﻿200 
  THE 
  EXTINCT 
  BATRACHIA, 
  REFTILIA 
  

  

  For, 
  as 
  it 
  has 
  been 
  accepted 
  for 
  the 
  Mosasauroid 
  included 
  by 
  Gibbes, 
  by 
  the 
  next 
  

   writer, 
  Leidy, 
  it 
  must 
  be 
  retained 
  for 
  it, 
  according 
  to 
  the 
  just 
  rule 
  usually 
  followed. 
  

   There 
  is, 
  however, 
  for 
  us 
  no 
  evidence 
  that 
  the 
  present 
  genus 
  possessed 
  such 
  a 
  tooth, 
  and 
  

   as 
  the 
  teeth 
  of 
  all 
  the 
  genera 
  bear 
  such 
  a 
  close 
  mutual 
  resemblance, 
  I 
  think 
  it 
  must 
  be 
  

   left 
  for 
  future 
  discovery 
  to 
  determine 
  the 
  application 
  of 
  the 
  genus 
  Holcodus. 
  Name 
  from 
  

   IIXutt) 
  an 
  oar. 
  

  

  Dorsals 
  transversely 
  ovate, 
  rounded 
  ; 
  quadrate 
  bone 
  broad 
  as 
  long, 
  meatus 
  larger 
  ; 
  

   humerus 
  little 
  contracted 
  medially, 
  with 
  flat 
  shaft; 
  pterygoid 
  teeth, 
  eight. 
  

  

  P. 
  TYMPANITICUS. 
  

  

  PLATECARPUS 
  TYMPANITICUS, 
  Cope. 
  

  

  Holcodics 
  aculidens, 
  Leidy, 
  Cretaceous 
  Rept. 
  N. 
  Araer., 
  p. 
  118, 
  Tab. 
  VII 
  4-7; 
  VIII 
  1-2-7; 
  XI 
  14; 
  vix 
  Gibbsii 
  

   Smithson. 
  Contrib. 
  1851, 
  II 
  7, 
  "Tab. 
  I, 
  3-5, 
  vel 
  Leiclyi, 
  Loc. 
  Cit. 
  Tab. 
  X-17. 
  

  

  This 
  species 
  is 
  of 
  about 
  the 
  size 
  of 
  Mosasaurus 
  clepressus, 
  Cope, 
  under 
  which 
  head 
  some 
  of 
  its 
  characters 
  are 
  

   pointed 
  out. 
  The 
  single 
  specimen 
  representing- 
  it, 
  was 
  found 
  in 
  the 
  upper 
  cretaceous 
  of 
  Mississippi, 
  near 
  Columbus, 
  

   by 
  Dr. 
  William 
  Spillman. 
  

  

  LIODON, 
  Oioen. 
  

  

  Report 
  on 
  British 
  Fossil 
  Reptiles. 
  Proceedings 
  Brit. 
  Assoc. 
  Adv. 
  Sci., 
  1841, 
  p. 
  144. 
  Odontography 
  p. 
  261, 
  Tab. 
  

   LXXII, 
  fig. 
  1-2. 
  ? 
  Macrosaurus, 
  Owen, 
  Journ. 
  Geolog. 
  Soc. 
  London, 
  1849, 
  380. 
  Cope, 
  Proc. 
  Bost. 
  Soc. 
  Nat. 
  Hist., 
  

   1869, 
  264. 
  PNectoportheus, 
  Cope? 
  Proc. 
  Acad. 
  Nat. 
  Sci., 
  1868, 
  181. 
  

  

  This 
  genus 
  was 
  defined 
  by 
  Owen, 
  in 
  consequence 
  of 
  the 
  more 
  compressed 
  and 
  less 
  

   facetted 
  character 
  of 
  the 
  teeth 
  in 
  the 
  type 
  species, 
  L. 
  anceps, 
  Ow. 
  of 
  England. 
  This 
  

   character, 
  though 
  important, 
  is 
  shown 
  by 
  Leidy 
  to 
  be 
  evanescent, 
  as 
  indicated 
  by 
  more 
  

   , 
  than 
  one 
  species 
  of 
  the 
  United 
  States. 
  I 
  find 
  these 
  species 
  to 
  differ 
  materially 
  from 
  Mo- 
  

   sasaurus 
  in 
  the 
  separation 
  and 
  linear 
  form 
  of 
  the 
  pterygoids. 
  The 
  characters 
  are 
  chiefly 
  

   derived 
  from 
  the 
  L. 
  proriger, 
  Cope, 
  and 
  L. 
  mitchillii, 
  Dekay, 
  as 
  follows 
  : 
  

  

  The 
  pterygoid 
  bones 
  without 
  contact 
  on 
  the 
  median 
  line, 
  but 
  separated 
  by 
  a 
  consider- 
  

   able 
  interspace 
  throughout 
  their 
  length. 
  Pterygoid 
  not 
  entirely 
  pleurodont. 
  Chevron 
  

   bones 
  free 
  to 
  the 
  end 
  of 
  the 
  vertebral 
  column 
  ; 
  dorsals 
  with 
  rudiment 
  of 
  the 
  zygosphenal 
  

   articulation. 
  

  

  These 
  characters 
  may 
  be 
  those 
  of 
  Macrosaurus, 
  Owen, 
  but 
  the 
  palatal 
  characters 
  of 
  the 
  

   type 
  of 
  that 
  genus 
  are 
  unknown 
  ; 
  they 
  are 
  probably 
  similar 
  to 
  those 
  here 
  given, 
  as 
  it 
  ap- 
  

   proaches 
  Clidastes 
  in 
  the 
  form 
  of 
  the 
  vertebral 
  arches, 
  and 
  the 
  pterygoids 
  are 
  separate 
  in 
  

   the 
  latter. 
  The 
  vertebrae 
  known 
  to 
  belong 
  to 
  L. 
  proriger 
  present 
  the 
  compressed 
  form 
  of 
  

   those 
  of 
  Liodon 
  laevis. 
  The 
  vertebra? 
  of 
  L. 
  mitchillii 
  are, 
  however, 
  unknown. 
  The 
  ptery- 
  

   goid 
  tooth 
  of 
  a 
  species 
  like 
  the 
  last 
  was 
  named 
  Lesticodus 
  by 
  Leidy. 
  1 
  have 
  not 
  used 
  this 
  

   name 
  for 
  the 
  present 
  genus, 
  as 
  the 
  species 
  and 
  genus 
  to 
  which 
  the 
  type 
  pertained 
  are 
  not 
  

  

  