On Some Little-known Melanostomiidae with the Description of a New Species ofEustomias

A new species,Eustomias mikhailinisp. nova, close toE. macrurawas described. It is proposed to restore theUrostomiassubgenus from the synonymy of theSpilostomiassubgenus. An identification key for the subgenera of the genusEustomiaswith a high number of rays of the pectoral fin and for the species of the subgenusUrostomiasis presented. A specimen ofEustomiasgr.melanostigma, which combines the features of different species of this group in its structure of the chin barbel, was described, which raises doubts about the validity of the isolation ofE. melanonemaandE. melanostigmoides. New occurrences of rareLeptostomiascf.bilobatusandPhotonectes xenopogonspecies, first discovered in the southeastern Pacific Ocean, were reported; detailed morphological descriptions of specimens are given; the limits of variability of diagnostically valuable characters are specified.