﻿518 
  J. 
  W. 
  HTJLKE 
  ON 
  A 
  REPTILIAN 
  TIBIA 
  AND 
  HUMERUS 
  

  

  Mr. 
  Fox 
  (he. 
  cit.) 
  described 
  the 
  tibia 
  and 
  fibula 
  of 
  Polacanihus 
  

   as 
  being 
  13 
  inches 
  long, 
  with 
  broad 
  ends, 
  like 
  those 
  of 
  Hylceosaurus, 
  

   the 
  diameters 
  of 
  the 
  distal 
  end 
  7g 
  and 
  3| 
  inches. 
  I 
  am 
  not 
  certain 
  

   whether 
  the 
  larger 
  of 
  these 
  latter 
  numbers 
  applies 
  to 
  the 
  breadth 
  of 
  

   the 
  tibia 
  alone, 
  or 
  includes 
  the 
  still 
  connected 
  fibula, 
  and 
  also 
  whether 
  

   13 
  inches 
  is 
  the 
  length 
  of 
  the 
  tibia, 
  or 
  of 
  this 
  with 
  its 
  lower 
  epiphysis 
  

   or 
  astragalus. 
  The 
  extensive 
  ossification 
  of 
  the 
  tendons 
  made 
  it 
  

   probable 
  that 
  the 
  skeleton 
  was 
  that 
  of 
  a 
  fully 
  grown 
  individual. 
  

   Mr. 
  Fox 
  has 
  verbally 
  informed 
  me 
  that 
  the 
  bones 
  of 
  his 
  Polacanihus 
  

   have 
  a 
  coarse 
  texture, 
  and 
  that 
  the 
  femur 
  is 
  devoid 
  of 
  a 
  medullary 
  

   canal. 
  The 
  impression 
  which 
  I 
  retain 
  from 
  a 
  cursory 
  view 
  of 
  Mr. 
  

   Fox's 
  tibia 
  two 
  years 
  ago 
  is 
  of 
  a 
  much 
  less 
  bulky 
  bone 
  than 
  this 
  

   specimen. 
  

  

  The 
  tibia 
  of 
  Hylceosaurus 
  obtained 
  by 
  Dr. 
  Mantell 
  at 
  Bolney, 
  now 
  

   in 
  the 
  British 
  Museum, 
  probably 
  represents 
  the 
  size 
  of 
  the 
  adult 
  

   shin-bone 
  of 
  this 
  Saurian, 
  if 
  it 
  actually 
  formed 
  part 
  of 
  the 
  same 
  

   skeleton 
  with 
  the 
  associated 
  scapulas 
  ; 
  for 
  these 
  (if 
  their 
  much 
  larger 
  

   size, 
  greater 
  massiveness, 
  and 
  stronger 
  features 
  than 
  those 
  in 
  the 
  

   well-known 
  Tilgate- 
  forest 
  slab 
  are 
  trustworthy 
  criteria) 
  very 
  likely 
  

   belonged 
  to 
  an 
  old 
  fully 
  grown 
  individual. 
  Its 
  length 
  is 
  the 
  same 
  

   as 
  that 
  of 
  Dr. 
  Wilkins's 
  specimen. 
  Its 
  proximal 
  end 
  is 
  similarly 
  

   massive, 
  and 
  its 
  distal 
  end 
  is 
  as 
  remarkably 
  expanded 
  ; 
  the 
  shaft 
  also 
  

   is 
  strongly 
  twisted. 
  The 
  condyles 
  are 
  better 
  marked, 
  and 
  the 
  lower 
  

   end, 
  owing 
  to 
  the 
  disassociation 
  of 
  the 
  astragalus, 
  has 
  the 
  usual 
  Di- 
  

   nosaurian 
  notch 
  instead 
  of 
  the 
  distal 
  trochlea 
  of 
  Dr. 
  WiBiins's 
  bone. 
  

   With 
  these 
  close 
  resemblances 
  I 
  prefer 
  to 
  refer 
  this 
  tibia 
  to 
  the 
  

   same 
  genus, 
  though 
  there 
  are 
  differences 
  of 
  detail 
  which 
  may 
  

   possibly 
  denote 
  another 
  species 
  than 
  Mantell's, 
  possibly 
  also 
  may 
  

   merely 
  be 
  the 
  expression 
  of 
  differences 
  of 
  age 
  or 
  sex. 
  

  

  Humerus 
  (PL 
  XXXI. 
  figs. 
  3 
  & 
  4). 
  — 
  The 
  bone 
  which 
  I 
  regard 
  as 
  a 
  

   left 
  humerus 
  shows 
  in 
  an 
  extreme 
  degree 
  the 
  dwarfing 
  of 
  the 
  shaft, 
  

   the 
  expansion 
  of 
  the 
  extremities, 
  and 
  the 
  massiveness 
  relatively 
  to 
  

   length 
  exhibited 
  by 
  the 
  tibia. 
  The 
  total 
  length 
  is 
  16-5 
  inches, 
  the 
  

   breadth 
  of 
  the 
  proximal 
  end 
  8 
  inches, 
  and 
  that 
  of 
  the 
  distal 
  end 
  

   rather 
  under 
  7 
  inches. 
  The 
  shaft 
  is 
  as 
  short 
  as 
  that 
  of 
  the 
  tibia. 
  

   The 
  girth 
  of 
  the 
  proximal 
  end 
  is 
  20 
  inches, 
  that 
  of 
  the 
  distal 
  end 
  is 
  

   18*5 
  inches, 
  and 
  that 
  of 
  the 
  shaft 
  9 
  inches. 
  The 
  proximal 
  border, 
  

   very 
  thick 
  and 
  rounded, 
  swells 
  out 
  at 
  about 
  3 
  inches 
  distance 
  from 
  

   its 
  ulnar 
  end, 
  and 
  assumes 
  a 
  roughly 
  trigonal 
  convex 
  form, 
  the 
  outer 
  

   limit 
  of 
  which 
  falls 
  where 
  the 
  proximal 
  and 
  radial 
  borders 
  meet. 
  

   The 
  base 
  of 
  this 
  sessile 
  articular 
  caput 
  falls 
  in 
  the 
  ventral 
  lip 
  of 
  the 
  

   proximal 
  border 
  ; 
  and 
  its 
  rounded 
  dorsal 
  apex 
  marks 
  the 
  stoutest 
  

   part 
  of 
  the 
  border, 
  where 
  its 
  thickness 
  reaches 
  3' 
  6 
  inches. 
  The 
  

   radial 
  border, 
  at 
  first 
  thinner 
  than 
  the 
  proximal, 
  descends 
  straight 
  

   for 
  the 
  space 
  of 
  3 
  inches, 
  and 
  then 
  expands 
  into 
  a 
  knob-like 
  swelling, 
  

   from 
  which 
  it 
  abruptly 
  declines, 
  ending 
  in 
  a 
  ridge 
  which 
  is 
  lost 
  on 
  

   the 
  ventral 
  or 
  anterior 
  surface 
  of 
  the 
  short 
  and 
  slender 
  shaft 
  above 
  

   the 
  radial 
  tuberosity. 
  The 
  ulnar 
  or 
  posterior 
  border 
  is 
  strongly 
  

   concave. 
  The 
  ventral 
  or 
  anterior 
  surface 
  of 
  the 
  expanded 
  proximal 
  

   part 
  is 
  very 
  hollow 
  transversely, 
  having 
  the 
  shape 
  of 
  a 
  wide 
  trough. 
  

  

  