A Skeleton of Great Fossil Beaver, Castoroides Ohtoensts. 151 
The spinous processes slant backward, as in Caséor, till we reach 
the tenth thoracic, which is vertical. Those back of this slant 
more or less forward. The third and fourth lumbar spines are 
the longest in the series, and slant forward nearly forty degrees, 
which is more than in Castor. There is no marked difference in 
the length of the neural spines from the fourth thoracic back to 
the sacrum. They are relatively short, and in the lumbar and pos- 
terior thoracic they are quite wide antero-posteriorly. In Cas- 
torowdes, Arctomys and Fiber said spines are wider than the intervals 
between, while in Castor the spaces are wider than the spines. The 
intervertebral foramina are relatively small. 
The lateral diameter of the first thoracic vertebra, including 
transverse processes, is fully three inches, and the distance between 
outer edges of anterior zygapophyses of the same is half a line 
less than two inches. ‘These transverse diameters diminish back- 
ward to the fifth. The transverse processes from the fourth to the 
ninth are double— the lower process having a facet to fit the 
tubercle of a rib—the upper process bending upward, slanting 
backward, and the tips of some of them turning inward as in 
Castor, but the upper portion is broader and more wing-lke than 
in said genus. | 
The tenth, eleventh and twelfth have no lateral processes proper, 
except so many barely distinct prominences. It would be difficult 
to conceive a better example of compactness, or a nicer provision 
for firm interlocking, combined with ample bending and twisting, 
than we have in the region from the twelfth to the fourteenth. 
The articulating facets are much curved laterally and fit very 
closely. ‘The anterior zygapophyses are clasped between the poste- 
rior zygapophyses, on the one side, and the strong, styloid, back- 
ward-projecting anapophyses on the other ; somewhat as if pinched 
between a thumb and finger. The anapophyses fade out with the 
second lumbar, as in Castor. 
The flattened, horn-shaped lateral processes of the fifth lumbar 
curve forward about an inch, and a little downward. They meas- 
ure from tip to tip 3.55 inches; lateral diameter of centrum, 1.75 
inches; vertical diameter of centrum, 1.12 inches; length of 
neural spine, 1.25 inches. 
