EXPLANATION OF PLATE X. 



Cranial bones of Protosiega gigas, Cope, one-half natural size. 



Fig. 1. Maxillary bone: a, from without; 6, from within. 



2. Deutary bone : a, from without ; b, from witbiu ; c, anterior view. 



3. Posterior portion of mandibular ramus from within : a, dentary ; 6, articular ; c, angular bones. 



4. Posterior portion of mandibular ramus from the outside ; letters the same. 



5. Quadrate aud pterygoid bones of the. right side from within. 



6. Quadrate bone of the same side from without. 



