RODENTIA. 27% 
according to Professor Flower these latter are not found in the 
Rodentia generally. The tail varies greatly, being in some very small 
indeed, whilst in others it exceeds the length of the body; the sternum 
or breast-bone is narrow and long, and collar-bones are to be found in 
most of the genera; the pelvis is long and narrow. In most cases the 
hind limbs are longer and more powerful than the fore-limbs ; in some, 
as in the jerboas (Dipus) and the Cape jumping hare (Pedetes caffer), 
attaining as disproportionate a length as in the kangaroos, their mode of 
progression being the same ; the tibia and fibula are anchylosed ; the fore- 
limbs in the majority of this order are short, and are used as hands in 
holding the food to the mouth, the radius and ulna being distinct, and 
capable of rotatory motion. The feet have usually five toes, but in 
some the hind feet have only four, and even three. In point of 
intelligence, the rodents do not come up to other mammals, being as a 
rule timid and stupid; the brain is small and remarkably free from 
convolution. The cerebellum is distinctly separated from and not 
overlapped by the hemispheres of the cerebrum; the organs of smell, 
sight and hearing are usually well developed ; the stomach is simple or 
in two sacs; the intestinal canal and cecum long. The latter is 
wanting in one family. 
Rodents have been divided in various ways by different authors. 
Jerdon separates his into four groups, viz. “ Scwride, squirrels ; 
Muride, rats; Hystricide, porcupines; and Leporide, hares ; which 
indeed are considered by some to embrace the whole of the order; to 
which has recently been added the Saccomyide, or pouched rats, whilst 
many systematists make separate families of the dormice, A/joxide ; 
jetboas, Dipodide; voles, Arvidolide ; mole-rats, Aspalacide and 
Bathyergide ; all included in the Murip#; and the Caviade, Octo- 
dontide, and Hydrocheride, belonging to the Hystricip&” (‘ Mammals 
of India,’ p. 164). 
However, the system that most commends itself is that of Mr. 
E. R. Alston, proposed in the ‘ Proceedings’ of the Zoological Society, 
and founded on the original scheme of Professor Gervais, by which the 
order is subdivided into two on the character of the incisor teeth. 
Those which have never more than two incisors, coated only in front 
with enamel are termed SimpLicIDENTATA, or Simple-toothed Rodents. 
The other sub-order, the genera of which have rudimentary incisors, as 
in the case of hares, rabbits, &c., and in which the enamel is spread 
more or less over all the surface, is termed DupLicipENTATA or Dowble- 
toothed Rodents, and this is the system I propose to follow. 
