Four new specimens of phalangiotarbid (Arachnids: Phalangiotarbida) from the Upper Carboniferous (upper Westphalian A) of Westhoughton, Lancashire, UK, are referred to Mesotarbus peteri sp. nov. An additional Lancashire phalangiotarbid, Phalangiotarbus subovalis (Woodward, 1872), from the Upper Carboniferous (lowerlmiddle Westphalian A) of Burnley, is redescribed and designated the neotype of this species. This material allows new interpretations of the opisthosomal segmentation and respiratory organs of phalangiotarbids, and a reconstruction of Mesotarbus peteri is presented.

Fossils from a new Upper Carboniferous LagerstaÈ tte of Late Westphalian A (Langsettian) age at Bickershaw, Lancashire, UK, are reported and an account of the locality is presented. In common with many Upper Carboniferous LagerstaÈ tten, the fossils are preserved within siderite nodules hosted by coal seam roof shales. The fossils include a diverse assemblage of plants, nonmarine bivalves, crustaceans, insects, arthropleurid fragments, a euthycarcinoid, xiphosurans, a whip scorpion, scorpion cuticle fragments, ®sh scales and coprolites. The arthropods, with a greater diversity and abundance of aquatic taxa, and the non-marine bivalves suggest a brackish,¯uvio-deltaic setting probably above the Haigh Yard Coal. However, tabulation of the relative abundances of fossils is of limited palaeoecological value, since the data represent a combination of the original community structure, each groups' preservation potential and mixing of material from dierent stratigraphic horizons on the tip.

Exceptionally preserved fossils are described from the Westhoughton opencast coal pit near Wigan, Lancashire, UK (uppermost Westphalian A, Lower Modiolaris Chronozone, regularis faunal belt). The fossils occur within sideritic concretions in a 1.5-metre zone above the Wigan Four Foot coal seam. Arthropods dominate the fauna and include arachnids, arthropleurids, crustaceans, eurypterids, euthycarcinoids, millipedes and xiphosurans. Vertebrates are represented by a single palaeoniscid fish, numerous disarticulated scales and coprolites. Upright Sigillaria trees, massive bedded units and a general lack of trace fossils in the roof shales of the Wigan Four Foot coal seam suggest that deposition of the beds containing these concretions was relatively rapid. Discovery of similar faunas at the equivalent stratigraphic level some distance away point to regional rather than localized controls on exceptional preservation.

SUMMARY A new specimen of the fossil arachnid Maiocercus celticus (Pocock, 1902) (Arachnida: Trigonotarbida), from the Upper Carboniferous (Westphalian A) Coal Measures of Westhoughton, Lancashire, UK is described. The taxonomy of Maiocercus celticus is revised and a new reconstruction is presented.

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