PLATE I. 



ODONTOENITHES. 

 Skull and lower jaws of Hesperornis regalis Marsh. 



All Figures Natural Size. Page. 



Fig. 1. — Skull ; lateral view, seen from the left. Top of cranium crushed, - 6 



pm — Premaxillary. 

 pms — Maxillo-premaxillary suture. 

 t — Tooth, in position in maxillary. 

 an — Anterior nares. 

 n — Nasal bone. 

 I — Lachrymal bone. 

 of — Iuter-orbital fenestra. 

 qj — Quadrato-jugal bone. 

 q — Quadrate bone. 

 bo — Basi-occipital. 



Fig. 2. — Left lower jaw ; lateral view of external surface, . . . . 11 



t — Teeth still in place. 



Fig. 3. — Left lower jaw ; seen from above, -.. : .. 11 



a — Groove for the teeth, with indications of sockets. 



b —Groove for the reception of the upper teeth when the jaws were closed 



c — Anglo of mandible. 



Fig. 4. — Right lower jaw ; inner side, 11 



d — Symphysial surface, showing that the rami were not coossified, but united 



only by cartilage. 

 e — Imperfect articulation between splenial and angular elements. 

 f — Articular surface for quadrate. 



Fig. 5. — Skull ; seen from above, cranium crushed, 6 



o —Orbit. 



tf — Temporal fossa. 



Note. — The dotted outlines in this and the following plates represent portions wanting in the specimens described. 

 The surface covered by oblique bars (as in figures 2 and 4) indicates portions concealed by the adhering matrix, or 

 otherwise obscured. 



