624 The American Naturalist. [July, 
the subfamily, Telmatotherium should, therefore, hold an 
intermediate position between Palaeosyops and Diplacodon.” 
It is interesting to note that these newly discovered skulls of 
Telmatotherium are merely greatly enlarged ones of the P. me- 
garhinus type (see fig. 2), and that other skulls in the collection 
of the American Museum show the transition stages between 
the generalized form of P. megarhinus and that of the Telma- 
totherium type from the uppermost part of the transition beds 
already, referred to. 7 
_In the Bridger proper or the area of southwestern Wyoming, 
just north of the Uinta Mountains, occur at least three well 
defined types of skulls of Palaeosyops, namely, that of P 
paludosus, with frontal region strongly convex and occipital 
portion broad and heavy (see fig. 3). The character of the 
teeth in this species is very primitive, but it has a specialized 
form of skull. 
2. The type which Marsh called Limnohyops. I recognized 
this as a good genus in my memoir, but I now believe that it 
should be included in Palaeosyops. In P. (Limnohyops) lati- 
cens the skull is saddle-shaped like that of Titanotherium, and 
I called particular attention to this fact in the paper already 
quoted (see fig. 1). 
3. The P. megarhinus type of skull is the most primitive of 
all, there is hardly any depression on the dorsal surface, and 
the sagittal crest is well defined. The teeth are tending towards 
those of Telmatotherium, as they have broad and angular 
crescents, with a reduction of the intermediate tubercles (see 
fig. 2). I wish to emphasize particularly that in the Bridger 
proper, the saddle-shaped type of skull was established, and 
contemporaneous with it was the much more primitive skull 
of P. megarhinus. I accordingly did not suspect that the lat- 
ter was in the direct line leading to Diplacodon. However, 
the discovery of the skull,of this species south of the Uinta 
Mountains and its relationship to Telmatotherium, has made 
necessary some changes in the phylogeny of the species of 
Palaeosyops, and I now find that there were two well defined 
lines of Palaeosyops tending in the characters of their skulls 
and dentition towards Titanotherium, and that these two 
