﻿3(} 
  P. 
  H. 
  CARPENTER 
  ON 
  SOME 
  NEW 
  OR 
  

  

  liarity 
  of 
  this 
  mode 
  of 
  articulation 
  was 
  first 
  noticed 
  by 
  J. 
  Miiller* 
  

  

  who 
  described 
  it 
  as 
  occurring 
  in 
  Pentacrinus 
  caput- 
  Medusce 
  and 
  in 
  

   the 
  Comatulce, 
  and 
  remarked 
  that 
  it 
  had 
  been 
  previously 
  figured 
  by 
  

   Goldfuss 
  in 
  P. 
  briareus 
  ; 
  while 
  he 
  gave 
  the 
  name 
  " 
  syzyzy 
  " 
  to 
  an 
  

   immovable 
  sutural 
  union 
  of 
  two 
  joints 
  such 
  as 
  occurs 
  between 
  the 
  

   original 
  third 
  and 
  fourth 
  brachials 
  of 
  most 
  Comatulce. 
  These 
  

   become 
  ultimately 
  united 
  into 
  one 
  double 
  joint, 
  the 
  outer 
  half 
  of 
  

   which 
  bears 
  a 
  pinnule 
  ; 
  and 
  similar 
  syzyzial 
  unions 
  occur 
  at 
  longer 
  

   or 
  shorter 
  intervals 
  throughout 
  the 
  whole 
  length 
  of 
  the 
  arms. 
  

   De 
  Loriol 
  t 
  has 
  somewhat 
  unfortunately 
  employed 
  the 
  name 
  " 
  syzyzy 
  ' 
  

   for 
  the 
  form 
  of 
  ligamentous 
  articulation 
  upon 
  a 
  vertical 
  ridge 
  which 
  

   occurs 
  between 
  the 
  second 
  and 
  third 
  radials 
  of 
  most 
  Is 
  T 
  eocrinoidea 
  

   (PI 
  I. 
  fig. 
  15), 
  and 
  speaks 
  of 
  the 
  distal 
  face 
  of 
  the 
  second 
  radial 
  

   as 
  presenting 
  'a 
  " 
  facette 
  articulaire 
  syzygale;" 
  though 
  the 
  second 
  

   epithet, 
  understood 
  in 
  its 
  original 
  sense, 
  implies 
  the 
  absence 
  of 
  any 
  

   articulation 
  J. 
  

  

  4. 
  The 
  Arms. 
  

   As 
  is 
  almost 
  invariably 
  the 
  rule 
  among 
  the 
  Neocrinoidea, 
  the 
  

   articulation 
  between 
  the 
  first 
  and 
  second 
  brachials 
  of 
  M. 
  Prattii 
  is 
  

   a 
  ligamentous 
  one, 
  like 
  that 
  between 
  the 
  second 
  and 
  third 
  radials. 
  

   Quenstedt's 
  figures 
  (Encriniden, 
  tab. 
  103) 
  show 
  that 
  the 
  rule 
  holds 
  

   good 
  in 
  M. 
  mespiliformis, 
  and 
  I 
  have 
  found 
  the 
  same 
  to 
  be 
  the 
  case 
  

  

  in 
  Ap. 
  Parlcinsoni. 
  ,,,.... 
  n. 
  £ 
  

  

  The 
  position 
  of 
  the 
  first 
  syzygial 
  or 
  double 
  joint 
  in 
  the 
  arms 
  ot 
  

   31. 
  Prattii 
  appears 
  to 
  vary 
  from 
  the 
  third 
  to 
  the 
  fifth 
  brachial, 
  and 
  

   not 
  to 
  have 
  the 
  constancy 
  which 
  is 
  met 
  with 
  among 
  the 
  Comatulce. 
  

   * 
  " 
  Ueber 
  den 
  P>au 
  des 
  Pentacrinus 
  caput-Medusa," 
  Abhandl. 
  d. 
  Berlin. 
  Akad. 
  

   1843, 
  p. 
  26 
  (of 
  separate 
  copy), 
  

   t 
  Op. 
  cit. 
  pp. 
  257, 
  258. 
  .. 
  10 
  ,. 
  T1 
  . 
  . 
  , 
  .... 
  

