XV THE RATS AND MICE 471 
glandular swelling at the base of the oesophagus, such as occurs 
in the last genus and in Graphiurus. Of Graphiurus there are 
thirteen species, all African in range. The genus does not differ 
widely from the last. There is, however, a glandular region of 
the oesophagus. Hliomys is the last genus of typical Dormice. 
It is Palaearctic in range. 
Platacanthomys, of a Dormouse-lhke form, has like other 
Dormice a long tail, on which the long coarse hairs are arranged 
in two rows on opposite sides towards the tip; it is represented 
by a single species, P. /asiwrus, from the Malabar coast. It is 
arboreal in habit. The fur is mingled with flattened spines. 
The molars are reduced to three on each side of each jaw. This 
form has been bandied about between the “ Mice” and _ the 
“ Dormice”; but Mr. Thomas’s discovery of the absence of the 
caecum argues strongly in favour of its correct location among 
the Gliridae. TZyphlomys is an allied genus, also from the 
Oriental region. This and the last are placed in a special 
sub-family of the Gliridae, Platacanthomyinae, by Mr. Thomas. 
Fam. 2. Muridae.—This family, that of the Rats and Mice 
in a wide sense, is the most extensive family of Rodents. In it 
Mr. Thomas includes no less than seventy-six genera. The 
molars are generally three. The tail is fairly long, or very long, 
and the soles of the feet are naked. 
Sub-Fam. 1. Murinae.—The true Rats and Mice may be 
considered to form a sub-family, Murinae. The genus Jus, 
including the Rats and Mice in the limited sense of the 
word, contains about 130 species. They are exclusively Old 
World in range, being only absent from the Island of 
Madagascar. In the New World there are no species of 
the restricted genus Mus. The eyes and the ears are large; 
the pollex is rudimentary, and bears a nail instead of a claw. 
The tail is largely scaly. All the members of the genus are 
small animals, some quite minute. In this country there are 
five species’ of the genus, viz. the Harvest Mouse, J/. minutus, 
which has a body only 24 inches long with an equally long tail. 
It is the smallest of British quadrupeds with the exception of 
the Lesser Shrew. The Wood Mouse, JZ. sylvaticus, is about 
twice the size; it differs also from the last species in that it 
1 To which a sixth, the ‘‘ Yellow-necked Mouse,” Mus flavicollis, may perhaps 
be added. 
