MESODONTA. 
141 
Transverse proximal diameter of the cuboid.. .. 0. 012 
Transverse distal diameter of the cuboid. 0. 008 
Antero posterior distal diameter of the cuboid... 0. 009 
Length of the navicular anteriorly .. 0, 0055 
Transverse diameter of the navicular. 0, 0110 
Antero-posterior diameter of the same.,. 0. 009 
Length of the ectocuneiform.... 0. 0075 
Transverse diameter of the same... 0. 005 
Antero posterior diameter of the same... . . 0. 009 
Length of the entocuneiform... 0. 0125 
Transverse distal diameter of the same. 0.004 
Antero-posterior distal diameter of the same.. 0. 008 
This species was about the size of the Raccoon, and its jaws indicate 
a greater degree of robustness. It is dedicated to my friend Henry C. 
Yarrow, M. D., to whom was committed the charge of that party of the 
Survey to which I was attached, and to whose zeal in the cause of the natural 
sciences the success of the special expedition is. largely due. 
Tomitherium tutum, Cope. 
Plate xxxix, fig. 19; Plate xl, figs. 16-25. 
Represented by a fragmentary ramus of the mandible, which supports 
the last two premolars and the first true molar, with the alveoli of the canine, 
and first and second preniolars. Accompan 5 ^ing it is a number of skeletal 
fragments entirely appropriate in size to this jaw. All were found with the 
pieces belonging to the T. jarrovii. 1 originally referred all the teeth to a 
single individual, as they belong to the right side, and nearly resemble 
each other. Having the last molar of P. jarrovii in the ramus of another 
individual, I was compelled, in order to accommodate the molars in one 
jaw, to regard the teeth now described as canine and first premolar as 
incisor and canine. This determination I now regard as impossible, since 
the positions of those teeth in relation to the symphysis require them to be 
identified as canine and first premolar. Their relative sizes accord with this 
arrangement, and the first premolar retains its normal one-rooted character. 
As a consequence of this determination, the last tooth in the ramus becomes 
the first true molar, and, as such, presents such a different form and size 
from the corresponding tooth of the other specimen, as to require that I 
should regard it as a distinct species. This appropriately corresponds with 
the bones which accompany the teeth, since they also belong to two 
individuals, a larger and a smaller. The smaller is certainly precisely 
