Key to Brazilian Trischizostoma species (all from entire telson group)

1. Coxa 2 subtriangular and with sharp anterior margin .................................................. 2

­ Coxa 2 subquadrate and with rounded anterior margin ............................................... 3

2. Eyes present; gnathopod 1 propodus subtriangular, telson distally emarginate (Fig. 4) ...................................................................................................... Trischizostoma raschi

­ Eyes absent; gnathopod 1 propodus subquadrate and with anterior lobe, telson distally rounded (Fig. 2) ................................................................. Trischizostoma denticulatum

3. Gnathopod 1 propodus quadrate; pereopod 3 basis 2 X length of propodus, telson distally truncate (Fig. 3)........................................................ Trischizostoma longirostrum

­ Gnathopod 1 propodus oval; pereopod 3 basis 3 X length of propodus, telson distally subacute......................................................................................................................... 4

4. Eyes very large, covering almost the entire head; gnathopod 1 palm with 19 short robust setae and 3 pairs of long robust setae distally (Fig. 5) ... Trischizostoma richeri

­ Eyes large, covering half­length of head; gnathopod 1 palm with 11 short and long robust setae and 3 pairs of long stout setae distally (Fig. 6) .......................................... ......................................................................................... Trischizostoma costai sp. nov.