236 PROCEEDINGS OF THE NATIONAL MUSEUM. 



Incisors differing from those of every other member of the genus 

 by being distinctly thrown forward, their angle with the upper tooth 

 row, measured as recently described,^ 84° and 85° in the two speci- 

 mens, while this angle comes out at about 70°-76° in T. gracilis and 

 the other members of the genus examined. Molars as usual. 



Dimensions of type. — Head and body, 92; tail, 133; hindfoot, 23,5; 

 ear, 16. Sloill — greatest length, 27.7; condylo-incisive length, 26.2; 

 zygomatic breadth, 14.2; nasals, 8.5; interorbital breadth, 4.7; 

 breadth of braincase, 13; palatilar length, 12.1; palatal foramina, 

 6.3; post foraminal palate, 5 ; upper molar series (worn), 4.2. 



Type.— Old female from Ocobamba Valley, U.S.N.M. No. 194902. 

 Original number 521. Collected July 29, 1915. 



Two specimens from Ocobamba Valley, 9,100 feet (Nos. 194809 and 

 194902). 



As already noticed, this species is remarkable for the unusually 

 forward set of its incisors, which distinguishes it from every other 

 member of the genus, and probably indicates some difference in its 

 habits, which are perhaps of a more fossorial or at least more defi- 

 nitely terrestrial nature. 



42. THOMASOMYS TACZANOWSKII Thomas. 



One specimen, (No. 194876) from Ocobamba Valley. 



This determination is of necessity somewhat provisional, and can 

 only be settled when modern topotypes are available. The type has 

 been skinned out of spirit, and is much discolored, while its ears are 

 shrunk, as is always the case with specimens so treated. The skulls 

 agree fairly closely, the size being about the same, the nasals simi- 

 larly sinuate along their sides, as in T. notahis, and the bullae 

 similarly larger than in the T. gracilis and the other small species to 

 which this mouse has so strong a general resemblance. 



43. AKODCN SURDUS Thomas. 



1917. Akoclon svrdus TiiouAJi, Sniiiiis. Misc. Coll., vol. 68, No. 4, p. 2. Axiril 

 10, 1917. 



A large, dark-colored siJecics allied to A. mollis. 



Size comparatively large. Build stout and heavy. Fur rather 

 coarse. General color above dark olivaceous gray (near "sepia" 

 Eidgway) ; under surface, soiled grayish, and hairs slaty basally, 

 dull buffy or drab terminally ; line of demarcation vague. 



Ears of medium size, colored like head. Hands and feet grayish 

 brown above, the flesh of the soles blackish. Tail fairly long, finely 

 haired, dark brown, scarcely lighter below. 



Skull (pi. 15, fig. 2) solidly built, its profile evenly convex above. 

 Muzzle thick and heavy. Interorbital region broad, its edges squared. 



^ Ann. and Mag. Nat. Hist., ser. 8, vol. 18, p. .S02, footnote. 1916. 



