1899-] Allen, New Rodents from Colombia and Venezuela. 205 



females, measure as follows: Males, total length, 329 (307-345); tail, 176 

 (162-194) ; hind foot, 32.7 (29-36). Females, total length, 312 (302-333) ; tail, 

 172 (163-182) ; hind foot, 32 (28-34). 



Skull, type, total length, 34.4 ; basal length, 27 ; zygomatic width, 18 ; mas- 

 toid width, 13; interorbital width, 5; length of nasals, 7.6 ; palatal length, 

 7.8 ; length of palatine foramina, 5.5 ; length of upper toothrow, 5.5 ; length 

 of lower jaw (condyle-to incisor tips), 20 ;, height (condyle to angle), 8.5 ; at- 

 coronoid process, 8.5. 



Young in first peLige. Above dark, many of the hairs rufous tipped ; sides 

 of the nose paler and more tinged with rufous ; below dark gray, with irregular 

 patches of white, the general color of the ventral surface passing gradually on 

 the sides into that of the upper surface ; ears, tail, and feet nearly as in the 

 adult, except that the fore limbs are externally like the sides of the body. The 

 ventral patches of white are variable in size and consist usually of a small anal 

 patch and a very large pectoral patch, in which the hairs are white to the base, 

 as in the adults. 



From this early phase there is every gradation to the pelage of the adult. 

 This change is most noteworthy and interesting in respect to the ventral surface, 

 where the original white patches gradually extend till the whole ventral area 

 becomes entirely pure white to the base of the hairs.' Not only do the original 

 white patches increase in extent, but white hairs also become intermixed with 

 the gray of the general surface, so that the original gray becomes veiled with 

 white long before the gray disappears from the basal portion of the pelage. In 

 advanced stages of the change the pectoral patch extends forward to the throat, 

 and backward along the median line of the belly, meeting the enlarging anal 

 patch, at this stage only the lateral portions of the ventral surface remaining 

 gray, more or less strongly veiled with white. The wholly pure white ventral 

 surface seems to be acquired slowly, and, may never be obtained by all individ-. 

 uals, as the percentage of such specimens is small in the present large series, 

 being not over one in seven. The particolored condition of the majority of' 

 even the practically adult specimens has suggested the specific name here- 

 imposed. 



. 



Oryzomys maculiventer seems to be a common species in the 

 Sierra El Libano district,: the present series numbering 47 speci- 

 mens, collected as follows-: Valparaiso, altitude 4500 feet, 13 

 specimens, April i4-June 16, 1899 ;> Sierra El Libano, elevation 

 6000 feet, 34 specimens, May, 1899. 



This is one of .the largest 'members of the genus known, to me, 

 being considerably larger than any species thus far described, 

 from northeastern South America. In cranial characters it 

 resembles O. meridensis Thomas, from M.erida, Venezuela, and it 

 seems also related to O. albigularis (Tomes), from Pallatanga, 

 Ecuador, but is nui^h [larger than -either,. and apparently Differs 



