﻿38 
  THE 
  EXTINCT 
  BATRACHIA, 
  REPTILIA 
  

  

  These 
  powerful 
  extremital 
  pieces 
  indicate 
  a 
  body 
  to 
  be 
  propelled, 
  of 
  not 
  less 
  than 
  usual 
  proportions. 
  If 
  this 
  he 
  

   the 
  case 
  the 
  number 
  of 
  dorsal 
  vertebrae 
  is 
  considerably 
  greater 
  than 
  in 
  the 
  species 
  of 
  this 
  order 
  in 
  general, 
  and 
  

   approaching 
  more 
  the 
  Ichthyosauri. 
  I 
  do 
  not 
  intend 
  to 
  suggest 
  any 
  affinity 
  between 
  the 
  latter 
  and 
  the 
  present 
  genus, 
  

   as 
  none 
  exists. 
  What 
  the 
  extent 
  of 
  cervical 
  vertebrae 
  may 
  have 
  been 
  is 
  uncertain. 
  The 
  caudals 
  have 
  probably 
  been 
  

   numerous, 
  though 
  not 
  probably 
  so 
  extended 
  as 
  in 
  Elasmosaurus. 
  

  

  The 
  size 
  of 
  the 
  species 
  can 
  be 
  approximately 
  estimated 
  from 
  the 
  proportions 
  furnished 
  by 
  Owen 
  (Reptiles 
  of 
  the 
  

   Liassic 
  Formations) 
  for 
  Plesiosaurus 
  rostratus. 
  The 
  skeleton 
  of 
  this 
  species 
  measures 
  11 
  feet 
  8 
  inches, 
  and 
  the 
  

   dorsal 
  vertebras 
  are 
  of 
  less 
  vertical 
  and 
  equal 
  transverse 
  diameter 
  compared 
  with 
  those 
  of 
  the 
  present 
  Saurian. 
  We 
  

   may 
  therefore 
  suppose 
  that 
  the 
  latter 
  exceeded 
  the 
  former 
  in 
  dimensions. 
  

  

  William 
  E. 
  Webb 
  of 
  Topeka 
  discovered 
  the 
  specimens 
  on 
  which 
  this 
  species 
  rests, 
  and 
  liberally 
  forwarded 
  them 
  

   to 
  me 
  for 
  examination 
  and 
  description. 
  

  

  ISCHYROSAURUS, 
  Cope. 
  

   Ischyrotherium 
  Leidy. 
  Trans. 
  Amer. 
  Philos. 
  Soc, 
  1860, 
  150. 
  

  

  This 
  genus 
  has 
  been 
  referred 
  by 
  Leidy 
  to 
  the 
  Mammalia, 
  and 
  to 
  the 
  order 
  Sirenia, 
  

   with 
  doubt. 
  Having 
  access 
  to 
  a 
  part 
  of 
  the 
  remains 
  on 
  which 
  it 
  was 
  established, 
  I 
  have 
  

   arrived 
  at 
  the 
  conviction 
  that 
  it 
  really 
  represents 
  an 
  aquatic 
  Saurian 
  more 
  or 
  less 
  distantly 
  

   related 
  to 
  Plesiosaurus. 
  My 
  reasons 
  for 
  regarding 
  it 
  as 
  Reptilian 
  and 
  not 
  Mammalian 
  

   are 
  : 
  first, 
  the 
  articulation 
  of 
  the 
  neural 
  arch 
  with 
  the 
  centrum 
  ; 
  second, 
  the 
  absence 
  of 
  

   epiphyses 
  ; 
  third, 
  the 
  absence 
  of 
  articulation 
  for 
  the 
  head 
  of 
  the 
  rib 
  on 
  the 
  centrum 
  ; 
  

   fourth, 
  the 
  lack 
  of 
  tuberculum 
  on 
  the 
  ribs. 
  

  

  With 
  respect 
  to 
  the 
  first 
  of 
  these 
  characters, 
  it 
  may 
  be 
  remarked 
  that 
  it 
  never 
  exists 
  

   in 
  mature 
  Mammalia, 
  and 
  disappears 
  at 
  an 
  early 
  period 
  of 
  the 
  development 
  of 
  all; 
  except 
  

   in 
  certain 
  seals 
  and 
  the 
  Echidna, 
  where 
  the 
  consolidation 
  of 
  the 
  neural 
  arch 
  is 
  a 
  little 
  

   delayed. 
  As 
  to 
  the 
  epiphyses, 
  there 
  is 
  no 
  trace 
  of 
  their 
  suture 
  to 
  be 
  found 
  on 
  fractured 
  

   surfaces, 
  supposing 
  their 
  existence 
  to 
  be 
  indicated 
  by 
  the 
  series 
  of 
  foramina 
  extending 
  on 
  

   the 
  inferior 
  surface 
  of 
  the 
  centrum 
  near 
  each 
  articular 
  extremity. 
  These 
  foramina 
  

   are, 
  I 
  believe, 
  merely 
  the 
  ruptured 
  coarse 
  cells, 
  which 
  can 
  be 
  found 
  near 
  the 
  articular 
  faces 
  

   in 
  the 
  vertebrae 
  in 
  all 
  Sauropterygia. 
  They 
  are 
  unusually 
  small 
  in 
  this 
  genus, 
  appropri- 
  

   ately 
  to 
  the 
  denser 
  structure 
  of 
  the 
  bones 
  as 
  compared 
  Avith 
  other 
  sea 
  saurians. 
  The 
  

   articulation 
  of 
  the 
  rib 
  takes 
  place 
  at 
  the 
  extremity 
  of 
  a 
  long 
  diapophysis, 
  and 
  there 
  only, 
  

   there 
  being 
  no 
  pit 
  for 
  the 
  eapitulum. 
  This 
  does 
  not 
  occur 
  in 
  Mammalia, 
  but 
  is 
  highly 
  

   characteristic 
  of 
  the 
  loAver 
  groups 
  of 
  the 
  Reptilia, 
  especially 
  the 
  Sauropterygia. 
  The 
  lum- 
  

   bar 
  series 
  in 
  Cetacea 
  presents 
  a 
  somewhat 
  similar 
  structure. 
  The 
  vertebrae 
  in 
  question 
  are 
  

   referred 
  by 
  Leidy 
  to 
  this 
  position, 
  but 
  they 
  are 
  clearly 
  median 
  dorsals, 
  from 
  the 
  elevated 
  

   position 
  and 
  length 
  of 
  the 
  diapophyses. 
  The 
  simple 
  form 
  of 
  the 
  ribs, 
  some 
  of 
  which 
  are 
  

   from 
  the 
  same 
  part 
  of 
  the 
  column, 
  is 
  quite 
  unknown 
  among 
  Mammalia, 
  

  

  There 
  are 
  other 
  significant 
  characters 
  of 
  less 
  value, 
  which 
  point 
  to 
  the 
  saurian 
  affini- 
  

   ties 
  of 
  this 
  genus, 
  and 
  confirm 
  the 
  preceding. 
  These 
  are 
  the 
  very 
  small 
  size 
  of 
  the 
  neural 
  

   canal, 
  the 
  cylindric 
  or 
  thickened 
  form 
  of 
  the 
  neural 
  arch, 
  and 
  the 
  strong 
  venous 
  foramina 
  

  

  