ZAPODID^E— ZAPUS— SYNONYMY AND CHARACTERS. 405 



Trunk enlarged posteriorly, in correlation with the shortness of the fore limbs 

 and great elongation of the hind ones, especially of the pes (cf. Mufida 

 except Gerbillince) ; nevertheless, the pes with five perfect and separate meta- 

 tarsals, and five functionally developed digits (cf. Dipodidce, Pedetidce). Claws 

 not peculiar (cf. Pedetida). Tail greatly exceeding the trunk in length (cf 

 most Muridcs), very slender, scant-haired (cf. Dipod/da, Pedetidce). Pro- 

 gression saltatorial. 



Other characters of less value are adduced as generic under the head 

 of Zapus. 



Genus ZAPUS, Coues. 



< Dipus, sp., Zimmermann, Geogr. Gescb. ii, 1780, 358. — Davies, Trans. Liuu. Soc. iv, 1798, 155. — Barton, 



Trans. Amer. Philos. Soc. iv, 1799, 114. 



< Mus, sp., Zimmermann. Peun. Arkt. Zool. i, 1787, 131 (Mus lotigipes, Ziinm., nee auct.). 



< Gerhillus, sp., Desmaeest, Mannn. ii, 1822, 331 (not type). 



= Mdriones, Fn. Cuvier, Dents des Mamm. 1825, 187 (type. But not Heriones of Illiger, Prod. 1811, 82, 

 which is based on Dipus tamaricinus and D. meridianua). 



< Merioues, Audubon & Bachman, Quad. N. Am. ii, 1851, 251 (used in an extended sense, to include 



Old World species of Dipodidw). 

 •= Jacuhts, Wagler, Natiirl. Syst. Auiphib. 1830, 23 (type. But not of Jarocki, 1821, nor of early authors). — 



Wagner, Arch, fur Naturg. 1841, Bd. i, 119.— Baird, Mamui. N. Am. 1857, 429. — Alston, 



Proc. Zool. Soc. Lond. 1876, 89. 

 = Zapus, Coues, Bull. U. S. Geol. Surv. Terr. 2d ser. No. 5, 1875, 253 (type). 



Chars. — 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, 

 Gerhillus, Mrriones or Meriones, Jnculus, and Zapus. Which of these names 

 is tenable 1 



The first three — Dipus, Mus, 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, Iaculus and Iacvlvs, was the specific 

 30 m 



