﻿302 
  P. 
  H. 
  CAEPENTER 
  ON 
  THE 
  RELATIONS 
  OE 
  

  

  Eichwald 
  *, 
  who 
  expressed 
  himself, 
  however, 
  somewhat 
  less 
  strongly 
  

   than 
  before 
  respecting 
  the 
  identity 
  of 
  the 
  fossils 
  from 
  Erras 
  (Baero- 
  

   crinus) 
  and 
  Pulkowa 
  (Hybocrinus 
  dijoentas). 
  For 
  he 
  merely 
  says 
  

   " 
  if 
  they 
  are 
  identical, 
  as 
  I 
  believe 
  them 
  to 
  be," 
  and 
  not 
  " 
  they 
  are 
  

   absolutely 
  identical." 
  It 
  would 
  seem, 
  therefore, 
  that 
  the 
  further 
  

   knowledge 
  of 
  Baerocrinus 
  which 
  had 
  been 
  obtained 
  by 
  Grewingk, 
  

   had 
  raised 
  some 
  doubts 
  in 
  the 
  mind 
  of 
  Eichwald 
  as 
  to 
  the 
  tenability 
  

   of 
  his 
  former 
  position. 
  He 
  also 
  accepted 
  Grewingk's 
  diagram 
  of 
  the 
  

   composition 
  of 
  the 
  calyx 
  of 
  Hybocrinus 
  dipentas 
  (fig. 
  I. 
  b), 
  but 
  renamed 
  

   it 
  rather 
  oddly. 
  Eor 
  the 
  four 
  large 
  arm-bearing 
  plates 
  were 
  called 
  by 
  

   him 
  " 
  parabasals," 
  the 
  only 
  " 
  radial" 
  admitted 
  by 
  him 
  being 
  the 
  small 
  

   arm-bearing 
  plate 
  borne 
  on 
  the 
  right 
  upper 
  side 
  of 
  the 
  fifth 
  or 
  

   azygos 
  " 
  parabasal." 
  The 
  four 
  other 
  radials 
  were 
  supposed 
  by 
  him 
  

   to 
  have 
  fused 
  with 
  the 
  subjacent 
  parabasals, 
  although 
  no 
  traces 
  of 
  

   sutures 
  remain 
  to 
  indicate 
  their 
  existence. 
  Some 
  such 
  idea 
  as 
  this 
  

   was 
  necessary 
  in 
  order 
  to 
  be 
  able 
  to 
  regard 
  the 
  calyx 
  of 
  Apiocrinus 
  

   (Hybocrinus) 
  dijoentas 
  as 
  tricyclic, 
  so 
  as 
  to 
  permit 
  of 
  its 
  comparison 
  

   to 
  that 
  of 
  Homocrinus 
  ; 
  for 
  Eichwald 
  seems 
  to 
  have 
  given 
  up 
  the 
  

   views 
  which 
  he 
  had 
  previously 
  held 
  respecting 
  its 
  under-basals. 
  

   With 
  this 
  granted 
  he 
  could 
  of 
  course 
  assert 
  that 
  the 
  composition 
  of 
  

   the 
  calyx 
  in 
  Apiocrinus 
  dijoentas 
  was 
  the 
  same 
  as 
  that 
  of 
  Homocrinus 
  

   alternatus, 
  except 
  as 
  regards 
  the 
  presence 
  of 
  the 
  fifth 
  radial 
  and 
  the 
  

   azygos 
  plate. 
  

  

  But 
  remembering 
  the 
  differences 
  between 
  the 
  various 
  species 
  of 
  

   Homocrinus 
  t 
  ', 
  he 
  did 
  not 
  consider 
  the 
  characters 
  of 
  A. 
  dijoentas 
  

   sufficiently 
  marked 
  to 
  be 
  of 
  generic 
  value. 
  Eichwald's 
  expectation 
  

   that 
  specimens 
  of 
  A. 
  dipentas 
  would 
  be 
  found 
  with 
  the 
  arm-bearing 
  

   plates 
  distinct 
  from 
  the 
  so-called 
  parabasals, 
  is 
  hardly 
  likely 
  to 
  be 
  

   realized. 
  

  

  He 
  also 
  objected 
  to 
  Grewingk's 
  conception 
  of 
  Baerocrinus 
  as 
  

   3-armed, 
  after 
  his 
  own 
  description 
  of 
  it 
  as 
  5-armed, 
  on 
  account 
  of 
  

   this 
  being 
  " 
  entirely 
  contradictory 
  to 
  our 
  fundamental 
  conception 
  of 
  

   a 
  Crinoid." 
  And 
  he 
  further 
  stated 
  that 
  " 
  this 
  would 
  be 
  a 
  structure 
  

   unique 
  in 
  its 
  character, 
  which 
  is 
  the 
  less 
  likely 
  to 
  have 
  existed, 
  

   because 
  the 
  Erras 
  fossil 
  is 
  so 
  similar 
  to 
  that 
  from 
  Pulkowa 
  that 
  I 
  

   have 
  referred 
  them 
  both 
  to 
  one 
  and 
  the 
  same 
  type, 
  Homocrinus, 
  and 
  

   I 
  must 
  now 
  assume 
  that 
  both 
  the 
  radials 
  intervening 
  between 
  the 
  

   three 
  arm-bearing 
  ones 
  have 
  been 
  lost, 
  together 
  with 
  their 
  arms" 
  (III). 
  

   One 
  does 
  not 
  wonder, 
  after 
  reading 
  the 
  above 
  passages, 
  that 
  Vol- 
  

   borth 
  should 
  have 
  blamed 
  Eichwald 
  for 
  straining 
  his 
  facts 
  to 
  suit 
  

   his 
  theories. 
  It 
  is 
  surely 
  no 
  argument 
  against 
  the 
  3-armed 
  nature 
  

   of 
  Baerocrinus 
  for 
  Eichwald 
  to 
  say 
  that 
  he 
  believed 
  it 
  to 
  be 
  so 
  like 
  

   a 
  5-armed 
  type 
  that 
  he 
  described 
  the 
  two 
  as 
  identical. 
  Neither 
  can 
  

  

  * 
  " 
  Die 
  Lethsea 
  Eossica 
  unci 
  ihre 
  Gegner," 
  Moscow 
  Bulletin, 
  1867, 
  vol. 
  i. 
  

   pp. 
  191-199. 
  

  

  "t 
  According 
  to 
  Wachsmuth 
  and 
  Springer 
  ('Eevision,' 
  p. 
  77), 
  Hall's 
  generic 
  

   description 
  of 
  Homocrinus 
  "is 
  so 
  indefinite, 
  that 
  it 
  includes 
  almost 
  every 
  genus 
  

   of 
  the 
  Cyathocrinidai 
  ;" 
  and 
  H. 
  alternatus, 
  on 
  the 
  characters 
  of 
  which 
  Eichwald 
  

   laid 
  so 
  much 
  stress 
  from 
  its 
  supposed 
  resemblance 
  to 
  Apiocrinus 
  dijoentas, 
  is 
  

   really 
  a 
  Dendrocrinus. 
  

  

  