﻿156 
  MR. 
  P. 
  A. 
  BATHER 
  ON 
  TRIGOtfOCRIlttlS 
  FROM 
  

  

  branch, 
  and 
  that 
  they 
  were 
  attached 
  directly 
  to 
  the 
  first 
  radials 
  : 
  this 
  f 
  

   he 
  admits, 
  would 
  be 
  abnormal. 
  That 
  arms 
  were 
  actually 
  present, 
  

   though 
  doubtless 
  minute, 
  is 
  proved 
  by 
  the 
  aperture 
  of 
  a 
  canal 
  in 
  the 
  

   middle 
  of 
  the 
  articular 
  facet 
  of 
  the 
  first 
  radial. 
  Besides 
  this, 
  the 
  

   depressions 
  for 
  the 
  attachment 
  of 
  the 
  various 
  muscles 
  and 
  the 
  

   articular 
  ridge 
  are 
  quite 
  evident. 
  In 
  Trigonocrinus, 
  however, 
  the 
  

   process 
  of 
  degeneration 
  of 
  the 
  arms 
  has 
  advanced 
  so 
  far 
  that 
  not 
  only 
  

   are 
  the 
  muscular 
  attachments 
  all 
  but 
  invisible, 
  but 
  the 
  canal 
  has 
  no 
  

   longer 
  any 
  opening, 
  or, 
  at 
  least, 
  none 
  that 
  can 
  be 
  distinguished 
  

   with 
  a 
  strong 
  lens 
  (PL 
  VI. 
  fig. 
  5). 
  Correlated 
  with 
  this 
  is 
  the 
  slightly 
  

   different 
  shape 
  of 
  the 
  petals, 
  or 
  rather 
  spines, 
  which 
  no 
  longer 
  present 
  

   a 
  flat 
  surface 
  against 
  which 
  the 
  second 
  and 
  third 
  radials 
  might 
  fit, 
  

   as 
  they 
  do 
  in 
  Phyllocrinus 
  and 
  Eug. 
  caryophyllatus. 
  Whether 
  any 
  

   rudiments 
  of 
  arms 
  were 
  still 
  present 
  in 
  the 
  living 
  animal, 
  we 
  cannot 
  

   say 
  ; 
  from 
  the 
  evidence 
  as 
  yet 
  before 
  us, 
  it 
  does 
  not, 
  however, 
  seem 
  

   likely 
  that 
  such 
  rudiments 
  can 
  have 
  been 
  more 
  than 
  fleshy 
  processes. 
  

  

  Another 
  point 
  of 
  distinction 
  is 
  the 
  small, 
  round, 
  ventral 
  aperture 
  

   of 
  the 
  calycal 
  cavity 
  with 
  its 
  enclosing 
  rim. 
  In 
  this 
  there 
  are 
  no 
  

   traces 
  of 
  radial 
  furrows, 
  and 
  it 
  is 
  altogether 
  very 
  unlike 
  the 
  broad, 
  

   shallow 
  basin 
  of 
  most 
  other 
  Eugeniacrinidse 
  ; 
  but 
  some 
  of 
  the 
  later 
  

   Oxfordian 
  species 
  of 
  Phyllocrinus 
  show 
  a 
  gradual 
  deepening 
  and 
  

   narrowing 
  of 
  the 
  calycal 
  cavity, 
  and 
  in 
  them 
  the 
  radial 
  furrows 
  are 
  

   rather 
  fainter 
  than 
  usual 
  — 
  e. 
  g. 
  P. 
  fenestratus, 
  Dumortier, 
  and 
  still 
  

   more 
  P. 
  granulatus, 
  d'Orb. 
  (PL 
  VI. 
  fig. 
  15). 
  It 
  is 
  noticeable 
  also 
  that 
  

   the 
  latter 
  species 
  is 
  distinguished 
  by 
  an 
  ornamentation 
  of 
  granules, 
  

   which 
  are 
  not 
  unlike 
  those 
  of 
  the 
  present 
  species 
  of 
  Trigonocrinus 
  

   (PL 
  VI. 
  fig. 
  14). 
  The 
  rim 
  round 
  the 
  calycal 
  cavity, 
  like 
  the 
  thickened 
  

   mouth 
  of 
  a 
  bottle, 
  represents, 
  of 
  course, 
  the 
  raised 
  wall 
  on 
  the 
  inner 
  

   side 
  of 
  each 
  radial 
  facet 
  ; 
  it 
  is 
  the 
  last 
  relic 
  of 
  articulation. 
  

  

  The 
  last 
  and 
  most 
  important 
  character 
  in 
  which 
  Trigonocrinus 
  

   differs 
  from 
  other 
  Eugeniacrinidae 
  is 
  the 
  mode 
  of 
  union 
  between 
  stem 
  

   and 
  radials. 
  In 
  Eug. 
  caryophyllatus 
  the 
  radials 
  are 
  prolonged 
  

   downwards, 
  i. 
  e. 
  dorsalwards, 
  far 
  from 
  the 
  calycal 
  cavity 
  ; 
  they 
  often 
  

   narrow 
  to 
  a 
  stalk, 
  supporting 
  the 
  broad 
  and 
  flat 
  ventral 
  portion 
  of 
  the 
  

   calyx 
  ; 
  a 
  clove-like 
  appearance 
  is 
  thus 
  produced, 
  whence 
  the 
  specific 
  

   name. 
  In 
  Eug. 
  aberrans 
  this 
  downward 
  extension 
  of 
  the 
  radials 
  is 
  

   extraordinarily 
  marked 
  *. 
  In 
  both 
  these 
  species 
  the 
  radials 
  are 
  

   often 
  fused, 
  and 
  their 
  aboral 
  ends 
  are 
  cut 
  off 
  quite 
  straight. 
  The 
  

   flat 
  surface 
  thus 
  formed 
  is 
  far 
  removed 
  from 
  the 
  calycal 
  cavity, 
  and 
  

   it 
  is 
  pierced 
  only 
  by 
  a 
  small 
  axial 
  canal. 
  It 
  is 
  a 
  sutural 
  surface, 
  

   and 
  marked, 
  like 
  the 
  corresponding 
  upper 
  surface 
  of 
  the 
  top 
  stem- 
  

   joint, 
  by 
  pustules 
  that 
  have 
  a 
  tendency 
  to 
  run 
  into 
  striae 
  (PL 
  VI. 
  

   fig. 
  10). 
  In 
  Eug. 
  nutans 
  this 
  sutural 
  surface 
  is 
  slightly 
  concave, 
  

   while 
  the 
  upper 
  surface 
  of 
  the 
  top 
  stem-joint 
  is 
  convex 
  in 
  proportion. 
  

   In 
  Eug. 
  Mussoni 
  the 
  concavity 
  and 
  corresponding 
  convexity 
  are 
  some- 
  

   what 
  greater. 
  In 
  all 
  typical 
  species 
  of 
  Phyllocrinus 
  this 
  concavity 
  

   has 
  become 
  a 
  deep, 
  narrow, 
  circular.hole 
  ; 
  into 
  this 
  was 
  inserted 
  either 
  

   the 
  whole 
  of 
  the 
  top 
  stem-joint, 
  or 
  a 
  cylindrical 
  prolongation 
  from 
  it, 
  

  

  * 
  De 
  Loriol, 
  ' 
  Pal. 
  Fran^.' 
  loc. 
  cit. 
  pi. 
  xv. 
  figs. 
  4-6. 
  

  

  