REVISION OF THE JUMPING MICE OF THE GENUS ZAPUS. 19 



10.7; inastoid breadth, 10.2; iuterorbital constriction, 4.2; incisor to 

 ]>ostpalatal notch, 8.5; foramen maguuui to postpalatal notch, 8; 

 fronto-palatal depth at middle of molar series, 6.2. 



General remarks. Zapus h. alascensis is a fairly well-marked subspe- 

 cies based on four specimens collected at Yakutat Bay, Alaska. Four 

 additional specimens in the National Museum from Alaska have been 

 examined, but are in such poor condition as to furnish no additional 

 characters. This form undoubtedly iutergrades with true hudsonius 

 somewhere in northern British America. - 



Specimens examined. Total number, 8, from the following localities: 

 Alaska: Nusliagak, 2; Yakutat Bay, 4; Yukon River, 2. 



ZAPUS HUDSONIUS AMERICANUS (Barton). Carolinian Jumping Mouse. 



Dipus americanus Barton, Trans. Am. Philos. Soc., IV, No. XII, p. 115, 1799. 

 Zapus hudsoiiius americanus Batchelder, Proc. New Eng. Zool. Club, I, p. 6, 1899. 



Type locality. Philadelphia, Pa. 



Geographic distribution. From vicinity of Raleigh, N. C., north 

 through Upper Austral zone along coastal plain to southern Connec- 

 ticut and lower Hudson Valley, intergrading in upper edge of its range 

 with Z. hudsonius. 



General characters. Similar to Zapus Jmdsonius, but smaller; dorsal 

 area less distinct; skull and teeth smaller. 



Color. Description of specimens in summer pelage from Raleigh, 

 2f. C. : Entire upper parts deep dull ochraceous, the dorsal area very 

 indistinct and but slightly mixed with black-tipped hairs; sides of head 

 much lighter than remainder of upper parts; ears very dark, nearly 

 black; under parts whitish, suffused with ochraceous. In the fall the 

 dorsal area is indistinct and very thickly flecked with yellowish-tipped 

 hairs ; sides dull yellowish. 



Cranial characters. Skull considerably smaller than in Z. hudsonius, 

 with zygomata more arched and brain case shorter; incisive foramina 

 shorter and relatively broader; interorbital breadth about the same; 

 rostrum relatively deeper and shorter; molar series shorter. 



Measurements. Average of 7 adults from Raleigh, N. C.: Total 

 length, 191.3; tail vertebra?, 115.4; hind foot, 28.3. 1 Two Trom Wash- 

 ington, D. C., average: Total length, 198.5; tail vertebrae, 117.5; hind 

 foot, 28. Skull: Average of two from Raleigh, N. C.: Basilar length, 

 l^j zygoinatic breadth, 10.3; mastoid breadth, 9.2; iuterorbital con- 

 striction, 3.9; incisor to postpalatal notch, 8.2; foramen magnum to 

 postpalatal notch, 7.5; fronto-palatal depth at middle of molar series, 6. 



General remarks. It is unfortunate that the name americanus must 

 be adopted for this subspecies, since it was based on specimens clearly 

 intermediate between the extremes of this form and true hudsonius. 



1 Fide Batcbekler. 



