﻿386 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM 
  vol.98 
  

  

  habitat 
  is 
  the 
  selva 
  rich 
  with 
  food 
  and 
  water. 
  However, 
  many 
  series 
  

   of 
  red 
  howlers 
  taken 
  by 
  the 
  writer 
  appeared 
  to 
  be 
  remnants 
  of 
  erst- 
  

   while 
  large 
  populations, 
  confined 
  to 
  small 
  relicts, 
  or 
  facsimiles 
  thereof, 
  

   of 
  primary 
  forest. 
  In 
  these 
  delimited 
  and 
  altered 
  habitats 
  individual 
  

   clans 
  of 
  howlers 
  have 
  become 
  isolated 
  from 
  the 
  mass 
  of 
  the 
  population. 
  

   With 
  continued 
  deforestation 
  these 
  clans 
  will 
  be 
  exterminated. 
  Indi- 
  

   viduals 
  do 
  persist, 
  however, 
  as 
  long 
  as 
  nature 
  provides 
  them 
  with 
  a 
  

   suitable 
  tree 
  and 
  its 
  fruit. 
  Unlike 
  their 
  more 
  resourceful, 
  or 
  more 
  

   adaptative 
  relatives, 
  howlers 
  do 
  not 
  ordinarily 
  supplement 
  their 
  ever- 
  

   diminishing 
  natural 
  larder 
  with 
  loot 
  from 
  cultivated 
  fields 
  circiun- 
  

   scribing 
  their 
  domain. 
  They 
  simply 
  eat 
  less 
  and 
  travel 
  less. 
  Their 
  

   growth 
  becomes 
  stunted, 
  their 
  resistance 
  to 
  disease 
  and 
  parasites 
  

   reduced. 
  At 
  the 
  same 
  time 
  they 
  fall 
  easier 
  to 
  predators 
  and 
  become 
  

   more 
  frequent 
  targets 
  for 
  indiscriminate 
  killing 
  by 
  man. 
  Physical 
  

   characters 
  of 
  these 
  detached 
  remnants 
  of 
  an 
  otherwise 
  numerous 
  and 
  

   powerful 
  race 
  are 
  not 
  indications 
  of 
  geographical 
  variation 
  or 
  sub- 
  

   speciation 
  but, 
  rather, 
  of 
  localized 
  degeneration. 
  

  

  Comparisons. 
  — 
  Superficially, 
  the 
  brightly 
  colored, 
  reddish 
  howler, 
  

   Alouaita 
  seniculus, 
  is 
  immediately 
  distinguished 
  from 
  the 
  smaller, 
  

   blackish 
  A. 
  palliata, 
  the 
  only 
  other 
  species 
  of 
  howler 
  found 
  in 
  Colombia 
  

   (and 
  Ecuador). 
  Striking 
  differences 
  in 
  structure 
  of 
  the 
  hyoid 
  bones 
  

   of 
  these 
  species 
  is 
  described 
  in 
  a 
  following 
  section. 
  Cranial 
  characters 
  

   distinguishing 
  the 
  two 
  are 
  not 
  so 
  obvious 
  or 
  so 
  easily 
  defined 
  as 
  external 
  

   and 
  hyoidal 
  ones. 
  In 
  seniculus 
  the 
  skuU 
  is 
  longer 
  and 
  relatively 
  

   narrower, 
  rostrum 
  more 
  projecting, 
  shallow 
  concavity 
  of 
  nasals 
  usually 
  

   evenly 
  curved 
  from 
  tips 
  to 
  between 
  orbits 
  ; 
  in 
  palliata, 
  the 
  rostrum 
  is 
  

   compressed 
  anteroposteriorly, 
  the 
  nasals 
  usually 
  forming 
  an 
  angle 
  

   between 
  orbital 
  and 
  maxillary 
  regions; 
  ratio 
  of 
  zygomatic 
  breadth 
  to 
  

   condylobasal 
  length 
  in 
  seniculus 
  63 
  to 
  77 
  percent 
  (60 
  specimens, 
  

   northern 
  Colombia), 
  in 
  palliata 
  74 
  to 
  83 
  percent 
  (20 
  specimens); 
  

   sphenomaxillary 
  fissure 
  long, 
  well 
  opened 
  in 
  palliata, 
  usually 
  reduced 
  

   or 
  obsolete 
  in 
  seniculus; 
  mesopterygoid 
  fossa 
  in 
  seniculus 
  widely 
  

   opened, 
  the 
  walls 
  nearly 
  parallel-sided, 
  distance 
  between 
  bases 
  of 
  

   hamular 
  processes 
  normally 
  equal 
  to 
  or 
  greater 
  than 
  distance 
  across 
  

   incisors 
  or 
  crown 
  lengths 
  of 
  either 
  P^~* 
  or 
  M^"^; 
  hamular 
  processes 
  

   usually 
  slender 
  and 
  elongate, 
  directed 
  back 
  as 
  well 
  as 
  down 
  with 
  

   tapered 
  tips 
  tending 
  to 
  recurve 
  upward; 
  mesopterygoid 
  fossa 
  in 
  

   palliata 
  narrower, 
  the 
  walls 
  markedly 
  convergent, 
  with 
  distance 
  

   between 
  bases 
  of 
  hamular 
  processes 
  equal 
  to 
  or 
  less 
  than 
  distance 
  

   across 
  incisors 
  or 
  crown 
  lengths 
  of 
  either 
  P^~* 
  or 
  M^~^; 
  hamular 
  proc- 
  

   esses 
  usually 
  short, 
  comparatively 
  broad 
  and 
  bent 
  sharply 
  downward 
  

   with 
  tips 
  expanded 
  and 
  truncate; 
  foramen 
  magnum 
  in 
  seniculus 
  

   usually 
  sub 
  triangular 
  in 
  outline 
  and 
  higher 
  than 
  wide; 
  in 
  palliata, 
  

   foramen 
  magnum 
  usually 
  subcircular 
  or 
  ovate 
  and 
  as 
  wide 
  or 
  wider 
  

   than 
  high, 
  the 
  occipital 
  condyles 
  markedly 
  weaker 
  than 
  in 
  seniculus 
  

  

  