(30 
UPPER MAMMAL GALLERY. 
ill these cases may be mentioned tlie gigantic Tree-Eats of Luzon 
in the Philippines, Crateromys ( 826 ) and Pldoeomys ( 792 ) ; and 
likewise the orange-bellied Australian Water-Rat, Hydromys 
ehrysogaster ( 791 ), which typifies a separate subfamily. There 
are numerous other genera of the fiimily which must be passed 
over here, but attention may be directed to specimens of the 
interesting Lemmings, Lemmus (877 to 879 ), and iJicrostonyx 
( 880 ) , as well as to the burrowing Mole-Voles, Ellohius ( 876 ), and 
Zokors, Myotalpa ( 881 ), examples of both of which are shown. 
[Casein] 'bhe Bamboo-Rats, Rldzomys ( 767 ), and Mole-Rats, 
( 770 ) and Bathyergus ( 788 ), of Asia and Africa, represent the 
families Spalacidce and Batliyergidcv^ and have short tails, thick 
heavy bodies, and powerful digging claws. Next come the 
North American Pocket-Gophers {Geomyidcr) ^ somewhat similar 
to the last, but provided with pouches in their cheeks, outside 
their mouths, often large enough to hold a walnut. Specimens 
of the typical genus Geomys (777 to 779 ) are exhibited. The 
Kangaroo-Rats and Pocket-Mice {Ileteromyidce)^ which are also 
North American, include the genera Hetevomys ( 782 ) and 
Dipodops ( 784 ). Following these are the Dipodidw (or 
Jaculidce. case 12), comprising the long-legged and long-tailed 
Jerboas of North Africa and Asia, specially modified for leaping 
lightly over a yielding sandy soil, of which there are several 
generic types, such as Bipus or Jacidus ( 761 ), Alactaga ( 758 ), 
and Emdioreutes ( 763 ) of Yarkand. 
The Hystricomorpha, or Porcupine tribe, have almost 
invariably one pair of premolars above and below, a peculiarly 
twisted low^er jaw, variably shaped slits in the palate, generally 
no process behind the socket of the eye, and separate shin-bones. 
The Ro(ients forming this section are very variable both in size 
and the characters of the skeleton. 
[C;i.se 11.1 This section contains the following families : — The Eedetidw, 
represented by the Springhaas, or so-called Jumping Hare, 
Pedetes cajfer ( 910 ), of Africa. The Octodontidce (case 11), with 
17 or 18 genera, nearly all confined to South America, of which 
the best known is the aquatic Coypu, Myocastor coypus ( 913 ), the 
habits of which are similar to those of the Water-Rat, while the 
fur is thick and soft, and of considerable value. The Porcupines, 
