Sentence:  On stones and sea-weeds between tide-marks. Sometimes parasitical on Zostera marina. It is very abundant on some parts of the Solway at low-water mark on a stony bottom, and becomes a great nuisance to the stake-nets, which require to be <WSD>tidely</WSD> cleared from the quantity that is caught by them. 
Meaning of the word marked with <WSD> tags:  At each tide; each time the tide comes in; tidally.