Dana, 1853
Head as tall as, or taller than long, except rarely almost as long as pereonites I-III combined, galeate or with plow-shaped protuberance on forehead, with downturned rostrum. ANT I with multi-articulate accessory flagellum, base of primary flagellum composed of several fused ART in males. MD ordinarily with weak palp, but tumid in Synopia. Inner lobes of lower lip separate, outer lobes frequently notched. Mandibular molar well-developed. P I and II weakly subchelate or simple. Coxae more or less long, CX IV never much larger than CX III. Telson elongate, rarely short (for example, in Synopia).
Fifteen genera, mainly benthic. Only one genus in the South Atlantic plankton:
Genus Synopia Dana, 1852