(Fig. 5)
Nauphanta challengeri Haeckel, 1880: 487. Haeckel, 1882: 103–111, pls. XXVI–XXVII.
Nausithoe challengeri —Vanĥffen, 1902: 28.
Holotype NHM 1882.10.9.1.
Material examined: NMNH 58264 (one specimen from the Mid North Atlantic Ocean, 1978, depth: 0–100 m); NHM 1882.10.9.1 (holotype).
Diagnosis: medusa—isodome bell and no mouth lips and manubrium.
Description: Based on original description, Bigelow (1928), Mayer (1910), and Kramp (1961). Adult medusa 12 mm in diameter; deep annular furrow marking the transition from pedalia to central disc; somewhat less in diameter than bell-radius; thin and long tentacles (longer than bell-radius); large bean-shaped gonads; one cluster of gastric filaments per quadrant, each one with about 24 filaments (96 total). No information about polyp stage.
Type locality: Tristan da Cunha Island, central South Atlantic (32°24’S 13°5’W, 2,600m depth)
Distribution: Only known from type locality, and a new record here (mid North Atlantic).
Remarks: The examined specimen (NMNH 58264) matches well with the original description. The animal had a very thick transparent umbrella, with high dome and marginal disc cylindrical, i.e., parallel to the oral-aboral axis. Gastrovascular cavity with 32 short gastric filaments in total and no manubrium (mouth opens directly to the cavity). Sixteen wide marginal lappets with pointed tips and eight rhopalia with statoliths and no ocellus. Eight yellowish-orange oval gonads. Total diameter 13 mm and tentacles up to 4 mm long (probably contracted due to preservation). The absence of mouth lips and manubrium is typical of N. marginata, however, the umbrella shape, the position of the gonads and the animal size match Haeckel’s description of Nausithoe challengeri.