40 Bulletin American Museum of Natural History. [Vol. XIV. 



Chapm.) from the Island of Trinidad, but it differs from it in 

 being fully one third smaller and very much paler in coloration. 



Sigmodon simonsi, sp. nov. 



Type, $ ad., Eten, coast region of northwestern Peru (alt.) 10 to 15 m., 

 Sept. 6, 1899 ; coll. P. O. Simons. Collector's No. 552. Type in British 

 Museum. 



Above pale buffy gray varied with black-tipped hairs ; sides of head below 

 eyes, and a well defined eyering, clear buff ; nose and sides of muzzle pale 

 ochraceous buff ; whole underparts pale buff ; ears finely haired, colored exter- 

 nally like the surrounding pelage, buff internally ; upper surface of fore and 

 hind feet pale buff, the hind feet a little darker than the fore feet ; tail well 

 covered with short stiff hairs, dusky brown above, lighter and more buffy brown 

 below. 



Measurements.^ Type, head and body, 155mm.; tail, 100 ; hind foot, 29; 

 ear, 23. Five adult specimens (4 males, i female) measure : Head and body, 

 151 (134-164) ; tail, 98 (93-100) ; hind foot, 30 (29-31) ; ear, 21 (20-23). 



Skull. Posterior border of palate thickened and depressed ; rostral portion 

 of skull convex, the nasals markedly decurved anteriorly ; skull in general 

 broad and heavily ossified. Dentition very heavy. Total length, 35.7 ; basal 

 length, 23.5 ; palate, 16 ; nasals, 12.4 ; zygomatic breadth, 20.3 ; mastoid 

 breadth, 14.7 ; interorbital breadth, 6 ; palatine foramina, 7x2; upper molar 

 series, 7. 



This species is based on a series of five specimens collected at 

 Eten, coast region of northwestern Peru, in September and Octo- 

 ber, 1899, by Mr. P. O. Simons, after whom the species is named. 

 They are all practically adult, and all males except one. 



Sigmodon simonsi \s very distinct from any previously described 

 species of the genus from South America. In the pale colora- 

 tion of the dorsal surface it most nearly resembles S. hispidus 

 texianus, and in the buffy ventral surface recalls S. minimus 

 Mearns from Arizona, and S. fulviventer Allen from western 

 Mexico. Its nearest geographical representative is S. peruanus 

 Allen, from which it differs in the much broader and heavier 

 skull of the latter, and also very strongly in coloration. S. 

 simonsi is obviously a pale, desert type, while S. peruanus is as 

 deeply colored as S. bogotensis or S. sancta-marta. S. peruanus is 

 very unlike the two last-named species, however, in cranial char- 

 acters. S. bogotensis and S. sancta-martce, it may be added, prove 

 to be very closely related inter se. 



1 By the collector, from fresh specimens. 



