The comparison of the bryozoan faunas of Europe and North America is very difficult for several reasons: First, the rock series are incomplete and never in strict conformity. Second, the European publications are much scattered and do not always correspond to the richness of the formations considered. France especially, with strata enormously rich in bryozoa, has insufficient literature. Third, the hesitations of classification, which commence only when one tries to adjust them, increase the causes of uncertainty. Finally, most of the Tertiary faunas of America and Europe originated in totally different areas. We are able, therefore, to give at this time only an approximate view of the subject.
In Europe the bryozoan fauna of the Lower Eocene is unknown, for there were then lagoon conditions incompatible to the development of these organisms. Only the Montian has been studied heretofore by Pergens and has furnished a . . .