. Bulletin of the British Museum (Natural History). . 4 5 -r 6 8 T" 9 —1— 10 —I— 1 1 —I— 1 2 —I 13 zooecial generation Fig. 7 Astogenetic gradients of zooecial length and width in a colony of 'Stomatopora' melvillei sp. nov., BM(NH) D55111. zone of astogenetic change for zooecial length is poorly differentiated and possibly brief, with relatively little difference in size between zooecia of different generations (Fig. 7). Zooecial width increases at a low rate for 10 or more zooecial generations. Measurements. TAM, 0-12-0-16 mm; TPM, 0-18-O-26 mm; FWL, 0-60-0-90 mm; FWW, 0-24-0-
. Bulletin of the British Museum (Natural History). . 4 5 -r 6 8 T" 9 —1— 10 —I— 1 1 —I— 1 2 —I 13 zooecial generation Fig. 7 Astogenetic gradients of zooecial length and width in a colony of 'Stomatopora' melvillei sp. nov., BM(NH) D55111. zone of astogenetic change for zooecial length is poorly differentiated and possibly brief, with relatively little difference in size between zooecia of different generations (Fig. 7). Zooecial width increases at a low rate for 10 or more zooecial generations. Measurements. TAM, 0-12-0-16 mm; TPM, 0-18-O-26 mm; FWL, 0-60-0-90 mm; FWW, 0-24-0-45 mm. Remarks. This species resembles the 5. granulata (Milne Edwards, 1838) of Walter (1972: 293-294) but has shorter zooecia. It differs from 5. incrassata (d'Orbigny, 1850) in the smaller zooecial dimensions. 'S.' melvillei is a common species at Faringdon and can be found encrusting a wide variety of substrates. It is most likely to be confused with Voigtopora calypso (below), which has zooecia of similar size. However, the parallel-sided zooecia of '5.' melvillei contrast with the slightly barrel-shaped zooecia of V. calypso, branches of V. calypso are never biserial, and lateral branching is known only in V. calypso. Genus VOIGTOPORA Bassler, 1952 Type species. Alecto calypso d'Oroigny, 1850, by original designation; Senonian of Saintes, Charente-Maritime, France. Remarks. lilies (1976) has redescribed the type species of Voigtopora. This genus differs from typical Stomatopora principally in the occurrence of lateral branching. Voigtopora also has zooecia which extend proximally as long, narrow tubes flanking the proximal zooecium. Range. Aptian (?Hauterivian) to Campanian. Voigtopora calypso (d'Orbigny, 1850) Figs 8-12 1850 Alecto calypso d'Orbigny: 265. 1851 Alecto calypso d'Orbigny; d'Orbigny: 844; pi. 630, figs 5-8. 1853 Stomatopora calypso (d'Orbigny) d'Orbigny: 841. 1926 Stomatopora calypso (d'Orbigny); Canu & Bassler: 5; pi. 26, fig. 11. 1974 Voi
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