Oct., 1916. Mammats, Cottins-Day Expepition —Oscoop. 207 
there is tendency for the hairs to have dark bases, the throat, axille, 
and inguinal regions being always white to the roots of the hairs. In 
one old female the entire under parts are pure snowy white sharply 
separated from the upper parts by a broad (5 mm.) tawny ochraceous 
lateral line. Both fore and hind feet are more or less brownish, and the 
ears, while usually tawny, are sometimes dusky antero-internally. 
Two adults present the following flesh measurements: Total length 
333, 328; head and body 149, 147; tail 184, 181; hind foot 27, 27. 
Hesperomys callosus boliviz Thomas. 
One specimen, Trinidad. 
On geographic grounds, this specimen might be either H. callosus 
or H. c. bolivig; and with nothing more than descriptions for com- 
parison, its identification cannot be regarded as positive. The tooth- 
row measures 4.1 mm., which is exactly the length given for that of the 
type of H. c. bolivie, and other cranial measurements correspond 
closely. External measurements are as follows: Total length 200; 
head and body 122; tail 78; hind foot 23. ’ 
Phyllotis (Graomys) domorum Thomas. 
Three specimens, Parotani. 
- These are typical examples of this species and from the region of 
the type locality. Their examination has been of particular interest in 
connection with the grouping of certain South American Muridz 
recently made by Thomas.* A small group including the present species 
has been given generic rank under the name Graomys, but this group 
is so closely allied to typical Phyllotis that it seems better to treat it as 
a subgenus rather than as a genus. This conclusion is largely influenced 
by a consideration of Phyllotts amicus, a species which is assigned infer- 
entially by Thomas to Phyllotis but which shows such affinity to 
Graomys that the exceedingly close relationship between the two 
groups can scarcely be doubted. In all external features except size 
the resemblance of P. amicus and P. domorum amounts to practical 
identity. The very soft, satiny pelage and the pure white self-colored 
areas of the under parts are very characteristic. The skull of P. 
amicus has the short, rounded braincase of typical Phyllotis but its very 
broad frontals and its slightly undercut zygomatic plate show very — 
decided approach to the condition in Graomys. It lacks the definite 
supraorbital bead but the supraorbital border is trenchant and even 
slightly elevated. The second upper molar is more nearly five-parted 
than in true Phyllotis, and in this respect also there is resemblance to 
*Ann. & Mag. Nat. Hist., (8), XVII, pp. 139-143, Jan., 1916. 
