﻿EXTERNAL 
  OHARACTEES. 
  

  

  17 
  

  

  Fig. 
  7. 
  

  

  ~^^ 
  

  

  Limbs 
  of 
  TLijla 
  arhorea, 
  showing 
  variations 
  in 
  the 
  proportion 
  

   of 
  the 
  tibia. 
  The 
  dotted 
  line 
  indicates 
  the 
  middle 
  line 
  of 
  

   the 
  body. 
  

  

  The 
  great 
  development 
  of 
  the 
  hind 
  limbs 
  enables 
  

   these 
  Batrachians 
  to 
  proceed 
  by 
  leaps 
  ; 
  there 
  is, 
  how- 
  

   ever, 
  one 
  exception 
  among 
  the 
  European 
  forms, 
  viz. 
  

   Bufo 
  calamita, 
  in 
  which 
  the 
  limbs 
  are 
  so 
  short 
  as 
  to 
  

   render 
  hopping 
  impossible, 
  and 
  this 
  toad 
  progresses 
  at 
  

   a 
  running 
  pace 
  when 
  pursued. 
  The 
  other 
  extreme 
  is 
  

   furnished 
  by 
  Bana 
  agilis^ 
  which 
  owing 
  to 
  its 
  extremely 
  

   long 
  hind 
  limbs 
  is 
  able 
  to 
  cover 
  a 
  distance 
  of 
  six 
  feet 
  

   at 
  one 
  leap. 
  The 
  aquatic 
  habits 
  of 
  a 
  Batrachian 
  can, 
  

   as 
  a 
  rule, 
  be 
  gauged 
  by 
  the 
  extent 
  of 
  the 
  web 
  between 
  

   the 
  toes 
  : 
  thus 
  Bufo 
  calamita 
  and 
  Alytes, 
  which 
  have 
  

   only 
  rudimentary 
  webs, 
  are 
  very 
  bad 
  swimmers, 
  and 
  do 
  

   not 
  venture 
  far 
  from 
  the 
  shore 
  ; 
  whilst 
  Bana 
  esculenta 
  

   and 
  Bomhinator, 
  with 
  their 
  broadly- 
  webbed 
  toes, 
  spend 
  

   nearly 
  the 
  whole 
  of 
  the 
  active 
  period 
  in 
  the 
  water. 
  

   But 
  there 
  are 
  exceptions 
  : 
  Pelohates, 
  the 
  toes 
  of 
  

   which 
  are 
  completely 
  webbed, 
  sojourns 
  but 
  a 
  very 
  

   short 
  time 
  in 
  the 
  water 
  ; 
  it 
  is 
  true 
  that 
  in 
  this 
  case 
  

   the 
  web 
  is 
  probably 
  of 
  use 
  for 
  pushing 
  aside 
  the 
  soil 
  

   in 
  the 
  process 
  of 
  digging. 
  

  

  The 
  following 
  synopsis 
  of 
  the 
  species 
  is 
  based 
  

   entirely 
  on 
  external 
  characters, 
  and 
  applies 
  to 
  both 
  

   sexes. 
  

  

  T. 
  Tongue 
  circular, 
  entire, 
  adherent, 
  or 
  slightly 
  

   free 
  behind 
  ; 
  vomerine 
  teeth 
  behind 
  the 
  level 
  of 
  

   the 
  choanse 
  ; 
  first 
  finger 
  shorter 
  than 
  second 
  

  

  (DlSCOGLOSSIDJl). 
  

  

  