Measurements. 



M. 

 Length from apex of nasals to occipital condyles (axial) 



(thirty-four inches) 684 



" from occipital condyles to femoris of palate 376 



" " occipital condyles to end of palatine lamina 



pteryzoidea 270 



" of four last molars : . . .242 



" three " 195 



" last molar 068 



Width of palate at nareal notch 116 



This remarkahle mammal shows several points of approximation to 

 the Rhinocerotidos as compared with others of the same group. Its 

 physiognomy is also a remarkable parallel of the Loxolophodon comutus, 

 Cope, of the Eocene, which animal it did not equal in size, although it 

 exceeds the largest living Rhinoceros. Two specimens of crania seen. 

 Megaceratops acer, sp. nov. 

 Another huge mammal, second only to the preceding in size, but more 

 formidably armed, was its cotemporary. It is represented in my collec- 

 tion chiefly by a single cranium without under jaw. Top of head fiat, 

 forming a narrow plane between the temporal fossae ; latter produced 

 backwards. Orbit not enclosed behind, an overhanging superciliary 

 ridge. Nasal exceedingly short and massive, each supporting a large 

 acute horn-core, which is connected with its fellow by a ridge at the 

 base, and diverges widely from it with an outward and forward curve to 

 the acutely compressed apex. Each horn-core about one foot long. The 

 top of the head is plane between the orbits, and little concave fore and 

 aft. The zygoma is very deep, and the postglenoid process well de- 

 veloped. End of nasal bones short and thick, but flat. 



Measurements. 



M. 



Length cranium (thirty-five inches) 895 



" from posterior rim temporal fossa to middle of 



superciliary ridge 345 



Width front between eyebrows 210 



Length horn-core on inner side (10 in.) 254 



The elemental origin of the horn-cores is probably different in this 

 genus from that which exists in Miobasileus. 



This was a truly formidable beast, exhibiting a position of the -horns 

 strangely the reverse of that seen during the present period. Its size 

 exceeded that o£ the Indian Rhinocerus. 



Megaceratops helocertjs, sp. nov. 

 Founded on a cranium of an animal of larger size than the last, with • 

 nearly complete maxillary dentition. There is a prominent horizontal 

 superciliary ridge without horns, and two short obtuse horn-cores on the 



