. Bulletin of the British Museum (Natural History), Geology. 80 P. D. TAYLOR ably Beer Head Limestone Formation, mantelli Zone; see Jarvis and Tocher 1987], Beer Head, Devon, England, Bather Collection. Paratype: BZ 998, Cenomanian, Wilming- ton Sands [a facies of the Beer Head Limestone Fm.], Grizzle Bed, White Hart Sandpit, Wilmington, Devon, Greenaway Colin. Name. From Mitra, Latin for head-dress, with reference to the similarity in shape of the operculum to a Bishop's mitre. Description. Colony multilamellar, each layer about 0-45 mm thick. Ancestrula unknown. Overgrowths arise through int
. Bulletin of the British Museum (Natural History), Geology. 80 P. D. TAYLOR ably Beer Head Limestone Formation, mantelli Zone; see Jarvis and Tocher 1987], Beer Head, Devon, England, Bather Collection. Paratype: BZ 998, Cenomanian, Wilming- ton Sands [a facies of the Beer Head Limestone Fm.], Grizzle Bed, White Hart Sandpit, Wilmington, Devon, Greenaway Colin. Name. From Mitra, Latin for head-dress, with reference to the similarity in shape of the operculum to a Bishop's mitre. Description. Colony multilamellar, each layer about 0-45 mm thick. Ancestrula unknown. Overgrowths arise through intrazooecial fission; pseudoancestrulae are autozooids with apertures about 0-14 x 0-12 mm in size; secondary zones of astogenetic change marked by increasing zooid size and elongation of apertures. Organization fixed-walled. Zooidal apertures closely-spaced, arranged in regular quincunx, dis- rupted close to overgrowth origins. Autozooids (Figs 230, 231) of large size, frontally elongate, about 2-3 x longer than wide, typically diamond-shaped in outline but sometimes rhomboidal; frontal wall convex, occu- pying about half of the frontal surface, with circular pseudopores; boundary wall inconspicuous, slightly salient. Aperture (Fig. 233) very large, elongate, about 1-5 to almost twice as long as wide, attaining maximum width between the hinge line and mid-length, mitre-shaped, pointed distally; apertural rim narrow; apertural shelf narrow, tapering proxi- mally; hinge line with median bar and low teeth at either end. Operculum (Fig. 234) often preserved in-situ, strongly con- vex; pseudopores elongate, numbering about 20, arranged in an irregular crescent often confined to the proximal half of the operculum. Terminal diaphragms may be present just beneath level of apertural shelf. Intramural buds not observed. Eleozooids unknown, presumed absent. Gonozooids not observed. Measurements. autozooids (10 zooids BMNHD11468) frontal length: frontal width: apertural length: apertural wi
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