Family ZAPODIDiE. 



< Subfamily Dipodinw, BaIRD, Mamm. N. Amor. 1857, 428 (Muridce). 



= Group Jaciilina, OaruS, Haudb. Zool. i, 1868, 101. 



= Family Jaculidce, Gill, Arraug. Kara. Mamm. 1872, 20. 



= Family Zap >didw, Coues, Bnl). U. S. Geol. and Gcogr. Snrv. Terr. 1875, 2d ser. No. 5, 253. 



= Subfamily Jaculinas, Alston, Proc. Zool. Soc. Lond. 1870, 89 (Dipodida:). 



The single known species which represents this family has been variously 

 classified by different authors. Since the period when it was commonly 

 assigned to the genus Mus of the older writers, it has usually, under various 

 generic designations, been considered to be allied to the Jerboas (Dipus), 

 doubtless on account of a superficial resemblance it bears to those animals. 

 It has frequently been referred to the genus Dipus itself; while, even among 

 the modern authors who have appreciated a generic distinction between Dipus 

 proper and Zapus, there have been those who regard these two genera as 

 components of one subfamily, Dipodince, of the family Murida But the two 

 genera have little in common aside from the ordinal characters they share 

 with other Rodents — little of consequence in common beyond the features by 

 which they are both to be recognized as members of the Murine series* of 

 Rodents ; for it seems that, whatever may be the value of the characters by 

 which the species of Zapus may be differentiated from typical Murines, — 

 even from Mus itself, — equally strong at least, if not stronger, points of differ- 

 ence from Dipus or Pcdetes may be found. I should judge that a classifica- 

 tion which distinguishes a family Dipodidce from Murid^e should, in apprecia- 

 tion of taxonomic equivalency, eliminate Zapus as the type of a separate 

 family, — one which, as I still contend, is scarcely more closely related to the 

 groups which Pedetes and Dipus respectively typify than it is to the Murida 

 proper. I find it quite as easy to draw the line between Zapus and either 

 Dipus or Pedetes as it is to separate the same form from Mus proper ; and 

 accordingly, in indorsing a classification which admits numerous families of 

 the Murine series, I recognize in the type of Zapus a group of full family 



* ilgomoipha, Alstou, 1870 — approximately eijuivaleut to the Myoidca of Gill, 1872. 



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