1. Body elongate, moderate in size; hind coxae oblique; eyes separated by less than the width of one eye; hind tibiae and tarsi bearing numerous long and stout spines; tarsal formula 4-5-5 or 4-4-4; living in fresh and sea water habitat. .......THAUMASTODINAE
-. Body semicircular to elongate, small to large size; hind coxae transverse or ovoid; eyes seprated by more than the width of one eye; hind tibiae and tarsi without numrous long and stout spines; tarsal formula 5-5-5 or 4-4-4. ..........2
2. Tarsal formula 5-5-5; hind coxae transverse and very closely approximated at their inner ends; metaventrite with a transversal groove close to the postrior edge. ........3
-. Tarsal formula 4-4-4; hind coxae ovoid and separated by more than the width of one coxa; metaventrite withour a transverse groove; living in sea water habitat. ....HYPHALINAE
3. Pronotal hypomera with an oblique ridge running forwards and inwards from the postero-outer angle. ........CEPHALOBYRRHINAE
-. Pronotal hypomera without an oblique ridge. .............LIMNICHINAE