OF THE MESOZOIC MAMMALIA. 
221 
The accompanying figures represent two views of the crown of a small tooth 
from the supposed Rhaetic Bone Bed near Hohenheim, not far from Stuttgart. It 
has been preserved for many years in the Mineralogical Cabinet of the Akademie 
Hohenheim, and was forwarded to the writer by Prof Dr. F. Nies, through the 
kindness of Dr. Baiu'. It has not been heretofore described. It con- 
sists of a low quadrate crown supporting four smooth, conic tubercles 
“ at the corners, which are very slightly worn ; the fangs are wanting ; 
the history of the specimen is somewhat uncertain. If it is actually 
^ from the Rhaetic Beds, it probably represents a premolar of Trigly- 
phus or one of the allied Tritylodonts. 
POLYMASTODONTID^, Cope, 1884. 
Fig. 14. Pre- 
molar of Trigly- 
phus (?) a, Upper 
view ; h, side view. 
f natural size. embraces the single genus Polymastodon (Cope) which 
has several known species. The dentition is i ^ c ^ pm f m |. The family char- 
acter as stated by Professor Cope, is that the fourth premolars are more simple than 
the first true molars. This is a rather uncertain distinction from Tritylodon in which 
the crowns of the premolars are not known. The dentition is much reduced. As 
there are no worn grooves between "the rows of tubercles, the upper tubercles 
simply oppose the lower, without alternating with them. No other family 
character is at present to be found, although it seems as clear that Polymastodon 
and Tritylodon belong to separate families as it is that they belong to the same 
sub-order. 
The incisors resemble those of the Plagiaidacidoe. The molars have three rows 
of numerous tubercles in the maxilla, and two rows in the mandible ; these tubercles 
are flattened into a tesselated pattern, lacking the longitudinal grooves. Various por- 
tions of the skeleton are described by Prof Cope. 
Incertje sedis 
STEREOGNATHUS, Charleswortli.t, 1854. 
The lower molars support six cusps arranged in three antero-posterior rows of 
two cusps each. From the tip of each cusp of the middle pair two low ridges diverge, 
forming a V, opening forwards. The lateral pair of cusps have similar ridges ex- 
tending from the median side of the cusp only, towards the centre of the crown 
(fig. 6,5). 
It is doubtful whether Stereognathas belongs to this sub-order, or to the follow- 
ing group. It cannot be placed in any of the foregoing families, since the lower 
molars have three rows of cusps instead of two. At the same time it is even more 
remote from any of the genera of the second group. The nearest likeness to its molar 
pattern is seen in the meniscdessus superior molar. 
* Report Brit. Assoc., 1854, p. 80; also Owen, Quart. Jour. Geol. Soc., 1857, p. 1. 
