270 MamMALIA OF INDIA. 
ting the mouth interferes with the animal’s feeding. A case is recorded 
by Blyth of a rat which had an eye destroyed by a tooth growing into 
it. Here again occurs a similarity to the elephant, whose tusks grow 
in the same maner, and if abnormally deflected will occasion, as in the 
case of one lately described to me, serious hindrance to the movement 
of the trunk. The incisors of rodents are composed of dentine coated 
in front with a layer of hard enamel, the other surfaces being without 
this protection, except in the case of some, amongst which are the 
hares and rabbits, which have a thin coating as well all over. These 
forms are those with rudimentary incisors, and constitute the links con- 
necting the other mammalia with the Gnawers. 
The molars are much alike in structure, and can hardly be divided, as 
they are by some naturalists, into molars and premolars. They take the 
three hindmost as molars, regarding the others as premolars. Some- 
times these grinders have roots, but are more commonly open at the 
end and grow from a permanent pulp. ‘They are composed of tubular 
and convoluted portions of enamel filed up with dentine, and their 
worn surfaces show a variety of patterns, as in the case of the Probos- 
cidea. These enamelled eminences are always transverse, and accord- 
ing to Cuvier those genera in which these eminences are simple lines, 
and the crown is very flat, are more exclusively frugivorous ; others, in 
which the teeth are divided into blunt tubercles, are omnivorous ; whilst 
some few, which have no points, more readily attack other animals, and 
approximate somewhat to the Carnivora. 
The head is small in proportion to the body, the skull being long and 
flat above ; the nasal bones are elongated ; the premaxillaries very large 
on account of the size of the incisor teeth, and the maxillaries are, 
therefore, pushed back ; the zygomatic arch is well developed in most, 
but is in general weak ; the orbit of the eye is never closed behind ; the 
tympanic bulla is very large; the jaw is articulated in a singular 
manner ; instead of the lateral and semi-rotary action of the Herbivora, 
or the vertical cutting one of the flesh-eating mammals, the rodent 
has a longitudinal motion given by the arrangement of the lower jaw, 
the condyle of which is not transverse, but parallel with the median line 
of the skull, and the glenoid fossa, or cavity into which it fits, and 
which is situated on the under side of the posterior root of the zygoma, 
is so open in front as to allow of a backwards and forwards sliding 
action. ‘The vertebral column is remarkable for the great transverse 
processes directed downwards, forwards, and widening at the ends. In 
the hare these processes are largely developed; the metapophyses or 
larger projections on each side of the central spinous process are very 
long, projecting upwards and forwards; the anapophyses or smaller 
projection in rear of the above are small; and the hypapophyses or 
downward processes are remarkably long, single and compressed ; 
