In a small collection of mammals recently sent by Dr. G.F. Gaumer from Izamal, Yucatan, to this Museum for identification, is a single specimen of a species of Adelonycteris , which appears to be undescribed. It may be called Adelonycteris gaumeri , sp. nov. Above dark brown, with an olivaceous wash, the fur being uniform dark brown to the base tipped with a slight tinge of olivaceous, the extreme tip slightly grayish in certain lights; below much lighter, the fur being dark brown basally and br