We propose to dedicate this new species, to our valuable friend the justly celebrated naturalist J.J. AUDUBON, as a small tribute of respect to his eminent talents, and the highly important services he has rendered science. The drawing which accompanies this paper, is from his inimitable pencil. This species was first observed, during the summer of 1829, when an individual female flew into the apartment of the late Dr. Hammersly, then one of the resident physicians of the Pennsylvania hospital: on the subsequent evening a male individual, of the same species, was also taken in the same manner. In August 1830, a very fine specimen was brought to the Academy of Natural Sciences, and Mr. Audubon informs me that the species has very recently been observed in New York. The natural characters of the species are--General colour black, sprinkled with gray above and beneath; ears black and naked; auriculum, short and broad or obtusely triangular; interfemoral membrane, sparsely hairy; last joint of the tail free: two incisors, with notched crowns, on each side of the canine teeth of the upper jaw, with a broad intervening space without teeth. The dimensions are.--Total length 3 inches 7 tenths; tail 1.7; length of ear 0.5. breadth of ear 0.4; length of leg 1.7; spread of wings 10.7. inhabit Pennsylvania and New York, and probably the southern states.--_Cab. of Acad. Nat. Sc. Philad._ (Abridged from Featherstonhaugh's _Monthly American Journal of Geology and Natural Science._) * * * * * FINE ARTS. * * * * * MOSAIC PAVEMENT.