30 BULLETIN: MUSEUM OF COMPARATIVE. ZOOLOGY. 
often in patches, or spots, sometimes occupying nearly the whole of the under 
surface, sometimes wholly wanting ; and in some specimens the upper surface 
also is patched with whitish). Very old examples are paler above with the 
sooty dorsal stripe, less well marked ; younger specimens are darker, often with 
most of the back sooty. 
Measurements (of ten adults, type and topotypes). — 
No. Sex. Total length. Tail vert. Hind foot. Ear. 
10,204 & old adult 270 135 26 21 
10,202 & old ad. 265 128 26 21 
10,218 2 old ad. 265 130 25 21 
10,211 & old ad. 265 125 25 20 
10,199 & ad. 260 126 26 20 
10,225 2 ad. (type) 260 128 26 20 
10,205 & ad. 257 125 26 20 
10,212 & ad. 255 120 26 20 
10,244 Q ad. 255 120 27 21 
10,198 & ad. 252 120 26 21 
Skull, type, adult 9, basal length, 28.8; occipitonasal length, 32.4; zygo- 
matic width, 15.6; mastoid width, 13.6; length of nasals, 13; width of 
nasals, 3.4; length of palatal slits, 6.2; width of palatal slits, 3.2; length of 
palate, to palatal notch, 12.8; to end of pterygoid, 19; length of upper molar 
series, 5; length of single half of mandible, 17.4. 
Remarks. — Peromyscus cacabatus was by far the commonest small mammal 
of the mountain forest belt of the Volcan de Chiriqui. It does not appear to 
occur below 4,000 feet, and extends from thence upward to the limit of the 
life zone it occupies, roughly speaking, about 8,000 feet, 7,500 feet is the 
highest altitude marked on any of the labels. The Mount Chiriqui Peromys- 
cus, is most nearly allied to P. guatemalensis and P. furvus, but is quite dis- 
tinct. It is the most southern member of the genus thus far recorded. 
Nyctomys! nitellinus,? sp. nov. 
Type. — Mus. Comp. Zo0l., No. 10,249, old ad. 9, Boquete, Feb. 8, 1901. 4,000 feet. 
Six specimens, Boquete, 4,000 to 6,000 feet, January, February, and March. 
Characters. — Apparently a very distinct species, though nearest to NV. deco- 
lorus (True) from Rio de las Piedras, Honduras. Color of back, pale and 
yellowish, but decidedly darker than in N. decolorus. Also larger than N. 
decolorus ; tail more hairy; skull much larger, with narrower posterior part; 
1] think all mammalogists must now regard the very well marked Central 
American hairy-tailed Vesper rats, as generically distinct from Rhipidomys. The 
important characters are four instead of six mamme, very slender, short rostrum, 
exceedingly short palatal slits and peculiarly expanded brain case. The syn- 
onymy is: Nyctomys Sauss. 1860; type, NV. sumichrasti ; Myoxomys Tomes, 1861 ; 
type, M. salvini. 
2 Nitellinus, like a dormouse. 
