Scarabs with ornamental devices, such as coils and twisted rope patterns engraved upon them, appear first about the reign of Usertsen I, and continued in use to the middle of the Eighteenth Dynasty, after which period they rarely occur. The date of any single specimen may generally be determined by the form of the back, but the glazing and general style of cutting is also important in this connection. Specimens of the late Twelfth and early Thirteenth Dynasties are often fine examples of ornamental art: they are generally designed with much care, and executed with wonderful minuteness and delicacy of touch. Finely worked specimens are also found of the time of Queen Hatshepsut and Thothmes III. A representative series of coil and rope-pattern scarabs is given in Pls. XVIII and XIX. The rope-patterns figured in Pl. XIX, 1-3, are of the Hyksos period, while those on Pl. XVIII, 1-15, 18, range in date from the Twelfth to the Eighteenth Dynasties. The coil-patterns given in Pl. XIX, 4, 5, 9, are certainly of the Hyksos period, while the remainder of the coil patterns are mainly of the late Twelfth and Eighteenth Dynasties. Often the continuous loop coil was used to ornament the scarabs of kings and officials. The earliest example, indeed the earliest example of any coil-pattern in Egypt, is found on a scarab of Usertsen I, most exquisitely worked and fully developed (fig. 82). [Illustration: Fig. 82.] For a long time past it has been thought that the spiral as a motive in decoration originated in the Nile Valley, and much misconception seems to prevail among archaeologists as to its occurrence in Egypt. Prof. Petrie says[114] that its earliest use in the country was for the decoration of scarabs, and he would trace the spiral motive back as far as the Fifth Dynasty. The single scarab that he instances, it is true, bears the prenomen of Dad-ka-Ra (Assa), but there is not the slightest reason to make one believe that this particular specimen is contemporaneous with the king whose name it bears; the whole style of it, on the contrary, clearly shows that it belongs to no earlier a date than the Eighteenth Dynasty. Prof. Petrie also attributes a number of scarabs bearing coil, hook and link ornamentation to the Sixth and Eighth Dynasties, but these have been conclusively shown by Fraser[115] and Griffith[116] to be in reality _post_ rather than _pre_ Twelfth Dynasty. The fact is that the spiral has not yet been found on Egyptian monuments of an older date than the reign of Usertsen I. It was then used as a motive for decorating a ceiling in the tomb of a chieftain at Assiut.[117] Employed architecturally it is not found again until the beginning of the Eighteenth Dynasty, when it was perhaps the most frequent motive for ceiling decorations in Theban tombs. In these tombs it is generally coloured yellow, to represent gold, and it is highly probable that the ornament itself originated in metal wire-work.[118]