236 BRITISH DESMIDIACE^:. 



wicks! (Witts). Surrey! Sussex (Ralfs). Hants! (Ben- 

 nett). Devon and Cornwall ! (Ralfs). 



WALES.- -Llyn Padarn !, Dolbadarn Castle!, Llyn 

 Idwal!, LlynOgwen! and Capel Curig ! (Cooke & Wills), 

 Carnarvonshire. 



SCOTLAND.- -Inverness !, Aberdeen, Kincardine, Perth ! 

 and Argyle (Roy & Biss.). Sutherland ! Ross ! Lewis 

 and Harris, Outer Hebrides ! Not uncommon in the 

 plankton ! Plankton of Bressay, Shetlands ! 



IRELAND.- -Dungloe and Glenties, Donegal ! Plank- 

 ton of Mavo ! Ouo-hterard, Derrvclare Lough and in 



/ \f 



plankton, Galway ! Muckross, Glen Carragh and in 

 plankton, Kerry ! Carrantuohill, Cork ! Dublin and 

 Wicklow (Arch.). Slieve Donard, Down ! 



Geogr. Distribution.- -France. Germany. Switzerland. 

 Galicia and Austria. Hungary. Italy. Spain. Portugal. 

 Norway. Sweden. Bornholm. Finland. Poland. S. 

 Russia. India. Australia. Central Africa. L T nited States 

 and Alaska. N. W. Canada. Guiana. Brazil. Patagonia. 



This species, although neither so common nor so abundant as 

 H. dissiliens, is fairly generally distributed in the British Isles. 

 It is readily distinguished from the latter species by the entire 

 absence of a constriction, its apical crown of minute granules, 

 and by its usually thicker sheath. 



According to Hauptfleisch, each tiny granule near the apex of 

 the semicell has in its centre the mouth of a jelly-secreting pore, 

 and it is by means of these pores that the broad tough sheath 

 of the filament is produced. The apical surface of each semicell 

 is also provided with similar pores, but the mouths of these are 

 not protruded beyond the general level of the surface in the same 

 way as the lateral ones. 



Var. minor Roy & Biss. (PL CLXII, fig. 5.) 



H. mucosa var. minor Roy & Biss. Scott. Desm. 1893, p. 9 (sep.) ; West 

 & G. S. West, Alg. Ceylon, 1902, p. 195, t, 22, f. 20. 



Cells relatively narrower than in the type ; filaments 

 about half the normal thickness. 



Length 12'5-U'oy. ; breadth 9-12 k u. 



