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  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM 
  

  

  vol. 
  07 
  

  

  Thus 
  we 
  find 
  the 
  same 
  relative 
  excess 
  in 
  width 
  of 
  the 
  lateral 
  

   radials 
  over 
  the 
  posterior 
  radials. 
  Hence 
  the 
  inequality 
  of 
  radials 
  

   shown 
  to 
  exist 
  in 
  the 
  specimens 
  generally 
  is 
  now 
  found 
  to 
  be 
  a. 
  

   character 
  in 
  the 
  types 
  of 
  those 
  species 
  which 
  have 
  been 
  considered 
  

   typical 
  of 
  Agasskocrinus, 
  including 
  the 
  genotype 
  itself. 
  Although, 
  

   in 
  these 
  two 
  specimens 
  the 
  anterior 
  radial 
  is 
  also 
  more 
  or 
  less 
  en- 
  

   larged, 
  as 
  in 
  some 
  others 
  before 
  mentioned, 
  it 
  does 
  not 
  follow 
  that 
  

   the 
  same 
  inequality 
  of 
  arms 
  extends 
  to 
  that 
  ray. 
  For 
  in 
  the 
  A. 
  

   laevis 
  type 
  I 
  was 
  able, 
  by 
  additional 
  preparation, 
  to 
  expose 
  the 
  

   distal 
  faces 
  of 
  the 
  axillary 
  primibrachs 
  all 
  around, 
  with 
  the 
  interest- 
  

   ing 
  result 
  that 
  while 
  in 
  the 
  anterolateral 
  rays 
  the 
  faces 
  of 
  the 
  

   axillary 
  are 
  6 
  and 
  4 
  mm. 
  respectively, 
  in 
  the 
  anterior 
  ray 
  the 
  faces 
  

   are 
  equal 
  at 
  5 
  mm. 
  — 
  those 
  in 
  the 
  posterior 
  rays 
  being 
  4.5 
  mm.; 
  so 
  

   that 
  while 
  in 
  some 
  specimens 
  the 
  anterior 
  arms 
  may 
  be 
  a 
  little 
  

   larger 
  than 
  the 
  posterior, 
  there 
  is 
  probably 
  no 
  such 
  hypertrophy 
  or 
  

   inequality 
  as 
  exists 
  in 
  the 
  latter 
  in 
  Whitfield's 
  species. 
  Not 
  only 
  so, 
  

   but 
  this 
  specimen 
  as 
  now 
  prepared 
  affords 
  a 
  comparative 
  view 
  of 
  the 
  

   posterior 
  arms 
  and 
  the 
  antero-lateral 
  arm 
  next 
  to 
  them, 
  by 
  which 
  

   the 
  greater 
  size 
  of 
  the 
  latter 
  can 
  be 
  plainly 
  seen 
  (pi. 
  15, 
  fig. 
  5a). 
  

  

  By 
  way 
  of 
  a 
  check 
  upon 
  these 
  observations, 
  and 
  in 
  order 
  to 
  see- 
  

   whether 
  analogous 
  differences 
  might 
  not 
  exist 
  among 
  the 
  rays 
  of 
  

   other 
  closely 
  related 
  genera, 
  I 
  tabulated 
  the 
  widths 
  of 
  the 
  radial 
  1 
  

   facets 
  in 
  26 
  specimens 
  from 
  the 
  same 
  formations 
  and 
  localities, 
  be- 
  

   longing 
  to 
  three 
  species 
  of 
  Eupachycrmus, 
  which 
  has 
  the 
  anal 
  side 
  

   identical 
  with 
  that 
  of 
  Agassisocrinus, 
  with 
  the 
  result 
  that 
  the 
  mean 
  

   width 
  of 
  the 
  five 
  radials 
  differs 
  not 
  exceeding 
  0.5 
  mm. 
  between 
  any 
  

   two 
  of 
  them, 
  and 
  not. 
  according 
  to 
  any 
  definite 
  plan. 
  The 
  composite 
  

   of 
  the 
  26 
  is 
  as 
  follows 
  : 
  

  

  The 
  obvious 
  conclusion 
  from 
  these 
  facts 
  is 
  that 
  the 
  anomalous 
  arm 
  

   structure 
  exhibited 
  in 
  Whitfield's 
  species 
  pertains 
  more 
  or 
  less 
  to 
  the 
  

   species 
  of 
  Agassisocrinus 
  generally, 
  and 
  that 
  the 
  dominant 
  character 
  

   of 
  the 
  latter 
  genus 
  is 
  not 
  the 
  absence 
  of 
  a 
  stem 
  but 
  the 
  hypertrophy 
  

   of 
  certain 
  arms 
  in 
  two 
  (perhaps 
  occasionally 
  three) 
  of 
  the 
  rays, 
  pro- 
  

   ducing 
  an 
  asymmetry 
  within 
  the 
  ray 
  itself 
  5 
  that 
  the 
  fusion 
  of 
  infra- 
  

   basals 
  is 
  not 
  entirely 
  a 
  matter 
  of 
  adult 
  growth 
  (although 
  the 
  elimina- 
  

   tion 
  of 
  the 
  stem 
  is 
  undoubtedly 
  an 
  adult 
  character 
  in 
  the 
  ontogeny 
  of 
  

   the 
  crinoids) 
  but 
  that 
  the 
  instability 
  of 
  the 
  base 
  follows 
  a 
  tendency 
  

   to 
  change 
  directly 
  associated 
  with 
  the 
  abnormal 
  modification 
  of 
  the 
  

   arms. 
  It 
  may 
  thus 
  be 
  a 
  character 
  which 
  became 
  fixed 
  in 
  certain 
  

   species, 
  or 
  it 
  may 
  have 
  occurred 
  sporadically 
  or 
  at 
  different 
  stages 
  of 
  

  

  