Revision of Plumulites ruskini Lamont, and new data from the Silurian of the Pentland Hills, Scotland

Disarticulated sclerites of plumulitid machaeridians were collected from the Wether Law Linn Formation (Telychian) in the Pentland Hills, Scotland. The specimens are described and compared to specimens collected earlier from the same horizon and locality. Other specimens from the same horizon, assigned in previous works to Turrilepas haswelli then to Plumulites sp., are figured here for the first time. The micro-ornament on plumulitid machaeridians is also documented for the first time. Seven sclerite types are identified and tentatively associated into scleritomes. The collection from the Pentland Hills is compared with other Ordovician and Silurian taxa from various Scottish localities, and this comparative study indicates that the present collection may constitute a new taxon. Nevertheless, complete individuals have to be collected to warrant a confident taxonomic identification.