_Description_ (based on 3 maxillary fragments, see Table 1).--Each of the maxillary fragments bears four thecodont teeth. These are conical, slender and sharply pointed; in their distal third they are slightly recurved, laterally compressed, and have anterior and posterior non-serrated cutting edges. In medial aspect at their bases, the teeth are longitudinally striated. The bases of the teeth are circular in cross-section and are slightly bulbous. There is no caniniform enlargement of any of the teeth, the longest tooth of each fragment being differently placed in the series of teeth and little longer than the others. There is no swelling on either the internal or external surfaces of the maxillae. The teeth are in a continuous series; no diastema or maxillary step is evident. [Illustration: FIGURES 1-3. _Delorhynchus priscus_, lower Permian, 6 miles north of Fort Sill, Comanche County, Oklahoma. All x 3. FIG. 1. KU 11117 (type specimen), lateral view of left maxilla. FIG. 2. KU 11118, lateral view of right maxilla. FIG. 3. KU 11119, lateral view of left maxilla.] The fragments have been broken along similar lines of fracture, and each is approximately rhomboidal in shape. The maxilla encircles the posterior border of the naris and extends dorsally above the naris to an extent sufficient to indicate the probable exclusion of the lacrimal bone from the narial border. At the posteroventral corner of the naris a foramen opens onto the lateral surface of the maxilla. The opening is the entrance to a canal that runs posteriorly above the tooth-row throughout the length of each specimen. Beneath the naris the maxilla extends as a broad tapering shelf, the ventral surface of which articulates with the premaxilla. The narial rim is wide, but wider ventrally than dorsally. The plane of the narial rim is oblique to the lateral surface of the maxilla. The external surface of each fragment is grooved and pitted. The ossification of each fragment appears to have been complete. TABLE 1.--DIMENSIONS, IN MILLIMETERS, OF THREE MAXILLARY FRAGMENTS OF DELORHYNCHUS PRISCUS Key: A. Anterior height of fragment B. Posterior height of fragment C. Length of fragment at tooth-row D. Dorsal length of fragment E. Mean length of teeth F. Anterior width of naris ============================================================ CATALOGUE NUMBER | A. | B. | C. | D. | E. | F. AND MEAN | | | | | | -----------------+------+------+------+------+------+------ KU 11117 | 6.0 | 8.0 | 6.0 | 8.0 | 3.0 | 3.0 KU 11118 | 6.0 | 6.0 | 9.0 | 8.0 | 2.0 | 3.0 KU 11119 | 6.6 | 8.0 | 10.0 | 11.0 | ? | 4.6 -----------------+------+------+------+------+------+------ Mean | 6.2 | 7.3 | 8.3 | 9.0 | 2.5 | 4.5 -----------------+------+------+------+------+------+------