xxv] 



RODENTIA 



701 



SCIURIDAE; the Voles, Rats and Mice, MURIDAE; and the Dormouse, 

 the sole British representative of the family MYOXIDAE. In North 

 America there are allied species, and in addition the Ground- 

 squirrels, or Chipmunks, Tamias, and three species of Woodchuck 

 or Marmot, Arctomys; also Porcupines, represented by the common 

 Canadian Porcupine, Erethizon dorsatus, the Beaver, Castor cana- 

 densis, and many others. Hystrix cristata is the Porcupine of 

 Southern Europe and Northern Africa. The Guinea-pig is probably 

 a domesticated variety of the South American species Cavia cutleri. 



19 



20 



14 



FIG. 352. Side view of the skull of the Eabbit, Lepus cuniculus. 



1. Nasal bone. 2. Lachrymal bone. 3. Orbitosphenoid. 4. Frontal. 

 5. Optic foramen. 6. Orbital groove for ophthalmic division of trigeminal 

 nerve. 7. Zygomatic process of squamosal. 8. Parietal. 9. Squamosal. 

 10. Supra-occipital. 11. Tympanic bone. 12. External auditory 

 meatus. 14. Lower incisor. 15. Anterior premolar tooth. 16. Anterior 

 upper incisor. 17. Mandible. 18. Maxilla. 19. Premaxilla. 



20. Occipital condyle. 



These various species are very like each other in their general 

 anatomy, but differing in the character of their molars, in their 

 fur and in their tails. 



Hares and Rabbits constitute the DUPLICIDENTATA, one of 

 the two sub-orders into which the order is divided. The name 

 is derived from the possession of an extra pair of upper incisors, 

 which however are so small as to be useless. The tail is short 

 and the cusps of the premolar and molar are joined so as to form 

 ridges or folds running across the tooth. The Common Hare, 



