﻿AND 
  AVES 
  OF 
  NORTH 
  AMERICA. 
  97 
  

  

  separated 
  by 
  a 
  concave 
  margin 
  from 
  a 
  larger 
  portion 
  at 
  right 
  angles 
  to 
  the 
  shaft. 
  The 
  

   latter 
  bears 
  an 
  oblique 
  surface 
  for 
  fixed 
  articulation 
  at 
  its 
  extremity. 
  

  

  In 
  Megadactylus,* 
  the 
  distal 
  portions 
  of 
  the 
  ischia 
  are 
  united 
  on 
  the 
  median 
  line 
  for 
  a 
  

   considerable 
  distance, 
  and 
  are 
  styloid 
  in 
  form. 
  This 
  portion 
  is 
  evidently 
  distal, 
  from 
  the 
  

   lack 
  of 
  articular 
  faces 
  and 
  the 
  divergence 
  and 
  flattening 
  of 
  the 
  other 
  extremities. 
  They 
  

   also 
  resemble 
  the 
  distal 
  extremities 
  in 
  Compsognathus. 
  In 
  Clepsysaurus, 
  the 
  shaft 
  and 
  di- 
  

   lated 
  extremity 
  are 
  both 
  preserved. 
  The 
  former 
  resembles 
  that 
  of 
  Megadactylus, 
  the 
  latter 
  

   that 
  of 
  Hadrosaurus 
  in 
  some 
  degree. 
  If 
  the 
  shaft 
  be 
  posterior, 
  the 
  other 
  extremity 
  is 
  an- 
  

   terior, 
  and 
  the 
  larger 
  dilatation 
  extending 
  at 
  an 
  angle 
  to 
  the 
  shaft 
  supports, 
  no 
  doubt, 
  the 
  

   iliac 
  articulation. 
  The 
  trihedral 
  shaft 
  indicates 
  a 
  median 
  line 
  of 
  junction. 
  In 
  Hadrosau- 
  

   rus 
  no 
  part 
  of 
  the 
  shaft 
  presents 
  a 
  face 
  for 
  contact 
  with 
  that 
  of 
  the 
  other 
  side, 
  while 
  in 
  

   Lselaps 
  such 
  face 
  is 
  very 
  distinct 
  and 
  elongate. 
  From 
  the 
  above, 
  I 
  suppose 
  that 
  the 
  larger 
  

   extension 
  of 
  the 
  ischium 
  is 
  superior 
  and 
  bears 
  the 
  iliac 
  articulation, 
  that 
  the 
  concave 
  an- 
  

   terior 
  outline 
  is 
  that 
  bounding 
  the 
  acetabulum, 
  and 
  that 
  the 
  lower 
  dilatation 
  was 
  in 
  con- 
  

   tact 
  with 
  but 
  not 
  united 
  to 
  the 
  pubis. 
  This 
  is 
  the 
  more 
  probable, 
  since 
  it 
  agrees 
  nearly 
  

   with 
  the 
  arrangement 
  in 
  Iguanodon, 
  as 
  pointed 
  out 
  by 
  Huxley.t 
  It 
  cannot 
  be 
  denied, 
  how- 
  

   ever, 
  that 
  the 
  supposed 
  iliac 
  articulation 
  in 
  the 
  ischium 
  in 
  Hadrosaurus, 
  bears 
  a 
  remark- 
  

   able 
  similarity 
  to 
  the 
  median 
  suture 
  presented 
  by 
  the 
  union 
  of 
  the 
  two 
  supposed 
  ischia 
  on 
  

   the 
  middle 
  line 
  below 
  and 
  distally, 
  as 
  in 
  the 
  pubes 
  of 
  Struthio. 
  In 
  that 
  case, 
  they 
  would 
  

   be 
  pubes. 
  In 
  a 
  posterior 
  direction 
  and 
  median 
  approximation 
  it 
  will 
  agree 
  also 
  with 
  the 
  

   known 
  pelvic 
  elements 
  of 
  an 
  interesting 
  Saurian 
  described 
  by 
  Von 
  Meyer 
  (Palaeonto- 
  

   graphica) 
  from 
  the 
  Wealden 
  of 
  Germany, 
  the 
  Stenopelix 
  valdensis. 
  No 
  attempt 
  has 
  been 
  

   made, 
  so 
  far 
  as 
  I 
  am 
  aware, 
  to 
  refer 
  this 
  animal 
  to 
  its 
  place. 
  It 
  appears 
  to 
  me 
  in 
  its 
  ver- 
  

   tebral 
  and 
  pelvic 
  features 
  to 
  be 
  a 
  small 
  Dinosaur 
  allied 
  to 
  Scelidosaurus 
  Owen. 
  The 
  

   ischia, 
  however, 
  are 
  remarkably 
  prolonged 
  posteriorly, 
  and 
  find 
  a 
  parallel 
  in 
  Compsog- 
  

   nathus 
  Wagn. 
  

  

  Believing 
  them 
  to 
  be 
  ischia, 
  the 
  inferior 
  pelvic 
  arches 
  of 
  Hadrosaurus 
  were 
  light 
  and 
  

   slender, 
  the 
  ischia 
  parallel 
  and 
  light, 
  and 
  entirely 
  incapable 
  of 
  supporting 
  the 
  Aveight 
  of 
  

   the 
  animal, 
  as 
  was 
  done 
  by 
  Megadactylus. 
  The 
  tail 
  was 
  no 
  doubt 
  the 
  great 
  support 
  when 
  

   the 
  head 
  was 
  elevated. 
  

  

  * 
  The 
  large 
  pneumatic 
  foramina 
  in 
  the 
  vertebrae 
  of 
  this 
  genus, 
  together 
  with 
  those 
  seen 
  in 
  the 
  sacrum 
  of 
  Lselaps, 
  

   explain 
  the 
  character 
  of 
  similar 
  vertebra 
  described 
  as 
  os 
  quadratum 
  of 
  Iguanodon 
  by 
  Mantell 
  and 
  Owen, 
  and 
  sacrals 
  

   of 
  Hadrosaurus 
  by 
  Leidy. 
  I 
  regard 
  the 
  latter 
  as 
  indicative 
  of 
  a 
  new 
  genus 
  allied 
  to 
  the 
  Goniopoda. 
  

  

  f 
  Opportunity 
  of 
  reviewing 
  this 
  part 
  of 
  my 
  essay 
  having 
  offered, 
  I 
  must 
  point 
  out 
  the 
  confirmatory 
  evidence 
  I 
  

   have 
  derived 
  from 
  Prof. 
  Huxley's 
  recent 
  explanation 
  of 
  the 
  structure 
  of 
  Hypsilophodon, 
  with 
  regard 
  to 
  my 
  determin- 
  

   ation 
  of 
  the 
  pubes 
  in 
  Hadrosaurus. 
  He 
  proves 
  conclusively 
  its 
  posterior 
  direction, 
  which 
  view 
  I 
  adopt 
  for 
  Hadrosau- 
  

   rus, 
  contrary 
  to 
  my 
  former 
  supposition. 
  

  

  AMERI. 
  PHILOSO. 
  SOC. 
  — 
  VOT,. 
  XIV. 
  '25 
  

  

  