﻿AND 
  AVES 
  OF 
  NORTH 
  AMERICA. 
  61 
  

  

  is 
  perhaps 
  a 
  posterior 
  dorsal. 
  It 
  is 
  but 
  slightly 
  curved, 
  has 
  a 
  vertically 
  broad 
  oval 
  section 
  proximally, 
  and 
  a 
  depressed 
  

   trigonal 
  one 
  distally; 
  there 
  is 
  little 
  trace 
  of 
  a 
  medullary 
  cavity. 
  

  

  M. 
  31. 
  

  

  Length, 
  0.23 
  Vertical 
  diameter 
  at 
  distal 
  third, 
  0.014 
  

  

  Do. 
  from 
  head 
  to 
  tubercle, 
  0.03 
  Transverse 
  do., 
  0.155. 
  

  

  I 
  find 
  no 
  abdominal 
  ribs, 
  such 
  as 
  are 
  abundant 
  in 
  the 
  North 
  Carolina 
  specimen 
  described 
  on 
  a 
  preceding 
  page. 
  

  

  This 
  species 
  has 
  been 
  distinguished 
  from 
  B. 
  priscus 
  by 
  the 
  form 
  of 
  its 
  caudal 
  vertebrae. 
  The 
  measurements 
  given 
  

   by 
  Emmons 
  and 
  Leidy, 
  of 
  the 
  other 
  species, 
  differ 
  in 
  the 
  greater 
  elongation 
  of 
  the 
  vertebral 
  centra. 
  The 
  length 
  of 
  

   the 
  latter 
  is 
  in 
  each 
  case 
  greater 
  than 
  the 
  width 
  of 
  the 
  articular 
  face, 
  instead 
  of 
  less. 
  They 
  are 
  also 
  smaller 
  in 
  all 
  

   their 
  dimensions. 
  We 
  shall 
  not 
  go 
  very 
  far 
  wrong 
  in 
  estimating 
  the 
  length 
  of 
  this 
  species 
  on 
  the 
  basis 
  of 
  the 
  gavial 
  

   of 
  the 
  Ganges, 
  as 
  furnished 
  by 
  Cuvier. 
  This 
  would 
  give 
  to 
  the 
  Belodon 
  lepturus 
  a 
  length 
  of 
  about 
  ten 
  feet, 
  and 
  a 
  

   habit 
  stouter 
  than 
  that 
  of 
  the 
  Crocodiles 
  of 
  the 
  present 
  day. 
  

  

  This 
  species 
  was 
  discovered 
  by 
  Chas. 
  M. 
  Wheatley, 
  proprietor 
  of 
  the 
  lead 
  and 
  zinc 
  mines 
  at 
  Phoenixville, 
  Penna. 
  

   He 
  obtained 
  the 
  remains 
  from 
  the 
  "Bone 
  bed" 
  of 
  the 
  Trias, 
  where 
  exposed 
  by 
  the 
  Phoenixville 
  Tunnel 
  of 
  the 
  Read- 
  

   ing 
  Railroad. 
  This 
  stratum 
  is, 
  according 
  to 
  Wheatley, 
  6 
  ft. 
  6 
  in. 
  from 
  the 
  top 
  of 
  the 
  series; 
  53 
  ft. 
  6 
  in. 
  lower 
  down 
  

   is 
  a 
  stratum 
  rich 
  in 
  plants 
  and 
  Saurian 
  remains, 
  and 
  95 
  ft. 
  deeper 
  occur 
  bituminous 
  shales 
  with 
  caprolites 
  and 
  bones. 
  

  

  CROCODILIA. 
  

  

  The 
  constitution 
  of 
  the 
  cranium 
  in 
  this 
  order 
  is 
  very 
  characteristic 
  and 
  peculiar. 
  The 
  

   basal 
  cranial 
  bones 
  are 
  forced 
  backwards, 
  so 
  that 
  they 
  occupy 
  a 
  more 
  or 
  less 
  vertical 
  posi- 
  

   tion, 
  and 
  the 
  sphenoid 
  is 
  almost 
  concealed 
  in 
  many. 
  The 
  quadratum 
  is 
  immoveably 
  

   embraced 
  by 
  the 
  exoccipital, 
  prootic 
  and 
  opisthotic. 
  The 
  pubes 
  do 
  not 
  enter 
  into 
  the 
  

   walls 
  of 
  the 
  acetabulum 
  as 
  in 
  Mammalia 
  and 
  Peptilia, 
  but 
  originate 
  from 
  the 
  inferior 
  

   pelvic 
  arch. 
  They 
  form 
  no 
  common 
  suture, 
  but 
  extend 
  sub-longitudinally, 
  thus 
  differing 
  

   from 
  pubes 
  generally. 
  The 
  latter 
  relation 
  of 
  true 
  pubes 
  occurs 
  among 
  Reptiles 
  only 
  in 
  

   Chelys, 
  Pelomedusa 
  galeata, 
  and 
  Sternothserus, 
  among 
  the 
  Chelouia, 
  and 
  in 
  Pterosauria. 
  

   An 
  anterior 
  process 
  from 
  the 
  ischium 
  occupies 
  the 
  usual 
  position 
  of 
  the 
  origin 
  of 
  the 
  

   pubis, 
  as 
  a 
  support 
  for 
  the 
  latter. 
  

  

  There 
  are 
  at 
  least 
  two 
  well 
  marked 
  types 
  in 
  the 
  class, 
  denned 
  as 
  follows: 
  

   Vertebra? 
  procoelian, 
  i. 
  e. 
  with 
  anterior 
  cup 
  and 
  posterior 
  ball; 
  the 
  sphenoid 
  bone 
  

   little 
  visible 
  on 
  the 
  base 
  of 
  cranium. 
  

  

  PROCOELI. 
  

  

  Vertebrae 
  concave 
  or 
  nearly 
  plane 
  at 
  both 
  extremities 
  ; 
  sphenoid 
  bone 
  with 
  larger 
  and 
  

   more 
  horizontal 
  exposure 
  on 
  base 
  of 
  cranium. 
  

  

  AMPHICOELI. 
  

  

  The 
  only 
  genus 
  of 
  Amphicceli 
  known 
  in 
  this 
  country 
  is 
  Hyposaurus 
  ; 
  the 
  Procoelian 
  

  

  genera 
  are 
  the 
  following 
  : 
  

  

  A 
  The 
  teeth 
  composed 
  of 
  several 
  enclosed 
  cones 
  of 
  dentine. 
  

  

  « 
  The 
  cervical 
  vertebrae 
  with 
  very 
  rudimental 
  or 
  split 
  hypapophyscs. 
  

  

  A 
  large 
  fossa 
  or 
  foramen 
  issuing 
  between 
  the 
  prefrontal 
  and 
  lachrymal 
  bones 
  of 
  the 
  

  

  face 
  ; 
  muzzle 
  long, 
  slender, 
  teeth 
  equal. 
  

  

  THORACOSAURUS. 
  

   AMERI. 
  PH1LOSO. 
  SOC. 
  — 
  VOL. 
  XIV. 
  16 
  

  

  