We now come to the Rodentia, a very extensive and difficult order, in which there is still much difference of opinion as to the details of classification, although the main outlines are pretty well settled. The foundations of a true classification of this order were laid by Mr. G. R. Waterhouse more than thirty years ago, and succeeding authors have done little more than follow his arrangement with unimportant modifications. Professor Lilljeborg, of Upsala, has however made a special study of this group of animals, and has given an original and detailed classification of all the genera. (_Systematisk Öfversigt af de Gnagande Däggdjuren, Glires. Upsala, 1866._) I follow this arrangement with a few slight modifications suggested by other naturalists, and which make it better adapted for the purposes of this work. Order--RODENTIA. Fam. { 55. Muridæ Rats. { 56. Spalacidæ Mole-rats. { 57. Dipodidæ Jerboas. { 58. Myoxidæ Dormice. { Murina { 59. Saccomyidæ Pouched Rats. { (Waterhouse) { 60. Castoridæ Beavers. { { 61. Sciuridæ Squirrels. Simplicidentati { { 62. Haploodontidæ Sewellels. { { { 63. Chinchillidæ Chinchillas. { { 64. Octodontidæ Octodons. { Hystricina { 65. Echimyidæ Spiny Rats. (Waterhouse) { 66. Cercolabidæ Tree Porcupines { 67. Hystricidæ Porcupines. { 68. Caviidæ Cavies. Duplicidentati { Leporina { 69. Lagomyidæ Pikas. { (Waterhouse) { 70. Leporidæ Hares. The Edentata have been classified by Mr. Turner, in the _Proceedings of the Zoological Society_ (1851, p. 205), by Dr. Gray in the British Museum Catalogue, and by Professor Carus in his _Handbuch_. The former takes a middle course between {91}the numerous families of Dr. Gray, seven in number, and the two families to which Professor Carus restricts the existing species. I therefore follow Mr. Turner. Order--EDENTATA. Fam. Bradypoda 71. Bradypodidæ Sloths. { 72. Manididæ Scaly Ant-eaters. { 73. Dasypodidæ Armadillos. Entomophaga { 74. Orycteropodidæ Ant-bears. { 75. Myrmecophagidæ Ant-eaters. The Marsupials have been well classified and described by Mr. Waterhouse in the first volume of his _Natural History of Mammalia_, and his arrangement is here followed. The suborders adopted by Professor Carus are also given. Order--MARSUPIALIA.