U. S. P. R. R. EXP. AND SURVEYS ZOOLOGY GENERAL REPORT 



This genus is distinguished from Dipus, among other characters, by having five toes on the 

 hind feet, (each with separate metatarsus?) instead of hut three articulated to a single 

 consolidated metatarsal bone. The tail in Dipus is densely hairy. The upper molars of Dipus 

 are three instead of four. In Scirtetes the upper incisors are not grooved, and there are two 

 or three metatarsal bones instead of five. 



JACULUS HUDSONIUS. 



Jumping Mouse. 



Dipus hudsonius, ZIMMERMANN, Geographische Geschichte, II, 1780, 358, (based on Pennant's long-legged mouse 



of Hudson's Bay.) 



BODDAERT, Elenchus Animalium, T, 1784, 115, (from Zimm.) 

 FISCHER, Synopsis, 1829, 340. 



Meriones hudsonius, AUD. & BACH. N. Ani. Quad. II, 1851, 251 ; pi. Ixxxv. 

 Mas longipes, ("PALL.") ZIMMERMAXN, Pennant's Arktische Zoologic, I, 1787, 131. 

 Dipus canadmsis, DAVIES, Linn. Trans. IV, 1798, 155. 



SHAW, Gen. Zool. Mamm. II, 1801, 192 ; pi. clxL 

 GerbUlus canadensis, DKSM. Mamm. II, 1822, 321. 



HARLAN, F. Amer. 1825, 155. 



GRIFFITH, Cuv. V, 1827, 240. 



GODMAN, Am. N. H. II, 94. 



Dipus americanus, BARTON, Am. Phil. Trans. IV, 1799, 115; plate. IB. VI, 1809, 143. 

 Jaculus americanus, WAGLER, Syst. der Amphibien, 1830, 23. 

 Meriones americanus, DEKAY, N. Y. Zool. 1, 1842, 70 ; plate xxiv, fig. 2. 

 Muslabradorius, Jos. SABINE, Zool. App. to Franklin's Narrative, 1823, 661. 

 Gerbittus labradorius, HARLAN, F. Am. 1825, 157. 

 GODMAN, Am. N. H. II, 97. 

 Merianes labradorius, RICHARDSON, F. B. Am. I, 1829, 144 ; pi. vii. 



WAGNER, in Scbreb. Saug. IV ; pi. ccxxvi, B, (from Rich.) 



DAWSON, Ed. New Phil. Jour. N. S. Ill, 1856, 2. 

 Jaculus labradorius, WAGNER, Suppl. Scbreb. Ill, 1843, 294. 



KENNICOTT, Mammals Illinois, Pat. Office Rep. Agricultural, for 1856, (1857), 95 ; pi. xi. 

 Meriones microcephalus, HARLAN, Pr. Zool. Soc. London, VII, 1839, 1, (Philadelphia.) 

 Meriones acadicus, DAWSON, Ed. New Phil. Jour. N. S. Ill, 1856, 2 ; plate i 

 Labrador rat, PENNANT, Hist. Quad. 1781, No. 295. IB. Arctic Zoology, I, 1782, 132. 



SP. CH. Above, light yellowish brown ; lined finely with black ; entire sides yellowish rusty, sharply defined against 

 the colors of the back and belly. Beneath, pure white ; feet and undo- surface of tail, whitish. Body measuring 2. 75 to 

 3. 50 inches ; tail, 4. 50 to 6. 00 inches ; hind feet, 1. 10 to 1. 30 inches. 



The head of this species is quite small in proportion to the body, which is thickest behind, in 

 correspondence with the great development of the muscles of the hind legs. There is a very 

 appreciable diminution in size from the rump to the head, without any constriction at the neck. 

 The fur is coarse and stiff, owing to the development of bristly hairs among the softer fur ; it 

 is rather long and pressed flat to the body. The naked muffle is entirely on the under surface 

 of the snout, the hairs extending around the very tip of the nose to the anterior surface, 

 where it is separated sharply from the naked portion by a furrow. It appears as if the hairy 

 skin could be drawn downwards so as completely to cover the nostrils. The nostrils are lateral, 

 and separated by a very wide septum, indented by two furrows. The upper lip is scarcely cleft 

 as far as the base of the incisors, and the space between the notch and the nose is hairy entirely. 



