RODENTIA CASTOR JNAE CASTOR CANADENSIS. 



359 



the American a similar line only intersects the ante-orbital tubercular process of the frontal, 

 sometimes, indeed, scarcely falling across the orbits at all. In a young "specimen from New 

 York, S. M. 1072, however, this line falls but little anterior to the middle of the orbit ; five adult 

 skulls, nevertheless, agree in the more anterior position of the line. In the absence of a skull 

 of the European beaver, I am unable to verify these characteristics, as indicated by Professor 

 Owen, but they are well shown in his figure, from which, also, it will appear that the distance 

 from the anterior end of the intermaxillary bones to the end of the nasal is the same with that 

 from the same point to the anterior molar, or that the two points are situated the one above the 

 other, while in the American beaver the latter line is considerably the longer. The sides of 

 the nasal bones are much more convex in the American. The cranium of the European species 

 seems also longer and more compressed. The cavity in the under surface of the basilar process 

 of the occipital is much larger and broader than in the American. The palatal foramina appear 

 to be further back in the European beaver, where they reach as far as the middle of the third 

 molar, while in the American they only get as far as the interval between the second and third. 



The following comparative table of measurements of the skulls of the European and 

 American beavers may serve to illustrate more fully the above differences. The first column 

 contains the measurements of a recent beaver from France, as given by Cuvier, (Ossemens 

 Fossiles, VIII, 96 ;) the other, those of skull No. 823, from the upper Missouri. 



The measurements of both are given in millimetres. 



Comparative measurements of skulls of European and American beavers. 



European. 



American, 



From summit of occipital crest to anterior extremity of intermaxillary 



From same point to anterior extremity of nasal 



Greatest width between zygomatic arches 



Most contracted portion of skull between orbits 



Width of cranium between zygomatic processes of temporal and auditive tube 



Width of the nose near its extremity.. 



Distance between external border of the auditive tubes 



Height from alveolar border to the summit of the narrowest part of cranium 



Height from middle part of the incisive foramina to middle portion of the nasal bone 



Height of occipital foramen 



Greatest width of occipital foramen 



Distance from occipital foramen to posterior border of palatine arch, (concave edge) 



Distance from posterior border of palatine arch to incisive foramen 



Distance from anterior extremity of the incisive foramen to the anterior border of alveolus of incisors. 



Lengh of alveolar border of molars 



Distance between external borders of last molars 



Distance between external borders of first molars 



Distance from posterior angle of lower jaw to anterior upper border of the alveoli of incisors 



0.146 

 0.142 

 0.102 

 0.025 

 0.046 

 0.028 

 0.072 

 0.050 

 0.035 

 0.018 

 0.017 

 0.041 

 0.048 

 0.025 

 0.030 

 0.038 

 0.025 

 0.109 



0.130 



0.129 



0.094| 



0.023 



0.047 



0.029 



0.075 



0.047 



0.035 



0.016| 



0.018| 



0.039 



0.045| 



0.027 



0.029 



0.035| 



0.028 



0.105 



In a very elaborate series of papers published recently by Brandt in volume VII of the 

 Memoires Mathematiques, Physiques, et Naturelles of the Academy of Sciences of St. Peters 

 burg, and also issued in a separate work under the title of Beitrage zur nahern Kenntniss 

 der Saugthiere Russlands, (St. Petersburg, 1855, 4to.) the author devotes many pages to the 



