Mt. Casaguate, Dept, San Miguel, Salvador. Nov, &1, 1925 - Dec, 23, 1924 Water mouse - Rata de la agua Water mice were found commonly in small rocky canyon streams in the sub-tropical zone. In places these streams were quite swift and with many little falls; at no place was the water quiet and it was always clear and cool. These little streams, across which I could step in most any place, usually ran through the coffee, however frequently they placed through patches of brush only to meet again with coffee, banana gloves, or cornfields farther along their courses. The Water mice were caught with large snap traps with no bait set in the most logical places in the stream. In many places I staked placed rocks in the stream so that the water could trickle through but only left one place for a water mouse to pass, and there I set my trap. I found that baited traps were tooattracting to other mice especially Sub-Tropical peromyscs and Yellow mice (Oryzomys). One specimen No. 10882 I was caught in a more quiet stream under some lilly pads, and another No. 10843 I was caught a little farther down the stream under some heavy grass which overlapped the water. This stream was bordered on one side by an old corn patch and on the other by a dense weed and brush thicket. A Water mouse which was caught alive