70 THE VICTORIAN NATURALIST. 



Genus 24. — Spluerozsma, Corda. 



S. excavatum, Ralfs ... Yan Yean (Res., w.) 



S. vertebratum, Ralfs ... H'berg. (lag.); Lake Wendouree, 



Ballarat 



Genus 25. — Onychoneyna, Wallich. 



O. nordstedtiana, Turn. ... H'berg., Wlsm., Alex, (pools) 



Genus 26. — Spondylosium, Breb. 



S. papillatum (?), W. and G. S. 



West ... Willsmere, Deepdene (pools) 



Genus 27. — Phymatodocis, Nordst. 



Genus 28. — Hyalotheca, Ehr. 



H. dissiliens (Sm.), Breb. ... Alex., Whan., Thorn, (lag.), 



Chelt. (s.), Yan Yean (Res., w.) 



Genus 29. — Streptonema, Wallich. 

 Genus 30. — Desmidium, Ag. 

 D. cylindricum, Grev. ... Box Hill (creek, pool) 



D. swartzii, Ag. ... ... Wlsm. Eildon (lag.) Chelt. (s.), 



Yan Yean (Res., plankton) 



Genus 31. —Gymnozyga, Ehr. 

 G. moniliformis, Ehr. ... Yarra Glen (lagoon) 



Descriptions of the New Forms. 



Pleurot/enium mamillatum sp. nov. (G. S. West). 



Small, moderately elongated, 14-15 times longer than the 

 diameter; semi-cells subcylindtical, slightly and very gradually 

 attenuated towards the apex, with a somewhat prominent basal 

 inflation and lo-ii undulations along each lateral margin, the 

 undulations becoming gradually smaller towards the apex ; apices 

 convex-truncate, furnished with 6-7 (4 visible) large, conical- 

 mamillate, somewhat diverging warts ; cell wall sparsely punctate. 



Length, 372-442 yu ; breadth at base of semi-cell, 28-31 jx ; 

 breadth in middle of semi-cell, 27-29 // ; breadth of apex, without 

 warts, 17-19 /J, with warts, 21-23 Z^- 



Habitat. — Yan Yean Reservoir, Victoria; in plankton, and 

 amongst weeds at the margin. 



This species is distinguished by the large size of the apical 

 warts, which are somewhat mamillate in character and few in 

 number. The semi-cells are approximately cylindrical in their 

 lower half, but the upper half is distinctly attenuated. 



Micrasterias mahabuleshwarensis, Hobson ; var. reductum, 

 var. nov. (G. S. West). 

 A variety with the inferior lobules of tlie lateral lobes much 

 reduced and very short. 



