32 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



Skull, type, 9 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. — I have compared the series of N. nitellinus with the type of 

 N. 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 Thomas. 



0. Thomas, Ann. and Mag. of N. H., 7th Series, IV., p. 278, 1899. 



Type locality. — Bogaba, Chiriqui. 



Four specimens; adult $ and 9 and a young ^, Bogaba, July, and a half 

 grown young one from Boquete, 5,600 feet, IVIarch. 



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 — 



Sigmodon borucae, Allen. 



Three adults, Bogaba, July. 



These appear to be identical with Allen^s S. borucce of Boruca, Costa Rica. 

 The measurements are — 



Sigmodon austerulus,^ sp. nov. 



Type. — Mus. Comp. Zool., No. 10,288, ad. ^, Volcan de Chiriqui, June 1, 1901. 



10,000 feet. 



Characters. — About the size of S. boriicce ; tail longer; pelage much more 

 hispid ; colors all much paler ; skull similar. 



1 Austerulus, somewhat harsh. 



