210 Fre~tp Museum or Naturat History — Zoétoey, Vor. X. 
able fulvous on the sides of the belly and likewise on the throat; on the 
other the under parts are practically pure white. The upper parts are 
quite as in P. brevicaudus. I see no objection to treating this form, if 
it be a valid one, as a subspecies of brevicaudus, for whatever local 
variations there may be, it is beyond speculation that all are relatively 
recent derivatives of a common stock. The fact of such slight differ- 
entiation in animals from localities so distant from each other is also 
an indication of general continuity of distribution and probable sub- 
specific relationship. 
Measurements of the two adults are: Head and body 250, 243; 
hind foot (dry) 50, 47.5; greatest length of skull 57.8, 60.2. 
Ctenomys opimus Wagner. Tuco-TUCco. 
One specimen, Oruro. 
This is somewhat immature and noticeably paler than a single topo- 
type of C. opimus with which it has been compared: Thomas* has 
referred specimens from Oruro to this species and has specially men- 
tioned a wide color variation among individuals from one locality, so 
our specimen probably has no extraordinary peculiarities. It is to be 
remembered, however, that rodents of fossorial subterranean habits 
are usually subject to much local differentiation, and when our know- 
ledge of the tuco-tucos is on a par with that of their North American 
analogues, the Geomyidz, we will doubtless recognize ‘a much larger 
number of forms than at present. 
Cavia musteloides boliviensis Waterhouse. BOLIVIAN CAvy. 
Twenty-four specimens, Parotani. 
A series of this size all taken at one time and place affords a valuable 
opportunity to observe variation, especially since such series thus far 
have seldom been preserved. In both color and cranial features con- 
siderable variation appears; rather more, generally speaking, than is 
found among cricetine and murine rodents. The color of the upper 
parts is relatively uniform throughout the series, the general tone being 
slightly darker or lighter according as the buffy annulations of the 
black-tipped hairs are narrower or broader. The broad, basal color of 
the hairs of the upper parts varies narrowly between shades of mouse 
gray and smoke gray always being darker mid-dorsally than laterally. 
The color of the under parts ranges from pale buff or creamy to the 
roots of the hairs (except on the throat) to creamy whitish with a dark 
grayish undercolor extending throughout except on the inner sides of 
the legs where the hairs are pale and self-colored. This latter type is 
*Ann. & Mag. Nat. Hist., (7), LX, p. 227, 1902. 
