﻿192 
  THE 
  EXTINCT 
  BATRACHIA, 
  REPTILIA 
  

  

  ing 
  of 
  a 
  sharp 
  unserrated 
  or 
  simple 
  cutting 
  edge. 
  These 
  acute 
  edges 
  or 
  carinse 
  separate 
  faces, 
  of 
  which 
  the 
  posterior 
  

  

  is 
  more 
  convex. 
  The 
  crowns 
  of 
  these 
  teeth 
  were 
  measured 
  by 
  Dr. 
  Fisher, 
  as 
  follows: 
  

  

  Inches. 
  Inches. 
  

  

  First, 
  anterior 
  face, 
  1 
  4-8 
  posterior, 
  1 
  7-8 
  

  

  Second, 
  " 
  " 
  13-8 
  " 
  2 
  

  

  Third, 
  " 
  " 
  1 
  2-8 
  " 
  1 
  2 
  2-8 
  

  

  The 
  pulp 
  cavity 
  extends 
  about 
  as 
  far 
  into 
  the 
  root 
  as 
  the 
  crown, 
  excepting 
  its 
  entrant 
  foramen 
  in 
  the 
  former. 
  

   The 
  mode 
  of 
  succession 
  of 
  the 
  teeth 
  is 
  well 
  seen 
  in 
  this 
  specimen, 
  and 
  illustrates 
  the 
  process 
  as 
  indicated 
  by 
  Leidy 
  

   (Cretac. 
  Kept., 
  p. 
  51). 
  The 
  fang-like 
  basis 
  of 
  the 
  functional 
  tooth 
  undergoes 
  extensive 
  excavation 
  by 
  absorption 
  to 
  

   furnish 
  space 
  for 
  its 
  successor, 
  the 
  remaining 
  portion 
  in 
  some 
  places 
  being 
  reduced 
  almost 
  to 
  a 
  shell, 
  yet 
  remaining 
  

   firmly 
  adherent 
  to 
  the 
  alveolar 
  walls, 
  without 
  the 
  slightest 
  evidence 
  of 
  displacement. 
  This 
  and 
  other 
  specimens 
  ex- 
  

   amined, 
  prove 
  that 
  the 
  old 
  tooth 
  is 
  not 
  removed 
  till 
  the 
  process 
  of 
  absorption 
  has 
  extended 
  to 
  the 
  alveolar 
  margin, 
  

   when 
  the 
  crown 
  is 
  easily 
  detached. 
  

  

  The 
  splenial 
  bones 
  present 
  the 
  usual 
  remarkable 
  character. 
  At 
  the 
  posterior 
  extremity 
  of 
  each, 
  the 
  articulating 
  

   cavity 
  is 
  narrow 
  ovoid 
  in 
  form, 
  subacuminate 
  below, 
  and 
  not 
  so 
  broadly 
  rounded 
  as 
  in 
  the 
  M. 
  dekayi 
  (fig. 
  47). 
  

  

  Incites. 
  

   Long 
  diameter, 
  3.25 
  

  

  Tra,nsverse, 
  ■ 
  1.75 
  

  

  Total 
  depth 
  of 
  splenial 
  at 
  extremity, 
  . 
  4.5 
  

  

  Of 
  rounded 
  face 
  below 
  dentary 
  plate, 
  2.25 
  

  

  The 
  surface 
  appears 
  to 
  be 
  adapted 
  for 
  motion 
  in 
  two 
  directions. 
  

   The 
  vertebra 
  which 
  accompanied 
  the 
  jaw 
  measures 
  as 
  follows: 
  

  

  Length 
  centrum, 
  4.7 
  

  

  Width 
  anterior 
  articular 
  face, 
  4.55 
  

  

  Depth 
  " 
  " 
  " 
  . 
  4.65 
  

  

  It 
  is 
  a 
  dorsal 
  with 
  diapophyses 
  below 
  the 
  middle; 
  between 
  it 
  and 
  the 
  neural 
  arch, 
  near 
  the 
  articular 
  extremities, 
  

   the 
  surface 
  is 
  marked 
  with 
  sub-longitudinal 
  rugae. 
  

