UZ 
NOTES ON GZOMYVS BURSARIUS, THE 
Y POCKET-GOPHER. 
BY HENRY LESLIE OSBORN, PH.D., ST. PAUL, MINNESOTA. 
PENDING the publication of a fuller account of this in- 
teresting creature, it seems to be worth while to call the 
attention of students of the subject to some of the more 
interesting points already determined. The animal is well 
known in the northwestern United States, where in some 
regions, its habits protecting it from capture, it becomes 
avery great pest. In the vicinity of St. Paul, Minn., its 
traces are to be seen in open fields, where it can be re- 
cognized by the mounds of finely grained dirt that mark 
its excavating operations. It is very shy and largely 
nocturnal, but in more sparsely settled places it is seen in 
the day-time. I havenever seen it in the fields that are 
near my home, but its mounds are common about here 
everywhere. The fossorial habit is thus less positive and 
exclusive than in the mole and in the mole-rat of Europe. 
Yet this animal is truly subterranean, and its structure in 
many interesting ways isa departure from that of ordinary 
rodents. In its work of digging it goes into its burrow 
head foremost, using the head and fore limbs nearly equally. 
The dirt as it is loosened is first kicked under the animal 
till it is collected in a mass, when the creature turns about 
and with the fore limbs pushes it up out of the way. The 
animal is thus an important agent in this vicinity in that 
work of the circulation of the ingredients of the soil that 
Darwin showed us is one of the important parts played by 
earth-worms in the world economy. 
Tue Pockets.—The anterior part of the head of the 
pocket gopher is unusually elongate for a myomorph, so 
that the incisors are pushed out a long way in front of the 
molar region. Thisanterior region is, by reason of the 
great compression of the palatal region and the consequent 
narrowing of the roof of the mouth, well adapted for the 
ingrowth of the hairy portion of the upper lip, sothat the 
latter surrounds the upper incisors, reducing the palatal 
area to a very narrow groove in the centre of the roof of 
this part of the mouth chamber. The entire roof of the 
mouth is covered with hair and is closed behind at the 
level of the molar teeth by a constriction that leaves only 
a circular opening at the rear closed by the short tongue. 
This anterior portion of the mouth may be called the 
vestibule, as it leads also to the pockets. It is really 
more external than internal, and this character is of im- 
portance in the use of the mouth as an organ of excavation. 
The pockets are apparently the homologue of the cheeks. 
They are bounded by a fold of skin on the outer side which 
arises from the maxillary region of the face and runs 
downward to the lower jaw some distance behind the bases 
of the lower incisor teeth.’ Inside this fold of skin the 
pockets run backward to the level of the hinder border 
of the scapula. The pockets thus situated are lined in- 
ternally with the softest hair and like the vestibule already 
noted are really external cavities and not a part of the 
mouth. The indications from a study of the pockets 
in other rodents, as well as from the anatomy of Geomys, 
are that the pockets, though thus external, are the homo- 
logues of the cheek cavities and that the clothing of hair 
is a secondary character. 
The muscular structure of the pockets is interesting. 
The muscles are presumably part of the paniculus carnosus, 
though they are directly attached to the bony skeleton 
specialized for their peculiar functions. There are three 
distinct sets of muscles present; these are, first, a circular 
muscle that runs around the margin of the pocket in its 
outer bounding fold. ‘This by its contraction would seem 
to purse the opening of the pocket. The second set. of 
1See Baird, U.S.P.R.R., vol. viii., pl. <xi. 
SCHEIN Cle, : 
Vol. XXIII. No. 577 
muscles are those that I will call the protractors of the 
pockets. These are two in number on each side. They 
are spread out in the skin of both the inner and outer 
posterior portions of the pockets, and their fibres converge 
forward to finally form somewhat definite bands. The 
outer of these is attached in the skin at the origin of the 
fold on the upper jaw. The. other is attached to the 
lower attachment of the fold at the lower jaw. These two 
muscles thus surround the pocket, and their contraction 
pulls its recess forward to the opening of the vestibule. 
The third set of muscles are the retractors of the pocket. 
These arise funnel-wise from surface of the pocket both 
on its inner and outer aspects, and they run backward and 
dorsally parallel to the fibres of the latissimus dorsi and 
totally free from the skin. They forma band three or 
four incheslong and nearly an inch wide and are finally 
inserted in the tendinous aponeurosis that covers the in- 
ZZza 
or 
= Retract 
a Sew’ 
Protractor : 
Circe Muscle. 
Geomys, Muscles of the poeket. 
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sertion of the latissimus dorsi and is attached to the 
neural spines of the anterior lumbar vertebre. These by 
their action retract the pockets. As to the use of the 
pockets, it has been erroneously thought in general among 
the people where the gopher is common that its pockets 
are used in the removal of dirt. . Not a single well ascer- 
tained fact can be cited in proof of this notion, and it has 
lsocn certainly ascertained that the pockets are used for the 
reception of the harder portions of the food which are re- 
moved in them to be stored away for winter use. The 
softer parts of the food are eaten and digested at the time. 
Tue VERTEBRAL CoLtuMN.—The cervical vertebre, seven 
in number, are rather small, and in this way it results that 
