HYALOTHECA. 237 



SCOTLAND. Birsemore Loch, Aberdeen (Roy & 

 Biss.}. 



Geogr. Distribution . Ceylon. 



3. Hyalotheca Indica Turn. 

 (PL CLXII, fig. 10.) 



Hyalotheca Indica Turn. Freshw. Alg. E. India. 1893, p. 152, t. 22, f. 17" 

 (not t. 19, f. 18, which is H. dissiliens var. hirnis); West & G. 8. West, 

 Alg. Ceylon, 1902. p. 195; Further Contrib. Plankton Scott. Lochs, 

 1905, p.' 505, t. 6, f. 6. 



Cells small, a little longer than broad, subcylindrical, 

 very slightly broader in the middle than at the ends, 

 with a small but acute median incision ; apex of semi- 

 cell broad and truncate ; filaments not conspicuously 

 excavated at the joints ; in vertical view circular ;; 

 chloroplasts axile, one in each semicell, each with a 

 central pyrenoid. Filaments enclosed in a gelatinous 

 sheath. 



Zygospore unknown. 



Length 10-15*5 IJL ; breadth 9-12 \L ; breadth of apices 

 7'o-10fJL ; breadth of isthmus 8-10 IL. 



ENGLAND.- -Plankton of Easedale Tarn, Westmore- 

 land ! 



SCOTLAND.- -Plankton of Loch Fadaghoda, Lewis, 

 Outer Hebrides ! 



IRELAND.- -Plankton of small lakes, Clifden to Round- 

 stone, Galway ! 



Geogr. Distribution.- -India. Ceylon. Java (var.). 



This species bears a superficial resemblance to some forms of 

 H. dissiliens. From var. hians Wolle of that species it is dis- 

 tinguished by the relatively broader apices of its cells, the fila- 

 ments not being so conspicuously excavated at the joints, whilst 

 from H. dissiliens var. tatrica Racib. it is distinguished by its 

 smaller size, and by the different form of its constriction, which, 

 even though very slight, is more abrupt than in that species. 

 The British examples are somewhat larger than those from India 

 and Ceylon. 



