﻿INVERTEBRATES. 
  349 
  

  

  If 
  it 
  were 
  true, 
  as 
  Meek 
  and 
  Worthen 
  asserted, 
  that 
  in 
  "Codon- 
  

   ites" 
  the 
  five 
  or 
  six 
  upper 
  joints 
  became 
  anchylosed 
  in 
  more 
  adult 
  

   specimens, 
  and 
  were 
  transformed 
  into 
  solid 
  plates, 
  it 
  is 
  very 
  singu- 
  

   lar 
  that 
  no 
  transition 
  forms 
  have 
  ever 
  been 
  found 
  in 
  this 
  or 
  any 
  

   other 
  allied 
  species. 
  I 
  think 
  a 
  metamorphosis 
  like 
  this 
  would 
  have 
  

   undoubtedly 
  left 
  traces 
  of 
  the 
  columnar 
  joints 
  in 
  the 
  growing 
  

   animal, 
  especially 
  since 
  the 
  modification, 
  as 
  we 
  may 
  safely 
  suggest, 
  

   must 
  have 
  taken 
  place 
  gradually, 
  and 
  joint 
  by 
  joint; 
  but 
  although 
  

   I 
  have 
  examined 
  more 
  than 
  fifty 
  specimens 
  of 
  this 
  species, 
  I 
  could 
  

   not 
  find 
  the 
  remotest 
  traces 
  of 
  former 
  stem 
  joints, 
  or 
  of 
  a 
  suture; 
  

   all 
  that 
  I 
  have 
  been 
  able 
  to 
  discover 
  is 
  a 
  slight 
  angular 
  depression 
  

   around 
  the 
  lower 
  end 
  of 
  the 
  cup. 
  This 
  depression, 
  which 
  has 
  some- 
  

   what 
  the 
  appearance 
  of 
  a 
  suture, 
  is 
  caused 
  simply 
  by 
  the 
  more 
  rapid 
  

   spreading 
  of 
  the 
  upper 
  portions 
  of 
  the 
  basals. 
  Such 
  at 
  least 
  is 
  the 
  

   ease 
  in 
  some 
  species 
  of 
  Codonites, 
  Codaster 
  and 
  Troostocrinus, 
  in 
  

   which 
  the 
  base 
  appears 
  as 
  if 
  it 
  might 
  be 
  bicyclic, 
  but 
  actually 
  is 
  

   monocyclic, 
  and 
  in 
  which 
  the 
  lower 
  part 
  is 
  almost 
  cylindrical, 
  and 
  

   resembles 
  an 
  elongate 
  columnar 
  joint, 
  while 
  the 
  upper 
  part 
  is 
  

   conical. 
  

  

  It 
  seems 
  to 
  me 
  that 
  this 
  upward 
  spreading 
  of 
  the 
  basals 
  can 
  be 
  

   naturally 
  explained 
  by 
  the 
  growth 
  of 
  the 
  animal. 
  The 
  form 
  gener- 
  

   ally 
  throughout 
  the 
  Blastoids 
  is 
  in 
  a 
  young 
  specimen 
  more 
  elongate 
  

   than 
  in 
  the 
  adult, 
  and 
  after 
  attaining 
  a 
  certain 
  growth, 
  the 
  calyx 
  

   increases 
  in 
  height 
  comparatively 
  little, 
  while 
  the 
  ambulacra 
  still 
  

   grow 
  considerably 
  longer. 
  This 
  disproportion 
  in 
  the 
  growth 
  of 
  the 
  

   different 
  parts 
  is 
  equalized 
  by 
  the 
  increase 
  of 
  the 
  body 
  in 
  width, 
  by 
  

   which 
  the 
  ambulacra 
  attain 
  a 
  greater 
  curvature, 
  pushing 
  the 
  basals 
  

   and 
  partly 
  the 
  radials, 
  from 
  a 
  fairly 
  sloping 
  position 
  to 
  a 
  more 
  

   horizontal 
  one, 
  as 
  shown 
  in 
  the 
  following 
  species, 
  of 
  wbich 
  I 
  have 
  

   examined 
  a 
  large 
  number 
  of 
  specimens 
  in 
  all 
  stages 
  of 
  growth. 
  

  

  In 
  the 
  young 
  Orophocrinus 
  stelliformis, 
  the 
  ambulacra 
  occupy 
  only 
  

   the 
  upper 
  truncate 
  side 
  of 
  the 
  body, 
  the 
  lower 
  portions 
  are 
  turbinate 
  

   with 
  nearly 
  straight 
  sides 
  ; 
  in 
  very 
  old 
  specimens, 
  however, 
  the 
  am- 
  

   bulacra 
  curves 
  so 
  strongly, 
  and 
  reach 
  down 
  so 
  deeply, 
  that 
  the 
  radial 
  

   lips 
  were 
  brought 
  into 
  a 
  horizontal 
  position, 
  almost 
  to 
  the 
  level 
  of 
  

   the 
  basals, 
  and 
  the 
  sides 
  of 
  the 
  body 
  became 
  concave, 
  thereby 
  push- 
  

   ing 
  the 
  upper 
  portions 
  of 
  the 
  radials 
  in 
  a 
  more 
  outward 
  direction. 
  

  

  Schizoblastus 
  (Granatocrinus) 
  melo 
  0. 
  & 
  Shum. 
  is, 
  in 
  its 
  younger 
  

   stages, 
  elongate-ovate, 
  in 
  medium 
  sized 
  specimens 
  subglobose 
  to 
  glo- 
  

   bose, 
  and 
  in 
  large 
  specimens 
  depressed 
  globose. 
  The 
  same 
  modifi- 
  

  

  