104 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxvi. 



however, to such a height as the hinder pair. These probably repre- 

 sent the cerebral hemispheres. As mentioned above, there is a fora- 

 men j)laced at the front of each cerebral excavation. It probably trans- 

 mitted blood-vessels; for certainly no nerve left that part of the brain. 



The extensive space between the cerebellar processes and the cere- 

 bral hemispheres was probably mostly occupied by the optic lobes 

 (Plate 3, fig. 1, op. I). Doubtless, an exact model of the brain 

 would show here and farther in front a deep longitudinal cleft ; also 

 transverse clefts in front of the cerebellum and behind the cerebral 

 hemispheres. 



In Marsh's figure of the cast of the brain the olfactory lobe seems 

 to be too long. In the figure here shown (Plate 3. figs. 1, 3, olf. I) 

 it is a little too short. Its length is 55 mm. AMiere it escaped from 

 the olfactory canal its divisions are seen to have been directed to the 

 right and left, respectively. 



THE BRAIN-CASE AND THE l^AIN OF TRIPERATOPS SFLCATTTS. 



In the U. S. National Museum there are important parts of a skull 

 that has been identified as that of T. sulcatum. Th§ specimen is Cat. 

 Xo. 4286, U.S.X.M. It was collected by Mr. Hatcher in the so- 

 called Laramie beds of Converse County, Wyoming, for the U. S. 

 Geological Survey. Hatcher has presented a figure of the horn 

 cores." The brain-case, including the occipital condyle, has been sawed 

 from the liorn cores along a horizontal plane that passed somewhat 

 above the cerebral hemispheres. Afterwards the brain-case has been 

 divided along the median plane, thus exposing the brain cavity. 



The sutures of this brain-case have been mostl}', if not altogether, 

 obliterated. The general structure is the same as that of T. .serrafus, 

 but there are some minor differences of some importance. The 

 orbitosphenoidal segment (Plate 2, fig. 2, orh.'^) is not so extensively 

 developed, since nearly the whole of the olfactorj^ lobe lay in front 

 of the orbitosphenoids. The supraoccipital bone (Plate 2, fig. 2, 

 soc) is thicker than in T. sei'ratu.s. A part of the parietal is present. 

 AMiether or not it was consolidated with the supraoccipital is uncer- 

 tain, but there seems to be an open suture. In front of its articula- 

 tion with the supraoccipital a median sinus (Plate 2. fig. 2, sin) 

 descends and is separated from the brain cavity by bone only 5 mm. 

 thick. This represents probably the hinder of the two sinuses shown 

 in fig. 33 of The Ceratopsia and indicated by the letter X. It seems 

 to be bounded beloAv by the parietal, and by possibly a pa#t of the 

 frontals. It is doubtful whether or not the orbitosphenoids of this 

 species met above the olfactory lobe. 



The presphenoid lacks much of being as large as it is in T. serratus. 

 The basisphenoid (Plate 1, fig. 2, has; Plate 2, fig. 2, has) descends 



"The Ceratopsia, p. 134, fig. 113. 



