140 DISTRIBUTION OF EXTINCT ANIMALS. [part ii. 



seven species allied to Tillotherium and Anchippodus, and having 

 also relations, as Professor Cope believes, with the South American 

 Toxodontidse. 



Rodentia. — This order is represented in the Pliocene by a 

 beaver, a porcupine, and an American mouse (Hespervmys), all 

 extinct species of living genera, the Hystrix being an Old World 

 type ; and Professor Cope has recently described Panolax, a 

 new genus of hares from the Pliocene of New Mexico. The 

 Miocene deposits have furnished an extinct genus allied to the 

 hares — Palccolagus ; one of the squirrel family — Ischyromys ; 

 a small extinct form of beaver — Palceocastor ; and an extinct 

 mouse — Eumys. The Eocene strata of Wyoming have lately 

 furnished two extinct forms of squirrel, Paramys and Sciuravus ; 

 and another of the Muridse (or mouse family), Mysops. 



Cetacea. — Numerous remains of dolphins and whales, be- 

 longing to no less than twelve genera, mostly extinct, have been 

 found in the Miocene deposits of the Atlantic and Gulf States, 

 from New Jersey to South Carolina and Louisiana ; while seven 

 genera of the extinct family, Zeuglodontidse, have been found in 

 Miocene and Eocene beds of the same districts. Some remains 

 associated with these are doubtfully referred to the Seal family 

 (Phocidae) among the Carnivora. 



Edentata.— Till quite recently no remains of this order have 

 occurred in any North American deposits below the Post- Plio- 

 cene; but in 1874 Prof. Marsh described some remains allied to 

 Megalonyx and Mylodon, from the Pliocene beds of California 

 and Idaho, and forming a new genus, Morotherinm. As these 

 remains have only occurred to the west of the Eocky Mountains, 

 and in Pliocene deposits whose exact age is not ascertained, they 

 hardly affect the remarkable absence of this group from the 

 whole of the exceedingly rich Tertiary deposits in all other parts 

 of North America. 



General Relations of the extinct Tertiary Mammalia of North 

 America and Europe. — Having now given a sketch of the ex- 

 tinct Mammalia which inhabited Europe and North America 

 during the Tertiary period, we are enabled by comparing them, 



