﻿\-l4 
  

  

  I* 
  dekayi. 
  

  

  LXVII-LAMNIDiE, 
  

  

  ISUEOPSIS. 
  

  

  The 
  Mackerel 
  Porbeagle. 
  

  

  Body 
  cylindrical, 
  fusiform. 
  Head 
  saiall, 
  with 
  a 
  blnnt 
  pyr- 
  

   amidal 
  snout 
  ; 
  the 
  prsDor.-il 
  portion 
  of 
  tlie 
  latter 
  as 
  long 
  as 
  the 
  

   longitudinal 
  axis 
  of 
  the 
  cleft 
  of 
  the 
  mouth, 
  tetrahidal, 
  

   pointed. 
  Angle 
  of 
  the 
  month 
  midway 
  between 
  the 
  gill-open- 
  

   ing 
  and 
  nostril. 
  The 
  surface 
  of 
  the 
  head 
  exhibits, 
  under 
  the 
  

   lens, 
  numerous 
  minute 
  plates, 
  each 
  with 
  three 
  parallel 
  longi- 
  

   tudinal 
  elevated 
  lines, 
  producing 
  a 
  roughness 
  when 
  the 
  hand 
  

   is 
  moved 
  towards 
  the 
  head. 
  On 
  the 
  surface 
  of 
  the 
  head 
  arc 
  

   four 
  series 
  of 
  punctures 
  on 
  each 
  side, 
  commencing 
  nearly 
  op- 
  

   posite 
  to 
  the 
  posterior 
  margins 
  of 
  the 
  orbits, 
  dilating 
  and 
  

   extending 
  to 
  v.ithin 
  about 
  an 
  inch 
  of 
  the 
  extremity 
  of 
  the 
  

   snoat. 
  Imme.liately 
  before 
  the 
  eyes 
  is 
  a 
  large 
  patch 
  of 
  sim- 
  

   ilar 
  punctures, 
  which 
  extend 
  bejond 
  the 
  uostril« 
  ; 
  on 
  the 
  

   under-side 
  of 
  the 
  snout 
  is 
  a 
  triangular 
  patch 
  of 
  similar 
  punc- 
  

   tures, 
  extending 
  to 
  nearly 
  the 
  extremity 
  ; 
  a 
  regularly 
  curved 
  

   series 
  of 
  punctures 
  from 
  the 
  end 
  of 
  the 
  carina, 
  concurrent 
  

   with 
  the 
  back, 
  and 
  ending 
  just 
  anterior 
  to 
  the 
  origin 
  of 
  the 
  

   first 
  dorsal 
  fin. 
  All 
  these 
  punctures 
  are 
  the 
  apertures 
  of 
  

   mucous 
  ducts, 
  which 
  are 
  filled 
  with 
  a 
  transparent 
  jelly. 
  

   Eyes 
  moderate 
  ; 
  nostrils 
  doubly 
  curved, 
  sublaterah 
  Gill- 
  

   openings 
  extremely 
  wide, 
  the 
  width 
  of 
  the 
  first 
  being 
  rather 
  

   more 
  than 
  its 
  distance 
  from 
  the 
  last. 
  Teeth 
  of 
  various 
  shapes 
  

   and 
  sizes, 
  disposed 
  in 
  from 
  thiee 
  to 
  live 
  rows. 
  They 
  are 
  

   mostly 
  long 
  lancolato, 
  with 
  sharp 
  lateral 
  edges, 
  without 
  basal 
  

   cusps. 
  The 
  third 
  tooth 
  on 
  each 
  side 
  of 
  the 
  upper 
  jaw 
  is 
  

   much 
  smaller 
  than 
  those 
  next 
  to 
  it. 
  The 
  first 
  dorsal 
  fin, 
  

   which 
  has 
  its 
  origin 
  at 
  a 
  very 
  short 
  distance 
  from 
  the 
  base 
  of 
  

   the 
  pectorals, 
  is 
  quadrilateral, 
  higher 
  than 
  long; 
  its 
  upper 
  

   margin 
  is 
  excavated, 
  its 
  lower 
  angle 
  pointed. 
  The 
  second 
  

   dorsal 
  fin 
  is 
  very 
  small, 
  oblong 
  ; 
  its 
  lower 
  angle 
  behind 
  end- 
  

  

  