. Bulletin of the British Museum (Natural History). Zoology . i78 J. R. HAYNES side and subangular periphery. The initial part is like Cibicides for about two whorls and is followed by about six irregular whorls of chambers finally arranged in alternating rings (megalospheric form). The chambers tend to be almost square at first in dorsal view, up to three times as long as high later. Description. (PL 20, fig. 11, account of pores and apertures on the dorsal side based on additional specimen PI. 20, fig. 12.) Test presumed originally attached, plano-convex with raised, partially i
. Bulletin of the British Museum (Natural History). Zoology . i78 J. R. HAYNES side and subangular periphery. The initial part is like Cibicides for about two whorls and is followed by about six irregular whorls of chambers finally arranged in alternating rings (megalospheric form). The chambers tend to be almost square at first in dorsal view, up to three times as long as high later. Description. (PL 20, fig. 11, account of pores and apertures on the dorsal side based on additional specimen PI. 20, fig. 12.) Test presumed originally attached, plano-convex with raised, partially involute ventral side and flat, evolute, dorsal side, roughly pentagonal in outline, periphery semi-lobate, subangular; all the cham- bers visible on the dorsal side commencing with 14 arranged in a low, trochoid spiral of about 2\ whorls, these being followed by about 30 chambers arranged in rings, the rings at first irregular but finally of regular alternations of five chambers each, chambers increasing slowly but irregularly in size, becoming longer than high and slightly overlapping, septa limbate but flush; alternating rings of chambers of the last part clearly seen in ventral view, inflated and overlapping with impressed sutures, some with irregular, flap-like extensions along the sutures between previous chambers; wall radial, composite lamellar, densely perforated by pores between 1-2 microns in diameter and widening to the surface on the ventral side, up to 4 microns in diameter with interleaved sieve plates on the dorsal side (there is a tendency for the distance between the pores to be about double their diameter); aperture multiple, small openings about 15 microns in diameter, with lips, each chamber with two at the periphery and two at the dorsal basal suture, lips tending to become tubular extensions, apertures also developed on the flaps along the sutures on the ventral side. Dimensions. Maximum diameter o-66 mm. Material. More than 25 mm Fig.
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