THE SKULL. 



27 



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 sur- 

 face into an elongated, rather deep, and rugose 

 cavity. The antero-inferior margin of each of 

 these two inferior processes of the pterygoids 

 are produced into two broad laminae which run 

 obliquely upward across the inner surface of the 

 bone, the free borders curving toward one another 

 and partially arching over a deep canal, broad 

 below but constricted above, which may have 

 functioned as the eustachian canal. Above the 

 upper limits of these two laminae the pterygoids 

 are much constricted, and the superior process pre- 

 sents a smooth, flattened, external articular sur- 

 face for contact with the palatines, while on their 

 internal sides they articulate with one another 

 through short, grooved articular surfaces, which 

 are partially interrupted near their superior borders by a single large median foramen. The 

 sutural surface for contact with the palatine is projected above that which opposes the other 

 pterygoid, and there is a small foramen on the free border between these two surfaces, as shown 

 in fig. 23. The anterior edge of the pterygoid extends forward and forms an elongated plate, 

 crescentic in outline. This articulates with the palatines above and with the maxillary below, 



as shown in figs. 21 and 24. Just above the maxillary a 

 „.-''" i large foramen passes between the pterygoid and palatine. 



Anteriorly this foramen is bounded by the posterior border 

 of the palatine and posteriorly by the anterior border of the 

 pterygoid. At the extreme top the pterygoids articulate 

 externally with the palatines and to a slight extent also with 

 inferior lateral projections from the vomers, while medially 

 they are in contact with one another save for the interrup- 

 tion due to the median foramen already mentioned, which 

 doubtless served to transmit the sensory nerves to the 

 palate. These characters are especially well represented in 

 the type of T. horridus, No. 1820, Yale Museum collection, 

 and are shown here in figs. 24 and 25, drawn from that skull. 



THE PALATINES. 



Fig. 22.— External view of right maxillary of type of Triceratops 

 flabellatus.No. 1821, Yale Museum, e, Anterior end; p, pos- 

 terior end; if, infraorbital foramen. One-eighth natural 

 size. 



Fig. 23. — Inner view of left pterygoid of type of 

 Triceratops flabellatus, No. 1821, Yale Mu- 

 seum, q, Angle for articulation with notch 

 in quadrate; m, process embracing poste- 

 rior process of maxillary; a, surface for 

 contact with basisphenoid process; s, sur- 

 face for opposite pterygoid; /, interptery- 

 goid foramen; pi, palatine border; pp, 

 pterygopalatine foramen; ec, (?) eusta- 

 chian canal. One-eighth natural size. 



These are broad, thin bones, 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 trans- 

 verse 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 portion of 

 the maxillaries. The vertical and longitudinal portion of the palatines is 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 apparent!}?" 

 also to the prefrontals. At the inferior and anterior angle, just where the transverse and longi- 



