CASTORIDA—CASTOR—CASTOR FIBER. 443 
e 
American than in the European; but both Dr. Ely’s series and my own furnish 
many exceptions to this, which seems to be a distinction of little importance. 
The differences referred to by Brandt, in respect to the prominence of 
the nasal process of the intermaxillary, the form of the malar bone, and the 
presence of a ridge below the orbital ring, formed by the junction of the 
parietal and frontal bones, are also inconstant, and of slight or very doubtful 
value as features distinctive of the two forms; and the same may be also 
almost said of the other differences detailed by Brandt as occurring in the 
lateral aspect of the skull (numbered 6, 7, and 8 under § 3 in his memoir) ; 
the parts referred to are so variable in different specimens of the American 
animal. 
In respect to the posterior aspect of the skull, the main difference 
insisted upon by Brandt is in respect to the shape of the occipital foramen. 
Respecting this point, Dr. Ely well observes: “ If we examinea large number 
of skulls of the American Beaver, the great variety of forms presented by the 
occipital foramen appears remarkable. It is sometimes low and broad, again 
a rounded arch, and in other instances shows the high triangular shape peculiar 
to the European variety. This form is found frequently in young, and 
occasionally in old [American] skulls.” 
In respect to the posterior aspect of the skull, Dr.. Brandt notices the 
larger size and greater depth of the basilar cavity in the European, with the 
more rounded margins, and the more anterior position of the auditory bull, 
differences both Dr. Ely’s specimens and my own show to be quite constant. 
In the American skulls, these are quite variable features, so that occasionally 
there is a close approximation to the European form. 
After noticing in detail all of the alleged differences pointed out by Dr. 
Brandt, Dr. Ely concludes his examination in the following words: “I have 
thus endeavored to show, from an examination of a large number of skulls of 
the American Beaver, that a greater tendency to variation in these structures 
exists than was observed by Dr. Brandt, in the smaller number (five American 
and eight European), on which he based his differential characteristics. It 
will be remembered that Brandt does not insist upon the most obvious feature 
which distinguishes the Old World Beaver from that of the New World, viz. 
the greater lengthening posteriorly of the nasal bones, since it ‘cannot be 
rigorously proven in all cases’. Following out, then, the principle which 
guided his researches, many additional exceptional instances have been found 
