The geographical distribution of animals, with a study of the relations ...

———140 DISTRIBUTION OF EXTINCT ANIMALS. [part ii.seven species allied to Tillotherium and Anchippodus, and havingalso relations, as Professor Cope believes, with the South AmericanToxodontidse.Rodentia.—This order is represented in the Pliocene by abeaver, a porcupine, and an American mouse (Hespervmys), allextinct species of living genera, the Hystrix being an Old Worldtype ; and Professor Cope has recently described Panolax, anew genus of hares from the Pliocene of New Mexico. TheMiocene deposits have furnished an extinct genus allied to theharesPalccolagus ; one of the squirrel familya small extinct form of beavermouseIschyromys ;Palceocastor ; and an extinctEumys. The Eocene strata of Wyoming have latelyfurnished two extinct forms of squirrel, Paramys and Sciuravus ;and another of the Muridse (or mouse family), Mysops.Cetacea.—Numerous remains of dolphins and whales, belongingto no less than twelve genera, mostly extinct, have beenfound in the Miocene deposits of the Atlantic and Gulf States,from New Jersey to South Carolina and Louisiana ;while sevengenera of the extinct family, Zeuglodontidse, have been found inMiocene and Eocene beds of the same districts. Some remainsassociated with these are doubtfully referred to the Seal family(Phocidae) among the Carnivora.Edentata.—Tillquite recently no remains of this order haveoccurred in any North American deposits below the Post- Pliocene;but in 1874 Prof. Marsh described some remains allied toMegalonyx and Mylodon, from the Pliocene beds of Californiaand Idaho, and forming a new genus, Morotherinm. As theseremains have only occurred to the west of the Eocky Mountains,and in Pliocene deposits whose exact age is not ascertained, theyhardly affect the remarkable absence of this group from thewhole of the exceedingly rich Tertiary deposits in all other partsof North America.General Relations of the extinct Tertiary Mammalia of NorthAmerica and Europe.—Having now given a sketch of the extinctMammalia which inhabited Europe and North Americaduring the Tertiary period, we are enabled by comparing them,