﻿INVERTEBRATE 
  S 
  . 
  359 
  

  

  top 
  is 
  highly 
  elevated, 
  standing 
  out 
  conspicuously 
  over 
  the 
  adjoin- 
  

   ing 
  parts. 
  Even 
  in 
  height 
  it 
  extends 
  beyond 
  the 
  limits 
  of 
  the 
  other 
  

   parts 
  of 
  the 
  body. 
  

  

  Anal 
  aperture 
  large, 
  oval 
  in 
  form, 
  horizontal 
  in 
  position. 
  Toward 
  

   the 
  outer 
  side 
  the 
  opening 
  is 
  formed 
  by 
  the 
  wall 
  of 
  the 
  anal 
  plate, 
  

   which 
  at 
  the 
  upper 
  end 
  is 
  bulging 
  outward 
  without 
  being 
  excavated. 
  

   The 
  lateral 
  sides 
  of 
  the 
  aperture 
  are 
  formed 
  by 
  the 
  upper 
  curved 
  

   ends 
  of 
  the 
  oral 
  side-plates, 
  which 
  are 
  connected 
  by 
  two 
  or 
  three 
  

   small 
  anal 
  vault 
  pieces, 
  and 
  these 
  constitute 
  the 
  upper 
  boundary 
  of 
  

   the 
  aperture. 
  

  

  Ambulacra 
  long, 
  narrow, 
  linear, 
  raised 
  above 
  the 
  general 
  level 
  of 
  

   the 
  body, 
  except 
  close 
  to 
  the 
  oral 
  pole, 
  near 
  which 
  they 
  curve 
  

   abruply 
  toward 
  the 
  oral 
  opening, 
  and 
  the 
  ambulacrum 
  becomes 
  lo- 
  

   cated 
  below 
  the 
  abutting 
  surface. 
  The 
  lancet-piece 
  is 
  deeply 
  grooved 
  

   along 
  the 
  median 
  line, 
  and 
  when 
  the 
  side-pieces 
  (pore-pieces 
  of 
  

   Roemer) 
  are 
  not 
  in 
  place, 
  there 
  is 
  at 
  the 
  suture, 
  along 
  each 
  side 
  of 
  

   the 
  plate, 
  a 
  deep 
  sulcus, 
  penetrated 
  by 
  the 
  hydrospire-pores. 
  This 
  

   sulcus, 
  however, 
  when 
  the 
  side-pieces 
  are 
  in 
  situ 
  is 
  totally 
  filled, 
  

   and 
  the 
  sides 
  of 
  the 
  ambulacrum 
  rise 
  abruptly 
  above 
  the 
  abutting 
  

   edges. 
  The 
  side-pieces 
  rest 
  against 
  the 
  upper 
  face 
  of 
  the 
  deeply 
  

   crenulated 
  ridges 
  of 
  the 
  lancet-piece. 
  They 
  are 
  strongly 
  wedge- 
  

   shaped 
  and 
  placed 
  obliquely 
  to 
  the 
  ambulacral 
  or 
  food-groove, 
  with 
  

   the 
  smaller 
  angle 
  directed 
  to 
  the 
  ab-oral 
  side. 
  Their 
  number 
  is 
  from 
  

   about 
  sixty 
  to 
  nearly 
  ninety 
  in 
  very 
  large 
  specimens. 
  The 
  outer 
  

   side-pieces 
  (supplementary 
  pore-pieces 
  of 
  Roemer) 
  are 
  comparatively 
  

   large, 
  their 
  longer 
  side 
  being 
  about 
  two-thirds, 
  their 
  shorter 
  sides 
  

   fully 
  one-half 
  of 
  the 
  corresponding 
  sides 
  in 
  the 
  pore-pieces. 
  

  

  The 
  summit 
  is 
  a 
  flat 
  disc, 
  somewhat 
  depressed 
  in 
  the 
  middle, 
  

   sub-pentangular 
  in 
  outline, 
  the 
  angles 
  resting 
  against 
  the 
  slightly 
  

   truncated 
  upper 
  part 
  of 
  the 
  oral 
  plates, 
  leaving 
  in 
  the 
  direction 
  of 
  

   each 
  ambulacrum 
  a 
  good 
  sized 
  passage. 
  The 
  central 
  aperture 
  is 
  

   pentangular, 
  rather 
  deeply 
  depressed. 
  

  

  Spiracles 
  ten, 
  one 
  to 
  each 
  side 
  of 
  the 
  ambulacrum, 
  those 
  of 
  the 
  

   posterior 
  side 
  not 
  in 
  contact 
  with 
  the 
  anal 
  aperture. 
  They 
  are 
  in 
  

   this 
  species 
  not 
  easily 
  detected, 
  being 
  placed 
  laterally 
  within 
  the 
  

   projecting 
  edges 
  of 
  the 
  orals, 
  which 
  for 
  their 
  reception 
  are 
  at 
  this 
  

   place 
  more 
  prominent, 
  and 
  somewhat 
  excavated. 
  The 
  hydrospires 
  

   are 
  arranged 
  in 
  ten 
  groups, 
  with 
  two 
  in 
  each 
  group 
  ; 
  they 
  are 
  in 
  

   form 
  similar 
  to 
  those 
  of 
  Granatocrinus 
  Norwoodi, 
  but 
  comparatively 
  

   a 
  little 
  larger. 
  Hydrospire-pores 
  small, 
  and 
  more 
  or 
  less 
  hidden. 
  

  

  