﻿AND 
  AVES 
  OF 
  NORTH 
  AMERICA. 
  101 
  

  

  the 
  posterior 
  cutting 
  edge 
  being 
  directed 
  outwards. 
  The 
  anterior 
  alveolus 
  is 
  shallower 
  than 
  the 
  second, 
  and 
  this 
  

   shallower 
  than 
  the 
  third, 
  which 
  gives 
  an 
  oblique 
  slope 
  to 
  the 
  fractured 
  margin 
  of 
  the 
  bone, 
  and 
  suggests 
  the 
  applica- 
  

   tion 
  of 
  another 
  skeletal 
  piece. 
  This 
  I 
  suppose 
  to 
  be 
  the 
  premaxillary, 
  as 
  the 
  bone 
  is 
  externally 
  too 
  flat 
  to 
  permit 
  the 
  

   median 
  premaxillary 
  suture 
  to 
  occupy 
  that 
  position. 
  The 
  upper 
  portion 
  may 
  be 
  related 
  to 
  the 
  margin 
  of 
  the 
  nares. 
  

   A 
  series 
  of 
  five 
  foramina 
  extends 
  along 
  the 
  outer 
  face 
  of 
  the 
  bone 
  opposite 
  the 
  middle 
  of 
  the 
  depth 
  of 
  the 
  alveolae. 
  

   The 
  alveola? 
  are 
  directed 
  more 
  anteriorly 
  from 
  behind 
  forwards. 
  

  

  Lines. 
  

   Depth 
  of 
  alveolus, 
  34 
  

  

  Length 
  crown 
  of 
  successional 
  tooth, 
  25 
  

  

  Length 
  piece 
  embracing 
  four 
  alveola;, 
  Gl 
  

  

  Mandible. 
  — 
  One 
  portion 
  from 
  the 
  anterior 
  part 
  of 
  the 
  ramus. 
  The 
  latter 
  measure 
  three 
  inches 
  in 
  depth 
  from 
  the 
  

   outer 
  alveolar 
  border, 
  which 
  is 
  a 
  little 
  more 
  elevated 
  than 
  the 
  internal, 
  and 
  1.5 
  in. 
  in 
  thickness 
  at 
  the 
  fractured 
  edge. 
  

   A 
  longitudinal 
  series 
  of 
  vascular 
  foramina 
  extends 
  along 
  the 
  middle 
  of 
  the 
  external 
  face. 
  The 
  teeth 
  are 
  implanted 
  

   in 
  deep 
  alveola}, 
  and 
  had 
  transversely 
  oval 
  compressed 
  fangs; 
  the 
  sections 
  of 
  the 
  crowns 
  of 
  teeth 
  from 
  different 
  

   portions 
  of 
  the 
  ramus 
  differ. 
  Two 
  from 
  the 
  anterior 
  region 
  are 
  considerably 
  recurved, 
  the 
  concave 
  or 
  posterior 
  edge 
  

   deticulate 
  to 
  the 
  base 
  of 
  the 
  enamel, 
  the 
  anterior 
  aspect 
  minutely 
  serrate, 
  two 
  fifths 
  the 
  length 
  from 
  the 
  tip. 
  Section 
  

   at 
  this 
  point 
  lenticular, 
  lower 
  down 
  the 
  anterior 
  face 
  becomes 
  broader 
  and 
  rounded, 
  giving 
  a 
  rounded 
  cuneiform 
  

   section. 
  Throughout, 
  one 
  face 
  is 
  more 
  convex 
  than 
  the 
  other. 
  A 
  young 
  posterior 
  tooth 
  yet 
  in 
  the 
  alveolus 
  (no. 
  8) 
  

   is 
  less 
  recurved, 
  subacute, 
  and 
  of 
  more 
  lenticular 
  section, 
  having 
  both 
  edges 
  denticulate 
  to 
  the 
  base 
  of 
  the 
  enamel. 
  

   Fangs 
  hollow, 
  the 
  pulp 
  cavity 
  capacious 
  but 
  rapidly 
  diminishing 
  and 
  short; 
  the 
  cast 
  sulphide 
  of 
  iron 
  and 
  marl. 
  

  

  Indies. 
  

