Another kind of circular knotwork is formed by enclosing the simpler sort of knots derived directly from plaitwork within a circular band, which crosses over in one or two places and turns inwards to form the enclosed knots. [Illustration: Circular knotwork from Tarbet, Ross-shire] The illustrations of the different kinds of circular knotwork from actual examples show the process of development. [Illustration: Circular knotwork from Monasterboice, Co. Louth] [Illustration: DETAIL OF ORNAMENT ON ERECT CROSS-SLAB AT NIGG, ROSS-SHIRE _From photographs of the cast in the Science and Art Museum, Edinburgh, supplied by Mr. Vallance, Curator_] By the term _triangular knotwork_ is meant interlaced patterns, the setting-out lines of which form triangles only or triangles and lozenges. The patterns are made by distorting the simple knots derived from plaitwork, so as to adapt them to the triangular shape. This species of knotwork is very seldom seen except in a few of the Hiberno-Saxon MSS. and on some of the sculptured stones of Ireland and Scotland. The best examples are at Kilfenora, Co. Clare; Ulbster (now at Thurso Castle), Sutherlandshire; and Dunfallandy, Perthshire. [Illustration: Triangular knotwork from Ulbster, Caithness] Under the head of ringwork and chainwork are included all patterns composed of circular, oval, and looped rings interlaced symmetrically round a centre, or arranged so as to form a long chain. Patterns of this kind are not found in the best Celtic work, and when they occur it is generally an indication either of Scandinavian influence or of the style being debased. A certain number of modifications of the interlaced-work already described are produced by adapting the patterns so that they will fit into circular or annular spaces. Instances of this may be seen on the erect cross-slabs at Hilton of Cadboll (now at Invergordon Castle) and Nigg, Ross-shire; Glamis, Forfarshire; and Rossie Priory, Perthshire; and on the Lough Erne and Monymusk Reliquaries. [Illustration: Triangular knotwork from Dunfallandy, Perthshire] STEP-PATTERNS