The Freshwater Algae of Africa. 



561 



Long., 3^/x ; lat., 26/a; lat. isthm., 12/x. All individuals triangular 

 in end-view. 



3. Staurastrum hexagonale, n. sp. ( Fig. 32.) 



S. subparvum, cireiter I}, plo longius quam latum, modice con- 

 strictum, sinu acutangulo Late aperto. Semicellulae transverse hexa- 

 gonae, angulis lateralibus leviter productis, angulis omnibus plus 

 minus rotundatis; apicibus rectis truncatis ; marginibus lateralibus 

 superioribus fere rectis, marginibus lateralibus inferioribus reotis vel 

 leviter concavis. A vertice visae tri- vel quadrangulares, angulis 

 rotundatis, lateribus plus minus concavis. Membrana in parte 

 centrali semicellularum laevis, sed angulis granulis parvis rotundatis. 



Fig. 32. — Staurastrum hexagonale, n. sp. * 7~>o. 



eoncentrice dispositis, munitis, iis in apice anguli utriusque paullo 

 majoribus, plus minus acutis, etiam dentiformibus. 



Long.. 33-36ju.; lat., 25-30 /a; lat. isthm., 10-12 fi; crass., 19-20 fi. 



Samples 8, 19. 



This species is characterised by the hexagonal shape of the semi- 

 cells in front-view (Fig. 32). In this respect it differs markedly 

 from the nearly allied 8. punctulatum, Breb. Other points of 

 distinction are: (a) The more marked rounding of the ends and 

 the concavity of the sides in end-view: (b) the absence of granules 

 from the central part of the semicells ; (c) the tooth-like character of 

 the granules at the ends: and (d) the proportionally greater length. 

 In outline it bears some resemblance to S. anguloswm, Schmidt (which, 

 however, I only know from the inadequate figures in Migula, Krypto- 



