156 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxii. 



^llpo. /.). He also omitted the suture between po.stfrontal and 

 frontal, which is plainly shown on the specimen. (See Plate XIII.) 

 While there is no positive evidence that the postfrontal is now cor- 

 rectly identified, j^et after a comparison with other reptilian skulls, 

 both fossil and recent, it appears to the writer the most logical arrange- 

 ment of this region of the skull. The postfrontal at its anterior 

 extremity articulates with the frontal and parietal, with the former by 

 a long lapping suture. (See Plates XII and XIII.) Its inner margin 

 constitutes the outer posterior boundary of the supratemporal fossa. 

 At the posterior boundary of this fossa an inwardly directed expansion 

 of this bone unites with the squamosal. Its anterior surface enters 

 into the boundary of the orbital cavity. 



The hasisphenoid articulates posteriorly with the basioccipital and 

 exoccipitals and laterally with the alisphenoids and orbitosphenoids. 

 The basipterygoid processes are broken oif and gone. 



The alisphenoid and orhitosphenoid bones are present, but their 

 boundaries can not be definitely defined at this time. Where the 

 orhitosphenoid articulates with the ventral surface of the frontals are 

 several notches or openings leading into the cerebral cavity. 



OPENINGS IN THE SKULL. 



The, fora7nen magnum, is wholly inclosed by the exoccipitals. The 

 outline of the foramen has been distorted somewhat by crushing, but 

 it appears higher than wide and was probably oval, as represented in 

 the restored drawing. (See fig. 3.) 



The supratemporal fossa is suboval in form and opens outward 

 and backward. It is bounded anteriorly by the parietal and post- 

 frontal; the inner wall is formed by the parietal and bounded posteri- 

 orly by the squamosal, its outer wall by the postfrontal. 



Onl}^ the superior boundary of the orMtal camty is shown in this 

 specimen. This is concave antero-posteriorly and is formed above by 

 the frontal and postfrontal. The inner posterior wall is bounded 

 chiefly by ali- and orbitosphenoids. See Plate ^WO. sp. and Al. up. 



There is no evidence of a pineal foramen in M. agilis. However, 

 Marsh makes the following observation:'^ '"In one specimen of Moro- 

 saurus, a similar opening has been observed, but in other Saurojjoda 

 the parietal bones, even if thin, are complete." He probably refers 

 here to the skull of Morosaurus gra7idis, of which he figures a poste- 

 rier portion in the Dinosaurs of North America. Plate XXX, fig. 2. 

 The presence of a well-defined pineal foramen in the skull of Moro- 

 saurus grandis appears now to be definitely determined by Professor 

 Osborn after a preliminary study of three Morosaurus skulls, of which 

 he has published a figure of the more complete one.* He makes the 



aAm. Jour. Sci., XXVII, February, 1884, p. 162. 

 6H. F. Osborn, Nature, LXXIII, 1906, p. 283, fig. 2. 



