> 

334 B. N. A. BOUNDARY COMMISSION. 
referred to 7. vagans, though closely resembling that species, is not large enough 
for final deterimination. The Cionodon, though based on incomplete remains, is 
quite sufficient for paleontological purposes. WelYe. ‘i 
In conclusion, it may be stated that there are present two genera in this 
_ collection which are diagnostic of the Fort Union epoch, but no species certainly 
so, though two species are probably identical with species of that epoch; also, 
that the presence of Dinosauria refers the fauna to the Mesozoic series; and that 
there is no satisfactory evidence of the co-existence of these reptiles with Tertiary 
forms; that the species referred to Plastomenus constitute an indication of affinity 
with corresponding Eocene forms. "The presence of garfishes of the genus Clastes in 
this formation is as yet peculiar to this and the Judith River localities, As these 
gars have not heretofore been found in North America below the Eocene, they 
constitute the first case of apparent commingling of Tertiary and Cretaceous 
animal life yet clearly determined. Yet the evidence is far from being as weighty 
in indication of Tertiary relations as is the presence of the saurians in question as 
evidence of Mesozoic character ; for the gars, though now living, are an ancient type, 
their allies having swarmed in the Jurassic seas, and it is therefore altogether rea- 
sonable that they should be found in fresh water deposits of Cretaceous and Tertiary 
age. The rarity of the localities of the former deposit accounts for the late date of 
their discovery there. 
CIONODON, Cope. 
Bull. US. Geol. Survey Terrs., No. 2, p. 21. 
Char, gen.—Established primarily on a portion of the right maxillary bone, with 
numerous teeth in place, of the C. arctatus, Cope, a species discovered in the Fort Union 
beds of Colorado. The following generic characters are derived from the typical 
specimen of this species. The posterior portion exhibits a suture, probably for union 
with the palatine bone, while the rest of the interior margin is free. It is removed 
some distance from the tooth line in consequence of the horizontal expanse of the 
bone, while the outer face is vertical. 
The teeth are rod-like ; the upper portion subcylindric in section, with the inner 
face flattened from apex to base, while the lower half is flattened by an abrupt exca- 
vation to the middle, for the accommodation of the crown of the successional tooth. 
The inner face of the tooth, from apex to base, is shielded by a plate of enamel, 
which is somewhat elevated at the margins, and supports a keel in the middle, thus 
giving rise to two shallow longitudinal troughs. The remainder of the tooth is 
covered with a layer of some dense substance, possibly cementum, which overlaps 
the vanishing margins of the enamel. The outer inferior excavation of the shaft 
presents a median longitudinal groove, to accommodate the keel of the closely-ap- 
pressed crown of: the successional tooth. The apex of the tooth being 
obtusely wedge-shaped, the functional tooth is pushed forward and _ trans- 
versely, toward the inner side of the jaw. The tooth slides downward in a 
closely-fitting vertical groove of the outer alveolar wall. The inner wall is 
oblique, its section forming with that of the outer a V; it is furrowed 

