the 
  Oxford 
  Clay; 
  and 
  3 
  genera 
  and 
  4 
  

   species 
  unite 
  the 
  Kellaways 
  below 
  with 
  this 
  horizon. 
  The 
  purely 
  

   Oxford-Oolite 
  species 
  are 
  Cerithium 
  Damonis, 
  Leptoxis 
  trochiformis, 
  

   Littorina 
  Meriani, 
  Melania 
  inermis, 
  Neritina 
  arata, 
  Paludina 
  scotica, 
  

   Pleurotomaria 
  amphiccelia 
  , 
  P. 
  Jliinsteri, 
  and 
  Valvata 
  prcecursor. 
  

   These 
  restricted 
  forms, 
  as 
  in 
  almost 
  ever}- 
  case 
  through 
  the 
  Jurassic 
  

   deposits, 
  occur 
  only 
  in 
  single 
  species. 
  Pleurotomaria 
  reticulata 
  is 
  

   the 
  only 
  species 
  of 
  Gasteropod 
  out 
  of 
  the 
  17 
  that 
  passes 
  from 
  the 
  

   Oxford 
  Clay 
  to 
  the 
  Corallian 
  beds. 
  Thus 
  the 
  Oxford 
  Clay 
  Gastero- 
  

   poda 
  are 
  of 
  specific 
  value 
  ; 
  but, 
  as 
  in 
  the 
  great 
  argillaceous 
  groups 
  

   from 
  the 
  Lias 
  up 
  to 
  and 
  including 
  the 
  Kimmeridge 
  Clay, 
  the 
  mass 
  

   of 
  the 
  species 
  belong 
  to 
  the 
  Lamellibranchiata. 
  The 
  extreme 
  poverty 
  

   of 
  species 
  is 
  shown 
  by 
  the 
  following 
  figures 
  for 
  the 
  10 
  genera 
  : 
  — 
  

  

  Alaria, 
  Littorina, 
  Pleurotomaria, 
  each 
  possess 
  3 
  species 
  = 
  9 
  

  

  rTeritina 
  possesses 
  2 
  ,, 
  = 
  2 
  

  

  Cerithium, 
  Leptoxis, 
  Hydrobia, 
  ITelania, 
  Palu- 
  

   dina, 
  and 
  Yalvata 
  each 
  possess 
  1 
  „ 
  =6 
  

  

  17 
  

  

  Cephalopoda. 
  Ammonites. 
  — 
  No 
  less 
  than 
  45 
  species 
  of 
  Ammo- 
  

   nites 
  occur 
  in 
  the 
  Oxford 
  Clay, 
  11 
  of 
  which 
  pass 
  to 
  the 
  succeeding 
  

   Coralline 
  Oolite 
  and 
  4 
  to 
  the 
  Kimmeridge 
  Clay 
  ; 
  20 
  species 
  ranged 
  

   from 
  the 
  Kellaways 
  Eock 
  below. 
  The 
  special 
  Ammonite 
  fauna 
  is 
  18 
  

  

  * 
  Quart. 
  Journ. 
  Geol. 
  Soc. 
  vol. 
  vii. 
  pp. 
  104-113. 
  

  

  2 
  2 
  

  

  