﻿art 
  9 
  UK 
  USUAL 
  FORMS 
  OF 
  FOSSIL 
  CRINOIDS 
  SPRINGER 
  57 
  

  

  and 
  the 
  column 
  facet 
  present 
  (pi. 
  15, 
  figs. 
  10, 
  11) 
  ; 
  and 
  also 
  a 
  few 
  

   have 
  portions 
  of 
  arms. 
  In 
  the 
  remainder 
  the 
  infrabasals 
  are 
  fused. 
  

  

  From 
  the 
  Chester 
  region, 
  upper 
  Okaw, 
  equivalent 
  to 
  the 
  Glen 
  

   Dean 
  formation 
  of 
  Kentucky, 
  in 
  Randolph 
  and 
  adjoining 
  counties 
  

   in 
  southern 
  Illinois, 
  from 
  which 
  most 
  of 
  the 
  described 
  species 
  have 
  

   been 
  derived, 
  there 
  are 
  about 
  70 
  specimens; 
  in 
  about 
  60 
  of 
  these 
  all 
  

   traces 
  of 
  infrabasal 
  sutures 
  are 
  absent, 
  while 
  in 
  10 
  these 
  plates 
  are 
  

   divided, 
  and 
  traces 
  of 
  column 
  facet 
  visible. 
  The 
  specimens 
  range 
  

   from 
  8 
  to 
  20 
  mm. 
  in 
  diameter. 
  Roemer's 
  type 
  is 
  19 
  mm. 
  wide, 
  and 
  

   shows 
  a 
  sutural 
  division 
  at 
  the 
  upper 
  part 
  of 
  the 
  infrabasals, 
  but 
  

   no 
  trace 
  of 
  a 
  column 
  facet. 
  

  

  Among 
  the 
  15 
  described 
  species, 
  as 
  shown 
  by 
  the 
  descriptions 
  and 
  

   figures, 
  the 
  following 
  have 
  the 
  infrabasals 
  completely 
  fused, 
  and 
  all 
  

   trace 
  of 
  column 
  absent: 
  A. 
  conicus, 
  A. 
  dactylif 
  omnia, 
  A. 
  laevis, 
  A. 
  

   gibbosus, 
  A. 
  Chester 
  >ensis, 
  A. 
  dissimilis, 
  and 
  A. 
  carbonarius,=7. 
  

   These 
  have 
  the 
  infrabasals 
  divided, 
  and 
  a 
  column 
  facet 
  present: 
  A. 
  

   occidentalism 
  A. 
  tumidus, 
  A. 
  constrictus, 
  A. 
  papillatus, 
  A. 
  penta- 
  

   gonus, 
  and 
  A. 
  globosus,=Q. 
  Of 
  the 
  remaining 
  two, 
  A. 
  hemispher- 
  

   icus 
  and 
  A. 
  ovalis, 
  the 
  figures 
  show 
  the 
  infrabasals 
  divided, 
  but 
  the 
  

   descriptions 
  say 
  there 
  is 
  no 
  evidence 
  of 
  a 
  column. 
  Thus 
  at 
  least 
  40 
  

   per 
  cent 
  of 
  the 
  described 
  species 
  had 
  a 
  column, 
  and 
  there 
  is 
  nothing 
  

   in 
  either 
  figures 
  or 
  descriptions 
  to 
  indicate 
  that 
  these 
  were 
  based 
  

   upon 
  immature 
  individuals. 
  

  

  On 
  examining 
  the 
  specimens 
  with 
  reference 
  to 
  the 
  fusion 
  of 
  the 
  

   base 
  several 
  conditions 
  will 
  be 
  found 
  : 
  some 
  have 
  the 
  infrabasals 
  

   completely 
  anchylosed 
  — 
  usually 
  a 
  good 
  sized 
  cone; 
  some 
  have 
  them 
  

   well 
  divided, 
  with 
  a 
  facet 
  suitable 
  for 
  the 
  attachment 
  of 
  the 
  column 
  ; 
  

   in 
  some 
  they 
  appear 
  divided 
  only 
  at 
  the 
  inside 
  of 
  the 
  cup; 
  still 
  

   others 
  have 
  a 
  more 
  or 
  less 
  imperfect 
  division, 
  with 
  suture 
  lines 
  

   ragged 
  or 
  curving 
  (pi. 
  15, 
  figs. 
  18, 
  19), 
  as 
  if 
  in 
  a 
  transition 
  state, 
  or 
  

   one 
  in 
  which 
  the 
  sharp 
  definition 
  of 
  the 
  suture 
  is 
  hindered 
  by 
  a 
  

   restricted 
  mode 
  of 
  growth, 
  accompanied 
  by 
  the 
  formation 
  of 
  zigzag 
  

   radiating 
  nerve 
  canals, 
  passing 
  out 
  into 
  the 
  wall 
  of 
  the 
  cup 
  instead 
  

   of 
  down 
  into 
  a 
  stem 
  (pi. 
  15, 
  fig. 
  24). 
  

  

  In 
  1882 
  Whitfield 
  described 
  a 
  species 
  from 
  the 
  upper 
  zone 
  of 
  the 
  

   Maxville 
  formation 
  of 
  Ohio, 
  equivalent 
  to 
  the 
  Glen 
  Dean 
  of 
  Ken- 
  

   tucky, 
  under 
  the 
  name 
  Cyathocrinus 
  inequidactylus. 
  zs 
  Some 
  years 
  

   afterwards, 
  finding 
  the 
  name 
  preoccupied, 
  he 
  republished 
  the 
  de- 
  

   scription, 
  changing 
  the 
  specific 
  name 
  to 
  C. 
  maxvillensis.™ 
  He 
  had 
  

   three 
  specimens, 
  of 
  which 
  he 
  gave 
  good 
  figures, 
  the 
  arms 
  being 
  

   partly 
  preserved 
  in 
  two 
  of 
  them. 
  The 
  distinctive 
  character 
  of 
  the 
  

  

  88 
  Ann. 
  New 
  York 
  Acad. 
  Sci., 
  vol. 
  2, 
  p. 
  219, 
  pi. 
  9, 
  figs. 
  5-8. 
  

  

  s9 
  Idem. 
  vol. 
  3, 
  Feb. 
  3 
  891, 
  p. 
  577, 
  pi. 
  13, 
  figs. 
  5-8 
  ; 
  Geol. 
  Surv. 
  Ohio, 
  vol. 
  8, 
  1893, 
  p. 
  465, 
  

   pi. 
  9, 
  figs. 
  5-8. 
  

  

  