The diverse brachiopod faunas from the Calcaire de Ferques of north France and the Lime Creek Formation of Iowa show a remarkable homeomorphy. They are both of Frasnian age and occupied similar mid-shelf muddy carbonate environments. It is possible to match species in the two faunas on external form; this similarity can also be seen in the population histograms. The two areas originated in different faunal provinces, however, and serial sections show that homeomorphic forms were not genetically related. Thus it seems possible that the similarity between the two faunas is entirely a result of adaptation to similar environments.