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  EXPLANATION 
  OP 
  THE 
  PLATES. 
  

  

  Fig. 
  B. 
  Pectinura 
  iufernalis, 
  showing 
  the 
  disk 
  and 
  the 
  variations 
  of 
  

   the 
  " 
  naked 
  plates," 
  x 
  3. 
  

   C. 
  OiMopinax 
  stellatus, 
  showing 
  the 
  arrangement 
  of 
  the 
  radial 
  

   and 
  interradial 
  plates 
  on 
  the 
  disk, 
  x 
  2. 
  

  

  Plate 
  IX. 
  

  

  Pig. 
  A. 
  Cucumaria 
  semperi. 
  

  

  B. 
  ColocMrus 
  tuberculosus. 
  Spicules 
  seen 
  from 
  the 
  side 
  and 
  

  

  from 
  below. 
  

  

  C. 
  Actinocucumis 
  difftcilis. 
  

  

  D. 
  Tliyone 
  oheni. 
  Calcareous 
  ring 
  and 
  oesophagus. 
  

  

  E. 
  a 
  and 
  b, 
  spicules 
  of 
  Stereoderma 
  validum; 
  c, 
  c?, 
  the 
  same, 
  

  

  seen 
  a 
  little 
  out 
  of 
  focus; 
  e^ 
  a 
  smaller 
  spicule 
  ; 
  /, 
  a 
  spicule 
  

   seen 
  in 
  side 
  view. 
  

  

  P. 
  Phyllophorus 
  proteus. 
  F'. 
  Parts 
  of 
  calcareous 
  ring. 
  

  

  G. 
  Holotliuria 
  macleart. 
  

  

  All 
  but 
  figs. 
  D 
  and 
  F' 
  are 
  magnified 
  220 
  times, 
  and 
  are 
  figures 
  of 
  

   spicules; 
  D 
  is 
  magnified 
  f, 
  F' 
  twice. 
  

  

  Plate 
  X. 
  

  

  Fig. 
  A. 
  Antedon 
  carpenteri, 
  nat. 
  size. 
  A 
  a, 
  A 
  5, 
  A 
  c. 
  First, 
  second, 
  

   and 
  typical 
  pinnules, 
  x 
  3. 
  

  

  B. 
  pumila, 
  X 
  3. 
  B 
  a, 
  B 
  h. 
  First 
  and 
  fourth 
  pinnules, 
  

  

  X3. 
  

  

  C. 
  loveni, 
  nat. 
  size. 
  Ca,Ch,Cc. 
  First, 
  third, 
  and 
  typical 
  

  

  pinnules, 
  x 
  3. 
  C 
  d, 
  C 
  e. 
  Dorsal 
  surface 
  of 
  arms 
  in 
  regions 
  

   marked 
  x 
  and 
  y 
  in 
  C, 
  x 
  3. 
  

  

  Plate 
  XI. 
  

  

  Fig. 
  A. 
  Antedon 
  bidens, 
  X 
  2. 
  A 
  a. 
  A 
  cirrus, 
  X 
  4, 
  Ab, 
  Ac. 
  First 
  

   and 
  third 
  pinnules, 
  x 
  4. 
  

  

  B. 
  deci2nens, 
  x 
  f. 
  B 
  a. 
  Arm-joints 
  from 
  above, 
  x 
  4. 
  

  

  