﻿INTERMEDIATE 
  BETWEEN 
  BIRDS 
  AND 
  REPTILES. 
  15 
  

  

  affords, 
  we 
  need 
  no 
  longer 
  be 
  doubtful 
  as 
  to 
  the 
  origin 
  of 
  the 
  many 
  

   bipedal 
  tracks 
  which 
  occur 
  in 
  the 
  Trias 
  and 
  upwards. 
  

  

  Some 
  are 
  very 
  probably 
  the 
  " 
  spoor 
  " 
  of 
  Struthious 
  birds 
  which 
  

   may 
  have 
  existed 
  fully 
  as 
  far 
  back 
  as 
  the 
  beginning 
  of 
  the 
  Secondary 
  

   Period; 
  but 
  most 
  are, 
  no 
  doubt, 
  due 
  to 
  the 
  bipedal 
  habit 
  of 
  our 
  

   Secondary 
  reptiles, 
  a 
  peculiarity 
  still 
  maintained 
  by 
  the 
  Australian 
  

   Chlamydosaurus. 
  

  

  Discussion. 
  

  

  Mr. 
  Seeley 
  thought 
  that 
  the 
  footprints 
  on 
  the 
  slab 
  cited 
  in 
  the 
  

   paper 
  had 
  been 
  produced 
  by 
  some 
  saurian, 
  such 
  as 
  a 
  Pterodactyle, 
  

   the 
  fore 
  limbs 
  of 
  which 
  were 
  wider 
  apart 
  than 
  its 
  hind 
  limbs, 
  rather 
  

   than 
  by 
  Compsognathus. 
  If 
  the 
  foot-track 
  had 
  been 
  due 
  to 
  a 
  saurian 
  

   walking 
  on 
  its 
  hind 
  legs 
  only, 
  he 
  thought 
  that 
  the 
  principal 
  im- 
  

   pressions 
  must 
  of 
  necessity 
  have 
  been 
  nearer 
  together. 
  He 
  disputed 
  

   the 
  correctness 
  of 
  the 
  term 
  " 
  adaptive 
  modification 
  " 
  as 
  applied 
  to 
  

   the 
  air-cavities 
  in 
  bones. 
  He 
  was 
  inclined 
  to 
  regard 
  the 
  Pterodactyle 
  

   as 
  more 
  closely 
  allied 
  to 
  birds 
  than 
  did 
  the 
  author 
  of 
  the 
  paper. 
  

   The 
  condition 
  of 
  the 
  carpus, 
  as 
  well 
  as 
  the 
  tarsus, 
  in 
  these 
  reptiles 
  

   showed 
  their 
  ornithic 
  affinities. 
  He 
  cited 
  jerboas, 
  kangaroos, 
  and 
  

   other 
  forms, 
  in 
  which 
  the 
  hind 
  legs 
  were 
  mainly 
  used 
  for 
  pro- 
  

   gression, 
  but 
  in 
  which 
  the 
  sacrum 
  and 
  other 
  bones 
  were 
  not 
  modified, 
  

   as 
  instances 
  calculated 
  to 
  inspire 
  caution 
  in 
  connecting 
  the 
  mode 
  of 
  

   progression 
  with 
  structure. 
  

  

  Mr. 
  Hijlke 
  could 
  not 
  regard 
  the 
  tracks 
  as 
  those 
  of 
  a 
  Pterodactyle, 
  

   as 
  the 
  inner 
  marks 
  were 
  much 
  less 
  distinct 
  than 
  the 
  outer, 
  and 
  would 
  

   therefore 
  hardly 
  be 
  due 
  to 
  the 
  hinder 
  limbs, 
  on 
  which 
  the 
  weight 
  

   would 
  mainly 
  fall. 
  

  

  Mr. 
  Blanford 
  agreed 
  with 
  Mr. 
  Seeley 
  that 
  the 
  mere 
  fact 
  of 
  the 
  

   Chlamydosaurus 
  walking 
  on 
  its 
  hind 
  legs 
  did 
  not 
  suffice 
  to 
  prove 
  any 
  

   affinity 
  with 
  Dinosaurians. 
  

  

  Mr. 
  "Woodward, 
  in 
  reply, 
  stated 
  that 
  the 
  two 
  points 
  on 
  which 
  

   he 
  had 
  mainly 
  founded 
  the 
  paper 
  were: 
  — 
  1st, 
  the 
  occurrence 
  of 
  

   footprints 
  in 
  the 
  Solenhofen 
  limestone, 
  characteristic 
  of 
  a 
  bipedal 
  

   progression 
  of 
  some 
  saurian, 
  which 
  had, 
  moreover, 
  used 
  its 
  tail 
  from 
  

   time 
  to 
  time 
  to 
  give 
  it 
  a 
  forward 
  impetus 
  ; 
  and 
  2ndly, 
  the 
  method 
  

   of 
  walking 
  of 
  Chlamydosaurus. 
  With 
  regard 
  to 
  animals 
  thus 
  pro- 
  

   gressing, 
  he 
  was 
  not 
  prepared 
  to 
  accept 
  the 
  view 
  that 
  there 
  was 
  no 
  

   corresponding 
  modification 
  in 
  structure. 
  

  

  