The British Lower Palaeozoic Crinoidea

Abstract

A full survey is given of all known Crinoidea from the Lower Palaeozoic rocks in Britain (including Ireland), but consideration of crinoid stem fragments is omitted, with a few exceptions. In the Ordovician 28 species are described or referred to, 16 being named as new 5 species were previously known, the remainder are too inadequately preserved for detailed naming. The Ordovician species belong to 17 genera, two of which are new. It is found that there are two faunal provinces - one covering the Anglo-Weleh area, and the other the Soots-Irish area. Crinoids of pre middle Caradoc age in the Scots-Irish area are closely related to contemporary forms in north America, while those in the Anglo-Welsh area belong to different genera, some being related to forms found in Bohemia. In the upper Caradoc and Ashgill the faunas are moro uniform, nearly all being of American affinities, and there appears to have been a mixing of forms from both faunal provinces. An especially noteworthy occurrence of crinoids is in the Ashgill Starfish Bed near Girvan, where nine genera (one new) are found, none of which has previously been recorded in Britain. In the Silurian 88 species are described or referred to; 10 of these are too inadequately known for detailed naming, but 11 others are described as new species. The Silurian species belong to 42 genera. No faunal provinces have been detected, the fauna being more or less uniform over the British area, so far as the records permit such a generalisation. This uniformity seems to be world wide. The Llandovery has 7 new species (2 named), only 1 having been previously recorded. 16 species (3 named as new) are present in the Wenlock Shale, though they are often poorly preserved. Reef conditions in the Wenlock Limestone favoured both crinoid growth and preservation and some 65 species are recorded from this horizon, mainly at Dudley. 10 species are recorded from the Ludlow formation (3 new), hut only one of these is found in the Upper Ludlow. In general it is considered that the faunas of the different Silurian formations are distinct enough to be recognised individually.