. Bulletin of the British Museum (Natural History). . inconspicuous and are usually abraded. They have a longi- tudinally elliptical shape with a minute ooeciopore. Measurements. TAM (top of ridges), 0-10-0-12 mm; TAM (sides of ridges), 0-06-0-08 mm; GDL, c. 1-0 mm; GW, c. 0-75 mm. Remarks. This is a very common and distinctive species at Faringdon. Colonies are often found encrusting quartzose or claystone pebbles ( Fig. 30), but may also occur on bivalve shells and sometimes on brachiopods and echinoid spines. Wilson (1986) interpreted R. hagenowi as being well- adapted to the
. Bulletin of the British Museum (Natural History). . inconspicuous and are usually abraded. They have a longi- tudinally elliptical shape with a minute ooeciopore. Measurements. TAM (top of ridges), 0-10-0-12 mm; TAM (sides of ridges), 0-06-0-08 mm; GDL, c. 1-0 mm; GW, c. 0-75 mm. Remarks. This is a very common and distinctive species at Faringdon. Colonies are often found encrusting quartzose or claystone pebbles ( Fig. 30), but may also occur on bivalve shells and sometimes on brachiopods and echinoid spines. Wilson (1986) interpreted R. hagenowi as being well- adapted to the physically rigorous habitats afforded by the exteriors of claystone pebbles in the Red Gravels. However, the robust construction of the colonies may also have contri- buted to their occurrence in this habitat. Indeed, many specimens of R. hagenowi evidently survived extensive abra- sion, probably post-mortem, which often resulted in trunca- tion of the ridge crests. Genus IDMONEA Lamouroux, 1821. Type SPECIES. Idmonea triquetra Lamouroux, 1821, by mono- typy; Bathonian, Normandy (see Mongereau & Walter 1965; Walter 1970). Remarks. Idmonea has been used by Mesozoic palaeonto- logists in a way different from neontologists. The latter have commonly referred erect tubuloporine species with branches of a subtriangular cross section to this genus (but cf. Harmelin 1976). However, the Jurassic type species is a tubuloporine with encrusting branches, subtriangular in cross section and with a selvedge of kenozooecia which does not coalesce with that of other branches to form a continous sheet (cf. Repto- clausa). 'Adventitious' branches sometimes originate from the kenozooecial selvedge. From the encrusting base erect branches may arise, having an ovoidal cross-sectional shape with autozooecial apertures opening on one side of the branch and kenozooecia on the other. These erect branches. Please note that these images are extracted from scanned page images that may have been digital
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