228 BRITISH DESMIDIACEJE. 



Austria. Hungary. Norway. Sweden. Denmark. K".. 

 and S. Russia. Greenland. New Zealand (var.). United 

 States. 



Several investigators have noticed that this tiny species some- 

 times occurs attached to filamentous alga?, or to the leaves 

 of mosses, by means of a very short gelatinous basal stalk. 

 It is the only species of the genus in which this is known to- 

 occur, and even here the filaments are so fragile and break 

 away so easily from the basal attachment that it is usually 

 observed in a free floating condition. The cells are all alike, 

 and there is no distinction in their form, whether they are 

 near the base or the apex of the filament. It seems to occur 

 more abundantly in Ireland than in any other part of the 

 British Isles. 



Var. pyramidatum West. (PL CLXI, figs. 4, 5.) 



82)- pulclidlum var. pyramidatum West & G. S. West, New Brit. Ate. 1893,, 

 p. 3, f. 8 ; Alga-fl. Yorks. 1902, p. 95. 



Semicells more definitely pyramidate than in the 

 type, sides nearly straight, apex broadly truncate ; 

 isthmus narrower than in the type. 



Length 10-11 [I ; breadth 8'6-9'6pi ; thickness 4'Sp ; 

 breadth of apex 5*8-5*9 ^ ; breadth of isthmus 2-2*6 {A. 



ENGLAND.- -Eiccall Common, E. Yorks. 



SPECIES TO BE ENQUIRED INTO. 



SPONDYLOSIUM ARMILLATUM Turn. ' Desm. Notes,' 1893, p. 346, 

 f. 20. A still smaller plant (than Spondylosium monile Turn. 

 = SP- pygwi&nm, var. monile (Turn.) West), biscoctiform, 

 centre gently incavate in front view ; side view compressed. 

 Length 6 (JL ; breadth 3*7 /u ; thickness 2'5 p Trelleck Common, 

 Monmouth, Wales. 



Genus 24. HYALOTHECA Ehrenb. 1840. 



Ehrenb. in Berlin. Monats. 1840, p. 212. 

 Kiitz. Phyc. Germ. 1845, p. 140. 

 Ralfs, Brit. Desm. 1848, p. 51. 

 Kiitz. Spec. Alg. 1849, p. 187. 

 De Bary, Conj. 1858, p. 76. 



