604 MURIDAZ—EPIMYS 
Remarks :—The following measurements from Hossack (of. czz., 9) 
illustrate the changes of bodily proportions which transpire with 
growth :— 




Percentages of head and body length. 
Head and 
body. 
Tail. Hind foot. Ear. 
EL. rattus, juvenile : 4 95 = 100 147°3 31°5 18°9 
Do. do: 5 . 100 = 100 145 29 19 
Do. do. . . 105 = 100 128°5 27°6 1671 
Do. adult . . c 173 = 100 121 19°1 1271 

Weight :—Two captive male alexandrinus (or frugivorus) weighed 
4 and 5 ounces, or 113-3 and 141-6 grammes respectively; a female 
E. r. rattus in captivity. weighed 5-25 ounces, or 148-5 grammes 
(Millais, ii, 208). The weights recorded by Eagle Clarke vary between 
139-4 and 215-5 grammes, but as will be seen from the above table 
these weights are not those of the largest individuals enumerated. 
It is, however, improbable that the weight ever much exceeds 300 
grammes; full-grown specimens of xorvegicus frequently weigh from 
450 to over 500 grammes. This great difference fully explains the 
inability of xa¢tws to withstand its rival. 
Skull :—Condylo-basal length, 38 to 45; zygomatic breadth, 19-2 
to 22; interorbital constriction, 5-8 to 6-4; occipital breadth, 15 to 
17-2; depth of brain-case at middle, 10-8 to 12-6; length of nasals, 
14 to 17; of diastema, 10-2 to 13; of mandible, 23-2 to 28; of maxillary 
tooth-row, 6:4 to 7-4; of mandibular tooth-row, 6-2 to 7-2. 
Distinguishing characters:—All the sub-species of #. vattus are 
best distinguished from all forms of xorvegicus by their lightness, 
elegant build, longer tails, and larger and much more delicate ears. 
The adult skull has larger bullz, and presents well-marked distinctions 
in the parietal and interparietal regions, as described above. 
Habits:—A general account of the habits of rats is given below 
under E. xorvegicus. The Black Rat is essentially a climber,! and does 
not burrow under houses or infest drains like its rival; it shows no 
liking for water, which it perhaps only enters occasionally, as when 
danger presses. As compared with the Brown Rat, it is doubtless in 
the main a clean feeder—possibly evidence of its more salubrious 
station rather than of a nicer or daintier palate. Lataste (313) says 
that it is by no means mute. Observers differ as to its odour, for 
while de l’Isle (184) describes it as more odorous and fetid than 
norvegicus, Adams (MS.) states it to be without the offensive smell of 
the latter species. 
According to Shipley,? this species does not breed before it has 
1 Hossack describes it as scampering upside down along the cage wires. 
2 Journ. Econ. Biol., iii., 1908, 62. 
