36 BULLETIN 89, UNITED STATES NATIONAL MUSEUM. 



Pterygoids (pt.). — The pterygoids are irregularly shaped bones, as shown in 

 ft., plate 7. On the latero-posterior borders two diverging processes are developed, 

 which extend backward and outward, and articulate on the inner side by a long, 

 lapping suture, witn anteriorly directed processes from the quadrates. On the 

 internal posterior border, where these processes leave the body of the pterygoid, 

 it unites with the descending basisphenoid processes. On the latero-anterior 

 borders two spatulate processes are given off which extend forward and outward. 

 Whether these processes unite with the palatines, or whether there is a transpalatine, 

 as in the crocodile and some other reptiles, can not be determined from this speci- 

 men, because of the incomplete and damaged condition of tliis region. On the 

 median ventral surface of the pterygoids a downwardly directed angular process 

 is developed. Tliis process is strongly braced by vertical lamina extending down 

 on the sides and back (fig. 2, pi. 9). Above and behind this process and at the junc- 

 tion of the pterygoids with the basisphenoid is a large opening that appears to lead 

 forward into a chamber above the pterygoids, and which may represent the pos- 

 terior narial opening. 



From the forward face of the descending process just described is a vertical 

 plate of bone extending well forward in the roof of the mouth. It is likely that 

 a portion of this plate represents the vomers, but the sutural junction of these ele- 

 ments can not be determined from this specimen. 



Palatines (pi.). — That the palatines are present there can be no doubt, but it 

 is impossible from the present specimens to get anything like an adequate idea of 

 their extent, or relationships to the surrounditig elements. The irregularly tri- 

 angular elements in front of the pterygoids, as represented in plate 7, were identified 

 by Marsh as the palatines. We can not be certain, however, that the openings in 

 the bone and their inner contours exist as depicted. 



Vomer (v.). — Specimens Nos. 4934 and 4935 (v., pi. 7) show the vomer to have 

 been present in Stegosaurus, but it is impossible from available specimens to deter- 

 mine their true extent or relationships. 



Epipterygoid. — The damaged condition of this part of the palate in the skull 

 of No. 4934 makes it impossible to positively identify this element. 



Measurements of shull of Stegosaurus stenops, No. 4934- Type. 



mm. 



Greatest length of skull, taken at center 414 



Greatest expanse of paraoccipital processes 142 



Greatest expanse above center of orbits 156 



Greatest expanse above center of nares 18 



Distance from posterior border of orbit to posterior extremity of squamosal 104 



Distance fi-om anterior border of oi-bit to anterior extremity of premaxillae 251 



Distance from extremity of premaxillae to distal extremity of quadrate 400 



Distance from distal end of quadrate to top of skull 149 



Height of skull over center of maxillary (estimated) 71 



Height of snout at anterior border of narial opening 40 



Height of skull with lower jaw, measurement taken at center of orbit 144 



Same measurement taken below posterior border of nares 90 



Transverse diameter of occipital condyle 39 



Antero-posterior diameter of orbit 91 



Antero-posterior diameter of narial opening 75 



