WELWITSCh's AFRICAN FRESR-^'ATER M,GJE. 179 



apicibus rectis et lateribus subrectis, spinis longis tenuibus acutis 

 curvatis circ. 4 ad latus unumquodque ; a vertice visfe triangulares, 

 lateribus leviter concavis, angulis truucatis cum spinis longis 

 curvatis leviter divergentibus 4-5 instructis ; membrana glabra. 

 Long, sine spin. 15-17 /x, cum spin. 21-27 /i; lat. sine spin. 

 16-17 /x, cum spin. 27-29 /x; lat. istbm. C-5-7-5/x; long. spin. 4-G-o/x. 



Huilla. In paludibusexsiccandis; April 1860. No. 176. Etiam 

 inter Utricularknn, Morro de Lopollo ; April 1860. No. 179. 



This species differs from 5. IIi/striA- Ralfs in its smaller size, its 

 more angular semicells, its fewer, longer, thinner, and curved spmes 

 which are confined to the face of the truncate angles. 



10, S. Welwitschii, sp. n. (tab. 369, fig. 1). S. subparviim, 

 paullo longius quam latius (sine spinis), modice constrictum, sinu 

 aperto extremo obtuso; semicelluhB oblongo-rectangulares, angulis 

 rotundatis, apicibus latis et subrectis, spina valida suberecta ad 

 angulum inferiorem unumquemque, spinis subincurvatis apices 

 versus, spinis brevibus acutis 5-6 ad marginem lateralem utrobique; 

 spinis parvis 10-15 (circiter) ad angulum unumquemque irregulariter 

 dispositis et spina valida erecta supra eas ; a vertice visie penta- 

 gonfe, angulis rotundatis et spinatis, lateribus concavis et glabris. 

 Long, sine spin. 34-45 //, cum spin. 45-51 [i ; lat. sine spin. 

 29-31 ji, cum spin. 34-37 /^ ; lat. isthm. 16-18 /x. 



Huilla. In paludibus exsiccandis; April 1860. No. 176. 

 This is a very characteristic species. 



11. S. Corbula, sp. n. (tab. 369, fig. 2). S. parvum, 1^-plo 

 longius quam latius (sine spinis), profimde constrictum, sinu aperto 

 extremo rotundato ; semicelluLie transverse oblonga), marginibus 

 lateralibus rotundatis, apicibus latis (subrequalibus in latitudine 

 cellulis) et rectis, spinis gracilibus erectis et leviter curvatis 2 ad 

 angulum superiorem unumquemque, spinis brevissimis conicis 

 circiter 7 ad margines laterales, et seriebus duabus (circ.) intra 

 marginem imumquemque ; a vertice visa) triangulares angulis late 

 rotundatis, spinis brevissimis 7-8 ad angulos in ambitu et spinis 

 similibus 11-12 intra marginem angulorum, lateribus glabris, rectis 

 vel subconcavis. Long, sine spin. 27 ji, cum spin. 36 /a ; lat. sine 

 spin. 23 /x, cum spin. 25 //. ; lat. isthm. 9*5 /x. 



Huilla. In paludibus exsiccandis ; April 1860. No. 176. 



This species has about twenty-five very short spines on each of 

 the three angles of a semicell, over which is placed a pair of slender, 

 erect and longer spines. It most nearly approaches N. Wi'licitxehii 

 in form and arrangement of spines, but differs from it in being tri- 

 angular in vertical view, and in having a pair of slender erect spines 

 in place of the single stout spine of the latter species. The angles 

 are also furnished with more numerous and shorter spines, and it 

 is moreover a smaller, much more constricted species. 



Var. PULCHRUM (tab. 369, fig. 3). Var. semicellulis lateribus 

 retuso-emarginatis ad medium et apicibus concavis ; a vertice visis 

 lateribus concavis, angulis rotundo-truncatis et subproductis. Long. 

 sine spin. 30 /x, cum spin. 42 /a; lat. (cum spin, brcv.) 27 /x ; lat. 

 isthm. 9"5 /x. 



Huilla. Lopollo ; Febr. 1860. No. 192. 



N 2 



