﻿OF 
  FIVE 
  GENERA 
  OF 
  MESOZOIC 
  REPTILES. 
  

  

  43 
  

  

  Now 
  these 
  two 
  negative 
  features 
  at 
  once 
  distinguish 
  this 
  type 
  of 
  

   dorsal 
  vertebra 
  from 
  all 
  genera 
  of 
  Iguanodontidse 
  and 
  Tracho- 
  

   dontidoe 
  in 
  which 
  the 
  vertebrae 
  have 
  been 
  described 
  * 
  ; 
  the 
  whole 
  

   of 
  the 
  series 
  of 
  anterior 
  and 
  middle 
  dorsals 
  in 
  these 
  families 
  

   having 
  a 
  distinct 
  rib-facet 
  on 
  the 
  arch, 
  either 
  immediately 
  in 
  

   advance 
  of 
  or 
  somewhat 
  below 
  the 
  transverse 
  process, 
  and 
  a 
  deep 
  

   fossa 
  between 
  the 
  latter 
  and 
  the 
  postzygapophyses 
  f 
  . 
  In 
  the 
  Sceli- 
  

  

  Fis. 
  1. 
  

  

  (?) 
  Syngonosaurus 
  macrocercus. 
  — 
  Posterior 
  and 
  left 
  lateral 
  aspect 
  of 
  a 
  dorsal 
  

   vertebra, 
  from 
  the 
  Cambridge 
  Greensaad 
  ; 
  nat. 
  size, 
  t.p., 
  transverse 
  

   process; 
  pt.z., 
  postzygapophysis 
  ; 
  n.c, 
  neural 
  canal. 
  

  

  dosauridae, 
  however, 
  the 
  dorsal 
  vertebrae 
  of 
  the 
  type 
  skeleton 
  of 
  

   Hglceosaurus, 
  although 
  of 
  considerably 
  larger 
  size, 
  agree 
  with 
  the 
  

   present 
  specimens 
  in 
  the 
  above-mentioned 
  characters, 
  and 
  show 
  

   most 
  distinctly 
  the 
  " 
  step 
  "■ 
  on 
  the 
  transverse 
  process 
  for 
  the 
  articu- 
  

   lation 
  of 
  the 
  head 
  of 
  the 
  rib. 
  If, 
  indeed, 
  the 
  two 
  specimens 
  under 
  

   consideration 
  be 
  compared 
  with 
  the 
  eight 
  dorsals 
  still 
  remaining 
  in 
  

   apposition 
  in 
  the 
  type 
  skeleton 
  of 
  Hglceosaurus, 
  an 
  extremely 
  close 
  

   resemblance 
  is 
  noticeable. 
  Thus 
  the 
  shorter 
  and 
  carinated 
  vertebra 
  

   resembles 
  in 
  contour 
  the 
  penultimate 
  vertebra 
  of 
  that 
  series, 
  while 
  

   the 
  figured 
  specimen 
  agrees 
  equally 
  closely 
  with 
  the 
  last 
  and 
  latest 
  

   of 
  the 
  series 
  in 
  question, 
  and 
  also 
  with 
  a 
  detached 
  middle 
  dorsal 
  

   seen 
  on 
  the 
  right 
  of 
  the 
  slab. 
  

  

  * 
  With 
  the 
  possible 
  exception 
  of 
  those 
  figured 
  by 
  Prof. 
  Cope 
  (Eep. 
  TJ. 
  S. 
  

   Geol. 
  Surv. 
  Terr. 
  vol. 
  ii. 
  pi. 
  i.) 
  as 
  Cionodon. 
  

  

  t 
  Compare 
  the 
  figure 
  of 
  the 
  doi'sal 
  of 
  Iguanodon 
  on 
  p. 
  47 
  of 
  the 
  preceding 
  

   volume 
  of 
  this 
  Journal. 
  

  

  