﻿autO 
  UNUSUAL 
  FORMS 
  OF 
  FOSSIL 
  CRINOIDS 
  SPRINGER 
  39 
  

  

  there 
  were 
  none 
  which 
  showed 
  any 
  indication 
  of 
  recumbent 
  arms. 
  In 
  

   the 
  closely 
  related 
  Eucladocrinus 
  the 
  long 
  radial 
  extensions, 
  or 
  tubu- 
  

   lar 
  appendages, 
  frequently 
  show 
  a 
  tendency 
  to 
  bend 
  backward 
  over 
  

   the 
  calyx, 
  but 
  always 
  the 
  true 
  arms 
  are 
  folded 
  over 
  the 
  ventral 
  side 
  ; 
  

   even 
  in 
  cases 
  like 
  that 
  of 
  E. 
  tuberosus 
  18 
  , 
  where 
  the 
  tegmen 
  is 
  strongly 
  

   hemispherical, 
  and 
  the 
  arm 
  bases 
  are 
  directed 
  far 
  below 
  the 
  hori- 
  

   zontal, 
  the 
  arms 
  fold 
  in 
  the 
  normal 
  way. 
  The 
  same 
  thing 
  may 
  be 
  

   said 
  of 
  other 
  genera 
  with 
  hemispheric 
  calyx, 
  like 
  Megistocrinus, 
  

   Agaricocrinus, 
  etc. 
  

  

  In 
  recent 
  years, 
  however, 
  I 
  have 
  obtained 
  two 
  specimens 
  of 
  Platy- 
  

   crinus 
  from 
  the 
  well 
  known 
  locality 
  of 
  Le 
  Grand, 
  Iowa, 
  but 
  at 
  a 
  

   different 
  horizon 
  from 
  that 
  of 
  the 
  numerous 
  species 
  heretofore 
  de- 
  

   scribed, 
  in 
  which 
  the 
  arms 
  are 
  compactly 
  folded 
  backward 
  upon 
  the 
  

   calyx 
  and 
  stem, 
  and 
  apparently 
  fixed 
  in 
  that 
  position, 
  after 
  the 
  man- 
  

   ner 
  of 
  Barrandeocrinus 
  and 
  Acrocrinus. 
  The 
  calyx 
  in 
  both 
  is 
  com- 
  

   pletely 
  enveloped, 
  and 
  can 
  only 
  be 
  partially 
  exposed, 
  considerably 
  

   distorted, 
  in 
  one 
  of 
  them. 
  We 
  know 
  that 
  the 
  species 
  belongs 
  to 
  

   Platycrinus, 
  because 
  both 
  specimens 
  have 
  the 
  twisted, 
  elliptic 
  stem. 
  

   Of 
  other 
  characters 
  little 
  can 
  be 
  said, 
  and 
  the 
  position 
  of 
  the 
  arms 
  

   must 
  distinguish 
  the 
  species. 
  I 
  am 
  giving 
  two 
  views 
  of 
  one 
  speci- 
  

   men 
  ; 
  the 
  other 
  is 
  slightly 
  larger, 
  and 
  equally 
  characteristic 
  as 
  to 
  the 
  

   arms. 
  

  

  Horizon 
  and 
  locality. 
  — 
  Mississippian, 
  Kinderhook 
  group, 
  lower 
  

   horizon; 
  Le 
  Grand, 
  Iowa. 
  

  

  Genus 
  DICHOCRINUS 
  Miinster 
  

   Plate 
  11 
  

  

  Dichocrinus 
  Wachsmuth 
  and 
  Springer, 
  North 
  Amer. 
  Crin. 
  Cam., 
  1897, 
  

  

  p. 
  753. 
  

   Lower 
  Carboniferous, 
  Kinderhook 
  to 
  Chester. 
  

  

  Among 
  the 
  changes 
  to 
  which 
  this 
  highly 
  variable 
  genus 
  and 
  its 
  

   allies 
  were 
  subject, 
  the 
  recumbent 
  arm 
  took 
  a 
  strong 
  hold. 
  This 
  was 
  

   illustrated 
  by 
  Wachsmuth 
  and 
  Springer 
  under 
  their 
  species 
  Dicho- 
  

   crinus 
  pendens 
  from 
  the 
  Burlington 
  limestone 
  19 
  , 
  and 
  I 
  am 
  now 
  giv- 
  

   ing 
  some 
  additional 
  figures 
  of 
  it, 
  including 
  one 
  of 
  a 
  specimen 
  with 
  

   the 
  complete 
  stem 
  and 
  crown, 
  partly 
  to 
  show 
  the 
  persistence 
  of 
  this 
  

   character, 
  several 
  specimens 
  having 
  now 
  been 
  found, 
  and 
  partly 
  to 
  

   exhibit 
  the 
  Dichocrinus 
  stem 
  as 
  usually 
  seen, 
  in 
  comparison 
  with 
  one 
  

   of 
  its 
  remarkable 
  variations 
  (pi. 
  11, 
  figs. 
  4, 
  7). 
  The 
  first 
  is 
  without 
  

   cirri, 
  except 
  in 
  the 
  form 
  of 
  distal 
  root 
  branches, 
  while 
  the 
  latter 
  has 
  

   cirri 
  in 
  regular 
  whorls, 
  beginning 
  in 
  the 
  upper 
  region 
  of 
  the 
  stem, 
  

   of 
  such 
  an 
  extraordinary 
  length 
  that 
  they 
  completely 
  envelop 
  the 
  

  

  18 
  North 
  Amer. 
  Crin. 
  Cam., 
  pi. 
  72, 
  figs. 
  4a, 
  6c. 
  

  

  19 
  Idem, 
  p. 
  774, 
  pi. 
  78, 
  fig. 
  15. 
  

  

  