292 APPENDICES. 



bones of the European beaver is not so strongly curved as in the 

 American. Two of the European skulls, however, approach 

 quite to the American in this respect. The superior surface oi 

 the anterior half of the nasal bones is in six of the European 

 skulls pretty plane ; in two of the others, on the contrary (Nos. 51 

 and 1955 of the Kiew Col.), as in all the five American, it is 

 strongly convex. In regard to the character (or relation) of the 

 nasal bones, there remains, therefore, in consequence of the pre- 

 ceding remarks, only their more considerable length in compari- 

 son with the skull as a mark of the European beaver; since the 

 greater lengthening posteriorly of the nasal bones cannot be so 

 rigorously proven in all European beavers, especially not in our 

 Lapland specimens. It is possible, however, that the nasal bones 

 are less prolonged posteriorly in younger animals than in full- 

 grown, so that in this way the full-grown European might be 

 recognized by its posteriorly prolonged nasal bones. Confirm- 

 atory of this view are the following facts : 1. That in all of the six 

 old skulls lying before me of European beavers, the posterior ex- 

 trem.ities of the nasal bones reach more or less far posteriorly, 

 and that this happens in a young skull of the Kiew Collection 

 (No. 57), the length of which is four lines greater than that of 

 the one from Lapland ; and 2, that in one very young American 

 skull, the nasal bones extend backward somewhat less relatively 

 than in the full grown." 



It is in respect to the nasal bones that the greatest difference 

 has been observed between the European and the American 

 beavers. The most striking obvious difference being the back- 

 ward extension of the nasals in the European variety. In ex- 

 treme cases, their posterior margins are found behind the middle 

 of the margin of the orbital ring: and over the anterior margin 

 of the upper molars — a point probably never reached by the 

 nasals in the American skull ; but this feature of the European 

 skull is not constant. Brandt has not found it in the Polish and 

 the Lapland beaver, and he expressly yields the point as to its 

 being a characteristic mark of the European variety ; it cannot, 

 he says, "be rigorously proven in all European skulls." In the 

 New York skull the nasals are elongated as represented in the 

 Polish skull. It does not appear that the lengthening of the 

 nasals in the American skull is invariably due to age — since 

 their proportional length, in some young skulls, perhaps equals 



