﻿46 
  Dr. 
  H. 
  Ludwig 
  on 
  Ophiopteron 
  elegans. 
  

  

  lateral 
  scute 
  bears 
  in 
  the 
  first 
  place 
  near 
  the 
  tentacular 
  scale 
  

   a 
  hook 
  ; 
  then 
  follows 
  a 
  spinulose 
  spine, 
  and 
  beyond 
  this 
  

   begins 
  the 
  fin, 
  into 
  the 
  composition 
  of 
  which 
  (in 
  the 
  lower 
  

   and 
  middle 
  parts 
  of 
  the 
  arm) 
  there 
  enter 
  ten 
  bacilliform 
  

   spines. 
  The 
  hooks 
  possess 
  four 
  buccally 
  directed, 
  curved 
  

   points, 
  which 
  stand 
  in 
  a 
  row 
  one 
  below 
  the 
  other 
  ; 
  towards 
  

   the 
  apex 
  of 
  the 
  arm 
  the 
  number 
  of 
  points 
  diminishes 
  to 
  three 
  

   and 
  finally 
  to 
  two. 
  The 
  spinulose 
  spines 
  are 
  about 
  half 
  as 
  

   long 
  again 
  as 
  the 
  hooks, 
  but, 
  like 
  these, 
  stand 
  off 
  obliquely 
  

   from 
  the 
  arm 
  and 
  have 
  the 
  form 
  of 
  a 
  club 
  beset 
  with 
  spines 
  

   in 
  its 
  outer 
  half; 
  the 
  basal 
  portion 
  of 
  the 
  club 
  shows 
  an 
  

   enlargement 
  for 
  articulation 
  upon 
  the 
  band 
  of 
  the 
  lateral 
  

   scute. 
  The 
  supporting 
  rods 
  of 
  the 
  fin 
  are 
  also 
  attached 
  by 
  

   an 
  enlarged 
  base 
  ; 
  but 
  above 
  this 
  they 
  rather 
  quickly 
  diminish 
  

   into 
  a 
  thin 
  rod, 
  which 
  gradually 
  becomes 
  thinner 
  and 
  traverses 
  

   the 
  fin 
  to 
  its 
  free 
  lateral 
  margin, 
  following 
  a 
  slightly 
  curved 
  

   course. 
  The 
  supporting 
  rods 
  usually 
  do 
  not 
  terminate 
  in 
  a 
  

   simple 
  point, 
  but 
  fork 
  a 
  little 
  before 
  their 
  termination, 
  so 
  that 
  

   the 
  two 
  branches 
  of 
  the 
  fork 
  lie 
  close 
  together. 
  The 
  reticu- 
  

   late 
  structure 
  of 
  the 
  calcareous 
  bodies 
  of 
  the 
  Echinodermata 
  

   is 
  well 
  developed 
  in 
  the 
  thickened 
  base 
  of 
  the 
  supporting 
  

   rods, 
  but 
  is 
  deficient 
  in 
  their 
  middle 
  part, 
  although 
  it 
  is 
  indi- 
  

   cated 
  in 
  the 
  terminal 
  section 
  by 
  fine, 
  oblique, 
  transverse 
  

   canals. 
  If 
  we 
  distinguish 
  the 
  supporting 
  rods 
  by 
  consecu- 
  

   tive 
  numbers, 
  starting 
  from 
  the 
  ventral 
  surface 
  of 
  the 
  arm, 
  

   there 
  is 
  a 
  slight 
  increase 
  of 
  length 
  from 
  1 
  to 
  3 
  and 
  a 
  diminu- 
  

   tion 
  from 
  4 
  to 
  10 
  ; 
  5 
  is 
  of 
  about 
  the 
  same 
  length 
  as 
  1, 
  while 
  

   10 
  is 
  only 
  half 
  as 
  long. 
  

  

  The 
  fin 
  is 
  formed 
  by 
  a 
  thin 
  transparent 
  membrane, 
  in 
  

   which 
  we 
  can. 
  distinguish 
  an 
  inner 
  margin 
  attached 
  to 
  the 
  

   band 
  of 
  the 
  lateral 
  scute, 
  a 
  free 
  anterior 
  margin 
  directed 
  

   towards 
  the 
  tip 
  of 
  the 
  arm, 
  a 
  free 
  outer 
  margin, 
  and 
  a 
  free 
  

   posterior 
  margin 
  turned 
  towards 
  the 
  base 
  of 
  the 
  arm. 
  Tiie 
  

   course 
  of 
  the 
  line 
  of 
  insertion 
  of 
  the 
  fin 
  upon 
  the 
  lateral 
  scute 
  

   causes 
  the 
  anterior 
  margin 
  to 
  originate 
  on 
  the 
  ventral 
  surface 
  

   and 
  the 
  posterior 
  margin 
  on 
  the 
  dorsal 
  surface 
  of 
  the 
  arm. 
  

   As 
  the 
  whole 
  fin 
  from 
  the 
  anterior 
  to 
  the 
  posterior 
  margin 
  

   has 
  a 
  greater 
  extent 
  than 
  the 
  length 
  of 
  an 
  arm-joint, 
  the 
  con- 
  

   secutive 
  fins 
  lie 
  over 
  one 
  another 
  like 
  tiles, 
  so 
  that 
  in 
  looking 
  

   at 
  the 
  arm 
  from 
  the 
  back 
  the 
  aboral 
  portion 
  of 
  each 
  fin 
  is 
  

   overlain 
  by 
  the 
  adoral 
  part 
  of 
  the 
  next 
  one. 
  The 
  anterior 
  

   and 
  posterior 
  margins 
  of 
  the 
  fin 
  are 
  not 
  formed 
  by 
  the 
  first 
  

   and 
  last 
  supporting 
  rods, 
  but 
  by 
  a 
  narrow 
  border 
  of 
  the 
  fin- 
  

   membrane, 
  which 
  runs 
  along 
  the 
  rods 
  in 
  question. 
  At 
  the 
  

   free 
  outer 
  margin 
  the 
  fin-membrane 
  passes 
  in 
  curves 
  from 
  

   the 
  tip 
  of 
  one 
  supporting 
  rod 
  to 
  that 
  of 
  the 
  next. 
  

  

  