The Lemmings of the Genus Synaptomys. 



63 



wrangeli, and the reentrant angle on the outer side of the last lower molar 

 is much deeper and nearly forms a closed loop on the outer side of that 

 tooth. The upper incisor is narrower and the sulcus shallower than in 

 the other known species. 



Measurements (from dry skin). Total length, about 112; tail vertebne, 

 22 ; hind foot, 18. 



General remarks. Mictomys -truei differs markedly from the two other 

 species now known in the fullness of the molar loops and the depth of 

 the reentrant angle on the outer side of the last lower molar. I have 

 named the species in honor of Mr. F. W. True, curator of mammals in 

 the U. S. National Museum. 



Syiiaptomys (Mictomys) wrangeli sp. nov. 



Type from W ran gel, Alaska, No. 74720, r$ ad., U. S. National Museum, 

 Department of Agriculture collection. Collected September 0, 1895, by 

 Clark P. Streator. Original number 4871. 



General characters. Similar to S. innuitus, but larger ; tail and hind foot 

 longer ; skull narrower. 



Color. Upper parts grizzled grayish brown, with a yellowish cast; 

 under parts plumbeous, tippid with whitish ; tail bicolor, brownish above, 

 whitish below, darker at tip. 



Cranial and dental characters. The skull of Mictomys wrangeli, contrasted 

 with that of M. innuitus, is nar 

 rower and higher; the zygomata 

 narrower and less spreading ante 

 riorly ; brain case narrower and 

 less depressed; audital bullse less 

 inflated anteriorly. The posterior 

 loop of the last upper molar is 

 much shorter ; the reentrant angle 

 on outer side of last lower molar 

 shallower, and the enamel folds of 

 all the teeth more loosely spaced. 



Measurements (taken in flesh). 

 Type specimen : total length, 122 ; 

 tail vertebnfe, 23; hind foot, 19. 



FIG. 5. Skull of Mictomys wrangeli 

 (type) X i%. 



Average of two specimens from type locality: total length, 119.5; tail 

 vertebrae, 22.5 ; hind foot, 19. 



BIBLIOGRAPHY. 



Titles of Papers Containing Original Matter Relating to the Genus Synaptomys. 



1. 1857. Baird, Spencer F. Mammals of North America, 1857. Orig 



inal description of genus Synaptomys and species S. cooperi 

 (pp. 556-558). 



2. 1874. Cones, Elliott. Synopsis of Muridae. <Proc. Acad. Nat. Sci., 



Phila., pp. 173-196, 1874. Description and record of locali 

 ties (pp. -192-194). 



10 Bior,. Soc. WASH., VOL. X, 1896 



