422 PALEONTOLOGY. 



The more recent tertiary formations and the bone-caves in 

 England have furnished fossil remains not distinguishable 

 from the existing beaver, hare, and rabbit, water-vole and 

 field-vole, as well as remains of a Pica, or tailless hare, belong- 

 ing to the genus Lagomys, and of a very large Kodent, akin 

 to the beaver, called Trogontherium. Similar fossil remains 

 have been abundantly found in the pliocene and later forma- 

 tions of continental Europe, including representatives of the 

 genus Hystrix, or fossil porcupines (H. refossa, Ger.), from the 

 pliocene of Issoire. The coeval deposits of America have 

 yielded fossil remains of extinct species belonging to genera 

 — e. g., Lagostomus, Echimys, Ctenomys, Ccelogenys, and other 

 Cavies — now restricted to South America. In North America, 

 fossil remains of a Eoclent (C aster o'ides) of comparatively 

 gigantic size have recently been discovered. 



The great beaver (Trogontherium) seems to have become 

 extinct in England and the Europseo- Asiatic continent before 

 the historical period ; whilst the smaller pliocene beaver con- 

 tinued to exist with us, like the wolf, until hunted down by 

 man. It still survives in a few of the great continental rivers. 

 Of the little Lagomys of our ossiferous caves no living 

 example remains in either England or Europe. The species, 

 indeed, may be extinct : its genus is now limited to Central 

 and Southern Asia. 



GEOGRAPHICAL DISTRIBUTION OF PLEISTOCENE MAMMALS. 



A most interesting generalization has been educed from 

 the mass of facts relating to the fossil Mammals of the later 

 tertiaries — viz., the close correspondence between the fauna of 

 those and of the present periods in the Europaao- Asiatic ex- 

 panse of dry land. In this expanse species continue to exist of 

 nearly all those genera which are represented by pliocene and 

 post-pliocene mammalian fossils of the same natural continent, 

 and of the immediately adjacent island of Great Britain. 



