THE BANK MOUSE 411 
of 81; another of 85 contained two embryos. At about 85 adult pelage 
is assumed, and from 90 upwards the majority are sexually mature. 
Many grow on to a much greater size, 
and, in exceptional cases, females have 
been found to be sexually immature at 
97 or 99. It is not clear whether dimen- 
sions exceeding 100 are abnormal, or 
whether every individual would reach 
that size if not previously destroyed. 
Apparently they continue to grow for 
a long time, and Millais finds that all 

Microte improve considerably in colour Cake 
and size until they are two years old. 
There is nothing to show that the sexes ‘4 B 
differ constantly in size. Fic. 63.—CHEEK-TEETH OF LZvotomys 
Skull :—Condylo-basal length, 21-2  séomerensis (A, right upper; 8, left 
fomen-2 breadth at zyeomata, 12-2\fo. (towers 7 times life. size). (Drawn) by 
2 ; een M. A. C. Hinton.) 
14; at inter-orbital constriction, 3-6 to 
-2; at occiput, 10-7 to 11-8; median occipital depth, 5-8 to 6-4; greatest 
length of nasals, 5-6 to 7-4; of diastema, 5-6 to 7-2; of mandible, 12:8 
to 14:8; of maxillary tooth-row, 4:8 to 5:6; of mandibular tooth-row, 
4:8 to 5-4. 
Distinguishing characters:—As between mice of this genus and 
others of similar size, the hairy, bicoloured tail is probably the 
most distinctive external character. Its length, about half that 
of the head and body, is greater than that of any JMzecrotus, 
shorter than that of any member of the sub-family Murzne. In the 
skull the simple palate, rooted cheek-teeth with rounded salient angles, 
and transversely open triangles of #, are diagnostic. The characters 
of the other species of Hvotomys are given under their special headings. 
The Bank Mouse’ is not specialised by its structure 
for a narrow type of existence. Its habits are, therefore, of 
comparatively wide range, but not strikingly peculiar in any 
particular direction. It may be found in all the situations 
ordinarily affected by Grass Mice or Field Mice, without, how- 
ever, adopting the extreme role of either. In demeanour and 
activity it is quite intermediate, being less fossorial, but much 
more rapid and agile in all its movements, than the Grass 
1 Of earlier original accounts that of E. R. Alston, in Bell’s second edition, 
usually, but incorrectly attributed to Bell himself, is, considering the date, 1874, 
perhaps the best. Other original accounts are those of G. T. Rope, Sciezce Gossip, 
July 1886, 155-7 ; and of Douglas English, Some Smaller British Mammaz/s (undated). 
