io8 Bulletin of Laboratories of Denison University [Voi. xi* 
ley or canon which separates the main range from the western 
foot-hills exposes a vast series of schists of great lithological 
variety. Occasional diorites exhibit the extreme of metamor- 
phism but no true intrusives were seen. All portions of the 
range were not visited and it is possible that some intrusive out- 
break was overlooked but in that case it must have been quite 
insignificant. 
6 . 
THE SAN ANTONIO AREA. 
The area east of San Antonio and thence to De Vaca is 
peculiar and in some respects unique. At De Vaca is a fault 
extending northeast which is in all probability the extension of 
the similar fault seen a short distance east of the town of Ti- 
jeras. The carboniferous lime is here abruptly cut off and the 
Jura-trias appears on the west side with a strong dip to the 
northwest. These strata appear in two ranges of hills to the 
northwest, beyond which the Cretaceous appears either follow- 
ing in normal sequence or, as is more probable, on the down 
side of another fault. The country in this neighborhood is very 
rough, the lower parts of the exposures revealing a dark car- 
boniferous shale, at which horizon coal is occasionally mined, 
as is the case north of the cabins of Gutierez. The upper mem- 
bers are of a yellowish freestone capped with a more dense 
white sandstone. An irregular but rather continuous escarp- 
ment forms a bluff which is a conspicuous landmark from a dis- 
tance whence the land ultimately slopes to the region about 
San Antonito, the interval being filled in with Cretaceous. The 
dip is generally north and northwest but is modified by at least 
one north and south dyke. The one in question is of peculiar 
interest as being probably the last remnant' of a volcano that 
once existed about a mile east of San Antonio. At this place 
is a large amphitheatre of at least a mile in diameter bounded 
to the north, east, and west by the escarpment of Cretaceous 
just mentioned, on the south in part by a low hill of Jura-trias. 
This amphitheatre is now a fertile valley but from its north- 
ern arc a dyke of basic igneous rock pierces the escarpment to 
