The castles, which according to Robert de Monte, Henry I. built altogether [_ex integro_] were Drincourt, Chateauneuf-sur-Epte, Verneuil, Nonancourt, Bonmoulins, Colmemont, Pontorson, St Denis-en-Lyons, and Vaudreuil. Many of these may have been wooden castles; Chateauneuf-sur-Epte almost certainly was; it has now a _round_ donjon on a motte. The "Tour Grise" at Verneuil is certainly not the work of Henry I., but belongs to the 13th century. APPENDIX R THE SO-CALLED SHELL KEEP We have three accounts of motte-castles from the 12th century: that of Alexander Neckham, in the treatise _De Utensilibus_; that of Laurence of Durham, cited in Chapter VII., p. 147; and the well-known description of the castle of Marchem, also cited in Chapter VI., p. 88. All these three describe the top of the motte as surrounded by a wall (of course of wood), within which is built a wooden tower. The account of Marchem says that it was built in the middle of the area. This supports the conjecture in the text. Mr H. E. Malden has shown (_Surrey Archæolog. Collections_, xvi., 28) that the keep of Guildford is of later date than the stone wall round the top of the motte. Remove this tower, and there would be what is commonly called a shell keep. It would appear, therefore, that it was a common practice to change the bank or stockade round the top of the motte into a stone wall (no doubt as a defence against fire), leaving the keep inside still of wood. Four of the pictures from the Bayeux Tapestry (see Frontispiece) all give the idea of a wooden tower inside a stockade on a motte. APPENDIX S PROFESSOR LLOYD'S "HISTORY OF WALES" I regret that this valuable work did not appear until too late for me to make use of it in my chapter on Welsh Castles. It is worth while to note the following points in which Professor Lloyd's conclusions differ from or confirm those which I have been led to adopt. Aberystwyth and Aberrheiddiol.--"After the destruction of the last Aberystwyth Castle of the older situation in 1143, the chief stronghold of the district was moved to the mouth of the Rheiddiol, a position which it ever afterwards retained, though people still insisted on calling it Aberystwyth" (514). "The original castle of Aberystwyth crowned the slight eminence at the back of the farm of Tan y Castell, which lies in the Ystwyth valley 1-1/2 miles S. of the town. There is the further evidence of the name, and the earthworks still visible on the summit" (426, _note_). Carreghova.--I ought perhaps to have included this castle in my list, though on the actual map its site is within the English border; but as there are absolutely no remains of it [D. H. M.] it does not affect the question I am discussing.