Stridulating organ present on posterior branchiostegite

Stridulating organ consisting of 5 to 7 very strong ridges in a wide and straight band

Another edge of thelycal plate entire

Lest petasma lobe sharply pointed and triangular

12 to 24 stridulating ridges, the ridges are arranged in a curved band directed anteroventrally from the posterior margin of the carapace

Stridulating organ absent from posterior branchiostegite

Hepatic sulcus absent or not reaching to ventral edge of branchiostegite

A pair of teeth like plate;ets immediately posterior to thelycal plate