Quadrant 1948 Journal 59 May 24 Las Cuevas, 23°34'N, 109°39'W Baja California a large arroyo that cuts its way in a northerly direction through a large flat valley. The arroyo walls are about 200 feet high and rise vertically from the sand of the arroyo bottom which is about 1/4 mile in width at the town. Caverns occur in the sandstone walls with their floors level with the wash bottom, attesting to their origin by water action during flood time. Three such caves were visited in that region. The first cave visited was across the arroyo from the town and faced in a south-west direction. An irrigation ditch of small size ran in front of its mouth and numerous large-leaved saplings grew in its entrance. The smell of guano greeted (?) our noses the minute we stepped into the exterior, and heard the chittering of bats at the back of it. The cave was about eighty feet in depth and about 15 feet wide for most of its length, with the ceiling divided into three concave regions, the innermost being the largest (approx 10x15 ft). Numerous crevices extended back into the rock and many hollows opening downward occurred in the back of the cave. The floor was irregular, being composed of the same black dusty material that we went through at the cave at Mulege. The bats were present by the hundreds, whole areas, some 5x7 feet, being covered with a layer of