Several species of Triassic and Jurassic ammonites have been found in Slovenia up to the present. Layered limestone south of Leše near Prevalje yielded a rich group of fossils, primarily consisted of ammonites. Ivan Ocepek and Matija Križnar from the Slovenian Museum of Natural History examinated the samples and determined that the found heteromorphic ammonites are first of its kind in Slovenia. The purpose of my research paper was to review and taxonomically define the ammonites found on site, which are the property of Ivan Ocepek and to try to interpret the environment and time in which they lived. For the purpose of this research paper, three stratigraphic profiles have been studied and thirteen thin sections for optical microscopy have been made. In this assignment I have reviewed forty-six samples, of which I determined six species and seven genera, eleven samples remained undetermined, because of bad condition or my inexperience in this field. Finally I interpreted that the limestone deposited in a deep sea, pelagic environment during the Early Cretaceous.