62 Merriam — The Lemmings of tJie 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. 



Mcamrcmeiitfi of tj/pi' specimen (alcoholic, measured by C. H. M.).— Total 

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



Synaptoniys (Mictomys) dalli sp. nov. 



Ti/pe locality. — Nulato, Alaska, No. 10957, (^ adult [skeleton from alco- 

 hol], U. S. National Museum. Collected February, 1867, by Wm. H. Dall. 



General c/iorw/fr.s.— Similar to M. ivrangeli, but differing in cranial char- 

 acters. 



Color. — Unknown. 



Cranial and dental characten^. — Skull similar to that of ivrangeli, but differ- 

 ing in the following particulars: nasals emarginate instead of truncate 

 jiosteriorly ; interparietal much narrower anteroposteriorly and acute at 

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

 matic expansion slightly larger ; aadital Imllie muck larger and more fully 

 inflated, with corresponding reduction in breadth of basioccipital and 

 basisphenoid ; mandible conspicuoush/ larger, liroailer, and Jwarier, 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 ivrangeli. 



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

 brte, 22; hind foot, 19. 



General remarki<. — In looking at the skull of M. dtlll from above and 

 comparing it with the type of M. ivrangeli, 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 bullae and molar 

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

 the disproportionally large size of the mandible and molars of d(dii. 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. 



Tgpe from Skagit Valley, Washington, No. iViVi, yg- ad., U. S. Na- 

 tional Museum. Collected August 6, 1(S59, by Dr. C. B. Kennerly (prob- 

 ably in mountains bordering Skagit valley). 



Genered, 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 plunil)eous 

 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 dentid characters. — The skull of tiie type is nearly destroyed) 

 leaving only the teeth in the i)r()ken jaws. Tlie molar loops, l)oth above 

 and below, are much fuller and more1)luntly rounded than in innuitns and 



