The pitchstones of Arran have been so well known for more than a century that further description may seem to require an apology. Except for Judd's description of the Drumadoon and Cir Mhor occurrences,1 most of the previous investigations have dealt with the Corriegills rocks. The object of the present paper is to give a description of the glassy rocks and the felsites associated with them, which are found outwith the area treated in the Geological Survey memoir on North Arran, and to discuss shortly several of the more striking characteristics which they exhibit. The occurrences considered include the Monamore Glen sills and dykes, the Glen Ashdale composite dyke, the series of intrusions in the neighbourhood of Tighvein and the Burican pitchstone. The Monamore Pitchstones. The earliest notice of this series of intrusions occurs in Bryce's “Geology of Arran.” In the edition published in 1859 no mention is made of it, but in the third edition, published about 1865, he describes two beds of pitchstone in “Moneadmhor Glen,” associated with “claystones, hornstone, quartz-rock, and porcellanite.”2 Zirkel,3 in his account of his journeyings in the Western Isles, mentions incidentally, in his description of the Corriegills and Tormore dykes, the same two intrusions, and notices that they contain thicker spherulites than is usual in this type of rock, and small green hornblende prisms, while associated with them is a “hornsteinahnliche felsit.” Similarly, Allport4 refers to them, but gives no details. This series of intrusions comprises one felsite dyke and This 250-word extract was created in the absence of an abstract