Illustrated key to the species of Spiralothelphusa Bott, 1968

1. G1 with longitudinally less strongly twisted (half turn) terminal segment and distal portion of subterminal segment (Fig. 7A) .......................................................................................................... 2

– G1 with longitudinally more strongly twisted (full turn) terminal segment and distal portion of subterminal segment (Fig. 7B) .......................................................................................................... 5

2. G1 tip gently curved upwards (Fig. 7C); G1 non-twisted portion with gently curved outer margin (Fig. 7C)...................................................................... Spiralothelphusa hydrodroma (Herbst, 1794)

– G1 tip almost straight to gently hooked downwards (Fig. 7D–F); G1 non-twisted portion with strongly or sharply curved outer margin (Fig. 7D–F)........................................................................ 3

3. Male telson with gently concave lateral margins (Fig. 7G); G1 non-twisted portion with sharply curved outer margin (Fig. 7D).......................................... Spiralothelphusa senex (Fabricius, 1798)

– Male telson with straight lateral margins (Fig. 7H–I); G1 non-twisted portion with regularly curved outer margin (Fig. 7E–F) ................................................................................................................... 4

4. Male pleonal somite 6 relatively narrower, proximal width circa 1.3 times medial length (Fig. 7H); male telson equal in length to male pleonal somite 6 (Fig. 7H); G1 non-twisted portion with relatively less strongly convex outer margin (Fig. 7E)........................... Spiralothelphusa fernandoi Ng, 1994

– Male pleonal somite 6 relatively broader, proximal width circa 1.6 times medial length (Fig. 7I); male telson slightly longer than male pleonal somite 6 (Fig. 7I); G1 non-twisted portion with relatively more strongly convex, hump-like outer margin (Fig. 7F) ................................................................... ....................................................................... Spiralothelphusa gibberosa Pati & Sudha Devi, 2015

5. G1 relatively stout, with tip strongly curved upwards (Fig. 7J) .......................................................... ....................................................................................... Spiralothelphusa parvula (Fernando, 1961)

– G1 relatively slender, with tip gently hooked downwards (Fig. 7K–L) ............................................ 6

6. Male telson with concave lateral margins (Fig. 7M); G1 non-twisted portion with outer margin sharply, relatively less strongly curved and straight towards base (Fig. 7K) ...................................... .................................................................................... Spiralothelphusa wuellerstorfi (Heller, 1862)

– Male telson with almost straight lateral margins (Fig. 7N); G1 non-twisted portion with outer margin regularly, relatively more strongly curved and distinctly notched towards base (Fig. 7L) ................. ....................................................................................................... Spiralothelphusa andhra sp. nov.