'\'914^] ALLEN — MAMMALS 65 



The molars are not very dissimilar in pattern to those of M. arvalis, of 

 which this species may prove to be a geographical race. The last upper 

 molar has four salient angles on the lingual and three on the labial side, 

 though in some specimens there is a minute fourth angle indicated on the 

 outer side posteriorly. The first lower molar has four deep re-entrants on 

 the inner side, and three on the outer side, the anterior-most of which is 

 broadly rounded. There are four closed triangles in front of the posterior 

 transverse loop, while the anterior loop is rounded externally but nearly 

 bisected by the first re-entrant on its inner side. There is a pronounced 

 tendency toward the formation of separate triangles in the anterior lobes 

 of the last lower molar through the antero-internal prolongation of the 

 outer enamel folds. 



Measurements. — The type was measured by the collector, as follows: 

 total length, 188 mm. (head and body 136.5); tail, 51.5; hind foot, 21.5. 

 The skull measures: condylobasal length, 30; palatal length, 16.2; dia- 

 stema, 9.9; zygomatic breadth, 17; interorbital constriction, 3.8; mastoid 

 breadth, 14; maxillary tooth-row, 7; mandibular tooth-row, 6.8; audital 

 bulla, 9.6X5.9; height from top of brain-case, through bulla, 10.4. 



Remarks. — I am unable to refer the Kolyma meadow mouse to 

 any of the various species recorded from eastern Siberia, and there- 

 fore venture to describe it as new. The small, yellowish M. kamt- 

 schaiicus is a wholly different animal, without the tendency to form 

 triangles in the last lower molars. Through the kindness of Mr. 

 Gerrit S. Miller, Jr., I have been enabled to make comparison with 

 specimens of this species from Petropaulski, Kamtchatka, as well 

 as with the type, in alcohol, of M. tshuktshorum, which came from 

 Plover Bay, East Siberia. The latter, as the skull shows, is an 

 immature animal; yet, as compared with equally immature speci- 

 mens of M. koreni, it differs remarkably in its relatively undeveloped 

 palate, without lateral bridges, as well as in its smaller audital 

 bullae. 



Sciurus vulgaris subsp. ? 



A single squirrel was brought back, which, in view of the great 

 variation in color of this species, I have refrained from assigning 

 to any of the Eastern forms. It is nearest S. v. calotus or mant- 

 churicus, though apparently somewhat smaller than the latter 



