128 THE DESEADO FORMATION OF PATAGONIA 
genus is, that the crowns are expanded much wider than 
the roots. While there is not yet enough direct evidence 
to prove it, I feel that this and the next genus will prove 
to be deciduous teeth, of either Proadinotherium or some 
related genus. Two species of this genus have been de- 
scribed, both from the upper Deseado. 4 
I. phorcus Amegh., loc. cit. above. 
This species is characterized by its size, the last upper 
molar (so called) measuring 16 mm. long by 14 mm. wide. 
I. deflexus Amegh., 1904, Anal. Mus. Nac. B. A., ser. 3, 
3, Ds 83: 
This species is based on a worn tooth designated as molar 
1 (probably d. pm. 3) 14 mm. long by 19 mm. wide. 
Sse 
Fig. 84. I. phorcus. Fig. 85. I. deflexus, Fig. 86. N. insulatus, 
“Upper molar 3’’—natural “Upper molar 1”’—natural “Upper molar 1’’—natural 
size, after Ameghino. size, after Ameghino. size, after Ameghino. 
Nesohippus Ameghino 
Nesohippus Amegh., rg04, Anal. Soc. Cienc. Argen., t. 56, p. 34 of reprint. 
Nesohippus Amegh., rgo4, Anal. Mus. Nac. B. A., ser. 3, t. 3, p. 218. 
This genus is described as very like the foregoing, but 
differs in having a strong perpendicular style on the ante- 
rior external face of the upper molars. As in the preced- 
ing genus, the crown is considerably expanded above the 
roots. I feel that this genus will also prove to be the milk 
teeth of some one of the genera of this family. One species 
is described, based on a single tooth. 
N. insulatus Amegh., 1904, loc. cit. under the genus. 
The species is just as described under the genus, the last 
upper molar measuring 24 mm. long by 16 mm. wide; given 
as from the upper Deseado. 
