Bellottia Giglioli, 1883: 399, type species Bellottia apoda Giglioli, 1883 by monotypy (type locality: Gulf of Naples, Italy).
Xenobythites Smith & Radcliffe in Radcliffe, 1913, type species Xenobythites armiger Smith & Radcliffe in Radcliffe, 1913: 173 by original designation (type locality: Mindanao, Philippine Isls.)
Diagnosis. The diagnosis in Nielsen et al. (1999: 97) is here slightly modified based on additional material. Body short, depth at origin of anal fin 13.0-23.0 % SL, head partly scaled, 3-5 spines at lower half of hind margin of preopercle, a pointed spine near upper angle of opercle, palatine teeth present, a few, large sensory pores behind and below eye and on mandible, long rakers on anterior gill arch 3-6, pectoral fin rays 19-28, pelvic fins absent, precaudal vertebrae 10-13, males with large genital hood.
Similarity. The subfamily Bythitinae is characterized by continuous dorsal, caudal and anal fins and the penis being an integrated part of the large genital hood. In addition to Bellottia, two genera contain species that lack pelvic fins: Pseudonus Garman, 1899 and Hephthocara Alcock, 1892. The former of these is most similar to Bellottia with one species without and 1-2 species with pelvic fins, large sensory pores on head, a partly naked head and a very similar otolith. Hephthocara holds 1-2 species both without pelvic fins, but with no large sensory pores, a naked head and an otolith less similar to that of Bellottia.
Species. Besides the five species mentioned in the introduction, Nielsen et al. (1999: 97) noted that two specimens collected in midwater (one from off Portugal and one from the Galapagos Islands) may represent undescribed species. Unfortunately, neither of the two specimens can be located.