﻿art 
  9 
  UNUSUAL. 
  FORMS 
  OF 
  FOSSIL 
  CRINOIDS 
  SPRINGER 
  87 
  

  

  typical 
  Hydreionocrinus 
  with 
  a 
  more 
  or 
  less 
  broadly 
  rounded 
  cup 
  

   and 
  concaye 
  base; 
  in 
  all, 
  the 
  arms 
  are 
  composed 
  of 
  wedge-form 
  

   brachials, 
  and 
  the 
  branching 
  is 
  more 
  or 
  less 
  of 
  the 
  heterotomous 
  type, 
  

   not 
  always 
  very 
  distinct. 
  

  

  The 
  first 
  two, 
  both 
  from 
  the 
  lower 
  Burlington 
  limestone, 
  have 
  a 
  

   true 
  balloon-shaped 
  ventral 
  sac, 
  with 
  a 
  narrow 
  neck 
  supporting 
  a 
  

   widely 
  expanding 
  bag 
  above 
  it, 
  composed 
  of 
  numerous 
  plates 
  sharply 
  

   sculptured 
  or 
  rising 
  into 
  angular 
  nodes; 
  whereas 
  the 
  third, 
  from 
  

   the 
  Upper 
  Burlington 
  formation, 
  having 
  likewise 
  a 
  narrow 
  neck, 
  

   takes 
  on 
  the 
  mushroom 
  form, 
  spreading 
  out 
  into 
  a 
  flattened 
  disk, 
  

   composed 
  of 
  rather 
  numerous 
  plates, 
  some 
  of 
  which 
  are 
  produced 
  into 
  

   spines 
  of 
  variable 
  length, 
  like 
  those 
  of 
  the 
  later 
  appearing 
  Hydre- 
  

   ionocrinus. 
  

  

  The 
  differences 
  between 
  the 
  first 
  two 
  as 
  claimed 
  bv 
  their 
  author 
  are 
  

   rather 
  slight, 
  but 
  between 
  them 
  and 
  the 
  third 
  the 
  distinction 
  is 
  very 
  

   great, 
  the 
  spiniferous 
  flattened 
  top 
  being 
  constant 
  in 
  15 
  specimens 
  

   from 
  the 
  upper 
  Burlington 
  bed, 
  as 
  against 
  about 
  25 
  from 
  the 
  lower 
  

   in 
  which 
  the 
  sac 
  is 
  always 
  rounded 
  and 
  non-spiniferous 
  ; 
  only 
  two 
  

   or 
  three 
  somewhat 
  intermediate 
  specimens 
  have 
  been 
  seen. 
  As 
  be- 
  

   tween 
  the 
  lower 
  bed 
  species, 
  the 
  author 
  notes 
  that 
  in 
  G. 
  ventricosus 
  

   the 
  second 
  radials 
  (IBr) 
  are 
  smaller 
  than 
  the 
  first, 
  and 
  the 
  arms 
  

   more 
  distinctly 
  wedge-form, 
  while 
  in 
  C. 
  dilatatus 
  the 
  second 
  radials 
  

   are 
  larger 
  than 
  the 
  first 
  and 
  united 
  at 
  their 
  lateral 
  margins; 
  and 
  

   that 
  in 
  the 
  former 
  the 
  sac 
  is 
  composed 
  of 
  large 
  plates 
  in 
  the 
  lower 
  

   part 
  and 
  smaller 
  in 
  the 
  upper, 
  which 
  is 
  the 
  reverse 
  of 
  the 
  latter. 
  

   Taking 
  the 
  specimens 
  as 
  they 
  come 
  these 
  differences 
  seem 
  not 
  to 
  

   be 
  very 
  constant, 
  but 
  on 
  the 
  whole 
  the 
  plates 
  of 
  the 
  sac 
  at 
  the 
  distal 
  

   part 
  appear 
  generally 
  larger 
  in 
  G. 
  dilatatus 
  than 
  in 
  G. 
  ventricosus. 
  

  

  As 
  all 
  three 
  of 
  these 
  species 
  were 
  described 
  without 
  illustrations, 
  

   paleontologists 
  will 
  welcome 
  the 
  publication 
  of 
  adequate 
  figures 
  now. 
  

   I 
  am 
  giving 
  photographs 
  of 
  the 
  types 
  of 
  G. 
  dilatatus 
  and 
  G. 
  ventri- 
  

   cosus 
  now 
  in 
  my 
  possession, 
  formerly 
  in 
  the 
  collection 
  of 
  Dr. 
  C. 
  A. 
  

   White, 
  together 
  with 
  some 
  other 
  specimens 
  showing 
  the 
  characters 
  of 
  

   the 
  species 
  more 
  completely; 
  also 
  of 
  characteristic 
  specimens 
  of 
  G. 
  

   subspinosus 
  as 
  well 
  known 
  to 
  the 
  Burlington 
  collectors. 
  In 
  none 
  

   of 
  the 
  40 
  specimens 
  of 
  the 
  three 
  species 
  is 
  the 
  position 
  of 
  the 
  anal 
  

   opening 
  disclosed, 
  but 
  it 
  must 
  be 
  at 
  some 
  point 
  below 
  the 
  inflated 
  

   portion 
  of 
  the 
  sac. 
  

  

  I 
  am 
  also 
  figuring 
  two 
  specimens 
  of 
  the 
  inflated 
  sac 
  of 
  one 
  or 
  both 
  

   the 
  lower 
  Burlington 
  species 
  from 
  the 
  equivalent 
  horizon 
  in 
  southern 
  

   New 
  Mexico 
  discovered 
  by 
  me 
  in 
  1883, 
  50 
  showing 
  the 
  great 
  geo- 
  

   graphical 
  range 
  of 
  this 
  highly 
  specialized 
  form. 
  

  

  B0 
  Sprigner. 
  On 
  the 
  Occurrence 
  of 
  the 
  lower 
  Burlington, 
  limestone 
  in 
  New 
  Mexico, 
  

   Amer. 
  Journ. 
  Sci., 
  vol. 
  25, 
  1884, 
  pp. 
  97-103. 
  

  

  