﻿art 
  9 
  UNUSUAL 
  FORMS 
  OF 
  FOSSIL 
  CRINOIDS 
  SPRINGER 
  7 
  

  

  and 
  distal 
  regions 
  involute, 
  enlarging, 
  sometimes 
  diminishing 
  

   again, 
  bilaterally 
  symmetric, 
  elliptic 
  or 
  subcrescentric 
  in 
  section; 
  

   with 
  two 
  rows 
  of 
  jointed 
  cirri 
  along 
  the 
  margins 
  or 
  the 
  back 
  of 
  the 
  

   bilateral 
  part 
  varying 
  in 
  arrangement, 
  which 
  may 
  converge 
  over 
  

   the 
  closely 
  coiled 
  noncirriferous 
  proximal 
  portion 
  like 
  spokes 
  of 
  a 
  

   wheel. 
  Crown 
  of 
  the 
  type 
  of 
  the 
  Heterocrinidae 
  ; 
  without 
  compound 
  

   radials, 
  and 
  rather 
  resembling 
  locrinus 
  than 
  Heterocrinus; 
  rays 
  ir- 
  

   regular, 
  more 
  or 
  less 
  unequal 
  in 
  size, 
  four 
  or 
  five 
  in 
  number; 
  arms 
  

   dichotomous 
  or 
  slightly 
  heterotomous. 
  (Partly 
  adapted 
  from 
  Bather 
  

   under 
  Hevpetocrinus. 
  ) 
  

  

  As 
  observed 
  by 
  Bather, 
  5 
  the 
  chief 
  diagnostic 
  characters 
  within 
  

   the 
  genus 
  are 
  furnished 
  by 
  the 
  stem 
  and 
  its 
  appendages. 
  The 
  

   crown 
  is 
  rarely 
  seen, 
  and 
  owing 
  to 
  pressure 
  resulting 
  from 
  its 
  in- 
  

   rolled 
  habitus 
  the 
  calyx 
  did 
  not 
  have 
  the 
  freedom 
  to 
  develop 
  in 
  the 
  

   usual 
  way, 
  and 
  is 
  therefore 
  more 
  or 
  less 
  deformed. 
  

  

  Except 
  in 
  the 
  Devonian 
  species, 
  the 
  crown 
  is 
  usually 
  very 
  slender 
  

   and 
  elongate, 
  so 
  that 
  it 
  can 
  lie 
  along 
  the 
  grooved 
  side 
  of 
  the 
  stem, 
  

   between 
  the 
  two 
  rows 
  of 
  cirri, 
  without 
  producing 
  any 
  swelling 
  or 
  

   bulging 
  to 
  indicate 
  its 
  presence. 
  In 
  that 
  condition 
  it 
  is 
  impossible 
  

   to 
  see 
  anything 
  beyond 
  the 
  general 
  outline 
  of 
  the 
  crown, 
  and 
  we 
  are 
  

   therefore 
  unable 
  to 
  analyze 
  its 
  composition. 
  In 
  the 
  two 
  cases 
  in 
  

   which 
  the 
  full 
  contour 
  of 
  the 
  calyx 
  has 
  been 
  seen, 
  one 
  a 
  Silurian 
  and 
  

   the 
  other 
  a 
  Devonian 
  species, 
  the 
  former 
  has 
  four 
  rays 
  and 
  the 
  latter 
  

   five. 
  If 
  this 
  difference 
  were 
  known 
  to 
  be 
  constant, 
  it 
  might 
  furnish 
  

   ground 
  for 
  a 
  subdivision 
  of 
  the 
  genus. 
  But 
  in 
  the 
  presence 
  of 
  so 
  

   remarkable 
  a 
  specialization 
  the 
  crown 
  was 
  doubtless 
  in 
  a 
  plastic 
  con- 
  

   dition, 
  and 
  with 
  the 
  evidence 
  we 
  have, 
  or 
  are 
  likely 
  to 
  obtain, 
  there 
  

   seems 
  to 
  be 
  no 
  other 
  course 
  than 
  to 
  treat 
  these 
  variations 
  as 
  secondary 
  

   occurrences, 
  incident 
  to 
  the 
  cramped 
  condition 
  in 
  which 
  the 
  crown 
  

   habitually 
  grew, 
  which 
  necessarily 
  produced 
  more 
  or 
  less 
  suppres- 
  

   sion 
  or 
  deformation 
  of 
  the 
  parts 
  subject 
  to 
  pressure. 
  

  

  On 
  the 
  other 
  hand, 
  the 
  stem 
  was 
  a 
  seat 
  of 
  activity 
  unusual 
  in 
  the 
  

   stalked 
  crinoids, 
  and 
  the 
  cirri 
  took 
  on 
  special 
  functions 
  analogous 
  

   to 
  those 
  of 
  the 
  comatulids 
  — 
  that 
  is 
  to 
  say, 
  they 
  became 
  active, 
  per- 
  

   haps 
  prehensile, 
  organs, 
  free 
  to 
  develop 
  according 
  to 
  their 
  condi- 
  

   tions; 
  and 
  their 
  modifications, 
  as 
  in 
  the 
  comatulids, 
  furnish 
  impor- 
  

   tant 
  characters 
  for 
  the 
  discrimination 
  of 
  species. 
  Bather 
  suggests 
  5 
  

   (p. 
  46) 
  that 
  these 
  probably 
  broke 
  off 
  any 
  rooted 
  attachment 
  they 
  

   may 
  have 
  formed, 
  and 
  that 
  they 
  clung 
  to 
  corals 
  or 
  other 
  objects 
  by 
  

   their 
  cirri 
  — 
  a 
  mode 
  of 
  life 
  that 
  would 
  furnish 
  the 
  stimulus 
  for 
  nu- 
  

   merous 
  variations. 
  This 
  suggestion 
  is 
  reinforced 
  by 
  my 
  observa- 
  

   tions, 
  showing 
  positively 
  that 
  in 
  some 
  species 
  the 
  stem 
  was 
  free 
  

   from 
  any 
  attachment 
  whatever. 
  

  

  6 
  Crinoidea 
  of 
  Gotland, 
  p. 
  45. 
  

  

  