﻿56 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM 
  vol.98 
  

  

  Macruroryzomys, 
  new 
  subgenus 
  (genus 
  Oryzomys) 
  

  

  Type 
  species. 
  — 
  Nectomys 
  hammondi 
  Thomas, 
  Ann. 
  Mag. 
  Nat. 
  Hist., 
  

   ser. 
  8, 
  vol. 
  12, 
  p. 
  570, 
  19i;3 
  (type 
  locality, 
  Mindo, 
  Pichincha 
  Province, 
  

   northwestern 
  Ecuador) 
  ; 
  Hershkovitz, 
  Mus. 
  Zool. 
  Univ. 
  Michigan 
  

   Misc. 
  Pnbl. 
  No. 
  58, 
  pp. 
  21, 
  22, 
  81, 
  1944. 
  

  

  Description 
  of 
  type 
  species. 
  — 
  A 
  large, 
  extremely 
  long-tailed 
  member 
  

   of 
  the 
  genus 
  resembling 
  Nectomys 
  alfari 
  in 
  color 
  and 
  character 
  of 
  

   pelage 
  ; 
  fifth 
  hind 
  toe, 
  without 
  claw, 
  extending 
  to 
  base 
  of 
  second 
  pha- 
  

   lanx 
  of 
  fourth 
  toe; 
  other 
  external 
  characters 
  as 
  originally 
  described. 
  

   Nasals 
  broad 
  in 
  front, 
  not 
  markedly 
  tapering 
  behind, 
  the 
  posterior 
  

   borders 
  meeting 
  obtusely; 
  zygomatic 
  plate 
  wide 
  but 
  only 
  slightly 
  

   forward-projecting 
  as 
  seen 
  from 
  above; 
  supraorbital 
  region 
  nearly 
  

   parallel-sided, 
  the 
  edges 
  slightly 
  raised 
  and 
  overhanging; 
  interparietal 
  

   large; 
  walls 
  of 
  sphenopalatine 
  fossa 
  not 
  fenestrated; 
  palate 
  compara- 
  

   tively 
  simple, 
  the 
  posterolateral 
  fossae 
  and 
  pits 
  but 
  little 
  developed. 
  

   Molars 
  large, 
  cusps 
  high, 
  the 
  folds 
  between 
  narrowly 
  compressed 
  but 
  

   open 
  at 
  the 
  crown 
  margins 
  ; 
  first 
  internal 
  folds 
  present 
  in 
  uj)per 
  and 
  

   lower 
  molars, 
  the 
  second 
  internal 
  folds 
  in 
  the 
  lower 
  molars 
  only 
  ; 
  no 
  

   discreet 
  anterior 
  median 
  fold 
  evident; 
  minor 
  folds 
  of 
  Mi_3 
  well 
  

   developed. 
  

  

  M 
  ecLSurements 
  of 
  the 
  type 
  (in 
  millimeters). 
  — 
  Head 
  and 
  body, 
  203; 
  

   tail, 
  251; 
  hind 
  foot, 
  32; 
  ear, 
  18; 
  condylobasal 
  length, 
  38.8; 
  zygomatic 
  

   breadth, 
  21.2; 
  length 
  of 
  nasals, 
  16.0; 
  alveolar 
  length 
  of 
  molar 
  row, 
  

   6.9; 
  least 
  interorbital 
  breadth, 
  6.9; 
  width 
  of 
  zygomatic 
  plate, 
  5.0; 
  

   interparietal, 
  5.4X10.9; 
  width 
  across 
  parietal 
  ridges, 
  14.0; 
  incisive 
  

   foramina, 
  3.3X6.3; 
  crown 
  dimensions 
  of 
  first 
  upper 
  molar, 
  2.3X3.1. 
  

  

  Remarks. 
  — 
  The 
  Costa 
  Rican 
  Oi^zomys 
  aphrastus 
  Harris 
  (Mus. 
  

   Zool. 
  Univ. 
  Michigan 
  Occ. 
  Pap. 
  No. 
  248, 
  p. 
  5, 
  1932) 
  is 
  probably 
  most 
  

   nearly 
  related 
  to 
  O. 
  harmnondi. 
  

  

  LITERATURE 
  CITED 
  

  

  EteRSHKOVITZ, 
  Philtp. 
  

  

  1944. 
  A 
  systematic 
  review 
  of 
  the 
  Neotropical 
  water 
  rats 
  of 
  tlie 
  genus 
  

   Nectomys 
  (Cricetinae). 
  Mus. 
  Zool. 
  Univ. 
  Michigan 
  Misc. 
  Publ. 
  No. 
  

   58, 
  88 
  pp., 
  4 
  pis., 
  5 
  figs., 
  2 
  maps. 
  

  

  o 
  

  

  