Hooks: 8-9; anterior teeth: none; posterior teeth: 23-25.
Maximum adult body length: 43 mm; tail: 19-24 %.
Body flaccid, broadest at region of tail septum; transversal musculature on trunk; head narrow; hooks serrated in juveniles. One pair of very long lateral fins, both on trunk and tail; lateral fins partially rayed, rounded. Collarette absent; gut diverticula absent. Small eyes without pigment, close together. Seminal vesicles conical; position of seminal vesicles: touching neither posterior fins nor tail fin. Ovaries of medium length; ova large. Adhesive papillae and adhesive organs absent; apical glands present.
Distribution: deep-mesopelagic to bathypelagic; (probably) very wide distribution.
Remarks: displays tropical submergence.
Type locality: North-east Pacific.