﻿Oi-yiithosaurian 
  Genus 
  Ornitlioclieirus. 
  545 
  

  

  Group 
  B. 
  

  

  J. 
  a. 
  6, 
  4. 
  Proximal 
  end 
  of 
  right 
  Imraerus. 
  Tlie 
  deltoid 
  

   crest 
  lias 
  its 
  origin 
  far 
  below 
  the 
  condyle, 
  and 
  is 
  apparently 
  

   slightly 
  oblique 
  to 
  its 
  long 
  axis. 
  The 
  pneumatic 
  foramen 
  is 
  

   further 
  down 
  the 
  shaft 
  than 
  in 
  J. 
  a. 
  6, 
  26 
  (Group 
  A), 
  and 
  

   there 
  is 
  a 
  ridge 
  on 
  the 
  preaxial 
  moiety 
  of 
  the 
  condyle. 
  The 
  

   condyle 
  is 
  not 
  so 
  crescentic, 
  and 
  therefore 
  the 
  horns 
  splay- 
  

   more 
  outwards 
  and 
  the 
  ulnar 
  crest 
  is 
  moderately 
  developed. 
  

  

  Group 
  C. 
  

  

  The 
  perfect 
  humerus 
  J. 
  a. 
  6, 
  30, 
  whose 
  characters 
  have 
  

   been 
  given 
  by 
  Seeley, 
  is 
  the 
  type. 
  J. 
  a. 
  6, 
  22, 
  23, 
  24, 
  27, 
  28 
  

   are 
  proximal 
  ends 
  exhibiting 
  pneumatic 
  forarainae 
  on 
  the 
  

   ventral 
  surface, 
  and 
  38, 
  39, 
  40, 
  41 
  should 
  also 
  appai^ently 
  

   have 
  been 
  included, 
  although 
  they 
  are 
  too 
  much 
  abraded 
  to 
  

   reveal 
  the 
  pneumatic 
  foramen. 
  

  

  Distal 
  ends. 
  

  

  Group 
  A. 
  

  

  J. 
  fl. 
  6, 
  21 
  & 
  32. 
  Examples 
  belonging 
  to 
  left 
  humeri. 
  

   They 
  are 
  similar 
  to 
  Ornithodesnms 
  latideas, 
  though 
  one-fifth 
  

   smaller 
  in 
  the 
  transverse 
  diameter 
  of 
  the 
  distal 
  articulation, 
  

   and 
  the 
  characters 
  are 
  very 
  weakly 
  developed. 
  The 
  central 
  

   circular 
  cavity 
  and 
  the 
  transverse 
  valley 
  in 
  no. 
  32 
  are 
  tilled 
  

   with 
  phosphate 
  of 
  lime, 
  and 
  thus 
  are 
  not 
  well 
  seen, 
  while 
  in 
  

   No. 
  31 
  these 
  are 
  obscured 
  by 
  the 
  bone 
  being 
  much 
  worn 
  in 
  this 
  

   region 
  and 
  destroyed 
  on 
  the 
  dorsal 
  margin 
  of 
  the 
  median 
  

   pit. 
  The 
  ulnar 
  articulation 
  on 
  each 
  bone 
  is 
  also 
  worn, 
  and 
  

   does 
  not 
  appear 
  to 
  have 
  been 
  as 
  highly 
  developed 
  as 
  in 
  

   Ornithodesmus 
  latidens. 
  Seeley 
  says 
  * 
  that 
  the 
  " 
  mesial 
  

   condyle 
  in 
  this 
  group 
  appears 
  in 
  every 
  case 
  to 
  be 
  an 
  epiphysis 
  

   which 
  is 
  wanting." 
  The 
  narrow 
  ridge 
  on 
  the 
  proximal 
  end 
  

   of 
  the 
  ulna 
  requires 
  a 
  valley 
  to 
  articulate 
  in, 
  and 
  this 
  would 
  

   be 
  impossible 
  if 
  a 
  mesial 
  condyle 
  had 
  been 
  present. 
  

  

  J. 
  a. 
  6, 
  31. 
  This 
  example 
  possesses 
  the 
  same 
  charactei's 
  

   as 
  nos. 
  21 
  and 
  32, 
  although 
  in 
  a 
  very 
  incipient 
  stage. 
  It 
  is 
  

   interesting 
  because 
  the 
  centi'al 
  circular 
  entrance 
  into 
  the 
  

   bone 
  is 
  not 
  present. 
  In 
  that 
  region 
  occurs 
  a 
  basin-shaped 
  

   hollow 
  only. 
  

  

  * 
  H. 
  G. 
  Seeley, 
  ' 
  Ornitbosauria,' 
  1870, 
  p. 
  40. 
  

   Ann. 
  cfc 
  Mag. 
  N. 
  Hist. 
  Ser. 
  8. 
  Vol. 
  xiii. 
  37 
  

  

  