STAURASTRUM. 115 



cells subcimeate or cup-shaped, broadening towards the 

 apex, which is slightly convex and provided with a row 

 of emarginate or irregular verruca ; upper angles pro- 

 duced to form tapering processes tipped with 3 minute 

 spines, and covered with several series of denticulations 

 which are sometimes continued over the body of the 

 semicell itself, processes slightly converging or nearly 

 horizontal. Vertical view usually triangular, sides 

 straight, or very slightly convex, angles produced to form 

 processes with slightly undulating margins, with a series 

 of emarginate verrucae just within each lateral margin. 



Zygospore unknown. 



Length 42-57^; breadth, including processes, 55- 

 100'S (I ; breadth of isthmus 9-13 p. 



ENGLAND.- -Plankton of Ennerdale Water, Cumber- 

 land! and Malham Tarn, W.Yorks! Plankton of Brace- 

 bridge Pool, and Windmill Pool, Shirley, Warwickshire ! 



SCOTLAND. Plankton of Lochs Sandy, Trebister, 

 Beosetter and Bressay, Shetlands ! 



IRELAND.- -Xear Lough Magrath, Donegal ! Plankton 

 of Lough Accorymore, Achill Isle, Mayo ! Ballynahinch, 



Gal way ! 



Geoc/r. Distribution- -France. Galicia and Austria. 

 Italy. Norway. Siberia. Central China. India. Australia. 



In the originally described Italian specimens the apical verrucas 

 were very much more irregular in size and form than in the 

 British examples, and near the origin of each process there was 

 a longer conspicuous spinous verruca. In the British specimens 

 the verrucse are all more or less of the same size, and form quite 

 a regular series. There is a further difference in the British 

 examples in the presence of delicate granules, either in scattered 

 groups, or forming a circular band round the base of the semicelL 



The species is not infrequent in plankton gatherings. 



Var. annulatum W. & G. S. West. (PL CXLVIII, 



% 3.) 



St. Manfeldtii var. annulatum West & G. S. West, Alg. N. Ireland, 1902, 

 p. 56, t. 1, f. 30, 31. 



Processes slightly narrower than in the type ; apical 



