﻿G. 
  B. 
  Wieland 
  — 
  Huge 
  Cretaceous 
  Turtles. 
  239 
  

  

  by 
  Mr. 
  Hugh 
  Gibb, 
  and 
  now 
  on 
  exhibition 
  in 
  the 
  Museum 
  of 
  

   Yale 
  University. 
  The 
  plate 
  is 
  carefully 
  interpreted 
  in 
  fig. 
  1. 
  

   Still 
  other 
  features 
  are 
  shown 
  in 
  ligs. 
  2 
  and 
  3, 
  which 
  are 
  neces- 
  

   sarily 
  somewhat 
  diagrammatic. 
  

  

  Notwithstanding 
  considerable 
  lateral 
  compression 
  of 
  the 
  

   posterier 
  portions, 
  this 
  skull 
  is 
  an 
  unusually 
  good 
  one, 
  all 
  the 
  

   main 
  details 
  needed 
  for 
  a 
  restoration 
  being 
  well 
  preserved. 
  It 
  

   only 
  fails 
  in 
  the 
  region 
  of 
  the 
  brain 
  cavity 
  and 
  the 
  posterior 
  

   extremity 
  and 
  connections 
  of 
  the 
  vomer. 
  Its 
  description 
  and 
  

   comparison 
  with 
  its 
  nearest 
  known 
  relative 
  and 
  ancestor 
  Pro- 
  

   tostega 
  gigas 
  from 
  the 
  Kansas 
  chalk 
  has 
  been 
  made 
  all 
  the 
  

   more 
  exact 
  and 
  satisfactory 
  by 
  the 
  courtesy 
  of 
  Prof. 
  W. 
  M. 
  

   Wheeler 
  and 
  Dr. 
  E. 
  C. 
  Case, 
  who 
  generously 
  placed 
  in 
  my 
  

   hands 
  for 
  purposes 
  of 
  comparison 
  the 
  exceptionally 
  line 
  mate- 
  

   rial 
  so 
  ably 
  investigated 
  by 
  the 
  latter 
  (5). 
  This 
  represents 
  

   various 
  disarticulated 
  elements 
  of 
  the 
  skull 
  and 
  a 
  line 
  mandible. 
  

   Between 
  the 
  two 
  specimens 
  the 
  skull 
  of 
  these 
  important 
  forms 
  

   of 
  the 
  Cretaceous 
  may 
  now 
  be 
  known 
  with 
  essential 
  complete- 
  

   ness. 
  The 
  description 
  of 
  parts 
  follows. 
  

  

  The 
  Premaxillaries. 
  — 
  These 
  elements 
  are 
  strongly 
  coossitied 
  

   and 
  comparatively 
  narrow 
  laterally, 
  but 
  long 
  and 
  massive. 
  

   The 
  narial 
  border 
  is 
  rounded 
  and 
  horizontal. 
  The 
  dental 
  

   border 
  is 
  posteriorly 
  less 
  developed 
  into 
  a 
  cutting 
  edge 
  than 
  in 
  

   other 
  turtles, 
  but 
  anteriorly 
  runs 
  out 
  into 
  the 
  most 
  strongly 
  

   decurved 
  beak 
  known 
  in 
  any 
  turtle, 
  the 
  aspect 
  being 
  that 
  seen 
  

   in 
  birds 
  of 
  prey. 
  The 
  surface 
  of 
  the 
  beak 
  especially 
  is 
  deeply 
  

   pitted, 
  and 
  in 
  life 
  must 
  have 
  been 
  covered 
  by 
  a 
  horn 
  sheath 
  of 
  

   the 
  relative 
  decurvature 
  and 
  strength 
  of 
  that 
  of 
  the 
  eagle. 
  

   There 
  is 
  only 
  a 
  shallow 
  excavation 
  for 
  the 
  reception 
  of 
  the 
  

   mandibular 
  beak. 
  

  

  The 
  great 
  length 
  and 
  other 
  details 
  are 
  the 
  exact 
  antithesis 
  of 
  

   the 
  short 
  and 
  notched 
  premaxillaries 
  of 
  Dermoohelys 
  with 
  a 
  

   persistent 
  suture. 
  The 
  inner 
  features 
  and 
  union 
  with 
  the 
  

   vomer 
  are 
  shown 
  in 
  tig. 
  2. 
  The 
  boundaries 
  are, 
  in 
  spite 
  of 
  all 
  

   disparities, 
  essentially 
  similar 
  to 
  those 
  seen 
  in 
  Dermochelys. 
  

  

  The 
  Maxillaries. 
  — 
  The 
  general 
  maxillary 
  outline 
  is 
  that 
  of 
  

   a 
  broad 
  Y 
  lying 
  on 
  its 
  side, 
  the 
  fork 
  forming 
  the 
  anterior 
  

   orbital 
  boundary, 
  and 
  the 
  wide 
  base 
  extending 
  forward 
  to 
  an 
  

   unusual 
  distance. 
  Much 
  of 
  the 
  great 
  cranial 
  length 
  is 
  due 
  to 
  

   the 
  elongated 
  maxillaries 
  and 
  premaxillaries. 
  

  

  The 
  narial 
  border 
  is 
  only 
  moderately 
  upcurved 
  to 
  aid 
  in 
  the 
  

   formation 
  of 
  the 
  greatly 
  elongated 
  external 
  nares, 
  which 
  face 
  

   upwards 
  and 
  but 
  slightly 
  forwards, 
  being 
  much 
  more 
  nearly 
  

   horizontal 
  than 
  in 
  most 
  turtles. 
  

  

  The 
  dental 
  border 
  is 
  continued 
  by 
  the 
  maxillary 
  as 
  a 
  low 
  

   cutting 
  edge 
  which 
  soon 
  becomes 
  rounded 
  and 
  continues 
  so 
  to 
  

   junction 
  with 
  the 
  jugal. 
  It 
  should 
  be 
  noted 
  here 
  that 
  the 
  

  

  