Quest 1948 Journal 140 June 26 Alvergo San Louis, 800+ ft, 9 mi W. Calmalli, Baja California investigate the vertical slope from the surface. The slope was found to narrow in length as it approached the surface, the actual entrance being about 6 x 8 feet. Across the opening a large trancing timber was firmly placed and others were visible below widely separated. As I approached the opening I saw several large bats flying below which were probably Choeronycteris mexicana. Dr. Benson lowered himself into the slope and immediately scared out a large Brown Owl which flew back into the darkness of the slope interior. He subsequently scared out one Choeronycteris mexicana which I definitely recognized as it flew past me and three Myotis californicus, one of which was knocked down by the net and captured. The Myotis californicus of the slopes were not seen until Dr. Benson had fired several shots into the slope interior which was inaccessible, and we did not leave until he was climbing out the opening - this species seeming very reluctant to fly and leave the shelter. The last Myotis californicus made repeated attempts to enter the opening of the horizontal tunnel further down the hill which was being