﻿AND 
  AYES 
  OF 
  NORTH 
  AMERICA. 
  117 
  

  

  If 
  Dr. 
  Leidy 
  had 
  left 
  the 
  matter 
  undecided 
  as 
  to 
  which 
  of 
  these 
  he 
  regarded 
  as 
  the 
  type 
  of 
  the 
  genus 
  Dinodon, 
  

   the 
  almost 
  universal 
  practice 
  of 
  naturalists 
  would 
  refer 
  the 
  name 
  to 
  that 
  form 
  which 
  should 
  not 
  be 
  first 
  thereafter 
  

   discovered 
  to 
  be 
  distinct, 
  and 
  named. 
  

  

  I 
  have 
  been 
  of 
  the 
  opinion 
  that 
  the 
  two 
  forms 
  of 
  teeth 
  included 
  by 
  Leidy 
  under 
  the 
  head 
  of 
  Dinodon 
  really 
  belong 
  

   to 
  distinct 
  animals, 
  and 
  Leidy 
  is 
  also 
  of 
  that 
  opinion. 
  In 
  18G6, 
  in 
  describing 
  the 
  genus 
  Laelaps 
  (Proc. 
  Acad., 
  p. 
  27!)), 
  

   I 
  said, 
  " 
  The 
  genus 
  Laelaps 
  belongs 
  to 
  the 
  family 
  Dinodontidae 
  which 
  is 
  characterized, 
  * 
  * 
  by 
  its 
  compressed, 
  

   sabre-shaped 
  teeth. 
  It 
  differs 
  * 
  * 
  from 
  Dinodon 
  in 
  that 
  teeth 
  of 
  the 
  latter 
  have 
  two 
  posterior 
  serrate 
  edges 
  

   separated 
  by 
  a 
  posterior 
  plane." 
  This, 
  then, 
  according 
  to 
  the 
  usage 
  of 
  naturalists 
  establishes 
  the 
  name 
  Dinodon 
  for 
  

   the 
  truncate 
  teeth 
  and 
  Laelaps. 
  for 
  the 
  two-edged 
  . 
  

  

  Dr. 
  Leidy 
  however 
  in 
  an 
  essay 
  published 
  in 
  Proc. 
  Academy 
  Nat. 
  Sci., 
  18G8, 
  p. 
  198, 
  in 
  expressing 
  his 
  belief 
  in 
  the 
  

   distinctness 
  of 
  the 
  two 
  genera, 
  states 
  that 
  "teeth 
  of 
  like 
  shape" 
  (i. 
  e. 
  like 
  Megalosaurus) 
  referred 
  by 
  me 
  to 
  Dinodon 
  

   alone 
  belong 
  to 
  this 
  genus, 
  and 
  names 
  the 
  species 
  represented 
  by 
  the 
  truncate 
  teeth, 
  or 
  the 
  true 
  Dinodon 
  horridus, 
  

   Aublysodon 
  mirandus. 
  He 
  then 
  goes 
  on 
  to 
  say, 
  "Future 
  discovery 
  may 
  prove 
  Laelaps 
  and 
  Dinodon 
  identical," 
  and 
  

   on 
  p. 
  199 
  * 
  "An 
  enemy 
  which 
  may 
  perhaps 
  on 
  nearer 
  comparison 
  of 
  corresponding 
  parts 
  prove 
  to 
  be 
  

  

  another 
  species 
  of 
  the 
  same 
  genus 
  until 
  now 
  supposed 
  to 
  be 
  different, 
  under 
  the 
  names 
  of 
  Dinodon 
  and 
  Laelaps.'" 
  

   It 
  is 
  thus 
  sufficiently 
  obvious 
  that 
  the 
  proposition 
  is 
  to 
  refer 
  Laelaps 
  as 
  a 
  synonyme 
  of 
  Dinodon. 
  It 
  appears 
  to 
  me, 
  

   on 
  the 
  other 
  hand, 
  that 
  this 
  is 
  contrary 
  to 
  the 
  rules 
  of 
  nomenclature, 
  and 
  the 
  principles 
  which 
  lie 
  at 
  their 
  root, 
  and 
  

   that 
  the 
  name 
  Aublysodon 
  is 
  a 
  synonyme 
  of 
  Dinodon. 
  

  

  This 
  is 
  however 
  on 
  the 
  supposition 
  that 
  Leidy 
  had 
  left 
  the 
  question 
  open 
  or 
  uncertain, 
  as 
  to 
  which 
  of 
  the 
  two 
  

   forms 
  of 
  teeth 
  was 
  characteristic 
  of 
  his 
  genus 
  Dinodon. 
  I 
  think 
  however 
  he 
  has 
  not 
  left 
  it 
  undecided, 
  and 
  I- 
  am 
  

   supported 
  in 
  this 
  by 
  the 
  opinion 
  of 
  Von 
  Meyer. 
  

  

  The 
  teeth 
  of 
  Laelaps 
  both 
  from 
  New 
  Jersey 
  and 
  Nebraska 
  do 
  not 
  differ 
  from 
  those 
  of 
  Megalosaurus, 
  while 
  those 
  

   of 
  Dinodon 
  do. 
  It 
  was 
  not 
  to 
  be 
  supposed 
  that 
  Dinodon 
  was 
  established 
  on 
  teeth 
  of 
  the 
  former 
  character, 
  as 
  the 
  

   practice 
  of 
  describing 
  species 
  and 
  genera, 
  without 
  a 
  basis 
  of 
  distinctive 
  characters 
  is 
  an 
  unusual 
  and 
  bad 
  one, 
  and 
  

   ought 
  not 
  to 
  be 
  tolerated 
  in 
  natural 
  science. 
  

