146 lransactions.—Zoology. 
Habitat: Throughout the whole of New Zealand; abundant in fresh 
water, extending into brackish water. 
A very variable shell, but easily recognized by its smooth rounded 
whorls. The aperture varies from nearly a half to a third of the length of 
the shell. The narrow, turreted, form is P. zealandiz, but I do not think 
it is distinct, as there are many intermediate varieties. 
The animal is in all respects like P. corolla. The central lobe of the 
median tooth is considerably produced. 
Our species appears to be quite distinct from the Tasmanian Paludina 
nigra (Q & G), the whorls in that shell, judging from the figure, being much 
more oblique, and the aperture nearly parallel to the axis. Hydrobia 
spelea is, I think, only a small form of P. antipodum. It was found, along 
with H. reevei, with moa bones in the Collingwood caves near Nelson. 
P. pupomes. 
Plate I., figs. D and H. 
Shell minute, oval, olive-green, or brownish; whorls 4, smooth, 
rounded; aperture ovate, two-fifths the length of the shell, peritreme 
continuous. 
Formula of the denticles, ra3 9; 20; 80 to 35. 
Axis, ‘06 to ‘07; breadth, 035. 
Habitat: Estuary of the Avon and Heathcote rivers, in brackish water. 
Not found in fresh water. 
This shell 1s very constant in its form, and very unlike the other species 
of the genus, but the animal and dentition at once indicate its relationship. 
No doubt it will be found in many other localities. The central lobe of 
the median tooth is considerably produced; the central denticle of the 
first lateral is rather larger than the others. The inner surface of the 
operculum has some small granules at its anterior end; these are not 
calcareous, 
EXPLANATION OF PLATE I., FIGS. A ro H. 
Al. Potamopyrgus cumingiana, x 5 times. 
2. embryonic shells x 25 times. 
B 4 Poiciibisapeahin stile: x 5 times. 
» animal x 5 times. 
Cc ; Potamopyra antipodum, three varieties x 5 times. 
or operculum x 8 times 
Pa pupoides, x 10 times. 
Potamopyrgus cumingiana, teeth x 470 times. 
Potamopyrgus corolla, median tooth x 470 times. 
Potamopyrgus antipodum, erence and first lateral teeth x 470 times. 
—— pupoides, median, first and second lateral teeth x 470, and opercd- 
um from the inside x 20 times. 
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