216 



Meviews — Prof. 0. C. Marsh's Dinocerata. 



" These bones are a peculiar feature in the skull of Dinocerata, 

 and may be called the pre-nasal bones. In very young animals, they 

 are unossified ; in adult animals they are distinct; but in very old 

 animals they become coossified with the nasals, and with each other. 



"The frontal bones in Dinoceras mirahile are shorter than the nasals 

 (see Fig. 4). In all the known skulls of the Dinocerata, the median 

 suture uniting the two frontals is entirely obliterated. The suture 

 joining them with the nasals in front, and with the maxillaries on. 

 the side, is distinct in the type of Dinoceras. 



Fig. 4. — View of upper- surface of skull of 

 Dinoceras miiabile, Marsh, with brain-cast iu 

 natural position. /, frontal bone ; ni, maxil- 

 lary bone ; m', maxillary protuberance ; n, 

 nasal bone ; n , nasal protuberance ; p, 

 parietal bone; p', parietal protuberance ; 

 pm, premaxillary bone ; s, supra-occipital 

 crest. 



Fig. 5. — Skull of a young 

 specimen of Dinoceras distavs, 

 Marsh, seen from above ; with 

 brain-cast in natural position. 

 Both Figs. 4 and 5 are one- 

 eighth natural size. The letters 

 refer to the same parts of the 

 skull in both fisrures. 



'* The maxillary bones form a large portion of the lateral surface 

 of the skull. They contain all the teeth, except those of tlie lower 

 jaw, and they also expand into the large median pair of osseous 

 elevations, or horn-cores. 



"In one young specimen, the fronto-parietal suture is still open 

 and passes in a nearly straight line across the top of the cranium 



