RODENTIA-CASTORINAE-CASTOR CANADENSIS. 
859 
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. 
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....... 
Liropean. 
American 
0.146 
0.130 
0.142 
0.129 
0.102 
' 0.094j 
0.025 
0.023 
0.046 
0.047 
0.028 
0.029 
0.072 
0.075 
0.050 
0.047 
0.035 
0.035 
0.018 
0.016| 
0.017 
0.018| 
0.041 
' 0.039 
0.048 
0.045' 
0.025 
0.027 
0.030 
0.029 
0.038 
0. 035| 
0.025 
0.028 
0.109 
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 Busslands, (St. Petersburg, 1855, 4to.)—the author devotes many pages to the 
