[Illustration: FIG. 2. _Sinclairella dakotensis_ Jepsen, UCM no. 21073,
right M2; Orellan, Weld County, Colorado; drawing by Mrs. Judith Hood:
occlusal view, approximately × 9.]
_Material._--UCM no. 20173 (fig. 2), is a right M2.
_Locality and stratigraphy._--The tooth was discovered at
the Mellinger locality, Sec. 17, T 11 N, R 65 W, Weld
County, Colorado. The Mellinger locality is in the Cedar
Creek Member, White River Formation, and its fauna is
considered to be of Orellan age (Patterson and McGrew, 1937,
and Galbreath, 1953).
_Description and comments._--UCM no. 21073, which is more
heavily abraded than KU no. 11210, shows no evidence of a
stylar cusp either anterolabial to the metacone or in the
position of a mesostyle. A small stylar cusp is present
anterolabial to the paracone. A notch that appears to have
been cut through the enamel of the posterolabial corner of
the crown could have received the parastylar apex of M3. A
similar notch is not present on the M2 of KU no. 11210 nor
indicated in the illustrations of the M2 of Princeton no.
13585. The coronal dimensions of UCM no. 21073 (table 1) do
not appear to differ significantly from those of the M2's of
KU no. 11210 and the type specimen of _Sinclairella
dakotensis_.