112 RODENTIA order vi 



Arvicola Lac^pede {Hypudaeus Illiger) (Fig. 141 A). Posterior extremity 

 of the incisor extending behind the last M. Many Recent forms found also 

 in the Pleistocene of Europe. 



Cuniculus Wagner (Banded lemming) (Figs. 141 B, 142). Posterior 

 extremity of the incisor terminating below the last M. 

 ^f^/^tM^^ Recent in northern Europe. Fossil in the Pleistocene. 



^~'^^^^^^J Myodes Pallas {Lemimis Linck). Same locality and 



Fig. 142. horizon as the preceding. 



sp^tiMZ'^oTvltburi. Microtus Schrank. Fiber Cuvier. Recent and in the 



Lower P. 3/i. Pleistoccne of North America. Anaptogonia, Sycium Cope. 



Pleistocene of North America. Mimomys F. Major. Teeth 

 with roots, rather high. Pliocene of Norwich. Ruscinomys Deperet. Pliocene 

 of Roussillon. LopMomys Dep6ret from the same locality. Systematic 

 position doubtful. 



Subfamily 6. S pal agin ae. 



Skull and dental formula similar to that of the Dipodinae. 



Siphneus Brants. Recent and fossil in northern Asia. Rhizomys Gray. 

 Recent in Asia, fossil in the Pliocene of Siwalik. 



Prospalax Kormos. Fossil in the Pliocene and Pleistocene of Hungary. 



Family 9. Hystricoidea (Hystricomorpha). 



Angle of the mandible arising from the lateral surface of the incisor alveolus. 

 Coronoid process low, jaws movable only in an antero-posterior direction. Skull flat, 



without postorbital process and with very wide infraorbital canal. ' ' ' ' • Cheek 



teeth with enamel folds, usually prismatic-hypsodont, seldom brachyodont. Fibula 

 free. 



The Hystricoidea appear first as Hystricinae, Theridomyinae and Issiodoro- 

 myinae in Europe. The Hystricinae spread later over the entire surface of 

 the eastern hemisphere ; the two remaining subfamilies wander to South 

 America, and develop in that region as Erethizontinae, Capromyinae, Chinchillinae, 

 Octodontinae and Cariinae. The Ctenodactylinae and Bathyerginae are restricted 

 to Africa, and are not yet known to exist as fossils. 



Subfamily 1. Hystricinae. Old World Porcupines. 



Cheek teeth with roots, moderately hypsodont. Crowns with enamel folds and 

 fossettes. 



Hystrix Linn. Fossil in Europe from the Oligocene through the Pleisto- 

 cene. In the Pliocene and Pleistocene also in India. A large well-known 

 form from the Eocene of Quercy is "Hystrix" lamandini Filhol. 



Subfamily 2. Erethizontinae. New World Porcupines. 



Cheek teeth brachyodont. Descendants of Trechojnys 1 



Eosteiromys Amegh. Colpodon strata of Patagonia. Steiromys Ameghino 

 in the Miocene of Santa Cruz. 



