Leuckart, 1854
Siphonophores without an apical pneumatophore. The nectosome usually consists of one or two, often dissimilar, nectophores, although up to ca. 15 are present in the family Hippopodiidae. The cormidial elements consist of a bract, a gastrozooid, with tentacle, and a succession of gonophores. Again the Hippopodiidae are exceptional in that they do not possess bracts. There are no palpons, with the possible exception of one species. Asexual swimming bells have also been reported in some species, but these may be the first (spent) gonophore retained. In many species the mature cormidial units are set free from the stem to lead a separate existence, known as the eudoxid or sexual stage.
About 100 species distributed amongst 6 families. The families usually can be distinguished by the basic shape of the nectophores and bracts; however, the key presented here, cannot take account of every specific variation, or all the larval stages (see Page 321 ) .
Family Prayidae
Subfamily Amphicaryoninae
Subfamily Prayinae
Subfamily Nectopyramidinae
Family Hippopodiidae
Family Diphyidae
Family Clausophyidae
Family Sphaeronectidae
Family Abylidae