84 
MURIDAE RECORDED FROM VICTORIA 
Size small. General colour varies from greyish-brown to yellowish-brown 
on the dorsal surface, and from brownish-grey to white below. The majority 
show little contrast between the upper and lower surfaces. Ear fairly large. 
Tail about as long as head and body. Manus and pes buffy-white, sparsely 
clothed with brownish-white hairs. 
Skull . — Comparatively broad and flat. Wide in the interorbital region. 
Anterior edge of zygomatic plate sloping gently backwards towards its base. 
Teeth . — First molar large, its length more than M 2 and M 3 combined. 
Wearing surface of upper incisors notched. 
Dimensions of Skin (from flesh). — Head and body, 74 mm. ; tail, 82 mm. ; 
hind foot, 17 5 mm.; ear, 11 5 mm. 
Dimensions of Skull . — Greatest length, 22 3 mm. ; basal length, 19 5 mm. ; 
greatest breadth, 12 mm.; nasals, 7 5 X 2 3 mm.; interorbital breadth, 
4 mm. ; palate length, 115 mm. ; breadth inside M 2 , 3 mm. ; breadth outside 
M 2 , 4' 5 mm.; palatal foramina, 5 mm.; diastema, 5 5 mm.; upper molars, 
3 mm. 
Type Locality. — Europe. 
Tlie teeth characters mentioned above are a simple means of 
separating the European House Mouse from the native mice. 
Molar teeth of the latter are graduated in size, the second 
being only a little smaller than the first, and the incisors have 
a true chisel edge. If the upper lip of the House Mouse be 
lifted, the notched incisors are easily seen. 
Many mouse plagues have occurred in Victoria, and in every 
case they have consisted of this species. Periodically, and 
probably in relation to suitable weather conditions, the fer- 
tility of the mice increases tremendously, and their numbers 
become many hundreds of times more than normal. Food 
supply becomes inadequate, and they commence a migratory 
movement, usually towards the south. Wood J ones also points 
out (Mamm. Sth. Aust., iii, p. 322) that, apart from migra- 
tion, the wave of increased fertility also moves progressively, 
and has been known to affect an island colony to which the 
mainland animals could have no access. At the height of the 
plague millions of mice are on the move. They are preyed 
upon by other mammals and birds, and are trampled in hun- 
dreds under the feet of agricultural workers. Finally starva- 
tion and disease set in, and, as suddenly as they increased, 
numbers return to normal. The amount of damage and the 
monetary loss to the State caused by such incidents cannot be 
calculated, but it must amount to a huge sum. 