  

  + 
  In 
  a 
  previous 
  paper 
  (this 
  Journ. 
  vol. 
  xxxvu. 
  p. 
  134) 
  I 
  have 
  pointed 
  out 
  that 
  

   it 
  is 
  a 
  mistake 
  to 
  suppose 
  that 
  MiUericrinus 
  differs 
  from 
  Apiocrmus 
  m 
  the 
  

   presence 
  of 
  an 
  articular 
  facet 
  on 
  the 
  first 
  radials, 
  for 
  traces 
  of 
  a 
  transverse 
  

   articular 
  ridge 
  and 
  of 
  muscle- 
  and 
  ligament-fossae 
  can 
  be 
  made 
  out 
  on 
  the 
  

   central 
  ends 
  of 
  the 
  first 
  radials 
  in 
  good 
  specimens 
  of 
  Apiocrmus. 
  I 
  had 
  not 
  at 
  

   that 
  time 
  seen 
  any 
  well-preserved 
  calyx 
  of 
  A. 
  Parkinsom, 
  and, 
  judging 
  from 
  

   d'Orbigny's 
  figure 
  (pi. 
  5. 
  fig. 
  6), 
  was 
  led 
  to 
  imagine 
  that 
  in 
  that 
  species 
  the 
  first 
  

   two 
  raaials 
  are 
  united 
  by 
  syzygy, 
  as 
  is 
  generally 
  supposed. 
  Recently, 
  however, 
  

   T 
  have 
  been 
  permitted 
  to 
  examine 
  the 
  excellent 
  calices 
  of 
  that 
  species 
  in 
  the 
  

   Museum 
  of 
  Practical 
  Geology, 
  and 
  I 
  find 
  that 
  it 
  too 
  had 
  a 
  muscular 
  articula- 
  

   tion 
  between 
  the 
  first 
  two 
  radials. 
  I 
  suspect 
  the 
  same 
  to 
  be 
  the 
  case 
  in 
  all 
  

   Aoiocrinites 
  The 
  power 
  of 
  movement, 
  however, 
  must 
  have 
  been 
  excessively 
  

   limited 
  and 
  the 
  presence 
  of 
  the 
  enormous 
  fossa 
  beneath 
  the 
  transverse 
  articular 
  

   ridee 
  distinguishes 
  this 
  form 
  of 
  articulation 
  from 
  that 
  met 
  with 
  m 
  most 
  ISeocri- 
  

   noidea 
  though 
  an 
  approach 
  to 
  it 
  occurs 
  in 
  some 
  species 
  of 
  Millenerinus. 
  

  

  I 
  mav 
  also 
  state 
  here 
  that 
  the 
  second 
  and 
  third 
  radials 
  of 
  Ap. 
  ParJcmsom 
  and 
  

   of 
  Av 
  'Meriani 
  (as 
  I 
  learn 
  from 
  specimens 
  kindly 
  lent 
  me 
  by 
  M. 
  de 
  loriol) 
  are 
  

   united 
  bv 
  ligamentous 
  articulation, 
  just 
  as 
  described 
  above 
  in 
  M. 
  Prathi, 
  

   though 
  the 
  lower 
  end 
  of 
  the 
  vertical 
  articular 
  ridge 
  in 
  the 
  Apiocnnus-radiixls 
  is 
  

   separated 
  from 
  the 
  dorsal 
  edge 
  of 
  the 
  plate 
  by 
  a 
  large 
  fossa 
  similar 
  to 
  that 
  on 
  

   the 
  first 
  radials, 
  and 
  either 
  absent 
  or 
  but 
  poorly 
  developed 
  m 
  Mill&rwnnus. 
  

  

  It 
  will 
  be 
  evident 
  from 
  these 
  considerations 
  that 
  Apiocrmus 
  conforms 
  more 
  

   Hoselv 
  to 
  the 
  type 
  of 
  Pentacrinus 
  and 
  Comatula 
  than 
  has 
  been 
  hitherto 
  sup- 
  

   posed, 
  though 
  the 
  enormous 
  expansion 
  of 
  the 
  calyx-plates 
  marks 
  it 
  off 
  very 
  

   distinctly 
  from 
  the 
  other 
  Neocrinoidea. 
  

  

  