118 THE CERATOPSIA. 



at o 2 in the same plate, half a mile to the southwest, on the crest of the ridge that 

 forms the watershed between this and the next tributary to the south, emptying into Buck 

 Creek from the west, there is another "blow-out" of about equal area in a similar sandstone 

 layer, but at a horizon estimated as 80 feet higher, from which were obtained bones of 

 Trachodon and numerous teeth of Laramie mammals, fishes, and reptiles, including repre- 

 sentatives of both the Ceratopsidae and Trachodontidse. 



ORIGINAL DESCRIPTION. 



In his original description Marsh placed the present species in the genus Ceratops. His 

 description as given in the American Journal of Science for April, 1889 (3d ser., vol. 37, pp. 

 334-335), was as follows: 



The strange reptile described by the writer as Ceratops montanus proves to have been only a subordinate member of the 

 family. Other remains received more recently indicate forms much larger and more grotesque in appearance. They also 

 afford considerable information in regard to the structure of these animals, showing them to be true Stegosauria, but with the 

 skull and dermal armor strangely modified and specialized just before the group became extinct. 



■ The vertebrae and the bones of the limbs and of the feet are so much like the corresponding parts of the typical Stego- 

 saurus from the Jurassic that it would be difficult to separate the two when in fragmentary condition, as are most of those 

 from the later formation. The latter forms, however, are of much larger size, and nearly all the bones have a peculiar 

 rugosity much less marked in the Jurassic species. In the form here described this feature is very conspicuous and marks 

 almost every known part of the skeleton. 



In the type specimen of the present species, the posterior horn cores are much larger than these appendages in any other 

 known animal living or extinct. One of them measures at the base no less than twenty-seven inches, and about sixteen 

 inches around, halfway to the summit. Its total height was about two feet. In general form these horn cores resemble 

 those of Ceratops montanus, but the anterior margin is more compressed, showing indications of a ridge. 



The top of the skull in the region of the horn cores is thick and massive and strongly rugose. 



This skull as a whole must have had at least fifty times the weight of the skull of the largest Sauropoda known, and tins- 

 fact will give some idea of the appearance of this reptile when alive. 



As previously stated, the posterior pair of horn cores of this family are hollow at the base, and in form and surface 

 markings are precisely like those of the Bovidse. The resemblance is so close that, when detached from the. skull, they can 

 not be distinguished by any anatomical character. This accurate repetition, in later and still existing forms, of the highly 

 specialized weapons of an extinct group of another class is a fact of much interest. 



The present .specimen is from the Laramie formation of W3 r oming, but fragmentary remains which may be referred 

 provisionally to the same species have been found in Colorado. 



As is now well known, and as was soon after recognized by Professor Marsh, the Ceratop- 

 sidse are not nearly so closely related to the Stegosauria as he then supposed. There are many 

 important structural differences, not only in the skull but in almost every portion of the 

 skeleton. 



CERATOPS HORRIDTJS MADE THE TYPE OF THE NEW GENUS TRICERATOPS. 



Shortly after this Professor Marsh recognized the generic distinction existing between 

 Ceratops montanus and C. horridus, and made the latter the type of a new genus, Triceratops. 

 His remarks in this connection, as published in the American Journal of Science, August, 1889 

 (vol. 38, pp. 173-174), were as follows: 



The animal described by the writer as Ceratops Jiorridus possesses some remarkable characters not before known 

 in the Dinosauria. In addition to the pair of massive horn cores on the top of the skull, there is a third horn core on the 

 nose. This is median, as in the rhinoceros, and is placed on the end of the nasals, which are firmly coossified to support it. 



The edentulous premaxillaries are compressed anteriorly and are strongly coossified with each other and with a third 

 bone in front, which corresponds to the predentary bone below, the whole forming a projecting beak, like that of a tortoise. 

 Over all there was, evidently, a huge horny covering, like the beak of a bird. 



The bone in front of the premaxillaries has apparently not before been observed in any vertebrate, and ma}' be called the 

 rostral bone (os rostrale). It is analogous to the prenasal ossification of the pig and of the Dinocerata. 



Other portions of the skull show features not before seen in the Dinosauria. There is a huge occipital crest, extending 

 backward and outward. In the present specimen this is bent downward at the sides, like the back part of a helmet, thus 

 affording in life strong protection to the neck. 



The lower jaws are massive and were united in front by a strong predentary bone. This is pointed anteriorly and its 

 surface marked by vascular impressions, showing that it was covered with horn and fitted to meet the beak above. 



The skull appears to have been at least two meters in length, aside from the horny beak. Ii represents a genus distinct 

 from the type of the family, which may be called Triceratops. This interesting specimen, which has recently been received at 

 the Yale Museum, was discovered by Mr. Charles A. Guernsey and Mr. E. B. Wilson in the Laramie formation of Wyoming. 



