852 RODENTIA 



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

 to it in position, both small tubercles -well detiued from t2, the 

 re-entrant angles deep and without supplemental folds ; second 

 lamina essentially like first, not connected with it by longitudinal 

 ridges, /6 entire ; third lamina completely distinct from second, 

 /9 well developed, about as large as /3, <7 absent. Second upper 

 molar with first lamina represented by large tl ; second and third 

 laminae essentially as in m^, 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 tb, the 

 latter joined by an obsolete tQ to outer 

 extremity of /8, the only remnant of 

 the third lamina ; as the crown wears 

 away the second and third laminae 

 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 



£piinij!i mttus. Cheek-teeth. straight, its anterior border with deep 

 re-entrant angle on outer side of 

 middle ; second and third laminye 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 lamina, 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 laminae. 

 Third lower molar with two lamina?, 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. 



Bemarks. — 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 rattiis 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, Epimi/s rattus alexandrinus, 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. 



