﻿240 
  

  

  G. 
  R. 
  Wieland 
  — 
  Huge 
  Cretaceous 
  Turtles. 
  

  

  entire 
  dental 
  border 
  is 
  peculiar 
  ; 
  firstly, 
  because 
  of 
  the 
  

   decurved 
  premaxillary 
  ; 
  secondly, 
  because 
  of 
  the 
  very 
  slight 
  

   concavity 
  of 
  the 
  vomeral 
  region, 
  and 
  the 
  continuation 
  of 
  the 
  

   dental 
  border 
  of 
  the 
  jugal 
  as 
  a 
  rounded 
  edge, 
  which 
  instead 
  of 
  

   ascending 
  is 
  most 
  depressed 
  at 
  its 
  junction 
  with 
  the 
  quadrato- 
  

   jugal, 
  as 
  will 
  be 
  again 
  noted 
  in 
  the 
  description 
  of 
  the 
  latter 
  

   9 
  elements. 
  

  

  The 
  maxillaries 
  do 
  not 
  rise 
  

   as 
  high 
  relatively 
  to 
  meet 
  the 
  

   prefrontals 
  as 
  is 
  nsual. 
  There 
  

   is 
  in 
  this 
  conformation 
  a 
  sug- 
  

   gestive 
  resemblance 
  to 
  Lyto- 
  

   loma 
  (chelone) 
  longiceps 
  Owen. 
  

   The 
  Jugals. 
  — 
  These 
  elements 
  

   are 
  subtriangular 
  in 
  outline, 
  

   the 
  basal 
  side 
  being 
  longest, 
  

   and 
  extending 
  back 
  to 
  the 
  

   lower 
  extremity 
  of 
  the 
  quad- 
  

   rato- 
  jugal 
  as 
  an 
  un-notched 
  

   nearly 
  straight, 
  somewhat 
  de- 
  

   pressed 
  and 
  rounded 
  border. 
  

   The 
  depression 
  of 
  the 
  jugal 
  is 
  

   quite 
  unique 
  and 
  gives 
  great 
  

   length 
  to 
  the 
  unusual 
  dental 
  

   border 
  thus 
  formed. 
  

  

  With 
  the 
  postfrontal 
  the 
  jugal 
  

  

  Figure 
  2. 
  Archelon 
  isclwros 
  Wieland. 
  £ 
  ±1 
  - 
  • 
  . 
  A 
  • 
  j 
  

  

  Median 
  vertical 
  section 
  through 
  ante- 
  formS 
  the 
  Posterior 
  two-thirds 
  

  

  rior 
  region 
  of 
  skull 
  x{; 
  m, 
  maxillary; 
  Of 
  the 
  orbit, 
  the 
  Orbital 
  border 
  

  

  «, 
  narial 
  opening 
  ; 
  o, 
  orbital 
  boundary 
  ; 
  being 
  distinctly 
  flattened 
  and 
  

  

  Sl^ 
  e 
  -ii?r 
  t0 
  ' 
  n 
  f 
  al; 
  Pi 
  Paktal; 
  Pm 
  ' 
  from 
  2cm 
  hvo 
  *' 
  d 
  posteriorly 
  to 
  

  

  premaxillan 
  r 
  ; 
  v, 
  vomer. 
  n 
  n 
  , 
  ~. 
  , 
  •' 
  , 
  

  

  3*3 
  cm 
  broad 
  anteriorly. 
  Only 
  

   the 
  extreme 
  anterior 
  extension 
  articulates 
  with 
  the 
  palatal, 
  

   making 
  the 
  boundaries 
  those 
  of 
  Thalassoehelys 
  and 
  not 
  like 
  

   those 
  of 
  Dermoehelys. 
  

  

  The 
  Quadrato- 
  jugals 
  (Paraquadrate 
  of 
  Siebenrock 
  12). 
  — 
  

   These 
  bones 
  present 
  exteriorly 
  a 
  large 
  gently 
  convex 
  surface 
  

   of 
  broadly 
  crescentic 
  outline. 
  The 
  concave 
  posterior 
  border 
  

   stands 
  at 
  a 
  right 
  angle 
  to 
  the 
  outer 
  surface 
  and 
  is 
  4 
  cm 
  broad, 
  

   forming 
  a 
  symmetrical 
  surface 
  with 
  the 
  quite 
  similar 
  posterior 
  

   orbital 
  boundary 
  noted 
  above. 
  See 
  fig. 
  1. 
  

  

  The 
  quadrate 
  is 
  fortunately 
  present 
  in 
  the 
  specimen 
  of 
  

   Protostega 
  gigas 
  studied 
  by 
  Case, 
  who 
  thus 
  describes 
  it 
  (5, 
  

   page 
  27) 
  : 
  " 
  The 
  quadrato-jugal 
  of 
  the 
  right 
  side 
  is 
  triangular 
  

   in 
  general 
  outline. 
  The 
  posterior 
  edge 
  is 
  concave 
  and 
  the 
  

   whole 
  bone 
  is 
  convex 
  from 
  above 
  downward. 
  The 
  superior 
  

   edge 
  is 
  narrow, 
  and 
  there 
  is 
  no 
  prolongation 
  of 
  the 
  antero- 
  

   inferior 
  portion 
  as 
  in 
  Dermoehelys 
  (5, 
  PI. 
  Y, 
  fig. 
  7)." 
  

  

  