LÖNNBERG, STUDY OF THE VARIATION OF EUROPÉ AN BEAVERS. 1 1 



of the molar. In tvvo adult Elbe Beavers I have measured 

 the palatal width between the first molars to be about 10 mm. 

 while the breadth of the molar is about 9 mm. In the Mol- 

 davia Beaver the palatal width at the place quoted is about 

 13 mm. and in the old Danube Beaver the same measurement 

 is 15 mm. while the molar measures resp. 8,5 and 9 mm. In 

 the younger Danube Beaver the palatal width is only 10, f) mm. 

 and that of the molar 8, .5 mm. These dimensions are thus 

 variable. 



The lengtli of the molar series is shorter in the Moldavia- 

 Danube Beavers than in the Elbe Beavers as can be seen 

 from the table of measurements, but it is, of course, uncertain 

 whether this is constant. 



The structure of the molars of the Moldavia-Danube 

 Beavers is very variable and it is therefore best to describe 

 the arrangement of the enamelfolds of each tooth separately. 

 In the specimen from Wittingau on the left side: m^ the tvvo 

 posterior outer enamelfolds have joined in such a way that 

 an oval complete ring is enclosed within the branches of a 

 broad fold from the outer side. The inner fold extends with 

 its tip between this large fold and the anterior outer fold 

 which is normal, m^ and m^ are normal and their inner fold 

 ends in the interspace between the middle and anterior 

 outer fold. In jj^ the inner fold has become fused with the 

 anterior outer fold so that a continuous transverse fold is 

 formed in front, and the posterior portion shows the two 

 posterior outer enamelfolds forming a separate portion of 

 the tooth in exactly the same manner as Matschie be- 

 lieved to be characteristic for the hindmost molar of the 

 Swedish Beaver. The condition of the right side is also very 

 interesting. In m^ the tips of the posterior and middle ex- 

 teriör enamel folds have become fused which results in for- 

 ming, as just has been described from the opposite side, a 

 separate central column, on the worn surface appearing as 

 an oval ring, surrounded by a broad fold. In addition to 

 this the inner fold is fused with the antero-external fold so 

 as to form a separate transverse fold as has been described 

 from the premolar of the left side. m^ m^ and p-^ have the 

 normal arrangement of the folds with the tip of the inner 

 fold extending between the middle and anterior outer folds. 

 The Beaver from Danube at Regensburg has normal teeth and 



