﻿440 
  H. 
  G. 
  SEEIEY 
  ON 
  SOME 
  GENERIC 
  MODIFICATIONS 
  

  

  the 
  bone 
  might 
  be 
  more 
  intelligible 
  were 
  it 
  revolved 
  through 
  half 
  

   a 
  circle. 
  

  

  Fig. 
  4. 
  — 
  Pectoral 
  Arch 
  and 
  Humerus 
  of 
  Plesiosaurus, 
  as 
  restored 
  by 
  

   Prof. 
  Owen. 
  

  

  E. 
  Epistemum. 
  S. 
  Scapula. 
  c. 
  Coracoid. 
  H. 
  Humerus. 
  

  

  Prof. 
  Huxley 
  (' 
  Anatomy 
  of 
  Vertebrated 
  Animals 
  ') 
  apparently 
  re- 
  

   gards 
  the 
  Plesiosaurian 
  pectoral 
  arch 
  as 
  a 
  constant 
  quantity, 
  since 
  

   the 
  species 
  are 
  said 
  to 
  differ 
  in 
  little 
  more 
  than 
  the 
  proportions 
  of 
  

   the 
  head 
  to 
  the 
  trunk, 
  and 
  the 
  relative 
  length 
  and 
  degree 
  of 
  exca- 
  

   vation 
  of 
  the 
  centra 
  of 
  the 
  vertebras. 
  The 
  scapula 
  finds 
  its 
  affinities 
  

   in 
  the 
  Lacertilia, 
  the 
  ventral 
  part 
  of 
  the 
  bone 
  in 
  Plesiosaurus 
  being 
  

   supposed 
  to 
  correspond 
  to 
  the 
  glenoid 
  part 
  of 
  the 
  scapula 
  of 
  Iguana, 
  

   while 
  the 
  mass 
  of 
  the 
  Lizard-scapula 
  is 
  supposed 
  to 
  be 
  represented 
  

   by 
  the 
  lateral 
  portion 
  of 
  the 
  scapula 
  of 
  Plesiosaurus. 
  I 
  should 
  not 
  

   attach 
  more 
  than 
  epiphysial 
  importance 
  to 
  the 
  glenoid 
  ossifications 
  

   in 
  Lizards, 
  seeing 
  how 
  largely 
  epiphyses 
  are 
  developed 
  in 
  the 
  order, 
  

   and 
  therefore 
  believe 
  that 
  no 
  part 
  of 
  the 
  Plesiosaurian 
  scapula 
  corre- 
  

   sponds 
  to 
  the 
  glenoid 
  ossification 
  adjoining 
  the 
  scapula 
  and 
  coracoid 
  

   bones 
  in 
  some 
  Lizards. 
  The 
  two 
  chief 
  objections 
  to 
  Prof. 
  Huxley's 
  

   view 
  are, 
  that 
  in 
  Plesiosaurs 
  there 
  is 
  no 
  evidence 
  of 
  more 
  than 
  one 
  

   ossification 
  in 
  the 
  scapula 
  ; 
  while 
  the 
  preglenoid 
  part 
  of 
  the 
  bone 
  in 
  

   Lizards 
  is 
  commonly 
  in 
  intimate 
  relation 
  with 
  the 
  clavicle, 
  which 
  

   on 
  the 
  hypothesis 
  would 
  not 
  be 
  the 
  case 
  in 
  Plesiosaurs. 
  The 
  lateral 
  

   part 
  of 
  the 
  scapula 
  is 
  of 
  such 
  varying 
  size, 
  that 
  I 
  prefer 
  to 
  suppose 
  

   it 
  moulded 
  from 
  the 
  scapula 
  in 
  the 
  several 
  species 
  by 
  muscular 
  

   developmont. 
  

  

  At 
  page 
  210 
  of 
  the 
  same 
  work 
  Prof. 
  Huxley 
  gives 
  a 
  diagram 
  of 
  

   the 
  Plesiosaurian 
  pectoral 
  girdle 
  (see 
  fig. 
  5), 
  based, 
  as 
  I 
  learn 
  by 
  

   letter, 
  on 
  " 
  what 
  he 
  imagines 
  to 
  be 
  sufficient 
  evidence." 
  The 
  chief 
  

   point 
  in 
  which 
  I 
  dissent 
  from 
  that 
  figure 
  is 
  the 
  treatment 
  of 
  the 
  

   interclavicle 
  ; 
  but 
  granting 
  that, 
  as 
  Prof. 
  Huxley 
  remarks, 
  the 
  bone 
  

   is 
  not 
  always 
  perfectly 
  ossified, 
  no 
  specimen 
  hitherto 
  described, 
  or, 
  

   as 
  far 
  as 
  I 
  know, 
  exhibited 
  in 
  any 
  Museum, 
  shows 
  the 
  characters 
  of 
  

   the 
  five-rayed 
  mass 
  named 
  by 
  Prof. 
  Huxley 
  " 
  a, 
  clavicles 
  and 
  inter- 
  

   clavicle 
  ?" 
  (fig. 
  5, 
  J). 
  

  

  