STERRHOLOPHUS FLABELLATUS. 147 



number of vertical series of teeth in each jaw. The form and characters of the maxillaries are 

 well shown in fig. 22. 



The premaxillaries. — The principal characters of the premaxillaries are well shown in fig. 28. 

 They had a widely extended contact with each other and together they formed an imperfect 

 anterior median septum. Anteriorly and superiorly they each send upward a strong pillar, 

 which is inclosed by and gives support to the distal extremity of the nasal, with which it is 

 united by suture only. Below the nasals on the anterior margin of the premaxillaries there is 

 an extended articular surface for contact with the rostral, and this is continued backward on 

 the inferior border of the premaxillary both on its external and internal margin. Posteriorly 

 there is a slender ascending process which is wedged in between the maxillary and nasal and 

 reaches almost to the lachrymal foramen. About midway between the anterior and posterior 

 ascending processes a third median process is given off from the superior margin of the premaxil- 

 lary. This is directed forward and upward and joins the anterior process just below the nasals 

 and gives additional support to those elements. 



The transverse bones. — The transverse bones are reduced to elongated flattened bones 

 located one on the supero-external surface of the lower posterior process of each maxillary as 

 shown at tr in fig. 21. They are somewhat thickened on the external median border but are 

 rather thin at either extremity. They have a slight contact with both the pterygoids and 

 palatines, but fulfill none of the functions of the transverse or transpalatine bones as seen in the 

 crocodiles and most modern reptiles. So rudimentary are the transverse bones in the Ceratopsia 

 that they might best be described as vestigial. 



The palatines. — These are broad, thin bone#, each consisting of two plates, one vertical and 

 longitudinal, running in a plane nearly parallel with the longer axis of the skull, the other vertical 

 and transverse and occupying a plane extending nearly at right angles to the longer axis of the 

 skull. Along their inferior borders the palatines embrace the superior border of the internal 

 portions of the maxillaries. The vertical and longitudinal portions of the palatines are in contact 

 posteriorly with the pterygoids. The vertical and transverse portion has a thickened, free 

 inferior border; laterally it gives support to the lachrymal, the superior process of the maxillary, 

 and apparently also to the prefrontals. At the anterior angle just where the transverse and 

 longitudinal portions of the palatines meet they are produced into long pointed processes which 

 fit nicely into notches on the supero-internal surfaces of the maxillaries, as is well shown in fig. 20. 

 Just above this process the anterior border of the palatine incloses posteriorly an elongated 

 oval foramen which is bounded anteriorly by an ascending process of the maxillary. This 

 foramen passes from the cavity of the mouth to the infratemporal cavity, and may be called the 

 maxillo-palatine foramen. It is situated as shown at v, fig. 20, just below the much smaller 

 infraorbital foramen, from which it is separated by a slender process of the maxillary. Above, 

 the palatines approach each other and embrace between them the vomers, the superior extremity 

 of the pterygoids, and the median blade of the alisphenoids. The articulation of these various 

 elements with one another is well shown in figs. 20 and 21. 



The pterygoids. — The pterygoids are very irregular in form, as shown in fig. 23. Inferiorly 

 and posteriorly they are broad and thin, with the posterior portion expanded so as to form a 

 broad wing, convex externally and concave internally. The antero-inferior angle of this portion 

 is thick and is lodged in a deep notch on the internal side of the quadrate, while above and 

 posteriorly the broad, thin wing of the pterygoid overlaps on the inner side the thin angular 

 part of the quadrate, as shown in outline in fig. 20. On the superior portion of the concavity on 

 the inner side of this portion of the pterygoid there is a large rugosity for contact with the 

 anterior face of the distal end of the basisphenoid process. Anterior to this broadly expanded 

 portion of the pterygoid and separated from it by a deep rounded notch is the antero-inferior 

 process of the pterygoid which is in contact with the transverse and curves round the posterior 

 extremity of the inferior branch of the maxillary so as to receive a portion of its inner and 

 superior surface into an elongated, rather deep, and rugose cavity. The anteroinferior 



a Here Hatcher's revised typewritten manuscript ends. 



