1915.] Matthew and Granger, Lower Eocene Wasatch and Wind River Faunas. 467 
Cynodontomys and Microsyops p% are progressively molariform, smaller 
than m; but do not appear to be derived from the peculiar Mixodectes type. 
The type species of Cynodontomys and Microsyops are from the Lysite 
and Lower Bridger, and are in fact so much alike that the genera would be 
better united were it not for the more diverse species found in the Gray 
Bull below and Upper Bridger above. The successive species between 
these two extremes form a progressive series, but the amount of change in 
the teeth is not large as between any two successive stages, and in the molars 
it is hardly appreciable. | 
Metolbodotes. Schlosser! has referred to the Mixodectidee under this 
name a lower jaw from the Fayum Oligocene of Egypt. The only grounds 
that I can discover for this reference are that it has the same dental formula 
as that ascribed to Olbodotes by Osborn (erroneously so, I believe, for a 
careful re-examination of the type of Osborn’s genus by Mr. Granger and 
myself leads to the conclusion that it is identical with Mixodectes). 'The 
teeth of Metolbodotes, so far as one may judge from Schlosser’s figures, are 
wholly unlike those of either Mixodectes or Microsyops, but they agree very 
well with those of Erinaceide, to which family the genus probably belongs. 
It certainly is not related to the Mixodectide and cannot therefore afford 
any confirmatory evidence as to their Insectivore affinities, as Schlosser 
affirms that it does. 
Key to Genera of Mixodectide. 
A. Mizxodectine: Upper molars quadrangular with strong hypocone. P* with high 
robust backwardly curved external cusp and small internal cusp; ps with high 
stout protoconid and low heel. Three premolars. Canine reduced. 
Mizxodectes (Olbodotes), Indrodon. Paleocene, Torrejon beds. 
B. Microsyopine: Upper molars triangular with weak hypocone. pt progressively 
molariform, the cusps corresponding in form and position to those of the molars. 
Three premolars, lower canine absent? 
1. Cynodontomys.. P* with trittocone smaller than protocone, parastyle dis- 
tinct, posterior wing of deuterocone crescent rudimentary; py with deutero- 
conid smaller than protoconid. 
2. Microsyops. P#4 with trittocone and protocone of equal height and size, no 
parastyle, posterior wing of deuterocone crescent fully developed; ps with 
deuteroconid and protoconid of equal height. 
1 Schlosser, 1910, Zodl. Anz., Bd. XXXV, s. 507; 1911, Beit. z. Pal. Oest.-Ung., Bd. 
XXIV; 8:70, taf: in. fe. 5. 
2 Or lower canine much enlarged, incisors absent; see preceding discussion. 
