﻿218 
  THE 
  EXTINCT 
  BATRACHIA, 
  REPTILIA 
  

  

  The 
  form 
  of 
  the 
  centrum 
  presents 
  one 
  marked 
  peculiarity. 
  The 
  superior 
  rim 
  of 
  the 
  

   cup 
  is 
  excavated 
  for 
  the 
  passage 
  of 
  the 
  spinal 
  cord, 
  and 
  the 
  ball 
  is 
  concave 
  on 
  its 
  superior 
  

   aspect, 
  appropriately 
  to 
  the 
  same. 
  This 
  is 
  marked 
  on 
  cervicals 
  and 
  dorsals, 
  and 
  faintly 
  

   indicated 
  on 
  proximal 
  caudals. 
  There 
  are 
  no 
  ridges 
  on 
  the 
  centrum. 
  There 
  is 
  a 
  gradual 
  

   increase 
  in 
  length 
  from 
  the 
  cervicals 
  to 
  the 
  dorsals 
  and 
  lumbars. 
  Those 
  in 
  the 
  proximal 
  

   caudals 
  are 
  much 
  like 
  the 
  same 
  in 
  Mosasaurus, 
  that 
  is, 
  rounded 
  below, 
  and 
  with 
  three 
  su- 
  

   perior 
  faces, 
  the 
  lateral 
  being 
  the 
  longest. 
  The 
  distal 
  caudals 
  are 
  much 
  compressed. 
  

  

  The 
  neural 
  spines 
  of 
  the 
  cervical 
  vertebrae 
  commence 
  about 
  opposite 
  the 
  notches 
  between 
  

   the 
  zygosphens 
  and 
  zygapophyses, 
  and 
  are 
  attenuated 
  anteriorly 
  ; 
  they 
  are 
  stouter 
  behind. 
  

   The 
  ninth, 
  (the 
  first 
  preserved), 
  and 
  probably 
  those 
  anterior, 
  have 
  an 
  acute 
  edge 
  behind 
  

   as 
  well 
  as 
  before. 
  No 
  neural 
  spine 
  is 
  perfect 
  among 
  the 
  dorsals, 
  but 
  on 
  the 
  fifteenth 
  the 
  

   position 
  is 
  preserved 
  .75 
  the 
  length 
  of 
  the 
  centrum 
  ; 
  the 
  thinness 
  of 
  the 
  broken 
  edge 
  

   would 
  indicate 
  that 
  there 
  had 
  not 
  been 
  as 
  much 
  lost. 
  The 
  posterior 
  edge 
  is 
  nearly 
  oppo- 
  

   site 
  to 
  the 
  ends 
  of 
  the 
  zygapophyses 
  ; 
  its 
  posterior 
  slope 
  is 
  considerable. 
  They 
  are 
  evi- 
  

   dently 
  shorter 
  than 
  in 
  Mosasaurus. 
  

  

  The 
  neural 
  spines 
  of 
  the 
  caudals 
  are 
  various. 
  The 
  more 
  anterior 
  are 
  thicker 
  behind 
  

   and 
  alate 
  in 
  front, 
  narrowing 
  to 
  the 
  tip. 
  The 
  median 
  are 
  of 
  similar 
  form, 
  but 
  equally 
  

   alate 
  anteriorly 
  and 
  posteriorly. 
  The 
  more 
  posterior 
  are 
  much 
  narrowed 
  at 
  the 
  base, 
  and 
  

   present 
  only 
  the 
  alee 
  towards 
  the 
  extremity; 
  the 
  last 
  are 
  not 
  wider 
  than 
  the 
  haemal 
  

   spines. 
  

  

  The 
  chevron 
  bones 
  have 
  been 
  at 
  an 
  earlier 
  age 
  separated 
  from 
  the 
  centra, 
  but 
  as 
  in 
  

   Platecarpus, 
  they 
  are 
  entirely 
  coalescent 
  with 
  their 
  bases. 
  In 
  Mosasaurus 
  the 
  separation 
  

   persists. 
  They 
  have 
  two 
  short 
  haemapophysial 
  limbs, 
  and 
  a 
  very 
  long 
  tapering 
  spine, 
  

   which 
  is 
  grooved 
  in 
  front. 
  On 
  a 
  middle 
  caudal, 
  it 
  is 
  much 
  longer 
  than 
  the 
  centrum 
  and 
  

   neural 
  spine, 
  and 
  as 
  long 
  as 
  4.5 
  centra 
  adjacent. 
  All 
  the 
  haemal 
  arches 
  are 
  directed 
  ob- 
  

   liquely 
  posteriorly. 
  No 
  vertebrae 
  without 
  them 
  have 
  been 
  preserved. 
  

  

  Hypapophyses 
  exist 
  on 
  the 
  ten 
  cervical 
  vertebrae. 
  As 
  in 
  Mosasaurus, 
  their 
  extremi- 
  

   ties 
  are 
  concave, 
  and 
  are 
  articulated 
  to 
  distinct 
  bones 
  which 
  represent 
  a 
  distinct 
  hypapo- 
  

   physial 
  ossification. 
  These 
  bones 
  may 
  be 
  compared 
  to 
  short, 
  compressed 
  ungueal 
  pha- 
  

   langes. 
  The 
  articular 
  extremity 
  of 
  the 
  first 
  is 
  nearly 
  plane, 
  of 
  the 
  others 
  conic, 
  with 
  an- 
  

   teroposterior 
  enlargement. 
  They 
  are 
  directed 
  posteriorly, 
  and 
  have 
  a 
  broad 
  obliquely 
  

   ovate 
  outline 
  on 
  the 
  lateral 
  view. 
  Their 
  extremities 
  are 
  ruoose. 
  

  

  The 
  ribs 
  commence 
  at 
  the 
  axis, 
  which 
  has 
  borne 
  a 
  small 
  one. 
  There 
  is 
  no 
  distinct 
  

   parapophysis, 
  hence 
  each 
  rib-head 
  is 
  undivided, 
  but 
  is 
  flattened 
  vertically. 
  The 
  anterior 
  

   may 
  be 
  known 
  by 
  the 
  greater 
  compression 
  of 
  both 
  head 
  and 
  shaft. 
  The 
  rib 
  of 
  the 
  third 
  

   vertebra 
  has 
  a 
  narrow, 
  convex, 
  articular 
  surface, 
  and 
  is 
  concave 
  on 
  the 
  anterior 
  face. 
  That 
  

   of 
  the 
  fifth 
  is 
  much 
  wider, 
  and 
  with 
  more 
  truncate 
  head. 
  That 
  of 
  the 
  sixth 
  was 
  found 
  

  

  