CHORDATA. 207 



B. DEGIDUATA. Placenta deciduate (except in the Prosimiae). 

 Order 5. Rodentia (Glires). Mammals with (usually) five clawed digits 

 to the maims and pes, chisel-shaped continuously growing incisors, 



and 3-6 back teeth with transverse folds of enamel ; no canines. Pla- 

 centa discoidal. Lepus timidus, hare. L. cuniculus, rabbit. Cavia 

 cobaya, C. aperea, guinea-pig. Hydrochcerus capybara, Hystrix, 

 porcupine. Pedetes caffer, Cape jumping hare. Cricetus frumen- 

 tarius, hamster. Mus rattus, black rat. M. decumanus, brown rat. 

 M. musculus, mouse. Arvicola, vole. Myodes, lemming. Castor 

 fiber, beaver. Myoxus, dormouse. Sciurus vulgaris, squirrel. 



