146 
PEOCEEDINGS OF SOCIETIES. 
2 . —Dimetopia {Bush). 
1 . — JD. spicata {Bush). 
Bass’s Strait; Dr. Harvey. 
2 . — JD. cornuta {Bush). 
Bass’s Strait; parasitical on polyzoa; very abundant; Dr. Harvey. 
New Zealand; Dr. Joliffe. 
3. Calwellia, n.g* 
Cells in pairs, joined back to back* Each pair of cells arising by 
tubular prolongations from the pair next but one below it. Each pair 
having a direction at right angles to the next. At a bifurcation each 
cell of the primary pair giving otf a secondary pair. Ovicell subglo- 
bular, placed immediately above and behind the posterior margin of the 
cell aperture. 
1.— C. hicomis , n. s. Hate XV., Eigs. 13 and 13 a. 
The only known species. 
This genus supplies another link in the beautiful chain of modifica¬ 
tions in the arrangement of cells in pairs furnished by the Gemellariadae. 
By combining one of the peculiar characters of Notamia with a genera, 
appearance closely resembling Dimetopia, it affords another reason for 
retaining Notamia in the group, bearing, in fact, with the exception of 
the total absence of avicularia, the same structural relation to Notamia 
which Dimetopia bears to Gemellaria. The lower half of each pair is 
contracted and tube-like, the two tubes of which it is composed sepa¬ 
rating and curving over the walls of the inflated triangular upper half 
of the pair immediately beneath it. The coenoecium is thus formed of 
two incorporated, independent rows of pairs of cells, all the cells of each 
row being in the same plane, but at right angles to all the cells of the 
other row. This somewhat complicated structure might be better un¬ 
derstood if the reader would imagine another exactly similar double¬ 
stem incorporated at right angles with Eig. 13a, Plate XV. 
The cell-mouth is small, nearly horizontal on the upper surface of 
the cell. The margin is thickened, rising at the outer angles of the nearly 
straight lower lip into a pair of strong, incurved, blunt spines. The cell- 
wall seems to consist of two membranes, and round the lower lip and at 
the base of the spines there are a few small, oval and round, fenestrae, 
passing apparently through one layer only. A small, granular, perforated 
papilla rises immediately below the cell-mouth, the oval aperture pass 
ing right through the cell-wall. 
* I dedicate this genus, at Dr. Harvey’s suggestion, to Mr. Callwell, of Dublin, the 
well-known microscopist. 
