During the 2010 National Park Service BioBlitz at Biscayne National Park, Homestead, FL, barnacles were collected from a submerged mangrove log near the Park headquarters. From the washings of the crushed barnacles, Archechiniscus biscaynei nov. sp. was extracted. This new species can be distinguished by its lack of a median cirrus, its large peduncles at the base of the external claws, the rounded cephalic clava between the internal and external cephalic cirri, a club-shaped papilla above the base of leg IV, and bulbous papilla just above the claws on the anterior of legs I, II, and III. A table of comparison of characteristics among the four known species and a key to their identification are provided.