e no bar to its inclusion in the Nitosauridae
(Edaphosauria). The marginal teeth of _Delorhynchus_ are simple and
primitive, being much like those of the nitosaurids that are described
in the literature.

The large narial opening and its posterior, dorsal and ventral enclosure
by the maxilla, the infraorbital canal, and the sculptured external
surfaces of the maxillary fragments indicate that _Delorhynchus_, in
these features at least, is close to achieving the caseid grade.

Family SPHENACODONTIDAE

=Thrausmosaurus serratidens= new genus and new species

(_Thrausmosaurus_ is formed from the neuter Greek noun, _thrausma_,
meaning fragment, and the masculine Greek noun, _sauros_, meaning
reptile. The specific name, _serratidens_, is formed from the Latin
_serratus_, meaning serrate, and the masculine Latin noun, _dens_,
meaning tooth. The specific name is used as a substantive in apposition
with the generic name.)

_Type specimen._--Fragmentary left dentary, bearing five teeth, the
most posterior of which is broken at the base, KU 11120.

_Referred specimens._--Fragmentary ?left maxilla, having two teeth, KU
11121; fragmentary left dentary having two teeth, KU 11122.

_Horizon and locality._--From the early Permian fissure deposits in the
Arbuckle limestone of the Dolese Brothers Limestone Quarry,
approximately 6 miles north of Fort Sill, in sec. 31, T. 4N, R. 11 W,
Comanche County, Oklahoma.

_Diagnosis._--Small; teeth thecodont, compressed laterally, recurved
distally, and bearing anterior and posterior cutting edges; anterior
serrations limited to recurved portions of teeth, posterior serrations
extending nearly entire length of teeth; lateral compression of teeth
more pronounced medially than laterally; bases of teeth expanded.

_Description._--The type specimen is 16 mm. long. It bears five teeth
that are implanted in a straight row. Empty sockets are present between
the first and second teeth, and the third and fourth teeth. The first
tooth is 3.0 mm. long, the middle two are each 2.5 mm. long, and the
fourth tooth is 2.0 mm. long. The fifth tooth is broken off at its base.

The empty sockets are large. The mouth of each is circular and
approximately 2.0 mm. in diameter. Both sockets are 1.25 mm. deep. The
bases of the teeth are expanded to fill the sockets, although the blades
of the teeth arise from only the lateral portions of the bases. The edge
of the dentary rises above the bases of the tee