744 N. H. DARTON 
Near Purisima Vieja, on the Arroyo San Gregorio, 12 miles 
northwest of La Purisima, a thin lava bed lies at the base of the 
formation (or in the top of the yellow beds, see Fig. 16), and a 
short distance above that place is a vent from which this lava 
flow probably came. Near San José, 7 miles farther up the same 
canyon, conglomerates predominate in the high canyon walls and 
two sheets of basalt are included. The later are well exposed 
in Arroyo Caije near Rancho Nombre de Marie, 25 miles south- 
south west of Mulegé. In the extensive exposures of the agglom- 
erates and conglomerates near San Miguel on the Arroyo Raimondi 
(or Miguel), as shown in Figures 15 and 20, a thin sheet of trachyte 
is included in the succession. Near Rancho los Angeles in the same 
canyon the cliffs 500 feet high consist of coarse conglomerate, some 
beds being harder than others and consisting largely of bowlders of 
igneous rocks in gray sand. Below Rancho Mescal, a few miles 
above Rancho las Tules, underlying gray sandstone appears lying 
in yellow beds and in places on agglomerate which displaces 
the upper members of the yellow beds. These features are also 
well exposed halfway between Rancho las Tules and Rancho San 
Antonio. Not far below the latter place the basalt beds of the 
mesa sandstone thin out and the lava of the mesas lies directly on 
top of the yellow beds. The relations in this arroyo are shown in 
Figure 15. 
Mesa sandstone appears at San Vicente, a ranch 5 miles south- 
east of La Purisima, where a fine spring issues from it, and is well 
exposed along the arroyos San Antonio and Pabellon 10-20 miles 
south of La Purisima. In the latter there are high bluffs of it at 
Rancho Pabellon and extending to beyond Coyote hole a watering- 
place as head of tidewater, 20 miles south-southwest of La Purisima. 
Here the rock is soft sandstone, in part pale greenish and yellowish. 
It is capped by caliche and conglomerate of Quaternary age which 
covers the adjoining mesas. The yellow tint may be due to a 
mixture of detritus from yellow beds which do not outcrop in this 
vicinity. 
In the deep canyon of the Arroyo Comondu, near the village 
of Comondu, there are high walls of mesa sandstone capped by 
basalt .of the lava sheets which cover the adjoining mesas, and 
there is also a cap of basalt at lower level, apparently a remnant 
