Petrobia Ewing 1909 (Bryobiinae: Petrobiini)

It has 3 pairs of prodorsal setae and 10 pairs of opisthosomal setae all borne on prominent tubercles, peritreme ending simply with a bulb-like structure. Empodium curved distally and has two rows of ventrally directed tenent hairs. With 3 pairs of anal and 3 pairs of para-anal setae. Tarsus I has 3 pairs of duplex setae.