﻿art 
  9 
  UNUSUAL 
  FORMS 
  OF 
  FOSSIL 
  CRINOIDS 
  SPRINGER 
  13 
  

  

  even 
  when 
  detached 
  the 
  taper 
  in 
  width 
  of 
  the 
  stem 
  for 
  some 
  dis- 
  

   tance 
  back 
  is 
  plain 
  to 
  the 
  eye. 
  The 
  diminution 
  is 
  decisively 
  shown 
  

   by 
  measurements. 
  In 
  six 
  specimens 
  having 
  the 
  stem 
  complete 
  to 
  the 
  

   narrow 
  distal 
  end, 
  with 
  diameters 
  of 
  coil 
  from 
  20 
  mm. 
  down 
  to 
  12 
  

   mm., 
  the 
  diminution 
  from 
  the 
  widest 
  median 
  part 
  to 
  the 
  distal 
  end 
  

   is 
  from 
  5 
  — 
  5-^-4 
  — 
  1 
  — 
  3 
  — 
  2.5 
  mm. 
  down 
  to 
  1 
  mm. 
  or 
  less; 
  whereas 
  in 
  

   the 
  five 
  largest 
  specimens 
  of 
  the 
  open-coiled 
  form, 
  with 
  diameters 
  

   in 
  the 
  corresponding 
  part 
  of 
  the 
  coil 
  of 
  from 
  24 
  to 
  14 
  mm., 
  the 
  aver- 
  

   age 
  maximum 
  width 
  is 
  3 
  mm., 
  only 
  reaching 
  4 
  mm. 
  in 
  one 
  case 
  ; 
  and 
  

   this 
  width 
  is 
  in 
  most 
  cases 
  maintained 
  with 
  but 
  little 
  diminution 
  so 
  far 
  

   as 
  the 
  stem 
  is 
  preserved. 
  In 
  the 
  largest 
  specimen, 
  with 
  stem 
  extend- 
  

   ing 
  about 
  8 
  cm. 
  beyond 
  the 
  coil, 
  the 
  width 
  is 
  still 
  3 
  mm. 
  at 
  the 
  in- 
  

   complete 
  distal 
  end. 
  In 
  one 
  of 
  the 
  six 
  close-coiled 
  specimens 
  above 
  

   mentioned, 
  having 
  diameters 
  of 
  12 
  and 
  14 
  mm., 
  the 
  distal 
  portion 
  

   diminishes 
  in 
  width 
  from 
  4 
  mm. 
  to 
  a 
  point 
  in 
  a 
  distance 
  of 
  only 
  two 
  

   and 
  a 
  half 
  times 
  its 
  maximum 
  width. 
  

  

  In 
  the 
  present 
  species 
  the 
  involute, 
  or 
  bilateral, 
  portion 
  of 
  the 
  stem 
  

   is 
  limited 
  to 
  about 
  one 
  and 
  a 
  half 
  convolutions 
  with 
  diameters 
  rang- 
  

   ing 
  from 
  9 
  mm. 
  to 
  a 
  maximum 
  of 
  24 
  mm., 
  while 
  in 
  the 
  open-coiled 
  

   form 
  there 
  may 
  be 
  one 
  or 
  two 
  more 
  loose 
  coils, 
  with 
  the 
  stem 
  ex- 
  

   tending 
  still 
  farther 
  in 
  a 
  broad 
  curve, 
  or 
  nearly 
  straight. 
  

  

  In 
  many 
  of 
  the 
  specimens 
  the 
  two 
  outer 
  longitudinal 
  sutures, 
  rem- 
  

   nants 
  of 
  the 
  primitive 
  five 
  by 
  which 
  the 
  stem 
  was 
  originally 
  divided, 
  

   are 
  very 
  prominent 
  (pi. 
  2, 
  fig. 
  2a), 
  and 
  the 
  stem 
  between 
  them 
  is 
  

   often 
  raised 
  into 
  a 
  rounded 
  ridge, 
  as 
  mentioned 
  by 
  Bather 
  under 
  

   H. 
  ammonis? 
  

  

  There 
  is 
  no 
  doubt 
  that 
  this 
  form, 
  with 
  its 
  abbreviated 
  and 
  root- 
  

   less 
  stem, 
  led 
  a 
  free 
  life 
  ; 
  whereas 
  it 
  is 
  probable 
  that 
  the 
  other 
  form, 
  

   with 
  elongate 
  stem, 
  was 
  sessile, 
  temporarily 
  or 
  permanently. 
  

  

  In 
  addition 
  to 
  the 
  specimens 
  from 
  the 
  Decatur 
  County 
  area, 
  I 
  

   have 
  about 
  an 
  equal 
  number 
  from 
  the 
  Waldron 
  shale 
  at 
  Newsom, 
  

   Tenn., 
  which 
  I 
  am 
  unable 
  to 
  distinguish 
  from 
  them 
  by 
  any 
  characters 
  

   disclosed 
  in 
  the 
  fossils, 
  and 
  which 
  have 
  a 
  remarkable 
  uniformity 
  in 
  

   the 
  characters 
  above 
  desscribed. 
  Hence 
  notwithstanding 
  the 
  dif- 
  

   ference 
  in 
  horizon, 
  they 
  will 
  with 
  our 
  present 
  knowledge 
  have 
  to 
  be 
  

   referred 
  to 
  the 
  same 
  species. 
  So 
  far 
  as 
  observed, 
  the 
  form 
  with 
  the 
  

   open 
  coil 
  does 
  not 
  occur 
  at 
  the 
  Waldron 
  locality. 
  

  

  This 
  description 
  is 
  based 
  upon 
  about 
  forty 
  specimens, 
  almost 
  

   equally 
  divided 
  between 
  the 
  two 
  localities. 
  

  

  Horizon 
  and 
  locality. 
  — 
  Silurian, 
  Brownsport 
  formation; 
  Decatur 
  

   County, 
  Tennessee; 
  and 
  Waldron 
  shale, 
  at 
  Newsom, 
  Tennessee. 
  A 
  

   small 
  fragment 
  from 
  St. 
  Paul, 
  Indiana, 
  shows 
  that 
  this 
  or 
  the 
  fol- 
  

  

  " 
  Crinoidea 
  of 
  Gotland, 
  p. 
  51. 
  

  

  