634 DR. FORSYTH MAJOR ON FOREST-BED MAMMALS. [Junel6, 



which obtains not unfrequently in younger stages of Beavers' 

 molars (especially in p^ and m^) and sometimes persists in the 

 adult. Text-fig. 136 B shows the upper molars of a young adult 

 of the Ehone Beaver, where m^ exhibits the pattern of Meves's 

 figure. A second, rather old specimen of the Rhone Beaver in 

 the British Museum (!N"o. 5.3.9.1) shows likewise on both sides 

 the same conformation of the m^ as in the younger specimen. 

 Text-fig. 135 B, on the other hand, exhibits the upper molar series 

 of a rather old Swedish Beaver in the Museum of the Royal 

 College of Surgeons*, kindly placed at my disposal by Prof. Keith. 

 Here m^ presents the normal condition ; and together with the 

 other cheek-teeth, when compared with Meves's figure, illustrates 

 the well-known fact of the considerable individual variation in the 

 pattern of the enamel, chiefly due to different stages of wear. 



Text-fig. 137. 



Castor fiber L. Lapland. Side view of anterior portion of skull. 

 R. Coll. of Surgeons Museum. 



The text-figure 137 exhibits the side view of the anterior 

 portion of the skull in the Royal College of Surgeons, which does 

 not depart from the noi-mal condition in the European Beaver. 

 The figure in Meves's Atlas to which Matschie alludes is appa- 

 rently taken from the skull of a youngish specimen, and, besides, 

 may not be quite correct. 



As to the characters assigned to Matschie's new species, G. hal- 

 ticus,^ notably the greater elongation of the sagittal crista, they 

 are simply those of old age. 



* No. 3102, " from an animal taken in Lapland about the year 1830." 



