OF SOME NORTH WORCESTERSHIRE POOLS. 431 
7. CRUCIGENIA APICULATA (Lemm.), Schmidle in Allgemeine bot. Zeitschr. 
vi. (1900) р. 234. Staurogenia apiculata, Тешип. in Bot. Centralbl. Bd. Ixxvi. 
(1898) р. 151; in Pliner Forschungsberichten, vii. (1899) t. 1. f. 14. 
(Pl. 34. fig. 13.) 
Length of cell 6 y, breadth 4 y : length of colony 15 р, breadth 11 y. 
A single specimen of this very rare alga was found in a collection from 
Wilden Pool. Each colony consists of four cells. Each cell of the colony 
possesses one short broad-based spine, situated on the margin of the free 
edge of the cell, near to, and slightly inclined towards, the median plane of 
the colony. The organism has not been previously recorded for the British 
Isles. 
8. CRUCIGENIA RENIFORMIS, sp. nov. (Pl. 34. fig. 14.) 
C. coloniis e cellulis 16 formatis; cellula singula coloniæ reniformi ; 
chromatophora eum pyrenoide singulo. Long. cell. 68 и, lat. cell. 4 р. 
Hab. Wilden Pool, Stourport, Worcestershire. 
Each colony consists of sixteen cells held together by a rather large amount 
of mucilage. In the centre of each group of four cells is a small quadrate 
space, and a large quadrate space lies in the centre of each complete colony 
of sixteen cells. Each individual cell is reniform in shape, with the exterior 
curvature lying towards the centre of each quarter-colony of four cells. 
There is one pyrenoid in each cell. The species resembles C. triangularis, 
Chodat, but differs from it in having reniform cells. 
9. TETRASTRUM STAUROGENLEFORME (Schrüd.), Chodat, Algues vertes de la 
Suisse, 1902, p. 208. (РІ. 34. fig. 15.) 
Length of cell 4y ; length of colony 9 p. 
Small numbers were found in Spring Grove Upper Pool, associated with 
Pediastrum, Scenedesmus, and Lagerheimia. Each cell of the four-celled 
colony is ornamented with four or five spines, situated on the outer margin 
of the cell. The alga is of very rare occurrence, and is easily overlooked. 
10. GEMINELLA INTERRUPTA, Turpin, in Mém. Mus. Hist. Nat. xvi. (1828) 
p. 329, t. 13. f. 24. 
Considerable quantities of this alga occurred in Island Pool. The cells 
tend to lie in pairs in the filament, but every gradation was observed between 
paired cells and cells evenly spaced. The filament is invested with a thick 
mucous coat. This alga is of rare occurrence in the British Isles. 
11. CERATIUM HiRUNDINELLA (О. Е. Müller), Schrank, Briefe nat. phys. 
ikon. Inhalts, 1802, р. 375. 
Two forms of this very variable species were found. One occurred in 
Stanklin Pool. It had three antapical horns well developed and widely 
divaricated (Pl. 34. fig. 16). The second form was seen in Spring Grove 
Lower Pool. It had two antapical horns well developed, but not widely 
