334

B. N. A. BOUNDARY COMMISSION.

referred to T. vagans , though closet)’ resembling that species, is not large enoughfor final deterimination. The Cionodon, though based on incomplete remains, isquite sufficient for pala?ontologieal purposes.

In conclusion, it may be stated that there are present two genera in thiscollection which are diagnostic of the Fort Union epoch, but no species certainlyso, though two species are probably identical with species of that epoch ; also,that the presence of JHnosauria refers the fauna to the Mesozoic series; and thatthere is no satisfactory evidence of the co-existence of these reptiles with Tertiaryforms; that the species referred to Plaslomenus constitute an indication of affinitywith corresponding Eocene forms. The presence of garfishes of the genus Vlasies inthis formation is as yet peculiar to this and the Judith ltiver localities. As thesegars have not heretofore been found in North America below the Eocene , theyconstitute the first case of apparent commingling of Tertiary and Cretaceous animal life yet clearly determined. Yet the evidence is far from being as weightyin indication of Tertiary relations as is the presence of the saurians in question asevidence 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 Tertiaryage. The rarity of the localities of the former deposit accounts for the late date oftheir discovery there.

CIONODON, Cope.

Bull. U S. Geol. Survey Terrs., No. 2, p. 21.

Char. gen .—Established primarily on a portion of the right maxillary bone, withnumerous teeth in place, of the C. arctatus , Cope, a species discovered in the Fort Unionbeds of Colorado . The following generic characters are derived from the typicalspecimen of this species. The posterior portion exhibits a suture, probably for unionwith the palatine bone, while the rest of the interior margin is free. It is removedsome distance from the tooth line in consequence of the horizontal expanse of thebone, while the outer face is vertical.

The teeth are rod-like ; the upper portion subeylindric in section, with the innerface 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, thusgiving rise to two shallow longitudinal troughs.. The remainder of the tooth iscovered with a layer of some dense substance, possibly cementum, which overlapsthe vanishing margins of the enamel. The outer inferior excavation of the shaftpresents a median longitudinal groove, to accommodate the keel of the closely-ap-pressed crown of the successional tooth. The apex of the tooth beingobtusely wedge-shaped, the functional tooth is pushed forward and trans-versely, toward the inner side of the jaw. The tooth slides downward in aclosely-fitting vertical groove of the outer alveolar wall. The inner wall isoblique, its section forming with that of the outer a V ; it is furrowed