﻿186 
  

  

  THE 
  EXTINCT 
  BATRACHIA, 
  REPTILIA 
  

  

  teeth 
  are 
  well 
  known. 
  As 
  it 
  has 
  probably 
  been 
  earlier 
  named 
  M. 
  mitchillii 
  by 
  Dekay 
  

   that 
  name 
  will 
  remain 
  attached 
  to 
  it. 
  

  

  The 
  Elliptonodon 
  compressus, 
  Emmons, 
  I 
  do 
  not 
  consider 
  to 
  be 
  a 
  Mosasauroid. 
  The 
  

   Baseodon 
  reversus, 
  Leidy, 
  is 
  founded 
  on 
  pterygoid 
  teeth 
  of 
  some 
  species. 
  They 
  resemble 
  

   those 
  of 
  M. 
  dekayi. 
  

  

  MOSASAURUS, 
  Conybeare. 
  

  

  In 
  this 
  genus, 
  the 
  median 
  articulation 
  of 
  the 
  ramus 
  mandibuli 
  permitted 
  of 
  much 
  less 
  

   motion 
  than 
  in 
  Clidastes, 
  and 
  probably 
  allowed 
  of 
  only 
  a 
  moderate 
  expansion 
  of 
  the 
  in- 
  

   terramal 
  space. 
  That 
  it 
  permitted 
  the 
  deglutition 
  of 
  very 
  large 
  bodies 
  is 
  apparent. 
  The 
  

   accompanying 
  cut 
  exhibits 
  the 
  posterior 
  splenial 
  articular 
  face 
  in 
  two 
  views, 
  of 
  a 
  large 
  M. 
  

   dekayi 
  from 
  Gloucester 
  Co., 
  N. 
  J. 
  

  

  Fig. 
  47. 
  

  

  There 
  are 
  numerous 
  species 
  of 
  this 
  genus, 
  which 
  appear 
  to 
  belong 
  to 
  two 
  groups, 
  the 
  

   one 
  characterized 
  by 
  the 
  rounded, 
  and 
  the 
  other 
  by 
  the 
  depressed 
  form. 
  of 
  the 
  lumbar 
  ver- 
  

   tebrae. 
  A 
  species 
  of 
  the 
  latter 
  type 
  has 
  been 
  referred 
  to 
  the 
  genus 
  Ampliorosteus 
  by 
  

   Gibbes. 
  They 
  however 
  seem 
  to 
  graduate 
  into 
  each 
  other 
  through 
  such 
  species 
  as 
  M. 
  

   missuriensis, 
  in 
  such 
  a 
  way 
  as 
  to 
  preclude 
  the 
  idea 
  of 
  the 
  existence 
  of 
  distinction 
  on 
  that 
  

   ground. 
  The 
  teeth, 
  as 
  has 
  been 
  shown 
  by 
  Leidy, 
  present 
  a 
  considerable 
  range 
  of 
  varia- 
  

   tion, 
  which, 
  he 
  remarks, 
  if 
  too 
  great 
  to 
  be 
  embraced 
  by 
  a 
  single 
  species, 
  indicate 
  a 
  greater 
  

   number 
  of 
  species 
  than 
  has 
  been 
  supposed. 
  

  

  Having 
  access 
  to 
  a 
  considerable 
  amount 
  of 
  material, 
  contained 
  in 
  the 
  cabinets 
  of 
  the 
  

   Academy 
  Natural 
  Sciences, 
  the 
  State 
  Geological 
  Survey 
  at 
  New 
  Brunswick, 
  of 
  the 
  Mount 
  

   Holly 
  (Burlington 
  Co.) 
  Lyceum, 
  and 
  of 
  myself, 
  I 
  can 
  rely 
  with 
  confidence 
  on 
  the 
  exist- 
  

   ence 
  of 
  seven 
  species 
  of 
  the 
  restricted 
  genus. 
  These 
  are, 
  M. 
  maximus, 
  Cope, 
  M. 
  dekayi, 
  

   Bronn, 
  M. 
  fulciatus, 
  Cope, 
  M. 
  missuriensis, 
  Harlan, 
  M. 
  oarthrus, 
  Cope, 
  M. 
  depressus, 
  

   Cope, 
  M. 
  brumbyi, 
  Gibbes. 
  As 
  a 
  species 
  probably 
  distinct, 
  but 
  not 
  well 
  established, 
  I 
  

   include 
  M. 
  minor, 
  Gibbes. 
  

  

  Cranium. 
  The 
  species 
  named, 
  as 
  well 
  defined, 
  have 
  been 
  compared 
  in 
  their 
  quadrate 
  

   bones, 
  atlases, 
  and 
  lumbar 
  vertebra?, 
  where 
  the 
  most 
  marked 
  peculiarities 
  have 
  been 
  dis- 
  

  

  