34 BULLETIN 89, UNITED STATES NATIONAL MUSEUM. 



No. 4934, that part of the bone visible on the outer surface is an oblong, oblique 

 plate, the upper border of which is notched by the nostril. Posteriorly it sends 

 backward a gradually narrowing process which is intercalated between the nasal and 

 maxillary, terminating at a point about midway between the narial and orbital 

 openings. The regularly curved, anterior end of the premaxillary is continued 

 upward into a posteriorly directed process which overlaps the anterior end of the 

 nasal, thus completing the boundary of the narial orifice. On the anterior ends of 

 the cojoined premaxillae the median surface is transversely concave, leaving two 

 diverging ridges extending down toward the latero-external angles of the nose. 

 The surface of these bones is comparatively smooth, not rugose as in Camptosaurus. 

 The palatal surface is hollowed out transversely. The right premaxillary of No. 

 4934 has an alveolar border 61 mm. in length. The greatest width of the articu- 

 lated premaxillae is 59 mrn. The more important features of the premaxdlary 

 are well shown in plates 5 and 6, and plate 9, figure 1. In No. 4935 the postero- 

 internal borders are shown to be in contact with the vomers. 



Maxillae (m.). — The maxillary is a large bone of rudely subtriangular outline, 

 whose outer surface forms the greater part of the cheek portion of the skull (pi. 5, 

 m). Its superior border meets the premaxillary, nasal, and lachrymal bones. 

 Posteriorly it articulates externally with the jugal and internally with the palatines. 

 In advance of the dentigerous portion of the maxilla, a triangular flattened extension 

 is applied to the lower median surface of the premaxillary, terminating somewhat 

 forward of the center of the narial opening. In specimen No. 4935 this end appears 

 to be in contact with the vomer. The right maxillary of No. 4934 has a height of 

 54 mm. above the dentigerous border at its center. The dental or alveolar border 

 is swollen transversely, the teeth being placed on the internal margin. In this 

 maxillary I am able to count an unbroken series of 22 teeth and there may have 

 been two or three more on the anterior end. The 22 teeth occupy a longitudinal 

 space of 129 mm. A fragmentary maxilla belonging to specimen No. 6645 shows 

 the usual row of foramina which pierce the bone above the level of the tooth roots. 

 The greatest length of the right maxillary of No. 4934 is 214 mm. 



Jugal (j.). — The jugals are preserved in situ in No. 4934, as shown in plate 5, j. 

 They are tang slender bones with expanded ends, which form the lower boundaries 

 of the orbits. On the upper posterior end an ascending process underlaps a descend- 

 ing process from the postorbital. and with the quadratojugal completes the post- 

 orbital bar. Posteriorly it meets the quadratojugal by squamous suture. An- 

 teriorly, it appears to overlap the maxillary and lachrymal by a flattened end. In 

 his published drawings of this skull, Marsh indicates the anterior termination as 

 being posterior to the anterior boundary of the orbit, but a close examination of the 

 specimens shows that they extended some distance in advance of this point, as 

 indicated in the corrected drawing (pi. 5). The greatest length of the right jugal 

 of No. 4934 is 109 mm. 



Quadratojugal (qj.). — The quadratojugal, as shown by specimen No. 6645 

 (see qj., fig. 6), is a small irregularly shaped bone, having a much expanded pos- 

 terior end which articulates suturaliy with the lower postero-external side of the 

 quadrate. A comparatively thin, finger-like extension is directed forward and laps 

 along the inner side of the posterior extension of the jugal. In this specimen it has a 

 greatest length of 50 mm. 



