. Bulletin of the British Museum (Natural History), Geology. 3mm ^&k 138b. â ?'A< Fig. 138 a, b, Mitrocystella sp. a, dorsal and b, ventral aspect. Locality: Pontyfenni. B. rushtoni Biozone, Pontyfenni Formation, Upper Arenig. E63158a, b. Fig. 139 a, b, Cothurnocystis sp. a, dorsal and b, ventral aspect. Note the gill slits as a prominent series of openings on the left side of the head. Locality: Llwyn-crwn. B. rushtoni Biozone, Pontyfenni Formation, Upper Arenig. NMW , b. quarry at Llwyn-crwn. The purpose of this note is to record these zoologically important animals, in the
. Bulletin of the British Museum (Natural History), Geology. 3mm ^&k 138b. â ?'A< Fig. 138 a, b, Mitrocystella sp. a, dorsal and b, ventral aspect. Locality: Pontyfenni. B. rushtoni Biozone, Pontyfenni Formation, Upper Arenig. E63158a, b. Fig. 139 a, b, Cothurnocystis sp. a, dorsal and b, ventral aspect. Note the gill slits as a prominent series of openings on the left side of the head. Locality: Llwyn-crwn. B. rushtoni Biozone, Pontyfenni Formation, Upper Arenig. NMW , b. quarry at Llwyn-crwn. The purpose of this note is to record these zoologically important animals, in the hope that further search will discover more of them and thus allow this part of the fauna to be properly described. All the chordates found are primitive forms which retain a calcite skeleton of echinoderm type ('calcichordates'). General accounts of these animals are given in Jefferies (1981a, 1986). To avoid confusion it must be mentioned that many workers regard them as echinoderms, notably. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original British Museum (Natural History). London : BM(NH)
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