198 MESSRS. W. WEST AND G. S. WEST ON 
The name “spirale” could not be adopted for the variety because there is already a 
well-marked var. spirale of this species (cf. West & G. S. West, in Journ. Bot. 
xxxvi. 1898, p. 335). 
In var. Turnerii several cells occur in a colony, and are strongly twisted together in 
their central portions. 
300. RHAPHIDIUM  LONGISSIMUM, Schröder, in Bericht. Deutsch. Botan. Gesellsch. 
1897, xv. p. 973, t. 17. fig. A Closteriopsis longissima, Lemmermann, in Plóner 
Forschungsberichten, t. 7. 1899, p. 29, t. 2. figs. 836-88. Closterium pronum, Bréb., 
var. longissimum, Lemm. (sec. Lemmermann). 
Var. TROPICUM, var. n. Var. polis acutissimis sed non setiformibus. 
Long. 225-288 u; lat. 6-7:5 y. 
Hab. Paddyfields, Heneratgodha. 
We have already shown that Closteriopsis longissima, Lemm., was most probably a 
form of Rhaphidium longissimum, Schroder (cf. Journ. Bot. xxxviii. 1900, p. 298), and 
after examining these specimens from Ceylon we feel convinced that the two are 
identical. Moreover, we are also certain that they belong to the genus Rhaphidium. 
DESMATRACTUM, gen. n. 
Cellule minutz, libere natantes, semper solitarize, late fusiformes vel ellipticee cum 
apicibus longe acuminatis, ad medium subito sed minute constrictze. Chromato- 
phora pyrenoide singulo preedita. : 
301. DESMATRACTUM PLICATUM, sp. unica. (Pl. 17. figs. 14, 15.) Cellule longitudinaliter 
costatz (costis 8), a vertice vise circulares cum nodulis acutis 8 in ambitu. 
Long. cell. 16-17:3 4; lat. cell. 65-7 »; lat. constrict. 5°3-5'8 u. 
Hab. Paddyfields, Heneratgodha. 
This genus most nearly approaches Rhaphidiwm, but is principally distinguished by 
the form of the cell and by the central constriction, which extends equally all round the 
median part of the cell. 
Genus TETRAEDRON, Kuetz. 
302. TETRAÉDRON CRUCIATUM, nob. Micrasterias cruciata, G. C. Wallich, in Ann. A 
Mag. Nat. Hist. ser. 3, v. p. 281, t. 13. fig. 12. Staurophanum. cruciatum, W. B. 
Turn. in K. Sv. Vet.-Akad. Handl. xxv. 1893, no. 5, p. 159, t. 20. figs. 20, 21. 
Diam. 37-40 u. 
Hab. In artificial tank, Peradeniya. 
303. TETRAÉDRON CAUDATUM, Hansg. in Hedwigia, xxvii. 1888, p. 181. Astericiwm 
caudatum, Corda, 1839. Polyedriwm pentagonum, Reinsch. 
Forma 1ncisum, Reinsch. 
— Hab. Pond, Royal Botanical Gardens, Peradeniya. 
