512 O. C. Marsh—Jurassic Mammals. 
The affinities of this peculiar species are not easy to deter- 
mine, but it should probably be placed in the Plagiaulacide. 
The number of eee shows that it is distinct from the 
known genera of this gro 
The only specimen Bee indivates an animal about as large 
as a weasel. It was found in the Upper Jurassic deposits of 
yoming. 
Ctenacodon nanus, sp. nov. 
A second and smaller species of this genus is indicated by 
two lower jaws, found separately. One of these, the type spect- 
men, has the four premolars and two molars in place, and wel 
preserved. ‘The former teeth all have two fangs, and smooth, 
sharp compressed crowns. The last premolar only has its sum- 
mit marked by faint notches. The molars have one cone with 
a broad base on the outer side, and three low inner cones of 
nearly equal size. Between these is a deep worn longitudinal 
valley, as in the molars of Allodon, above described. “There is 
no cingulum, and the two molars are of the same size. e 
ies (Clenacodon te : 
The following measurements will indicate the size of this 
specimen : 
Extent of premolar and molar series ___-.---. ---- gum 
Extent of premolar series _ - Be NTN 
Antero-posterior diameter of last premolar Sere Yada fe - 
Height’ of twin. 2 be ee a ee 
Heipht ‘of oondyiew 220 2 id os ee 0 2°5 
WVIGUN Of CONE YIB Core ee 15 
The specimens representing the present species are from the 
Atlantosaurus beds of Wyoming. 
Docodon striatus, gen. et sp. nov. 
The present genus is most nearly allied to Diplocynodon, but 
may be distinguished from it by having, in the lower jaw behind 
“8 canine, ees teeth instead of twelve. The canine has two 
