I am indebted to the kindness of Professor Ramsay, Director-General, and of Professor Geikie, Director of the Scottish Branch of the Geological Survey of Great Britain, for the privilege of examining and describing a remarkable collection of fossil fish-remains from the Lower Carboniferous rocks (Calciferous Sandstone Series) of Eskdale and Liddesdale. Most of the specimens were collected by Mr Arthur Macconochie, one of the collectors attached to the Scottish Geological Survey; and Mr Walter Park of Brooklyn Cottage, Langholm, has also willingly co-operated in the search, so far as the district of Eskdale is concerned. I have myself also had the pleasure of twice visiting Eskdale, along with Mr Macconochie and Mr B. N. Peach, and on these occasions I obtained a few specimens for my own collection.