﻿220 
  THE 
  EXTINCT 
  BATRACHIA, 
  REPTILIA 
  

  

  portion 
  flat 
  ; 
  its 
  outline 
  describes 
  nearly 
  half 
  a 
  circle, 
  of 
  which 
  the 
  inner 
  portion 
  only 
  is 
  

   thickened 
  for 
  the 
  articular 
  face 
  of 
  a 
  carpal 
  : 
  the 
  outer 
  distal 
  angle 
  is 
  thus 
  directed 
  back- 
  

   wards, 
  towards 
  the 
  humerus. 
  The 
  humeral 
  articular 
  extremity 
  is 
  a 
  single 
  transverse 
  

   plane. 
  

  

  The 
  ulna 
  is 
  broader 
  proximally 
  than 
  the 
  radius, 
  but 
  not 
  so 
  expanded, 
  the 
  extremities 
  

   being 
  of 
  nearly 
  equal 
  width. 
  The 
  extremities 
  of 
  ulna 
  and 
  radius 
  are 
  well 
  separated. 
  

  

  Three 
  carpal 
  bones 
  appear 
  to 
  belong 
  to 
  the 
  first 
  row. 
  They 
  are 
  fiat 
  and 
  oval, 
  the 
  ulnar 
  

   the 
  thickest, 
  the 
  radial 
  the 
  largest; 
  the 
  intermedial 
  has 
  six 
  articular 
  faces, 
  and 
  a 
  marginal 
  

   border, 
  which 
  was, 
  I 
  suppose, 
  posterior, 
  and 
  completed 
  the 
  inter-osseous 
  space 
  in 
  front. 
  

   A 
  fourth 
  bone, 
  which 
  belongs 
  either 
  to 
  the 
  second 
  series 
  or 
  to 
  the 
  metatarsals, 
  is 
  elongate 
  

   ovate 
  with 
  straight 
  parallel 
  borders, 
  both 
  quite 
  thin, 
  the 
  inner 
  the 
  shorter; 
  extremities 
  

   thickened, 
  rounded 
  inwards. 
  The 
  position 
  of 
  this 
  bone 
  has 
  been, 
  therefore, 
  longitudinal. 
  

  

  It 
  is 
  probable 
  that 
  the 
  fore-limb 
  was 
  long, 
  though 
  the 
  proximal 
  portions 
  are 
  so 
  much 
  

   shortened. 
  The 
  powerful 
  muscles 
  of 
  the 
  humerus 
  would 
  otherwise 
  be 
  without 
  object. 
  

   These 
  muscles, 
  with 
  the 
  peculiar 
  form 
  of 
  the 
  humerus, 
  probably 
  prevented 
  any 
  appearance 
  

   of 
  an 
  arm 
  in 
  life, 
  and 
  the 
  hand 
  would 
  be 
  nearly 
  sessile. 
  

  

  There 
  are 
  no 
  remains 
  of 
  hind 
  limbs, 
  though 
  there 
  is 
  no 
  sufficient 
  evidence 
  that 
  they 
  

   have 
  not 
  existed. 
  

  

  There 
  are 
  three 
  species 
  of 
  the 
  genus 
  Clidastes 
  known 
  to 
  the 
  writer, 
  which 
  differ 
  as 
  

   follows 
  : 
  

  

  Eleventh 
  vertebra 
  (or 
  the 
  first 
  without 
  trace 
  of 
  hypapophysis) 
  with 
  total 
  width 
  to 
  

   length 
  as 
  1 
  to 
  1.33., 
  the 
  inverted 
  centrum 
  roof-shaped, 
  elevated; 
  width 
  (total), 
  2 
  in. 
  3 
  

   lin. 
  Large. 
  c. 
  iguanavus. 
  

  

  Same 
  vertebra 
  with 
  width 
  to 
  length 
  as 
  less 
  than 
  1:2; 
  inverted 
  centrum, 
  lower, 
  more 
  

   broadly 
  rounded; 
  total 
  width, 
  1 
  in. 
  6 
  lin. 
  Small. 
  c. 
  propython. 
  

  

  The 
  generic 
  characters 
  are 
  almost 
  entirely 
  derived 
  from 
  the 
  second 
  species 
  named. 
  

  

  CLIDASTES 
  IGUANAVUS, 
  Cope. 
  

  

  Proceed. 
  Acad. 
  Nat. 
  Sci. 
  Phil. 
  1868, 
  223. 
  Geological 
  Survey, 
  New 
  Jersey, 
  Cook, 
  App. 
  C. 
  

  

  In 
  this 
  species 
  the 
  articular 
  face 
  of 
  the 
  zygosphens 
  is 
  inclined 
  at 
  an 
  angle 
  of 
  45°, 
  while 
  that 
  of 
  the 
  zygapophysis 
  

   is 
  a 
  little 
  more 
  horizontal. 
  The 
  posterior 
  zygapophyses 
  are 
  broken 
  off. 
  

  

  The 
  convex 
  articular 
  face 
  is 
  nearly 
  vertical, 
  meeting 
  the 
  lower 
  plane 
  at 
  a 
  slightly 
  less 
  angle 
  than 
  the 
  upper. 
  It 
  is 
  

   much 
  more 
  strongly 
  convex 
  transversely 
  than 
  vertically. 
  The 
  neural 
  arch 
  rises 
  from 
  the 
  anterior 
  three-fourths 
  of 
  the 
  

   centrum, 
  the 
  zygapophysis 
  coming 
  off 
  from 
  the 
  edge 
  of 
  the 
  cup, 
  and 
  the 
  diapophysis 
  from 
  .2 
  of 
  the 
  length 
  behind 
  it. 
  

   The 
  zygapophysis 
  is 
  more 
  prominent 
  than 
  the 
  zygosphen, 
  and 
  the 
  sinus 
  between 
  them 
  is 
  floored 
  by 
  a 
  thin 
  horizontal 
  

   plate 
  at 
  its 
  fundus. 
  

  

  The 
  general 
  form 
  of 
  the 
  vertebra 
  is 
  depressed. 
  The 
  inferior 
  face 
  of 
  the 
  centrum 
  presents 
  a 
  median 
  obtuse 
  ridge, 
  

   and 
  nearly 
  flat 
  lateral 
  faces, 
  which 
  are 
  concave 
  antero-posteriorly. 
  The 
  cup 
  is 
  broader 
  than 
  deep, 
  and 
  has 
  a 
  slightly 
  

   concave 
  outline 
  ; 
  the 
  base 
  of 
  the 
  zygosphen 
  originates 
  opposite 
  the 
  middle 
  of 
  the 
  neural 
  canal. 
  The 
  latter 
  is 
  a 
  broad 
  

   vertical 
  oval. 
  

  

  