But if the form of these brooches be thus closely allied to the Celtic form, their ornament is no less closely allied to the Celtic system of ornamentation. The peculiar prickliness of the bulbs, which is the most marked feature of their character, is not distinctively Celtic, but a suggestion of it is occasionally found on Celtic silver-work, as, for instance, on the almost globular head of a Celtic brooch in the National Museum, and on a gold brooch found near Coleraine.[49] But the reverse hemispheres of the bulbous terminations of the Skaill brooches, which present this prickly ornamentation on the obverse, are also decorated with engraved designs. These are of two varieties, simple interlaced ribbon patterns and zoomorphic patterns. The character of the interlaced work so closely resembles the Celtic style that it may be said to be more Celtic than Scandinavian. The character of the zoomorphic work, on the other hand, is more Scandinavian than Celtic, and is suggestive of the style and treatment of the designs on the Manx crosses, while it more closely resembles some of the more characteristic designs of the purely Scandinavian metal-work of the heathen time. ----- Footnote 49: The gold brooch is figured in the _Ulster Journal_, vol. iv. p. 1. ----- The interlaced work is present on the reverse hemispheres of the bulbs of one of the largest of the prickly brooches, in the form of a circular pattern (Fig. 68) which is common in Celtic work, and may be seen on several of the sculptured monuments of the east coast of Scotland. Another circular pattern of interlaced work (Fig. 69), differing in its construction, but possessing the Celtic peculiarity of the divided bands, is found on the head of the pin of another brooch. The collars of the first-mentioned example are also surrounded by bands of interlaced work in a running pattern (Fig. 70), which is common on Celtic stone and metal work. [Illustration: Fig. 68.—Circular pattern on reverse of the bulbs of the brooch described p. 80 (actual size). ] [Illustration: Fig. 69.—Circular pattern on the head of the pin of brooch, described pp. 81-82 (actual size). ] [Illustration: Fig. 70.—Pattern on the reverse of the bulbs of the brooch described p. 80 (actual size).] [Illustration: Fig. 71.—Zoomorphic pattern on bulb of the brooch in the Skaill hoard, shown as Fig. 59.] [Illustration: Fig. 72.—Ornament on bulb of brooch, shown as Fig. 59 (actual size).] [Illustration: Fig. 73.—On the pinhead of brooch, shown as Fig. 59 (actual size).] [Illustration: Fig. 74.—On a single bulb of a brooch in the Skaill hoard (actual size).] [Illustration: Fig. 75.—On one of the bulbs (actual size).] [Illustration: Fig. 76.—On one of the bulbs (actual size).]