1 Cheliped propodus with one ventral seta; cheliped fixed-finger almost straight, with two prominent teeth; uropod exopod well-developed, as long as article 1 of endopod ............... Siphonolabrum tenebrosus n.sp.
- Cheliped propodus with two ventral setae; cheliped fixed finger convex, with more numerous, less prominent teeth; uropod exopod very short, bud-like.......................................................................................... 2
2 Pereonites 4–5 clearly longer than broad; pereopods 3–6 with unspecialized spiniform setae on merus and carpus; shelf-bathyal species ....................................................................................... Anarthruropsis longa
- Pereonites 4–5 shorter than broad; pereopods 3–6 with clavate, pectinate and bifid spiniform setae on merus and carpus; hadal species ....................................................................................................... A. langi