Character of the Order--A well-defined Group--Teeth Evidence--Kinds and Number of Teeth--The Incisors: their Growth, Renewal, and Composition--The Molars--The Gnawing Process--Skeleton--Brain--Senses--Body--Insectivora and Rodentia--Food of Rodents--Classification--THE SIMPLE-TOOTHED RODENTS--Characteristics--THE SQUIRREL-LIKE RODENTS--SCIURIDÆ--Distinctive Features--THE COMMON SQUIRREL--Form--Distribution--Food--Bad Qualities--Habits--THE GREY SQUIRREL--THE FOX SQUIRREL--Flying Squirrels--Their Parachute Membrane--THE TAGUAN--Appearance--Habits--Other Species--THE POLATOUCHE--THE ASSAPAN--The Genus _Xerus_--THE GROUND SQUIRRELS--THE COMMON CHIPMUNK--THE MARMOTS--Distinguishing Features--THE SPERMOPHILES--THE GOPHER--THE SISEL, OR SUSLIK--THE BARKING SQUIRRELS--THE PRAIRIE DOG--Description--Species--Habits--Burrows--Fellow-inmates in their “Villages”--THE TRUE MARMOTS--THE BOBAC--THE ALPINE MARMOT--THE WOODCHUCK--THE HOARY MARMOT, OR WHISTLER--ANOMALURIDÆ--Tail Peculiarity--Distinctive Features--HAPLODONTIDÆ--Description--THE SEWELLEL--CASTORIDÆ--THE BEAVER--Skeletal Peculiarities--General Form--Appearance--Distribution--The Beavers of the Old and New World--Habits--Wonderful Sagacity--The Building Instinct--Their Method of Working--The various Stages--Their Lodges--Their Dams--Activity by Night--Flesh--Hunted--The _Castoreum_ 81 CHAPTER II. THE DORMOUSE, LOPHIOMYS, RAT, AND MOUSE FAMILIES.