1010.] The Rodent ia. 323 



CHAPTER VIII. GENETIC RELATIONS OF THE RODENTS 



AND EDENTATES. 



Analysis. 



Page 



I. The Rodentia 323 



Outline history of tlie ordinal classification 323 



Naturalness of the order 325 



Origin of the Rodentia 326 



TT The Edentate or Paratherian Orders 332 



Outline history of the ordinal classification 332 



The Tubulidentata 334 



The Pholidota 337 



The Xenarthra 339 



I. The Rodentia. 



Outline History of the Ordinal Classification. 



The characters of the dentition of the group are so striking and the 

 representatives of the order form so many passages from one type to another 

 that the modern conception of the group was reached much more rapidly 

 than was the case in other orders. 



1693. Ray describes under the "Quadrupeda vivipara pede multifido 

 herbivora binis pr?elongis dentibus anterioribus in utraque maxilla, sen 

 Leporinum Genus" the following animals (/. c, p. 204): 



"Lepus, Aayws . . . . The Hare"; "Cuniculus, Aaavirvs, A Rabbit or 

 Cony"; "Cuniculus Brasiliensis Tapeti dictus" [= Lepus brasiliensis]; 

 "Cuniculus Brasiliensis Aperea dictus" [= Cavia apcreq]; "Hystrix, the 

 Porcupine"; " Cuanda Brasiliensibus Marcgr Tlaquatzin spinosum Her- 

 nand." ['! Cocndou (= Synetheres) prehensilis]; "Castor sive Fiber, The 

 Beaver"; " Sciurus vulgaris," " Sciurus virginianus cinereus major, the great 

 grey Virginia Squirrel"; "Sciurus Zeylanicus pilis in dorso nigricantibus 

 Rukkaia dictus" [Sciurus macrourus]\ "Sciurus Americanus volans, the fly- 

 ing squirrel" [Sciuropterus volucella]; "Sciurus Getulus Caii apud Gesnerum 

 The Barbary Squirrel" [Xerus getulus]; then follows some fifteen species 

 under the term "Mus," including, beside the true rats and mice, the "mus 

 aquaticus sive Rattus aquaticus" [Fiber zibethicus], "Mus aquaticus exo- 

 ticus. The Muscovy or Musk Rat," [ ? Crocidura myosura] ; " Mus Avellan- 



