﻿akt!) 
  UNUSUAL 
  FORMS 
  OF 
  FOSSIL 
  CRINOIDS 
  SPRINGER 
  29 
  

  

  The 
  exact 
  mode 
  of 
  succession 
  of 
  these 
  diminishing 
  cirri 
  is 
  rather 
  

   difficult 
  to 
  ascertain; 
  the 
  outer 
  one 
  rests 
  in 
  a 
  good 
  sized 
  facet 
  upon 
  

   the 
  suture 
  between 
  the 
  two 
  short 
  nodals, 
  and 
  each 
  succeeding 
  one 
  

   seems 
  to 
  be 
  articulated 
  upon 
  the 
  first 
  cirral 
  of 
  its 
  predecessor, 
  some- 
  

   what 
  as 
  shown 
  by 
  the 
  sketches 
  on 
  plate 
  7. 
  

  

  The 
  occurrence 
  of 
  the 
  cirri 
  in 
  diminishing 
  clusters 
  recalls 
  the 
  

   more 
  elaborate 
  arrangement 
  seen 
  in 
  Bather's 
  Hevpetocrinus 
  flabel- 
  

   licirrus. 
  There 
  is 
  no 
  sign 
  of 
  rudimentary 
  cirri, 
  outside 
  of 
  the 
  

   marginal 
  rows, 
  in 
  ?my 
  of 
  the 
  specimens 
  of 
  this 
  species. 
  The 
  crown 
  

   is 
  imperfectly 
  known, 
  being 
  usually 
  closely 
  enveloped 
  by 
  the 
  cirri, 
  

   as 
  is 
  most 
  of 
  the 
  species 
  of 
  Myelodactylus, 
  but 
  enough 
  is 
  exposed 
  

   in 
  one 
  specimen 
  to 
  show 
  that 
  it 
  belongs 
  to 
  the 
  usual 
  Dichocrinus 
  

   type: 
  it 
  was 
  evidently 
  smaller 
  than 
  in 
  the 
  other 
  Keokuk 
  species. 
  

   Total 
  length 
  of 
  stem 
  in 
  maximum 
  specimen 
  10.5 
  cm. 
  with 
  probably 
  

   1.5 
  cm. 
  missing 
  at 
  the 
  distal 
  end; 
  length 
  of 
  circular 
  neck 
  about 
  1 
  cm. 
  ; 
  

   diameter 
  of 
  proximal 
  coil 
  in 
  two 
  specimens 
  having 
  the 
  most 
  com- 
  

   plete 
  stem 
  about 
  one-fourth 
  the 
  total 
  length 
  of 
  stem. 
  

  

  In 
  connection 
  with 
  the 
  original 
  description 
  three 
  specimens 
  were 
  

   figured, 
  two 
  of 
  which 
  are 
  of 
  the 
  type 
  above 
  described; 
  and 
  it 
  was 
  

   from 
  these 
  two 
  that 
  the 
  description 
  relative 
  to 
  the 
  details 
  of 
  stem 
  and 
  

   cirri 
  was 
  made, 
  it 
  being 
  stated 
  that 
  the 
  cirri 
  were 
  slender, 
  composed 
  

   of 
  about 
  sixteen 
  to 
  eighteen 
  joints 
  ending 
  in 
  a 
  sharp 
  point, 
  and 
  that 
  

   they 
  arose 
  from 
  alternate 
  columnals 
  — 
  overlooking 
  the 
  fact 
  that 
  in 
  

   the 
  two 
  specimens 
  above 
  mentioned 
  the 
  " 
  alternate 
  joint 
  " 
  is 
  a 
  pair 
  

   of 
  short 
  columnals 
  equaling 
  in 
  length 
  the 
  single 
  one 
  interposed. 
  

  

  The 
  type 
  locality 
  is 
  given 
  as 
  Indian 
  Creek, 
  Montgomery 
  County, 
  

   Indiana, 
  and 
  it 
  is 
  from 
  there 
  that 
  the 
  two 
  specimens, 
  together 
  with 
  

   three 
  others 
  subsequently 
  acquired, 
  were 
  derived. 
  In 
  one 
  of 
  the 
  

   latter 
  the 
  stem 
  is 
  preserved 
  to 
  nearly 
  its 
  full 
  length, 
  showing 
  its 
  

   broad 
  and 
  open 
  curve 
  (pi. 
  7, 
  fig. 
  5). 
  The 
  original 
  of 
  Wachsmuth 
  

   and 
  Springer's 
  figure 
  1 
  is 
  from 
  another 
  locality 
  and 
  a 
  somewhat 
  

   higher 
  horizon; 
  it 
  has 
  a 
  different 
  arrangement 
  of 
  columnals 
  and 
  

   cirri 
  — 
  a 
  form 
  for 
  which 
  I 
  have 
  proposed 
  the 
  species 
  C. 
  crawfords- 
  

   villensis. 
  While 
  it 
  is 
  true 
  that 
  the 
  description 
  of 
  the 
  crown 
  was 
  made 
  

   from 
  this 
  specimen, 
  there 
  is 
  nothing 
  substantially 
  distinctive 
  about 
  

   it, 
  and 
  as 
  in 
  our 
  present 
  view 
  the 
  decisive 
  specific 
  characters 
  in 
  these 
  

   forms 
  are 
  to 
  be 
  looked 
  for 
  in 
  the 
  stem, 
  that 
  fact 
  may 
  be 
  disregarded. 
  

  

  In 
  the 
  character 
  of 
  multiple 
  cirri 
  springing 
  from 
  a 
  pair 
  of 
  short 
  

   columnals, 
  this 
  species 
  takes 
  on 
  a 
  plan 
  which 
  became 
  the 
  leading 
  

   character 
  in 
  the 
  later 
  Carboniferous 
  forms. 
  

  

  Horizon 
  and 
  locality. 
  — 
  Mississippian, 
  Keokuk 
  limestone, 
  lower 
  

   horizon; 
  Indian 
  Creek, 
  Montgomery 
  County, 
  Indiana. 
  

  

  