﻿AND 
  AVES 
  OF. 
  NORTH 
  AMERICA. 
  

  

  187 
  

  

  covered. 
  In 
  the 
  following 
  cuts 
  the 
  outlines 
  of 
  the 
  proximal 
  extremities 
  of 
  the 
  ossa 
  quad- 
  

   rata 
  are 
  given, 
  with 
  sections 
  at 
  a 
  little 
  below 
  the 
  middle 
  of 
  the 
  length 
  of 
  each. 
  

  

  Fig. 
  48. 
  

  

  1. 
  Mosasaurus 
  maximus, 
  Cope. 
  

  

  2. 
  " 
  dekayi, 
  Bronn. 
  

  

  3. 
  ■" 
  depressus, 
  Cope. 
  

  

  4. 
  Platecarpus 
  tympaniticus, 
  Cope. 
  

  

  5. 
  Liodon 
  validus, 
  Cope, 
  position 
  the 
  reverse 
  of 
  the 
  others. 
  

  

  6. 
  Clidastes 
  propython, 
  Cope. 
  

  

  One-third 
  natural 
  size. 
  The 
  great 
  alae 
  in 
  2a 
  and 
  5a 
  are 
  

   unknown. 
  

  

  6, 
  the 
  great 
  ala 
  ; 
  c, 
  the 
  meatus 
  auditorius 
  ; 
  d, 
  the 
  posterior 
  decurved 
  extremity 
  of 
  the 
  proximal 
  end 
  of 
  the 
  os 
  

   quadratum. 
  

  

  Dotted 
  lines 
  crossing 
  the 
  outlines 
  indicate 
  fractures 
  and 
  restorations 
  outside 
  of 
  

   them. 
  In 
  figs. 
  4a 
  and 
  6a 
  the 
  dotted 
  lines 
  indicate 
  the 
  bridging 
  of 
  the 
  meatus 
  by 
  the 
  

   proximal 
  extremity 
  of 
  the 
  bone. 
  The 
  great 
  ala 
  is 
  lost 
  in 
  our 
  specimens 
  both 
  of 
  M. 
  dekayi 
  

   and 
  M. 
  depressus. 
  The 
  marked 
  peculiarity 
  of 
  M. 
  depressus 
  is 
  shown 
  above 
  ; 
  also, 
  the 
  

   great 
  decurvature 
  of 
  the 
  superior 
  extremity 
  around 
  and 
  behind 
  the 
  meatus 
  in 
  the 
  Platecar- 
  

   pus 
  and 
  the 
  Clidastes. 
  In 
  them 
  it 
  descends 
  below 
  opposite 
  the 
  point 
  of 
  section, 
  and 
  is 
  

   therefore 
  divided 
  by 
  the 
  line 
  from 
  which 
  the 
  outline 
  is 
  taken. 
  In 
  Mosasaurus 
  minor, 
  

   gracilis, 
  and 
  brumbyi, 
  the 
  quadrate 
  bone 
  is 
  unknown. 
  

  

  Vertebrcs. 
  The 
  outlines 
  of 
  the 
  lateral 
  elements 
  of 
  the 
  atlas 
  of 
  five 
  species, 
  including 
  

   that 
  of 
  the 
  giganteus, 
  (from 
  Camper) 
  indicate 
  corresponding 
  differences, 
  which 
  are 
  most 
  

   distinct 
  on 
  the 
  internal 
  faces. 
  In 
  M. 
  giganteus, 
  M. 
  depressus, 
  and 
  M. 
  dekayi 
  there 
  is 
  

   a 
  facet 
  for 
  articulation 
  with 
  the 
  centrum, 
  just 
  below 
  the 
  anterior 
  facet. 
  In 
  order 
  to 
  ac- 
  

   commodate 
  this, 
  the 
  inferior 
  ala 
  ceases 
  behind 
  the 
  anterior 
  facet 
  in 
  the 
  last 
  two 
  species, 
  

   or 
  is 
  only 
  developed 
  at 
  the 
  posterior 
  part 
  of 
  the 
  element 
  in 
  the 
  European 
  animal. 
  In 
  the 
  

   M. 
  maximus, 
  on 
  the 
  contrary, 
  this 
  ala 
  is 
  prolonged 
  to, 
  and 
  even 
  beyond 
  the 
  anterior 
  or 
  

  

  