449 MONOGRAPHS OF NORTH AMERICAN RODENTIA. 
pean skulls. Dr. Ely states that, in six American skulls, the average length 
is 5.39, and the average length of the nasals 1.81, or nearly 0.34 of the length. 
In three others, with an average length of 4.42, the nasals average 1.59 or 
0.36 of the length. In seven others, he finds, however, the relative length 
of the nasals still greater. 
(5) The frontal portion of the lachrymal bone in the American Beaver,” 
Brandt finds, ‘‘is more triangular,—posteriorly twice as broad as anteriorly,— 
and smaller than in the European; it is also nearly limited to the space 
between the malar and frontal bones; since it impinges only with its anterior 
border-like narrow end upon a small process of the upper jaw, or even only 
approaches it.. In the Beavers of the Old World, however, the larger, more 
quadrangular, anteriorly and posteriorly equally broad frontal portion of the 
lachrymal bone lies not only between the malar and frontal bones, but is 
united in similar extent equilaterally with the superior maxillary.” 
In the majority of instances, Dr. Ely finds the differences here men- 
tioned by Brandt, but states that in some of his skulls the lachrymal has the 
quadrangular form, being as broad anteriorly as posteriorly, and my own series 
affords additional exceptions, the individual variation in the form of this bone ~ 
being very great in the American skulls. 
In respect to the anterior aspect of the skull, Dr. Brandt found the 
nasal opening triangular in the European,—narrower inferiorly, and hence 
more or less pointed,—but quadrangular in the American, being but little 
narrower below than above. Dr. Ely notes the greater tendency to the 
quadrangular form in the American, but cites examples where the opening 
is nearly if not quite as triangular as in the European, and I find several 
American skulls in my series that fully bear out the statement. The form of 
the nasal opening, however, is very variable; in very few is it distinctly quad- 
rangular, being generally considerably narrowed and rounded, or more or less 
angular, below. Dr. Brandt also finds the inter- and inferior maxillaries 
broader in the European skulls than in the American, and the incisors also 
correspgndingly broader. As shown by Dr. Ely, however, the difference is 
evidently somewhat less than the amount claimed by Dr. Brandt. 
In respect to the lateral aspect of the skull, Dr. Brandt finds no differ- 
ence in the dorsal outline in the two forms, but points out a number of alleged 
differences in other features. The zygomatic process of the maxillary he 
claims is relatively narrower, as compared with the malar bone, in the 