  

  In 
  describing 
  Dinodon, 
  Leidy 
  says 
  the 
  Laelaps-like 
  teeth 
  resemble 
  those 
  of 
  Megalosaurus, 
  and 
  in 
  his 
  recent 
  

   article 
  in 
  the 
  Proc. 
  Academy 
  (p. 
  198), 
  that 
  they 
  are 
  "identical 
  in 
  character 
  with 
  those 
  of 
  Megalosaurus." 
  

  

  He 
  moreover 
  specifies 
  that 
  the 
  truncate 
  teeth 
  of 
  Dinodon 
  are 
  really 
  those 
  that 
  characterize 
  it, 
  in 
  the 
  following 
  

   words: 
  " 
  as 
  the 
  entire 
  dentition 
  of 
  Megalosaurus 
  has 
  not 
  yet 
  been 
  ascertained, 
  it 
  may 
  turn 
  out 
  to 
  be 
  the 
  case 
  that 
  in 
  

   other 
  parts 
  of 
  the 
  jaws 
  than 
  those 
  known, 
  it 
  possesses 
  teeth 
  like 
  the 
  ones 
  above 
  described 
  as 
  peculiar. 
  Should 
  on 
  

   future 
  discovery 
  such 
  a 
  condition 
  of 
  things 
  be 
  proved 
  to 
  exist, 
  Dinodon 
  wjuld 
  then 
  cease 
  to 
  be 
  anything 
  more 
  than 
  a 
  

   second 
  species 
  of 
  Megalosaurus." 
  The 
  truncate 
  teeth 
  are 
  then 
  the 
  "peculiar" 
  feature 
  of 
  Dinodon, 
  and 
  all 
  that 
  

   prevents 
  the 
  species 
  from 
  being 
  referred 
  to 
  Megalosaurus. 
  

  

  Von 
  Meyer 
  has 
  understood 
  this 
  language 
  as 
  I 
  have, 
  and 
  has 
  believed 
  that 
  the 
  teeth 
  now 
  ascribed 
  by 
  Leidy 
  to 
  

   AvMysodon, 
  are 
  really 
  characteristic 
  of 
  Dinodon. 
  He 
  says 
  (Palseontographica, 
  vii, 
  p. 
  267) 
  that 
  some 
  of 
  the 
  teeth 
  

   " 
  indicate 
  such 
  peculiarity, 
  that 
  Leidy, 
  who 
  has 
  made 
  the 
  investigation, 
  thought 
  it 
  necessary 
  to 
  characterize 
  the 
  

   animal 
  as 
  distinct 
  from 
  Megalosaurus, 
  under 
  the 
  name 
  of 
  Dinodon 
  horridus. 
  

  

  It 
  is 
  therefore 
  evident 
  that 
  the 
  Laelaps-like 
  teeth 
  described 
  under 
  Dinodon, 
  are 
  really 
  those 
  that 
  require 
  a 
  new 
  

   name, 
  if 
  any. 
  I 
  will 
  not 
  give 
  them 
  a 
  name 
  however, 
  since 
  there 
  is 
  no 
  evidence 
  that 
  they 
  differ 
  from 
  either 
  Megalo- 
  

   saurus 
  or 
  Laelaps, 
  though 
  of 
  course 
  the 
  probability 
  is, 
  that 
  they 
  belong 
  to 
  a 
  species 
  of 
  the 
  latter 
  genus. 
  

  

  Although 
  Aublysodon 
  would 
  thus 
  be 
  a 
  synonyme 
  of 
  Dinodon, 
  it 
  is 
  not 
  an 
  altogether 
  useless 
  name, 
  since 
  the 
  

   latter 
  was 
  given 
  years 
  ago 
  to 
  a 
  genus 
  of 
  serpents 
  by 
  DumSril 
  and 
  Bibron, 
  and 
  may 
  therefore 
  be 
  suppressed. 
  

  

  The 
  classification 
  and 
  characters 
  here 
  employed 
  in 
  treating 
  of 
  the 
  Dinosauria, 
  were 
  embraced 
  in 
  the 
  original 
  

   essay 
  included 
  in 
  the 
  present 
  one, 
  which 
  was 
  read, 
  and 
  the 
  contents 
  communicated 
  verbally, 
  before 
  the 
  Academy 
  of 
  

   Natural 
  Sciences 
  in 
  the 
  spring 
  of 
  1867. 
  

  

  This 
  point 
  is 
  alluded 
  to 
  partly 
  because 
  the 
  portion 
  of 
  the 
  original 
  essay 
  on 
  the 
  Dinosauria 
  has 
  been 
  in 
  part 
  

  

  anticipated 
  by 
  the 
  publication 
  of 
  a 
  lecture 
  by 
  Prof. 
  T. 
  H. 
  Huxley 
  before 
  the 
  Royal 
  Society 
  of 
  Great 
  Britain, 
  bearing 
  

  

  date 
  February 
  7, 
  1868. 
  The 
  tenor 
  and 
  result 
  of 
  the 
  studies 
  of 
  Prof. 
  Huxley 
  were 
  the 
  same 
  that 
  followed 
  my 
  own, 
  and 
  

  

  the 
  details 
  of 
  his 
  reasoning 
  are 
  thus 
  published 
  prior 
  to 
  mine. 
  The 
  position 
  of 
  the 
  ischia 
  and 
  pubes 
  in 
  the 
  Dinosauria. 
  

  

  AMERI. 
  PHILOSO. 
  SOC. 
  — 
  VOL. 
  XIV. 
  30 
  

  

  