146 Cincinnati Society of Natural History. 
width or distance apart. One edge of a cement plate may be several 
times thicker than the other, and in more than one case, as at x, 
fig. 5, the flattened enamel rings in the crowns, unless carefully 
examined, appear to be confluent. 
The lower series, on either side, is slightly concave antero-pos- 
teriorly, corresponding to an equal convexity in the upper. The 
upper grinders slant and curve outward and backward; the lower 
slant inward and forward, though the first, toward the crown, bends. 
slightly backward. | 
The upper projects about equally from the alveolus all along. 
Below, the fourth is barely above the alveolus rim, but they rise 
gradually forward, till the front border of the first stands out more 
than a half inch. 
The distance from the inner curve of the upper incisors to the 
crown of an anterior molar is 4.12 inches, which is .25 of an inch 
greater than in the Clyde skull. 

Fig. 7.—One-third natural size. Lower jaw, exterior view: a, angle bent down- 
ward and inward: c, coronoid process; d, condyle, bent inward ; f, fossa for attach- 
ment of muscles. Straws show foramina. B, Outline of lower jaw of Castor, same 
scale. 
The massive look of the lower jaw, with its many prominent 
features, arrests the attention of the most indifferent observer. Its 
weight, after lying in a dry room for five months, is one pound and 
twelve ounces avoirdupois. 
It can hardly be needful to describe in full detail what specialists 
have heretofore had in hand. Some account may, however, be of 


