1889.] Geology and Palceontology . 717 
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. 
It may be that the two species last described belong to Agathaumus, 
as the cranial characters of that genus are not known. 
Monoclonius crassus Cope, 1. c. Parts of two individuals found 
Monoclonius fissus Cope, sp. nov. 
Founded on a squamosal bone of an individual of much smaller 
size than those above described. The suture with the parietals is 
relatively shorter than in the M. crassus, occupying only the distal third 
of the margin. The plate anterior to the transverse suture for the 
quadrate is more nearly in one plane, is wider in relation to its length, 
and has a squamosal sutural surface, and a transverse groove not seen 
in the M. crassus. The excavation posterior to the process which joins 
the quadrate is deeper. External border mostly lost. Total length 180 
mm. ; length in front of quadrate suture 50 mm. ; width in front of 
do. 87 mm. ; width at postquadrate concavity, 62 mm. 
Bones of Agathaumidas much reduced. 
Fig. I . Parietal bone of Monoclonius crassus one-eighth natural size. 
Fig. 2. Nasal and part of ? ethmoid bones of Monoclonius spheno- 
cerus ; a side view; b from above; two-ninths natural size. 
Fig. 3. Part of frontal bone of Monoclonius recurvicornis with 
supraorbital horn, and nasals with horn ; profile, two-ninths natural size. 
Fig. 4. Front view of supraorbital and nasal horns and adjacent 
bones of Monoclonius recurvinostris ; two-ninths natural size. 
Fig. 5. Part of nasal bones of do. with part of median horn, from 
