150 Cincinnati Society of Natural History. 
across the posterior articulating surfaces, which are decidedly con- 
cave, vertically, and look far more directly backward and less 
downward than in Castor. The arterial foramina pass through the 
double tranverse processes and form a notch in the lower posterior 
margin of the anterior articulating surfaces. The remaining four 
cervical vertebrze are missing. 
The length and general bulk of the spinal column, from the 
sacrum to the atlas, does not differ much from that of an adult 
man, being about twenty-one inches in length. It is difficult to 
determine the exact length, as some pieces are missing and the 
epiphyses are nearly all absent. ‘There were fourteen thoracic ver- 
tebre, nine of which had transverse processes. This is evident 
from the fact that there are nine ribs on one side having tubercles. 

Fria. 10.--One-third natural size.. Two dorsal vertebree near the lumbar region: a, 
anterior and upper view. Note the pits in base of neural arch; b, posterior, under 
View. 
The lumbar vertebre are five in number, and the sacral four— 
these divisions corresponding to Castor. ‘The centra are porous 
and spongy to a degree not often met with. At the base of each 
neural arch (upper side of centrum) is a pair of pits, or foramina, 
which appear to open into the more spongy interior. These are 
easily seen in Castor, Arctomys, Fiber, and probably many other 
genera, but here they are conspicuous to a marked degree. In the 
cervical region they are comparatively small and remote, on oppo- 
site sides of the median line. ‘They are larger and nearer together 
in the middle dorsal region, while in the lumbar region thev 
occupy the whole floor of the arch, separated only by a thin blade, 
and are large enough, each, to hold a fair-sized bean. Split a 
black walnut, remove the kernel from the divisions of one of the 
halves, and we have similar-looking cavities. The posterior tho- 
racic, and the lumbar vertebrz, are coarsely punctured on the 
under side — one or two of the lumbar to such an extent and so 
irregularly as to give them a worm-eaten appearance —some of 
the foramina having the diameter of a small goose quill. 

