﻿36 
  INTEODUCTION. 
  

  

  The 
  squamosal 
  is 
  a 
  bamixier-sliaped 
  boue, 
  tlie 
  anterior 
  

   brancli 
  of 
  wliicli 
  may 
  be 
  much 
  reduced, 
  as 
  in 
  Biifo^ 
  

   long 
  and 
  free, 
  as 
  in 
  Eana, 
  or 
  join 
  tlie 
  maxillary, 
  as 
  in 
  

   Discoglossus 
  and 
  Pelohates. 
  

  

  The 
  vomers 
  vary 
  much 
  in 
  size 
  according 
  to 
  the 
  

   genera 
  ; 
  they 
  are 
  largest 
  in 
  Discoglossus, 
  where 
  their 
  

   posterior 
  toothed 
  border 
  covers 
  over 
  the 
  palatines. 
  

   The 
  latter 
  bones, 
  if 
  present, 
  are 
  narrow 
  and 
  transverse, 
  

   and 
  extend 
  across 
  the 
  whole 
  palate 
  ; 
  in 
  Bufo 
  their 
  

   lower 
  surface 
  forms 
  a 
  cutting, 
  sometimes 
  serrated 
  edge, 
  

   which 
  makes 
  up 
  for 
  the 
  absence 
  of 
  vomerine 
  teeth. 
  

   The 
  pterygoids 
  are 
  trifurcate, 
  and 
  the 
  anterior 
  branch 
  

   may 
  or 
  may 
  not 
  reach 
  the 
  palatines, 
  or 
  may 
  be 
  much 
  

   produced 
  forwards 
  when 
  the 
  latter 
  bones 
  are 
  absent, 
  

   as 
  in 
  Bomhinator, 
  The 
  parasphenoid 
  is 
  a 
  large 
  bone 
  

   shaped 
  like 
  a 
  T, 
  or 
  like 
  a 
  dagger 
  with 
  very 
  short 
  

   handle. 
  

  

  Most 
  genera 
  have 
  a 
  cartilaginous 
  tympanic 
  ring 
  

   applied 
  to 
  the 
  outer 
  surface 
  of 
  the 
  hammer-shaped 
  

   squamosal, 
  in 
  the 
  upper 
  portion 
  of 
  which 
  ends 
  the 
  

   slender, 
  ossified, 
  stapedial 
  rod 
  (columella 
  auris). 
  

   The 
  tympanum 
  is 
  absent 
  in 
  Pelohates, 
  and 
  both 
  the 
  

   tympanum 
  and 
  the 
  stapedial 
  rod 
  in 
  Bomhinator, 
  

   which 
  in 
  this 
  respect 
  ag'ain 
  resembles 
  the 
  tailed 
  

   Batrachians. 
  

  

  In 
  Discoglossus 
  three 
  bones 
  invest 
  the 
  ]\Ieckelian 
  

   cartilao-e 
  which 
  forms 
  the 
  ramus 
  of 
  the 
  mandible 
  : 
  the 
  

   dentary 
  in 
  front, 
  the 
  angular 
  or 
  angulo-splenial 
  behind, 
  

   and 
  extending 
  more 
  to 
  the 
  front 
  on 
  the 
  inner 
  side, 
  

   and 
  a 
  small 
  bone 
  which 
  articulates 
  with 
  the 
  quadrate, 
  

   the 
  articular. 
  In 
  Eana 
  the 
  articular 
  remains 
  cartila- 
  

   ginous, 
  but 
  the 
  symphysial 
  cartilages 
  ossify, 
  forming 
  

   the 
  so-called 
  mento-Meckelian 
  or 
  symphjsial 
  bones, 
  

   which 
  in 
  adult 
  specimens 
  fuse 
  on 
  the 
  upper 
  side 
  

   with 
  the 
  dentary 
  (Fig. 
  14). 
  These 
  symphysial 
  bones 
  

   are 
  less 
  distinct 
  in 
  Hyla 
  and 
  Bufo, 
  less 
  still 
  or 
  even 
  

   almost 
  indistinguishable 
  in 
  the 
  Pelohatidae 
  and 
  Disco- 
  

   glossidm. 
  

  

  The 
  hyoid 
  varies 
  very 
  considerably 
  in 
  the 
  different 
  

  

  