﻿650 
  ME. 
  J. 
  W. 
  GEEGOEr 
  ON" 
  CTSTECHINUS 
  CEASSTTS. 
  

  

  has, 
  however, 
  shown 
  * 
  that 
  the 
  abyssal 
  genera 
  of 
  the 
  present 
  day, 
  

   such 
  as 
  Argopatagus, 
  Palceotropus, 
  Urediinus, 
  CystecJiinus, 
  and 
  

   Calymne, 
  are 
  apetalous, 
  while 
  the 
  littoral 
  genera 
  of 
  the 
  Clypeastro- 
  

   idea 
  and 
  Petalosticha 
  usually 
  have 
  petaloid 
  ambulacra, 
  and 
  that, 
  

   moreover, 
  the 
  same 
  peculiarity 
  may 
  be 
  noticed 
  within 
  the 
  limits 
  of 
  a 
  

   single 
  genus 
  ; 
  thus 
  in 
  Scliizaster 
  the 
  deep-sea 
  species 
  are 
  less 
  petaloid 
  

   than 
  the 
  littoral. 
  This 
  feature 
  Loven 
  attributes 
  to 
  the 
  nature 
  of 
  

   the 
  gases 
  of 
  the 
  abyssal 
  waters. 
  CystecJiinus 
  crassus 
  is 
  apetalous, 
  

   and 
  as 
  we 
  might 
  have 
  expected 
  some 
  variation 
  in 
  this 
  point 
  in 
  the 
  

   ambulacra 
  had 
  the 
  species 
  been 
  a 
  shallow-water 
  form, 
  we 
  may 
  

   fairly 
  conclude 
  that 
  it 
  was 
  a 
  dweller 
  in 
  the 
  deep 
  seas. 
  

  

  The 
  imperfect 
  preservation 
  of 
  this, 
  the 
  only 
  fossil 
  specimen 
  of 
  its 
  

   family, 
  is 
  to 
  be 
  deplored, 
  the 
  more 
  so 
  since 
  their 
  abyssal 
  habitat 
  is 
  

   as 
  unfavourable 
  to 
  their 
  being 
  found 
  by 
  the 
  palaeontologist 
  as 
  the 
  

   fragility 
  of 
  the 
  test 
  in 
  recent 
  species 
  is 
  to 
  their 
  preservation 
  by 
  the 
  

   zoologist. 
  A 
  more 
  thorough 
  search 
  in 
  the 
  Eadiolarian 
  deposits 
  of 
  

   Barbados 
  may, 
  however, 
  bring 
  to 
  light 
  further 
  material. 
  Never- 
  

   theless 
  the 
  foregoing 
  description, 
  despite 
  its 
  inevitable 
  imperfection, 
  

   appears 
  justified 
  not 
  only 
  by 
  the 
  intrinsic 
  interest 
  of 
  the 
  genus, 
  nor 
  

   merely 
  by 
  the 
  unique 
  position 
  of 
  the 
  specimen 
  as 
  the 
  sole 
  extinct 
  

   representative 
  of 
  its 
  group, 
  but 
  by 
  the 
  evidence 
  of 
  this 
  fossil 
  as 
  to 
  the 
  

   age 
  and 
  origin 
  of 
  the 
  Barbadian 
  deposits 
  — 
  an 
  evidence 
  which, 
  as 
  

   herein 
  suggested, 
  is 
  not 
  without 
  its 
  bearing 
  on 
  some 
  broader 
  ques- 
  

   tions 
  of 
  geological 
  speculation. 
  

  

  Discussion. 
  

  

  The 
  Chaieman 
  (Prof. 
  J. 
  W. 
  Jucld) 
  congratulated 
  the 
  Author 
  on 
  

   the 
  very 
  clear 
  way 
  in 
  which 
  he 
  had 
  laid 
  his 
  facts 
  and 
  inferences 
  

   before 
  the 
  Society. 
  

  

  He 
  considered 
  that 
  if 
  it 
  could 
  be 
  demonstrated 
  that 
  these 
  deposits 
  

   were 
  so 
  late 
  as 
  the 
  Author 
  supposed, 
  and 
  that 
  the 
  material 
  was 
  

   actually 
  laid 
  down 
  in 
  such 
  deep 
  seas, 
  it 
  afforded 
  strong 
  proofs 
  of 
  

   striking 
  movements 
  in 
  comparatively 
  recent 
  times. 
  

  

  The 
  Atjthoe 
  stated 
  that 
  these 
  Barbados 
  rocks 
  were 
  much 
  con- 
  

   torted, 
  showing 
  that 
  differential 
  movements 
  had 
  taken 
  place 
  in 
  

   comparatively 
  modern 
  times. 
  

  

  * 
  S. 
  Loven, 
  " 
  On 
  Pourtalesia, 
  a 
  Genus 
  of 
  Echinoidea," 
  Kongl. 
  Svenska 
  Vetensk, 
  

   Akad. 
  Hancll. 
  new 
  ser. 
  xix. 
  'No. 
  7, 
  1883, 
  p. 
  95. 
  

  

  