﻿AND 
  AVES 
  OF 
  NORTH 
  AMERICA. 
  115 
  

  

  must 
  have 
  rendered 
  them 
  far 
  less 
  efficient 
  as 
  weapons 
  than 
  the 
  hind 
  feet, 
  in 
  an 
  attack 
  on 
  

   such 
  a 
  creature 
  as 
  Hadrosaurus 
  ; 
  hence 
  perhaps 
  the 
  latter 
  were 
  preferred 
  in 
  inflicting 
  fatal 
  

   wounds. 
  The 
  ornithic 
  type 
  of 
  sacrum 
  elucidated 
  by 
  Prof. 
  Owen, 
  suggests 
  a 
  resemblance 
  

   in 
  the 
  use 
  of 
  the 
  limb." 
  

  

  There 
  were 
  but 
  few 
  animals 
  then 
  living 
  which 
  could 
  afford 
  long 
  pursuit 
  on 
  land, 
  so 
  

  

  \ 
  far 
  as 
  known, 
  excepting 
  among 
  the 
  Dinosauria 
  of 
  that 
  day. 
  The 
  Laelaps 
  had 
  to 
  contend 
  

  

  with 
  hard-shelled 
  turtles 
  or 
  armored 
  crocodiles, 
  or 
  the 
  swift 
  sea-saurians. 
  These 
  it 
  must 
  

  

  capture 
  by 
  sudden 
  movements, 
  as 
  it 
  is 
  not 
  likely 
  that 
  its 
  grasping 
  toes 
  furnished 
  much 
  

  

  natatory 
  power. 
  

  

  The 
  lightness 
  and 
  hollowness 
  of 
  the 
  bones 
  of 
  the 
  Laelaps 
  arrest 
  the 
  attention. 
  This 
  

   is 
  especially 
  true 
  of 
  the 
  long 
  bones 
  of 
  the 
  hind 
  limbs 
  ; 
  those 
  of 
  the 
  fore 
  limbs 
  have 
  a 
  less 
  

   considerable 
  medullary 
  cavity. 
  In 
  this 
  respect 
  they 
  are 
  quite 
  similar 
  to 
  those 
  of 
  Coelo- 
  

   saurus 
  Leidy, 
  of 
  which 
  its 
  describer 
  remarks 
  that 
  " 
  the 
  medullary 
  cavity 
  of 
  the 
  tibia 
  is 
  

   large, 
  and 
  the 
  walls 
  thin 
  and 
  dense," 
  "being 
  intermediate 
  in 
  this 
  respect 
  between 
  the 
  

   characters 
  of 
  the 
  Mammals 
  and 
  Birds." 
  

  

  The 
  mutual 
  flexure, 
  as 
  well 
  as 
  the 
  lightness 
  and 
  strength 
  of 
  the 
  great 
  femur 
  and 
  tibia 
  

   are 
  altogether 
  appropriate 
  to 
  great 
  powers 
  of 
  leaping. 
  The 
  feet 
  must 
  have 
  been 
  elongate, 
  

   whatever 
  the 
  form 
  of 
  the 
  tarsi 
  ; 
  the 
  phalanges, 
  or 
  toe 
  bones 
  were 
  slender, 
  nearly 
  as 
  

   much 
  so 
  relatively 
  as 
  those 
  of 
  an 
  eagle, 
  while 
  the 
  great 
  claws 
  in 
  which 
  they 
  terminated 
  

   were 
  relatively 
  larger 
  and 
  more 
  compressed 
  than 
  in 
  the 
  birds 
  of 
  prey. 
  There 
  was 
  no 
  

   provision 
  for 
  the 
  retractibility 
  observed 
  in 
  the 
  great 
  carnivorous 
  mammalia, 
  but 
  the 
  size 
  

   of 
  the 
  inferior 
  basal 
  tuberosity 
  indicates 
  the 
  insertion 
  of 
  a 
  great 
  tendon 
  of 
  a 
  powerful 
  

   flexor 
  muscle. 
  The 
  slight 
  grooves 
  at 
  the 
  base, 
  and 
  deeper 
  one 
  on 
  each 
  side 
  of 
  the 
  pha- 
  

   lange, 
  indicate 
  the 
  usual 
  horny 
  sheath, 
  which, 
  prolonging 
  the 
  point 
  of 
  the 
  claw, 
  would 
  

   give 
  it 
  a 
  total 
  length 
  of 
  ten 
  inches. 
  

  

  The 
  tail 
  was 
  moderately 
  long, 
  rounded 
  and 
  strong, 
  and 
  not 
  so 
  much 
  a 
  support 
  as 
  capa- 
  

   ble 
  of 
  striking 
  a 
  blow 
  and 
  of 
  throwing 
  an 
  enemy 
  within 
  reach 
  of 
  the 
  kick 
  or 
  grab 
  of 
  the 
  

   terrible 
  hind 
  leg. 
  

  

  The 
  fore 
  limbs 
  must 
  indeed 
  have 
  been 
  of 
  very 
  little 
  use, 
  and 
  it 
  is 
  very 
  difficult 
  to 
  

   imagine 
  an 
  animal 
  both 
  running 
  and 
  seizing 
  the 
  prey 
  it 
  overtakes, 
  with 
  the 
  hind 
  limb. 
  If 
  

   it 
  were 
  not 
  a 
  carrion 
  feeder 
  it 
  must 
  have 
  leaped. 
  We 
  are 
  informed 
  by 
  Hochstetter* 
  that 
  

   the 
  Apteryx 
  leaps 
  with 
  the 
  utmost 
  ease 
  over 
  objects 
  two 
  and 
  three 
  feet 
  in 
  height, 
  that 
  is, 
  

   higher 
  than 
  its 
  head. 
  Huxley 
  suggests 
  that 
  the 
  Compsognathus 
  " 
  hopped 
  " 
  along 
  on 
  its 
  

   hind 
  limbs. 
  The 
  bulk 
  of 
  Laelaps 
  is 
  no 
  objection 
  to 
  its 
  leaping, 
  for 
  the 
  giant 
  extinct 
  kanga- 
  

   roos, 
  Macropus 
  atlas 
  and 
  titan, 
  found 
  in 
  the 
  postpliocene 
  caves 
  of 
  Australia, 
  did 
  not 
  fall 
  far 
  

   short 
  of 
  these 
  reptiles, 
  in 
  this 
  respect. 
  We 
  may 
  add 
  that 
  Laelaps 
  had 
  smaller 
  allies, 
  as 
  

  

  * 
  New 
  Zealand 
  Amer. 
  Trans., 
  181. 
  

  

  