﻿EXTERNAL 
  CHAEACTERS. 
  9 
  

  

  II. 
  External 
  Characters. 
  

  

  As 
  these 
  Batrachians 
  liave 
  no 
  neck, 
  the 
  head 
  passes 
  

   directly 
  into 
  the 
  body, 
  and, 
  except 
  in 
  Pelohates, 
  where 
  

   the 
  skin 
  is 
  closely 
  adherent 
  to 
  the 
  rugose 
  skull, 
  the 
  

   demarcation 
  is 
  consequently 
  difficult 
  to 
  trace. 
  By 
  

   drawing 
  a 
  line 
  connecting 
  the 
  articular 
  extremities 
  

   of 
  the 
  mandible 
  we 
  obtain 
  approximately 
  the 
  exact 
  

   length 
  of 
  the 
  head, 
  the 
  greatest 
  width 
  beiog 
  at 
  the 
  

   commissures 
  of 
  the 
  jaws. 
  The 
  head 
  is 
  more 
  or 
  less 
  

   flattened, 
  with 
  prominent 
  eyeballs 
  covered 
  above 
  by 
  

   the 
  upper 
  eyelid, 
  which 
  is 
  continuous 
  with 
  the 
  rest 
  of 
  

   the 
  cephalic 
  integument. 
  The 
  upper 
  surface 
  of 
  the 
  

   head 
  may 
  be 
  limited 
  on 
  each 
  side 
  by 
  an 
  angular 
  line 
  

   extending 
  from 
  the 
  tip 
  of 
  the 
  snout 
  to 
  the 
  upper 
  

  

  Fig. 
  1. 
  

  

  Upper 
  views 
  of 
  heads 
  of 
  (a) 
  Bana 
  temporaria 
  and 
  

   (Bj 
  Bomhinator 
  igneus. 
  

  

  eyelid, 
  the 
  canthus 
  rostralis, 
  continued 
  behind 
  as 
  a 
  

   ridge 
  or 
  fold, 
  the 
  supra-temporal 
  ridge 
  (Fig. 
  1, 
  a). 
  

   In 
  some 
  forms, 
  such 
  as 
  Bomhinator 
  igneus 
  (Fig. 
  1, 
  b), 
  

   the 
  snout 
  is 
  simply 
  arched 
  from 
  one 
  lip 
  to 
  the 
  other, 
  

   and 
  there 
  is 
  no 
  trace 
  of 
  a 
  canthus 
  rostralis. 
  The 
  side 
  

   of 
  the 
  snout 
  below 
  the 
  canthus 
  rostralis 
  is 
  called 
  the 
  

   loreal 
  region. 
  The 
  length 
  of 
  the 
  snout 
  is 
  taken 
  by 
  

   applying 
  the 
  points 
  of 
  the 
  compasses 
  to 
  the 
  anterior 
  

   border 
  of 
  the 
  (bony) 
  orbit 
  and 
  the 
  very 
  tip 
  of 
  the 
  

   snout, 
  on 
  the 
  median 
  line. 
  

  

  The 
  nostrils 
  are 
  small 
  valvular 
  openings, 
  situated 
  

   between 
  the 
  end 
  of 
  the 
  snout 
  and 
  the 
  eyes, 
  alter- 
  

  

  