1915.| Matthew and Granger, Lower Eocene Wasatch and Wind River Faunas. 431 
hintere dem zweiten Halbmond gegeniiberliegt und haufig ginzlich 
isoliert bleibt.” 
The construction in Entelonychia he further defines as! “Untere M mit 
einem sehr kurzen vorderen und einem langgestreckten hinteren Halbmond 
und zwei Innenhéckern, von denen der erste stark in die Quere gezogen ist.”’ 
These descriptions apply accurately to the specimen in hand. It is 
not so readily placeable in any of the South American families. It repre- 
sents an extreme type of reduction of the anterior, and elongation of the 
posterior crescent, high and narrow crown, and simple premolars. The 
Isotemnide appear to he nearest, although the genera are decidedly more 
brachyodont and the disproportion of the crescents is less. There is in 
Ly 
4 
a : PLEUROSTYLODON 
SIS 
| 
F< 
NovrostyLops 
IMG. ABI ae Sf 
ame ha ke 
<q 
Nv 
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ee bees Sah, gva a We peer a rat ets 
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Fig. 2.  Arctostylops steini, type specimen, compared with South American Entelonychia. 
Inner views of lower teeth. 
these features a strong suggestion of nearer relationship to Leontinia, 
despite the contrast in size, but I think it is probably illusory. At all 
events there appears to be no known South American genus with which it 
compares closely. I suspect that when better known it will prove to stand 
in the same relation to the Entelonychia as does Metachevromys to the 
Loricata,— an aberrant offshoot from a primitive stage in their evolution. 
It has much nearer allies in the South American faune than has Metachet- 
romys. But this may be because we are able to compare it with Eocene 
types (Notostylops fauna), while our comparisons of Metacheiromys with 
the armadillos are limited to Miocene (Santa Cruz fauna) and later types, 
nothing being known of the skeleton of the older armadillos. Between 
Ts oe, Ie ace 
