OSTEOLOGY OF THE ARMORED DINOSAURIA. 



27 



Known elements of the Stegosaurian skull. 



Alisphenoid al. sp 



Angular an 



Articular ar 



Basisphenoid bs 



Basioocipital bo 



Deutary d 



Exoccipital ex. o 



Frontal / 



Jugal j 



Lachrymal I 



Maxillary m 



Nasal n 



Orbitosphenoid or.sp 



Palatine pi 



Prespheuoid p.sp 



Paraoccipital (opisthotic) p.oc 



Parietal p 



Postorbital po 



Postfi-ontal po./ 



PostsLipraorbital po. so 



Prefrontal pf 



Preiaaxillary pm 



Prearticular p.ar 



Predeutavy pd 



Presupraorbital p. so 



Prootic pro 



Pterygoid pi 



Quadrate q 



Quadratojugal ; qj 



Splenial s 



Squamosal sq 



Surangular sa 



Supraoccipital so 



Vomer v 



Fig. 3. — SkullofStegosaurusstenops Marsh. Lateral view. Type. Cat. no. 4934, U.S.N. M. 

 Less than } nat. size. a. Anterior nares; an, angular; ar, articular; b, orbit; c, infra 



TEMPORAL FOSSA; d, DENTARY; j, JUGAL; I, LACHRYMAL; m, MAXILLARY; 71, NASAL; OC, OCCIPITAL 



condyle; p.ar, prearticular; p<1, predentary; pf, prefrontal; pm, premaxillary; po, 

 postorbital; p. oc, paraocctpital; po.so, postsupraorbital; p.so, presupraorbital; q, quad- 

 rate; qj, quadratojugal; s, splenial; so, surangular; sq, squamosal. 



Description. — A study of this material shows that Marsh's figures of the skull 

 of Stegosaurus stenops, which have appeared in numerous American and European 

 publications, are incorrect in many of then - details. The inaccuracies are in great 

 part due either to the complete coalescence or to the obscure condition of many of 

 the sutures, and also in some instances to a wrong interpretation of cracks in the 

 skull (No. 4934) as representing sutural articulations. These errors have been cor- 

 rected in the drawings, and a more detailed mention of them wall follow in the 

 discussion of the separate skull elements. 



Viewed from the side (pi. 5 and fig. 3) the skull of Stegosaurus is long and slender, 

 the facial portion being especially produced. With the jaw in position the outline of 

 the skull is wedge shaped, the apex being directed forward. The nares are long, 

 and, as in Camptosaurus, are situated well in front. The orbit is large, measuring 

 about one-fifth of the total length of the skull, and placed well back. The infra- 

 temporal fossae are somewhat smaller. Marsh has pointed out that "all of these 



