_Suborder_ CONDYLARTHRA 438 _Suborder_ TOXODONTIA 439 _Nesodon_, 439; _Toxodon_, 439; _Typotherium_, 440. _Group_ TILLODONTIA 441 Bibliography of Ungulates 442 CHAPTER X THE ORDER RODENTIA 443 _Suborder_ SIMPLICIDENTATA 448 _Section_ SCIUROMORPHA, 448. _Family_ ANOMALURIDÆ, 449; _Anomalurus_, 449. _Family_ SCIURIDÆ, 450; _Sciurus_, 450; _Rhithrosciurus_, 452; _Xerus_, 452; _Tamias_, 452; _Pteromys_ and _Sciuropterus_, 453; _Eupetaurus_, 454; Extinct genera, 454; _Arctomys_, 454; _Cynomys_, 455; _Spermophilus_, 456; Extinct genera, 457. _Family_ HAPLODONTIDÆ, 457; _Haplodon_, 457. _Family_ CASTORIDÆ, 457; _Castor_, 457. _Section_ MYOMORPHA, 459. _Family_ MYOXIDÆ, 459; _Myoxus_, 459; _Eliomys_, 459; _Graphiurus_, 459; _Claviglis_, 460; _Muscardinus_, 460. _Family_ LOPHIOMYIDÆ, 460; _Lophiomys_, 460. _Family_ MURIDÆ, 461; _Hydromys_, 461; _Xeromys_, 461; _Platacanthomys_, 462; _Gerbillus_, 462; _Pachyuromys_, 462; _Mystromys_, 462; _Otomys_ and _Dasymys_, 462; _Malacomys_, 462; _Phlœomys_, 462; _Dendromys_, 463; _Cricetus_, 463; _Holochilus_, 464; _Sigmodon_, 464; _Rhithrodon_ and _Ochetodon_, 464; _Neotoma_, 464; _Hypogeomys_, 465; _Nesomys_, 465; _Brachytarsomys_, 465; _Hallomys_, 465; _Eliurus_, 465; _Phenacomys_, 466; _Arvicola_, 466; _Synaptomys_, 467; _Myodes_, 467; _Cuniculus_, 470; _Fiber_, 470; _Neofiber_, 472; _Ellobius_, 472; _Siphneus_, 472; _Deomys_, 473; _Mus_, 473; _Nesocia_, 475; _Golunda_, 476; _Uromys_, 476; _Chiruromys_, 476; _Hapalotis_, 476; _Mastacomys_, 476; _Acanthomys_, 476; _Echinothrix_, 477; _Typhlomys_, 477; _Cricetomys_ and _Saccostomus_, 477; _Pithechirus_, 477. _Family_ SPALACIDÆ, 477; _Spalax_, 477; _Rhizomys_, 477; _Bathyergus_, 478; _Georychus_ and _Myoscalops_, 478; _Heterocephalus_, 478. _Family_ GEOMYIDÆ, 478; _Geomys_, 478; _Thomomys_, 478; _Dipodomys_, 479; _Perognathus_ and _Heteromys_, 479. _Family_ DIPODIDÆ, 479; _Sminthus_, 479; _Zapus_, 480; _Dipus_, 480; _Alactaga_, 480; _Platycercomys_, 480; _Pedetes_, 480. _Section_ HYSTRICOMORPHA, 480. _Family_ OCTODONTIDÆ, 480. _Ctenodactylus_, 481; _Pectinator_, 481; _Octodon_, 481; _Habrocoma_, 482; _Schizodon_, 482; _Ctenomys_, 482; _Spalacopus_, 482; _Petromys_, 482; _Myopotamus_, 482; _Capromys_, 482; _Aulacodus_, 483; _Plagiodon_, 483; _Loncheres_ and _Echinomys_, 483; _Mesomys_, 483;