﻿236 
  ME. 
  E. 
  LYDEKKEE 
  ON 
  EEMAINS 
  OE 
  EOCENE 
  AND 
  MESOZOIC 
  

  

  assumption 
  that 
  the 
  humerus 
  and 
  mandible 
  belong 
  to 
  the 
  same 
  form, 
  

   to 
  refer 
  them 
  to 
  Lytoloma. 
  This 
  view 
  is 
  in 
  harmony 
  with 
  that 
  of 
  

   M. 
  Dollo, 
  who 
  refers 
  a 
  very 
  similar 
  mandible 
  from 
  the 
  Chalk, 
  

   figured 
  by 
  Sir 
  R. 
  Owen 
  in 
  his 
  ' 
  Cretaceous 
  Reptilia,' 
  pt. 
  i. 
  pi. 
  vii.A, 
  

   fig. 
  4, 
  to 
  this 
  genus 
  (.Euclastes) 
  *. 
  

  

  With 
  regard 
  to 
  specific 
  distinction, 
  the 
  pointed 
  posterior 
  end 
  of 
  

   the 
  carapace 
  of 
  Chelone 
  Benstedi 
  is 
  different 
  from 
  that 
  of 
  the 
  Eocene 
  

   species 
  of 
  Lytoloma, 
  in 
  which 
  the 
  carapace 
  is 
  rounded 
  behind 
  ; 
  so 
  

   that 
  the 
  presumption 
  is 
  that 
  the 
  Greensand 
  form 
  does 
  not 
  belong 
  to 
  

   that 
  species. 
  Under 
  these 
  circumstances 
  I 
  propose 
  the 
  name 
  Lyto- 
  

   loma 
  cantabrigiense 
  for 
  the 
  latter, 
  taking 
  the 
  mandible 
  as 
  the 
  type. 
  

  

  It 
  is 
  possible 
  that 
  in 
  this 
  form 
  and 
  L. 
  trigoniceps 
  of 
  the 
  Brackles- 
  

   ham 
  Beds 
  we 
  have 
  species 
  differing 
  somewhat 
  from 
  the 
  typical 
  Lower 
  

   Eocene 
  forms 
  and 
  approximating 
  to 
  Thalassochelys. 
  

  

  I 
  may 
  observe, 
  in 
  passing, 
  that 
  humeri 
  in 
  the 
  British 
  Museum 
  

   (e. 
  g., 
  No. 
  35365) 
  indicate 
  the 
  occurrence 
  of 
  Athecate 
  Chelonians 
  in 
  

   the 
  Cambridge 
  Greensand, 
  which 
  I 
  am 
  disposed 
  to 
  refer 
  to 
  the 
  

   American 
  Cretaceous 
  genus 
  Protostega 
  of 
  Cope. 
  

  

  3. 
  Aegillochelys 
  (nov. 
  gen.) 
  from 
  the 
  London 
  Clay. 
  

  

  I 
  may 
  take 
  the 
  opportunity 
  of 
  mentioning 
  that 
  the 
  skull 
  figured 
  

   in 
  pi. 
  sv. 
  of 
  pt. 
  i. 
  of 
  Owen's 
  ' 
  Reptilia 
  of 
  the 
  London 
  Clay 
  ' 
  as 
  the 
  

   type 
  of 
  Chelone 
  cuneiceps 
  appears 
  to 
  me 
  to 
  indicate 
  a 
  form 
  presenting 
  

   affinities 
  both 
  with 
  Lytoloma, 
  Thalassochelys, 
  and 
  Chelone, 
  but 
  

   which 
  cannot 
  be 
  referred 
  to 
  any 
  one 
  of 
  these 
  genera. 
  I 
  believe 
  that 
  

   the 
  skull 
  figured 
  on 
  pi. 
  xxv. 
  of 
  the 
  same 
  writer's 
  ' 
  History 
  of 
  British 
  

   Fossil 
  Reptiles,' 
  vol. 
  ii. 
  Chelonia, 
  under 
  the 
  name 
  of 
  Chelone 
  conveoca, 
  

   also 
  belongs 
  to 
  the 
  same 
  species 
  ; 
  the 
  occipital 
  shield 
  (interoccipital 
  

   of 
  Owen) 
  being 
  thrust 
  back 
  in 
  the 
  adult. 
  Eor 
  this 
  form 
  I 
  pro- 
  

   pose 
  the 
  generic 
  name 
  Argillochelys, 
  of 
  which 
  I 
  shall 
  give 
  the 
  full 
  

   description 
  in 
  the 
  British 
  Museum 
  ' 
  Catalogue 
  of 
  Fossil 
  Reptilia 
  ;' 
  I 
  

   may 
  mention, 
  however, 
  that 
  it 
  is 
  chiefly 
  characterized 
  by 
  the 
  extreme 
  

   shortness 
  and 
  anterior 
  breadth 
  of 
  the 
  pterygoids, 
  in 
  which 
  the 
  lateral 
  

   borders 
  are 
  deeply 
  emarginate, 
  and 
  the 
  ectopterj'goid 
  processes 
  are 
  

   placed 
  at 
  the 
  antero-external 
  angles 
  instead 
  of 
  near 
  the 
  middle 
  of 
  

   these 
  bones. 
  The 
  palate 
  and 
  mandibular 
  symphysis 
  are 
  ridged, 
  

   and, 
  at 
  least 
  in 
  the 
  young, 
  the 
  skull 
  has 
  an 
  azygous 
  occipital 
  shield, 
  

   as 
  in 
  Thalassochelys. 
  I 
  believe 
  that 
  other 
  Chelonians 
  from 
  the 
  

   London 
  Clay 
  described 
  by 
  Sir 
  B,. 
  Owen 
  may 
  also 
  be 
  referred 
  to 
  this 
  

   genus, 
  and 
  especially 
  the 
  skull 
  figured 
  under 
  the 
  name 
  of 
  Chelone 
  

   brachyceps. 
  Some 
  of 
  these 
  forms 
  were 
  included 
  by 
  Prof. 
  Cope 
  in 
  

   his 
  Puppigerus. 
  

  

  4. 
  Plesiochelys 
  (n. 
  sp.) 
  /rom 
  the 
  Wealden. 
  

  

  On 
  page 
  272 
  of 
  a 
  paper 
  published 
  by 
  Mr. 
  G. 
  A. 
  Boulenger 
  and 
  

   myself 
  in 
  the 
  ' 
  Geological 
  Magazine 
  ' 
  for 
  1887, 
  mention 
  is 
  made 
  of 
  

  

  * 
  Ann. 
  Soc. 
  Geol. 
  Nord, 
  vol. 
  xv. 
  p. 
  122 
  (1888). 
  

  

  