Synopsis Marine Jurassic sequences of Jaisalmer Basin of north-western Rajasthan have been palaeontologists' paradise for the study of mega fauna and their biostratigraphy from as far back as 1877. No comprehensive record of any group of these fossils has so far been published, except few isolated reports of ammonites from this basin. The present Palaeontologia Indica deals with various details ammonite fauna of Jaisalmer Basin-its taxonomy, fighred description and distribution of the fauna in time and space. it also establishes a biostratigraphic frame of Jurassic sequence of the basin. This study may fill the existing gap in knowledge in the precise lithostratigraphic and chronostatigra[hic subdivisions of Jurassic succession of rajasthan. Detailed field work included establishment of continuous lithocolumns, their systematic measurement that has led to better understanding the lithological sequence of the area. The lithostratigraphy has been modified, redefined and type sections of some lithostratigraphic units have been described.