Famiry ZAPODID AE. 
< Subfamily Dipodinw, Barrp, Mamm. N. Amer. 1857, 428 (Murida@). 
= Group Jaculina, Carus, Handb. Zool. i, 1868, 101. 
= Family Jaculidw, GiLi, Arrang. Fam. Mamm. 1872, 20. 
=TV amily Zapodida, Cours, Bull. U. 8. Geol. and Geogr. Surv. Terr. 1875, 2d ser. No. 5, 253. 
= Subfamily Jaculinw, ALSTON, Proc. Zodl. Soe. Lond. 1876, &9 ( 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 haye been those who regard these two genera as 
components of one subfamily, Dipodina, of the family Muride But the two 
genera have litfle 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 Pedetes may be found. I should judge that a classifica- 
tion which distinguishes a family Dipodide from Muride should, in apprecia- 
tion of taxonomic equivalency, eliminate Zapus as the type of a separate 
one which, as I still contend, is scarcely more closely related to the 
family, 
groups which Pede/es and Dipus respectively typify than it is to the Muride 
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 
* Myomorpha, Alston, 1876—approximately equivalent to the Myoidea of Gill, 1572. 
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