\ 
54 DR. б. 8. WEST ON THE ALGÆ OF 
apical warts on any individual semicell may be six or seven. The margins of 
the semicells are undalate from base to apex, the undulations, which are 10 
or ll in number, becoming gradually less distinct towards the apex. The 
lower half of each semicell is approximately cylindrical, but the upper half is 
distinctly attenuated. Specimens of P. mamillatum are frequently found 
attached by their apices in pairs, separation of the cells not following imme- 
diately after division. 
14. PLEUROTÆNIUM ovatum, JVordst. in Ofvers. af К. Vet.-Akad. Hoch, 
no. 3 (1877), p. 18.—Docidium ovatum, Nordst., 1810. 
Var. rumipum, Maskell, in Trans. N. Zeal. Instit. xxi. (1889) p. 29, +. 6. 
fig. 54.—? Docidium rotundatum, W. В. Turner, in. К. Sv. Vet.- Akad. Handl. 
xxv. no. 5 (1893), p. 37, t. 7. fig. 2a. 
Forma marginibus lateralibus superioribus semicellularum leviter concavis 
(—.Docidium pyriforme, W. B. Turner, l. с. t. 7. fig. 3) ; tuberculis apicalibus 
magnitudinis variabilis 6-9; membrana laterum inferiorum incrassata. 
Long. 241-262 ш; lat. max. 94-100 p ; lat. ар. 35-40 д. 
Паб. Yan Yean Reservoir, at the weedy margins (Nov. and Dec. 1905). 
The form seen differs from that described by Maskell from New Zealand 
in the retuseness of the upper parts of the lateral margins of the semicells. 
Almost exactly the same form was observed from Cheltenham, Victoria : 
long. 240-255 u ; lat. max. 89-98 ш; lat. apic. 29:5-32:5 ш. From the latter 
locality one zygospore was found (consult Hardy in Victorian Naturalist, xxiii. 
(1906) p. 21). It was subglobose, externally smooth, and the wall consisted 
of three distinct coats, each of which was lamellose. The middle and inner 
coats had shrunk away from the outer one, especially at one side, and the 
middle coat was papillate, the papillæ being sparsely scattered, blunt, and 
2-2°7 ш in length. Diam. zygosp. 96-108 u. (РІ. 6. fig. 9.) Fora zygo- 
spore to possess a papillate middle coat is a most unusual occurrence. 
Genus TRIPLOCERAS, Вай. 
15. TRIPLOCERAS GRACILE, Bail, in Smithson. Contrib. ii. (1851) р. 38, t. 1. 
fig. 10 [figure poor] ; Wittr. in Nov. Act. reg. Soc. Sci. Upsala, vii. (1869) 
р. 21, t. 1. fig. 10 [figures not good].—T. gracile, forma, W. & G. S. West, 
in Trans. Linn, Soc. ser. 2, Bot. v. (1896) p. 236, t. 13. figs. 9-13. [Etiam 
inclus. T. gracile forma elongata, T. gracile f. gracillima, T. gracile f. quadri- 
loba, et T. gracile subsp. bilobatum, W. В. Turner, т К. Sv. Vet.-Akad. 
Handl. xxv. no. 5 (1893), pp. 25, 26, t. 2. figs. 1-4.] 
Turner’s statement (l. с. p. 26) that “ Triploceras gracile is perhaps the 
most polymorphie species known" is singularly near the mark, but whatever 
virtue the statement possessed he at once destroyed by naming four forms of 
this most variable species on characters which are not only trivial, but which 
