MUS EATTUS. 
275 
Measurements taken from specimens of the smaller form preserved in alcohol. 
Eayum. 
Minia. 
Beltim. 
c?. 
?. 
6. 
$. 
mm. 
mm. 
mm. 
mm. 
Head and body . . 
165 
152 
152 
Tail. 
200 
197 
195 
Hind foot . . . . , 
30 
32-5 
35 
Ear.. 
22 
22*5 
22 
Dr. Andrews gives the following measurements 
taken in the flesh 
of three large 
specimens from Cairo :— 
6 . 
cJ. 
ct. 
mm. 
mm. 
mm. 
Head and body 
210 
195 
Tail. 
270 
245 
Hind foot .... 
38 
38 
Ear. 
24 
26 
23 
Long hair on baek . 
43 
58 
55 
Measurements of skulls. 
Cairo. 
Fayum. 
r 
A 
! 
_A-, 
C?. 
C?. 
d • 
mm. 
mm. 
mm. 
mm. 
Greatest length . . . 
45-5 
39-5 
39-5 
„ breadth . . 
22 
19-5 
20-5 
Ereadth of brain-ease . 
. 18 
17-5 
16-5 
16-5 
Length of nasals 
16-5 
13-7 
14 
Basal length .... 
40-5 
35 
35 
Length of palate . . 
22-5 
18-5 
18-5 
Incisive foramina . . 
8 
7-3 
7 
jMolar series .... 
7 
6'5 
6-5 
Ereadth outside molars 
• ••••• 9 
9 
7-7 
8T 
The two Fayum skulls 
are from older animals 
than those 
of the larger Cairo 
specimens. 
Ihe brain-case of Mus rattus is much more rounded than that of the following, 
M. norvegiciis. The parietal ridges for the attachment of the masseter muscles are 
somewhat bowed outwards ; the angles formed by these ridges and the supraorbital 
ridges are on the fronto-parietal suture. The molars are narrower, the ear-conchs 
rounder. The incisive foramina slightly overlap the front molars ; these foramina are 
alike in shape in both species, being about the same width in front and behind, and 
convexly expanding in the middle, with the median septum fairly strong throughout ; 
the palate is slightly narrower in this species than in the following.—W. E. de W. 
2 N 2 
