Huxley, 1859
Agalmatids whose tentilla have a single terminal filament (unicornuate) and only a vestigial involucrum. Characteristic sigmoidal courses for radial canals on the nectosac of the nectophore, that begins with a downward sweep. The post-larval stage of a Halistemma spp. was described by Haeckel (1888) as a separate species, Nectalia loligo. Pugh (1974) correctly surmised its true status, but Alvariño (e.g. 1981) continued to refer to it as a separate species.
Halistemma cupulifera
Halistemma rubrum
Halistemma striata