﻿R. 
  P. 
  TOMES 
  ON 
  LOWER-OOLITE 
  MADREPORARIA. 
  429 
  

  

  and 
  at 
  the 
  Horse 
  Pools, 
  near 
  Gloucester, 
  at 
  which 
  places 
  it 
  is 
  not 
  

   uncommon. 
  

  

  Chorisastrjea 
  gregaria, 
  M'Coy, 
  sp. 
  (PI. 
  XVI 
  II. 
  figs. 
  1-3.) 
  

  

  Montlivaltia 
  gregaria, 
  M'Coy. 
  Ann. 
  & 
  Mag. 
  N". 
  H. 
  ser. 
  2, 
  vol. 
  ii. 
  

   p. 
  19 
  (1848). 
  

  

  Thecosmilia 
  gregaria, 
  Edw. 
  and 
  Haime, 
  Brit. 
  Foss. 
  Cor. 
  pt. 
  ii. 
  

   p. 
  135, 
  pi. 
  xxviii. 
  

  

  MM. 
  Edwards 
  and 
  Haime, 
  in 
  their 
  great 
  work 
  on 
  the 
  British 
  

   Fossil 
  Corals, 
  after 
  stating 
  that 
  the 
  corresponding 
  calices 
  in 
  Theco- 
  

   smilia 
  annularis 
  are 
  on 
  the 
  same 
  level, 
  observe 
  that 
  that 
  peculiarity 
  

   is, 
  however, 
  only 
  attained 
  with 
  age, 
  and 
  that 
  therefore 
  specimens 
  of 
  

   various 
  ages 
  are 
  necessary 
  for 
  the 
  purpose 
  of 
  investigation*. 
  

  

  Of 
  Thecosmilia 
  trichotoma 
  they 
  say 
  that 
  the 
  corallites 
  " 
  arrange 
  

   themselves 
  so 
  as 
  to 
  constitute 
  a 
  short 
  row, 
  and 
  do 
  not 
  separate 
  

   immediately 
  from 
  each 
  other 
  ; 
  it 
  may 
  even 
  happen 
  that 
  a 
  few 
  of 
  

   these 
  small 
  series 
  of 
  corallites 
  remain 
  in 
  contact 
  laterally, 
  and 
  thus 
  

   assume 
  the 
  form 
  of 
  iSymphyllia. 
  But 
  these 
  variations 
  in 
  the 
  general 
  

   form 
  are 
  only 
  met 
  with 
  in 
  young 
  specimens, 
  and 
  have 
  never 
  been 
  

   met 
  with 
  in 
  the 
  older 
  large 
  corals" 
  f. 
  

  

  The 
  same 
  authorities 
  speak 
  of 
  Thecosmilia 
  gregaria 
  as 
  follows 
  : 
  — 
  

   " 
  T. 
  gregaria 
  differs 
  still 
  more 
  from 
  the 
  preceding 
  species 
  [Thecosmilia 
  

   annularis'] 
  by 
  the 
  corallites 
  remaining 
  in 
  general 
  grouped 
  in 
  fasciculi 
  

   to 
  a 
  considerable 
  distance 
  from 
  the 
  parent 
  calice 
  on 
  which 
  they 
  were 
  

   formed 
  by 
  fissiparous 
  gemmation, 
  a 
  mode 
  of 
  arrangement 
  which 
  we 
  

   have 
  not 
  met 
  with 
  in 
  the 
  other 
  corals 
  of 
  the 
  same 
  genus" 
  %. 
  

  

  From 
  the 
  foregoing 
  passages 
  it 
  is 
  evident 
  that 
  even 
  so 
  long 
  ago 
  as 
  

   1857 
  the 
  present 
  species 
  was 
  not 
  regarded 
  as 
  typical 
  of 
  the 
  genus 
  : 
  and 
  

   Prof. 
  Duncan, 
  in 
  his 
  Supplement 
  to 
  the 
  work 
  of 
  MM. 
  Edwards 
  and 
  

   Haime, 
  appears 
  to 
  have 
  found 
  even 
  greater 
  difficulty 
  in 
  defining 
  the 
  

   species 
  with 
  precision 
  ; 
  for 
  he 
  speaks 
  of 
  as 
  many 
  as 
  five 
  varieties 
  from 
  

   Crickley 
  alone, 
  which, 
  excepting 
  for 
  the 
  examination 
  of 
  a 
  considerable 
  

   series 
  from 
  other 
  scources, 
  might 
  have 
  been 
  supposed 
  to 
  have 
  re- 
  

   lations 
  with 
  Heterogyra, 
  Symphyllia, 
  and 
  Latlmceanclra. 
  Prof. 
  

   Duncan 
  also 
  refers 
  to 
  a 
  series 
  in 
  Dr. 
  Wright's 
  collection 
  which 
  

   appear 
  to 
  graduate 
  into 
  Symj)hyllia§. 
  

  

  In 
  my 
  former 
  paper 
  on 
  Crickley 
  corals 
  I 
  expressed 
  an 
  opinion 
  that, 
  

   with 
  the 
  examination 
  of 
  a 
  greater 
  number 
  of 
  specimens 
  of 
  this 
  species 
  

   and 
  of 
  more 
  varied 
  age, 
  a 
  different 
  and 
  more 
  definite 
  conclusion 
  

   respecting 
  its 
  affinities 
  would 
  be 
  arrived 
  at 
  ; 
  and 
  I 
  held 
  that 
  opinion 
  

   because 
  I 
  had 
  already 
  seen 
  some 
  young 
  individuals 
  which 
  only 
  re- 
  

   quired 
  identification 
  with 
  Thecosmilia 
  gregaria 
  to 
  furnish 
  characters 
  

   which 
  would 
  remove 
  it 
  from 
  the 
  genus 
  Thecosmilia 
  altogether. 
  The 
  

   acquisition 
  of 
  a 
  great 
  many 
  specimens 
  of 
  all 
  ages 
  has 
  supplied 
  the 
  

   intermediate 
  forms 
  ; 
  and 
  these 
  have 
  led 
  to 
  the 
  appearance 
  of 
  this 
  

   well-known 
  species 
  with 
  those 
  with 
  which 
  it 
  is 
  here 
  associated. 
  

  

  In 
  young 
  and 
  typical 
  individuals 
  the 
  appearance 
  is 
  that 
  of 
  a 
  much 
  

  

  * 
  Page 
  84. 
  t 
  Page 
  85. 
  { 
  Page 
  87. 
  

  

  § 
  Supp. 
  Brit. 
  Foss. 
  Corals. 
  

  

  