180 WELWITSCh's AFRICAN FRESHWATER ALG.E. 



12. S. actinotum, sp. n. (tab. 369, fig. 4). S. subparvum, 

 circiter li-plo latins quaui longins (sine spinis), profunde cou- 

 strictum, sinu acuto et aperto ; semicellnlpe transverse elliptico-fusi- 

 formes, apicibus snbtruncatis, spina acutissima singula subcurvata 

 ad angulum subacutum unumquemque horizontaliter disposita, 

 seriebiis transversis duabus granulorum minutorum trans angulum 

 unumquemque, serie verrucarum emarginatavum circiter G in mar- 

 gine apicis ; a vertice visa) rotatfe, sexaugulares, lateribus profunde 

 concavis et minute undulatis, spina gracili longa subcurvata acuta 

 ad angulum subacutum unumquemque, seriebus duabus granulorum 

 minutorum trans angulum unumquemque, cum annulo verrucarum 

 emarginatarum 12 intra marginem, duabus earum sub base auguli 

 uniuscujusque dispositis. Long. 23 ji ; lat. sine spin. 30 ji, cum 

 spin. 57 /x ; lat. istbm. 9-5 /x. 



Huilla. In paludibus exsiccandis ; April 1860. No. 170. 



This peculiar Staurastrum does not appear to be closely related 

 to any other. 



Var. SIMPLEX (tab. 369, fig. 5). Var. semicellulis sine annulo 

 apicali verrucarum emarginatarum ; semicellulis late obtriangulari- 

 bus, apicibus latis et subiectis ; a vertice visis pentaradiatis ; spinis 

 validioribus longioribusque. Long. 30 /x ; lat. sine spin. 35 //., cum 

 spin. 63 /x ; lat. isthra. 15 /x. 



Huilla. Inter Utricxdariaw , Morro do Lopollo ; April 1800. 

 No. 179. 



13. S. cassidum, sp. n. (tab. 308, fig. 21). S. parvum, circiter 

 duplo longius quam latins, profunde constrictum, sinu lineari ; 

 semicellulfB conico-pyramidatfe, apicibus et angulis basalibus ro- 

 tundatis, lateribus rectis vel leviter retusis ; a vertice visfB triangu- 

 lares, angulis acute rotundatis et levissime productis, lateribus 

 rectis, isthmo trigone, angulis unius semicellulfe cum iis alterius 

 alternantibus ; membrana punctata et leviter incrassata ad apices 

 semicellularum. Long. 38'5-42 /x; lat. 20-22 /x; lat. isthm. 

 7-5-9-5 jx. 



Huilla. In uliginosis editioribus prope Humpata, Empalanca 

 et Lopollo ; May 1800. No. 15. 



This species is distinguished from S. trihedral e'WoWe {Desm. U.S. 

 123, pi. 40, f. 12-14 ; West & G. S. West in Traus. Linn. Soc. 

 2nd ser. v. 200-1, t. xvi. f. 29) by its smaller size, its more conical 

 semicells with comparatively broader apices and almost straight 

 sides, by the form of its vertical view, and by the much smaller and 

 more numerous markings on the membrane. S. trihedrale var. 

 rhomboidcum West & G. S. West {I. c. f. 30) seems to be intermediate 

 in form between this species and S. trihedrale, but it has the charac- 

 teristic basal angles, the narrow apex, and the markings of /S'. tri- 

 hedrale, whereas none of these characters are possessed by 8. cassidum. 



14. S. areolatum, sp. n. (tab. 307, fig. 17). S. magnum, 

 duplo longius quam latius, profunde constrictum, sinu sublineari 

 et aperto extremo rotundato ; semicellulie subquadrata) angulis 

 rotundatis ; a vertice visje trigone lateribus rectis ; membrana 

 crassa, ad apicem crassissima, valde scrobiculata, scrobiculis majori- 



