﻿AND 
  AYES 
  OF 
  NORTH 
  AMERICA. 
  149 
  

  

  size 
  ; 
  but 
  their 
  centres 
  are 
  distant 
  from 
  the 
  end 
  of 
  the 
  muzzle 
  (measured 
  axially) 
  mere 
  than 
  

   one-third 
  the 
  total 
  length 
  of 
  the 
  cranium. 
  

  

  The 
  descending 
  portion 
  of 
  the 
  pre-frontal 
  is 
  very 
  wide, 
  and 
  equal 
  to 
  the 
  width 
  of 
  the 
  

   maxillary 
  outside 
  the 
  lachrymal 
  foramen 
  ; 
  the 
  latter 
  is 
  small. 
  Internally, 
  the 
  columns 
  of 
  

   the 
  prefrontals 
  converge 
  below 
  to 
  nearly 
  an 
  acute 
  angle, 
  and 
  are 
  directed 
  forwards 
  along 
  

   the 
  vomer. 
  They 
  restrict 
  the 
  nasal 
  meatus 
  extensively, 
  leaving 
  its 
  diameter 
  less 
  than 
  that 
  

   of 
  the 
  columns. 
  On 
  the 
  muzzle 
  the 
  pre-frontals 
  have 
  but 
  a 
  short 
  common 
  suture, 
  admit- 
  

   ting 
  the 
  frontal 
  far 
  between 
  them. 
  The 
  internal 
  nostrils 
  have 
  a 
  diameter 
  each 
  side 
  the 
  

   septum 
  equal 
  to 
  that 
  between 
  the 
  pre-frontals. 
  

  

  ETTCLASTES 
  PLATYOPS. 
  Cope. 
  

  

  Premaxillaries 
  narrow, 
  rounded 
  in 
  front; 
  maxillary 
  outline, 
  nearly 
  straight 
  to 
  below 
  anterior 
  rim 
  of 
  orbits, 
  

   where 
  the 
  breadth 
  of 
  the 
  muzzle 
  is 
  4 
  inches, 
  length 
  to 
  end 
  of 
  muzzle 
  only 
  2. 
  Plane 
  from 
  top 
  of 
  prefrontals 
  to 
  maxillary 
  

   margin 
  straight, 
  oblique 
  maxillary 
  margin 
  with 
  a 
  gentle 
  sigmoid 
  flexure; 
  Squamosal 
  much 
  expanded 
  below 
  and 
  behind 
  

   orbits. 
  Frontal 
  region 
  flat, 
  parietal 
  rising 
  behind; 
  nasal 
  meatus 
  subquadrate, 
  slightly 
  narrowed 
  below, 
  its 
  palatal 
  fora- 
  

   men 
  with 
  a 
  free 
  lateral 
  osseous 
  margin. 
  Alveolar 
  ridge 
  divergent, 
  little 
  projecting 
  above 
  the 
  oblique 
  surface; 
  the 
  

   latter 
  is 
  most 
  concave 
  behind 
  on 
  each 
  side 
  of 
  the 
  vomer, 
  presents 
  no 
  ridges, 
  and 
  few 
  nutritious 
  foramina. 
  Line 
  of 
  

   common 
  suture 
  of 
  o. 
  o. 
  maxillaria 
  in 
  front 
  of 
  vomer, 
  in 
  a 
  sulcus. 
  Palatines 
  cuneiform 
  with 
  everted 
  margins 
  posteri- 
  

   orly, 
  latter 
  most 
  elevated 
  on 
  each 
  side 
  the 
  small 
  choanal 
  opening, 
  which 
  is 
  bounded 
  in 
  front 
  by 
  the 
  projecting 
  posterior 
  

   knob 
  of 
  the 
  vomer. 
  The 
  maxillaries 
  are 
  very 
  massive, 
  and 
  underlie 
  more 
  than 
  two-thirds 
  the 
  area 
  of 
  the 
  orbits; 
  they 
  

   receive 
  a 
  very 
  extensive 
  descending 
  portion 
  of 
  the 
  prefrontals, 
  their 
  union 
  extending 
  so 
  far 
  towards 
  the 
  median 
  line 
  

   as 
  to 
  leave 
  but 
  a 
  narrow 
  nasal 
  meatus. 
  This 
  offers 
  a 
  powerful 
  resistant 
  face 
  to 
  the 
  motion 
  of 
  the 
  mandibles. 
  The 
  

   posterior 
  orbital 
  margin 
  is 
  .75 
  inch 
  in 
  thickness, 
  and 
  is 
  at 
  right 
  angles 
  to 
  its 
  alveolar 
  margin. 
  Pterygoids 
  almost 
  

   entirely 
  broken 
  away. 
  The 
  following 
  measurements 
  will 
  furnish 
  the 
  best 
  data 
  for 
  a 
  comprehension 
  of 
  the 
  form 
  in 
  

   detail. 
  

  

  Total 
  length 
  cranium, 
  

   Breadth 
  behind 
  orbits, 
  

  

  " 
  between 
  poster, 
  margins 
  orbits, 
  

   Least 
  interorbital 
  width, 
  

   Width 
  of 
  nasal 
  meatus, 
  

   Depth 
  premaxillaries, 
  

  

  " 
  maxillary 
  at 
  middle 
  orbit, 
  

  

  " 
  squamosal 
  at 
  zygomatic 
  arch, 
  

   Length 
  naso-prefroutals, 
  

  

  " 
  " 
  " 
  common 
  suture, 
  

  

  " 
  common 
  suture 
  frontals, 
  

  

  " 
  from 
  anterior 
  margin 
  orbit 
  to 
  nasal 
  meatus, 
  

  

  " 
  " 
  premaxillary 
  margin 
  to 
  end 
  vomer, 
  

  

  Width 
  posterior 
  nares 
  together, 
  

  

  " 
  palatine 
  bone 
  opposite 
  end 
  of 
  vomer, 
  

  

  " 
  vomer 
  near 
  anterior 
  extremity, 
  

   Greatest 
  diameter 
  of 
  orbit, 
  

   Least 
  " 
  " 
  

  

  AMERI. 
  PHILOSO. 
  SOC. 
  — 
  VOT,. 
  XIV. 
  38 
  

  

  In. 
  

  

  Lin. 
  

  

  11 
  

  

  

  8 
  

  

  6. 
  

  

  5 
  

  

  2.5 
  

  

  2 
  

  

  2,5 
  

  

  1 
  

  

  2.5 
  

  

  1 
  

  

  1. 
  

  

  1 
  

  

  3.5 
  

  

  2 
  

  

  2. 
  

  

  2 
  

  

  3. 
  

  

  

  6.2 
  

  

  2 
  

  

  4. 
  

  

  

  11. 
  

  

  3 
  

  

  0. 
  

  

  1 
  

  

  1.5 
  

  

  

  .9 
  

  

  

  .7 
  

  

  2 
  

  

  .6 
  

  

  