﻿80 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL. 
  MUSEUM 
  vol.67 
  

  

  has 
  a 
  wide 
  anal 
  area, 
  with 
  posterior 
  basal 
  broadly 
  truncate 
  and 
  a 
  

   short 
  and 
  broad 
  radianal, 
  as 
  is 
  the 
  case 
  with 
  all 
  Burlington 
  and 
  

   Keokuk 
  species. 
  Form 
  of 
  the 
  sac 
  is 
  unknown, 
  but 
  from 
  the 
  shape 
  

   of 
  the 
  crown 
  is 
  probably 
  similar 
  to 
  that 
  of 
  Z. 
  elegans, 
  which 
  the 
  

   species 
  also 
  strongly 
  resembles 
  in 
  the 
  short, 
  quadrangular 
  brachials, 
  

   and 
  mode 
  of 
  branching 
  of 
  the 
  arms. 
  

  

  There 
  is 
  an 
  undescribed 
  species 
  from 
  the 
  Keokuk 
  limestone 
  at 
  

   Indian 
  Creek, 
  Indiana, 
  represented 
  by 
  several 
  specimens, 
  with 
  a 
  

   turbinate 
  calyx 
  like 
  bursaeformis, 
  but 
  otherwise 
  a 
  good 
  Zeacrinus. 
  

  

  ZEACRINUS 
  ELEGANS 
  Hall 
  

  

  Plate 
  21, 
  figs. 
  2-4 
  

  

  Zeacrinus 
  elegans 
  Hall, 
  Geol. 
  Iowa, 
  pt. 
  2, 
  185S, 
  p. 
  547, 
  pi. 
  9, 
  figs. 
  1, 
  2. 
  

   Upper 
  Burlington 
  limestone; 
  Burlington, 
  Iowa. 
  

  

  The 
  true 
  Zeacrinus 
  of 
  the 
  earlier 
  type, 
  with 
  depressed 
  calyx, 
  post. 
  

   B 
  broadly 
  truncate, 
  RA 
  short 
  and 
  wide, 
  not 
  passing 
  down 
  between 
  

   BB. 
  This 
  structure 
  is 
  uniform 
  in 
  28 
  specimens 
  showing 
  the 
  anal 
  

   side; 
  and 
  in 
  a 
  total 
  of 
  43 
  specimens 
  all 
  have 
  a 
  single 
  IBr, 
  axillary, 
  

   in 
  four 
  rays, 
  and 
  3 
  or 
  4 
  in 
  the 
  anterior. 
  There 
  are 
  6 
  to 
  11 
  arms 
  to 
  

   the 
  ray, 
  usually 
  8 
  or 
  10. 
  In 
  this 
  species 
  we 
  have 
  the 
  expanded, 
  club- 
  

   shaped 
  sac, 
  lying 
  well 
  within 
  the 
  arms, 
  in 
  marked 
  contrast 
  to 
  that 
  of 
  

   the 
  Chester 
  species. 
  I 
  am 
  figuring 
  a 
  good 
  example 
  of 
  this, 
  also 
  

   another 
  to 
  show 
  the 
  range 
  of 
  variation 
  in 
  number 
  of 
  arms, 
  and 
  an- 
  

   other 
  of 
  smaller 
  size. 
  The 
  opening 
  has 
  not 
  been 
  observed. 
  The 
  

   other 
  Burlington 
  and 
  most 
  of 
  the 
  Keokuk 
  species 
  are 
  true 
  to 
  this 
  

   type, 
  with 
  variations 
  as 
  to 
  minor 
  details. 
  

  

  ZEACRINUS 
  COMMATICUS 
  S. 
  A. 
  Miller 
  

  

  Plate 
  22, 
  figs. 
  l-3a 
  

  

  Zeacrinus 
  commaticus 
  S. 
  A. 
  Millek, 
  Geol. 
  Surv. 
  Missouri, 
  Bull. 
  4, 
  1891, 
  

  

  p. 
  36, 
  pi. 
  5. 
  figs. 
  10, 
  11. 
  

   Upper 
  part 
  Keokuk 
  limestone 
  ; 
  Boonville, 
  Missouri. 
  

  

  A 
  species 
  remarkable 
  for 
  the 
  introduction 
  within 
  the 
  genus 
  of 
  a 
  

   new 
  type 
  of 
  sac, 
  which 
  rises 
  above 
  the 
  limits 
  of 
  the 
  arms, 
  and 
  has 
  

   the 
  anal 
  opening 
  at 
  the 
  base. 
  The 
  term 
  " 
  club-shaped 
  " 
  is 
  especially 
  

   well 
  adapted 
  to 
  this 
  sac, 
  as 
  it 
  is 
  in 
  form 
  a 
  veritable 
  war 
  club, 
  with 
  

   a 
  strong 
  handle 
  and 
  knotted 
  end. 
  The 
  species 
  is 
  abundant 
  and 
  

   strongly 
  marked. 
  It 
  has 
  the 
  broadly 
  truncate 
  post. 
  B, 
  with 
  short 
  

   RA, 
  of 
  the 
  earlier 
  type, 
  49 
  specimens 
  being 
  all 
  in 
  that 
  condition 
  

   with 
  little 
  variation; 
  and 
  of 
  these 
  37 
  have 
  one 
  IBr 
  in 
  four 
  rays, 
  

   and 
  12 
  have 
  two 
  IBr 
  all 
  around 
  — 
  an 
  exceptional 
  occurrence 
  for 
  the 
  

   genus, 
  but 
  one 
  which 
  is 
  repeated 
  in 
  the 
  latest 
  species. 
  The 
  project- 
  

   ing 
  part 
  of 
  the 
  sac 
  with 
  its 
  rounded 
  nodes 
  is 
  shown 
  in 
  many 
  speci- 
  

   mens, 
  and 
  its 
  full 
  length 
  with 
  the 
  anal 
  opening 
  in 
  two. 
  

  

  