98 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxvi. 



into two, one for each side. Hatcher" says that in Torosaurus hifufi 

 there is a j^air of these foramina, separated by a thick j^artition of 

 bone that marks the median line of the skull. 



Xow, to the writer it seems perfectly clear that the foramen in 

 question represents the supratemporal fossse of the alligator and of 

 various other reptiles. The bone rising up and dividing the fossa 

 into two, either at the surface or deeper down, Avill almost certainly 

 be found to be the true parietal. Through the enormous thickening 

 of the postfrontals the parietal has been crowded from the upper sur- 

 face of the skull of Tricerafops and the two supratemj^oral fossa? have 

 been pushed into one at the midline. 



As regards the fossa? in the frill, they may be explained as gaj)s 

 between the squamosal and the supratemporal of each side. Hatcher ^ 

 tells that these openings conununicated with the temporal fossa? and 

 with the cavities at the bases of the horn cores. These passages must 

 represent the posttemporal fossfo. Possibly through them passed 

 branches of the temporal arteries to spread themselves over the upper 

 surface of the frill. 



Hatcher has, in my o]:)inion, erred in his interpretation of the l)rain- 

 case of the Ceratopsia. His errors have arisen jiartly from the nearly 

 complete or complete absence of sutures in the skulls examined and 

 partly from his not having recognized the differences between the rep- 

 tilian skull and that of the mammals, a group Avith which he was 

 more familiar. The latter cause of error is shown in his failure to 

 mention the prootic bone, one of the most constant in the reptilian 

 skull, and in his si)eaking of all of the l)ones of the skull in front of 

 the exoccipitals as the alisphenoid, as if it corresponded to the sphe- 

 noid of human anatomy. Again, on page 30 of The Ceratoj^sia, the 

 organ of hearing is misunderstood because it did not present mam- 

 malian characters. 



The specimen before me (Cat. No. ■2410. U.S.X.M.) appears to agree 

 quite closely with Hatcher's fig. 8 representing the same parts of 

 2\ faheUati/s, although the latter is about a third larger than Xo. 

 2410. Xow, in both skulls there are undoubtedly present the basi- 

 occipital, the basisphenoid, the presphenoid, exoccipitals, prootics, 

 alisphenoids, and orbitosphenoids. In fact, it appears that the brain- 

 case of the Ceratopsia was the most complete of any known reptile. 



Inasmuch as the sutures l)etwee7i the bones are mostly effaced, we 

 are able to determine their limits only approximately, guided partly 

 by the orifices for the nerves, partly by the courses of the sutures in 

 living reptiles, but especially by aid from the fine skull of Campto- 

 saurus now being studied by Mr. Charles "\V. Gilmore, who has gener- 

 ously allowed the writer to examine it. 



''Tlie Ceratopsia, p. 151. «* Ideui, p. 125. 



