178 welwitsch's African freshwater alg.e. 



The nearest species to this is S. subtrifurcatiim West & G. S. 

 West (in Trans. Linn. Soc. 2ud ser. v. 258-9, t. xvi. f. 24 (1896) ), 

 from which it is distinguished by the three diverging and somewhat 

 shorter spines at each angle being situated in a vertical plane, and 

 in the pentagonal vertical view with acute angles. 



7. S. pentateuchophorum, sp. n. (tab. 369, fig. 6). S. medi- 

 ocre, circiter l|-plo longius quam latins (sine spinis), profunde 

 constrictnm, sinu aperto et subrectangulari ; semicellulje elliptico- 

 oblongte, apicibus leviter convexis, lateribus sursum convergentibus, 

 spina valida convergente ad angnlum inferiorem iinumquemque, 

 spina valida suberecta incurvata ad angulum superiorem uuum- 

 quemque instructa, etiam spinis 3-4 inter spinas majores irregu- 

 lariter dispositis ; a vertice visa3 pentagonft", lateribi;s profunde 

 concavis, spinis 5-6 ad angulos late rotundatos. Long, sine spin. 

 36'5 iJL, cum spin. 63 /x; lat. sine spin. 27-31 /x, cum spin. 46-49 /^ ; 

 lat. isthm. 15 jj.. 



Huilla. Freq. in paludibus exsiccandis ; April 1860. No. 176. 

 Etiam freq. inter Utriculariam, Morro de Lopollo; April 1860. 

 No. 179. 



This species is somewhat allied to S. trUlcns-Neptuni, but is very 

 distinct from it. 



8. S. heteroplophorum, sp. n. (tab. 369, fig. 8). S. mediocre, 

 l^-plo latins quam longius (sine spinis), profunde constrictum, sinu 

 aperto acutangulo ; semicellulie transverse oblongcT, ventro inflato, 

 apicibus pa3ne rectis (subconcavis), lateribus subrectis apicibus 

 versus convergentibus, spina valida acuta convergente ad angulum 

 inferiorem unumquemque, spina valida suberecta (subdivergenti) 

 acuta ad angulum superiorem unumquemque, etiam cum spinis 

 paucis niulte minoribus circa spinas majores subirregulariter dis- 

 positis ; a vertice visjB triangulares, lateribus concavis et angulis 

 obtuse rotundatis, spinis majoribus duabus ad angulos verticaliter 

 dispositis, spinis minoribus circa angulos ; membrana glabra. Long, 

 sine spin. 19 /x, cum spin. 36-37 /x ; lat. sine spin. 23-25 /x, cum 

 spin. 33-40 /x ; lat. isthm. 10-5 /x. 



Huilla. Freq. in paludibus exsiccandis ; April 1860. No. 176. 

 Etiam inter Utriculariam, Morro de Lopollo ; April 1860. No. 179. 



The arrangement of the spines on the much narrower angles (as 

 seen in vertical view) easily distinguishes this species from .S. Hi/stri.v 

 Ealfs. At each angle there are two large spines in a vertical plane, 

 and about six much smaller ones round them ; the latter are some- 

 times regularly disposed in a circle round the two larger ones. 



Var. latum (tab. 369, fig. 9). Var. cellulis latioribus, sinu 

 minus aperto ; semicellulis angulis leviter subcapitatis et apicibus 

 convexis, spinis parvis 6 multe reductis et in annulo circa spinis 

 majoribus duabus ordinatis. Long, sine spin. 17 /x, cum spin. 

 26 /x ; lat. sine spin. 23 /x, cum spin. 28 /x ; lat. isthm. 6 /x. 



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



9. S. Pseudohystrix, sp. n. (tab. 369, fig. 10). S. parvum, 

 tam longum quam latum (sine spinis), profunde constrictum, sinu 

 aperto acutangulo ; semicellula^ transverse rectangulari-oblongfe. 



