Miller.] 192 [Feb.^, 
presence of three closed or nearly ck^ed outer triangles in the 
posterior upper molar in addition to ^ le usual terminal crescent 
(pi. 4, fig. 2a). Otherwise the pattern of enamel folding shows 
no peculiarities. There are, however, in this respect some inter- 
esting variations. In the posterior upper molar the external 
triangles tend to remain open, comr- nicating more or less broadly 
with those of the opposite sidp '' llis is especially the case with 
the type, though in no one o^ "'.ive adults are these triangles so 
tightly closed as in the averc^eiS. riparias. The specimen from 
Profile Lake differs from all the others in lacking the third outer 
triangle in the posterior upper molar. This I regard as merely 
an extreme case of individu:il variation. Two of the adults (Nos. 
2523 and 2528) are peculiar in having the anterior loop of the 
first lower molar deei)ly cut by an internal re-entrant angle, the 
apex of which reaches nearly across to the enamel of the 
opposite side, making the tooth appear to have four internal 
triangles. 
We found this interesting new Arvicola near the summit of 
Mount Washington and at the outlet of Profile Lake. But one 
specimen was taken at the latter place, so it is impossible to say 
whether the animal is of regular occurrence there. On Mount 
Washington we took eight examples, an adult and four young at 
the Lake of the Clouds, and three adults near the head of 
Tuckerman's Ravine. The first specimen was caught near the 
edge of the Lake of the Clouds on a mound of rock fragments 
beneath which we could hear running water. The mound was 
thickly covered with Carex rigida bigelovii interspersed with 
willows (Salix argyrocarpa) , blueberries ( Vaccinium uliginosutn) , 
raspberries (Rubus trijlorus), and many herbaceous plants sucli as 
Viola palustris, Coptis trifoUa, Geum racUalum peckii, Streptopus 
roseus^ and the like. Near the lower part of the mound and 
between this and the lake a sphagnum (S. girgensohnii stachyodes) 
grew in profusion. Although there could be no doubt that 
numerous mice lived in the mound, all our efforts to trap them 
failed. A few rods away, however, the four young ones were 
secured. At the head of Tuckerman's Ravine we again found 
the animal where a dense turf of Carex covered the bare rocks, 
leaving a labyrinth of cavities beneath through which water was 
flowing. These specimens were all taken in tx-aps set under the 
turf. The mice apparently live wholly in the natural cavities 
