BHL10EUS. 
the second, the shortest of the latter two, and the inner, or 
first finger, very short. The dental formula is, incisors, 
6 . 1—1 . 3-3 . 4—1 
— ; canines, — ; premolars, —; true molars, — *>. 
There are three well determined species in this section, the 
P. australis , P. sciureas, and P. breviceps , to which Mr. 
Gould has added a fourth species, P. a riel. They have the 
anterior incisor teeth of the upper jaw large, somewhat sud¬ 
denly dilated immediately below the fang, and assuming a 
triangular form. In P . australis they are broader than in 
either the P. sciureus or P. breviceps. The next incisor, on 
either side, is smaller than the posterior one, narrow at the 
base, and broad at the apex. The third incisor is broad, 
and has a sharp incurved cutting edge. The canine is tolera¬ 
bly large, separated by a narrow space on either side, from 
the false molars, or incisors; compressed and pointed, and its 
anterior and posterior edges are sharp: the exposed part of this 
tooth is more elongated than that of either of the molars. The 
first premolar on either side is large, broad, compressed, and 
pointed, has a slight indication of an anterior and posterior lobe, 
and two distinct fangs. The second premolar is small, short, 
and compressed, and has a minute anterior lobe: this tooth is 
separated by a considerable space from the first premolar, and by 
a narrow space from the third ; the latter touches the first truo 
molar, is narrow in front, and presents one triangular, and 
pointed cusp. The first true molar is considerably larger 
than the following molars, each of which is smaller than the 
preceding, so that the last is not equal in bulk to one-half of 
the first. With the exception of the Inst, all the true molars 
present four somewhat blunt and rounded tubercles, and in 
general appearance very much resemble the corresponding 
teeth in the squirrel. The last molar has but three tubercles 
—two in front, and one behind. The incisors of the lower 
jaw are long, compressed, and pointed, and have the upper 
