﻿LITTLE 
  -KISTOW^ 
  JTJEASSIC 
  CEINOIDS. 
  37 
  

  

  The 
  next 
  syzygy 
  is 
  equally 
  variable 
  in 
  position, 
  following 
  the 
  first 
  

   at 
  an 
  interval 
  of 
  from 
  0-3 
  joints. 
  The 
  syzygial 
  faces 
  are 
  marked 
  

   with 
  well-defined 
  radiating 
  strise, 
  just 
  as 
  in 
  the 
  Comatulce. 
  

  

  The 
  arm-joints 
  are 
  short 
  and 
  nearly 
  oblong 
  in 
  outline, 
  bearing 
  

   pinnules 
  alternately 
  upon 
  opposite 
  sides, 
  the 
  first 
  pinnule 
  being- 
  

   borne 
  by 
  the 
  second 
  brachial, 
  which 
  is 
  slightly 
  more 
  wedge-shaped 
  

   than 
  the 
  nearly 
  rhomboidal 
  first 
  brachial. 
  In 
  one 
  or 
  two 
  pinnules 
  

   of 
  the 
  specimen 
  represented 
  in 
  fig. 
  9 
  the 
  side-plates 
  of 
  the 
  ambu- 
  

   lacra 
  are 
  still 
  visible 
  ; 
  they 
  are 
  generally 
  similar 
  to 
  those 
  of 
  many 
  

   recent 
  species 
  of 
  Pentacrinus 
  and 
  Comatula, 
  though 
  somewhat 
  more 
  

   massive, 
  as 
  they 
  are 
  in 
  various 
  Palaeocrinoids. 
  

  

  5. 
  Remarks. 
  

  

  The 
  species 
  which 
  most 
  nearly 
  resemble 
  M. 
  Prattii 
  are 
  M. 
  Nodo- 
  

   tianus, 
  d'Orb., 
  and 
  the 
  small 
  variety 
  of 
  M. 
  Munsterianus, 
  to 
  which 
  

   the 
  name 
  Bucliianus 
  has 
  been 
  given*. 
  But 
  in 
  both 
  species 
  the 
  

   radials 
  are 
  relatively 
  wider 
  and 
  less 
  steeply 
  inclined 
  than 
  those 
  of 
  

   M. 
  Prattii. 
  This 
  is 
  more 
  especially 
  the 
  case 
  in 
  M. 
  Nodotianus, 
  

   which 
  species 
  is 
  also 
  distinguished 
  by 
  the 
  stem-joints 
  having 
  a 
  

   tendency 
  to 
  the 
  petaloid 
  markings 
  that 
  are 
  characteristic 
  of 
  the 
  

   Pentacrinidae. 
  

  

  A 
  possible 
  ally 
  of 
  M. 
  Prattii 
  is 
  the 
  singular 
  type 
  described 
  by 
  

   Quenstedtt 
  as 
  a 
  Pentacrinus 
  from 
  the 
  White 
  Jura, 
  y, 
  of 
  Sotzen- 
  

   hausen. 
  It 
  has 
  no 
  sign 
  of 
  any 
  verticils 
  of 
  cirrhi 
  on 
  the 
  stem, 
  and 
  

   the 
  number 
  of 
  arms 
  was 
  very 
  probably 
  limited 
  to 
  ten, 
  as 
  the 
  few 
  

   that 
  are 
  preserved 
  do 
  not 
  fork 
  as 
  far 
  as 
  the 
  tenth 
  brachial, 
  though 
  

   they 
  may 
  of 
  course 
  have 
  done 
  so 
  on 
  a 
  later 
  joint, 
  as 
  in 
  P. 
  bri- 
  

   ar 
  eus. 
  Quenstedt 
  says 
  nothing 
  about 
  the 
  surfaces 
  of 
  the 
  stem- 
  

   joints 
  ; 
  but 
  it 
  is 
  difficult 
  to 
  see 
  why 
  the 
  type 
  should 
  be 
  referred 
  to 
  

   Pentacrinus 
  rather 
  than 
  to 
  Miller 
  icrinus, 
  the 
  former 
  genus 
  being 
  

   especially 
  distinguished 
  by 
  the 
  presence 
  of 
  cirrhus-verticils 
  on 
  the 
  

   stem. 
  

  

  Among 
  the 
  various 
  types 
  of 
  Pentacrinus 
  the 
  calices 
  of 
  which 
  are 
  

   known, 
  that 
  which 
  most 
  closely 
  resembles 
  M. 
  Prattii 
  in 
  the 
  cha- 
  

   racters 
  of 
  its 
  calyx 
  is 
  the 
  recent 
  P. 
  Wyville-Tliomsoni 
  from 
  the 
  

   North 
  Atlantic 
  %. 
  The 
  radials 
  and 
  basals 
  are 
  about 
  the 
  same 
  

   relative 
  size 
  in 
  both 
  cases, 
  and 
  the 
  markings 
  and 
  slope 
  of 
  the 
  arti- 
  

   cular 
  faces 
  are 
  very 
  similar, 
  ■ 
  the 
  curious 
  concentric 
  lines 
  on 
  the 
  

   muscle-plates 
  of 
  the 
  Pentacrinus 
  occurring 
  also 
  on 
  those 
  of 
  the 
  

   Millericrinus 
  (PI. 
  I. 
  figs. 
  11, 
  13, 
  17, 
  20, 
  21). 
  The 
  ventral 
  

   aspect 
  of 
  the 
  calyx, 
  with 
  its 
  tolerably 
  wide 
  central 
  funnel, 
  is 
  also 
  

   very 
  much 
  the 
  same 
  in 
  both 
  cases, 
  that 
  of 
  the 
  Millericrinus 
  being 
  

   rather 
  the 
  flatter. 
  But 
  this 
  resemblance 
  disappears 
  when 
  the 
  two 
  

   calices 
  are 
  viewed 
  from 
  below. 
  In 
  the 
  Pentacrinus 
  the 
  facet 
  which 
  

   receives 
  the 
  top 
  stem-joint 
  and 
  is 
  formed 
  by 
  the 
  undersurfaces 
  of 
  the 
  

   basals 
  is 
  relatively 
  small, 
  and 
  the 
  petaloid 
  markings 
  of 
  the 
  Penta- 
  

   crinus-stem 
  begin 
  to 
  be 
  visible 
  upon 
  it. 
  This 
  facet 
  is 
  relatively 
  

  

  * 
  De 
  Loriol, 
  op. 
  cit. 
  pp. 
  35-39, 
  pi. 
  7. 
  fig. 
  14. 
  

   t 
  Op. 
  cit. 
  tab. 
  99. 
  fig. 
  174. 
  

  

  