Tripedalia binata

Description and comparison of adult medusae. Both species with cuboid bell, whitish transparent with a yellowish to brownish tinge in colour, with rounded edge (Figures 3 A, G; Figures 4 A, H). In Tripedalia binata, bell sparsely covered with nematocyst warts, in Tripedalia cystophora nematocyst warts frame mainly bell outline from apex edge to velarium; apex of Tripedalia binata flattened with slight horizontal constriction near the top (Figure 3 G, arrows), apex of Tripedalia cystophora slightly arched, no horizontal constriction; in Tripedalia binata bell heights up to 11 mm, bell width up to 14 mm (interpedalia distance), in Tripedalia cystophora bell height up to 12 mm, bell width up to 15 mm (interpedalia distance). Groups of two (Tripedalia binata) or three (Tripedalia cystophora) flattened, slender knife-blade-shaped pedalia with one tentacle each located at interradial corner of bell rim (Figure 3 D; Figure 4 F); pedalia length ca. 1 / 2 – 2 / 3 bell height. In Tripedalia cystophora outer wing keel length lined by nematocyst band. In both species, pedalial canals show slight bend, round knee; tentacles resemble string of beads with white (Tripedalia binata and Tripedalia cystophora) nematocyst batteries in life specimens (Figure 4 G). Rhopalium located inside rhopalial niche cavity on each side of bell, 1 / 3 of bell height up from margin, (Tripedalia binata, Figure 3 F; Tripedalia cystophora, Figure 4 E), niche forms a roof without upper nor lower covering scale. Short, very faint, “ viking helmet-horn ” - like rhopalial horns extend from top of rhopalial niche in Tripedalia binata (Figure 3 F, arrows), no rhopalial horns in Tripedalia cystophora. Velarium, measuring ca. 1 / 5 – 1 / 6 width of bell base, containing 6, sharp-pointed-triangular velarial canals per quadrant in both species (Figures 3 C, I, J; Figures 2 C, J), in Tripedalia binata main canals flanking pedalia and / or frenulae can grow branches or side canals in further development (Figure 3 J). Mature females in both species show stark white coloured velarial canal tips (Figure 3 I; Figure 4 J). In both species, long, four-lobed manubrium, 1 / 2 to 3 / 4 bell height in length; small, flat stomach communicating with 4 gastric pouches leading into velarial canals. Gastric phacellae in both species epaulette-shaped (Figure 3 E; Figure 4 D). Gonads located in gastric pouches, generally butterfly-shaped and separated by interradial septum, centres of gonad “ wings ” attached to septum, canal system connects gonad “ wings ” through septum.