﻿298 
  

  

  P. 
  H. 
  CAKPENTEE 
  ON 
  THE 
  EELATIONS 
  OF 
  

  

  31. 
  On 
  the 
  Relations 
  of 
  Hyboceines, 
  Baeeoceinus, 
  and 
  Hybo- 
  

   cystites. 
  By 
  P. 
  Heebeet 
  Caepentee, 
  Esq., 
  M.A., 
  Assistant 
  

   Master 
  at 
  Eton 
  College. 
  Communicated 
  by 
  Prof. 
  P. 
  Maetin 
  

   Dencan, 
  1T.B. 
  Lond., 
  F.R.S., 
  Y.P.G.S. 
  (Read 
  May 
  10, 
  1882.) 
  

  

  [Plate 
  XI.] 
  

  

  The 
  Crinoids 
  from 
  the 
  Lower 
  Silurian 
  of 
  Canada 
  for 
  which 
  the 
  

   genus 
  Hybocrinus 
  was 
  established 
  by 
  Billings* 
  in 
  1856 
  are 
  remark- 
  

   able 
  for 
  the 
  protuberance 
  of 
  the 
  anal 
  side 
  of 
  the 
  cup, 
  so 
  that 
  it 
  has 
  

   somewhat 
  of 
  a 
  humpbacked 
  appearance, 
  as 
  is 
  expressed 
  in 
  Billings's 
  

   generic 
  name. 
  Resting 
  on 
  the 
  stem 
  are 
  five 
  pentagonal 
  basals, 
  

   above 
  and 
  alternating 
  with 
  which 
  is 
  a 
  row 
  of 
  five 
  plates 
  (fig. 
  I. 
  a, 
  

   and 
  PI. 
  XI. 
  figs. 
  3, 
  4, 
  5). 
  Four 
  of 
  these 
  are 
  arm-bearing 
  radials. 
  

   The 
  fifth 
  is 
  a 
  hexagonal 
  " 
  anal, 
  1 
  ' 
  or 
  (as 
  I 
  prefer 
  to 
  call 
  it) 
  azygos 
  

   plate, 
  on 
  the 
  right 
  upper 
  edge 
  of 
  which 
  rests 
  a 
  small 
  arm-bearing 
  

   radial, 
  while 
  its 
  left 
  upper 
  edge 
  bears 
  a 
  smaller 
  and 
  true 
  anal 
  plate. 
  

  

  These 
  characters 
  are 
  well 
  shown 
  in 
  fig. 
  I. 
  a, 
  which 
  is 
  a 
  copy 
  of 
  

   Billings's 
  original 
  diagram 
  of 
  the 
  genus 
  ; 
  and 
  also 
  in 
  PL 
  XI. 
  figs. 
  

   3, 
  4, 
  and 
  5, 
  which 
  represent 
  the 
  left, 
  right, 
  and 
  anal 
  sides 
  of 
  a 
  

   specimen 
  from 
  the 
  upper 
  part 
  of 
  the 
  Trenton 
  beds 
  of 
  Mercer 
  

   County, 
  Kentucky, 
  IT. 
  S. 
  A. 
  

  

  A 
  form 
  somewhat 
  similar 
  to 
  Hybocrinus, 
  though 
  lacking 
  the 
  second 
  

   or 
  true 
  anal 
  plate, 
  had 
  been 
  described 
  some 
  years 
  previously 
  by 
  Yon 
  

   Leuchtenbergt 
  under 
  the 
  name 
  of 
  Apiocrinus 
  dipentas 
  (fig. 
  I. 
  b 
  ; 
  

  

  Fig. 
  I. 
  

  

  Calyx-diagrams 
  of 
  Hybocrinus 
  and 
  Baerocrinus. 
  

   a 
  

  

  CD 
  E 
  

  

  b. 
  Basal. 
  r. 
  Eadial. 
  a. 
  Anal 
  plate. 
  

  

  A. 
  Hybocrinus 
  tumidus. 
  After 
  Billings. 
  

  

  B. 
  H. 
  dipentas, 
  type. 
  After 
  Grewingk. 
  

  

  C, 
  D. 
  H 
  dipentas, 
  other 
  varieties. 
  After 
  Schmidt. 
  

   E. 
  Baerocrinus 
  Ungerni. 
  After 
  Grewingk. 
  

  

  * 
  Report, 
  Geological 
  Survey 
  of 
  Canada, 
  1856, 
  p. 
  274. 
  

  

  t 
  Beschreibung 
  einiger 
  neuen 
  Thierreste 
  der 
  Urwelt 
  yon 
  Zarskoje 
  Sselo 
  

  

  (St. 
  Petersburg, 
  1843, 
  4to.) 
  p. 
  17, 
  tab. 
  ii. 
  figs. 
  9 
  & 
  10. 
  

  

  