4 ARKIV FÖR ZOOLOGI. BAND 5. N:0 6. 



such a suggestion the attention may be turned to an exami- 

 nation of the skulls and molars of the Beavers from the Elbe 

 killed in a recent time. The first skull of a Beaver with 

 undoubted origin from the Elbe examined by me was that 

 of a young specimen which had once belonged to the col- 

 lections of Hensel.^ An examination of this specimen proved 

 that on every molar the inner enamelfold shoots past the 

 end of the anterior fold of the outer side just as in Swedish 

 and Norwegian specimens and there is on the whole no con- 

 spicuous difference between this skull and Swedish Beaver 

 skulls of corresponding age. The skull of a young Beaver 

 from »Elbe bei Glinde, Kreis Calbe» ^ has not the inner 

 enamelfold exactly opposite the anterior fold of the outer 

 side on any of the molars, they might at most be termed 

 obliquely opposite in some molars and in all of them the end 

 of the inner fold shoots more or less past that of the anterior 

 outer fold and touches it at the inner side. In the lower 

 molars the outer fold shoots deeply in to the interspace 

 between the posterior and middle inner folds. The nasals 

 and other cranial bones have the same appearance as the 

 corresponding ones of Swedish Beavers of the same age. 

 These two skulls were, however, as has been mentioned, 

 rather young and the condition of the molars and the mutual 

 relation of the enamel folds might change as well as other 

 characteristics with increasing age and growth. To make sure 

 about this T procured two large skulls of fullgrown Elbe 

 Beavers, both obtained near Wittenberg, Dessan. 



The first of these shows the following condition s, left 

 side: 2>* = enamel folds almost opposite (alleged »Elbe type») 

 but the end of the inner fold pressed in between the anterior 

 and middle outer fold; 7n^ = inner enamel fold and anterior 

 enamel fold from the outer side meet somewhat more obli- 

 quely than in p^ and the former shoots past the latter; m- 

 and m^ have the inner fold shooting completely past the end 

 of the anterior outer fold (alleged »Swedish type»); right 

 side of the same skull (Fig. 1): p^, m-, and m^, inner fold 

 shoots past the anterior outer fold (»Swedish type»); m^ the 

 folds meet obliquely, but the inner shoots past the anterior 



^ This skull has kindly been placed at my disposition by Professor 

 Dr. W. Leche. 



' This skull has been kindly placed at my disposition by Professor 

 Dr. Kurt Lampert, Stuttgart. 



