Key to Hastatobythites, Saccogaster and Parasaccogaster n. gen.

1 Gill opening ends at or below level of dorsal margin of pectoral peduncle; pectoral peduncle attached to body; skin thick; eye sunk in, subdermal............................................................. Parasaccogaster n. gen. (p.26)

- Gill opening ends above level of dorsal margin of pectoral peduncle; pectoral peduncle free of body; skin thin (except in S. tuberculata); eye not subdermal.......................................................................... 2

2 Narrow head (5.6–6.0 % SL) and body (3.5–3.9 % SL); one anteriorly directed median spine above eyes; three bony ridges on frontal plate......................................................................... Hastatobythites (p.3)

- Broad head (10.5–15.0 % SL) and body (4.2–9.5 % SL); pair of spines above and behind eyes (absent in S. parva); no or single bony ridge on frontal plate................................................................ Saccogaster (p. 5)