﻿140 
  Twenty-eighth 
  Eeport 
  on 
  the 
  State 
  Museum. 
  

  

  gate 
  heptagonal, 
  their 
  greatest 
  width 
  about 
  one-third 
  above 
  

   their 
  lower 
  margin. 
  Radial 
  plates 
  proportionally 
  large 
  ; 
  the 
  

   first 
  pentangular, 
  wedge-form 
  below; 
  the 
  second 
  hexagonal, 
  as 
  

   large 
  as 
  the 
  others 
  ; 
  the 
  third 
  usually 
  hexagonal 
  (sometimes 
  

   pentagonal), 
  supporting 
  on 
  the 
  upper 
  sloping 
  faces 
  one 
  or 
  two 
  

   large 
  supraradial 
  plates, 
  with 
  a 
  very 
  small 
  bifurcating 
  or 
  ax- 
  

   illary 
  plate 
  resting 
  in 
  an 
  excavation 
  in 
  the 
  middle 
  of 
  the 
  upper 
  

   margin 
  of 
  the 
  second, 
  above 
  which 
  commence 
  the 
  arm 
  plates 
  ; 
  

   resting 
  partly 
  on 
  this 
  small 
  plate, 
  and 
  partly 
  on 
  the 
  second 
  

   supraradial 
  plate 
  above 
  the 
  third 
  radial, 
  and, 
  upon 
  the 
  upper 
  

   margin 
  of 
  the 
  latter, 
  there 
  is 
  a 
  somewhat 
  large, 
  heptagonal, 
  

   intersupraradial 
  plate. 
  

  

  The 
  interradial 
  and 
  anal 
  series 
  consist 
  of 
  four 
  plates 
  each 
  ; 
  

   the 
  first 
  heptagonal, 
  as 
  large 
  as 
  the 
  radials 
  or 
  larger, 
  support- 
  

   ing 
  two 
  somewhat 
  smaller 
  hexagonal 
  plates 
  in 
  the 
  second 
  

   range, 
  one 
  still 
  smaller 
  in 
  the 
  third, 
  above 
  which 
  the 
  brachial 
  

   plates 
  of 
  the 
  adjacent 
  rays 
  unite 
  ; 
  the 
  anal 
  series 
  is 
  the 
  same 
  

   as 
  the 
  interradial 
  in 
  the 
  best 
  formed 
  specimens 
  ; 
  but 
  there 
  is 
  

   sometimes 
  a 
  slight 
  irregularity 
  seen 
  in 
  one 
  series, 
  which 
  we 
  

   infer 
  may 
  be 
  the 
  anal 
  side. 
  Surface 
  of 
  plates 
  flat 
  or 
  with 
  only 
  

   the 
  general 
  convexity 
  of 
  the 
  body, 
  covered 
  by 
  very 
  fine 
  con- 
  

   fluent 
  granules 
  or 
  interrupted 
  radiating 
  strise, 
  which 
  unite 
  at 
  

   the 
  sutures 
  ; 
  each 
  subradial 
  plate 
  is 
  marked 
  at 
  the 
  middle 
  of 
  

   the 
  lower 
  margin 
  with 
  a 
  small 
  triangular 
  node 
  and 
  a 
  some- 
  

   what 
  elevated 
  rim, 
  giving 
  a 
  pentalobate 
  border 
  to 
  the 
  basal 
  

   cavity. 
  In 
  many 
  specimens 
  the 
  first 
  radial 
  plate 
  is 
  marked 
  by 
  

   a 
  central 
  node. 
  

  

  Summit 
  nearly 
  flat 
  and 
  depressed 
  towards 
  the 
  margins 
  or 
  

   to 
  the 
  inner 
  side 
  of 
  the 
  arm- 
  bases, 
  composed 
  of 
  numerous 
  

   small 
  polygonal 
  plates, 
  with 
  a 
  subcentral 
  proboscis, 
  and 
  on 
  

   the 
  inner 
  side 
  of 
  each 
  pair 
  of 
  arms 
  a 
  foramen 
  opening 
  into 
  

   the 
  cavity 
  of 
  the 
  body. 
  Plates 
  of 
  the 
  dome 
  irregular 
  in 
  size 
  

   and 
  varying 
  in 
  different 
  individuals, 
  the 
  specimen 
  figured 
  

   having 
  larger 
  plates 
  than 
  some 
  others 
  which 
  have 
  been 
  subse- 
  

   quently 
  observed. 
  

  

  Arms 
  two 
  from 
  each 
  ray, 
  each 
  one 
  composed 
  of 
  short, 
  wide 
  

   pentagonal 
  plates 
  which 
  are 
  interlocking 
  at 
  their 
  adjacent 
  

   edges; 
  plates 
  gradually 
  becoming 
  shorter 
  and 
  the 
  arms 
  grad- 
  

   ually 
  tapering 
  to 
  their 
  extremities. 
  Length 
  of 
  arms 
  about 
  65 
  

   mm., 
  lateral 
  diameter 
  at 
  the 
  base 
  8 
  mm. 
  Column 
  round, 
  not 
  

   enlarging 
  at 
  its 
  junction 
  with 
  the 
  body, 
  and 
  uniformly 
  cylin- 
  

  

  