398 
THE  REV.  R.  T.  LOWE  ON  ALEPISAURUS. 
fragile,  not  pungent,  but  flexible  like  whalebone,  curving  backwards,  rounded,  and 
tapering  to  fine,  excessively  slender  points,  like  horse-hair,  webbed  quite  up  to  their 
tips  :  the  web  is  peculiarly  delicate,  of  extreme  tenuity,  and  inconceivably  fragile ; 
coloured  dark  iridescent  steely  blue,  with  a  pale  azure  hne  extending  partly  up  each 
ray,  as  in  former  specimens  ;  but  in  this  the  whole  outline  is  faintly  edged  with  white, 
of  which,  from  their  less  perfect  condition,  the  traces  only  were  visible  in  both  the  for- 
mer individuals. 
The  second  dorsal  fin  is  just  as  in  the  two  former  specimens.  Its  hinder  edge  is 
broad  and  flattened  towards  the  base,  as  in  the  dorsal  fins  of  certain  Sharks.  Its  height 
and  breadth  at  top  are  each  about  an  inch  and  a  half. 
The  most  striking  and  important  addition  is  the  correct  form  of  the  caudal  fin.  This 
organ  in  both  the  former  specimens  was  too  much  mutilated  to  warrant  any  attempt  at 
delineation  or  description.  In  the  present  it  is  deeply  forked,  and  composed,  as  in  the 
former  specimens,  of  nineteen  principal  rays,  of  which  ten  form  the  upper  and  nine  the 
lower  lobe.  Besides  these  nineteen,  there  are  eight  shorter  rays,  of  unequal  length,  at 
the  base  of  both  forks,  above  and  beneath.  The  great  peculiarity  which  this  third  speci- 
men has  brought  to  light,  is  the  production  of  the  upper  lobe  into  a  long,  gracefully- 
arched,  linear,  or  rather  tape-like,  broad,  flattened  filament,  composed  of  the  one  long 
outer  unbranched  ray,  and  of  three  with  part  of  the  fourth  of  the  next  inner  branched 
rays.  The  first  or  outermost  of  the  ten  rays  forming  the  upper  lobe  is  simple,  and  ex- 
tends considerably  beyond  the  extreme  tip  of  the  lower  lobe,  but  does  not  reach  half  the 
length  of  the  produced  part  of  the  upper,  of  which  it  forms  a  portion.  The  next  three 
rays  are  branched,  and  their  threads  or  branches  form  entirely,  along  with  the  former 
simple  ray,  the  produced  or  tape-hke  filament,  which  is  an  inch  broad  at  its  base, 
slightly  narrowing  towards  the  rather  obtuse  tip  to  about  one  third  of  an  inch.  There 
are  seven  threads  or  branches  of  these  rays,  running  nearly  parallel  and  reaching  to  the 
tip.  The  six  next  rays  are  much  branched,  and  gradually  shorter  ;  the  uppermost 
thread  or  branch  of  the  first  of  them,  i.  e.  of  the  fifth  ray  of  the  upper  lobe,  is  a  little 
produced,  and  forms  a  part  of  the  base  of  the  lengthened  filament. 
The  lower  lobe  of  the  caudal  fin  is  simple,  oblong-oval,  acute  at  the  tip.  Its  lowest 
ray  is  also  its  longest,  and  unbranched.  The  four  next  are  nearly  the  same  length,  and 
branched.    The  four  innermost  are  gradually  shorter,  and  also  branched. 
The  upper  lobe  is  between  one  third  and  one  fourth  of  the  whole  length.  The  lower 
lobe  is  one  tenth  of  the  whole  length. 
The  middle  rays  of  the  caudal  fin  are  faintly  barred,  but  much  branched  :  the  outer 
rays  are  very  strongly  barred,  but  gradually  less  branched  from  the  middle  outwards. 
The  caudal  fin  is  set  on  in  the  peculiar  manner  general  among  the  ScomhridcB.  It 
surrounds  the  termination  of  the  body  on  three  sides,  leaving  a  rectangular  central 
space  longer  than  deep.  This  pecuUarity  is  chiefly  owing  to  the  large  number  (eight) 
and  strength  of  the  supernumerary  shorter  rays,  both  above  and  beneath,  which  extend 
some  distance  forwards  along  the  dorsal  and  the  ventral  lines. 
The  anal  fin  is  one  fifteenth  of  the  entire  length,  and  its  greatest  height,  which  is  in 
