1889.] Mineralogy and Petrography. 155 
of the teeth designated. In these the external 
more compressed and less conical than the two species above 
described, resembling more nearly those of the L. evansii. 
The posterior has a weak vertical rib; the anterior a strong 
one. The external cingular cusps are thoroughly fused with 
the external crescents, forming their anterior horns. The an- 
terior horns of the internal crescents are a little more produced 
than the posterior. No external or posterior cingulum ; a 
much interrupted anterior cingulum, which is continued round 
the internal base of the anterior crescent, which is further con- 
tinued on the anterior side of the internal base of the posterior 
crescent. Enamel finely wrinkled. Diameters ; anteroposter- 
ior 14 mm.; transverse, at base, 15 mm. 
OreodontidcB, an inferior first premolar. 
Elotherium mortoni Leidy ; 1. c. 
Remarks. 
The continued scarcity of Oreodontids is matter of surprise. 
Their place is supplied so far, by an increased number of 
Tragulidas (four species). The presence of a genus of Lamb- 
dotheriidse, Haplacodon, increases the impression of anti- 
quity of the fauna produced by the presence of a Creodont 
(Hemipsalodon.) 
MINERALOGY AND PETROGRAPHW 
Petrographical News. — Interbedded with the Tertiary 
schists ot the western Cordilleras in Peru and Bolivia, are 
andesites, which are divided by Rudolph^ into a western area of 
pyroxene-andesites, an eastern area of horn blende-andesites 
and a middle area of a variety intermediate between these two. 
The structure of each class varies from those types in which 
there is a devitrified glassy groundmass, to those in which the 
groundmassis microcrystalline. The plagioclase is andesin that 
has suffered alteration in the center because of the more basic 
character of this portion. The pyroxene-andesitcs contain aug- 
ite twinned parallel to Px,and also an orthorombic pyroxene 
with a cleavage parallel to oop^ and a parting parallel to oP. 
Both augites have in some cases undergone alteration into 
bastite. By an increase in the amount of hornblende the 
