﻿AND 
  AVES 
  OF 
  NORTH 
  AMERICA. 
  122-E 
  

  

  at 
  first 
  horizontally, 
  then 
  with 
  a 
  gradual 
  approach 
  to 
  vertically. 
  Like 
  the 
  other 
  bones, 
  

   they 
  are 
  pneumatic 
  and 
  thin 
  walled 
  proximally 
  ; 
  at 
  their 
  medial 
  portion 
  they 
  contain 
  very 
  

   light 
  spongy 
  cancelli. 
  

  

  As 
  compared 
  with 
  Compsognathus 
  the 
  caudal 
  vertebrae 
  are 
  very 
  much 
  shorter 
  and 
  

   deeper 
  : 
  the 
  extremities 
  are 
  stouter 
  and 
  more 
  robust 
  ; 
  the 
  metatarsi 
  and 
  phalanges 
  with 
  

   ungues 
  being 
  shorter 
  and 
  thicker. 
  

  

  That 
  animals 
  of 
  this 
  genus 
  made 
  some 
  of 
  the 
  tracks 
  similar 
  to 
  those 
  of 
  birds 
  in 
  the 
  

   red 
  sandstones 
  of 
  the 
  Valley 
  of 
  the 
  Connecticut, 
  there 
  can 
  be 
  no 
  doubt. 
  It 
  furthermore 
  

   explains 
  some 
  problematical 
  impressions 
  which 
  are 
  occasionally 
  found 
  with 
  them. 
  Tracks 
  

   of 
  an 
  animal 
  resting 
  in 
  a 
  plantigrade 
  position, 
  as 
  indicated 
  by 
  the 
  moulds 
  of 
  two 
  long 
  par- 
  

   allel 
  metatarsi, 
  each 
  terminated 
  by 
  three 
  toes, 
  are 
  accompanied 
  by 
  a 
  peculiar 
  bilobate, 
  

   transversely 
  oval 
  mark 
  on 
  the 
  middle* 
  line, 
  some 
  distance 
  behind 
  the 
  heels. 
  

  

  Prof. 
  Hitchcock 
  states 
  that 
  it 
  appears 
  to 
  be 
  the 
  impression 
  of 
  a 
  short 
  stiff 
  tail. 
  The 
  

   present 
  specimen 
  shows 
  clearly 
  that 
  it 
  was 
  made 
  by 
  the 
  obtuse 
  extremities 
  of 
  the 
  ischia. 
  

   The 
  saurian 
  squatted 
  down, 
  resting 
  on 
  its 
  styloid 
  ischia 
  as 
  the 
  third 
  leg 
  of 
  a 
  tripod 
  of 
  

   which 
  the 
  anterior 
  pair 
  was 
  represented 
  by 
  the 
  hinder 
  legs. 
  Prof. 
  O. 
  C. 
  Marsh 
  informs 
  

   me 
  that 
  in 
  the 
  museum 
  of 
  Yale 
  College, 
  a 
  slab 
  exhibiting 
  impressions 
  similar 
  to 
  the 
  above, 
  

   shows 
  the 
  impressions 
  of 
  the 
  anterior 
  feet 
  also, 
  which 
  were 
  put 
  to 
  the 
  ground 
  in 
  the 
  act 
  

   of 
  rising 
  or 
  sitting, 
  or 
  perhaps 
  reached 
  to 
  it, 
  while 
  the 
  animal 
  was 
  squatting, 
  as 
  do 
  those 
  

   of 
  carnivorous 
  Mammalia. 
  

  

  The 
  tracks 
  of 
  many 
  of 
  the 
  animals 
  discovered 
  by 
  Hitchcock 
  are 
  plantigrade. 
  That 
  

   they 
  could 
  not 
  have 
  walked 
  like 
  the 
  plantigrade 
  mammal, 
  is 
  sufficiently 
  evident 
  from 
  the 
  

   length 
  of 
  the 
  metatarsal 
  elements, 
  which 
  would 
  necessitate 
  a 
  constant 
  contraction 
  of 
  the 
  

   tibialis 
  anticus 
  muscle, 
  or 
  peculiar 
  arrangement 
  of 
  the 
  tarsal 
  bones, 
  for 
  its 
  support. 
  The 
  

   latter 
  does 
  not 
  appear 
  to 
  have 
  existed, 
  and 
  the 
  former 
  is 
  so 
  very 
  improbable, 
  that, 
  in 
  con- 
  

   nection 
  with 
  the 
  pneumatic 
  structure 
  of 
  the 
  bones, 
  there 
  is 
  abundant 
  reason 
  to 
  suppose 
  

   that 
  they 
  progressed 
  by 
  leaps, 
  and 
  assumed 
  the 
  plantigrade 
  position 
  when 
  at 
  rest. 
  

  

  No 
  portion 
  of 
  the 
  cranium 
  or 
  dentition 
  of 
  this 
  genus 
  has 
  been 
  preserved. 
  The 
  large 
  

   stout 
  hooked 
  claws 
  of 
  the 
  fore 
  foot 
  would 
  indicate 
  a 
  more 
  or 
  less 
  carnivorous 
  diet. 
  

  

  The 
  Connecticut 
  Sandstones 
  have 
  been 
  regarded 
  as 
  Triassic, 
  which 
  the 
  lower 
  portions 
  

   of 
  them 
  undoubtedly 
  are, 
  and 
  similar 
  to 
  the 
  German 
  Keuper 
  in 
  the 
  presence 
  of 
  Labyrin- 
  

   thodonts, 
  Thecodonts 
  and 
  Dinosauria 
  in 
  Massachusetts, 
  Pennsylvania 
  and 
  North 
  Carolina. 
  

  

  MEGADACTYLXJS 
  POLYZELUS, 
  Hitchcock. 
  

  

  Loc. 
  Cit. 
  p. 
  39, 
  1865. 
  Iclmology 
  of 
  Massachusetts, 
  p. 
  186, 
  1858. 
  Tab. 
  IX, 
  fig. 
  6 
  (Right 
  fore 
  foot). 
  

   This 
  species 
  was 
  about 
  the 
  size 
  of 
  an 
  ordinary 
  hound. 
  The 
  surfaces 
  of 
  the 
  vertebrae 
  are 
  smooth, 
  and 
  do 
  not 
  dis- 
  

   play 
  any 
  sculpture. 
  Their 
  dimensions 
  are 
  as 
  follows: 
  

  

  Lines. 
  

  

  Antero-posterior 
  length 
  median 
  caudal, 
  10.1 
  

  

  Depth 
  articular 
  face, 
  11.4 
  

  

  