1915.] Matthew and Granger, Lower Eocene Wasatch and Wind River Faunas. 21 
Didymictis protenus (Cope 1874). 
Limnocyon protenus Cope 1874, Rep. Vert. Foss. New Mex. , p. 15; (Didymictis) 
1875, Syst. Cat. Vert. Hoc. New Mex., p. 11; 1877, Ext. Vert. New hee p. 123, pl. 
xxxix, figs. 1-9; 1885, Tertiary Varobraia, p. oll; in part. 
Syn. Piipeiiche curtidens Cop 1882, Pal. Bull. 34, Proc. Am. Phil. Soe. Vol. XX, 
p. 160; Tert.. Vert. p. 313, pl. xxivd, fe 10. 
Type, U.S. Nat. Mus. No. 1092, lower jaws from the New Mexican Wasatch. 
Distinctive characters: Pi-m, = 55-60 mm.; mj_. = 19-22 mm. Parastyle of m! 
considerably extended, with oblique crest, no distinct metastyle on cingulum. 
This is the typical and best known species of the genus, and is repre- 
sented in our collections by a large series of specimens, including several 
skulls, with fragmentary skeletons, and numerous upper and lower jaws. 
The greater part are from the Big Horn Basin, but three lower jaws are from 
the New Mexican Wasatch, a number of parts of jaws from the Wind River 
and Clark Fork basins, and a single jaw fragment from the Evanston 
Wasatch. 
The New Mexican specimens agree fairly well with the type; they 
represent both upper and lower horizons. ‘The specimens from the Lysite 
level in the Big Horn and Wind River basins, are uniformly larger and are. 
referred to a more progressive mutant. To this variety also belong a num- 
ber of Big Horn specimens of earlier collections; their horizon is not exactly 
recorded, but from such records as exist of level and locality, and from the 
character of matrix and preservation, it appears that they are from the 
Lysite or.the upper levels of the Gray Bull. Among these are the speci-. 
mens figured by Cope in 1885 and Matthew in 1901. This larger variety 
(D. protenus lysitensis infra) 1s not recognized in the New Mexican Wasatch, 
but the Evanston specimen appears to be referable to it. 
Didymictis curtidens was based upon a lower jaw fragment in which the 
space behind the carnassial for mz is less than normal; but this may be due 
to immaturity or to abnormal retardation of the eruption of mpg; it is not 
distinguishable otherwise nen protenus and no other specimens confirm its 
supposed characters. 
Didymictis protenus lysitensis mut. nov. 
Didymictis protenus Corr 1885, Tert. Vert. p. 311, pl. xxvd, figs. 4 and 5; (Viver- 
ravus) MarrHEew 1901, Bull. A. M. N. H., Vol. XIV, p. 8, figs. 1-5 
Type, No. 15639 from Lysite of 15-mile Creek, Big Horn Basin, Wyoming. 
Distinctive characters: p:-M2 = 65-70 mm.; mi-2 = 21-24 mm. _Parastyle of m! 
~ much extended with oblique crest, sometimes double cusped; metastyle a more or 
less distinct cusp. 
