268 THE ZOOLOGIST. 
Beaver (‘Historia Animalium,’ lib. 8, cap. 47), says “the tail 
is like that of a fish; in the other parts of the body they 
resemble the Otter; they are both of them aquatic animals, and 
both have hair softer than down.” 
Quoting this passage, Franzius says:—‘‘ Nam teste etiam 
Plinio fiber est lutra cui accessit cauda piscts, sed lutra est fiber sine 
cauda”’ [ piscis, understood]. But his translator, improving upon 
this (p. 223), puts it thus :—‘‘ Pliny saith that the Otter and 
Beaver are both the same, but in this they differ; the Beaver 
hath a tail, but the Otter hath no tail at all”! It need scarcely 
be said that this is altogether a libel on the Otter, which (as we 
all know) has a very fine tail, long, thick, and tapering. 
What, then, is the zoological position and what the relation- 
ships of the amphibious Beaver, about which such marvellous 
stories have been told ? 
The form of the skull and the character of the teeth (two 
large incisors in each jaw separated by a wide interval from the 
molars, and no canines) show that it belongs to the order 
Rodentia, or gnawing animals, which feed entirely on vegetable 
substances. Although aquatic in its habits, it has nothing to 
do (as the ancients supposed) with the fish-eating Otter, which 
has a very different dentition, and belongs to the order Carnivora, 
or flesh-eating mammals. 
The order Rodentia forms one of the most clearly defined 
eroups of the Mammalia; a group which has representatives in 
all parts of the world, and the species of which are very 
numerous, especially in America, including, amongst others, 
such familiar animals as Hares and Rabbits, Squirrels, Rats, 
and Mice. 
The most striking characters of the Rodents are those 
furnished by the teeth, so admirably adapted for their mode of 
life, and it will be observed, on examining the skull of a Beaver, 
that the incisor teeth have enamel only in front; so that, their 
posterior surfaces wearing away faster than the anterior, they are 
always naturally sloped or chisel-shaped. Their prismatic form 
causes them to grow from the root as fast as they wear away 
from the tip (their formative pulp being persistent), and this 
tendency to increase in length is so powerful that, if either of 
them be lost or broken, the corresponding tooth in the other jaw, 
having nothing to oppose or impede it, becomes developed to a 
