96 DEUXIÈME ASSEMBLÉE GÉNÉRALE 
In the Upper Jurassic or Lower Cretaceous mammalia of the Como 
beds we must also admit that no progress has been made to determine 
whether these animals represent both Insectivora and Marsupialia and 
perhaps Monotremata (OsBorx), or whether they are all Marsupialia‘ 
(most English authors). A re-study (Ossorx *?) of the structure of the 
upper molars in the Yale Museum collection strengthens the trituber- 
cular theory (Cope, OsBorx) of the origin of the upper molar teeth. 
Tue UPPER CRETACEOUS FAUNA. 
Here again the relatively modernized (OsBorx*) animals of the Upper 
Cretaceous or Laramie, although carefully revised, still require elucida- 
tion from the rich collection in the Yale University Museum. Mars's 
statement that certain of these animals are Marsupials has been fully 
confirmed by Marrnew, a fact which is striking in the absence of any 
present evidence of Marsupials in the American basal Kocene. 
The present relations of these Laramie animals to those of the Basal 
Eocene (Puerco, Torrejon) has been somewhat strengthened by the re- 
cognition of the ancestors (Meniscoëssus) of Polymastodon, also by the 
supposed recognition of forms related to the Amblypoda, especially to the 
Periptychidæ (OsBorxn); but forms certainly ancestral to the Creodonta 
and other Eocene mammals have not yet been recognized. 
Tue Basaz KOCENE FAUNA. 
In this fauna, commonly known as Puerco, great progress has been 
made. 
Two sharply defined faunal stages have been distinguished (WorTMaN), 
a lower, Puerco proper, and an upper, Torrejon (Marraew “), (Compare 
Fig. 1, 2). The latter is more nearly contemporaneous with the Basal 
Eocene (Cernaysien) of France. Fortunately, in Montana, a new locality 
has been discovered for these very archaie mammals in the Fort Union 
beds (Douézass”, Farr) which promises to extend our knowledge of this 
fauna. 
? AMEGHINO, FI. Los Diprotodontes del orden de los Plagiaulacideos. An. Mus. 
Nac., Buenos-Aires, t. ix, 1903, pp. 81-192. 
? Palæontological Evidence for the Original Tritubercular Theory. Amer. Jour. 
Sci, Vol. xvii, Aprit, 1904, pp. 321-328. 
® Fossil Mammals of the Upper Cretaceous. Bull. Amer. Mus. Nat. Hist., Vol. v, 
1893, pp. 5311, 330. 
# MarTHEw. À Revision of the Puerco Fauna. Bull. Amer. Mus. Nat., Vol. ix, 
1897, pp. 260-261. 
5 A Cretaceous and Lower Tertiary Section in South Central Montana. Proc. 
Amer. Phil. Soc., Vol. xli, 1902, No. 170, pp. 207-224. 
