﻿300 
  P. 
  H. 
  CAEPEX'IEK 
  ON 
  THE 
  RELATIONS 
  OF 
  

  

  times 
  fuse 
  with 
  one 
  another, 
  and 
  do 
  not 
  everywhere 
  show 
  the 
  

   sutures 
  quite 
  so 
  clearly 
  as 
  is 
  represented 
  in 
  Hall's 
  ideal 
  diagram." 
  

   In 
  this 
  point, 
  however, 
  lies 
  the 
  chief 
  difference 
  between 
  the 
  two 
  

   types. 
  The 
  sutures 
  are 
  not 
  visible 
  in 
  the 
  Erras 
  specimen 
  (Baero- 
  

   crinus), 
  because 
  they 
  are 
  not 
  there 
  (fig. 
  I. 
  e 
  ; 
  PI. 
  XI. 
  fig. 
  1) 
  ; 
  and 
  

   Eichwald 
  was 
  driven 
  to 
  assume 
  a 
  fusion 
  between 
  the 
  basals 
  and 
  

   supposed 
  under-basals 
  in 
  order 
  to 
  support 
  his 
  theory 
  of 
  its 
  being 
  a 
  

   Homocrinus. 
  But 
  in 
  Apiocrinus 
  dipentas 
  he 
  believed 
  himself 
  able 
  

   to 
  discern 
  not 
  only 
  a 
  suture 
  between 
  basals 
  and 
  under-basals, 
  but 
  

   also 
  sutures 
  between 
  the 
  under-basals 
  themselves, 
  which 
  in 
  his 
  

   view 
  are 
  in 
  the 
  same 
  line 
  with 
  the 
  basals, 
  and 
  not 
  alternating 
  with 
  

   them 
  : 
  and 
  he 
  made 
  the 
  curious 
  mistake 
  of 
  saying 
  that 
  this 
  is 
  quite 
  

   the 
  same 
  arrangement 
  as 
  in 
  Encrinus 
  liliiformis 
  from 
  the 
  Muschel- 
  

   kalk, 
  although, 
  as 
  is 
  well 
  known, 
  exactly 
  the 
  reverse 
  is 
  the 
  case. 
  

  

  The 
  so-called 
  Yolborth's 
  organ 
  was 
  regarded 
  by 
  Eichwald 
  as 
  due 
  

   to 
  fracture 
  — 
  a 
  view 
  which, 
  with 
  more 
  or 
  less 
  modification, 
  has 
  been 
  

   adopted 
  by 
  later 
  writers 
  ; 
  but 
  his 
  attempt 
  to 
  discover 
  in 
  the 
  Eussian 
  

   specimens 
  the 
  interradial 
  plates 
  of 
  Homocrinus 
  has 
  hardly 
  met 
  with 
  

   such 
  general 
  acceptance. 
  Neither 
  was 
  his 
  refutation 
  of 
  Yolborth's 
  

   identification 
  of 
  Apiocrinus 
  dipentas 
  as 
  a 
  Hyboerinus 
  at 
  all 
  well 
  

   grounded 
  ; 
  for 
  it 
  depended 
  on 
  the 
  following 
  reasoning. 
  — 
  Two 
  radials 
  

   arc 
  visible 
  on 
  one 
  side 
  of 
  the 
  Erras 
  fossil 
  (Baerocrinus). 
  The 
  oppo- 
  

   site 
  * 
  side 
  of 
  the 
  Pulkowa 
  specimens 
  shows 
  three 
  radials 
  in 
  a 
  

   continuous 
  series. 
  Hence 
  there 
  was 
  an 
  unbroken 
  series 
  of 
  five 
  

   radials 
  in 
  Apiocrinus 
  dipentas, 
  which 
  therefore 
  could 
  not 
  be 
  a 
  

   Hyboerinus. 
  The 
  weak 
  point 
  in 
  this 
  argument 
  is 
  the 
  assumption 
  of 
  

   the 
  specific 
  identity 
  of 
  the 
  Erras 
  and 
  Pulkowa 
  specimens, 
  which, 
  

   like 
  Yolborth 
  and 
  Grewingk 
  f, 
  I 
  am 
  strongly 
  inclined 
  to 
  doubt 
  ; 
  

   although 
  Schmidt 
  ±, 
  the 
  latest 
  writer 
  on 
  the 
  subject, 
  adopts 
  Eich- 
  

   wald's 
  view 
  as 
  regards 
  this 
  point. 
  He 
  refers 
  both 
  fossils 
  to 
  Hybo- 
  

   erinus 
  dipentas, 
  however, 
  and 
  gives 
  diagrams 
  of 
  other 
  examples 
  of 
  

   the 
  species 
  (fig. 
  I. 
  c, 
  d), 
  which 
  have 
  any 
  thing 
  but 
  the 
  continuous 
  

   series 
  of 
  five 
  radials 
  that 
  was 
  assumed 
  to 
  exist 
  by 
  Eichwald 
  after 
  

   his 
  examination 
  of 
  "opposite"' 
  sides 
  of 
  two 
  very 
  dissimilar 
  speci- 
  

   mens. 
  ' 
  

  

  Eichwald's 
  defence 
  of 
  Homocrinus 
  was 
  severely 
  criticised 
  by 
  Yol- 
  

   borth^ 
  who 
  stated 
  that 
  he 
  had 
  examined 
  over 
  twenty 
  calyces 
  of 
  

   Hyboerinus 
  dipentas 
  without 
  finding 
  any 
  traces 
  of 
  the 
  under-basals 
  

   described 
  by 
  Eichwald 
  in 
  a 
  young 
  but 
  worn 
  specimen 
  ; 
  while 
  he 
  

   also 
  pointed 
  out 
  Eichwald's 
  mistake 
  in 
  localizing 
  the 
  under-basals 
  

   of 
  Encrinus 
  as 
  parallel 
  to 
  the 
  basals, 
  and 
  that, 
  if 
  Eichwald's 
  descrip- 
  

   tion 
  of 
  it 
  were 
  correct, 
  Apiocrinus 
  dipentas 
  would 
  represent 
  a 
  new 
  

   type 
  of 
  Crinoids 
  altogether 
  and 
  not 
  belong 
  to 
  Homocrinus 
  at 
  all. 
  

  

  * 
  How 
  determined 
  as 
  opposite 
  ? 
  

  

  t 
  " 
  Ueber 
  Hoplocrinv.s 
  dipentas 
  und 
  Baerocrinus 
  Ungerni," 
  Archiv 
  fur 
  die 
  

   Naturkunde 
  Liv- 
  Ebst- 
  und 
  Kurlands, 
  series 
  1, 
  Bd. 
  iv. 
  p. 
  110. 
  

  

  | 
  " 
  Ueber 
  einige 
  neue 
  und 
  wenig 
  bekannte 
  Baltisck-silurisclie 
  Petrefacten," 
  

   Mem. 
  St. 
  Petersb. 
  Acad. 
  torn. 
  xxi. 
  no. 
  11, 
  p. 
  5. 
  

  

  § 
  " 
  Die 
  angeblicbe 
  Homocrinen 
  der 
  Lethsea 
  Rossica 
  ." 
  Moscow 
  Bulletin, 
  1866, 
  

   part 
  iv. 
  pp. 
  541-550. 
  

  

  