﻿OF 
  THE 
  PLESIOSAURIAN 
  PECTOKAL 
  ARCH. 
  441 
  

  

  Fig. 
  5. 
  — 
  Pectoral 
  Arcli 
  of 
  Plesiosaurus, 
  as 
  restored 
  by 
  Prof. 
  Huxley. 
  

  

  s. 
  Scapula. 
  /. 
  Interclavicle 
  and 
  clavicles, 
  g. 
  Glenoid 
  cavity, 
  c. 
  Coraeoid. 
  

  

  Another 
  interpretation 
  lately 
  given 
  is 
  that 
  of 
  Prof. 
  E. 
  D. 
  Cope, 
  

   who, 
  in 
  his 
  splendid 
  memoir 
  " 
  On 
  the 
  Extinct 
  Eeptilia 
  &c. 
  of 
  North 
  

   America" 
  (Trans. 
  Am. 
  Phil. 
  Soc, 
  vol. 
  xiv. 
  pt. 
  1. 
  p. 
  51, 
  pi. 
  2), 
  conjec- 
  

   tures 
  that 
  the 
  bones 
  which 
  I 
  have 
  here 
  named 
  scapulae 
  shoidd 
  be 
  called 
  

   " 
  clavicles 
  or 
  procoracoids 
  ; 
  " 
  and 
  consequently, 
  in 
  restoring 
  the 
  skele- 
  

   ton, 
  an 
  imaginary 
  scapula 
  is 
  introduced, 
  which 
  he 
  supposes 
  should 
  ex- 
  

   tend 
  dorsally 
  over 
  the 
  ribs 
  after 
  the 
  pattern 
  of 
  Prof. 
  Owen's 
  diagram. 
  

   Prof. 
  Cope's 
  genus 
  Elasmosaurus, 
  in 
  which 
  this 
  structure 
  is 
  repre- 
  

   sented 
  in 
  a 
  restoration 
  (pi. 
  1), 
  is 
  formed 
  so 
  entirely 
  on 
  the 
  Plesio- 
  

   saurian 
  type, 
  that 
  I 
  think 
  the 
  laws 
  of 
  osteological 
  correlation 
  warrant 
  

   us 
  in 
  affirming 
  that, 
  since 
  no 
  trace 
  of 
  such 
  structure 
  exists 
  in 
  any 
  

   European 
  Plesiosaur, 
  no 
  such 
  bone 
  will 
  ever 
  be 
  found 
  in 
  Elasmosaurus. 
  

   The 
  above 
  hypothesis 
  alone 
  could 
  have 
  induced 
  that 
  distinguished 
  

   naturalist 
  to 
  name 
  the 
  scapulae 
  clavicles 
  ; 
  it 
  may 
  also 
  have 
  induced 
  

   him 
  to 
  draw 
  the 
  limits 
  of 
  the 
  glenoid 
  cavities 
  for 
  the 
  humeri 
  entirely 
  

   in 
  the 
  coraeoid 
  bones, 
  excluding 
  therefrom 
  these 
  elements 
  of 
  the 
  

   scapular 
  arch, 
  because 
  it 
  would 
  be 
  contrary 
  to 
  analogy 
  for 
  them 
  to 
  

   enter 
  into 
  the 
  glenoid 
  cavity 
  if 
  the 
  scapulas 
  are 
  supposed 
  to 
  be 
  

   clavicles. 
  I 
  am 
  convinced 
  that 
  clavicles 
  form 
  no 
  part 
  of 
  the 
  ossified 
  

   mass 
  figured 
  by 
  Prof. 
  Cope. 
  If 
  it 
  were 
  asked 
  what 
  becomes 
  of 
  the 
  

   clavicles 
  ? 
  the 
  same 
  question 
  might 
  be 
  repeated 
  with 
  regard 
  to 
  those 
  

   bones 
  in 
  Crocodiles 
  ; 
  and 
  if 
  the 
  so-called 
  clavicles 
  of 
  Chelonians 
  are, 
  

   as 
  I 
  believe, 
  only 
  potential 
  representatives 
  of 
  the 
  precoracoids, 
  there 
  

   would 
  be 
  no 
  need 
  to 
  account 
  for 
  clavicular 
  bones, 
  even 
  to 
  complete 
  

   the 
  osteological 
  analogy 
  with 
  the 
  chelonian 
  pectoral 
  arch. 
  If 
  Mr. 
  

   Parker's 
  nomenclature 
  were 
  accepted, 
  we 
  should 
  be 
  led, 
  starting 
  with 
  

   a 
  chelonian 
  comparison, 
  to 
  look 
  for 
  the 
  clavicles 
  rather 
  in 
  relation 
  

   with 
  the 
  interclavicle 
  than 
  with 
  the 
  scapulas. 
  

  

  Professor 
  Phillips, 
  whose 
  loss 
  we 
  have 
  lately 
  had 
  to 
  deplore, 
  ap- 
  

   pears, 
  in 
  his 
  ' 
  Geology 
  of 
  Oxford,' 
  to 
  have 
  mistaken 
  the 
  bones 
  of 
  the 
  

   pectoral 
  arch 
  in 
  Plesiosaurus 
  for 
  those 
  of 
  the 
  pelvic 
  arch 
  : 
  bones 
  

   which 
  have 
  all 
  the 
  characters 
  of 
  coracoids 
  are 
  named 
  pubic 
  bones, 
  

   while 
  the 
  scapula 
  is 
  identified 
  with 
  the 
  ischium. 
  These 
  determina- 
  

   tions 
  seem 
  to 
  me 
  attributable 
  to 
  the 
  occurrence 
  in 
  the 
  Oxford 
  Clay 
  

   of 
  unsuspected 
  generic 
  modifications, 
  and 
  to 
  a 
  Teleosaurian 
  theory 
  of 
  

  

  Q. 
  J. 
  G. 
  S. 
  No. 
  120. 
  2 
  i 
  

  

  