^CEEDINGS OF THE NATIONAL MUSEUM. 



VOL. XXXVI. 



^ ^ition and thus exposes the ventral sutural surface 

 m juxtaposition, would unite closely with the transversely 

 onecl dorsal surface of the prootic. Anteriorly it presents a 

 thickened sutural surface for union with the alisphenoid. BeloAv, 

 the anterior border is deeply notched by the foramen ovale. The 

 upper exterior surface forms part of the lower inner boundary of 

 the supratemporal fossa. On the lower median part of the lateral 

 surface is a deep, vertical groove leading up to a foramen entering 

 the brain case, which, from its position, should represent the exit of 



the seventh or facial nerve. 

 -^^ (See VII, fig. 5.) 



In the skull of Trieera- 

 tops, Hatcher « was un- 

 able to distinguish the pro- 

 otic, and in Diplodocvs, 

 Holland '' did not detect 

 its presence. In both 

 cases the region which it 

 should occupy if present 

 was considered a part of 

 the alisphenoid. Fro m 

 t h e facts brought out 

 by a study of the skull 

 of Camptosaurus which 

 shows the presence of the 

 otic elements in the di- 

 nosaurian skull, I believe 

 they will be found in both 

 of the forms mentioned 

 above. In this connec- 

 tion it is of interest to 

 quote from Huxley '' who 

 says : " The prootic is, in 

 fact, one of the most constant bones of the skull in the lower verte- 

 brates, though it is commonly mistaken, on the one hand for the 

 alisphenoid, and on the other for the entire petro-mastoid." 



The epiotic I am unable to recognize and if present, it occurs, as 

 in most reptiles, fused with the supraoccipital, and no longer recog- 

 nizable. 



Parietal. — As in most reptiles (excepting Chelonia, IchtJiyosauria, 

 and some Thero?)iorpha), the parietals in Camptosaurus are united. 

 ( See Plate 10. ) An examination of two disarticulated skulls in which 



" Mon. V. S. Geol. Survey, XLIX, 1907. p. IT. 



^Memoirs Carnegie Museum, II, No. 6. 1906, p. 23(), fig. 8. 



^ The Anatomy of Vertebrated Animals, 1872, p. 26. 



Fig. 5. — Lateral view of posterior portion of 

 SKULL of Camptosaurus dispar Marsh. Cat. No. 

 .5473, U.S.N.M. ; g nat. size. A1. sp., alisphe- 

 noid ; bo, BASIOCCIPITAI, ; hS, BASISPHENOID ; c, 

 groove LEADING TO FORAMEN THROUGH WHICH THE 

 CAROTID ENTERS PITUITARY FOSSA ; CXO, EXOCCIPI- 

 TAL ; OC, OCCIPITAL CONDYLE ; poC, PARAOCCIPITAL 

 PROCESS OF OPISTHOTIC ; p, pt, PROCESS FOR PTERY- 

 GOID ; pro, PROOTIC ; s, sutural surface of 



SUPRAOCCIPITAL, CRUSHED UPWARD FROM ITS NOR- 

 MAL POSITION IN RELATION TO THE PROOTIC WITH 

 WHICH IT UNITES ; SO, SUPRAOCCIPITAL ; V, FORAMEN 

 OVALE ; VII, FORAMEN FOR SEVENTH OR FACIAL 

 NERVE ; VIII, INTERNAL AUDITORY MEATUS ; IX, X, 

 FORAMEN LACEBUM POSTERIUS ; XII, HYPOGLOSSAL 

 FORAMEN, AND FORAMEN FOR EXIT OF VEIN. 



