The Freshwater Algae of Africa. 



559 



eentricis ordinatis; a vertiee visis ellipticis, polis late rotundatis, 

 inflatione mediana distincta subacuta. Long., 50 60 p.; lat., 43-50 p ; 

 lal . isthm., 12-1 5 /'. 



Samples •_' 1, i2 * > . 



This variety shows considerable resemblance t«> C. pearsoni, <i. S. 

 West ( Freshw. Alg. Percy Sladen Mem. Exped., Aim. S. A IV. Museum, 

 ix, 1912, p. 87, PI. I. fig. 12), and the name is intended to bring oul 

 tliis fact. Tl differs from iliis species (a) in the end-view, which is 

 practical!} thai typical for C '. mbbroomei ; (b) in the somewhal coarser 

 granulation; and (c) in the fad that the granules are arranged in 

 obvious concentric series. Moreover the individuals are smaller. The 



Pig. 30. -Cosmariwm subbroomei, Schmidle, var. pseudo-pearsoni, nov. var. 



x Too. 



variety may also be compared with C. botrytis, Menegh., C. radiosum, 

 Wblle, and C. intermedium, Delp, 



Genus XANTHIDIUM Ehrenberg. 



1. Xanthidium brevispinum, n. sp. (Pig. 31.) 



X. subparvum, ca. tarn longum quam latum, profunde constrictum, 

 sinu angusto-lineari, extremo vix ampliato. Semicellulae late trapezi- 

 formes, angulis inferioribus late rotundatis, angulis superioribus acutis 

 (utrisque serie spinarum 3 instructis) ; lateribus convexis con- 

 vergentibus, superne fere rectis vel interdum concavis (serie spinarum 

 3 vel plurium ad angulum lateralem instructis) ; apicibus truncatis 

 rectis; semicellulis intra angulum basalem spinis parvis 3 5 et intra 

 apicem spinis parvis diverse dispositis (plerumque in medio et intra 

 angulum superiorem utrumque) instructis; prope media semicellula 

 area diverse scrobiculata. A vertice visae subrhomboideae, polis latis 

 rotundatis seriebus tribus spinarum 3 instructis, ad medium utrobique 

 valde incrassatae spina bifurcata munitae ; a latere visae r 



Long., 42 p ; lat. max. sine acul., 42/' ; lat. apic, 27 p ; lat. isthm., 

 12 p; crass., 23 p. 



Sample 7 (very rare). 



