1090 The American Naturalist. [December, 
between 2 and 3, and 3 and 4, but there would seem to be little doubt 
that the genus Titanotherium has been evolved from the earlier 
Bridger forms of Paleosyops through P. laticeps and the intermediate 
forms Telmatotherium vallidens from the Washakie and Diplacodon 
from the Uinta. Vertebrate paleontology rarely shows a more com- 
plete series of the stages of development than are to be seen here. 
I wish here to thank Prof. Scott for his kindness in placing at my 
disposal the material upon which this paper is based. My thanks are 
also due to the various undergraduate and graduate members of the 
expedition of 1895, whose generosity alone made it possible. 
EXPLANATION OF PLATES. 
Plate XX XVIII. 
Fig. 1.—Side view of front of skull of Diplacodon emarginatus. 
Fig. 2.—Dorsal view of same. 
Fig. 3.—Front view of same. 
Fig. 4.— Crown view of lower jaw of same. 
Fig. 5.—Crown view of inf. premolars of Paleosyops laticeps. 
Fig. 6—Crown view of inf. premolars of Titanotherium sp. 
Plate XX XIX. All figures } natural size. 
Fig. 1.—Side view of Paleosyops laticeps (after Earle). 
Fig. 2.—Side view of Telmatotherium vallidens (after Osborne). 
Fig. 3.—Side view of Diplacodon emarginatus. 
Fig. 4.—Side view of Titanotherium varians (after Marsh). 
—J. B. HATCHER. 
Princeton, N. J., Oct. 29, 1895. 
POSTSORIPT. 
The genus Telmatotherium as it now stands should be divided, since 
it embraces at least three quite distinct forms. The type of T. vallidens 
should be removed from that genus and made the type of a new genus. 
This new genus may be called Manteoceras as suggested by Wortman 
from the field, it would be distinguished from Telmatotherium by the 
absence of the infraorbital shelf, the stronger and more expanded 
zygomata and the concave superior aspect of skull and incipient fronto- 
nasal horns. The type of T. cornutum should also be made the type of 
a new genus which may be called Dolichorhinus, it would be distin- 
guished from Manteoceras and Telmatotherium by the reduced number 
of inferior incisors, presence of incipient horns, presence of infraorbital 
shelf and position of posterior nares.—J. B. HATCHER. 
