MAMMALS OF NORTHERN COLOMBIA—HERSHKOVITZ 137 
brown mixed with buffy, cheeks buffy, eyes ringed with dark brown. 
Tail black above, white beneath. 
Measurements (in millimeters).—Those of the holotype followed by 
the means and extremes of the adults of the type series, including the 
holotype. Head and body, 239, 243 (217-278, ten specimens); tail, 
164, 173 (150-192, seven specimens); hind foot, 51, 50.6 (45-53, 
ten specimens); ear, 24, 25 (22-28, nine specimens); greatest length 
of skull, 59.2, 57.3 (52.3-63.4, eleven specimens) ; zygomatic breadth, 
26.4, 26.3 (24.7-28.4, eight specimens); length of nasals, 22.0, 21.5 
(20.0-23.5, eleven specimens); alveolar length of molar row, 8.7, 8.3 
(7.8-8.9, twelve specimens). 
Coloration of the paratypes.—More brightly colored than any of the 
Colombian races of guyannensis found east of the Rio Magdalena. 
As usual in the species, the individual becomes paler as it becomes 
older. Subadults acquiring the spiny pelage show more black on the 
back. With the establishment of the adult pelage, the black terminal 
portions of the spines become less prominent as the ochraceous bands 
of the soft hairs become broader, the hairs themselves, longer. In all 
specimens the underparts are sharply defined white, the hind feet 
white more or less marked with brown. 
Remarks.—Of the races of guyannensis found west of the Rio Mag- 
dalena in Colombia, and in western Ecuador and Central America, 
only the extremely pale decumanus of Ecuador is markedly different 
in external characters. Cranially there is little basis for making dis- 
tinctions. In the enamel pattern they all agree in having three folds 
in the lower molars, while some of the Central American forms in- 
cluding panamensis, and calidior of western Ecuador, tend to retain 
the fourth fold in the last two upper molars, and in the lower pre- 
molar. In dental characters, magdalenae shows its nearer relation- 
ship to the western forms than to mincae and chrysaeolus which are 
much nearer geographically, but on the opposite side of the Ria 
Magdalena. 
Specimens examined.—Nineteen (13 males, 6 females) all in the 
collection of the United States National Museum. Rio San Pedro, 
17 (one with skull only); Norosi, 2 (one with skull only). 
PROECHIMYS HENDEEI Thomas 
Proechimys hendeei Tuomas, Ann. Mag. Nat. Hist., ser. 9, vol. 18, p. 162, 1926 
Type locality—Puca Tambo, Chachapoyas district, Amazonas, 
Peru. 
Distribution (of the species).—Known only from the Amazonian 
region of Ecuador and Peru. 
Characters (of the species)—Upperparts ochraceous to tawny 
with a mixture of black, the median dorsal area more or less as in 
guyannensis but with spines weaker, less prominent. Underparts, in 
