THE  REV.  R.  T.  LOWE  ON  ALEPISAURUS. 
399 
front,  one  twentieth.  It  is  considerably  thickened  at  the  base,  and  not  seated  in  a 
groove.  The  first  three  rays  are  simple,  but  not  pungent,  and  with  difficulty  distinguish- 
able ;  the  remaining  eleven  branched.  Of  these  eleven,  the  first  two  are  only  bifid, 
and  of  nearly  equal  length  with  the  third  simple  ray,  which  is  the  longest ;  the  three 
next  are  trifid,  but  rapidly  decrease  in  length  ;  the  last  six  are,  again,  only  bifid,  of  nearly 
equal  length,  the  last  four  being  about  the  height  of  the  first  simple  ray,  and  each  more 
remote  than  the  preceding.  The  first  simple  ray  is  not  rough. 
The  following  is  the  fin  formula  for  the  present  specimen : 
lstD.44.  2ndD.adipose.  A.3+11.  P.1  +  13.  V.  1 +9. C.  (J^P*  ft!-^l-  B.M.7. 
I  Un.  8  +  1  +  8  J 
Total  length,  to  the  tip  of  the  produced  upper  lobe  of  the  caudal  fin  extended,  62  inches. 
Greatest  depth,  being  close  behind  the  pectoral  fins,  3-^  inches. 
Greatest  thickness,  being  at  the  root  of  the  tail  or  just  behind  the  eyes,  1-1-  inch. 
Weight  little  more  than  4  lbs. 
The  lateral  line  resembles  a  gelatinous  band  or  ridge,  slightly  elevated  the  whole 
length  of  the  body,  but  most  remarkably  so,  and  forming  quite  a  keel,  from  about  the 
middle  of  the  anal  fin  to  the  setting  on  of  the  caudal.  After  the  fish  has  been  some 
time  out  of  the  water,  or  immersed  in  spirits,  this  gelatinous  keel  falls,  and  loses  nearly 
all  its  prominency.  It  is  marked  by  a  faint  black  stripe  or  fine,  accompanied  by  a 
series  of  pores,  set  at  irregular  intervals  along  each  side.  Throughout  its  whole  length 
it  is  nearer  the  dorsal  than  the  ventral  fine.  The  two  little  accessory  oblique  ridges  on 
each  side  the  termination  of  the  lateral  line,  at  the  root  of  the  caudal  fin,  present  in  the 
true  Mackarels  {Scomber  vulgaris  and  Colias),  as  well  as  in  the  Thunnies,  are  here  wanting. 
The  base  of  the  first  dorsal  fin  is  seated  in  a  deep  groove,  with  jelly-like  transparent 
margins.  This  groove  continues  backwards,  from  the  termination  of  the  first,  nearly 
to  the  second  dorsal  fin,  becoming  gradually  more  shallow  and  obsolete. 
The  anterior  branched  rays  of  the  pectoral  and  ventral  fins,  and  the  outer  rays  of 
both  lobes  of  the  caudal  fin,  have  the  bars  or  joints  remarkably  raised  and  prominent, 
resembling  knobs,  or  like  the  knuckles  of  the  fingers. 
The  extreme  lightness  of  this  fish,  in  proportion  to  its  size,  is  equally  remarkable 
with  its  peculiar  flaccidity.  The  head  seems  ready  to  separate  from  the  body  with  the 
smallest  force. 
This  third  specimen  was  much  more  brilliantly  coloured  than  either  of  the  former, 
though  in  a  precisely  similar  manner.  On  each  side,  at  the  origin  of  the  caudal  fin, 
was  a  large  metallic  iridescent  patch  of  extreme  splendour ;  and  the  same  hues  pre- 
vailed, in  almost  equal  brightness,  along  the  base  of  the  anal  fin.  The  iris  was  coppery 
and  golden,  the  pupil  black. 
In  my  former  reference  of  this  new  genus  to  Les  Tanioides  of  Cuvier,  I  was  merely 
guided  by  its  evident  affinity  to  Lepidopus  and  Trichiurus.  These  two  genera  are  now 
by  Cuvier  and  Valenciennes,  in  the  eighth  volume  of  their  '  Histoire',  removed  from 
the  Tanioides,  with  which  they  were  associated  formerly  by  Cuvier  in  his  second  or 
3  G  2 
