5 
: Measurements. M. 
Depth of cranium at M. 2... ..ce.c. cee ceeecceeee seve 0138 
Length of molar series along base...... aa NaddN coe -.» .0080 
Diameter of second molar { antero-posterior........... .0016 
LUNSVEIS Ci iace ose 5 aes ee -0020 
Width of face of superior incisor........... ea ttaccmen 20020 
MENTIscomMys HIPPODUS, Zen. et sp. nov. 
Gen. Chur, The characters of this genus are derived from the dentition 
of both jaws, and from portions of the cranium which are preserved. The 
molars are rooted, and number +. Those of the superior series are with- 
out enamel inflections, and the triturating surface exhibits two external 
and one internal crescentic sections of the investing enamel. On the sec- 
ond superior molar there are three external crescents in the typical species ; 
and the first molar is simply conic. Between the inner and external cres- 
cents, there are the curved edges of enamel plates directed obliquely and 
transversely. The grinding surfaces of the inferior molars display in the 
unworn condition, two L-shaped transverse crests, connected longitu- 
dinally on the median line ; on wearing. the lateral emarginations of the 
enamel become shvllower, disappearing from the inner side, but remaining 
on the outer. Incisor teeth not grooved. Hurameninfraorhitale anterius, 
if present, elevated in position and near orbit. 
The characters of the dentition of this genus resemble those of the genus 
Pteromys, which is now confined to Asia and the Malaysian Archipelago. 
The superior molars differ from those of Pleromys in wanting all reéntrant 
enamel inflection. Specimens in my collection indicate two species of 
Miniscomys. 
Spectf. Char, Superior molars with a vertical ridge from the points of 
junction of the crescents on the external side; there are thus two on the 
second molar, and one each on the third and fourth. Within each of the 
external crescents is another crescentic edge of a pair of vertical enamel 
plates, and the inner marginal crescent sends off a short transverse branch 
towards them. With attrition, all these crests unite by their extremities, 
enclosing four distinct lakes, which, after still further wear, disappear. 
Attrition produces a similar result in the inferior molars, viz.: two pairs of 
crescents enclosing four lakes, which ultimately wear out. The inferior 
incisor has a shallow concavity on its anterior face. 
The maxillary bone, anterior to the molar teeth, is shorter than the pre- 
maxillary. The incisive foramina are entirely in the latter. The sides 
and superior aspect of the muzzle are regularly convex in transverse sec- 
tion. The inferior incisive alveolus is enclosed entirely in the plane of the 
ramus, and extends posteriorly to below the last molar tooth. ‘The masse- 
teric ridge is very oblique, and rises to a median point below the second 
molar. The coronoid process rises from the front of the last molar. 
Measurements. M. 
- Length of superior molar series. ............0 0000. .-. 008 
