﻿AND 
  AVES 
  OF 
  NORTH 
  AMERICA. 
  171 
  

  

  spine, 
  nearly 
  over 
  the 
  posterior 
  zygapophyses, 
  and 
  vertical 
  to 
  the 
  plane 
  of 
  the 
  centrum. 
  The 
  inferior 
  outline 
  of 
  the 
  

   centrum 
  of 
  this, 
  as 
  of 
  all 
  the 
  other 
  vertebrae, 
  is 
  concave. 
  

  

  Lines. 
  

   Length 
  of 
  centrum, 
  3.75 
  

  

  " 
  top 
  of 
  neural 
  arch, 
  2. 
  

  

  " 
  neural 
  spine, 
  3.2 
  

  

  Depth 
  from 
  anterior 
  zygapophysis, 
  1.75 
  

  

  Width 
  of 
  neural 
  spine, 
  1. 
  

  

  Another 
  fractured 
  dorsal 
  exhibits 
  a 
  broader 
  neural 
  spine, 
  but 
  its 
  form 
  cannot 
  be 
  accurately 
  ascertained; 
  in 
  a 
  

   third 
  its 
  extent 
  is 
  nearly 
  that 
  of 
  a 
  neural 
  arch, 
  and 
  it 
  has 
  considerable 
  longitudinal 
  breadth 
  to 
  its 
  crest. 
  The 
  centrum 
  

   of 
  this 
  vertebra 
  appears 
  to 
  be 
  shorter 
  than 
  in 
  the 
  last, 
  no 
  doubt 
  in 
  harmony 
  with 
  its 
  position 
  as 
  a 
  rib-bearing 
  dorsal. 
  

  

  Lines. 
  

  

  Length 
  of 
  centrum 
  (No. 
  3), 
  3.5 
  

  

  " 
  below 
  posterior 
  zygapophysis, 
  2. 
  

  

  " 
  neural 
  arch, 
  3. 
  

  

  Height 
  of 
  vertebra 
  (top 
  of 
  spine 
  concealed), 
  C. 
  (? 
  f 
  ) 
  

  

  " 
  posterior 
  zygapophysis, 
  2.5 
  

  

  Depth 
  centrum 
  at 
  condyle, 
  1.1 
  

  

  Length 
  centrum 
  (No. 
  15), 
  3.2 
  

  

  Height 
  of 
  vertebra, 
  4 
  6 
  

  

  " 
  to 
  posterior 
  zygapophysis, 
  1.6 
  

  

  The 
  anterior 
  cotylus 
  in 
  this, 
  as 
  in 
  all 
  the 
  other 
  vertebrae, 
  looks 
  partly 
  dowirwards. 
  The 
  superior 
  anterior 
  outline 
  

   of 
  the 
  neural 
  spine 
  is 
  concave, 
  as 
  though 
  the 
  straight 
  margin 
  were 
  cut 
  away 
  to 
  half 
  the 
  depth 
  of 
  the 
  spine. 
  Whether 
  

   this 
  is 
  the 
  natural 
  form, 
  or 
  result 
  of 
  fracture 
  of 
  the 
  matrix, 
  is 
  not 
  readily 
  ascertained; 
  in 
  another 
  the 
  full 
  width 
  is 
  

   carried 
  four-fifths 
  way 
  up 
  to 
  the 
  crest. 
  

  

  Of 
  what 
  are 
  perhaps 
  caudal 
  vertebrae 
  there 
  are 
  profiles 
  of 
  six, 
  mostly 
  with 
  reverses; 
  two 
  are 
  very 
  perfect. 
  In 
  all 
  

   the 
  inferior 
  outline 
  of 
  the 
  centrum 
  it 
  is 
  markedly 
  concave. 
  No. 
  1, 
  the 
  most 
  characteristic, 
  differs 
  from 
  the 
  others 
  in 
  

   possessing 
  a 
  long 
  acuminate 
  process, 
  projecting 
  at 
  an 
  angle 
  of 
  35° 
  with 
  the 
  axis 
  of 
  the 
  centrum 
  immediately 
  below 
  the 
  

   posterior 
  condyle 
  ; 
  or, 
  as 
  the 
  inferior 
  part 
  of 
  the 
  condyle 
  is 
  obscured 
  by 
  it, 
  at 
  the 
  side 
  of 
  it. 
  This 
  may 
  be 
  looked 
  upon 
  

   as 
  a 
  profile 
  of 
  a 
  chevron 
  bone, 
  or 
  as 
  one 
  of 
  a 
  pair 
  of 
  lateral 
  central 
  processes, 
  such 
  as 
  go 
  off 
  anteriorly 
  in 
  Pterosauria, 
  

   Coeciliae, 
  and 
  Amphiumae; 
  or, 
  perhaps 
  less 
  probably, 
  as 
  a 
  posterior 
  hypophysis. 
  That 
  this 
  may 
  be 
  the 
  anterior 
  ex- 
  

   terior 
  extremity, 
  though 
  furnished 
  with 
  the 
  condyle, 
  is 
  rendered 
  more 
  probable 
  by 
  the 
  presence 
  of 
  a 
  short 
  obtuse 
  pro- 
  

   cess 
  immediately 
  upon 
  the 
  column, 
  and 
  which 
  cannot 
  be 
  other 
  than 
  the 
  surspectant 
  zygapophysis. 
  It 
  is, 
  therefore, 
  

   quite 
  possible 
  that 
  this 
  vertebra 
  is 
  opisthocoelian, 
  as 
  Seeley* 
  has 
  pointed 
  out 
  the 
  cervicals 
  of 
  Dimorphodon 
  macronyx 
  

   to 
  be. 
  The 
  neural 
  arch 
  stands 
  only 
  upon 
  the 
  two-thirds 
  of 
  the 
  centrum, 
  next 
  the 
  cotylus 
  bearing 
  extremity, 
  and 
  

   offers 
  the 
  free 
  projection 
  of 
  the 
  despectant 
  zygapophysis 
  appropriate 
  to 
  the 
  opposite 
  extremity 
  of 
  a 
  vertebra, 
  like 
  itself. 
  

   Below 
  this 
  extremity 
  of 
  the 
  centrum 
  is 
  a 
  keel-like 
  zygapophysis 
  of 
  a 
  right 
  angled 
  triangular 
  form, 
  the 
  centrum 
  being 
  

   the 
  hypothenuse. 
  

  

  Lines. 
  

   Length 
  of 
  centrum, 
  3.5 
  

  

  " 
  inferior 
  spine, 
  1.25 
  

  

  Depth 
  at 
  cotylus 
  without 
  zygapophysis, 
  2. 
  

  

  A 
  second 
  and 
  larger 
  vertebra 
  (No. 
  2) 
  of 
  the 
  same 
  type 
  differs 
  in 
  the 
  lack 
  of 
  zygapophysis 
  above 
  the 
  condyle, 
  and 
  

   of 
  the 
  spine 
  below 
  the 
  same. 
  The 
  centrum 
  is 
  prolonged 
  considerably 
  beyond 
  the 
  line 
  of 
  the 
  neural 
  arch; 
  at 
  its 
  oppo- 
  

  

  * 
  Annals 
  Magaz. 
  Nat. 
  Hist., 
  1865. 
  

  

  