This is Z6,at 18 dah and 4.4mm.
pp3 show at this stage.Now there are five pairs of walking legs:mp3,pp1,pp2,pp3 and pp5.And five pairs of swimming legs:mp2,mp3,pp1,pp2 and pp3.
Telson is slightly ovoid and shorter than uropods.
Branches of A1 are about half total length.