Dana, 1852
Lateral lobes of head not sharp. Eyes large (Synopia scheelana 1; Synopia ultramarina 1). Small secondary eye on each side, at base of ANT I. MD of medium size (Synopia ultramarina 2), with medium-large molar, triturative, or swollen and pillowlike, but poorly triturative. Mandibular palp extremely tumid. CX III strongly expanded distally, with strong posteroproximal excavation; CX IV small, situated in posterior excavation of CX III (an unusual character, commonly observed in coxae IV and V in some other gammarideans). ART 6 of P I and II slender or tumid, subovate, not linear, may bear marginal setae, lacking strong spines. Dactyl of P II small. Pleonites I-III not denticulate. Basipodite of UR III short, subequal to telson (Synopia scheelana 3; Synopia ultramarina 3). Telson short, cleft or entire, in the latter case distally trifoliate. Purely pelagic (epipelagic) genus.
Nine species, 3 in the tropical South Atlantic:
Synopia caraibica (Known from Caribbean Sea.)
Synopia gracilis Dana, 1853
Synopia scheelana Bovallius, 1886
Synopia ultramarina Dana, 1853
Genus poorly reported in literature. For discussion of two more Synopia species found only in the northern part of the tropical Atlantic Ocean, and not treated here, see (Andres, 1984).