The Unicorn crestfish (Eumecichthys fiski) is the only species in the genus Eumecichthys, which is one of just two genera in the oceanic family Lophotidae (the crestfishes). This species is rare and known only from the deep sea (possibly around 1000 m), but is apparently widely distributed from South Africa to India, Japan, Hawaii, and Mexico. The head and body are silvery with 24 to 60 dark vertical bands and the fins are red. The highly elongated body may reach 130 cm or more (body depth is around 1/25th of length). The first three or four dorsal rays are produced into a long, narrow pennant that extends far forward of the mouth. The dorsal fin includes 310 to 393 rays, the anal fin 5 to 9 rays, the pectoral fin 13 to 15 rays, and the caudal fin (tail) 12 to 13 rays. (Robins and Ray 1986; Heemstra 2003; Froese and Pauly 2011)

The common name, Unicorn Crestfish, comes from the distinctive projecting supraoccipital, a bone on the dorsal (upper) side of the skull.

A unique feature shared by members of the Lophotidae (Lophotes and Eumecichthys) is the presence of an ink tube (or ink sac). The ink tube allows its bearer to expel black fluid from the cloaca as a defense against predators (Robins and Ray 1986; Honma, Ushiki, and Takeda, 1998).