Page:Transactions NZ Institute Volume 15.djvu/329

C. tenue, sp. nov.

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 μ; breadth at constriction 3 μ.

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. bioculatum, Brébisson, but differs in the absence of the distinct isthmus which, according to Ralfs, connects the segments of that species, and in having a deep and narrow, instead of a wide and gaping, constriction. C. exiguum, Archer (Micr. Journ., 1864, pl. vi.), has oblong segments. I find none of the minute Cosmaria described exactly corresponding to this form. It has not the colour of C. tinctum, Ralfs.

X. cristatum, Brébisson. S. (R. XIX.)

I have not found this plant in Canterbury. It seems to be not uncommon in Hawke's Bay.

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

Same remark as for the last species.

A. incus, Brébisson. S. (R. XX.)

Only from Hawke's Bay.

A. convergens, Ehrenberg. S. (R. 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.

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

Not uncommon.

S. alternans, Brébisson. (R. XXI.)

Rare.

S. tricorne, Brébisson. S. (R. XXII.)

I cannot identify any of my Canterbury specimens with this form, which appears to be common in Hawke's Bay.

Rabenhorst considers the two last as only varieties of S. dilatatum. The distinction between S. alternans and S. tricorne is very slight, depending upon a minute prolongation of the angles of the latter into short processes.