  

  No. 
  1; 
  total 
  length 
  (fang 
  broken), 
  2 
  33 
  

  

  length 
  of 
  enamel, 
  1.83 
  

  

  width 
  below, 
  .833 
  

  

  anterior 
  diameter, 
  .433 
  

  

  No. 
  2; 
  length 
  of 
  crown 
  (tip 
  restored), 
  1.875 
  

  

  anterior 
  diameter, 
  . 
  5 
  

  

  No. 
  3; 
  length 
  of 
  crown, 
  2.125 
  

   width 
  at 
  base, 
  .G88 
  

  

  Larger 
  teeth 
  are 
  indicated 
  by 
  fragments. 
  The 
  development 
  of 
  the 
  teeth 
  has 
  apparently 
  proceeded 
  as 
  in 
  Megalo- 
  

   saurus 
  . 
  The 
  development 
  of 
  the 
  dental 
  papilla 
  takes 
  place 
  within 
  a 
  niche 
  of 
  the 
  alveolus, 
  between 
  it 
  and 
  the 
  inner 
  

   mandibular 
  or 
  maxillary 
  wall. 
  Small 
  serate 
  casps 
  are 
  found 
  in 
  this 
  position 
  beneath 
  but 
  a 
  thin 
  stratum 
  of 
  bone. 
  In 
  

   one 
  situation 
  a 
  second 
  successional 
  tooth 
  occupies 
  a 
  position 
  between 
  the 
  primary 
  cusp 
  and 
  the 
  functional 
  tooth, 
  and 
  

   is 
  about 
  intermediate 
  in 
  size 
  between 
  them. 
  These 
  successional 
  teeth 
  then 
  increasing 
  in 
  size, 
  by 
  a 
  horizontal 
  move- 
  

   ment, 
  transverse 
  to 
  the 
  cranial 
  axis, 
  place 
  themselves 
  close 
  to 
  the 
  fangs 
  of 
  the 
  functional 
  teeth, 
  into 
  whose 
  places 
  

   they 
  gradually 
  rise. 
  An 
  absorption 
  of 
  the 
  dental 
  wall 
  probably 
  prepares 
  the 
  older 
  tooth 
  for 
  shedding, 
  at 
  which 
  time 
  

   the 
  apex 
  of 
  the 
  successional 
  tooth 
  is 
  ready 
  for 
  use.* 
  

  

  Vertebra. 
  — 
  No 
  cervical 
  or 
  dorsal 
  vertebra? 
  were 
  preserved 
  ; 
  we 
  have 
  only 
  as 
  yet 
  sacrals, 
  and 
  numerous 
  caudals. 
  

   All 
  are 
  much 
  constricted 
  medially, 
  or 
  hour-glass 
  shaped, 
  the 
  centrum 
  cylindrical 
  in 
  section 
  throughout 
  in 
  most 
  of 
  the 
  

   caudals, 
  the 
  anterior 
  of 
  the 
  latter 
  and 
  the 
  lumbars 
  of 
  deeper 
  vertical 
  than 
  transverse 
  diameter 
  throughout. 
  The 
  

   articular 
  surfaces 
  are 
  moderately 
  shallow 
  biconcave 
  in 
  all, 
  most 
  strongly 
  in 
  the 
  subproximial 
  caudals. 
  The 
  neural 
  

   arches 
  attached 
  by 
  permanent 
  suture, 
  and 
  inferior 
  surfaces 
  for 
  articulation 
  of 
  chevron 
  bones. 
  The 
  caudals 
  offer 
  

   indication 
  of 
  neural 
  spines 
  ; 
  their 
  traces 
  are 
  on 
  the 
  majority 
  low, 
  and 
  of 
  considerable 
  longitudinal 
  extent. 
  Articular 
  

  

  * 
  Deslongchamps 
  figures 
  a 
  tooth 
  as 
  doubtfully 
  bjlonging 
  to 
  Poecilopleurum. 
  It 
  resembles 
  that 
  of 
  a 
  Crocodilian, 
  and 
  probably 
  belongs 
  to 
  a 
  species 
  of 
  that 
  

   subclass. 
  He 
  states 
  that 
  Megalosaurus-like 
  teeth 
  occur 
  in 
  the 
  strata 
  in 
  which 
  Poecilopleurum 
  was 
  found. 
  There 
  is 
  now 
  much 
  reason 
  to 
  believe 
  that 
  the 
  latter 
  

   are 
  the 
  true 
  teeth 
  of 
  the 
  genus 
  in 
  question. 
  

  

  AMERI. 
  PHILOSO. 
  SOC. 
  — 
  VOL. 
  XIV. 
  26 
  

  

  