The discovery of the ammonite, Bouleiceras cf nitiscens Thevenin, below the base of the limestones which underly the equivalent of the Spiti shales in the Hama Mesozoic succession, shows that the Trais is not represented in them and that they belong entirely to the Jurassic, in the Thai-Bara Gali section at least. The presence of the fossil indicates a Toarcian (upper Liassic) age for the beds in which it is found. Some of the implications of its presence are discussed.