ZAPODIDE—ZAPUS—SYNONYMY AND CHARACTERS. 465 
Trunk enlarged posteriorly, in correlation with the shortness of the fore limbs 
and great elongation of the hind ones, especially of the pes (ef. Aluride 
except Gerbilling) ; nevertheless, the pes with five perfect and-separate meta- 
tarsals, and five functionally developed digits (cf. Dipodida, Pedetide). Claws 
not peculiar (cf. Pedetide). Tail greatly exceeding the trunk in length (ef. 
most Muride), very slender, scant-haired (cf. Dipodide, Pedetide). Pro- 
gression saltatorial. 
Other characters of less value are adduced as generic under the head 
of Zapus. 
GENUS ZAPUS, Coues. 
< Dipus, sp., ZIMMERMANN, Geogr. Gesch. ii, 1780, 358.—Daviegs, Trans. Linn. Soe. iv, 1798, 155.—Barron, 
Trans. Amer. Philos. Soc. iv, 1799, 114. 
< Mus, sp., ZIMMERMANN, Penn. Arkt. Zool. i, 1787, 131 (Mus longipes, Zimm., nee auct.). 
< Gerbillus, sp., DESMAREST, Mamm. ii, 1822, 331 (not type). 
= Meériones, PR. Cuvier, Dents des Mamm. 1825, 187 (type. But not Meriones of Mliger, Prod. 1811, 82, 
which is based on Dipus tamaricinus and D. meridianus). 
< Meriones, AUDUBON & BacHMAN, Quad. N. Am. ii, 1851, 251 (used in an extended sense, to include 
Old World species of Dipodida). 
= Jaculus, WAGLER, Natiirl. Syst. Amphib. 1830, 23 (type. But not of Jarocki, 1821, nor of early authors).— 
Waener, Arch. fiir Naturg. 1841, Bd. i, 119.—Barrp, Mamm. N. Am. 1857, 429.—AQrsToNn, 
Proce. Zodl. Soc. Lona. 1876, 89. 
= Zapus, Cours, Bull. U. 8. Geol. Surv. Terr. 2d ser. No. 5, 1875, 253 (type). 
Cuars.—With well-developed internal cheek-pouches. Digits of the 
hand five, the first of which is rudimentary, with a flat, blunt nail; palms 
naked, granular, and tuberculate. Digits of the foot five, all functional, and 
with perfect claws and basal webs; sole naked throughout, the heel smooth, 
the rest granular and tuberculate. Meatus of the ear capacious, closed with 
large antitragal and tragal flaps. Pelage coarse and hispid. Size small; 
configuration modified from an ordinary Murine shape; physiognomy peculiar. 
Other characters are fully detailed in the description of the species 
beyond. Here I may refer again, more in detail, to the grounds (briefly set 
forth when I proposed the name Zapus) upon which a new designation was 
given to the well-known genus; for.I insist that a new name was required. 
The generic type in question has been successively called Dipus, Mus, 
Gerbillus, Mériones or Meriones, Jaculus, and Zapus. Which of these names 
is tenable ? 
The first three—Dipus, Alus, and Gerbillus—are too obviously inappli- 
cable to be brought into the question at all. Their unavailability in this con- 
* 
nection is now conceded by all. 
1. Jaculus, or, in its older forms, Jaculus and Jaevlvs, was the specific 
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