﻿determined 
  by 
  Vertebrate 
  Fossils. 
  337 
  

  

  discoveries 
  have 
  been 
  made, 
  especially 
  in 
  the 
  West, 
  and 
  much 
  

   information 
  bearing 
  on 
  the 
  subject 
  has 
  been 
  obtained 
  from 
  

   various 
  quarters. 
  In 
  1884, 
  the 
  author 
  revised 
  and 
  extended 
  

   the 
  first 
  section 
  for 
  his 
  monograph 
  on 
  the 
  Dinocerata, 
  and 
  it 
  

   seems 
  fitting 
  on 
  the 
  present 
  occasion 
  to 
  bring 
  together 
  once 
  

   more 
  some 
  of 
  the 
  later 
  evidence, 
  and 
  place 
  on 
  record 
  the 
  more 
  

   - 
  important 
  horizons 
  now 
  known 
  to 
  the 
  author 
  by 
  personal 
  

   exploration, 
  or 
  by 
  other 
  investigations 
  which 
  he 
  has 
  verified. 
  

  

  The 
  accompanying 
  section, 
  Plate 
  XII, 
  is 
  designed 
  to 
  represent 
  

   in 
  outline, 
  in 
  their 
  geological 
  order, 
  the 
  successive 
  horizons 
  at 
  

   present 
  known 
  with 
  certainty 
  from 
  characteristic 
  vertebrate 
  

   fossils. 
  The 
  correlation 
  of 
  these 
  horizons 
  with 
  those 
  deter- 
  

   mined 
  on 
  other 
  evidence 
  is 
  important, 
  and 
  considerable 
  progress 
  

   in 
  this 
  direction 
  has 
  already 
  been 
  made, 
  but 
  the 
  results 
  cannot 
  

   be 
  presented 
  here. 
  

  

  In 
  comparing 
  the 
  present 
  section 
  with 
  the 
  one 
  first 
  published 
  

   by 
  the 
  author, 
  it 
  will 
  be 
  noticed 
  that 
  no 
  vertebrates 
  are 
  yet 
  

   known 
  in 
  the 
  Archaean 
  or 
  Cambrian, 
  but 
  a 
  single 
  fortunate 
  

   discovery 
  in 
  Colorado 
  has 
  recently 
  carried 
  back 
  the 
  first 
  known 
  

   appearance 
  of 
  Fishes, 
  from 
  the 
  lower 
  Devonian 
  to 
  the 
  lower 
  

   Silurian, 
  or 
  more 
  specifically, 
  from 
  the 
  Schoharie 
  Grit 
  to 
  the 
  

   Trenton. 
  

  

  The 
  next 
  point 
  of 
  importance 
  is 
  in 
  the 
  Triassic, 
  in 
  the 
  horizon 
  

   of 
  the 
  Connecticut 
  river 
  sandstone 
  where 
  so 
  many 
  foot-prints 
  

   have 
  been 
  found, 
  and 
  attributed 
  to 
  Birds. 
  Recent 
  discoveries 
  

   in 
  these 
  beds 
  have 
  shown 
  that 
  at 
  least 
  three 
  distinct 
  forms 
  of 
  

   carnivorous 
  Dinosaurian 
  reptiles, 
  all 
  of 
  moderate 
  size, 
  lived 
  at 
  

   that 
  period, 
  and 
  doubtless 
  did 
  their 
  share 
  in 
  leaving 
  foot-prints 
  

   behind 
  them. 
  In 
  two 
  of 
  the 
  skeletons 
  secured, 
  the 
  bones 
  of 
  

   the 
  hind 
  feet 
  are 
  still 
  in 
  position, 
  and 
  in 
  life 
  could 
  have 
  made 
  

   some 
  of 
  the 
  foot-prints 
  previously 
  discovered. 
  

  

  .Near 
  the 
  base 
  of 
  the 
  Jurassic, 
  a 
  new 
  horizon 
  may 
  now 
  be 
  

   defined 
  as 
  the 
  Hallopus 
  beds, 
  as 
  here 
  alone 
  remains 
  of 
  the 
  

   remarkable 
  reptile 
  named 
  by 
  the 
  author 
  Hallopus 
  victor 
  have 
  

   been 
  found. 
  Another 
  diminutive 
  Dinosaur, 
  JVanosaurus, 
  

   occurs 
  in 
  the 
  same 
  strata. 
  This 
  horizon 
  is 
  believed 
  to 
  be 
  

   lower 
  than 
  the 
  Baptanodon 
  beds, 
  although 
  the 
  two 
  have 
  not 
  

   been 
  found 
  together. 
  The 
  Hallopus 
  beds 
  now 
  known 
  are 
  in 
  

   Colorado, 
  below 
  the 
  Atlantosaurus 
  beds, 
  but 
  quite 
  distinct 
  

   from 
  them. 
  

  

  The 
  Baptanodon 
  beds 
  have 
  been 
  found 
  at 
  many 
  localities, 
  

   in 
  Dakota, 
  Wyoming, 
  and 
  northern 
  Utah, 
  everywhere 
  beneath 
  

   the 
  Atlantosaurus 
  beds, 
  and 
  having 
  below 
  them, 
  at 
  various 
  

   localities, 
  a 
  series 
  of 
  red 
  beds, 
  which 
  may, 
  perhaps, 
  contain 
  the 
  

   Hallopus 
  horizon, 
  but 
  are 
  generally 
  regarded 
  as 
  Triassic. 
  

  

  Beside 
  the 
  two 
  species 
  of 
  Baptanodon 
  described 
  by 
  the 
  

   author, 
  the 
  next 
  vertebrate 
  in 
  importance, 
  in 
  the 
  same 
  horizon, 
  

  

  