﻿88 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL, 
  MUSEUM 
  vol.67 
  

  

  Horizon 
  and 
  locality. 
  — 
  Mississippian, 
  lower 
  and 
  upper 
  Burlington 
  

   limestone 
  as 
  above 
  stated; 
  Burlington, 
  Iowa, 
  and 
  Lake 
  Valley, 
  New 
  

   Mexico. 
  

  

  COELIOCRINUS 
  LYRA 
  (Meek 
  and 
  Worthen) 
  

  

  Zeacrinus 
  lyra 
  Meek 
  and 
  Worthen, 
  Geol. 
  Surv. 
  Illinois, 
  vol. 
  5, 
  1873, 
  p. 
  432, 
  

  

  pi. 
  1, 
  figs. 
  11a, 
  b. 
  

   Lower 
  Burlington 
  limestone 
  ; 
  Burlington, 
  Iowa. 
  

  

  This 
  species 
  has 
  been 
  referred 
  to 
  Coeliocrinus. 
  The 
  figures 
  do 
  not 
  

   show 
  the 
  sac, 
  but 
  the 
  description 
  says 
  that 
  one 
  specimen 
  shows 
  "a 
  

   ventral 
  prolongation 
  nearly 
  as 
  long 
  as 
  the 
  arms, 
  somewhat 
  expanded 
  

   and 
  covered 
  with 
  spines 
  at 
  the 
  upper 
  extremity." 
  It 
  has 
  the 
  strictly 
  

   heterotomous 
  arms 
  of 
  Zeacrinus, 
  with 
  numerous 
  branches 
  from 
  the 
  

   outer 
  arm 
  to 
  the 
  inner 
  side 
  of 
  the 
  dichotom; 
  but 
  the 
  wedge-shaped 
  

   brachials 
  exclude 
  it 
  from 
  that 
  genus. 
  

  

  Another 
  species, 
  Zeacrinus 
  dubius 
  of 
  Miller 
  and 
  Gurley, 
  51 
  from 
  

   the 
  Keokuk 
  at 
  Bono, 
  Indiana, 
  is 
  almost 
  a 
  duplicate 
  of 
  O 
  oeliocrinus 
  

   subspinosus. 
  

  

  Genus 
  HYDREIONOCRINUS 
  De 
  Koninck 
  

  

  Plates 
  25, 
  26 
  

  

  Hydreionocrinus 
  De 
  Koninck, 
  Bull. 
  Acad. 
  Royale 
  Belgique, 
  vol. 
  8, 
  1858, 
  

   pt. 
  2, 
  p. 
  13. 
  — 
  Wachsmuth 
  and 
  Springer, 
  Rev. 
  Pal., 
  pt. 
  1, 
  1879, 
  p. 
  129 
  ; 
  

   pt. 
  3, 
  1SS6, 
  p. 
  245.— 
  Bather, 
  Trans. 
  Edinb. 
  Geol. 
  Soc, 
  vol. 
  10, 
  pt. 
  1, 
  

   1911-12, 
  pp. 
  61-76.— 
  Wright, 
  Trans. 
  Geol. 
  Soc. 
  Glasgow, 
  vol. 
  16, 
  1917- 
  

   18, 
  pp. 
  364-383. 
  — 
  Wanner, 
  Permischen 
  Echinod. 
  von 
  Timor, 
  1916, 
  pp. 
  

   150-166. 
  

  

  Lower 
  Carboniferous 
  to 
  Upper 
  Carboniferous. 
  

  

  The 
  distinctive 
  character 
  of 
  this 
  genus, 
  having 
  the 
  form 
  of 
  calyx 
  

   and 
  arrangement 
  of 
  anal 
  plates 
  substantially 
  as 
  in 
  Zeacrinus, 
  is 
  the 
  

   ventral 
  sac, 
  which 
  at 
  the 
  distal 
  end 
  is 
  transversely 
  flattened 
  like 
  a 
  

   mushroom, 
  abruptly 
  spreading 
  beyond 
  the 
  tips 
  of 
  the 
  arms 
  and 
  

   forming 
  a 
  low 
  canopy 
  composed 
  of 
  5 
  to 
  35 
  or 
  more 
  plates; 
  these 
  

   are 
  either 
  a 
  few, 
  spiniferous 
  and 
  meeting 
  towards 
  the 
  middle, 
  or 
  

   more 
  frequently 
  many 
  nodose 
  or 
  flattened 
  plates 
  in 
  the 
  middle 
  part, 
  

   irregularly 
  arranged, 
  and 
  bordered 
  at 
  the 
  margin 
  by 
  a 
  connected 
  

   ring 
  of 
  spiniferous 
  plates. 
  This 
  wide 
  spreading 
  sac 
  is 
  supported 
  by 
  

   a 
  narrow 
  tube, 
  in 
  which 
  the 
  anal 
  opening 
  is 
  at 
  the 
  anterior 
  side 
  

   about 
  midway, 
  as 
  now 
  shown 
  by 
  three 
  specimens. 
  The 
  cup 
  is 
  de- 
  

   pressed, 
  rounded, 
  bowl-shaped, 
  with 
  the 
  infrabasals, 
  and 
  sometimes 
  

   basals 
  also, 
  sunken 
  in 
  a 
  more 
  or 
  less 
  deep 
  cavity. 
  This 
  form 
  of 
  cup, 
  

   and 
  the 
  constant 
  presence 
  of 
  spines 
  on 
  the 
  sac 
  and 
  on 
  many 
  of 
  the 
  

   brachial 
  axillaries, 
  distinguish 
  the 
  genus 
  from 
  Coeliocrinus, 
  of 
  

  

  n 
  Journ. 
  Cincinnati 
  Soc. 
  Nat. 
  Hist., 
  1S90, 
  p. 
  44, 
  pi. 
  7, 
  figs. 
  7, 
  8. 
  

  

  