This common fossil of the Guelph of Canada has not been noted in the Le Claire beds of Iowa, or their immediate extension into adjacent states. Its occurrence, therefore, at Port Byron, Illinois, in the Barrett quarries one and one-half miles north of the town, is of special interest, since it shows a range much further to the west than hitherto observed, and a co-mingling of the Guelph and Niagara faunas in the Le Claire, similar to that in the so-called Guelph of Wisconsin. The specimens are well preserved, casts of the normal type not conforming to the variety of M. Compressus
