Monograptids from the McAdam Formation (Silurian), Nova Scotia

The McAdam Formation (Silurian, Nova Scotia) of W. H. Twenhofel has yielded three species of monograptids. Two species, Monograptus cf. M. varians Wood and M. sp. (of the M. chimaera (Barrande) type), are from a lower stratigraphic position. They indicate an early Ludlow age. The one species from a higher stratigraphic level is described here as M. fritschi cf. var. linearis Boucek. It suggests correlation with the British Monograptus leintwardinensis Zone. The stratigraphically higher species had earlier been identified as M. riccartonensis Lapworth and as M. wandalensis Walney & Welch. Although the earlier identifications had led to assignment of a greater age, the present study suggests that the graptolite-bearing part of the McAdam Formation ranges in age from early to probable middle Ludlow. Pelecypods are abundant within the formation. Some are found in association with the graptolites.