a ee ee ee a ee ea ae ee en ee ee ee aR, aN eee ME pone 


1891.] Cretaceous Mammalia. 603 
This collection of molars demonstrates that Meniscoéssus, like 
Stereognathus, belongs to a family in which the tubercles are 
crescentoid and arranged in two rows in the upper molars and 
three rows in the lower_molars. This is admirably shown in the 
author’s own figures as rearranged in Figure 5. a, the type of 
Dipriodon robustus, is seen to fit upon 4, the type of Tripriodon 
celatus; d and c belong to old individuals, but the worn cusps 
and valleys coincide ; they are respectively the author’s types of 
Dipriodon lunatus and a molar referred to Selenacodon fragilis, as 
it agrees exactly with the type except in point of -wear. 
The lower incisor, type 
of Zripriodon caperatus, 
corresponds in size with 
these molars; the two 
smaller incisors, referred 
to T. cælatus and Selena- 
codon brevis, have the 
same shape and grooved 
sides. (1) When these 
incisors are placed side 
by side, as in Fig. 5, 
with the upper incisors 
FIG. 6.— a, upper incisor of Halodon sculptus ; referred by the author 
4, lower incisor of Tripriodon caperatus, type ; 
upper incisor of Halodon serratus ; d, lower alioi to Halodon sculptus and 
E yria i brevis. After Marsh. Halodon serratus, we 
observe that the`longitudinal and transverse diameters of 
the crowns and fangs coincide exactly in measurement, ren- 
dering it highly probable that they belong to » 
the same species. (2) The question is, Do 
these teeth belong to Halodon or Menis- 
coéssus? We observe that the lower incisor 
associated with Halodon formosus (Pl. vii., 
Figs. 32-35) has the enamel confined to a 
band, as in Ptilodus and Neoplagiaulax. Itis Fic. 7.—Tooth de- 
ok ac LES 
smooth. It is, therefore, probable that all these aa of of Diprioton 
obustus. 


Striated, completely enameled incisors belong ”” 
to Meniscoéssus. (3) When, moreover, it is seen that these 
