﻿40 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM 
  vol.07 
  

  

  calyx, 
  and 
  probably 
  the 
  arms, 
  which 
  are 
  broken 
  off. 
  While 
  there 
  is 
  

   no 
  trace 
  either 
  of 
  coiling 
  or 
  bilateralism, 
  yet 
  the 
  peculiar 
  behavior 
  

   of 
  the 
  cirri 
  in 
  this 
  specimen 
  should 
  be 
  considered 
  in 
  connection 
  with 
  

   what 
  was 
  later 
  developed 
  under 
  Camptocrinus. 
  

  

  Wachsiinuth 
  and 
  Springer 
  at 
  the 
  same 
  time 
  described 
  from 
  the 
  

   Warsaw 
  group 
  another 
  species, 
  Dicliocrinus 
  oblongus 
  20 
  , 
  founded 
  

   upon 
  a 
  unique 
  specimen 
  having 
  only 
  the 
  calyx 
  preserved. 
  Speci- 
  

   mens 
  subsequently 
  obtained 
  with 
  the 
  arms 
  attached 
  show 
  that 
  these 
  

   are 
  of 
  the 
  recumbent 
  variety, 
  and 
  I 
  am 
  accordingly 
  illustrating 
  the 
  

   species 
  anew 
  (pi. 
  11, 
  figs. 
  5, 
  6). 
  

  

  In 
  these 
  two 
  species, 
  however, 
  as 
  I 
  see 
  them 
  now, 
  there 
  does 
  not 
  

   seem 
  to 
  be 
  quite 
  the 
  same 
  structural 
  type, 
  or 
  mode 
  of 
  attachment 
  

   of 
  the 
  arms, 
  that 
  we 
  have 
  in 
  the 
  preceding 
  examples. 
  The 
  arms 
  

   are 
  not 
  so 
  compactly 
  placed, 
  nor 
  connected 
  in 
  the 
  tegmen 
  by 
  their 
  

   covering 
  plates, 
  and 
  their 
  appearance 
  seems 
  more 
  like 
  that 
  of 
  ordi- 
  

   nary 
  bending 
  backward 
  as 
  the 
  result 
  of 
  great 
  flexibility. 
  

  

  Genus 
  ACROCRINUS 
  Yandell 
  

  

  Plates 
  9, 
  12, 
  and 
  18 
  

  

  Acrocrinus 
  Yandell, 
  Amer. 
  Journ. 
  Sci. 
  and 
  Arts, 
  vol. 
  20, 
  1855, 
  p. 
  135. 
  — 
  

   Wachsmuth 
  and 
  Spbingeb, 
  North 
  Amer. 
  Crin. 
  Cam., 
  1897, 
  p. 
  805. 
  — 
  

   Bather, 
  Lankester 
  Zoology, 
  pt. 
  3, 
  1900, 
  p. 
  159. 
  

  

  Carboniferous, 
  Burlington 
  to 
  Pennsylvanian. 
  

  

  Of 
  a 
  very 
  different 
  character 
  from 
  those 
  last 
  mentioned 
  are 
  the 
  

   arms 
  of 
  Acroc?*i?ius, 
  the 
  last 
  successor 
  in 
  the 
  family 
  Hexacrinidae, 
  

   which 
  is 
  thoroughly 
  illustrated 
  in 
  the 
  Camerata 
  monograph 
  (pi. 
  80). 
  

   In 
  this 
  form 
  we 
  have 
  in 
  one 
  species 
  a 
  perfect 
  example 
  of 
  the 
  re- 
  

   cumbent 
  arm 
  structure 
  as 
  I 
  have 
  described 
  it, 
  in 
  which 
  not 
  only 
  

   are 
  the 
  arms 
  compactly 
  placed, 
  in 
  close 
  contact, 
  connected 
  in 
  the 
  

   tegmen 
  so 
  as 
  to 
  restrict 
  motion, 
  directed 
  downward 
  from 
  the 
  edge 
  

   of 
  the 
  tegmen 
  and 
  closing 
  around 
  the 
  stem, 
  but 
  the 
  calyx 
  is 
  marked 
  

   by 
  numerous 
  longitudinal 
  impressions 
  following 
  the 
  course 
  of 
  the 
  

   arms 
  and 
  formed 
  by 
  the 
  continued 
  pressure 
  of 
  the 
  arms 
  from 
  their 
  

   dorsal 
  side. 
  I 
  think 
  there 
  is 
  no 
  doubt 
  that 
  they 
  grew 
  in 
  that 
  way, 
  

   and 
  that 
  the 
  mode 
  of 
  life 
  of 
  this 
  species 
  was 
  to 
  have 
  the 
  arms 
  com- 
  

   pletely 
  recurved 
  with 
  the 
  pinnules 
  on 
  the 
  outside. 
  

  

  The 
  species 
  in 
  which 
  the 
  recumbent 
  arm 
  occurs, 
  Acrocrinus 
  am- 
  

   phora 
  Wachsmuth 
  and 
  Springer, 
  came 
  from 
  a 
  single 
  colony 
  at 
  

   Huntsville, 
  Alabama, 
  in 
  the 
  Ohara 
  formation 
  of 
  the 
  lower 
  Chester 
  

   (formerly 
  referred 
  to 
  the 
  St. 
  Louis), 
  in 
  which 
  it 
  was 
  fairly 
  abun- 
  

   dant. 
  Upwards 
  of 
  sixty 
  specimens 
  were 
  collected 
  by 
  Wachsmuth, 
  

   and 
  with 
  one 
  or 
  two 
  imperfect 
  exceptions 
  the 
  structure 
  as 
  above 
  set 
  

  

  20 
  North 
  Amer. 
  Crin. 
  Cam., 
  p. 
  759, 
  pi. 
  78, 
  fig. 
  9. 
  

  

  