852 KODENTIA 



the outer tubercle nearly as large as t\, and only a little anterior 



to it in position, both small tubercles well defined from ti, the 



re-entrant angles deep and without supplemental folds ; second 



lamina essentially like first, not connected with it by longitudinal 



rido-es, t% entire ; third lamina completely distinct from second, 



<9 well developed, about as large as t3, tl absent. Second upper 



molar with first lamina represented by large t\ ; second and third 



laminae essentially as in m 1 , the third with well developed <9 



nearly as large as that of preceding tooth and marked off from 



tS by a distinct re-entrant angle. Third upper molar with large, 



distinct, terete tl, small ti and *5, the 



latter joined by an obsolete t6 to outer 



extremity of tS, the only remnant of 



the third lamina ; as the crown wears 



away the second and third laminse 



assume the form of a narrow loop, the 



two limbs of which are separated by a 



deep re-entrant angle. Anterior lower 



molar with crown scarcely as long as 



those of the two succeeding teeth, its 



area also less ; first lamina narrower 



fig. 173. than second, its posterior border nearly 



Epimys raitus. Cheek-teeth. straight, its anterior border with deep 



re-entrant angle on outer side of 



middle ; second and third laminas essentially alike, more strongly 



curved posteriorly than anteriorly, the division into two tubercles 



ill defined ; terminal heel small, compressed ; a small terete 



tubercle usually present at outer edge of space between second and 



third laminae, and a similar though smaller tubercle occasionally 



present in that between first and second. Second lower molar 



essentially like first without anterior lamina, the outer border with 



small supplemental tubercle at anterior base of first lamina, and 



another usually less well developed in space between laminse. 



Third lower molar with two laminse, the anterior of which shows a 



faint indication of division into two tubercles, the posterior similar 



to the posterior heel of the other teeth but considerably larger. 



Remarks. — Though now so completely intermingled in many 

 localities that exact determination of specimens is often im- 

 possible, there seems no good reason to doubt that two geo- 

 graphical races of Epimys rattus have established themselves in 

 western Europe. True rattus, the blackish, slaty-bellied form, 

 is a northern animal, normally occurring in a climate similar 

 to that of central and northern Europe.' The buff- bellied 

 form, Epimt/8 rattus alexandriniis, is normally more southern in 

 its range, finding its optimum conditions, so far as Europe is 

 concerned, in the Mediterranean region.'"' Individuals of each 



* In the United States it appears never to become naturalized north of 

 the limits of the Lower Austral life zone, while E. rattus is or has been 

 locally common in the Transition and Canadian zones. 



