222 O. C. Marsh—New Tertiary Mammals. 
This interesting fossil was found, last autumn, near Henry’s 
Fork, Wyoming, by Mr. G. M. Keasbey. 
Entomacodon angustidens, sp. nov. 
A very small insectivore, which appears to belong to the 
enus Hntomacodon, left its remains in the Green River Tertiary 
deposits, and our collections contain a left lower jaw, with the 
last premolar and the two following molars in good preserva- 
tion. ‘The molars agree essentially in the composition of their 
crowns with those of #. minutus, but the three anterior cusps 
are nearer together, and the one in front is nearly as high as the 
others. The specimen indicates, also, a smaller animal than the 
type of that species. The jaw is much compressed, and the teeth 
are very narrow. The last premolar resembles the adjoiming 
molar, but has the anterior cusp rudimentary. 
Measurements. 
Space occupied by last four lower teeth,..........-.+++5 55 9 
Antero-posterior diameter of last lower premolar,.......- 1°6 
Antero-posterior diameter of penultimate lower molar,....1°7 
APADSVOISE GIAWEEEE wires syne bape © kmh 0 hg ore ie 6 6 me ¥ 
Depth of jaw below last lower molar,...........22.0+0+5 2°5 
This specimen was found by Mr. J. J. DuBois, at Grizzly 
Buttes, Wyoming, in September of last year. 
Triacodon grandis, sp. nov. 
The genus Zriacodon was established, by the writer, on @ 
single lower premolar, which differed widely from any corres 
ponding tooth then known. The species thus represented was 
called 7. fallax, and its possible marsupial affinities were sug 
gested.* The researches of the Yale party during the past 
mal, but much still remains to be ascertained. A portion of & 
* This Journal, vol. ii, p. 123, August, 1871. 
