240 



CHAPTER XXXIV. 



RODENTS TOSODON. 



The Rodents should follow the Pachyderms and precede the Marsupials. If I had so arranged them, 

 we should have heen left without a place for the Whales, Bats, and Insectivora ; and I have 

 introduced these orders between the Pachj-derms and Rodents rather as a necessary digression 

 than as a natural connexion. I beg the reader now to revert to the Pachyderms, and suppose 

 that we have onlj^ just finished them off, and that we are now to adjust the Rodents in continuation 

 of them as satisfactorily as we can. 



Mr. Waterhouse has studied the Rodents with much care and success, and his works have greatly 

 lightened the labour and cleared the path for any one who wishes to acquire a knowledge of the 

 order. 



In his first essay* on the subject he divided the order into three great families, — the Mice, the 

 Porcixpines, and the Hares. In his subsequent works on the subject,! he added a family for the 

 Squii-rels, and first proposed a sub-family, or separate group, for the reception of the Rats with 

 external cheek-pouches. That grouj) has been adopted by others, and raised by Baird to the rank of 

 an independent family. It appears to me that "Waterhouse is right throughout ; and Baird and those 

 who adopt his view wrong in this step. I shall explain why I think so when we come to the Pouched 

 Rats. In the same way I think that Brandt and Giebel err in establishing the families Spalacini 

 and DiPODiNi for other sections of Rats. I look upon them merely as subsections of the other Rats 

 and Mice. So far as relates to these members of the Rodent family, therefore, I adopt Mr. Water- 

 house's main arrangement, j)ure and simple, subject to some modifications in the details of the dif- 

 ferent families. But I add to the order two genera, or families, which Mr. Watorhovise excluded, 

 the Hyrax and Toxodon. These have usually been included among the Pachyderms. They seem 

 to me, however, to be too essentially rodent in their characters to be so treated, and their admission 

 here necessitates some modification of Mr. Waterhouse's arrangement, to allow them to fit in 

 properly. The last of the Pachyderms were the aquatic section, Sirenia. I begin the Rodents with 

 the Toxodon, an extinct water Rodent, or gigantic Capybara. Its affinity to the Capybara requires 

 that animal to follow it, and that brings with it the whole of the Hystricid.?;, or Cavies, and 

 Porcupines. Next to them I place the genus Hyrax, which, on the one hgnd, is also connected 

 with the Capybaras, and, on the other, with the Hares and Pikas. I then get back again into Mr. 

 Waterhouse's groove, which I follow without any great deviation, except transposing the Mice and 



* Waterhouse, "On the Arrangement of the Rodcntia," vol. iv. 1858 ; and " Table of Rodents,'' in Keith Johnston's 

 in Charlesworth's Magazine of Nat. Hist., 1839, p. 90. "Physical Atlas." 



t Waterhouse, " Natural History of the Mammalia," 



