While engaged in studying the still enigmatical insect, Platypsilla castoris, along Devil's River, Texas in the spring of 1891, on opossum was treed by the dogs one evening, and shot. The following morning I found the animal, which was a female, and though herself dead, the young were still alive and in the pouch of the mother. While examining these I observed that the pouch also contained numbers of fleas. Specimens were captured and sent to the Department of Agriculture at Washington, I being at the time employed by the Division of Entomology.