380' PALEONTOLOGY 



(miocene) tertiary period have yielded evidences of not 

 fewer than eleven genera of Eodentia distinct from any now 

 known to exist. The deposits at Eppelsheim, near Darm- 

 stadt, of the same miocene age, have given evidence of 

 Eodents akin to the marmot and the beaver. 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, belonging to the 

 genus Lagomys, now confined as an existing species to Asia ; 

 and of a very large Eodent, akin to the beaver, called Trogon- 

 therium. Similar fossil remains have been abundantly found in 

 the pliocene and pleistocene formations of continental Europe, 

 including representatives of the genus Hystrix, or fossil 

 porcupines (H. refossa, Ger.), from the pliocene of Issoire 

 (fig. 133). The coeval deposits of America have yielded fossil 

 remains of extinct species belonging to genera — e. g., Lago- 

 stomus, Echimys, Ctenomys, Ccdogmys, and other Cavies — 

 now restricted to South America. In North America, fossil 

 remains of a Rodent of comparatively gigantic size have 

 recently been discovered. Some parts of the skeleton, and 

 more especially the dentition of the rodent order, are higldy 

 characteristic — the form of the articular surface for the lower 

 jaw, which is a longitudinal groove, the molars, especially of 

 the phytiphagous kinds, crossed by enamel plates more or 

 less transverse — these, with the long, curved, chisel-shaped 

 incisors, two in each jaw, suffice to determine the ordinal 

 relations of the fossil. The incisors alone would not be always 

 so safe a guide, for the rodent modification of these teeth is 

 repeated in the marsupial wombat and the lemurine aye-aye. 

 Willi regard to the Eodentia, the great beaver {Trogon- 

 thcrium) seems to have become extinct in England and the 

 Europaso-Asiatic continent before the historical period ; whilst 

 i lie smaller pliocene beaver continued to exist with us, like 



