(Family):A luminous organ on shoulder. No adipose fin. Dorsal and anal fins almost opposite on posterior half of body. (Genus):No pelvic fin. Monotypic genus. (Species):Body highly compressed, flabby, body height subequal to HL. Dorsal and ventral edges of body forming rather acute keel, showing leaf-like appearance. No nodular luminous organ on body, upper and lower edges of caudal peduncle fringed by black presumably luminous tissue. Pectoral fin tiny. Body color dark brown; opercular region, shoulder luminous organ, and anus black.
Distribution:
Cosmopolitan.
Remarks:
This species is the only fish without pelvic fin in the family. (Shimizu)