; 
4 
3 
3 
a 
a 
E 
À 
: 

1891.] Cretaceous Mammatia. 609 
E. INCERT SEDIS. 
8. STAGODONTIDÆ. Founded upon reptilian or ic- 
Stagodon nitor thyopsidan teeth. 
Platacodon nanus > 
This reduces the Cretaceous mammals described in these two 
papers to one well-determined order or suborder, two well-deter- 
mined families, and four or five genera, one of which can now be 
well defined (Meniscoéssus), while the remainder are probably 
distinct genera, which we may be able to define by the acquisition 
of more material (Cimolomys, Didelphops, and Cimolestes). There 
is no question that the majority of the remaining generic names 
are synonyms, although it is quite possible that some of the types 
described, such as Oracodon and Pediomys, may be found to rep- 
resent distinct or new genera. 
It may be said that this analysis has almost eliminated the 
work of the author. This unfortunately is what is necessary if 
we would render this contribution of any permanent value in 
paleontology. We are, then, left with a series of teeth which rep- 
resent rare skill on the part of the collector, and are figured with 
remarkable accuracy by the draughtsman. A few points of 
interest upon the collection asa whole may be mentioned : 
The Multituberculata. The preponderance of teeth belonging 
to members of this order would appear to indicate that it flour- 
ished during this period. Cimolomys represents a connecting 
form between Plagiaulax, Upper Jurassic, with three premolars,. 
and Ptilodus of the lowest Eocene with two. The smallest 
species, C. formosus, apparently has as many grooves upon the- 
fourth premolar as we observe in Ptilodus, and the first lower molar 
has even more tubercles than we find in the corresponding tooth 
of the Lower Eocene genus. These grooves and tubercles mark 
the stages of development, and it would appear that Cimolomys. 
is not far removed from Ptilodus ; this relation can only be deter- 
mined by the discovery of additional teeth; we may find that 
Cimolomys has a large third premolar. 
Another interesting fact is that Meniscoëssus does not belong 
with the Plagiaulacidæ, as has been generally suppa hitherto,'* 
16 Cope, Osborn, Lydekker. 
