128 BRITISH DESMIDIACEJ2. 



Length 40-44 ^ ; breadth of base of semicells 18*5- 

 22 /x,, of apex 20-25 /x; breadth of isthmus 14-16*5 p.. 



ENGLAND.- -Bog near Widdale Beck, N. Yorks ! Scaw- 

 fell, Cumberland ! Bovey Tracey, Devonshire (Joshua). 



WALES. Capel Curig, and at 2200 feet on G-lyder 

 Each, Carnarvonshire ! Dolgelly, Merioneth ! 



SCOTLAND.- -Ross, Aberdeen, Kincardine, Perth, 

 Argyll; zygospores from Den of Garrol, Kincardine 

 (Roy $ Bissett). Glen Nevis and Invermoidart, Inver- 

 ness ! Near Lerwick, Shetlands ! 



IRELAND.- -Dublin and Wicklow (Archer). Bally - 

 nahinch !, and Leenane (Archer), Gralway. 



Geogr. Distribution.- -France. Germany. Austria 

 (Bohemia). Bulgaria. Brazil. 



St. pileolatum is distinguished from St. Capitnlum by two 

 main features ; first, the upwardly directed apical angles of 

 the semicells, resulting in. a markedly concave apex, and 

 secondly, the greater number of verrucas encircling the base 

 of the semicells. The granulation is also a little different, as 



*, - * 



the granules are never sharp and spine-like in St. pileolatum. 



The verruca3 at the base of the semicell are variable 

 in character, but the most frequent form possesses longi- 

 tudinally compressed and slightly emarginate verrucas, which 

 might almost be described as short emarginate ridges 

 (consult PI. CXVIII, figs. 11 and 12). Sometimes the verrucas 

 are not so compressed and are furnished with blunt teeth at 

 their angles, in which case they much resemble those of 

 St. Capitulum (consult fig. 13). 



Brebisson's figure of this species (in Ralfs' ' Brit. Desm/ 

 1848, t. 35, f. 22) is very inaccurate as to detail, but the out- 

 line and general proportions are not bad. The granulation 

 as depicted at the base of the semicell is an obvious error. 



In addition to the type form of St. pileolatum there are 

 two others which are sufficiently distinct to merit definite 

 varietal names. These are : 



Var. CRISTATUM Liitkem. For description see below. 



Var. BiiASiLiENSE (Borg.) Liitkem. Desm. Attersees, 1893, 

 p. 567. St. amoenum Hilse var. brasiliense Borg. Desm. 

 Brasil. 1890, p. 45, t. 4. f. 44. Basal verrucas of semicells 

 larger and fewer in number (about 13), each surmounted by 

 5 or 6 minute, irregularly disposed denticulations. Long. 

 45 ji ; lat. 19 u; lat. isthm. 12 u. Hob. Brazil. We had 



