180 MR. С. S. WEST ON THE FRESHWATER АТСА 
The following diagnosis takes into consideration the limits of variation for the species :— 
Trichomata robusta et solitaria, inter algas varias sparsas, curta, in spiram laxam vel 
laxiusculam plus minusve subregulariter diametro 8:8-16 р contorta ; anfractibus 95-11 н 
inter ве distantibus ; apicibus trichomatis obtusis vel rotundato-obtusis; cytoplasmate 
ierugineo-eceruleo et homogeneo, cum granulis minutis sparsis. Crass. trich. 8-5 p. 
Geogr. distribution.—Central Africa ; Ceylon; Java. 
Family RIVULARIACEZ. 
Genus CALOTHRIX, 49. 
334. CALOTHRIX JULIANA, (Menegh.) Born.  Flah. in Ann. Sci. Nat. 
1° sér., Bot. iii. (1886) p. 348. 
Crass. fil. 10-12 р (ad 16 p); crass. trich. ad Баз. 7-93 д. 
Nyasa.—In scrapings from bottom of s.s. * Guendolen at anchor 8. end of 
lake (15 June, 1904 ; no. 577). 
335. CALOTHRIX EPIPHYTICA, W. & С. S. West, in Journ. Dot. xxxv. 
(1897) p. 240. 
Crass. fil. ad bas. 4°5-9 ш; crass. trich. ad bas. 2°8-5°8 д. 
Nyasa.—On Cladophora, Anchorage Bay (no. 11). 
Tanganyika.—On Cladophora scraped from the bottom of Dr. Cunnington's 
dau (24 Jan. 1905 ; no. 216). 
336. CALOTHRIX BREVISSIMA, sp. п. (PI. 10. fig. 8.) 
C. filis minutis et epiphyticis, culmis vetustis pelagiis affixis, gregariis et 
brevissimis, longitudine toto 53-94 д, non vel levissime attenuatis ; vagina 
firma, arcta, репе cylindrica, tenui, hyalina et achroa ; trichomatibus pallide 
olivaceo-viridibus, brevissimis, longitudine toto 80—62 u, vix attenuatis, apice 
rotundato ; cellulis inferioribus diametro subzequilongis vel brevioribus, 
superioribus diametro duplo brevioribus, minute granulatis ; heterocystis 
basilaribus singulis (rare binis) rotundato-hemispheericis vel subglobosis. 
Crass. fil. 5—7 ш; crass. trich. 3°8-5 p. 
Victoria Nyanza.—In the plankton, attached to decaying shreds of vegetable 
matter (probably old leaves and plant-stems), near Bukoba (21 Apr. 1906 ; 
no. 252). 
This minute species occurred clustered round fragments of decaying stems 
and leaves which had collected in the tow-net. It is characterized by its 
extreme shortness, and is distinguished from all other species of the genus by 
the absence of any appreciable attenuation. The sheaths are firm and 
eolourless, almost cylindrical, with open extremities, and they fit the trichomes 
very closely. The trichomes are rounded at both extremities, with the 
faintest, indication of attenuation towards the apex, and the cells are much 
shorter than their length. There is a well-defined basal heteroeyst of a 
