Article: Iocrinus in the Ordovician of England and Wales

locrinus contains more described species than any other crinoid genus known from the Ordovician of England and Wales. British species of this taxon generally have a smooth, conical, dorsal cup and a proximal stem which is pentagonal in transverse section. A new species, I. pauli, from the Llanvirn of the Builth Wells area, is unusual in having a ribbed dorsal cup and a proxistele of pentastellate transverse section. These features have hitherto been noted only in locrinus from North America. locrinus sp. cf. I. pauli is recognized from the Lower Llandeilo of Dyfed on the basis of disarticulated columnals and a poorly preserved crown. I. whitteryi Ramsbottom, from the Caradoc of Shropshire, is refigured to illustrate such diagnostic features as the anal sac, the brachial articulum, and the stem. The family locrinidae Moore and Laudon is now known to include six genera. With one exception of Lower Llandovery age, all known iocrinids are of Ordovician age, and can be divided into two groups depending upon the complexity of the anal series.