﻿art 
  9 
  UNUSUAL 
  FORMS 
  OF 
  FOSSIL 
  CRINOIDS 
  SPRINGER 
  3 
  

  

  know 
  it 
  occurred, 
  the 
  causes 
  of 
  which 
  are 
  unknown, 
  but 
  which 
  serve 
  

   as 
  examples 
  of 
  the 
  infinite 
  variety 
  with 
  which 
  the 
  processes 
  of 
  nature 
  

   go 
  on. 
  Many 
  of 
  these 
  are 
  already 
  well 
  known, 
  and 
  some 
  others 
  it 
  is 
  

   the 
  purpose 
  of 
  this 
  paper 
  to 
  illustrate. 
  No 
  general 
  discussion 
  of 
  

   crinoid 
  morphology 
  is 
  here 
  attempted. 
  For 
  that 
  reference 
  should 
  

   be 
  had 
  to 
  the 
  works 
  of 
  Bather 
  in 
  part 
  3 
  of 
  the 
  Lankester 
  Zoology; 
  

   of 
  Austin 
  H. 
  Clark 
  on 
  the 
  Existing 
  Crinoids; 
  of 
  Wachsmuth 
  and 
  

   Springer 
  on 
  the 
  Crinoidea 
  Camerata; 
  of 
  myself 
  on 
  the 
  Crinoidea 
  

   Flexibilia; 
  and 
  to 
  various 
  papers 
  by 
  Jaekel. 
  

  

  I 
  am 
  simply 
  presenting 
  a 
  number 
  of 
  facts, 
  more 
  or 
  less 
  unrelated, 
  

   bearing 
  upon 
  some 
  of 
  the 
  unusual 
  features 
  and 
  changes 
  above 
  

   alluded 
  to, 
  by 
  which 
  the 
  general 
  progress 
  of 
  the 
  crinoids 
  in 
  geo- 
  

   logical 
  time 
  was 
  characterized; 
  together 
  with 
  discussion 
  of 
  some 
  

   remarkable 
  parallel 
  modifications 
  which 
  I 
  am 
  now 
  able 
  to 
  illustrate 
  

   more 
  completely 
  than 
  was 
  possible 
  heretofore. 
  

  

  THE 
  COILED 
  BILATERAL 
  STEM 
  

  

  While 
  the 
  possession 
  of 
  a 
  stem 
  is 
  one 
  of 
  the 
  characters 
  by 
  which 
  

   the 
  crinoids 
  as 
  a 
  class 
  are 
  best 
  known 
  — 
  so 
  much 
  so 
  that 
  a 
  large 
  part 
  

   of 
  the 
  early 
  literature 
  treating 
  of 
  them 
  was 
  devoted 
  mainly 
  to 
  discus- 
  

   sion 
  of 
  the 
  isolated 
  segments 
  of 
  which 
  it 
  is 
  composed 
  — 
  there 
  was 
  in 
  

   some 
  instances 
  a 
  remarkable 
  tendency 
  to 
  get 
  rid 
  of 
  it. 
  This 
  append- 
  

   age 
  probably 
  existed 
  in 
  the 
  larval 
  stage 
  of 
  all 
  crinoids, 
  but 
  in 
  by 
  far 
  

   the 
  greater 
  part 
  of 
  the 
  existing 
  forms, 
  the 
  comatulids, 
  it 
  is 
  cast 
  off 
  at 
  

   approaching 
  maturity, 
  and 
  the 
  adult 
  crinoid 
  becomes 
  a 
  free 
  floater. 
  

   In 
  some, 
  the 
  pentacrinites, 
  it 
  attained 
  a 
  great 
  length; 
  and 
  in 
  some 
  

   (thought 
  to 
  be 
  due 
  to 
  living 
  on 
  reefs 
  in 
  shallow 
  water) 
  the 
  stem 
  is 
  

   very 
  short, 
  or 
  even 
  disappears, 
  fixation 
  being 
  accomplished 
  through 
  

   direct 
  attachment 
  by 
  the 
  fused 
  base. 
  

  

  In 
  most 
  of 
  the 
  Paleozoic 
  genera 
  the 
  stem 
  was 
  present, 
  sometimes 
  

   attached 
  or 
  anchored 
  by 
  remarkable 
  specialized 
  structures 
  (Scypho- 
  

   crlnus, 
  Ancyrocrinus, 
  etc.) 
  1 
  ; 
  in 
  many 
  cases 
  only 
  resting 
  in 
  the 
  soft 
  

   coze 
  of 
  the 
  sea 
  bottom 
  by 
  finely 
  pointed 
  terminals, 
  and 
  often 
  not 
  

   permanently 
  fixed. 
  2 
  

  

  The 
  great 
  Paleozoic 
  divisions, 
  Camerata 
  and 
  Flexibilia, 
  and 
  the 
  

   chiefly 
  Paleozoic 
  Inadunata, 
  had 
  stems 
  with 
  but 
  few 
  exceptions, 
  

   such 
  as 
  Edriocrinus 
  in 
  which 
  the 
  base 
  was 
  fused 
  and 
  attached 
  

   directly 
  to 
  other 
  objects 
  or 
  became 
  rounded 
  and 
  free 
  from 
  attach- 
  

   ment, 
  and 
  Agassizocrinus 
  in 
  which 
  a 
  free 
  floating 
  stage 
  in 
  some 
  of 
  

   its 
  species 
  was 
  also 
  attained. 
  The 
  same 
  thing 
  is 
  true 
  of 
  the 
  Mesozoic 
  

   crinoids. 
  

  

  1 
  Springer, 
  On 
  the 
  crinoid 
  genus 
  Scyphocrinus, 
  Smiths. 
  Misc. 
  Coll. 
  Publication 
  2440, 
  

   1917, 
  pp. 
  9-12. 
  

  

  2 
  Dr. 
  Edwin 
  Kirk's 
  instructive 
  paper 
  on 
  Eleutherozoic 
  relmatozoa, 
  Proc. 
  U. 
  S. 
  Nat. 
  

   Mus., 
  vol. 
  41, 
  1911, 
  pp. 
  1-137. 
  

  

  