﻿58 
  

  

  PROCEEDINGS 
  OF 
  THE 
  NATIONAL, 
  MUSEUM 
  

  

  vol. 
  67 
  

  

  species 
  as 
  defined 
  was 
  the 
  inequality 
  of 
  the 
  arms, 
  the 
  structure 
  of 
  

   which 
  was 
  described 
  as 
  follows 
  : 
  

  

  Second 
  radials, 
  or 
  first 
  arm 
  plates, 
  smaller 
  than 
  the 
  first 
  radials 
  and 
  nar- 
  

   rowing 
  upward 
  ; 
  wedge 
  formed 
  above, 
  and 
  each 
  supporting 
  two 
  arms. 
  On 
  the 
  

   postero-lateral, 
  with 
  the 
  arms 
  slender. 
  On 
  the 
  anterior 
  ray 
  it 
  is 
  short 
  and 
  

   supports 
  two 
  slender 
  arms 
  ; 
  while 
  on 
  the 
  antero-lateral 
  rays 
  they 
  support 
  a 
  

   slender 
  arm 
  similar 
  to 
  those 
  of 
  the 
  other 
  rays 
  on 
  the 
  anterior 
  side, 
  and 
  on 
  

   the 
  outer 
  side 
  an 
  arm 
  several 
  times 
  larger 
  and 
  stronger 
  than 
  the 
  others, 
  and 
  

   composed 
  of 
  longer 
  and 
  stronger 
  plates. 
  

  

  That 
  is 
  to 
  say, 
  there 
  are 
  10 
  arms, 
  but 
  those 
  on 
  the 
  axillary 
  faces 
  

   of 
  the 
  antero-lateral 
  primibrachs 
  are 
  unequal, 
  the 
  branch 
  on 
  each 
  

   outer 
  face 
  (toward 
  the 
  posterior 
  side) 
  being 
  hypertrophied, 
  thus 
  

   giving 
  two 
  disproportionately 
  large 
  arms, 
  and 
  eight, 
  much 
  smaller, 
  

   about 
  equal 
  among 
  themselves. 
  

  

  In 
  one 
  of 
  the 
  specimens 
  the 
  strong 
  antero-lateral 
  arm 
  is 
  preserved 
  

   to 
  more 
  than 
  an 
  inch. 
  In 
  all 
  three 
  the 
  infrabasals 
  are 
  distinctly 
  

   divided, 
  forming 
  a 
  rather 
  low 
  conical 
  cup, 
  to 
  which 
  a 
  well 
  developed 
  

   stem 
  is 
  attached. 
  

  

  Now 
  the 
  radial 
  facets 
  occupy 
  the 
  full 
  width 
  of 
  the 
  radials, 
  and 
  

   are 
  equipped 
  with 
  a 
  complete 
  muscular 
  articulation, 
  while 
  the 
  anal 
  

   side 
  is 
  that 
  of 
  the 
  later 
  Poteriocrinidae 
  ; 
  so 
  it 
  was 
  long 
  ago 
  evident 
  

   that 
  this 
  species 
  does 
  not 
  belong 
  to 
  the 
  genus 
  Cyathocrinus. 
  Casting 
  

   about 
  to 
  find 
  a 
  place 
  for 
  it, 
  having 
  meantime 
  acquired 
  an 
  excellent 
  

   specimen 
  clearly 
  belonging 
  to 
  the 
  species, 
  I 
  was 
  struck 
  with 
  the 
  re- 
  

   semblance 
  of 
  the 
  calyx 
  in 
  all 
  essential 
  characters 
  to 
  that 
  of 
  those 
  

   species 
  of 
  Agassizocrinus 
  having 
  divided 
  infrabasals 
  and 
  a 
  column 
  

   facet. 
  Upon 
  reviewing 
  my 
  material 
  which 
  has 
  been 
  referred 
  to 
  

   that 
  genus, 
  I 
  found 
  two 
  specimens 
  with 
  the 
  arms 
  transversely 
  frac- 
  

   tured 
  which 
  plainly 
  disclosed 
  in 
  cross 
  section 
  the 
  two 
  hypertrophied 
  

   arms, 
  precisely 
  as 
  in 
  Whitfield's 
  specimens. 
  In 
  both 
  of 
  these 
  also 
  

   the 
  infrabasals 
  are 
  divided, 
  and 
  a 
  distinct 
  column 
  facet 
  is 
  present. 
  

  

  Upon 
  making 
  careful 
  measurements 
  I 
  found 
  that 
  the 
  difference 
  in 
  

   the 
  size 
  of 
  arms 
  was 
  reflected 
  in 
  the 
  width 
  of 
  the 
  radials 
  at 
  the 
  dis- 
  

   tal 
  facet, 
  which 
  was 
  nearly 
  the 
  same 
  in 
  the 
  two 
  specimens, 
  the 
  mean 
  

   of 
  the 
  two, 
  in 
  millimeters, 
  being 
  : 
  

  

  This 
  suggested 
  the 
  probability 
  that 
  similar 
  measurements 
  might 
  

   furnish 
  a 
  clue 
  to 
  the 
  existence 
  of 
  unequal 
  arms 
  in 
  specimens 
  in 
  which 
  

   only 
  the 
  calyx 
  was 
  intact. 
  I 
  thereupon 
  assembled 
  all 
  such 
  speci- 
  

   mens 
  supposed 
  to 
  belong 
  to 
  Agassisoei'imts, 
  from 
  five 
  of 
  the 
  princi- 
  

   pal 
  regions, 
  and 
  tabulated 
  the 
  data 
  for 
  the 
  width 
  of 
  the 
  radial 
  facets, 
  

   measured 
  at 
  the 
  outside 
  in 
  15 
  of 
  these, 
  of 
  which 
  6 
  have 
  the 
  infrabas- 
  

  

  