﻿424 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM 
  vol. 
  103 
  

  

  and 
  no 
  natural 
  crosses 
  are 
  known. 
  Also 
  E. 
  -prezevaUkii 
  and 
  E. 
  onager 
  occur 
  to- 
  

   gether 
  in 
  Central 
  Asia 
  in 
  the 
  wild 
  state 
  and 
  no 
  undisputed 
  cases 
  of 
  crossing 
  are 
  

   known. 
  

  

  BoviDAE. 
  — 
  In 
  the 
  Malaj' 
  region 
  Lydekker 
  (1898) 
  records 
  four 
  species 
  of 
  Bos 
  

   (gaurvs, 
  indicus, 
  depressicornis, 
  and 
  frontalis) 
  occurring 
  in 
  the 
  same 
  area. 
  

  

  Antilopidae. 
  — 
  Allen 
  (1939) 
  reports 
  five 
  species 
  of 
  Gazella 
  (dorcas, 
  leptoceros, 
  

   thomsonii, 
  granti, 
  and 
  soemmerringii) 
  occurring 
  together 
  in 
  the 
  Anglo-Egyptian 
  

   Sudan. 
  

  

  Even 
  with 
  this 
  short 
  hst 
  it 
  is 
  obvious 
  that 
  two 
  or 
  more 
  species 
  of 
  a 
  

   single 
  genus 
  of 
  the 
  larger 
  mammals 
  do 
  occur 
  together 
  over 
  large 
  areas 
  

   and 
  in 
  essentially 
  the 
  same 
  habitat, 
  and 
  by 
  analogy 
  it 
  is 
  entirely 
  pos- 
  

   sible 
  that 
  more 
  than 
  one 
  species 
  of 
  a 
  genus 
  could 
  be 
  found 
  in 
  a 
  "quarry 
  

   fauna." 
  

  

  In 
  his 
  treatment 
  of 
  the 
  fauna 
  of 
  a 
  formation, 
  Matthew 
  (1930, 
  p. 
  272) 
  

   points 
  out 
  that 
  there 
  is 
  a 
  time 
  factor 
  involved 
  and 
  that 
  shifts 
  in 
  ranges 
  

   (possibly 
  due 
  to 
  minor 
  climatic 
  fluctuations 
  or 
  seasonal 
  movements 
  of 
  

   the 
  herds) 
  would 
  make 
  it 
  possible 
  for 
  species 
  with 
  adjacent 
  ranges 
  to 
  be 
  

   found 
  as 
  fossils 
  in 
  a 
  single 
  time 
  unit 
  of 
  a 
  formation. 
  This 
  is 
  illustrated 
  

   by 
  the 
  ranges 
  of 
  the 
  barren-ground 
  caribou 
  (Rangifer 
  arcticus) 
  and 
  the 
  

   woodland 
  caribou 
  (R. 
  caribou), 
  both 
  of 
  which 
  range 
  across 
  Canada 
  

   from 
  east 
  to 
  west 
  with 
  a 
  very 
  narrow 
  overlap 
  in 
  range. 
  Even 
  though 
  

   the 
  amount 
  of 
  overlap 
  did 
  not 
  change, 
  a 
  minor 
  climatic 
  change 
  would 
  

   permit 
  one 
  to 
  occupy 
  a 
  greater 
  amomit 
  of 
  the 
  former 
  territory 
  of 
  the 
  

   other 
  and 
  the 
  two 
  might 
  be 
  found 
  together 
  as 
  fossils, 
  dependent, 
  of 
  

   course, 
  on 
  the 
  accidents 
  of 
  preservation. 
  

  

  Another 
  method 
  by 
  which 
  species 
  of 
  adjacent 
  areas 
  may 
  be 
  intro- 
  

   duced 
  into 
  an 
  area 
  of 
  deposition 
  is 
  by 
  floods. 
  I 
  think 
  anyone 
  who 
  has 
  

   ever 
  seen 
  the 
  bloated 
  carcasses 
  of 
  cattle 
  floating 
  in 
  the 
  streams 
  of 
  the 
  

   west 
  during 
  a 
  summer 
  flood 
  will 
  admit 
  that 
  such 
  a 
  possibiHty 
  cannot 
  

   be 
  overlooked 
  in 
  regard 
  to 
  the 
  fluvial 
  deposits 
  of 
  the 
  plains. 
  Even 
  if 
  

   this 
  happened 
  only 
  once 
  in 
  each 
  climatic 
  microcycle 
  (11 
  years) 
  it 
  

   would 
  be 
  sufficient 
  to 
  establish 
  a 
  species 
  in 
  a 
  single 
  time 
  unit 
  of 
  a 
  for- 
  

   mation. 
  It 
  is 
  obvious, 
  of 
  course, 
  that 
  the 
  "visiting" 
  species 
  must, 
  

   have 
  its 
  range 
  upstream 
  fron 
  the 
  area 
  of 
  deposition. 
  A 
  shift 
  in 
  the 
  

   range 
  of 
  extraterritorial 
  forms 
  might 
  be 
  the 
  explanation 
  of 
  the 
  pres- 
  

   ence 
  of 
  Caenopus 
  in 
  only 
  the 
  Chadron 
  and 
  Upper 
  Brule 
  and 
  its 
  ab- 
  

   sence 
  in 
  the 
  Lower 
  Brule. 
  

  

  Another 
  item 
  which 
  must 
  be 
  kept 
  in 
  mind 
  in 
  the 
  consideration 
  of 
  

   fossil 
  faunas 
  is 
  the 
  territorial 
  range 
  of 
  the 
  individual. 
  Some 
  of 
  the 
  

   large 
  predators, 
  such 
  as 
  the 
  mountain 
  lion 
  (Felis 
  concolor) 
  and 
  the 
  

   grizzly 
  bear 
  (Ursus 
  horribilis), 
  have 
  a 
  territorial 
  range 
  with 
  a 
  200-mile 
  

   radius, 
  while 
  \vith 
  the 
  large 
  herbivores 
  it 
  seldom 
  exceeds 
  50 
  or 
  60 
  

   miles. 
  In 
  the 
  case 
  of 
  small 
  mammals, 
  such 
  as 
  Microlus, 
  the 
  radius 
  of 
  

   its 
  territorial 
  range 
  seldom 
  exceeds 
  20 
  or 
  25 
  feet. 
  Even 
  with 
  this 
  

   limited 
  nimiber 
  of 
  examples 
  it 
  is 
  clear 
  that 
  with 
  the 
  same 
  food 
  habits 
  

  

  