In this paper are described seventeen species of rotifers, of which six belong to the three genera, Filinia, Tetrarnastix and Pedalia of the family Filiniidae, seven to the genus Monostyla and the rest four to the genus Trichocerca. More species of Monostyla may be described in a succeeding issue. The species belonging to Trichocerca which are described in the present paper are the continuation from the preceding issue under the same title in the present journal.

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This paper describes the salinity expressed in terms of electrical conductivity in the mouth of the River Nikko and its vicinities where there are the tidal effect. The electrical conductivity measurements are used for the estimation of the salinity of river-water instead of chemical analysis, because the sudden and sharp changes of salinity distribution were made difficult chemical analysis for the lapse of time.
Conductivity of surface layer is almost the same as that of bottom layer in the high and low tides.
In Figures 3-8 and Table I, it is shown that the saline waters are stratified due to the density. From the inclinations of iso-electrical conductivity lines in the flooding tide, can be calculated the current velocities of bottom layers which are lager than the surface layers.
The saline damages for the corps in the basin are due to the salt water percolation from the river or the sea into the basin, because one third in area of the River Nikko is lower than the sea level or water level in the high tide. Hence, to remove the saline damage, there are methods either to let the water of the River Kiso flow into the River Nikko or rise the level of the River Nikko as to be higher than the sea level.

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Observations in the Nabebuta and Kaioku districts show that the deep artesian water is not contaminated by the sea water, despite of the saline damage in the ground surface owing to the saline water percolation through the earth dam. The artesian heads in those areas are measured to be always lower than the sea level. These results suggest the existence of the impermeable layer between the aquifer and the sea water. Tidal changes in the water levels of four artesian wells are observed and are found the results corresponding with theoretically presented by the author under the assumption that the tidal effect on the artesian head is only due to the fluctuations in the loading weight upon the submarine aquifer. Some of the values which represent the characteristics of the aquifer are computed in using the analytical treatment from the observed results.

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