﻿The 
  Fauna 
  of 
  the 
  Niagara 
  Group. 
  139 
  

  

  enlarges 
  to 
  the 
  base 
  of 
  the 
  arms. 
  Radial 
  series 
  of 
  three 
  plates 
  

   each, 
  the 
  first 
  of 
  these 
  heptagonal, 
  and 
  the 
  largest 
  plates 
  

   in 
  the 
  body 
  ; 
  second 
  radials 
  a 
  little 
  smaller 
  than 
  the 
  first, 
  oc- 
  

   tagonal 
  ; 
  third 
  radials 
  much 
  smaller, 
  heptagonal, 
  and 
  sup- 
  

   porting 
  on 
  each 
  upper 
  sloping 
  side 
  a 
  series 
  of 
  two 
  supraradi- 
  

   als, 
  the 
  upper 
  one 
  apparently 
  a 
  bifurcating 
  plate 
  in 
  some 
  of 
  

   the 
  rays. 
  

  

  The 
  interradial 
  series, 
  in 
  three 
  of 
  the 
  areas, 
  are 
  one, 
  one, 
  

   and 
  two 
  or 
  three, 
  and 
  in 
  the 
  other 
  two 
  areas 
  one, 
  two 
  and 
  

   three 
  or 
  four. 
  The 
  summit 
  is 
  pentalobate, 
  covered 
  by 
  small 
  

   plates, 
  and 
  showing 
  the 
  base 
  of 
  a 
  slightly 
  excentric 
  proboscis. 
  

   The 
  plates 
  of 
  the 
  body 
  are 
  smooth 
  in 
  the 
  middle, 
  with 
  short, 
  

   abrupt, 
  angular 
  ridges 
  near 
  the 
  margin, 
  which 
  meet 
  similar 
  

   ridges 
  of 
  the 
  adjoining 
  plates 
  at 
  the 
  suture 
  lines. 
  

  

  Height 
  from 
  the 
  base 
  to 
  the 
  summit 
  but 
  little 
  more 
  than 
  

   half 
  an 
  inch, 
  and 
  greatest 
  width 
  at 
  the 
  arm 
  bases 
  about 
  the 
  

   same. 
  

  

  The 
  genus 
  Turbinocrintjs 
  of 
  Troost 
  differs 
  from 
  Melocri- 
  

   nxjs 
  in 
  having 
  the 
  first 
  plate 
  of 
  one 
  of 
  the 
  interradial 
  spaces 
  

   (or 
  the 
  first 
  anal 
  plate) 
  truncating 
  one 
  of 
  the 
  basal 
  plates, 
  

   which 
  does 
  not 
  occur 
  in 
  any 
  known 
  species 
  of 
  Melocrinus. 
  

   The 
  structure 
  of 
  Turbinocrinus 
  above 
  the 
  basal 
  plates 
  is 
  

   similar 
  to 
  Actinocrinus, 
  differing 
  from 
  that 
  genus 
  only 
  in 
  

   the 
  presence 
  of 
  four 
  basal 
  plates. 
  

  

  KHODOCRINUS 
  Miller. 
  

   ' 
  Subgenus 
  LYRIOCMNUS 
  Hall. 
  

   Rhodocrinus 
  (Lyriocrinus) 
  Melissa. 
  

  

  Plate 
  15, 
  Figs. 
  18-27. 
  

  

  Rhodocrinus 
  Melissa 
  Hall. 
  Trans. 
  Alb. 
  Inst., 
  vol. 
  iv, 
  p. 
  198. 
  Abstract, 
  p. 
  4; 
  

   May, 
  1863. 
  

  

  Body 
  depressed 
  sub 
  spherical, 
  or 
  nearly 
  hemispheric 
  ; 
  base 
  

   nearly 
  flat 
  or 
  very 
  depressed 
  convex 
  ; 
  central 
  column 
  cavity 
  

   abruptly 
  and 
  deeply 
  depressed 
  ; 
  sides 
  inflated 
  in 
  the 
  lower 
  

   part 
  and 
  contracted 
  just 
  below 
  the 
  arm-bases, 
  where 
  it 
  is 
  again 
  

   a 
  little 
  expanded. 
  Basal 
  plates 
  very 
  small, 
  concealed 
  within 
  

   the 
  cavity 
  and 
  covered 
  by 
  the 
  column. 
  Subradial 
  plates 
  elon- 
  

  

  