2 ARKIV FÖR ZOOLOGI. BAND 5. N:0 6. 



These figures are, however, not so good, nor so repre- 

 sentative as they ought to be, and in consequence of this 

 the diagnose of the Swedish Beaver as proposed by Matschie 

 in the words quoted above does not hold good as will be 

 proved in the following. The first men tion ed charaoteristic, 

 viz. the alleged absence^ of the inner enamel fold of the Jäst 

 upper molar is quite erroneous because the molar figured by 

 Meves (1. c.) is anomalous. The specimen used for this 

 drawing is kept in the R. Natural History Museum in Stock- 

 holm, and the present writer has thus had the opportunity 

 of ascertaining that this anomaly is only to be found on the 

 last upper molar of the right side, not even on the left side 

 of the same specimen nor on any other molar of either side 

 of any other Beaver skull among 5 more adult Swedish spe- 

 cimen in the same collection. The same anomaly is, however, 

 present on one side of the youngest of four Norwegian Bea- 

 ver skulls which Prof. Collett kindly has lent me for com- 

 parison, and which all agree with Swedish specimens of the 

 same size and age. The said anomaly is thus present on one 

 side in either of two skulls out of 10 adult or semiadult from 

 Scandinavia and it only proves the variability in this respect, 

 nothing more. ^ 



The second characteristic is to be found in the Swedish 

 and Norwegian material which I have had at my disposition. 

 So far it evidently holds good but the question is, if the 

 Scandinavian Beavers always or as a rule have such an 

 arrangement of the enamel folds that on the worn surface of 

 the upper molars the inner fold passes the end of the ante- 

 rior fold of the outer side and ends free between the anterior 

 and middle enamel folds of the outer side, and if, on the 

 other hand, in the Elbe Beaver the inner enamel fold always 

 or as a rule is opposite to the anterior fold of the outer side 

 and presses itself against the same, for only in such a case 

 the from Matschie quoted characteristic can be regarded as 

 being of specific value. These conditions deserve accordingly 

 to be examined on a greater material before any decisive 

 conclusions may be drawn and for that purpose the following 



' It. is evident tliat tlie inner fold is not absent, but has become 

 fused with the anterior outer fold. 



^ Since this paper was written Dr. Forsyth Major has published a 

 paper »on species of Gastor fossil and recent» (Proc. Zool. Soc. 1908 Pt. Ill, 

 p. 630) to which may be referred. The author quoted figures there tn^ of 

 a Rhone Beaver with a similar enamel pattern. 



