ALLEN: MAMMALIA. 215 
internal salient angles. The second upper molar consists of three closed trans- 
verse prisms, the outer angles of which are slight 
ing angles of the inner side. The tooth has 
three salient angles on each side. The last 
upper molar is much like the one preceding, but 
the posterior enamel space, which has two small 
and opposite prisms at its anterior end, is pro- 
duced in the long axis of the tooth into a narrow 
heel, with nearly parallel sides. There are there- 
fore six salient angles in this tooth as in the sec- 
ond molar. In the specimen figured, however, 
there are indications of a small additional pair 
of angles, one on the outer and one on the inner 
side of the posterior heel, and this condition I 
also found in a specimen of M. melanogaster. 
The first lower molar has four closed enamel 
spaces the anteriormost with two internal and 
one external prominent projections; the three 
other spaces, are formed by the confluence of 
the prisms of opposite sides into a single trans- 
verse space. The tooth has four external and 
ly in advance of the correspond- 
Microtus (Eothenomys) mucronatus. 
Type No. 7790. C, Enamel pattern of 
right upper molars. D, Enamel pat- 
tern of right lower molars. 
five or even six internal salient 
angles according as the very small antero-internal point is less or more devel- 
oped. The second and third lower molars show each three transverse closed 
spaces, and each has three salient angles on either face. The reentrants of the 
third lower molar are somewhat deeper externally than in M. aurora. 
Measurements: — The type and three oth 
the flesh by the collector, as follows: — 
Total 
No. Length. Tail. 
7789 Type. 144 39 
7790 162 44 
7791 105! 45 
7803 130 37 
er specimens were measured in 
Hind Foot. Sex. 
19 9 ad. 
19 e) 
19 ie) 
19 2 imm. 
The ears of the dried skins measure 11 or 12 mm. in length from the meatus, 
which is 3 or 4 mm. greater than the corresponding dimension in skins of MW. 
melanogaster. 
The skull of the type measures: — greatest length, 26; basal length, 23.8; 
1 Probably a mistake since the skin as made up is quite as 
137 mm. in length. 
large as the other specimens and measures 
