﻿aht. 
  18 
  THE 
  CRIXOIJ) 
  GENUS 
  A.PIOCRINUS 
  SPRINGEK 
  & 
  

  

  running 
  inward 
  from 
  the 
  periphery 
  to 
  a 
  smooth 
  ring 
  surrounding 
  

   the 
  lumen, 
  about 
  one-third 
  the 
  diameter 
  of 
  the 
  columnal 
  and 
  flush 
  

   with 
  ..the 
  adjacent 
  surface; 
  this 
  is 
  seen 
  in 
  several 
  specimens, 
  and 
  is 
  

   evidently 
  a 
  constant 
  character, 
  with 
  perhaps 
  some 
  variation 
  in 
  rela- 
  

   tive 
  diameter. 
  

  

  In 
  the 
  structure 
  of 
  the 
  joint-face 
  may 
  be 
  seen 
  the 
  decisive 
  differ- 
  

   ence 
  between 
  this 
  genus 
  and 
  Pentacrinus, 
  Isocrinus, 
  or 
  Balanocrinus, 
  

   the 
  other 
  forms 
  which 
  might 
  be 
  encountered 
  in 
  rocks 
  of 
  the 
  same 
  age. 
  

   In 
  these 
  the 
  joint-face 
  is 
  divided 
  into 
  five 
  petaloid 
  sectors 
  differing 
  

   among 
  the 
  genera, 
  the 
  first 
  two 
  having 
  short 
  crenelations 
  at 
  the 
  mar- 
  

   gin 
  of 
  the 
  sectors, 
  and 
  the 
  last 
  having 
  them 
  only 
  at 
  the 
  periphery 
  of 
  

   the 
  stem. 
  In 
  Apiocrinus 
  there 
  are 
  no 
  sectors, 
  and 
  the 
  striae 
  extend 
  

   directly 
  inward 
  for 
  about 
  one-third 
  to 
  two-fifths 
  the 
  diameter 
  of 
  

   the 
  joint, 
  or 
  perhaps 
  sometimes 
  all 
  the 
  way 
  to 
  the 
  lumen. 
  For 
  con- 
  

   venience 
  of 
  comparison 
  with 
  the 
  Apiocrinus 
  joint-face, 
  and 
  also 
  to 
  

   facilitate 
  identification 
  of 
  fragments 
  that 
  are 
  likely 
  to 
  be 
  found, 
  I 
  

   am 
  giving 
  characteristic 
  figures 
  of 
  the 
  other 
  two 
  types 
  (pi. 
  1, 
  figs. 
  

   8, 
  9, 
  10, 
  11). 
  The 
  smooth 
  ring 
  surrounding 
  the 
  lumen 
  is 
  a 
  marked 
  

   character 
  in 
  our 
  species, 
  occupying 
  about 
  one-third 
  the 
  diameter 
  of 
  

   the 
  joint, 
  probably 
  varying 
  in 
  different 
  parts 
  of 
  the 
  stem; 
  it 
  is 
  but 
  

   little, 
  if 
  any, 
  sunken 
  below 
  the 
  general 
  surface 
  of 
  the 
  joint, 
  and 
  the 
  

   striae 
  in 
  some 
  cases 
  pass 
  over 
  it. 
  

  

  Among 
  European 
  species 
  comparison 
  may 
  be 
  made 
  with 
  Apio- 
  

   crinus 
  elegans 
  (Defrance), 
  which 
  is 
  of 
  a 
  very 
  similar 
  type 
  to 
  our 
  

   species, 
  having 
  usually 
  less 
  curvature 
  to 
  the 
  sides 
  of 
  the 
  expanded 
  

   stem 
  than 
  in 
  such 
  characteristic 
  species 
  as 
  A. 
  parhinsoni 
  and 
  A. 
  

   roissyanus. 
  Apiocrinus 
  elegans 
  was 
  described 
  by 
  Defrance 
  in 
  

   1819 
  4 
  as 
  Astropoda, 
  and 
  in 
  1839 
  was 
  referred 
  by 
  D'Orbigny 
  to 
  

   Apiocrinus:' 
  The 
  species 
  is 
  widely 
  distributed, 
  and 
  occurs 
  at 
  many 
  

   localities 
  in 
  France, 
  especially 
  in 
  the 
  districts 
  of 
  Calvados, 
  Cote 
  

   d'Or, 
  Nievre, 
  etc. 
  It 
  has 
  been 
  thoroughly 
  described 
  and 
  figured 
  by 
  

   De 
  Loriol, 
  6 
  from 
  whom 
  I 
  am 
  giving 
  copies 
  of 
  his 
  figures 
  1, 
  4, 
  and 
  6 
  

   of 
  plate 
  34, 
  showing 
  the 
  contour 
  of 
  stem 
  and 
  calyx, 
  and 
  figures 
  4, 
  

   46, 
  4<? 
  of 
  plate 
  35, 
  giving 
  details 
  of 
  the 
  joint-face. 
  

  

  In 
  relative 
  proportions 
  of 
  the 
  corresponding 
  parts 
  there 
  is 
  little 
  

   difference 
  between 
  our 
  species 
  and 
  this. 
  In 
  the 
  5 
  columnals 
  of 
  ours 
  

   the 
  spread 
  in 
  diameter 
  is 
  as 
  1 
  to 
  1.4; 
  in 
  De 
  Loriol's 
  figures 
  of 
  A. 
  

   elegans 
  on 
  plate 
  34 
  for 
  the 
  same 
  number 
  of 
  columnals 
  the 
  spread 
  in 
  

   figure 
  4 
  is 
  as 
  1 
  to 
  1.5, 
  and 
  in 
  figure 
  6 
  as 
  1 
  to 
  1.6. 
  The 
  joint-face 
  as 
  

   shown 
  by 
  figures 
  4, 
  4c 
  of 
  plate 
  35, 
  has 
  a 
  somewhat 
  less 
  number 
  of 
  

   striae, 
  about 
  48, 
  and 
  a 
  similar 
  smooth 
  median 
  ring, 
  which 
  is 
  rela- 
  

   tively 
  larger 
  and 
  distinctly 
  sunken. 
  This 
  smooth 
  inner 
  ring 
  sur- 
  

  

  «Dict. 
  des 
  Sci. 
  Nat., 
  vol. 
  14, 
  p. 
  468. 
  

  

  6 
  Hist. 
  Nat. 
  des 
  Crinoides, 
  p. 
  29, 
  pi. 
  5, 
  figs. 
  9-15. 
  

  

  • 
  Crinoides 
  de 
  la 
  France, 
  vol. 
  2. 
  pt. 
  1, 
  1888, 
  p. 
  240, 
  pis. 
  34, 
  35. 
  

  

  