﻿382 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM 
  vol. 
  08 
  

  

  Characters. 
  — 
  Upperparts 
  brown, 
  head, 
  outer 
  sides 
  of 
  forelimbs, 
  and 
  

   thighs 
  darker 
  than 
  back; 
  forehead 
  with 
  a 
  conspicuous 
  whitish 
  tri- 
  

   angular 
  patch; 
  underparts 
  whitish 
  to 
  buffy. 
  

  

  Variation. 
  — 
  Variations 
  in 
  color 
  are 
  described 
  under 
  locality 
  headings 
  

   listed 
  below. 
  No 
  color 
  differences 
  are 
  apparent 
  between 
  sexes; 
  

   cranium 
  of 
  female 
  slightly 
  more 
  vaulted 
  in 
  frontal 
  region, 
  the 
  brain 
  

   case 
  slightly 
  less 
  dolichocephalic 
  than 
  in 
  male; 
  canines 
  of 
  male 
  longer 
  

   and 
  heavier. 
  

  

  A 
  rudimentary 
  thumb 
  is 
  of 
  common 
  occurrence. 
  In 
  most 
  instances, 
  

   the 
  bony 
  vestige 
  of 
  the 
  thumb 
  is 
  too 
  short 
  to 
  be 
  detected 
  externally 
  

   as 
  a 
  digit. 
  In 
  one 
  individual 
  from 
  Guaimaral 
  (U.S.N.M. 
  No. 
  281779) 
  

   a 
  vestigial 
  thumb 
  bearing 
  a 
  nail 
  appears 
  on 
  each 
  hand. 
  One 
  specimen 
  

   from 
  the 
  Rio 
  Tarra 
  has 
  a 
  vestigial 
  nailless 
  thumb 
  on 
  each 
  hand. 
  Six 
  

   other 
  individuals 
  show 
  the 
  rudiment 
  on 
  the 
  right 
  hand 
  only. 
  Greater 
  

   frequency 
  of 
  obsolescence 
  of 
  the 
  left 
  thumb 
  may 
  indicate 
  a 
  tendency 
  

   toward 
  right-handedness 
  in 
  Ateles 
  hybridus. 
  

  

  La 
  Gloria 
  (two 
  females) 
  : 
  One 
  specimen 
  immature 
  ; 
  back 
  of 
  other, 
  

   a 
  flat 
  skin, 
  nearly 
  entirely 
  bare 
  as 
  result 
  either 
  of 
  faulty 
  preservation 
  

   or 
  improper 
  tanning. 
  Both 
  specimens 
  agree 
  with 
  the 
  large 
  series 
  

   form 
  the 
  Rio 
  Cesar, 
  described 
  below. 
  

  

  Remarks. 
  — 
  Unfortimately 
  the 
  locality 
  designated 
  as 
  typical 
  is 
  

   represented 
  by 
  poor 
  material. 
  On 
  a 
  geographical 
  basis, 
  however, 
  no 
  

   better 
  choice 
  could 
  have 
  been 
  made 
  as 
  it 
  is 
  wholly 
  improbable 
  that 
  any 
  

   other 
  locality 
  from 
  which 
  specimens 
  are 
  available 
  was 
  visited 
  by 
  

   Plee, 
  collector 
  of 
  the 
  type 
  series. 
  In 
  general, 
  specimens 
  of 
  mammals 
  

   taken 
  by 
  the 
  writer 
  in 
  La 
  Gloria 
  agree 
  best 
  with 
  corresponding 
  ones 
  

   secured 
  by 
  Plee. 
  The 
  lectotype 
  of 
  hybridus 
  is 
  considerably 
  faded 
  on 
  

   the 
  left 
  side 
  of 
  body, 
  arm, 
  and 
  foreleg. 
  Otherwise, 
  it 
  is 
  in 
  good 
  con- 
  

   dition 
  and 
  agrees 
  completely 
  with 
  average 
  specimens 
  of 
  the 
  Rio 
  Cesar 
  

   series. 
  The 
  adult 
  male 
  cotype 
  in 
  the 
  Paris 
  Museum 
  is 
  darker, 
  more 
  

   uniformly 
  brown 
  than 
  the 
  lectotype 
  and 
  agrees 
  with 
  darker 
  indi- 
  

   viduals 
  from 
  the 
  Cesar. 
  The 
  immature 
  male 
  cotype 
  is 
  badly 
  faded 
  

   but 
  appears 
  to 
  have 
  been 
  grayish 
  or 
  buffy 
  when 
  alive. 
  In 
  this 
  

   respect 
  it 
  resembles 
  the 
  type 
  of 
  Ateles 
  albifrons 
  Gray, 
  which, 
  whatever 
  

   its 
  original 
  coloration, 
  is 
  now 
  pale 
  buffy 
  with 
  the 
  extremities 
  darker. 
  

  

  The 
  name 
  hybridus 
  was 
  elected 
  by 
  Geoffroy 
  on 
  the 
  testimony 
  of 
  

   Roulin 
  that 
  the 
  vernacular 
  name 
  of 
  the 
  monkey 
  in 
  Colombia 
  is 
  mono 
  

   zambo, 
  or 
  "mulatto" 
  monkey. 
  In 
  Colombia, 
  however, 
  the 
  name 
  mono 
  

   is 
  generally 
  applied 
  to 
  howlers, 
  genus 
  Alouatta. 
  The 
  red 
  howler, 
  A. 
  

   seniculus, 
  is 
  known 
  as 
  mono 
  Colorado, 
  the 
  dark 
  brown 
  howler, 
  A. 
  

   palliata, 
  as 
  mono 
  zambo. 
  In 
  Andean 
  countries, 
  marimonda 
  is 
  the 
  

   common 
  criollan 
  name 
  for 
  spider 
  monkeys 
  ; 
  maguisapa 
  is 
  the 
  Quechua 
  

   equivalent. 
  

  

  Guaimaral 
  and 
  El 
  Orinoco, 
  Rio 
  Cesar 
  (9 
  males, 
  10 
  females): 
  Skin 
  of 
  

  

  