THE FRESHWATER ALGJE OF CEYLON, 143 
annulis 5-7 impressionum irregularium subquadrangularium vel subrectangularium 
(nunquam in series longitudinaliter dispositis), in parte superiore semicellularum 
impressionibus confluentibus et multe irregularibus, annulo basali impressionum 
irregulari et confluente; impressiones partes tenuissimæ membrane sunt (ut in 
Pleurotenio trochisco). 
Long. 259-276 u; lat. ad bas. semicell. 38-54 4; lat. ad apic. semicell. 97-344 ; lat. 
max. 61-71 u. 
Hab. Paddyfields, Heneratgodha.  Paddyfield between Kosgoda and Urahaighasma- 
hendai. 
This Pleurotenium is of the same nature as P. trochiscum, possessing a number of 
somewhat irregularly quadrate or rectangular pits arranged in transverse rings. The 
ring at the base of each semicell consists of much smaller and more irregular pits which 
are confluent round the base. The rings towards the apex are also confluent, forming 
elongated longitudinally placed pits of a very irregular outline, often confluent round the 
apex. The pitted marks of this species exhibit no trace of a longitudinal arrangement, 
but are disposed more after the manner of the bricks or stones in a wall. The arrange- 
ment of the pits and the greatly inflated semicells, which are entirely destitute of a basal 
inflation, readily distinguish this species. 
91 PLEUROTJ.ENIUM PARALLELUM, West & G. S. West, in Trans. Linn. Soc., ser. 2, Bot. 
vol. v. 1895, p. 46, t. 5. fig. 34. 
Long. 695 4; lat. ad bas. semicell. 4T n; lat. ad NUM semicell. 46:5 y. 
Hab. Paddyfields, Heneratzodha. 
92. PLEUROTJENIUM PERLONGUM, sp. n. (Pl. 19. figs. 1, 2.) P. mediocre, elongatum ; 
cellulis concatenatis, diametro | 28-36-plo longioribus; semicellule cylindrice, 
inflatione prominenti ad basin et undulis circiter 3 supra basin, lateribus parallelis, 
apicibus leviter dilatatis, tuberculis longitudinaliter ellipticis parvis 30-32 (visis 
16-17) instructis. 
Long. 463-590 « ; lat. ad bas. semicell. 19°5-21 4; lat. ad med. semicell. 14:5-15:5 u ; 
lat. ad apic. 20-21:5 D. 
Hab. Paddyfields, Heneratgodha. 
The extraordinary length of this species, together with the character of the base of the 
semicells and the dilated apices, are sufficiently characteristic. There are also more 
tubercles in the apical ring than is generally the case in narrow species of this class of 
Pleurotenia. The cells are usually somewhat curved, and are joined together in 
filaments, the tuberculated apex of one cell being closely applied to the tuberculated apex 
of the next. 
93. PLEUROTZENIUM ELATUM, Borge, in Bih. till K. Sv. Vet.-Akad. Handl. xxiv. 1899, 
Afd. 3, no. 12, p. 16. Docidium elatum, W. B. Turn. in K. Sy. Vet.-Akad. Handl. 
xxv. 1898, no. 5, p. 27, t. 2. fig. 16. Docidium robustum, W. B. Turn. 1. c. y. 27, 
t 2. ig. 8. 
