Maskell. — On the Neiv Zealand Desmidiese. 243 



C. tenne, sp. nov. 



Fig. 10. 



Frond sub-orbicular, the segments slightly broader than long. Ends 

 rounded. Edge smooth ; constriction deep, narrow, linear. Frond neither 

 punctate nor granulate. A single starch vesicle is visible in the centre of 

 each segment. 



End view elliptic. 



Length of frond 15-5 /*; breadth at constriction 3 ft. 



Not common : my specimens were all found amongst Chara, in running 

 water, near Christchurch. 



This is a very minute plant, scarcely larger than C. pusillum. It nearly 

 resembles C. bioculatnm, Brebisson, but differs in the absence of the distinct 

 isthmus which, according to Ealfs, connects the segments of that species, 

 and in having a deep and narrow, instead of a wide and gaping, constric- 

 tion. C. exiguum, Archer (Micr. Journ., 1864, pi. vi.), has oblong seg- 

 ments. I find none of the minute Cosmaria described exactly corresponding 

 to this form. It has not the colour of C. tinctum, Ealfs. 

 5. Xanthidium, Ehrenberg. 



-X". cristatum, Brebisson. S. (E. XIX.) 



I have not found this plant in Canterbury. It seems to be not uncom- 

 mon in Hawke's Bay. 



X. aculeatum, Ehrenberg. S. (E. XIX.) 



Same remark as for the last species. 



6. Arthrodesmus, Ehrenberg. 



A. incus, Brebisson. S. (E. XX.) 



Only front Hawke's Bay. 



A. convergent, Ehrenberg. S. (E. XX.) 



Only a single specimen observed, in a gathering from Hawke's Bay. 

 The spines on the ends of the segments in this specimen were sigmoid, 

 bending slightly outwards. 



7. Staurastrum, Meyen. 



S. dilatatum, Ehrenberg. (E. XXI.) 



Not uncommon. 



S. alternans, Brebisson. (E. XXI.) 



Bare. 



8. tricome, Brebisson. S. (E. XXII.) 



I cannot identify any of my Canterbury specimens with this form, which 

 appears to be common in Hawke's Bay. 



Eabenhorst considers the two last as only varieties of S. dilatatum. The 

 distinction between S. alternans and 8. tricome is very slight, depending 

 upon a minute prolongation of the angles of the latter into short processes. 



