﻿446 
  

  

  H. 
  G. 
  SEELET 
  ON 
  SOME 
  GENERIC 
  MODIFICATIONS 
  

  

  coid 
  foramen 
  and 
  the 
  glenoid 
  cavity 
  become 
  united 
  with 
  the 
  cora- 
  

   coids 
  into 
  one 
  bone. 
  Important 
  light 
  is 
  thrown 
  on 
  this 
  pectoral 
  arch 
  

   by 
  an 
  isolated 
  anchylosed 
  scapula 
  and 
  distally 
  imperfect 
  precoraco- 
  

   coracoid 
  bone, 
  also 
  from 
  the 
  Lias, 
  clearly 
  belonging 
  to 
  the 
  same 
  

   genus, 
  though 
  probably 
  referable 
  to 
  another 
  species 
  (fig. 
  10). 
  The 
  

  

  Fig. 
  10. 
  — 
  Left 
  Side 
  of 
  Pectoral 
  Arch 
  of 
  Eretmosaurus. 
  

  

  s. 
  Scapula. 
  

  

  c. 
  Coracoid. 
  

  

  g. 
  Glenoid 
  cavity. 
  

  

  coracoid 
  portion 
  of 
  this 
  mass 
  is 
  extremely 
  thin, 
  but 
  thickens 
  at 
  the 
  

   median 
  line 
  of 
  the 
  body 
  of 
  the 
  animal, 
  as 
  is 
  usual. 
  The 
  articular 
  

   surface 
  for 
  the 
  humerus 
  shows 
  no 
  indication 
  of 
  being 
  formed 
  by 
  

   more 
  than 
  one 
  bone, 
  so 
  perfectly 
  are 
  the 
  scapula 
  and 
  coracoid 
  

   blended. 
  On 
  a 
  line 
  with 
  the 
  anterior 
  margin 
  of 
  the 
  articular 
  sur- 
  

   face, 
  and 
  nearer 
  the 
  median 
  line 
  than 
  the 
  precoracoid 
  foramen, 
  is 
  a 
  

   small 
  vertical 
  perforation, 
  which 
  I 
  suppose 
  to 
  be 
  homologous 
  with 
  

   the 
  foramen 
  similarly 
  placed 
  in 
  the 
  coracoid 
  of 
  Lizards, 
  Crocodiles, 
  

   and 
  many 
  Dinosaurs, 
  and 
  to 
  be 
  similarly 
  definitive 
  of 
  the 
  limits 
  of 
  

   the 
  precoracoid 
  and 
  coracoid 
  elements 
  of 
  the 
  bones, 
  and 
  to 
  indicate 
  

   that 
  in 
  some 
  amphibian 
  ancestral 
  race 
  the 
  precoracoids 
  were 
  as 
  di- 
  

   stinct 
  from 
  the 
  coracoids 
  as 
  they 
  are 
  in 
  the 
  Cape 
  frog 
  {Dactylethra), 
  

   which 
  has 
  a 
  pectoral 
  region 
  not 
  altogether 
  incomparable 
  with 
  that 
  

   of 
  some 
  members 
  of 
  the 
  Plesiosaurian 
  order 
  (see 
  fig. 
  11). 
  The 
  ante- 
  

  

  Fig. 
  11. 
  — 
  Pectoral 
  Arch 
  of 
  Dactylethra. 
  (After 
  W. 
  K. 
  Parker.) 
  

  

  pc. 
  Precoracoid. 
  

  

  c. 
  Coracoid. 
  

  

  rior 
  margin 
  of 
  the 
  precoracoid 
  portion 
  of 
  the 
  bone 
  is 
  truncated 
  in 
  

   the 
  median 
  line, 
  though 
  a 
  suture 
  there 
  extends 
  between 
  it 
  and 
  the 
  

  

  