﻿AND 
  AYES 
  OF 
  NORTH 
  AMERICA. 
  203 
  

  

  In. 
  

  

  Proximal 
  width 
  cup, 
  3.43 
  

  

  " 
  depth 
  " 
  3.23 
  

  

  Caudal 
  without 
  diap. 
  No. 
  1, 
  length, 
  1.6 
  

  

  " 
  " 
  " 
  " 
  depth 
  cup, 
  2.65 
  

  

  " 
  " 
  " 
  " 
  width 
  " 
  2.6 
  

  

  " 
  " 
  " 
  " 
  height 
  neural 
  canal, 
  .4 
  

  

  " 
  " 
  " 
  " 
  antero-posterior 
  width 
  neural 
  spine, 
  . 
  8 
  

  

  Caudal 
  do.. 
  No. 
  2, 
  length, 
  1.2 
  

  

  " 
  " 
  " 
  depth 
  cup, 
  2.15 
  

  

  " 
  " 
  " 
  width 
  " 
  1.86 
  

  

  " 
  " 
  " 
  " 
  neural 
  sp. 
  (antero-posterior), 
  1.07 
  

  

  Caudal 
  do., 
  distal; 
  length, 
  .5 
  

  

  " 
  " 
  " 
  depth 
  cup, 
  .85 
  

  

  " 
  " 
  " 
  width 
  " 
  .64 
  

  

  Caudal 
  do., 
  distal; 
  diameter 
  antero-posterior, 
  of 
  neural 
  spine, 
  .40 
  

  

  The 
  points 
  of 
  attachment 
  of 
  the 
  chevron 
  bones 
  on 
  the 
  distal 
  vertebrae 
  are 
  strongly 
  marked 
  pits; 
  on 
  the 
  anteiior, 
  the 
  

   anterior 
  margins 
  of 
  the 
  pits 
  are 
  raised 
  and 
  continuous 
  with 
  the 
  chevrons. 
  

  

  The 
  muzzle 
  presents 
  the 
  usual 
  characters 
  of 
  the 
  large 
  Mosasauroids, 
  but 
  adds 
  a 
  peculiarity 
  in 
  the 
  prolongation 
  of 
  

   the 
  premaxillary 
  bone 
  into 
  a 
  cylindric 
  mass 
  forming 
  an 
  obtuse 
  beak 
  beyond 
  the 
  premaxillary 
  teeth. 
  The 
  bone 
  is 
  nar- 
  

   rowed 
  anteriorly, 
  and 
  does 
  not 
  descend 
  regularly 
  as 
  in 
  Mosasaurus 
  sp., 
  but 
  continues 
  to 
  its 
  abrupt 
  and 
  narrowed 
  termi- 
  

   nation 
  described. 
  The 
  extremity 
  is 
  deeper 
  than 
  wide. 
  Immediately 
  in 
  front 
  of 
  and 
  between 
  the 
  anterior 
  premaxillary 
  

   teeth, 
  a 
  short 
  acuminate 
  projection 
  interrupts 
  the 
  surface, 
  and 
  in 
  front 
  of 
  this, 
  a 
  transverse 
  depression. 
  Above, 
  the 
  

   surface 
  becomes 
  flattened, 
  and 
  presents 
  two 
  shallow 
  longitudinal 
  depressions 
  continuous 
  with 
  the 
  nostrils. 
  Where 
  the 
  

   pi 
  - 
  emaxillary 
  rather 
  suddenly 
  contracts 
  into 
  its 
  spine, 
  it 
  is 
  materially 
  wider 
  than 
  the 
  maxillary 
  on 
  each 
  side 
  of 
  it; 
  in 
  M. 
  

   missuriensis 
  it 
  is 
  narrower, 
  according 
  to 
  Goldfuss. 
  The 
  maxillary 
  border 
  of 
  the 
  nares 
  is 
  rather 
  suddenly 
  concave 
  at 
  the 
  

   anterior 
  extremity 
  of 
  the 
  nares, 
  narrowing 
  the 
  maxillaries; 
  the 
  latter 
  gradually 
  widen 
  by 
  the 
  expansion 
  of 
  their 
  inner 
  

   margins. 
  

