62 Merriam The Lemmings of the Genus Synaptomys. 



the posterior loop of the last upper molar is longer transversely, and the 

 reentrant angles of the middle and last lower molars are deeper. 



Measurements of type specimen (alcoholic, measured by C. H. M.). Total 

 length, 115; tail vertebrae, 17; hind foot, 17.5. 



Synaptomys (Mictomys) dalli sp. nov. 



Type locality. Nulato, Alaska, No. 10957, $ adult [skeleton from alco 

 hol], U. S. National Museum. Collected February, 1367, by Wm. H. Dall. 



General characters. Similar to M. wrangeli, but differing in cranial char 

 acters. 



Color. Unknown. 



Cranial and dental characters. Skull similar to that of wrangeli, but differ 

 ing in the following particulars: nasals emarginate instead of truncate 

 posteriorly; interparietal much narrower anteroposteriorly and acute at 

 both ends ; brain case broader ; interorbital constriction broader ; zygo- 

 matic expansion slightly larger ; audital bullx much larger and more fully 

 inflated, with corresponding reduction in breadth of basioccipital and 

 basisphenoid ; mandible conspicuously larger, broader, and heavier, particu 

 larly as seen from below ; upper and lower molars conspicuously larger ; 

 middle and last lower molars with reentrant angle on outer side decidedly 

 deeper than in wrangeli, and thus resembling truei; posterior loop of last 

 upper molar as in wrangeli. 



Measurements (estimated from skeleton). Total length, 115; tail verte 

 brae, 22; hind foot, 19. 



General remarks. In looking at the skull of M. d'llli from above and 

 comparing it with the type of M. wrangeli, the only conspicuous differ 

 ences are the greater breadth of the brain case and interorbital constric 

 tion. Looked at from below, the large size of the audital bull?e and molar 

 teeth is striking. On comparing the under jaws, one is also impressed by 

 the disproportionally large size of the mandible and molars of dalli. I 

 have named the species in honor of Dr. William H. Dall, who collected 

 it at Nulato, Alaska, nearly thirty years ago. 



Synaptomys (Mictomys) truei sp. nov. 



Type from Skagit Valley, Washington, No. ^Vi, yg. ad., U. S. Na 

 tional Museum. Collected August 6, 1859, by Dr. C. B. Kennedy (prob 

 ably in mountains bordering Skagit valley). 



General characters. Size and general appearance as in S. wrangeli, but 

 ears slightly longer and color of upper parts more reddish brown. Last 

 lower molar with a deep reentrant angle on outer side. 



Color. Upper parts dull umber brown fading gradually to plumbeous 

 of under parts ; belly hairs tipped with whitish. Tail bicolor, dark 

 above, whitish below. The type and only known specimen is in the 

 molt and in very poor condition ; hence the colors may not be as in the 

 living animal. 



Cranial and dental characters. The skull of the type is nearly destroyed* 

 leaving only the teeth in the broken jaws. The molar loops, both above 

 and below, are much fuller and more bluntly rounded than in innuitus and 



