﻿24 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM 
  vol.67 
  

  

  the 
  same 
  position 
  as 
  the 
  cirri 
  in 
  Myelodactylus. 
  They 
  are 
  relatively 
  

   of 
  fair 
  length, 
  5 
  to 
  11 
  mm., 
  and 
  somewhat 
  irregular 
  in 
  shape, 
  al- 
  

   though 
  mostly 
  tapering 
  to 
  a 
  point. 
  Upon 
  the 
  most 
  careful 
  examina- 
  

   tion 
  I 
  am 
  unable 
  to 
  find 
  any 
  sign 
  of 
  articulation, 
  sutural 
  division 
  

   into 
  cirrals, 
  or 
  of 
  any 
  organic 
  structure; 
  yet 
  from 
  the 
  manner 
  in 
  

   which 
  they 
  overlap 
  toward 
  the 
  center, 
  these 
  appendages 
  must 
  have 
  

   had 
  a 
  certain 
  amount 
  of 
  flexibility, 
  to 
  adapt 
  themselves 
  to 
  the 
  move- 
  

   ments 
  of 
  the 
  segments 
  when 
  inrolling. 
  That 
  there 
  was 
  ample 
  facility 
  

   for 
  movement 
  of 
  this 
  kind 
  among 
  the 
  segments 
  is 
  clearly 
  shown 
  

   by 
  their 
  crenellated 
  edges 
  and 
  strong 
  beveling 
  at 
  the 
  back 
  in 
  the 
  

   two 
  principal 
  specimens, 
  and 
  by 
  the 
  presence 
  of 
  a 
  fulcral 
  ridge 
  and 
  

   fossae 
  for 
  muscles 
  and 
  ligaments 
  as 
  shown 
  in 
  the 
  isolated 
  ossicles. 
  

   The 
  axial 
  nerve 
  canal 
  by 
  which 
  they 
  are 
  perforated 
  extends 
  to 
  the 
  

   last 
  of 
  the 
  rapidly 
  narrowing 
  columnals, 
  which 
  are 
  preserved 
  in 
  one 
  

   specimen 
  almost 
  to 
  the 
  very 
  end, 
  and 
  is 
  also 
  seen 
  in 
  the 
  fragments. 
  

  

  It 
  does 
  not 
  seem 
  possible 
  that 
  articulations 
  and 
  intercirral 
  sutures 
  

   existing 
  in 
  life 
  could 
  have 
  been 
  completely 
  obliterated 
  in 
  these 
  fos- 
  

   sils, 
  which 
  are 
  unusually 
  perfect 
  and 
  well 
  preserved 
  ; 
  but 
  of 
  course 
  if 
  

   the 
  appendages 
  should 
  prove 
  to 
  be 
  jointed 
  structures 
  the 
  generic 
  posi- 
  

   tion 
  might 
  depend 
  upon 
  the 
  calyx, 
  as 
  there 
  would 
  be 
  no 
  essential 
  

   character 
  discoverable 
  to 
  separate 
  it 
  by 
  the 
  stem 
  alone 
  from 
  Myelo- 
  

   dactylus 
  or 
  from 
  Carnptocrinus. 
  

  

  As 
  to 
  the 
  crown, 
  which 
  has 
  been 
  partially 
  exposed 
  by 
  cutting 
  

   away 
  the 
  appendages 
  at 
  one 
  side, 
  I 
  am 
  unable 
  to 
  ascertain 
  the 
  de- 
  

   tails 
  of 
  its 
  construction. 
  The 
  calyx 
  is 
  strong 
  and 
  thick, 
  and 
  prob- 
  

   ably 
  belongs 
  to 
  the 
  Camerata 
  — 
  perhaps 
  to 
  some 
  form 
  of 
  the 
  Hexa- 
  

   crinidae, 
  which 
  take 
  on 
  many 
  strange 
  modifications. 
  There 
  is 
  a 
  

   suggestion 
  of 
  Arthracantha 
  in 
  the 
  remnants 
  of 
  calyx 
  and 
  arms 
  which 
  

   are 
  seen. 
  

  

  In 
  general 
  form 
  this 
  species 
  is 
  to 
  be 
  compared 
  with 
  Myelodactylus 
  

   ammonis, 
  which 
  has 
  a 
  similarly 
  short 
  coil, 
  wide, 
  and 
  narrowly 
  ter- 
  

   minated, 
  and 
  in 
  some 
  specimens 
  of 
  which 
  the 
  maximum 
  width 
  of 
  the 
  

   stem 
  is 
  equal 
  to 
  one-third 
  the 
  diameter 
  of 
  the 
  coil. 
  Both 
  were 
  un- 
  

   doubtedly 
  free, 
  this 
  one 
  completely 
  so, 
  as 
  it 
  is 
  hard 
  to 
  see 
  how 
  the 
  

   apparently 
  functionless 
  appendages 
  could 
  have 
  served 
  for 
  clinging 
  

   to 
  other 
  objects. 
  

  

  From 
  the 
  little 
  we 
  can 
  see 
  of 
  the 
  crown, 
  wdiich 
  bears 
  no 
  re- 
  

   semblance 
  to 
  that 
  of 
  the 
  Heterocrinidae, 
  there 
  seems 
  to 
  be 
  no 
  reason 
  

   to 
  regard 
  this 
  strangely 
  modified 
  form 
  as 
  the 
  end 
  of 
  the 
  Myelo- 
  

   dactylus 
  series. 
  My 
  guess 
  would 
  be 
  that 
  it 
  belongs 
  to 
  the 
  Camerata, 
  

   and 
  might 
  be 
  regarded 
  as 
  the 
  beginning 
  of 
  the 
  Gamptocrinus 
  series. 
  

   From 
  the 
  singular 
  way 
  in 
  which 
  the 
  Carboniferous 
  genus 
  Dichocrinus 
  

   adapts 
  itself 
  to 
  some 
  very 
  broad 
  modifications 
  in 
  the 
  structure 
  of 
  

   stem, 
  arms, 
  and 
  other 
  appendages, 
  it 
  might 
  reasonably 
  be 
  supposed 
  

  

  