not with the mouldings of the classical archivolt, but with the cusp of the great arch at Ctesiphon. So far as I am aware the earliest example of this cuspidated ornament in monumental architecture is at Ctesiphon. It appears in northern Syria in the fifth century A.D., when it can be seen both with the cusps pointing inward[327] and with the cusps pointing outward.[328] In the latter form it bears a close resemblance to the broken palmette of late Graeco-Roman ornament,[329] and its origin is probably to be sought in oriental Hellenism, but whether it was developed in the Syrian or in the Mesopotamian regions I cannot determine. It became a common motive in Syrian architecture during the sixth century,[330] where it is used in both forms, but in the Mesopotamian sphere it is almost always inverted, as at Ctesiphon. We have it at Ukhaiḍir, not only in the façade but also on the arches of the mosque doorways and possibly in the lîwân arches in the courts.[331] In exactly the same form it is employed in the early Abbâsid buildings of Sâmarrâ,[332] and there is another notable example of its use over the doorway of the mosque at Ḥarrân, where an outward-pointing cusp is used (Plate 84, Fig. 2). In the mosque at Mayâfârqîn it is found inverted on the elaborate arches which cover the miḥrâb niches, on the relieving arches over the doors of the outer north wall (Plate 84, Fig. 3), and on the blind niches above. This part of the wall belongs to the earlier portion of the building, which is ascribed, in an inscription round the dome, to the Ortokid Alpi (A.D. 1152-1176). It is a common feature of Ortokid decoration at Diyârbekr,[333] and in the first half of the thirteenth century it is seldom absent from the lintels of Christian churches and Mohammadan mosques in Môṣul and the surrounding districts,[334] nor yet, in the late fourteenth and early fifteenth centuries, from the lace-like decoration of the arches in the mosques at Ḥasan Kaif[335] (Plate 84, Fig. 1). Other examples in late Mohammadan architecture are too numerous to be mentioned. I select the few which I have quoted because they are little known.