  

  No 
  part 
  of 
  the 
  frontals 
  is 
  preserved, 
  but 
  a 
  considerable 
  part 
  of 
  the 
  left 
  pre-frontal 
  remains. 
  It 
  unites 
  by 
  a 
  very 
  coarse 
  

   overlapping 
  suture 
  with 
  the 
  maxillary, 
  whose 
  outline 
  forms 
  an 
  irregular 
  chevron 
  with 
  the 
  apex 
  pointing 
  forwards 
  in 
  

   the 
  middle 
  of 
  the 
  maxillary 
  bone. 
  This, 
  it 
  will 
  be 
  seen, 
  is 
  very 
  different 
  from 
  the 
  form 
  given 
  by 
  Goldfuss 
  in 
  the 
  M. 
  

   missuriensis, 
  where 
  the 
  most 
  anterior 
  point 
  of 
  the 
  suture 
  is 
  on 
  the 
  nareal 
  margin. 
  The 
  external 
  margin 
  of 
  the 
  bone 
  

   behind 
  is 
  contracted 
  considerably 
  within 
  the 
  maxillary 
  border, 
  previous 
  to 
  its 
  outward 
  extension 
  towards 
  the 
  orbit. 
  

   This 
  is 
  much 
  less 
  marked 
  in 
  the 
  Clidastes 
  propython, 
  but 
  is 
  distinct 
  in 
  M. 
  missuriensis. 
  

  

  The 
  maxillo-premaxillary 
  suture 
  gradually 
  descends 
  to 
  the 
  alveolar 
  border 
  to 
  the 
  extremity 
  of 
  the 
  maxillary 
  bone, 
  

   where 
  it 
  descends 
  abruptly, 
  forming 
  an 
  interlocking 
  sriture 
  quite 
  different 
  from 
  that 
  squamosal 
  type 
  already 
  observed 
  in 
  

   other 
  species 
  of 
  the 
  order. 
  The 
  length 
  of 
  the 
  premaxillary 
  anterior 
  to 
  this 
  point, 
  is 
  three-fourths 
  the 
  length 
  of 
  the 
  

   same 
  to 
  the 
  beginning 
  of 
  the 
  nares. 
  

  

  The 
  number 
  o 
  teeth 
  on 
  the 
  maxillary 
  bone 
  was 
  probably 
  thirteen; 
  twelve 
  alveola 
  and 
  bases 
  remain, 
  and 
  one 
  is 
  

   added 
  in 
  the 
  position 
  of 
  the 
  posterior 
  tooth 
  of 
  M. 
  missuriensis, 
  if 
  such 
  existed; 
  this 
  may 
  be 
  questioned 
  in 
  consideration 
  

   of 
  the 
  small 
  number 
  of 
  mandibular 
  teeth. 
  Premaxillary 
  teeth 
  two 
  on 
  each 
  side, 
  the 
  anterior 
  with 
  bases 
  separated 
  only 
  

   by 
  a 
  groove. 
  Throughout 
  the 
  whole 
  series 
  the 
  bases 
  of 
  the 
  teeth 
  are 
  considerably 
  more 
  exposed 
  on 
  the 
  inner 
  than 
  the 
  

   outer 
  side. 
  

  

  The 
  crowns 
  are 
  everywhere 
  sub-cylindric 
  at 
  the 
  base, 
  the 
  inner 
  face 
  more 
  convex 
  than 
  the 
  outer. 
  Posteriorly 
  there 
  

   is 
  a 
  posterior 
  cutting 
  ridge, 
  as 
  well'as 
  a 
  marked 
  anterior 
  one, 
  both 
  minutely 
  crenulate, 
  but 
  the 
  former 
  disappears 
  till 
  in 
  

   the 
  anterior 
  teeth 
  there 
  is 
  only 
  an 
  anterior 
  edge, 
  the 
  posterior 
  face 
  being 
  convex 
  and 
  continuous 
  with 
  the 
  inner. 
  There 
  

   is 
  a 
  trace 
  of 
  cutting 
  edge 
  on 
  the 
  outer 
  portion 
  of 
  the 
  extremity 
  of 
  the 
  crown 
  in 
  the 
  most 
  anterior 
  teeth. 
  The 
  anterior 
  

   ridge 
  remains 
  very 
  strongly 
  marked. 
  The 
  surface 
  is 
  quite 
  rough 
  with 
  longitudinal 
  ribs, 
  of 
  which 
  eight 
  may 
  be 
  counted 
  

  

  