MONOCLONIUS SPHENOCERUS. 87 



material from the same region. Fig. 90 shows side, front, and top views of the type of Mono- 

 clonius recurvicornis Cope. 



The similarity in form exhibited by the supraorbital horn cores in Ceratops montanus and 

 Monoclonius recurvicornis will be apparent to all, while the dissimilarity between them and 

 the same element in the cotype of Monoclonius crassus, the type species of the genus, is even 

 more striking. This, together with the accessory horn in front of the larger horn shown in the 

 type of M. recurvicornis, along with several other characters to be noticed later, would seem 

 to warrant the removal of the last-mentioned species from the genus Monoclonius and the 

 placing of it in the genus Ceratops, with which it agrees very well in so far as the characters 

 of this latter genus are at present known. These questions will be discussed in greater detail 

 in that chapter devoted to a revision of the genera and species. 



Principal measurements of the type. 



Mm. 



Transverse diameter of occipital condyle 76 



Vertical diameter of occipital condyle 70 



Height of right frontal horn 166 



Antero-posterior diameter of same at base 117 



Transverse diameter of same at base 99 



Transverse diameter of nasal horn at base 112 



Transverse diameter of nasal horn near summit 35 



Antero-posterior diameter of nasal horn near summit 58 



Transverse diameter of nasals at base of nasal horn 133 



Transverse diameter of nasals at distal extremity of part preserved 49 



Height of nasal horn above superior border of nasals — 175 



Monoclonius sphenocertjs Cope. 1889. 



Type (No. 39S9, American Museum of Natural History) consists of portion of premaxillary nasals and nasai horn. 



Original description pp. 716-717, vol. 23, Am. Naturalist, 1889. 

 Cope, E. D., Am. Naturalist, vol. 26, 1892, p. 757. 

 Lambe, L. M., Contr. Canadian Pal., vol. 3 (quarto), pt. 2, 1902, p. 68. 

 Nopcsa, F. Baron, Foldtani Kozlony, Budapest, 1901, vol. 31, p. 270. 

 Osborn, H. F., (Agathaumas) Science, new series, vol. 7, 1893, pp. 842, 844; Contr. Canadian Pal., vol. 3 (quarto) , pt. 2, 1902, 



pp. 14,20. 

 The type (No. 3989, American Museum of Natural History) of the present species consists 

 of the nasals and left premaxillary, representing a very large individual, found by Charles H. 

 Sternberg on the Missouri River near Cow Island, Montana, in 1876. No definite horizon is 

 given. Cope's original description was as follows: 



Monoclonius sphenocerus Cope, represented by numerous parts of the skeleton, including parts of the skull, which were 

 found by Charles H. Sternberg, on the Missouri River, near Cow Island, in 1876. The end of the muzzle is preserved, and 

 presents characters which show that the species is quite different from the one last described. The nasal bones are greatly 

 1 produced to form a slender, compressed, decurved apex, with a prolongation of the inferior median ethmoid septum. The 

 superior face is round in the transverse section, and is rugose. At a long distance behind the apex the nasal born rises. It 

 is compressed and vertical in direction, and was not less than 250 mm. in length, but the apex I have not yet found in the 

 packages. Supraorbital horns unknown. The nasal bones are narrower at the base of the horn than in the recurvicornis, 

 and the horn is of different form. The anterior border converges regularly to the posterior, and its anterior edge is acute 

 for the distal half. Length of nasals in front of horn, 255 mm. ; transverse diameter of nasals below at base of horns, 70 mm.; 

 diameters of base of horn, antero-posterior, 160 mm.; transverse, 60 mm. 



The Monoclonius sphenocerus is an animal of large size, exceeding the rhinoceros in height, and the nasal horn is the 

 most formidable weapon I have observed in a reptile. 



From the above description and the figures which accompanied it it will be seen that the 

 species must rest on the nasals and premaxillary mentioned above. The numerous portions 

 of the skeleton mentioned by Cope are now no longer determinable, not having been distinctively 

 marked by Cope, and I shall base my description and diagnosis of the species on the nasals 

 and premaxillary alone. 



The nasals are massive and indicate an animal ofdarge size. The sutures for the frontals 

 and premaxillaries are distinct and indicate that the individual was scarcely adult. Superiorly 

 and about midway between their anterior and posterior extremities the nasals support a large 



