Platythelphusa A. Milne-Edwards 1887

1 Anterior margin of front deflexed, lacking well­defined teeth on external corners..... 2

­ Anterior margin of front almost horizontal, with well­defined sharp teeth on external corners........................................................................................................................ 3

2 External angles of front rounded, frontal margin granular. Small epibranchial tooth, one larger tooth on anterolateral margin in mesogastric region (Pl. XXIV)................................................................................................................................. P. praelongata

­ External angles of front square­shaped......................................................................... 4

3 Frontal margin lined with tooth­like tubercles............................................................. 7

­ Frontal margin lined by granules................................................................................ 8

4 Merus of p5 shorter than front width. One tooth on the anterolateral tooth behind the epibranchial tooth, equal in size to the epibranchial tooth (Pl. XXIII)............. P. polita

­ Merus of p5 either longer than, or almost equal to, front width.................................. 5

5 Epibranchial lobes distinctly raised. Inferior margin of ischium of p1–p5 with distal spine (Pl. XXV)....................................................................................... P. tuberculata

­ Epibranchial lobes indistinct. Distal spine on inferior margin of ischium of p1–p5 lacking........................................................................................................................ 6

6 Inferior margins of meri and propodi of p2–p4 each with a row of distinct spines (Pl. XX)...................................................................................................................... P. echinata

­ Inferior margins of meri of p2–p4 granulate, inferior margins of propodus of p2 with several minute spines, inferior margins of propodus of p3–p4 smooth (Pl. XXII)............................................................................................................................. P. maculata

7 Distal tooth of meri of p2–p4 pointed spine (Pl. XVIII).......................... P. conculcata

­ Distal tooth of meri of p2–p4 either low or lacking..................................................... 8

8 Subdistal tooth of meri of p2–p4 either low or lacking (Pl. XVII)................ P.armata

­ Subdistal tooth of meri of p2–p4 a sharp spine............................................................ 9

9 Carapace flattened (ch/fw <1.0) (Pl. XXI).............................................. P. immaculata

­ Carapace high (ch/fw>1.0) (Pl. XVII).................................................... P. denticulata