1088 The American Naturalist. [ December, 
new and several little-known species of Telmatotherium from most ex- 
cellent material secured by Mr. O. A. Peterson, chief y from the Uinta 
beds of Utah, has considered Te/matotherium cornutum as directly an- 
cestral to Diplacodon. He says, on page 72 of the article just cited, 
“ Telmatotherium cornutum is in one of the direct ancestral lines leading 
to the Titanotheres.” In a recent paper by Earle,’ he suggests a poly- 
phyletic origin of the genus Titanotherium as had already been inti- 
mated by Osborn. Earle, in this last paper, points out very clearly 
two distinct lines of species of Paleosyops and Telmatotherium which he 
considers persistent series and probable ancestors of Diplacodon and 
Titanotherium. 
After studying Diplacodon in connection with what is already known 
of Telmatotherium cornutum, it seems impossible to accept Osborn’s 
views in regard to the ancestral relations of the latter to any of the 
later Titanotheres. The character of the dentition and the presence of 
incipient frontonasal horns would, at first, seem to lead to such a con- 
clusion, but a closer study of the material seems to indicate that this is 
simply a case of parallelism, since, in nearly every other character, T. 
coruntum exhibits features not at all in accordance with what we 
should expect to find in the immediate ancestors of the Titanotheres ; 
as examples of such features, I would point out, 1, The long, narrow 
nasals; 2, Convex dorsal aspect of skull; 3, Position of posterior nares 
which, according to Osborn, are in this species moved backward until 
they now open far back behind the last molar ; 4, The slender and almost 
parallel zygomata; 5, The presence of an infraorbital shelf; 6, The 
reduction in the number of inferior incisors to two on either side, while 
Diplacodon still retains three well-developed ones on a side; and 
Marsh’ has shown that some of the later forms from near the base of 
the White River beds still retain three on a side, although quite rudi- 
mentary as would be expected. These are all characters of import- 
ance, and the position of the posterior nares and reduction of the num- 
ber of incisors in T. cornutum would seem to absolutely prohibit the 
placing of that species in the direct line leading to the genera Diplaco- 
don and Titanotherium. 
There seems to be little doubt that Diplacodon had an earlier ances- 
try than has heretofore been referred to it, for remains of it are found 
in the T. cornutum beds of Osborn associated with remains of that 
On a Supposed Case of Parallelism in the Genus Paleosyops. Am. Nat., 
July, 1895, pp. 612-626. 
‘Notice of New Tertiary Mammals. Am. Journ. Sci., June, 1890, pp. 523- 
525. 
