I Have obtained a considerable number of specimens of Thecidium ornatum, Moore, from the Coral Rag, in the bed containing Phasianella (Pseudomelania) striata; Pseudodiadema versipora, Hemicidaris intermedia, etc., from a quarry between Ayton and Scarborough. My friend, the late Mr. Charles Moore, F.G.S., gave me some specimens of this Brachiopod from the Coral Eag of Lyneham, Wiltshire, with which the Yorkshire Thecidium perfectly agrees in form. This shell, especially the dorsal valve, is plentiful at Ayton, but it is troublesome to find on account of its small size; it is best obtained by washing the marl; occasionally it is found attached to Ostrea.