  

  This 
  Mosasaur 
  could 
  not 
  have 
  been 
  less 
  than 
  eighty 
  feet 
  in 
  length. 
  * 
  

  

  As 
  compared 
  with 
  M. 
  giganteus, 
  this 
  species 
  presents 
  considerable 
  affinity. 
  The 
  Maastricht 
  animal 
  was 
  some- 
  

   what 
  smaller 
  than 
  either 
  of 
  those 
  here 
  described, 
  the 
  length 
  of 
  the 
  quadrate 
  bone 
  being 
  6 
  in. 
  4 
  lin., 
  or 
  more 
  as 
  in 
  our 
  

   specimens 
  of 
  M. 
  dekayi. 
  Its 
  elevated 
  sub-pentagonal 
  lumbars 
  and 
  caudals 
  are 
  also 
  more 
  as 
  in 
  M. 
  dekayi. 
  The 
  non- 
  

   coalescence 
  of 
  the 
  anterior 
  chevron 
  bones 
  in 
  M. 
  giganteus, 
  may 
  be 
  owing 
  to 
  immaturity. 
  As 
  compared 
  with 
  that 
  of 
  

   M. 
  maximus, 
  the 
  os 
  quadratum 
  presents 
  several 
  differences 
  and 
  resembles 
  that 
  of 
  M. 
  dekayi. 
  Thus 
  the 
  articular 
  ex- 
  

   tremity 
  which 
  extends 
  over 
  the 
  ala 
  is 
  small, 
  as 
  in 
  that 
  species; 
  the 
  median 
  posterior 
  ridge 
  is 
  rudimental 
  in 
  the 
  same, 
  

   not 
  a 
  strong 
  process 
  as 
  in 
  M. 
  maximus, 
  and 
  the 
  knob 
  is 
  small, 
  the 
  posterior 
  decurved 
  process 
  of 
  the 
  proximal 
  articular 
  

   face 
  nearly 
  in 
  contact 
  with 
  it. 
  The 
  distal 
  longitudinal 
  rib 
  is 
  relatively 
  twice 
  as 
  long 
  in 
  M. 
  giganteus 
  as 
  in 
  M. 
  maxi- 
  

   mus, 
  and 
  more 
  as 
  in 
  M. 
  dekayi. 
  Other 
  peculiarities 
  are 
  easily 
  found, 
  which 
  may 
  be 
  of 
  little 
  importance. 
  The 
  exter- 
  

   nal 
  part 
  of 
  the 
  distal 
  articular 
  face 
  is 
  pinched 
  up; 
  not 
  at 
  all 
  in 
  M. 
  maximus; 
  the 
  lower 
  part 
  of 
  the 
  ala 
  is 
  much 
  more 
  

   incurved 
  and 
  the 
  groove 
  on 
  its 
  margin 
  much 
  deeper. 
  

  

  The 
  51. 
  dekayi 
  may 
  attain 
  the 
  dimensions 
  of 
  this 
  species, 
  though 
  none 
  such 
  have 
  come 
  under 
  my 
  observation. 
  

  

  .From 
  the 
  lower 
  marl 
  bed 
  of 
  the 
  upper 
  cretaceous, 
  from 
  Monmouth 
  Co., 
  N. 
  Jersey, 
  

   and 
  Lumbcrton, 
  Gloucester 
  Co., 
  N. 
  Jersey. 
  

  

  MOSASAURUS 
  PRINCEPS, 
  Marsh. 
  

  

  Sillim. 
  Amer. 
  Journ. 
  Sci. 
  Arts, 
  18C9, 
  p. 
  392. 
  

  

  Prof. 
  Marsh 
  describes 
  an 
  individual 
  of 
  almost 
  equal 
  size 
  to 
  the 
  preceding, 
  which 
  he 
  distinguishes 
  from 
  them 
  Wv 
  the 
  

   form 
  of 
  the 
  quadrate 
  bone. 
  He 
  says 
  that 
  the 
  knob 
  near 
  the 
  meatus 
  is 
  well 
  developed; 
  and 
  the 
  proximal 
  articular 
  ex- 
  

  

  * 
  I 
  must, 
  express 
  my 
  obligations 
  i<> 
  Dr. 
  Fisher, 
  for 
  the 
  opportunttj 
  of 
  examining 
  the 
  above 
  specimens, 
  as 
  well 
  as 
  for 
  the 
  use 
  of 
  his 
  notes, 
  from 
  which 
  sev- 
  

   eral 
  extracts 
  are 
  made 
  in 
  the 
  above 
  description. 
  % 
  

  

  