24 Bulletin American Museum of Natural History. [Vol. XXXIV, 
more massive but less distinct posterior accessory cusps, hypoconid of m; 
larger and more massive and more central in position, filling up most of 
the “basin” of the heel, my broader and with shorter heel. Jaw a little 
longer than in D. protenus but considerably deeper. 
Nos. 14749-52 upper and lower jaws from the Lost Cabin horizon in the 
7 
NN NY \ Uy, 
WOK 3 ) 
: Ss ie ae 
Fig. 17. Didymictis altidens, lower jaw, outer view, with crown view of teeth, natural 
size. No. 14749, Lost Cabin beds, Wind River Basin. 
Wind River Basin, and 4792-8 fragments of jaws and teeth probably from 
the same level, are referable to this species. The specimens from the 
Lysite horizon are referable to D. protenus. In the Big Horn Basin a speci- 
men has been described by Prof. Scott as D. altidens.1 Information as to 
the exact locality of this specimen was kindly supplied by Professor Scott. 
It is from the westward extension of Tatman Mountain in the Big Horn 
Basin and was associated with Lambdotherium. Its horizon is thus fixed as 
Lost Cabin. 
In No. 14750 the palate is very well preserved, and in No. 14749 the 
lower jaw. 
I refer to this species No. 14781, a specimen from the Lost Cabin beds 
in the Wind River Basin, consisting of the tibize, fibule and complete hind 
feet, with a few other fragments. The reference is based upon agreement 
in construction of the foot bones with the corresponding parts in associated 
specimens of the smaller species. 
1 Scorr, 1888, Jour. Acad. Nat. Sci. Phila., Vol. LX, p. 169. 
