mabsh.] CLAOSAURID.E. 219 



Ceratopsidae, as first described by the writer, or as a suborder, Ceratop- 

 sia. as later defined by him, will depend upon the interpretation and 

 value of the peculiar characters manifested in its typical forms. 



The main characters which separate the group from other families of 

 the Dinosauria are as follows: 



(1) A rostral bone, forming a sharp, cutting beak. 



(2) The skull surmounted by massive horn cores. 



(3) The expanded parietal crest, with its marginal armature. 

 (i) A piueal foramen ( ?). 



(5) The teeth with two distinct roots. 



(6) The anterior cervical vertebra? coossified with each other. 



(7) The dorsal vertebra? supporting, ou the diapophysis, both the head 

 and tubercle of the rib. 



(8) The lumbar vertebra? wanting. 



The animals of this group were all herbivorous, and their food was 

 probably the soft, succulent vegetation that flourished during the Cre- 

 taceous period. The remains here figured are from the Ceratops beds 

 of the upper Laramie, on the eastern slope of the Eocky Mountains. 



The only known European member of this group is the Struthiosau- 

 rus Bunzel, 1871, apparently identical with Crata?onius Seeley, 1881. 

 It is from the Gosau formation of Austria, and the locality was visited 

 by the writer in 1864. Although only fragments, mostly of the skel- 

 eton and dermal armor, are known, some of these are very character- 

 istic. One specimen figured by Seeley, and regarded as a dermal plate 

 bearing a horn-like spine, is certainly part of the skull. It is very 

 similar in form to some of the horn cores of the smaller species of 

 Ceratops. 



CLAOSAURID-E. 



The next most important family of herbivorous dinosaurs from the 

 Cretaceous of North America is the Claosaurida?, and of tbese the type 

 genus is Claosaurus, described by the writer in 1890, from a specimen 

 found by him in Kansas in 1872. Several fortunate discoveries since 

 made have rendered this g'enus one of the best known of American 

 forms, and hence the principal characters of the skull and skeleton are 

 here given in detail. 



CLAOSAURUS. 

 THE SKULL. 



The skull of Claosaurus is long and narrow, with the facial portion 

 especially produced. The anterior part is only moderately expanded 

 transversely. Seen from the side (PI. LXXII, fig. 1), the skull shows 

 a blnnt, rugose muzzle, formed above by the premaxillary and below by 

 the predentary, both probably covered in life with a thick, corneous 

 integument. 



Behind the upper part of this muzzle is an enormous lateral cavity, 

 which includes the narial orifice, but was evidently occupied in life 

 mainly by a nasal gland, somewhat like that in the existing monitor, 



