36 ZOOLOGY. 



is clearly seen when the usual wearing down does 

 not take place, as, e.g., when the lower jaw is placed 

 obliquely under the upper jaw, or when a tooth is 

 absent in one jaw, under which circumstances the 

 corresponding incisor in the other jaw is not worn 

 down. In such a case the incisors continue to grow, 

 ultimately curving upwards or downwards, and be- 

 coming tusk-like structures (Fig. 20). The Rodents 

 have no canines. In those Rodents which feed both 

 on animal and vegetable food (the " Omnivora," e.g. 

 squirrel, common mouse, brown rat, etc.), the crowns 

 of the back teeth are completely covered with enamel ; 

 in the purely vegetable feeders (" Herbivora," e.g. 

 hare, rabbit), they are compound teeth (p. 22). In 

 most Rodents the hind feet are longer than the fore, 

 giving a springing gait. Eyes large. Many forms 

 have " cheek-pouches," in which the food they obtain 

 can be stored up for some time. When the pouches 

 are full, a muscle contracts by which their ends are 

 drawn backwards; they are emptied by the animal 

 pressing them with its fore feet. The majority of 

 Rodents are small, they are at most of medium size 

 (hare). The majority of the species have great powers 

 of reproduction, by which the injurious kinds are 

 sometimes rendered a very great pest. The British 

 forms injurious to agriculture principally belong to 

 the families of hares, mice, and voles. The squirrel 

 (Sciurus vulgaris), and the dormice (especially 

 Myoxus avellanarms) are solely of importance in 

 forestry. 



Family : LeporidsB {Hares and Rabbits). 



Skull somewhat long. Two small incisors behind 

 the two large upper ones. Ears long and spoon- 

 shaped. Upper lip cleft. Back teeth with enamel 

 folds. Here belong the hare (Lepus tvniidus) and 

 rabbit (Lepus cuniculus). 



