Vague as all this may probably appear, there is one dolmen in Ireland which seems to have a date. The great grandson of Dathi, whose red pillar-stone at Rath Croghan, erected A.D. 428, we have already pointed out, was named Ceallach. He was murdered by his four foster-brothers through envy about the sovereignty. They were hanged for their crime at a spot known as Ard-na-Riagh, near Ballina, and were buried on a hill on the opposite side of the river, where a dolmen still stands, and is pointed out as the grave of the four Maols, the murderers. These particulars are related in the Dinnsenchus, in the Book of Lecan, and in the Annals of the Hy Fiachrach, translated by Dr. O'Donovan (p. 35), who, in a note, adds that "this evidence, coupled with the description of the situation on the other side of the Moy, opposite Ard-na-Riagh, leaves no doubt of its identity." The dolmen in question has nothing very remarkable about it. The cap-stone, which measures 9 feet by 7 feet, is hexagonal in form, and is supported on three uprights, arranged similarly to those of Kit's Cotty House. It is perfectly level, and stands about 4 feet above the level of the soil. The cap-stone may have been fashioned into its present form by art; but there is no sign of chiselling, and, altogether there is nothing that would attract especial attention.[264] The interest rests with its date. If it can be established that it belongs to the beginning of the sixth century, which I see no more reason for doubting than Dr. O'Donovan does, it is a point gained in our investigation, in so far at least as dates are concerned. It would be tedious to enumerate the other dolmens in Ireland which have neither dates nor peculiarities to distinguish them from others of this class, but there is one monument of a megalithic character in Ireland which must be described before leaving the country, though it certainly is not a dolmen, and its date and use are both mysterious at present. [Illustration: 83. Sketch-Plan of Monument in the Deer Park, Sligo. Scale 40 feet to 1 inch.]