58 DR. С. S. WEST ON THE ALGÆ OF 
This handsome species belongs to that section of the genus including 
Micrasterias americana and M. mahabuleshwarensis, in which the polar lobe is 
furnished with accessory processes. It is at once distinguished from these 
species by the great length and divergence of the lateral lobules and the 
processes of the polar lobe. Accompanying this is a great reduction of the 
two accessory asymmetrical processes of the polar lobe, which are very 
minute, with smooth margins and bidenticulate apices. 
M. Hardyi is one of the most conspicuous constituents of the plankton of 
the Yan Yean Reservoir, and for thirteen months it was never absent from 
the tow-nettings. — It exhibits little variation, and only one abnormal spe- 
cimen was observed among many thousands. In this individual the lateral 
lobes of one semicell were undivided, resembling the lateral lobes of M. tropica 
but much more attenuated. Large numbers of specimens were observed in 
various stages of cell-division, and in the young semicells the lateral lobes 
are always entire and bluntly rounded. The four teeth at the attenuated 
apices of the lobes are not easily all observed, but they were present in every 
specimen examined. 
18. MICRASTERIAS THOMASIANA, Archer, in Journ. Mier. Soc. new ser. ii. 
(1862) p. 239, t. 12. figs. 1-5; И. & G. S. West, Monogr. Brit. Desm. ii. 
(1905) p. 110, t. 51. figs. 3-6. 
Var. PULCHERRIMA, var. п. (Pl. 4. fig. 1.) 
Semicellulæ cum processu brevi bidentato extrorsum eurvato intra basin 
lobuli lateralis uniuseujusque ; dente magno infra incisionem lobi lateralis 
superioris ; processibus lateralibus magnis duobus ad basin semicellularum 
dente magno superiore instructis. 
Long. 219 д; lat. 197 ш; lat. isthm. 30 ш; crass. max. 65 p- 
Hab. Toorourong Reservoir, in the plankton (July 1907). 
This beautiful Desmid was not uncommon in the tow-nettings obtained by 
boat from the Toorourong Reservoir, and was one of the only two Desmids 
present in the collections. It differs in a conspicuous manner from all other 
described forms of M. Thomasiana in the sixteen short, bidentate processes 
disposed one within each lateral lobule. The teeth within the divisions of the 
lateral lobes, 32 in the front view of a single cell, are present exactly as in 
the type, but there is an additional tooth close to the base of each superior 
lateral lobe, and there are some extra ones near the margin of each polar 
lobe. The larger, outwardly curved, lateral processes at the base of each 
semicell also possess an extra dorsal tooth of large size. 
M. Thomasiana is known from the western parts of Europe, from the 
United States, and forms of it from Ceylon, Singapore, and Java. 
