oeg Bulletin American Museum of Natural History. [Vol. XXXIV, 
also from the Lysite). It has not been found in New Mexico. In the Wind 
River basin it is represented in the Lysite horizon by a nearly related but 
uniformly smaller variant H. browne. 
Hyopsodus powellianus browni Loomis. 
Hyopsodus browni Loomis, 1905, Am. Journ. Sci., Vol. XIX, p. 422, fig. 7. 
Syn., H. jacksoni, H. lawsoni loc. cit., p. 428, fig. 8. 
Type, a lower jaw fragment in the Amherst Museum. 
The fourth premolar of Dr. Loomis’s type is altogether exceptional in 
the lack of any strong deuteroconid. This is not the normal character of 
the species as shown by a large series of topotypes in the American Museum 
collection. The supposed third premolar of H. jacksoni (“lawsonz” in 
figure) appears to be the fourth premolar of a smaller individual. While 
the topotype series shows some variability in the form of m? and a few other 
characters they run fairly constant in size and in most characteristics and 
there is no indication of the peculiar features on which Dr. Loomis character- 
ized these two species, and which are not normally present in any species 
of this genus, although they occur occasionally as abnormalities. I regard 
the series as representing a single subspecies intermediate in size between 
H. powellianus and mentalis and somewhat more primitive than either. 
The heel of the last molar is more elongate than in H. mentalis, the heel of 
p3 has no inner cusp, and the size is larger. These characters ally it with 
powellianus. It is abundant in the type locality, Cottonwood Draw (Bridger 
Creek) in the Wind River basin, and found more rarely in the Lysite of the 
Bighorn basin. A few doubtful specimens are found in the Lost Cabin 
horizon. 
Hyopsodus walcottianus sp. nov. 
Type, No. 14654, upper and lower jaws, parts of limb bones and hind foot, from 
Lost Cabin beds, Wind River basin. 
Distinctive Characters. Larger than H. powellianus, a ecties of p®-4 more 
conical with no anterior crescent-wing, deuteroconid of ps more posterior in position, 
ps more robust, less spatulate, basal cusps of lower premolars and external styles of 
upper premolars more distinct. Length m!* = 18; m,_3 = 21 mm. 
This is the largest known species of the genus, and appears to be the 
Lost Cabin successor of H. powellianus of the Lysite beds. It has therefore 
seemed appropriate to name it after the distinguished paleontologist who 
was Major Powell’s successor as director of the Geological Survey. 
In addition to the type, two lower jaws are referred here, one from the 
