20 



The type genera are distributed geographically as follows : — 



Montana. 



Wyoming Laeamie. 



Wyoming, Converse go. 

 Laramie. 



Colorado. 



Monoolonius, Cope. 



Agathaumas, Cope. 



Triceratops, Marsh. 



Polyonax, Cope. 



Dysganua, " 



(Cretaceous No. 6 or 7.) 



Torosaurus, " 





Ceratops, Marsh. 





Sterrholophus, " 





Claorhynchus^, Cope. 









Manospondylus, " 









^ So referred by Cope. Considerod by an iguanodont by Hatcher. 



Ill general the contrast in the Ceratopsia is as follows ; future discovery may alter 

 these prevailing characters : — 



Belly it Judith River Ceratopsia. 

 Of smaller size. 

 Nasal horns ver}' large. 

 Small frontal or supraorbital horns. 

 Widely open supratemporal fossaB. 

 Teeth single {? Monoclonius) and double fanged. 



Laramie Cbr.vi'Opsia, Upper Cretaceous. 

 Of larger size. 



Nasal horns relatively smaller (Triceratops) or even 



vestigial. 

 Greatly developed frontal horns. 



Supratemporal fossse open (Torosaurus) or nearly 

 closed (Triceratops). 



Monoclonius is the first name applied to a Montana ceratopsid. The type species, 

 M. crassHS, Cope, is distinguished by small supraorbital horns, a large supratemporal fossa, 

 and a wide squamoso-parietal crest. 31. rccnrvicornii>. Cope, is distinguished by a forwardly 

 recurved nasal horn ; M. sphenoceras. Cope, by a remarJiably elongate and laterally com- 

 pressed nasal horn ; M. ftssiis, Cope, by a squamosal of peculiar form.* Cerarops montanus, 

 the first of the horned dinosaurs described by Marsh, was found on the Missouri river, 

 Montana, in beds which Mr. Hatcher now considers of Judith River age. It is very 

 similar to if not generically identical with Monoclonius. If this prove to be the case, 

 Cope's suggestion (op. cit. p. 715) that this family should be called Agathaumidix, rather 

 than Ceratopsidrc will deserve consideration. The apparently new species M. dawsoni, 

 M. canadensis, and M. belli, discovered by Mr. Lambe in the Belly River series, add to 

 the variations in the Monoclonius type of skull in the Mid-Cretaceous. 



It will be observed that five of these species are known to possess large nasal and small 

 supraorbital horns. This stage of horn evolution may be contemporaneous with and 

 indeijendeut of that in the southern Laramie dinosaurs in which the nasal horns are 



* For the latest account of these types, which are now preserved in the American M iiseum of Natural History, see 

 Cope, " The Horned Dinosauria of the Laramie", Amer XcU. 1889, p. 715. 



