﻿172 
  PROCEEDINGS 
  OF 
  THE 
  GEOLOGICAL 
  SOCIETY. 
  

  

  scarcely 
  expect 
  to 
  find 
  that 
  the 
  species 
  occupied 
  a 
  given 
  area 
  for 
  

   a 
  long 
  period 
  of 
  time 
  without 
  modification 
  ; 
  hence 
  the 
  6 
  Lower- 
  

   Lias 
  species 
  may 
  have 
  stocked 
  the 
  succeeding 
  Middle 
  and 
  Upper 
  

   deposits. 
  But 
  only 
  one 
  species, 
  N. 
  striatus, 
  is 
  both 
  Lower 
  and 
  Middle 
  

   Lias, 
  and 
  the 
  only 
  two 
  species 
  common 
  to 
  the 
  Middle 
  and 
  Upper 
  

   Lias 
  are 
  N. 
  inornatus 
  and 
  iV. 
  semist?'iatus. 
  

  

  Teuthidce. 
  — 
  This 
  division 
  of 
  the 
  Dibranchiata 
  is 
  but 
  feebly 
  re- 
  

   presented 
  in 
  the 
  Lias. 
  Geoteuthis 
  bollensis 
  is 
  essentially 
  Lower 
  Lias 
  ; 
  

   Beloteuihis 
  Leckenbyi 
  and 
  B. 
  subcostatus 
  are 
  Upper 
  only, 
  and 
  do 
  not 
  

   occur 
  higher. 
  3 
  genera 
  and 
  4 
  species 
  are 
  all 
  that 
  are 
  known. 
  

  

  Belemnitidce. 
  — 
  115 
  species 
  are 
  known 
  to 
  occur 
  in 
  the 
  Jurassic 
  

   rocks 
  of 
  Britain, 
  65 
  of 
  which 
  belong 
  to 
  the 
  three 
  Liassic 
  divisions. 
  

   21 
  occur 
  in 
  the 
  Lower 
  Lias, 
  27 
  in 
  the 
  Middle 
  Lias, 
  and 
  34 
  in 
  

   the 
  Upper. 
  JVot 
  one 
  of 
  the 
  species 
  passes 
  to 
  the 
  Inferior 
  Oolite, 
  

   in 
  any 
  area 
  in 
  Britain, 
  or 
  Europe. 
  7 
  species 
  are 
  common 
  to 
  the 
  

   Lower 
  and 
  Middle 
  Lias 
  ; 
  they 
  are 
  Belemnites 
  calcar, 
  B. 
  clavatus, 
  

   B. 
  longissimus, 
  B. 
  Milleri, 
  B. 
  nitidus, 
  B. 
  penicillatus, 
  and 
  B. 
  virga- 
  

   tus. 
  Only 
  one 
  species, 
  B. 
  Milleri, 
  appears 
  to 
  be 
  present 
  in 
  all 
  three 
  

   divisions 
  of 
  the 
  Lias. 
  

  

  The 
  Lias 
  of 
  Yorkshire 
  through 
  the 
  researches 
  and 
  labours 
  of 
  

   Hunton, 
  Phillips, 
  Simpson, 
  Leckenby, 
  Tate, 
  and 
  Blake 
  have 
  yielded 
  

   a 
  large 
  number 
  of 
  species 
  ; 
  and 
  to 
  no 
  one 
  more 
  than 
  Mr. 
  Simpson 
  

   are 
  we 
  indebted 
  for 
  collecting 
  and 
  describing 
  the 
  species 
  occurring 
  

   in 
  the 
  Lias 
  of 
  Yorkshire. 
  Prof. 
  Phillips's 
  monograph 
  in 
  the 
  Pala3- 
  

   ontographical 
  Society's 
  Memoirs 
  is 
  the 
  only 
  reliable 
  British 
  work 
  

   we 
  possess 
  since 
  the 
  memoir 
  by 
  Miller 
  in 
  the 
  Trans, 
  of 
  the 
  Geol. 
  

   Soc. 
  vol. 
  ii. 
  1829. 
  Simpson's 
  small 
  but 
  valuable 
  work 
  on 
  the 
  Lias 
  

   of 
  Yorkshire 
  describes 
  no 
  less 
  than 
  40 
  species. 
  The 
  close 
  of 
  the 
  

   Lias 
  brought 
  with 
  it 
  a 
  very 
  great 
  diminution 
  of 
  this 
  group 
  of 
  the 
  

   Dibranchiata 
  ; 
  only 
  16 
  species 
  are 
  known 
  in 
  the 
  Inferior 
  Oolite, 
  3 
  

   in 
  the 
  Fuller's 
  Earth, 
  3 
  in 
  the 
  Great 
  Oolite, 
  none 
  either 
  in 
  the 
  Forest 
  

   Marble 
  or 
  Cornbrash, 
  3 
  species 
  in 
  the 
  Kcllaways 
  Bock, 
  13 
  species 
  in 
  

   the 
  Oxford 
  Clay, 
  declining 
  to 
  4 
  species 
  in 
  the 
  Corallian 
  beds, 
  and 
  8 
  in 
  

   the 
  Kimmeridge 
  Clay. 
  No 
  form 
  is 
  known 
  in 
  the 
  Portland 
  Oolite. 
  The 
  

   sudden 
  introduction 
  and 
  development 
  of 
  the 
  BelemnitidEe 
  in 
  the 
  Lias 
  

   calls 
  for 
  and 
  demands 
  much 
  research, 
  the 
  two 
  groups 
  the 
  Ammoni- 
  

   tidas 
  and 
  Belemnitidae 
  having 
  commenced 
  in 
  such 
  numbers, 
  and 
  the 
  

   latter 
  declined 
  so 
  rapidly. 
  

  

  Pisces. 
  — 
  43 
  genera 
  and 
  132 
  species 
  of 
  Fish 
  occur 
  in 
  the 
  three 
  divi- 
  

   sions 
  of 
  the 
  Lias. 
  40 
  genera 
  and 
  106 
  species 
  have 
  been 
  described 
  

   from 
  the 
  Lower 
  Lias, 
  only 
  2 
  genera 
  and 
  2 
  species 
  are 
  known 
  to 
  

   occur 
  in 
  the 
  Middle 
  Lias, 
  and 
  6 
  genera 
  and 
  18 
  species 
  in 
  the 
  Upper. 
  

   With 
  the 
  exception 
  of 
  4 
  genera, 
  Acrodus, 
  Hybodus, 
  Lepidotus, 
  and 
  

   Pholidophorus, 
  which 
  occur 
  in 
  and 
  pass 
  up 
  from 
  the 
  Bhsetic 
  bone-bed, 
  

   all 
  the 
  genera 
  and 
  species 
  enumerated 
  first 
  appeared 
  as 
  denizens 
  of 
  

   the 
  Liassic 
  seas 
  of 
  Britain. 
  I 
  am 
  not 
  aware 
  of 
  any 
  other 
  Bhsetic 
  forms 
  

   passing 
  to 
  the 
  Lower 
  Lias. 
  Their 
  distribution 
  is 
  extremely 
  local 
  ; 
  

   the 
  mass 
  of 
  the 
  species 
  of 
  the 
  Lower 
  Lias 
  have 
  been 
  obtained 
  

   from 
  Lyme 
  Begis, 
  and 
  those 
  occurring 
  in 
  the 
  Upper 
  Lias 
  are 
  chiefly 
  

   from 
  Whitby. 
  The 
  Lower 
  Lias 
  of 
  Lyme 
  Begis 
  has 
  been 
  extensively 
  

  

  