EPIMYS RATTUS Liinutnis. 



(Synonymy under subspecies.) 



Geoyraphical distrihntlon. — Originally confined to the north 

 temperate portions of the Old World ; now essentially cosmo- 

 politan through artificial dispersal. 



Didgnosis. — Skull with brain-case broad, its greatest breadth 

 across lateral ridges decidedly more than length of parietal 

 measured along ridge ; anterior upper molar without trace of 

 cingulum at anterior border of crown ; first lamina of m^ with 

 distinct outer tubercle usually almost as large as inner tubercle ; 

 terminal heel of m'^ with evident though incompletely separated 

 outer tubercle ; first and second lower molars usually with 

 evident small supplemental tubercles at outer extremity of 

 furrows ; form slender ; tail about as long as head and body 

 (usually somewhat longer) ; ear when laid forward extending 

 about to middle of eye ; hind foot of adults usually under 

 10 mm. in length ; condylobasal length of adult skulls usually 

 08 to 43 mm. 



External cluiradcra. — General form rather slender, iJio tail 

 usually longer than head and body and never, unless injured, 

 noticeably shorter. Head slender, tapering anteriorly, the ear 

 rather large, extending about to middle of eye wlien laid 

 forward, its substance thin and somewhat translucent, its 

 general outline broadl}^ oval, the basal portion of anterior border 

 folded backward (inward) ; posterior border of meatus witli 

 barely indicated ridge ; surface of ear finely papillose and very 

 inconspicuously pubescent. Muzzle pad small but well defined, 

 with deep median groove continuous with cleft in upper lii? ; 

 nostril crescentic, its inner and lower margins swollen, forming- 

 an ill-defined, wart-like excrescence below. Feet moderately 

 large, with no special pecidiarities of form. Front foot with 

 inner digit reduced to a mere tubercle with rudimentary nail not 

 extending to its edge ; outer digit slightly shorter than second, 

 the third and fourth sub-equal, slightly longer than second ; pads 

 five, large, distinct, that at base of outer toe with slightly 

 developed supplemental tubercle at outer base. Hind foot with 

 inner digit extending to middle of first phalanx of second di"it, 

 outer digit somewhat longer, the second, third and fourth 

 sub-equal and longest ; pads six, the postero-internal more than 

 twice as long as broad, widest in front, narrowing posteriorly, 

 the posteroexternal well developed, fully one-third as large as 

 that at base of outer toe ; pads at bases of inner and outer toes 

 with rudimentary supplemental outer tubercles ; surface of sole 

 naked, smooth except between pads, where it is noticeably 

 wrinkled. Claws simple, curved, those on hind fec;t largest. 

 Tail slightly four-sided, uniformly and very thinly haired 

 throughout, the tip with no distinct pencil ; annulations well 



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