Concerning your question, there are several papers published in the last 10 years on the Silurian "Orthoceras"-Limestone facies of Sardinia, Italy ... Please try:
Gnoli & Serventi 2006: A further oncoverid nautiloid from the Upper Silurian of Southwest Sardinia Geo.Alp 3: 3-8.
Histon & Gnoli 1999: Nautiloid Paleobathymetry from the Silurian 'Orthoceras Limestone' Facies of SW Sardinia, Italy. In: Advancing Research on Living and Fossil Cephalopods: 381-394.
Gouwy & Corradini 2006: Graphic correlation of the Sardinian Ockerkalk (upper Silurian: Implications on the conodont biostratigraphy. GFF 128: 103-108.