﻿FROM 
  THE 
  RADIOLARIAN 
  MARLS 
  OF 
  BARBADOS. 
  641 
  

  

  Apical 
  system 
  subcentral, 
  slightly 
  excentric 
  posteriorly. 
  Slightly 
  

   produced 
  and 
  disjoint. 
  Three 
  or 
  four 
  genital 
  pores. 
  The 
  position 
  

   of 
  the 
  madreporite 
  is 
  variable 
  ; 
  it 
  is 
  usually 
  on 
  the 
  right 
  antero- 
  

   lateral 
  basal, 
  but 
  it 
  may 
  have 
  receded 
  on 
  to 
  one 
  of 
  the 
  adjoining 
  

   intercalated 
  perisomatic 
  plates. 
  These 
  plates 
  are 
  two 
  or 
  more 
  in 
  

   number. 
  

  

  Ambulacra 
  apetaloid. 
  Ambulacral 
  plates 
  large 
  and 
  usually 
  hex- 
  

   agonal, 
  each 
  perforated 
  by 
  a 
  single 
  pore, 
  and 
  either 
  of 
  the 
  same 
  

   number 
  as 
  the 
  interambulacral 
  plates 
  or 
  but 
  slightly 
  in 
  excess. 
  

  

  Inter 
  ambulacral 
  plates 
  normally 
  hexagonal, 
  broader 
  than 
  deep 
  ; 
  

   horizontal 
  sutures 
  more 
  or 
  less 
  curved. 
  The 
  plates 
  of 
  the 
  postero- 
  

   lateral 
  interambulacra 
  are 
  the 
  smallest. 
  Caudal 
  beak 
  rudimentary 
  

   or 
  absent. 
  

  

  Epistroma. 
  The 
  whole 
  test 
  is 
  ornamented 
  with 
  a 
  fine 
  granulation 
  

   and 
  scattered 
  tubercles. 
  

  

  Actinostome 
  central 
  or 
  subcentral 
  ; 
  depressed, 
  the 
  edges 
  raised 
  

   into 
  a 
  rudimentary 
  perignathic 
  girdle. 
  Actinal 
  plates 
  simple. 
  

  

  Periproct 
  inframarginal, 
  just 
  below 
  the 
  ambitus. 
  

  

  No 
  fascioles. 
  

  

  Three 
  species 
  of 
  Cystechimis 
  were 
  found 
  by 
  the 
  ' 
  Challenger 
  ' 
  

   Expedition, 
  all 
  of 
  which 
  came 
  from 
  very 
  deep 
  seas. 
  C. 
  Wyvillii, 
  

   the 
  type 
  species, 
  was 
  dredged 
  at 
  depths 
  varying 
  from 
  1375 
  fathoms, 
  

   off 
  the 
  Crozet 
  Isles 
  in 
  the 
  Antarctic 
  Ocean 
  (Stat. 
  146), 
  down 
  to 
  2160 
  

   fathoms 
  off 
  Juan 
  Fernandez 
  (Stat. 
  299), 
  while 
  it 
  was 
  met 
  at 
  inter- 
  

   mediate 
  depths 
  at 
  Stations 
  147 
  and 
  158 
  in 
  the 
  Antarctic 
  Ocean, 
  and 
  

   at 
  Stations 
  296 
  and 
  299 
  off 
  the 
  coast 
  of 
  Chile. 
  C. 
  vesica 
  has 
  been 
  

   found 
  to 
  range 
  from 
  1675 
  fathoms 
  in 
  the 
  Antarctic 
  Ocean 
  at 
  Station 
  

   153, 
  to 
  2160 
  and 
  2225 
  fathoms 
  at 
  Stations 
  299 
  and 
  298, 
  between 
  

   Juan 
  Fernandez 
  and 
  Valparaiso. 
  C. 
  clypeatus, 
  the 
  species 
  which 
  

   is 
  probably 
  the 
  nearest 
  ally 
  of 
  O. 
  crassus, 
  was 
  found 
  off 
  Tristan 
  

   da 
  Cunha 
  at 
  Stations 
  133 
  and 
  334 
  and 
  in 
  the 
  China 
  Sea 
  at 
  Station 
  

   205, 
  at 
  depths 
  of 
  1900, 
  1915, 
  and 
  1050 
  fathoms 
  respectively. 
  

  

  The 
  bathymetrical 
  range 
  of 
  the 
  genus 
  is 
  therefore 
  from 
  1050 
  to 
  

   2225 
  fathoms. 
  Its 
  geographical 
  distribution 
  is 
  in 
  the 
  China 
  Sea, 
  in 
  

   the 
  Pacific 
  off 
  the 
  S.W. 
  coast 
  of 
  S. 
  America, 
  in 
  the 
  Atlantic 
  near 
  

   Tristan 
  da 
  Cunha, 
  and 
  in 
  the 
  Antarctic 
  between 
  the 
  Cape 
  and 
  Aus- 
  

   tralia. 
  Its 
  geological 
  distribution 
  is, 
  with 
  the 
  exception 
  of 
  the 
  

   species 
  here 
  described, 
  limited 
  to 
  the 
  present 
  time. 
  

  

  Cystechintjs 
  crassus, 
  n. 
  sp. 
  (Figs. 
  1-3, 
  p. 
  643.) 
  

  

  Shape 
  oval, 
  depressed 
  ; 
  posterior 
  interradius 
  flat. 
  The 
  flexibility 
  

   of 
  the 
  test 
  is 
  slight, 
  the 
  plates 
  are 
  1*5 
  mm. 
  in 
  thickness. 
  

  

  Ambulacra 
  apetaloid. 
  The 
  plates 
  are 
  large 
  and 
  fairly 
  uniform 
  in 
  

   size. 
  In 
  shape 
  they 
  are 
  hexagons, 
  which 
  are 
  usually 
  nearly 
  regular. 
  

   They 
  are 
  of 
  the 
  same 
  number 
  as 
  in 
  the 
  interradii, 
  viz. 
  7 
  or 
  8 
  be- 
  

   tween 
  apical 
  disc 
  and 
  ambitus. 
  The 
  pore 
  in 
  each 
  plate 
  is 
  central 
  

   or 
  subcentral, 
  the 
  excentricity 
  being 
  towards 
  the 
  abactinal 
  side 
  

   of 
  each 
  plate. 
  

  

  The 
  plates 
  are 
  flat, 
  without 
  ridges, 
  and 
  covered 
  by 
  a 
  minute 
  gran- 
  

   ulation 
  with 
  a 
  few 
  irregularly 
  scattered 
  small 
  tubercles. 
  

  

  3a2 
  

  

  