﻿aet9 
  UNUSUAL 
  FORMS 
  OF 
  FOSSIL 
  CRINOIDS 
  SPRINGER 
  37 
  

  

  In 
  the 
  series 
  of 
  specimens 
  obtained 
  there 
  are 
  14 
  individuals, 
  and 
  

   in 
  all 
  of 
  them, 
  without 
  a 
  single 
  exception, 
  the 
  arms 
  are 
  firmly 
  and 
  

   regularly 
  fixed 
  in 
  the 
  position 
  above 
  described 
  — 
  a 
  fact 
  which 
  seems 
  

   to 
  warrant 
  the 
  conclusion 
  that 
  this 
  habitus 
  is 
  associated 
  with 
  a 
  

   definite 
  structure, 
  and 
  is 
  not 
  a 
  temporary 
  condition 
  due 
  to 
  casual 
  

   movements 
  of 
  highly 
  flexible 
  appendages. 
  

  

  As 
  to 
  minor 
  details: 
  The 
  anal 
  series 
  is 
  strongly 
  developed 
  in 
  

   this 
  species, 
  forming 
  a 
  more 
  prominent 
  ridge 
  than 
  usual 
  in 
  the 
  

   Silurian 
  species, 
  being 
  especially 
  conspicuous 
  when 
  seen 
  from 
  the 
  

   tegmen. 
  The 
  stem 
  is 
  constructed 
  of 
  very 
  short 
  columnals, 
  one 
  of 
  

   which 
  projects 
  at 
  intervals 
  of 
  five 
  or 
  six, 
  with 
  a 
  beaded 
  perimeter. 
  

  

  In 
  point 
  of 
  size, 
  this 
  species 
  presents 
  a 
  wide 
  difference 
  from 
  all 
  

   the 
  others, 
  which, 
  as 
  stated, 
  are 
  usually 
  small, 
  the 
  largest, 
  and 
  latest 
  

   in 
  age, 
  M. 
  meeki 
  Lyon, 
  of 
  the 
  later 
  Niagaran, 
  having 
  the 
  calyx 
  20 
  

   mm. 
  high 
  and 
  22 
  mm. 
  wide 
  at 
  the 
  arm 
  bases 
  ; 
  whereas 
  our 
  two 
  speci- 
  

   mens 
  with 
  the 
  calyx 
  exposed 
  are 
  about 
  25 
  mm. 
  high 
  and 
  25 
  mm. 
  

   wide 
  at 
  the 
  arm 
  bases. 
  Measured 
  from 
  the 
  surface 
  of 
  the 
  tegmen 
  

   to 
  the 
  distal 
  end 
  of 
  the 
  pendent 
  arms 
  where 
  they 
  close 
  around 
  the 
  

   stem, 
  and 
  in 
  width 
  over 
  all 
  at 
  the 
  outside 
  of 
  the 
  pinnules, 
  these 
  

   dimensions 
  are 
  about 
  35 
  mm. 
  and 
  32 
  mm. 
  respectively. 
  In 
  figure 
  

   1, 
  and 
  in 
  two 
  other 
  specimens 
  not 
  figured, 
  the 
  same 
  measurements 
  

   give 
  40 
  mm. 
  in 
  height 
  and 
  37 
  mm. 
  in 
  width. 
  

  

  But 
  this 
  by 
  no 
  means 
  represents 
  the 
  maximum 
  dimensions 
  of 
  the 
  

   species, 
  for 
  among 
  the 
  14 
  specimens, 
  all 
  from 
  the 
  same 
  layer 
  and 
  

   locality, 
  are 
  two 
  from 
  which 
  the 
  calyx, 
  including 
  tegmen 
  and 
  arm 
  

   bases, 
  is 
  broken 
  away, 
  that 
  were 
  more 
  than 
  three 
  times 
  as 
  large. 
  

   Only 
  the 
  hollow 
  shell 
  remains, 
  containing 
  the 
  closely 
  apposed 
  arms 
  

   from 
  an 
  irregular 
  fractured 
  edge 
  below 
  the 
  arm 
  bases 
  to 
  the 
  distal 
  

   end. 
  That 
  much 
  of 
  the 
  crown 
  is 
  12.5 
  cm. 
  high 
  and 
  7.5 
  cm. 
  wide. 
  

   Inasmuch 
  as 
  one-seventh 
  of 
  the 
  individuals 
  attain 
  this 
  great 
  size, 
  

   it 
  is 
  clear 
  that 
  the 
  optimum 
  for 
  this 
  species 
  is 
  far 
  beyond 
  that 
  for 
  

   any 
  of 
  the 
  Silurian 
  forms. 
  

  

  Horizon 
  and 
  locality. 
  — 
  Lower 
  Devonian, 
  Oriskany; 
  Cumberland, 
  

   Maryland. 
  The 
  specimens 
  occur 
  in 
  a 
  friable 
  calcareous 
  sandstone, 
  

   associated 
  with 
  Edriocrinus, 
  Technocrinus, 
  and 
  numerous 
  other 
  

   forms 
  peculiar 
  to 
  that 
  horizon. 
  The 
  fossils 
  as 
  found 
  have 
  been 
  

   leached 
  by 
  the 
  percolation 
  of 
  water, 
  carrying 
  away 
  the 
  calcareous 
  

   material, 
  and 
  partially 
  replacing 
  it 
  by 
  silica. 
  By 
  this 
  leaching 
  

   the 
  finer 
  surface 
  markings 
  have 
  been 
  obliterated. 
  The 
  series 
  of 
  

   specimens 
  under 
  consideration 
  are 
  part 
  of 
  a 
  large 
  collection 
  made 
  

   by 
  Frank 
  Hartley 
  and 
  acquired 
  by 
  me 
  many 
  years 
  ago; 
  but 
  they 
  

   have 
  remained 
  undescribed 
  until 
  now 
  for 
  want 
  of 
  time. 
  

  

  Some 
  other 
  occurrences 
  of 
  this 
  nature, 
  not 
  all 
  new 
  species, 
  which 
  

   should 
  be 
  further 
  illustrated, 
  will 
  be 
  here 
  discussed. 
  

  

  