MARTIN: A COMPARISON OF THREE SKULLS. 395 
In Castoroides kansensis. 
The basie occipital shows no sutural contact with the basic 
sphenoid, but is firmly codssified with that element, and while 
the conical projections mentioned by Wyman exist, they are 
situated more caudally and closer to the occipital condyle than 
in either the Lenawee specimen or that described by Wyman 
from Clyde. 
The pterygoid, or wall between the internal pterygoid fossa 
and the inferior entrance to the posterior nares, rises imme- 
diately from the projection mentioned by Wyman, but at a 
point much farther back than in his specimen or that from 
Lenawee; consequently the pterygoids would be proportionally 
much longer transversely, while just behind and above the 
foramen rotundum two eavities, one above the other, occur, 
extending forward and upward, with the evidences of having 
a thin septum between the outer and inner walls of the inter- 
nal pterygoid fossa. 
Probably one of the most striking features of Castoroides 
is its enormous incisor teeth, which appear much out of pro- 
portion to the size of the molar teeth and skull. 
The principal differences observed between the Lenawee 
and the Boicourt skulls, then, are: The proportionally larger 
incisors, with narrower grooves and greater number; the rela- 
tively longer diastema between the incisors and molars; the 
difference in the pattern of the folds in the last molar, and its 
comparative smallness; the difference in frontonasal region; 
comparatively longer nasals; and deep, rough pittings of the 
parietals. 
BIBLIOGRAPHY. 
HALL AND WYMAN. The Geological Position of Castoroides ohioensis. 
Boston Journal of Science. 
ALLEN AND CouES. Monograph of the Rodents of North America. U. S. 
G. Survey Report, vol. XI, 1877. 
JOSEPH Moore. Concerning.a Skeleton of the Great Fossil Beaver, Cas- 
toroides ohioensis. Journal of Cincinnati Society of Natural His- 
tory, Nov. 1, 1890. 
JOSEPH Moore. The Recently Found Castoroides in Randolph County, 
Indiana. The American Geologist, vol. XII, Aug. 1893. 
JOSEPH Moore. A Cranium of Castoroides Found at Greenfield, Indiana. 
Proceedings of the Indiana Academy of Science, 1899. 
2—Univ. Sci. Bull, Vol. VI, No. 6. 
