392 MURIDA2E—LEMMUS 
anterior edge of the inter-pterygoid fossa carried forward 
dorsally past the overhanging edge of the palate. 
In the teeth the ungrooved upper incisors are compara- 
tively slender. The cheek-teeth (Fig. 57) are rootless; their 
tooth-rows converge anteriorly, their crowns are very broad, 
and the enamel-pattern is characterised by reduction of dentine- 
spaces, sharp enamel-angles, and deeply cut infolds ; the latter 
run almost right across #1 and #2 on the outer upper and 
inner lower sides; in some cases they are opposed by salient 
angles presenting a peculiar appearance of square truncation. 
Except where modified by the features just described, 
m and m’ do not differ from those of normal Zicrotine. 
m* is formed of four transverse 
loops ; the first is isolated from 
the second by a deep outer 
fold; the second from the third 
by the approximation of an 
inner and outer fold, the former 
a little deeper ; the third simi- 
larly from the fourth, but the 
inner fold is very deep, the 
outer a mere vestige. 
m, has the posterior loop 
preceded by three closed tri- 
— angles, and an anterior loop 
, formed by the blending of 
two or three reduced dentinal 
Sian com Cates spaces ; it presents three outer 
Lemmus lemmus (73 times life size); fromthe and four inner salient angles. 
a Peas Eee laad Oren ey a agrees in structure with that 
of AMficrotus, and differs merely 
in having the two outer closed triangles relatively small. 
mg is essentially similar; its postero-internal fold is, however, 
deepened, so that it extends practically across the crown, 
and the antero-external triangle of m. is not represented ; there 
is a large foramen below and behind the alveolus. 
The above characters show extreme specialisation in skull 
and teeth, but in external characters Lemmus is not so 
specialised as Decrostonyx. 
= Ae > 
— m — 

