﻿abt9 
  UNUSUAL 
  FORMS 
  OF 
  FOSSIL 
  CRINOIDS 
  SPRINGER 
  91 
  

  

  HoHzon 
  and 
  locality. 
  — 
  Mississippian; 
  Glen 
  Dean 
  formation 
  of 
  the 
  

   upper 
  Chester; 
  Sloan's 
  Valley, 
  Pulaski 
  County, 
  and 
  Grayson 
  

   Springs, 
  Kentucky. 
  Most 
  of 
  the 
  specimens 
  of 
  both 
  species 
  came 
  

   from 
  the 
  same 
  locality 
  at 
  Sloan's 
  Valley, 
  within 
  a 
  distance 
  of 
  a 
  

   few 
  hundred 
  feet; 
  but 
  as 
  the 
  collection, 
  was 
  made 
  from 
  the 
  debris 
  

   of 
  a 
  tunnel 
  excavation, 
  they 
  may 
  not 
  have 
  been 
  derived 
  from 
  the 
  

   same 
  layer, 
  although 
  the 
  matrix 
  and 
  lithological 
  appearance 
  are 
  

   identical. 
  Both 
  species 
  also 
  occur 
  at 
  Grayson 
  Springs 
  in 
  the 
  same 
  

   formation, 
  but 
  whether 
  in 
  the 
  same 
  layer 
  is 
  not 
  known. 
  They 
  have 
  

   not 
  been 
  recognized 
  in 
  other 
  Chester 
  localities. 
  

  

  For 
  completion 
  of 
  the 
  series 
  under 
  this 
  group 
  I 
  am 
  figuring 
  some 
  

   representative 
  species 
  of 
  Decadocrinus 
  and 
  Scytalocrinus. 
  The 
  two 
  

   genera 
  exhibit 
  variations 
  of 
  a 
  well 
  defined 
  arm 
  structure 
  of 
  two 
  

   to 
  the 
  ray, 
  unbranched; 
  and 
  while 
  typical 
  forms 
  of 
  the 
  two 
  are 
  

   readily 
  distinguished, 
  there 
  has 
  been 
  some 
  uncertainty 
  in 
  the 
  placing 
  

   of 
  certain 
  species. 
  As 
  a 
  general 
  rule 
  Decadocrinus 
  has 
  a 
  depressed 
  

   cup, 
  with 
  pentagonal 
  stem, 
  while 
  that 
  of 
  Scytalocrinus 
  is 
  more 
  or 
  

   less 
  elongate 
  and 
  turbinate, 
  with 
  rounded 
  stem. 
  But 
  as 
  to 
  these 
  

   there 
  are 
  exceptions; 
  and 
  the 
  most 
  reliable 
  character 
  in 
  practice 
  

   is 
  found 
  in 
  the 
  structure 
  of 
  the 
  pinnules, 
  those 
  of 
  Decadocrinus 
  

   being 
  large 
  and 
  well 
  separated, 
  resembling 
  ramules, 
  while 
  those 
  of 
  

   Scytalocrinus 
  are 
  closely 
  packed 
  like 
  regular 
  pinnules. 
  Both 
  show 
  

   good 
  examples 
  of 
  the 
  inflated 
  sac. 
  Those 
  of 
  the 
  specimens 
  which 
  

   I 
  figure 
  are 
  materially 
  different 
  in 
  form, 
  although 
  both 
  species 
  

   have 
  the 
  anal 
  opening 
  about 
  midway. 
  But 
  whether 
  this 
  difference 
  

   is 
  constant 
  is 
  not 
  known, 
  as 
  the 
  sac 
  is 
  too 
  rarely 
  found 
  exposed 
  to 
  

   furnish 
  a 
  general 
  rule. 
  In 
  both 
  genera 
  the 
  anterior 
  ray 
  occasionally 
  

   has 
  but 
  a 
  single 
  arm, 
  making 
  only 
  9 
  in 
  all 
  ; 
  and 
  in 
  both 
  there 
  may 
  

   be 
  either 
  one 
  or 
  two 
  primibrachs. 
  

  

  Genus 
  DECADOCRINUS 
  Wachsmuth 
  and 
  Springer 
  

  

  Decadocrinus 
  Wachsmuth 
  and 
  Springer, 
  Rev. 
  Pal., 
  pt. 
  1, 
  1879, 
  p. 
  119. 
  

   Devonian 
  to 
  Lower 
  Carboniferous. 
  

  

  DECADOCRINUS 
  HALLI 
  (Hall) 
  

  

  Plate 
  17, 
  figs. 
  4, 
  5. 
  

  

  Scaphiocrinus 
  halli 
  Hall, 
  Boston 
  Journ. 
  Nat. 
  Hist., 
  1861, 
  p. 
  308. 
  

   Decadocrinus 
  halli 
  Wachsmuth 
  and 
  Springer, 
  Rev. 
  Pal., 
  pt. 
  1, 
  p. 
  119. 
  

   Upper 
  Burlington 
  limestone; 
  Burlington, 
  Iowa. 
  

  

  An 
  excellent 
  example 
  of 
  the 
  delicate 
  Burlington 
  forms 
  of 
  the 
  

   genus. 
  It 
  only 
  differs 
  from 
  D. 
  scalaris, 
  5i 
  from 
  the 
  same 
  bed, 
  which 
  

   was 
  designated 
  by 
  Wachsmuth 
  and 
  Springer 
  55 
  as 
  type 
  of 
  the 
  genus, 
  

   by 
  having 
  a 
  single 
  primibrach 
  instead 
  of 
  two. 
  

  

  04 
  Meek 
  and 
  Worthen. 
  Geol. 
  Surv. 
  111., 
  vol. 
  5, 
  1S69, 
  p. 
  421, 
  pi. 
  2, 
  fig. 
  10. 
  

   SB 
  Rev. 
  Pal., 
  pt. 
  1, 
  p. 
  120. 
  

  

  