20 
MUSEUM BULLETIN NO. 12. 
known species of the genus, when discovered will most probably 
prove to be of small size. The characters of Anchiceratops, 
as at present known, seem to assign it to a position between 
Eoceratops and Triceratops, an evolutionary stage in accord 
with the position of the Edmonton formation intermediate 
to the earlier Belly River beds and the later Lance formation. 
The members of the second group (Centrosaurus, etc.) 
have small brow-horns, a large nose-horn, and parietals expanded 
behind small squamosals (Plate VI). While in this group the 
nasal horn is large, its shape is distinctive in the three known 
genera composing the group. Thus, in Centrosaurus the nasal 
horn curves forward, in Styracosaurus it is straight and points 
upward, in Brachyceratops it curves backward. 
In the two genera forming the third group there is a striking 
increase in the size of the brow-horns, a decrease in size in the 
nasal horn, and a development of very long, narrow squamosals 
(Plate VII). 
The above three groups or subfamilies of the homed din- 
osaurs, which may be named the Centrosaurinse, the Eocera- 
topsinse and the Chasmosaurince from the most primitive mem- 
ber of each group respectively, occur in the Belly River formation 
and later Cretaceous as follows: — 
Ancestral Type or Types 
(undiscovered) 
Horizon 
Centrosaurus 
group 
Eoceratops 
group 
Chasmosaurus 
group 
Belly River 
(Judith 
River) 
Centrosaurus 
Styracosaurus 
Brachyceratops 
Eoceratops 
Chasmosaurus 
Laramie 
(Lance Creek 
beds) 
Triceratops 
Torosaurus 
