*MacRae, R. Andrew and Hall, R.L., Department of Geology and Geophysics, University of Calgary, Calgary, Alberta, T2N 1N4.

Periechocrinus schultzianus is identified and described for the first time since its original publication from the Ludlow age (Silurian) Green Member of the Moydart Formation, Arisaig, Nova Scotia. It is the first complete crinoid to be described from Arisaig, despite substantial study of the rest of the fauna at the locality since the 1800's. P. schultzianus is a relatively large crinoid, distinguished from other species within the genus by a simple, isotomous, twice-branching fixed brachial pattern, and 20 unbranching biserial arms. One of the studied specimens is missing the "E" ray (resulting in only 16 arms), and is interpreted as a mutation of the living crinoid that persisted throughout its life.

Articulated P. schultzianus specimens occur in association with a diverse, well-preserved invertebrate fauna, including other crinoids (Cicerocrinus elegans), brachiopods (Salopina, Protochonetes, and rhynchonellids), bryozoans, bivalves, nautiloids, cornulitids, tentaculids, conularids, and nautiloids within 1-4cm thick unbioturbated "post-storm" mudstone beds found immediately above erosive-based, storm-deposited (convex-up ripples and hummocky cross stratification) impure bioclastic limestone. These "storm beds" punctuate a strongly-bioturbated, dominantly siltstone and shale stratigraphy containing brachiopods and other biota in life position, which represents deposition during "normal" shelf conditions. Although the fauna is clearly transported from life position, the "post-storm" units represent deposition of live or recently killed crinoids by waning storm-related currents within a short time (less than a few days) immediately after a storm event. In contrast, the disarticulated and probably long-dead shell fragments found in the underlying bioclastic limestone bed were probably winnowed from the sediments of the surrounding area and deposited in scours while the storm was still active.