MURIDZ 377 
are annulated, the basal and major portions being usually dusky. 
The first or juvenal coat of the young is distinct from that of 
adults, and precedes a post-juvenal coat of intermediate 
character. Two moults, one at each change of season, are 
probably normal, but their regularity is much interrupted by 
variable weather, the condition of the animals, and the influence 
of the long breeding season. The system of pigmentation and 
the principles of coat pattern are probably somewhat similar 
throughout the family, but having been chiefly studied in the 
House Mouse, are described under that species. 
Droppings :—These are very distinct from the more or less 
rounded crotties of the Leporide, being elongated, thicker 
in the middle and tapering to blunt points at each end. 
Except in size, they are not distinctive as between the various 
species. 
The British species fall into three sub-families :—the locally 
extinct Cvzcetine, or hamster-like rodents; the J/ccrotine, or 
voles and lemmings ; and the JZur7zez, or true mice and rats. 
A KEY TO BRITISH MURIDA, 
WITH MUSCARDINUS. 
I EXTERNAL CHARACTERS -—— 
I. Size larger (‘‘rats,” with head and body not less than 175, hind foot not less 
than 30 mm.) :— 
. Tail slightly more than half as long as head) 
and body; ear 16 to 18 mm. ; ale ARVICOLA. 
(A) Upper side brownish. - . A. amphibius amphibius. 
(B) Upper side blackish ‘ : { A. amphibius reta (Scot- 
* and, chiefly Highlands). 
2. Tail about as long as, not longer than, head’ 
and body ; ear 19 to 21 mm. : ; J EPIMYS norvegicus. 
3. Tail longer than head and body; ear 24 to 25 mm. :— 
(A) Upper side brownish. - . £. rattus alexandrinus. 
(B) Upper side blackish. : . £. rattus rattus. 
VOL. II. 2B 
