﻿542 
  REPORT 
  OF 
  COMMISSIONER 
  OF 
  FISH 
  AND 
  FISHERIES. 
  [54] 
  

  

  The 
  appendicular 
  skeleton 
  of 
  the 
  cranium, 
  or 
  the 
  cranial 
  visceral 
  

   arches 
  possessing 
  endoskeletal 
  supports, 
  are 
  apposed 
  to 
  theinfero-lateral 
  

   parts 
  of 
  the 
  skull 
  at 
  the 
  anterior 
  part 
  of 
  the 
  auditory 
  region. 
  

  

  The 
  most 
  important 
  of 
  these 
  arches 
  is 
  the 
  compound 
  hyoid 
  and 
  man- 
  

   dibular, 
  supported 
  by 
  a 
  common 
  hyomaudibular 
  element, 
  Hm, 
  which 
  

   abuts 
  with 
  its 
  upper 
  end 
  upon 
  the 
  anterior 
  wall 
  of 
  the 
  auditory 
  capsule. 
  

   Iuferiorly 
  the 
  hyomandibular 
  gives 
  support 
  (1) 
  to 
  the 
  mandible, 
  now 
  

   entirely 
  constituted 
  of 
  Meckel's 
  cartilage, 
  il/fr, 
  but 
  around 
  which 
  articu- 
  

   lar, 
  angular, 
  and 
  dentary 
  parostoses 
  are 
  subsequently 
  laid 
  down 
  in 
  

   membrane; 
  and 
  (2) 
  to 
  the 
  hyoid 
  arch, 
  through 
  the 
  intermediation 
  of 
  a 
  

   short 
  cylindrical 
  element, 
  the 
  interhyal 
  I 
  Hy, 
  which 
  in 
  its 
  turn 
  sup- 
  

   ports 
  a 
  series 
  of 
  elements 
  consisting 
  of 
  the 
  ceratohyal 
  G 
  Hy, 
  hypohyal 
  

   H 
  Hy, 
  and 
  urohyal 
  G 
  Hy. 
  

  

  The 
  changes 
  which 
  the 
  hyomandibular 
  has 
  undergone 
  in 
  the 
  course 
  

   of 
  further 
  development 
  are 
  quite 
  complex. 
  The 
  principal 
  portion 
  -of 
  

   the 
  upper 
  half 
  becomes 
  the 
  ossified 
  hyomandibular 
  element 
  of 
  the 
  

   adult, 
  an 
  articular 
  knob 
  being 
  formed 
  on 
  its 
  posterior 
  border, 
  which 
  

   supports 
  the 
  operculum. 
  Its 
  inferior 
  half 
  represents 
  the 
  quadrate 
  of 
  

   authors. 
  Between 
  the 
  quadrate 
  and 
  hyomandibular 
  portion 
  the 
  carti- 
  

   lage 
  representing 
  the 
  symplectic 
  does 
  not 
  seem 
  to 
  be 
  well 
  distinguished. 
  

   The 
  inner, 
  upper, 
  anterior 
  part 
  of 
  the 
  hyomandibular 
  bar 
  takes 
  part 
  in 
  

   the 
  formation 
  of 
  the 
  hinder 
  part 
  of 
  the 
  pterygoid, 
  i. 
  e., 
  the 
  metaptery- 
  

   goid 
  of 
  the 
  adult. 
  The 
  ecto- 
  and 
  entopterygoid 
  are 
  apparently 
  differen- 
  

   tiations 
  of 
  the 
  posterior 
  separate 
  element 
  of 
  the 
  palatopterygoid 
  arch 
  

   PI 
  PL 
  

  

  The 
  branchial 
  arches 
  are 
  five 
  in 
  number; 
  the 
  posterior 
  is 
  imperfectly 
  

   developed 
  above. 
  At 
  the 
  inner 
  ends 
  of 
  the 
  posterior 
  branchial 
  bars 
  

   are 
  placed 
  a 
  pair 
  of 
  epipharyngeal 
  plates, 
  Phb, 
  bearing 
  teeth 
  even 
  at 
  

   this 
  early 
  stage. 
  The 
  branchial 
  bars 
  are 
  not 
  yet 
  definitely 
  segmented 
  

   into 
  their 
  lateral 
  elements. 
  Cartilaginous 
  copula? 
  or 
  basibranchials, 
  B 
  

   jB, 
  are 
  present 
  in 
  the 
  floor 
  of 
  the 
  branchial 
  region, 
  as 
  shown 
  in 
  section 
  

   in 
  fig. 
  174. 
  

  

  A 
  very 
  remarkable 
  series 
  of 
  cephalic 
  appendages 
  now 
  remains 
  to 
  be 
  

   described. 
  These 
  are 
  the 
  maxillary, 
  nasal, 
  and 
  mental 
  barbels. 
  Of 
  

   these 
  the 
  nasal 
  pair 
  only 
  is 
  not 
  represented 
  in 
  cartilage 
  at 
  the 
  stage 
  of 
  

   development 
  here 
  under 
  consideration, 
  but 
  even 
  this 
  one 
  develops 
  a 
  

   chondritied 
  axial 
  support 
  at 
  a 
  later 
  stage. 
  

  

  Whether 
  the 
  endoskeletal 
  part 
  of 
  the 
  upper 
  end 
  of 
  the 
  so-called 
  max- 
  

   illary 
  barbel 
  in 
  reality 
  represents 
  the 
  maxillary 
  bone 
  of 
  other 
  fishes 
  

   seems 
  somewhat 
  open 
  to 
  doubt, 
  as 
  the 
  proximal 
  ossification 
  of 
  the 
  car- 
  

   tilaginous 
  support 
  of 
  this 
  barbel 
  would 
  give 
  this 
  element 
  in 
  the 
  cat- 
  

   fishes 
  a 
  cartilaginous 
  origin, 
  which 
  is 
  at 
  variance 
  with 
  what 
  is 
  known 
  

   of 
  the 
  development 
  of 
  its 
  homologue 
  in 
  all 
  other 
  forms 
  of 
  Teleosts, 
  in 
  

   which 
  it 
  arises 
  as 
  a 
  membrane 
  bone. 
  True, 
  it 
  ossifies 
  on 
  the 
  surface 
  of 
  

   the 
  cartilaginous 
  support 
  of 
  the 
  barbel, 
  even 
  in 
  Ictalurus, 
  yet 
  it 
  is 
  barely 
  

  

  