. Bulletin of the British Museum (Natural History). Zoology . 146 J. R. HAYNES shape, ventral side raised and umbilicate, dorsal side flattened, lobate in last part with slight keel commencing on the penultimate chamber and continuing almost to the base of the apertural face; 12 chambers arranged in a low, dextral trochoid spiral, 6 : 5—, following the proloculus, rapidly increasing in height, oblong—arcuate on dorsal, wedge-shaped on the ventral with apertural face markedly oblique to the periphery; final chamber with large irregular basal flap covering the umbilicus, sutures sli
. Bulletin of the British Museum (Natural History). Zoology . 146 J. R. HAYNES shape, ventral side raised and umbilicate, dorsal side flattened, lobate in last part with slight keel commencing on the penultimate chamber and continuing almost to the base of the apertural face; 12 chambers arranged in a low, dextral trochoid spiral, 6 : 5—, following the proloculus, rapidly increasing in height, oblong—arcuate on dorsal, wedge-shaped on the ventral with apertural face markedly oblique to the periphery; final chamber with large irregular basal flap covering the umbilicus, sutures slightly impressed becoming incised and thickened at the sides with secon- dary calcite in the umbilicus, radial on the ventral side, markedly curved on the dorsal side; wall radial and densely perforated with pores approximately a micron in size, apart from an oval area in the apertural face which includes the umbilical flap; aperture a low slit at the basal suture on the ventral side extending beneath the umbilical flap. Dimensions. Maximum diameter o-8 mm, height 0-32 mm. Approx. diameter of proloculus 25 microns. Material. Three specimens only. Variation. The material is insufficient for proper study of variation and di- morphism. This species is better developed outside Cardigan Bay in St Georges Channel. Juveniles show fewer chambers on the ventral side. Depository. () Slide 1970 : 11 : 26 : 246, 247. Stub 1970 : n : 26 : 55i. Provenance. Described specimen, CB 573. Remarks. Our specimens come close to the type figure of Williamson in their compression, in the character of the umbilical region and in the restriction of the. 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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