418 0. G. Marsh — Characters of the Ceratopsidce. 



Aet. LII. — Additional Characters of the Ceratopsidce, with 

 notice of New Cretaceous Dinosaurs ; by O. C. Marsh. 

 (With Plates Y-VIL) 



The gigantic horned Dinosaurs from the Laramie, which 

 have already been described by the writer, in this Journal,* 

 are still under investigation, and many new points in their 

 structure have recently been brought to light. Some of these 

 are here placed on record for the first time, and taken in 

 connection with those previously made known by the writer, 

 indicate that the group is a very distinct one, worthy to be 

 called a sub-order, which may be termed the Ceratopsia. 



Some of the main characters of this group are shown in the 

 sjDecimens figured in the accompanying plates, and others will 

 be fully represented in the illustrations of the memoir now in 

 preparation. 



The new forms described make it still more evident that the 

 Cretaceous Dinosaurs, of which so little has hitherto been 

 known, are quite as remarkable as their allies from the Jurassic. 



Skull of Triceratops. 



In addition to the armature of the skull of Triceratops, 

 already described, another ossification has been found attached 

 to the lower extremity of the jugal bone. This is a separate 

 element, like the epoccipital bones, but in very old animals, it 

 is coossified with the jugal, on which it rests. The external 

 surface is rugose, indicating that it was covered with horn. It 

 formed an anterior extension of the lateral series of ossifications 

 on the squamosal, and served to protect the side of the head. 

 This element may be called the epijugal bone. Its form and 

 position are shown in Plate y, fig. 1, d. 



The pterygoid bones and their position have already been 

 described by the writer. The palatine bones are much smaller 

 than the pterygoids. They are vertical, curved plates, outside, 

 and in front of the pterygoids, and uniting firmly with the 

 maxillaries. The vomers join the pterygoids in front, where 

 they appear as thin bones, closely applied to each other. 



*This Journal, vol. xxxvi, p. 471, December, 1888; vol. xxxvii, p. 334, April, 

 1889; vol. xxxviii, p. 173, August, 1880, p. 501, December, 1889; and vol. xxxix, 

 p. 81,' January, 1890. 



