THE VICTORIAN NATURALIST. 21 



sometimes long, narrowly linear, with the inner extremity 

 widely dilated ; semi-cells elliptic-hexagonal or trapeziform, 

 angles rounded, upper oblique margins slightly concave or sub- 

 straight, apex truncate or slightly convex. Side view of semi-cells 

 depressed-spherical, vertical view broadly elliptic, with the lateral 

 margins towards the poles very slightly concave. Cell wall 

 furnished with a very dense covering of pearly granules, which 

 are somewhat more prominent at the lateral angles ; granules in 

 the centre of the semi-cell slightly larger and flattened, with small 

 intervening scrobiculations, and in the middle of the apex 

 considerably reduced in size. 



Length, 85-106 fj. ; breadth, 82.5-92 /i ; breadth of isthmus, 

 19-32 fx ; thickness, 61.5-64 jj,. 



Habitat. — Cheltenham, 26th June, 1905. Lagoons of the 

 Yarra Yarra River, March, 1905. 



This species is, perhaps, more closely related to C. biretum, 

 Breb., than to any other. It approaches it in the denseness of its 

 granulations, in the elevated apices of its semi-cells, and in the 

 tumid vertical view. It differs from that species, however, in the 

 pronounced lateral angles and in the inequality of its granulation. 

 The median inflated part of the semi-cells is much greater than 

 in C. biretum, and in this region there are small scrobiculations 

 between the granules. 



C. biretiforme is very variable in the outline of the semi-cells. 

 The most abundant form seen possessed elliptic-hexagonal semi- 

 cells and a short, widely dilated sinus ; but another common 

 form had more trapeziform semi-cells, with less pronounced 

 lateral angles, and the sinuc was much longer. Between these 

 extreme forms were many other gradations. 



Pleurot^nium ovatum, Nordst. ; var. tumidum. Mask. 



Length, 240-255 fx ; breadth (max.), 89-98 ^ ; breadth of 

 apices, 29.5-32.5 p ; diameter zygospore, 96-108 fj.. 



Habitat.— Cheltenham, Victoria, 26th June, 1905. 



The specimens were remarkable for the prommence of the 

 apical teeth, which were conical, blunt, and 8 or 9 in number. 



One zygospore was observed. It was sub-globose, with a smooth 

 exterior. There were three distinct coats each of which was 

 lamellose, and the median coat had shrunk away from the outer 

 one (especially at one side). This median coat was papillate, 

 the papillce being sparsely scattered, blunt, and 2-2.7 i" length. 



MoNOSTROMA EXPANSA, G. S. West (sp. n.) 



Thallus membranaceous, broadly expanded, and slippery, 

 somewhat folded (or plicated) towards the margins, which are 

 generally slightly torn; cells more or less rounded or rounded- 

 polygonal, crowded, in a vertical transverse section of the 

 thallus elliptic-sublunate ; chloroplasts parietal, solitary, with a 

 single pyrenoid. 



