﻿G08 
  On 
  new 
  Mammals 
  from 
  the 
  Lower 
  Amazons. 
  

  

  This 
  is 
  only 
  the 
  fifth 
  recorded 
  specimen 
  belonging 
  to 
  the 
  

   rare 
  genus 
  Mesomys. 
  The 
  species 
  will 
  probably 
  prove 
  to 
  

   range 
  the 
  whole 
  length 
  of 
  the 
  River 
  Tocantins, 
  just 
  as 
  

   M. 
  ecaudutus 
  would 
  appear 
  to 
  occur 
  from 
  the 
  Huallaga 
  to 
  the 
  

   mouth 
  of 
  the 
  Amazon. 
  

  

  Kerodon 
  palustris, 
  sp. 
  n. 
  

  

  Allied 
  to 
  K. 
  spixi 
  and 
  K. 
  boliviensis. 
  

  

  General 
  colour 
  above 
  near 
  " 
  wood-brown 
  " 
  about 
  as 
  in 
  

   pale 
  little-annulated 
  specimens 
  of 
  K. 
  spixi, 
  the 
  light 
  mark 
  

   on 
  the 
  head 
  behind 
  the 
  ear 
  practically 
  obsolete. 
  Under 
  

   surface 
  soiled 
  whitish, 
  or 
  pale 
  isabella, 
  little 
  contrasted 
  with 
  

   the 
  colour 
  of 
  the 
  flanks 
  ; 
  very 
  different 
  to 
  the 
  white 
  of 
  

   K. 
  spixi 
  and 
  more 
  as 
  in 
  K. 
  boliviensis 
  ; 
  the 
  hairs 
  pale 
  slaty 
  

   basally, 
  dull 
  creamy 
  terminally. 
  

  

  Skull 
  in 
  general 
  shape 
  most 
  like 
  that 
  of 
  K. 
  spixi; 
  nasals 
  

   parallel-sided 
  ; 
  interorbital 
  region 
  broad 
  and 
  flat 
  ; 
  median 
  

   vertical 
  ridge 
  on 
  supraoccipital 
  obsolete; 
  anterior 
  border 
  of 
  

   mesopterygoid 
  fossa 
  intermediate 
  between 
  the 
  broad 
  opening 
  

   of 
  K. 
  spixi 
  and 
  the 
  narrow 
  one 
  of 
  K. 
  boliviensis 
  ; 
  in 
  K. 
  spixi 
  

   the 
  front 
  edge 
  of 
  the 
  fossa 
  corresponds 
  nearly 
  with 
  either 
  end 
  

   of 
  Ridgway's 
  " 
  elliptical 
  oval 
  " 
  (pi. 
  xvi. 
  fig. 
  10), 
  while 
  in 
  the 
  

   present 
  animal 
  it 
  is 
  as 
  in 
  the 
  right 
  half 
  of 
  u 
  elongate 
  ovate" 
  

   (tig. 
  5). 
  Bullas 
  smaller 
  than 
  in 
  either 
  of 
  the 
  allied 
  species. 
  

  

  Incisors 
  completely 
  deep 
  yellow 
  (" 
  orange-buff 
  ") 
  in 
  front, 
  

   the 
  allied 
  species 
  having 
  them 
  whitish 
  on 
  their 
  outer 
  half, 
  

   and 
  the 
  yellow 
  part 
  paler 
  ; 
  their 
  section 
  comparatively 
  shallow, 
  

   as 
  in 
  boliviensis, 
  their 
  depth, 
  from 
  front 
  to 
  back, 
  but 
  little 
  

   greater 
  than 
  the 
  breadth 
  of 
  either 
  of 
  them. 
  

  

  Dimensions 
  of 
  the 
  type 
  (measured 
  in 
  the 
  flesh) 
  : 
  — 
  

  

  Head 
  and 
  body 
  225 
  mm. 
  ; 
  hind 
  foot 
  46 
  ; 
  ear 
  25*5. 
  

  

  Skull: 
  greatest 
  length 
  55; 
  condylo-incisive 
  length 
  47'7 
  ; 
  

   greatest 
  breadth 
  30 
  ; 
  nasals 
  21x9; 
  interorbital 
  breadth 
  11*6 
  ; 
  

   palatilar 
  length 
  23*2 
  ; 
  breadth 
  of 
  mesopterygoid 
  fossa 
  4*8 
  ; 
  

   upper 
  tooth-series 
  (crowns) 
  11*7. 
  

  

  Ilab. 
  Cameta, 
  Lower 
  Tocantins. 
  

  

  Type. 
  Adult 
  female. 
  B.M. 
  no. 
  11.4.28.34. 
  Original 
  

   number 
  02. 
  Collected 
  3rd 
  January, 
  1911, 
  by 
  Fraulein 
  Dr. 
  

   F. 
  Snethlage; 
  presented 
  by 
  the 
  Goeldi 
  Museum, 
  Para. 
  

  

  From 
  K. 
  spixi, 
  to 
  which 
  on 
  geographical 
  grounds 
  this 
  cavy 
  

   might 
  have 
  been 
  expected 
  to 
  be 
  most 
  allied, 
  it 
  differs 
  by 
  its 
  

   slender 
  incisors, 
  narrower 
  and 
  differently 
  shaped 
  mesoptery- 
  

   goid 
  fossa, 
  much 
  smaller 
  bullae, 
  and 
  less 
  white 
  underside 
  — 
  in 
  

   some 
  of 
  which 
  characters 
  it 
  shows 
  affinity 
  with 
  K. 
  boliviensis. 
  

  

  