﻿CANYON 
  FERRY 
  FOSSIL 
  VERTEBRATES 
  — 
  ^WHITE 
  431 
  

  

  Transition 
  Zone 
  as 
  can 
  the 
  deposits 
  in 
  Weld 
  County, 
  Colo., 
  and 
  the 
  less- 
  

   well-known 
  faunas 
  of 
  Bates 
  Hole 
  and 
  Beaver 
  Divide, 
  Wyo. 
  Thomp- 
  

   son's 
  Creek, 
  McCarty's 
  Mountain, 
  and 
  the 
  Drummond 
  Beds 
  have 
  

   been 
  omitted 
  because 
  they 
  have 
  been 
  incompletely 
  reported 
  upon, 
  

   both 
  faunistically 
  and 
  stratigraphically. 
  

  

  The 
  fauna 
  of 
  the 
  Plains 
  Province 
  has 
  been 
  compiled 
  from 
  Scott, 
  et 
  al. 
  

   (1936-41), 
  Clark 
  (1937), 
  Cook 
  and 
  Cook 
  (1933), 
  and 
  Cook 
  (1934), 
  

   This 
  compilation 
  of 
  the 
  Plains 
  Province 
  fauna 
  may 
  be 
  introducing 
  

   error 
  into 
  the 
  comparisons 
  because, 
  with 
  a 
  north-south 
  extent 
  of 
  nearly 
  

   600 
  miles 
  for 
  the 
  Oligocene 
  deposits 
  of 
  the 
  plains, 
  latitudinal 
  zoning 
  

   may 
  have 
  existed. 
  But, 
  with 
  so 
  few 
  detailed 
  studies 
  of 
  limited 
  areas, 
  

   definite 
  evidence 
  either 
  for 
  or 
  against 
  latitudinal 
  zoning 
  is 
  wholly 
  

   lacking. 
  

  

  The 
  comparison 
  of 
  these 
  two 
  faunas 
  is 
  limited 
  by 
  necessity 
  to 
  the 
  

   smaller 
  mammals 
  because 
  the 
  remains 
  of 
  the 
  larger 
  forms, 
  particularly 
  

   the 
  titanotheres 
  and 
  rhinoceri, 
  are 
  often 
  too 
  fragmentary 
  for 
  more 
  

   than 
  family 
  identification. 
  However, 
  such 
  fragmentary 
  evidence 
  is 
  

   sufficient 
  to 
  establish 
  the 
  group 
  in 
  the 
  area 
  in 
  question. 
  Those 
  cases 
  

   where 
  the 
  generic 
  identification 
  is 
  reasonably 
  certain 
  but 
  no 
  specific 
  

   identification 
  can 
  be 
  made 
  are 
  indicated 
  in 
  table 
  3 
  by 
  the 
  abbreviation 
  

   "sp." 
  In 
  the 
  following 
  paragraphs 
  an 
  attempt 
  is 
  made 
  to 
  evaluate 
  

   the 
  differences 
  found 
  in 
  the 
  two 
  faunas. 
  

  

  Insectivora. 
  — 
  Although 
  representatives 
  of 
  this 
  group 
  are 
  not 
  

   numerous 
  in 
  collections, 
  one 
  finds 
  it 
  difficult 
  to 
  escape 
  the 
  inference 
  

   that 
  it 
  is 
  due 
  to 
  their 
  small 
  size. 
  There 
  are 
  two 
  genera, 
  Aioternodus 
  

   and 
  Ictops, 
  common 
  to 
  both 
  areas 
  but 
  the 
  species 
  are 
  distinct. 
  Two 
  

   genera, 
  Clinopternodus 
  and 
  Metacodon, 
  appear 
  to 
  be 
  confined 
  to 
  the 
  

   Plains 
  Province 
  and, 
  as 
  yet, 
  are 
  unknown 
  from 
  younger 
  deposits 
  

   outside 
  of 
  the 
  plains. 
  Two 
  genera, 
  Micropternodus 
  and 
  Domnina, 
  

   appear 
  to 
  be 
  confined 
  to 
  the 
  Mountain 
  Province. 
  Micropternodus 
  

   does 
  not 
  appear 
  to 
  have 
  survived 
  anywhere 
  beyond 
  the 
  Lower 
  Oli- 
  

   gocene, 
  and 
  Domnina 
  is 
  well 
  represented 
  in 
  the 
  Plains 
  Province 
  in 
  the 
  

   Middle 
  Oligocene. 
  Consequently, 
  one 
  would 
  expect 
  to 
  find 
  it 
  in 
  the 
  

   Lower 
  Oligocene 
  of 
  the 
  plains. 
  On 
  the 
  other 
  hand, 
  the 
  alternative 
  

   that 
  it 
  did 
  not 
  spread 
  to 
  the 
  plains 
  until 
  Middle 
  Oligocene 
  times 
  (as 
  

   appears 
  to 
  be 
  the 
  case 
  with 
  some 
  other 
  genera) 
  is 
  entirely 
  within 
  the 
  

   limits 
  of 
  possibility. 
  Since 
  Kentrogomphios 
  and 
  Talpa? 
  are 
  known 
  

   from 
  single 
  specimens 
  they 
  are 
  useless 
  for 
  this 
  study. 
  

  

  RoDENTiA. 
  — 
  Prosciurus 
  is 
  common 
  to 
  both 
  areas 
  in 
  both 
  the 
  Lower 
  

   and 
  Middle 
  Oligocene. 
  Ischyromys, 
  a 
  large 
  active 
  form, 
  appears 
  to 
  be 
  

   restricted 
  to 
  the 
  Mountain 
  Province 
  in 
  the 
  Lower 
  Oligocene 
  but 
  is 
  well 
  

   represented 
  in 
  the 
  Middle 
  Oligocene 
  of 
  the 
  plains, 
  where 
  it 
  underwent 
  

   considerable 
  radiation. 
  Titanotheriomys 
  and 
  Cylindrodon 
  are 
  common 
  

   to 
  both 
  areas 
  but 
  did 
  not 
  survive 
  into 
  the 
  Middle 
  Oligocene. 
  Pseudo- 
  

  

  