Acta Societatis pro Fauna et Flora Fennica, 49, N:o 7. 49 



Semicellulae conspicue sexangulatae. Spinae omnes 

 geminatae (numquam singulae), apicales valde sursum, ba- 

 sales valde deorsum inclinatae, longae tenues graciliter cur- 

 vatae. Membrana in area centrali papilla (seu protuberantia) 

 depressa, parva, glabra, circa earn circulo simplici scrobi- 

 cularum ornata. Cum spin. long. 70—80—76, lat. 76—84— 

 88, sine spin. long. 57— 51- X, lat. 51— 48— X, crass. 32, 

 isthm. 15—19—21, long, spinae 15—19 /(. [N:o 734, 927]. 



This variety is easily recognized by the markedly 

 6-angulate semicells, the long, slender and gracefully curved, 

 always paired spines, the apical ones being directed obli- 

 quely upwards forming an angle of 90° with the upper 

 lateral sides, the basal ones downwards (continuing the di- 

 rection of the upper lateral sides).*) The central area is 

 not thickened but possesses a slight smooth papilla sur- 

 rounded by a simple ring of scrobiculations. 



Very nearly related to this variety seems to be X. 

 controversum var. planctonicum West, Mngr. IV pi. 107 f. 

 7 — 8, which in my opinion would perhaps better be trans- 

 ferred to X. antilopaeum. In a monstrous semicell of var. 

 ornatum there was a short accessory spine just above the 

 normal basal spines. 



Mab. Keuru (C); near Tammerfors (W). PI. 4 fig. 

 30—31. 



Fully agreeing with West (Mngr. IV page 66) I do 

 not think it possible to separate var. fasciculoides L ii t k e m. 

 (Desm. Attersees, 1893 page 547) as a distinct variety. 

 Consequently it is here omitted. 



The remaining forms of X. antilopaeum, which do not 



belong to the varieties mentioned above, have not been 



recorded from Finland. They may be enumerated here as 



follows: 



X. antilop. forma Nordst, Alg. Brasil. (1877) p. 26 fig. xyl. 5. - 

 forma Nordst., ibid. p. 27 fig. xyl. 6. [Would perhaps better be 

 transferred to X. hastiferum). — var. canadense Josh., New rare Desm. 



*) The same arrangement of spines is sometimes met with invar. 

 polymazum and var. minneapoliense! 



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