90 DISTRIBUTION OF ANIMALS. [PART I. 
* 
The two next orders consist of but a single family each, viz. : 
Order Fam. 
PROBOSCIDEA _... 53. Elephantide ... ... Elephants. 
HYRACOIDEA ... 54. Hyracide .» «+ Rock-rabbits. 
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 classifi- 
cation of all the genera. (Systematisk Ofversigt af de Gnagande 
Daggdjuren, 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. Muride cael bere, eediees 
56. Spalacide ... ... Mole-rats. 
57. Dipodide ... ... Jerboas. 
ee 58. Myoxidee éy: jswa,y Domine: 
(Waterhouse) 59. Saccomyidw ... ... Pouched Rats. 
G0. Castoride ... ... Beavers. 
simplicidentati 61. Sciuridze + .-. Squirrels. 
. 62. Haploodontide ... Sewellels. 
63. Chinchillide ... ...Chinchillas. 
64. Octodontide ... ... Octodons. 
Hystricina ) 65. Echimyide ... ... Spiny Rats. 
(Waterhouse) } 66. Cercolabide ...  ... Tree Porcupines. 
67. Hystricide ... ... Porcupines. 
68. Caviidee we ae Cavies, 
a . Leporina 69. Lagomyide- ... ... Pikas. 
Dup licidentati | Waterhouse) | 70. Leporidze doe aes |) ELABR, 
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 
