During a short vacation visit to Derbyshire I have had the opportunity of making some further notes on burrows in limestone rocks, which may be worth recording. These burrows, it will be remembered, have been attributed by Messrs. Darbyshire, Mackintosh, and others, to the action of Pholades, a conclusion which I ventured to oppose, after an examination of several instances in the neighbourhood of Llandudno. Mr. Darbyshire calls attention, in his paper, to the occurrence of these burrows near Buxton, on Grin Edge and Harper Hill, at a height of about 1400 feet above the sea. I was therefore fully prepared to meet with them in the Carboniferous Limestone in other parts of the county.