510 MURIDA-—APODEMUS 
Arvicola, Apodemus appears to have died out in Britain during the 
middle Pleistocene, no trace of the genus being found in the later 
deposits of the Middle Terrace of the Thames. It then reappeared in 
the late Pleistocene (Ightham stage) by two forms having close 
affinities with the living sy/vaticus and flavicolis respectively. The 
sylvaticus-like form has been discovered in numerous English cave and 
fissure deposits of late Pleistocene age; but the remains, although 
abundant, are not sufficiently perfect to permit of a close comparison 
with any particular one of the living British members of the group. In 
Ireland similar fossils have been obtained from the Ballinamintra Cave, 
Co. Waterford (Adams, 7vans. R. Dublin Soc., S. 2, vol. 1., 195, 1881, 
where they are described as frog bones; see Scharff, 184); the caves of 
Kesh, Co. Sligo, where they were found in all deposits from the super- 
ficial brown layer to the basal clay (Scharff, 197); the Edenvale Caves, 
Co. Clare, where they were fairly abundant in all the caves, both in 
upper and lower strata (Scharff, 35); and the Newhall and Barntick 
Caves, Co. Clare, where they were rare and occurred mainly in the 
upper strata (Scharff, 35). Remains of A. sy/vaticus are also common 
in Holocene alluvial deposits and “submerged forests” in England. 
Description :—In general form the Field Mouse is much like a 
House Mouse, but differs in its much longer hind legs, larger hind feet 
and ears, and in its much larger and far more prominent eyes. 
The ears are of a broad ovate form, and extend, when laid forwards, 
for a short distance beyond the eyes; they are thinly clad with short 
hairs ; the antitragus is represented merely by a feeble ridge. The tail 
is about equal to the head and body in length; it tapers distally, is 
somewhat angular in section, and distinctly annulated, there being 
about 150 rings in all; the tail hairs are short and do not conceal the 
annulations, though they form a short terminal pencil. The snout is 
long and very prominent; the nostrils, separated by an upward 
continuation of the deep median cleft of the lip, open obliquely 
outwards and forwards, and are wider in front than behind; beneath 
them the small naked muzzle-pad is bounded by a transverse furrow. 
In each hand the thumb is a rudimentary tubercle covered by a small 
nail; digits 2,3, and 4 are the longest, 3 is slightly longer, 2 distinctly 
shorter than 4; digit 5 reaches to the base of 4; each finger is armed 
with a small sharp claw and crossed below by deep transverse grooves, 
of which there are five or six on digit 3; the palm is naked and 
provided with five normally placed pads, of which the two hinder are 
the largest ; between the pads the skin is irregularly wrinkled. In each 
foot the hallux extends to the base of digit 2; the three middle toes 
are of nearly equal length, digit 3 being, however, slightly the longest ; 
digit 5 reaches distinctly beyond the base of digit 4; the toes are 
grooved transversely below, there being seven or eight grooves on the 
central digits; their claws are like those of the fingers. The sole is 
