430 MR. В. M. GRIFFITHS ON THE AUGUST HELEOPLANKTON 
Dang., from Warwickshire, Surrey, Essex, and Devonshire ; Р. Takedana, 
G. 5. West, from Warwickshire and Surrey ; and P. Chodati, Lemm., from 
Great Barr Park, Staffordshire *. In addition, there is а new species, 
Pteromonas ovalis, from Spring Grove. 
3. PrEROMONAS OVALIS, sp. nov. (РІ. 34. fig. 6.) 
Cellula ovalis, cum divertieulo parvo cupuliformi in fine posteriori axiali у 
membrana cellulæ in alam ovalem expansa ; chromatophora subeampanulata 
cum pyrenoidibus duobus. Long. cell. 20:5 и, lat. cell. 19 д. 
Hab. Associated with Pt. aculeata in Spring Grove Lower Pool, Wribben- 
hall, Worcestershire, but in very small numbers. 
This species resembles Pt. angulosa (Carter), Dangeard, but differs from it 
in that the cell-cavity is not pyriform, but is oval with a small cupuliform 
diverticulum at the posterior axial extremity. The wing is a complete oval, 
without the prominent anterior angles of 7t. angulosa. 
4. SCENEDESMUS RACIBORSKI, Woloszynska in Hedwigia, lv. (1914) 
p. 109, t. 7. ff. 1, Г, & 2. (PI. 34. figs. 7 & 8.) 
Length of cell 10 д, breadth 3-5 м. 
This organism occurred in fair numbers in Wilden Pool. А colony 
consists of four cells, which are placed so that the longer transverse axes of 
the cells are arranged radially. When viewed along the longitudinal axis, 
the cells occupy about one-third of a circle. This species differs from 
all other species of Scenedesmus in this radial arrangement of the cells of the 
colony. Daughter-colonies of four cells remain for some time attached to 
the mother-colony. In this respect it resembles Dimorphococcus, but differs 
from that genus in the shape of the individual cells and in the very regular 
form of the colony. 
5. Oocysris PARVA, W.& G.S. West, in Journ. Bot. xxxvi. (1898) р. 335 ; 
G. S. West, L c. xxxvii. (1899) t. 394. ff. 14-17. (Pl. 34. figs. 9 & 10.) 
Length of cell 11 р, breadth 6 y. 
This is the smallest species of Oocystis. It occurred in small numbers in 
Spring Grove Upper Pool. The cells are embedded in a thick mucous 
envelope, and form small colonies of a few cells. It is a species of rare 
occurrence, 
Û. LAGERHEIMIA sp. (PI. 84. figs. 11 & 12.) 
Cellulze ellipsoideæ spinis brevibus subeurvatis 3-4 ad polum unumquemque. 
Length of cell 12 u, breadth 5 p. 
This alga was found in Spring Grove Upper Pool in some quantity, 
Mother-cells with four autospores were frequent. The organism does not 
entirely agree with any described species. 
* Consult С. S. West, “ Algological Notes.-—X.-XIIL," Journ, Bot. 1. (1912) p. 330. 
