The species key provided can be used without dissection. McCain (1968) includes a lateral view of a generalised caprellid showing the names of the different parts. Consultation of these figures could be useful for the use of the key
1. Pereopods 3 and 4 absent.. Antenna 2 setose ........................... Caprella scaura (Fig. 2)
– Pereopods 3 and 4 present, although very reduced. Antenna 2 not setose....... 2
2. Pereonites 6 and 7 fused................................................................................................ 3
– Pereonites 6 and 7 not fused.......................................................................................... 4
3. Body with dorsal projections ....................................... Metaprotella sandalensis (Fig. 8)
– Body dorsally without dorsal projections............. Metaprotella mauritiensis (Figs. 4–7)
4. One or two dorsal projections on the head.................................................................... 5
– Head smooth without projections.................................................................................. 6
5. Two acute projections dorsally on the head. Pereopods 3 and 4 reduced but visible..... ...................................................................................... Orthoprotella australis (Fig. 10)
– Only one dorsal projection on the head. Pereopods 3 and 4 very reduced. Very small size........................................................................... Noculacia sp (Fig. 9)
6. Gnathopod 2 setose, pereonites 5–7 short and robust. Abdomen not visible in the lat eral view .................................................................................. Paracaprella sp (Fig. 11)
– Gnathopod 2 not setose, pereonites 5–7 elongate. Abdomen projections visible in the lateral view......................................................... Hemiaegina minuta (Fig. 3)