﻿PACHYC0RMID2E. 
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  insignificant. 
  Pin-fulcra 
  minute 
  or 
  absent. 
  Pectoral 
  fins 
  large 
  and 
  

   sickle-shaped, 
  the 
  rays 
  only 
  branching 
  and 
  articulated 
  at 
  the 
  

   extreme 
  end; 
  pelvic 
  fins 
  absent 
  ; 
  dorsal 
  in 
  advance 
  of 
  the 
  anal 
  fin, 
  

   which 
  is 
  not 
  much 
  extended 
  ; 
  caudal 
  fin 
  very 
  deeply 
  forked. 
  Scales 
  

   small 
  and 
  very 
  deeply 
  imbricating, 
  those 
  of 
  the 
  ventral 
  aspect 
  

   scarcely 
  broader 
  than 
  deep 
  ; 
  lateral 
  line 
  conspicuous. 
  

  

  The 
  most 
  characteristic 
  feature 
  in 
  the 
  skull 
  of 
  this 
  genus 
  is 
  the 
  

   median 
  elevation 
  of 
  the 
  parietooccipital 
  region, 
  which 
  affects 
  a 
  

   sharply-defined 
  triangular 
  area 
  at 
  the 
  hinder 
  end 
  of 
  the 
  cranial 
  

   roof. 
  The 
  roof-bones 
  themselves 
  appear 
  to 
  be 
  all 
  fused 
  together 
  

   into 
  a 
  continuous 
  shield, 
  and 
  the 
  surface 
  is 
  completely 
  covered 
  with 
  

   a 
  very 
  fine 
  granular 
  ornament. 
  Traces 
  of 
  the 
  sutures 
  between 
  the 
  

   frontals, 
  squamosals, 
  and 
  parietals 
  are, 
  however, 
  sometimes 
  seen 
  ; 
  

   and 
  the 
  frontals 
  are 
  thus 
  shown 
  to 
  form 
  the 
  greater 
  part 
  of 
  the 
  

   hinder 
  elevation. 
  The 
  elements 
  in 
  the 
  otic 
  region 
  are 
  well 
  ossified, 
  

   though 
  not 
  hitherto 
  precisely 
  determined 
  ; 
  but 
  there 
  appears 
  

   to 
  be 
  no 
  ossified 
  interorbital 
  septum. 
  The 
  parasphenoid, 
  when 
  

   viewed 
  from 
  the 
  side, 
  is 
  observed 
  to 
  be 
  gently 
  arched, 
  bulging 
  

   slightly 
  downwards 
  ; 
  while 
  the 
  vomers 
  seem 
  to 
  be 
  completely 
  

   fused 
  with 
  the 
  mesethmoid. 
  Of 
  the 
  facial 
  bones, 
  by 
  far 
  the 
  largest 
  

   and 
  most 
  conspicuous 
  are 
  two 
  suborbitals 
  (postorbitals), 
  which 
  

   occupy 
  nearly 
  the 
  whole 
  of 
  the 
  cheek 
  between 
  the 
  preoperculum 
  

   and 
  the 
  orbit. 
  The 
  circumorbitals 
  are 
  comparatively 
  small, 
  and 
  

   have 
  only 
  been 
  satisfactorily 
  observed 
  as 
  a 
  series 
  of 
  little 
  plates, 
  

   all 
  broader 
  than 
  deep, 
  on 
  the 
  anterior 
  border 
  of 
  the 
  suborbitals. 
  

   The 
  sclerotic 
  capsule 
  is 
  ossified. 
  The 
  maxilla 
  is 
  long 
  and 
  slender, 
  

   tapering 
  in 
  front, 
  deepest 
  behind 
  ; 
  and 
  its 
  hinder 
  margin 
  is 
  exca- 
  

   vated 
  to 
  receive 
  a 
  large, 
  short, 
  and 
  deep 
  supramaxilla, 
  which 
  does 
  

   not 
  extend 
  upwards 
  on 
  the 
  cheek 
  higher 
  than 
  the 
  maxilla 
  itself. 
  

   The 
  premaxilla 
  has 
  not 
  been 
  observed, 
  and 
  may 
  perhaps 
  be 
  fused 
  

   with 
  the 
  rostrum. 
  The 
  structure 
  of 
  the 
  mandible 
  is 
  not 
  yet 
  satis- 
  

   factorily 
  known 
  ; 
  but 
  the 
  splenial 
  is 
  evidently 
  a 
  delicate 
  plate 
  with 
  

   comparatively 
  minute 
  teeth, 
  while 
  the 
  angular 
  bone 
  occupies 
  only 
  a 
  

   short 
  extent 
  of 
  the 
  outer 
  face 
  of 
  the 
  ramus. 
  

  

  There 
  is 
  a 
  large 
  gular 
  plate 
  completely 
  covering 
  the 
  anterior 
  

   portion 
  of 
  the 
  space 
  between 
  the 
  mandibular 
  rami, 
  while 
  the 
  

   branchiostegal 
  rays 
  are 
  short 
  and 
  numerous, 
  often 
  as 
  many 
  as 
  50. 
  

   Of 
  the 
  opercular 
  apparatus 
  the 
  most 
  characteristic 
  feature 
  is 
  the 
  

   very 
  large 
  size 
  of 
  the 
  suboperculum, 
  which 
  is 
  trapezoidal 
  in 
  form 
  and 
  

   throws 
  sharply 
  forwards 
  the 
  apex 
  of 
  the 
  triangular 
  operculum. 
  

   The 
  preoperculum 
  and 
  interoperculum 
  are 
  narrow 
  and 
  comparatively 
  

   small. 
  The 
  supratemporal 
  plates 
  resemble 
  those 
  of 
  Amia. 
  

  

  The 
  notochord 
  must 
  have 
  been 
  always 
  persistent, 
  though 
  there 
  

  

  