THE CERATOPSIA. 



for publication at the meeting of the society on March 18, 1856. In this paper Doctor Leidy 

 established four new genera and species of dinosaurs from the, remains collected by Doctor 

 Hayden and gave brief descriptions, without figures, of each. In the closing paragraph he 

 provisionally correlated the horizon from which the remains had come with the Wealden of 

 Europe. 



Three years later a Doctor Leidy described this- material more fully and accompanied 

 his descriptions with most excellent figures. In figs. 1-20, PI. 9, of the publication just cited 

 there are shown a number of teeth of various patterns, all of which were referred by Doctor 

 Leidy to Trachodon mirahilis. Of all the teeth represented in figs. 1-20, that 

 depicted in figs. 1-3 formed the basis of his original description of the above- 

 mentioned genus and species, as will readily appear from an examination of 

 the text. This tooth may then be fairly considered as the type of Trachodon 

 mirahilis, while the double-rooted tooth shown in figs. 18-20, which, as we 

 now know, pertains to a dinosaur belonging to a genus and species distinct 

 from that of which the single-rooted tooth shown in figs. 1-3 was made the 

 type, must be referred not only to a distinct genus and 

 species, but to another family and suborder. Later dis- 

 coveries have shown beyond a doubt that the tooth 

 delineated in figs. 18-20 pertained to a species of horned 

 dinosaur of the family Ceratopsidaa, a family which is unique 

 among all known reptiles, both living and extinct, in being 

 provided with teeth having forked roots and with a pair of 

 transversely placed supraorbital horns on the skull. It is 

 thus clearly evident that among this meager and fragmentary 

 collection secured by Doctor Hayden there were remains of 

 the horned dinosaurs, or Ceratopsia, though Doctor Leidy 

 failed to distinguish them from the Trachodontidae, as he might easily do 

 considering the nature of the material at his command. Leidy's figures of the lateral views of 

 these teeth are reproduced here (figs. 1 and 2) for comparison. 



Fig. 1.— Lateral view 

 of type of Tracho- 

 don mirabili s 

 Leidy. Natural 

 size. After Leidv. 



Fig. 2.— Lateral view 

 of tooth of Mono- 

 clonius, a horned 

 dinosaur discov- 

 ered by Doctor 

 Hayden. Twice 

 natural size. After 

 Leidy. 



DISCOVERY OF TYPE OF AGATIIALTMAS SYLVESTRIS BY PROF. F. B. MEEK. 



Seventeen years after Doctor Hayden's explorations in the Judith River country, or in 

 1872, Prof. F. B. Meek discovered a portion of the skeleton of a member of the Ceratopsia near 

 Black Buttes station on the Union Pacific Railroad, not far from the Hallville coal mines, 52 

 miles east of Green River. The locality was visited the same year by Prof. E. D. Cope, who 

 succeeded in recovering "sixteen vertebrae, including a complete sacrum, caudals, and dorsals, 

 both ilia and other pelvic bones, bones of the limbs, ribs, etc." These were described by Cope ° 

 and constitute the type of the genus and species Agaihaumas sylvestris. In his original descrip- 

 tion he says some limb bones were recovered. In a later publication, however, he says, "There 

 are no bones certainly referable to the limb bones." This material is at present preserved in 

 the collections of the American Museum of Natural History (No. 4000) and consisted originally, 

 according to Cope, of "sixteen vertebrae, including a perfect sacrum, with dorsals and caudals; 

 both ilia and other pelvic bones, those of one side nearly perfect; some bones of the limbs, 

 ribs, and other parts not determined." Of this material there has been accessible to me only 

 the right ilium and a mere fragment of the anterior extremity of the left, one rib nearly com- 

 plete, and a proximal portion of a second. The sacrum and the dorsals, caudals, and sacro- 

 caudals figured by Cope are also available, although some of the neural arches and spines of 

 the dorsals are missing. 



a Extinct Vertebrata from the Judith River and Great Lignite formations of Nebraska: Trans. Am. Philos.Soc, 2d ser., vol. 11, 1860, pp. 

 139-154. 



b Proc. Am. Philos. Soc, vol. 12, pp. 481-483. 



c Monographs U. S. Geol. and Geog. Surv. Terr., vol. 2, pp. 55-56. 



