From the introduction:
"The classification in this Fossilium Catalogus largely follows that of Wright et al., 1996, but some ideas of Cooper, 1999, Monks, 1999 and Monks, 2002. are taken into account.
The reference lists that belong to the species are mainly references of specimens that are depicted. But also included are references that can be important for palaeobiogeographical research. They are compiled from literature. The lists are, of course, subjective and open to improvement. Several species are attributed provisionally to genera, and that with question marks, because further research is needed to clarify the taxonomical status of these species. I have designated 3 lectotypes. In 45 cases ‘lectotype requested’ is indicated."