214 REPTILIA. 



front, and these fuse together in old individuals. The nasal bones are 

 large and massive and much thickened anteriorly to support the nasal 

 horn-core. The frontals are small, and the enormous horn-cores above 

 the eyes, which are hollowed at the base, are supported by the enlarged 

 postfrontals, partly also by the supraorbitals and postorbitals. The post- 

 frontals meet in the middle line, and at the median point of their union 

 with the parietals in young individuals there seems to be a perforation 

 which may perhaps be interpreted as a "pineal foramen." The great 

 posterior crest of the skull is formed chiefly by the parietals, and the 

 narrow supratemporal vacuity on each side is bounded outwardly by a 



FIG. 133. 



Triceratops serratus ; diagram of skull from the superior aspect, one-twentieth 

 nat. size. Cretaceous; Wyoming, c, supratemporal vacuity; d, epijugal 

 plate ; e, epi-occipital plates ; /, frontal ; fp., postfrontal ; h, horn-core ; 

 h', nasal horn-core ; j, jugal ; 7/t, maxilla ; n, nasal ; p, parietal ; pf., pre- 

 frontal ; pm., premaxilla ; r, rostral bone ; s, squamosal ; x, perhaps a 

 pineal foramen. (After Marsh.) 



separate squamosal. The brain-cavity is especially diminutive, smaller 

 in proportion to the skull than in any other known reptile. A tooth- 

 less predentary bone is observed in front of the mandible, and the 

 dentary rises behind into a large coronoid process. Articular, angular, 

 surangular, and splenial elements are distinguishable. The teeth are 

 arranged in a single functional series on the maxilla and dentary, and 

 are not displaced vertically by their successors, but from the side. They 

 are broader than long and implanted by a forked root, the inner and 

 outer branches of which are described as fixed in more or less distinct 

 sockets ; the dental crown is adapted for a herbivorous diet. The atlas 



