﻿232 
  

  

  ME. 
  E. 
  LYDEKEEE 
  OX 
  EEMAIXS 
  OF 
  EOCEXE 
  AXE 
  MESOZOIC 
  

  

  the 
  accompanying 
  woodcut, 
  and 
  is 
  somewhat 
  smaller 
  than 
  the 
  example 
  

   in 
  Mr. 
  Jesson's 
  collection, 
  is 
  taken 
  as 
  the 
  type 
  of 
  the 
  species. 
  From 
  

  

  Fig. 
  1. 
  — 
  Lateral 
  and 
  Oral 
  Aspects 
  of 
  the 
  Mandibular 
  Symphysis 
  of 
  

   Chelone 
  Jessoni; 
  from 
  the 
  Cambridge 
  Greensand. 
  (j 
  nat. 
  size.) 
  

  

  <;M--M 
  

  

  their 
  extremely 
  large 
  size, 
  I 
  take 
  it 
  that 
  these 
  specimens 
  are 
  pro- 
  

   bably 
  referable 
  to 
  marine 
  Turtles, 
  and 
  do 
  not 
  belong 
  to 
  Bhinochelys, 
  

   which 
  we 
  have 
  no 
  evidence 
  to 
  show 
  attained 
  anything 
  like 
  these 
  

   dimensions. 
  Assuming 
  that 
  I 
  am 
  right 
  in 
  this 
  respect, 
  the 
  specimen 
  

   may 
  be 
  described 
  as 
  follows 
  : 
  — 
  The 
  symphysis 
  is 
  considerably 
  elon- 
  

   gated, 
  and 
  the 
  palatal 
  surface 
  deeply 
  concave, 
  with 
  a 
  distinct 
  median 
  

   ridge, 
  tending 
  to 
  form 
  a 
  tubercle 
  at 
  its 
  posterior 
  extremity. 
  Infe- 
  

   riorly 
  the 
  symphysis 
  is 
  deep, 
  narrow, 
  and 
  highly 
  convex. 
  In 
  all 
  

   these 
  respects 
  the 
  specimens 
  agree 
  very 
  closely 
  with 
  the 
  mandible 
  of 
  

   the 
  Hawksbill 
  ; 
  and 
  since 
  the 
  palate 
  of 
  the 
  above-mentioned 
  cranium 
  

   likewise 
  approximates 
  to 
  that 
  of 
  the 
  latter, 
  there 
  is 
  a 
  strong 
  pre- 
  

   sumption 
  that 
  both 
  the 
  cranium 
  and 
  mandibles 
  may 
  belong 
  to 
  one 
  

   and 
  the 
  same 
  species*. 
  The 
  present 
  type 
  of 
  mandible, 
  it 
  may 
  be 
  

   added, 
  is 
  quite 
  different 
  from 
  that 
  of 
  Chelone 
  Hoffmanni 
  of 
  the 
  

   Maastricht 
  Cretaceous. 
  It 
  remains 
  to 
  consider 
  whether 
  these 
  spe- 
  

   cimens 
  can 
  be 
  referred 
  to 
  any 
  Cretaceous 
  species 
  already 
  described. 
  

   Now 
  it 
  appears 
  to 
  me, 
  judging 
  from 
  the 
  Ichthyopterygia 
  and 
  Sauro- 
  

   pterygia, 
  that 
  a 
  considerable 
  number 
  of 
  the 
  reptiles 
  of 
  the 
  Cambridge 
  

  

  * 
  The 
  presence 
  of 
  oral 
  ridges 
  in 
  one 
  species 
  of 
  Thalassochelys 
  renders 
  it 
  

   possible 
  that 
  the 
  present 
  form 
  belongs 
  to 
  that 
  genus. 
  

  

  