32 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
Skull, type, 2 old adult, basal length, 28 ; occipitonasal length, 32.4: zygo- 
matic width, 18; mastoid width, 13; interorbital width, 11; length of nasals, 
10.6 ; width of nasals, 3.2; length of palatal slits, 4.6 ; width of palatal slits, 
2.2; length of palate, to palatal notch, 12.4; length of upper molar series, 4.8 ; 
length of single half of mandible, 18. 
Remarks. —1 have compared the series of N. nitellinus with the type of 
NV. decolorus and the other species of this group in the United States National 
Museum, and while most nearly allied to the species from Honduras, I find 
excellent specific characters, both external and cranial for the separation of N. 
nitellinus. 
Tylomys watsoni Tuomas. 
O. Thomas, Ann. and Mag. of N. H., 7th Series, IV., p. 278, 1899. 
Type locality. — Bogaba, Chiriqui. 
Four specimens; adult @ and @ andayoung @, Bogaba, July, anda half 
grown young one from Boquete, 5,600 feet, March. 
The specimens from Bogaba are not only topotypes, but were caught on the 
banks of the same stream as the type. 
Measurements of the four specimens — 
No. Sex. Total length. Tail vert. Hind foot. Ear. 
10,254 9 old ad. 455 235 40 27 
10,251 & old ad. 440 235 42 25 
10,252 & yg. Boquete. 380 195 35 22 
10,253 & very yg. 260 125 32 18 
Sigmodon boruce, ALLEN. 
Three adults, Bogaba, July. 
These appear to be identical with Allen’s S. boruce of Boruca, Costa Rica. 
The measurements are — 
No. Sex. Total length. Tail vert. Hind foot. Ear. 
10,287 Q oldad. 280 105 32 19 
10,285 & ad. 260 110 30 1 
10,286 & yg. ad. 245 100 30 18 
Sigmodon austerulus,! sp. nov. 
Type. — Mus. Comp. Zodl., No. 10,288, ad. ¢, Volcan de Chiriqui, June 1, 1901. 
10,000 feet. 
Characters. — About the size of S. boruce; tail longer; pelage much more 
hispid ; colors all much paler; skull similar. 
1 Austerulus, somewhat harsh. 
