THE KANSAS UNIVERSITY 
SCIENCE BULLETIN. 
Vou. VI, No. 6] JANUARY, 1912. Wnore SeniEs 
ON A COMPARISON OF THREE SKULLS: CASTOR- 
OIDES OHIOENSIS, CASTOROIDES KANSENSIS, AND 
CASTOR. 
BY H. T. MARTIN. 
(Plates 24-27.) 
(Contribution from the Zodlogical Laboratory, No. 199.) 
INCE the first discovery of Castoroides ohioensis and its 
S description, in 1838, by Foster, there has been approxi- 
mately twenty specimens, mostly fragmentary, reported 
from as many different localities. Out of this number it is 
interesting to note that only one, that from Dallas, Tex., was 
found west of the Mississippi valley. This, coupled with 
the fact that the Boicourt specimen figured in this paper is a 
new addition to the Pleistocene of Kansas, adds much to the 
value of the specimen. 
Through the courtesy of the secretary of the Smithsonian 
Institute, the writer has been allowed the privilege of figuring 
and comparing with our Kansas specimen a nearly complete 
skull of Castoroides ohioensis. So perfect is this specimen that 
only a small portion of both the malar arches is all that is 
missing. The skull is beautifully preserved, with the denti- 
tion absolutely perfect. The double posterior nares, well 
shown, is formed by the pterygoides being laterally compressed 
at about their middle, until they meet, thus forming two ori- 
fices instead of one, as in all other rodents. The superior fossa, 
pyriform in shape, the lower and smaller one triangular. (See 
plate 25, fig. A, at a-a.) 
It is unfortunate that so little is known of the history re- 
lating to the discovery of the beautiful skull which the writer 
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