. Bulletin of the British Museum (Natural History), Geology. SOUTH AFRICAN GAUDRYCERATDDAE 151 umbilical wall, merging with rounded, convergent flanks. The ventrolateral shoulders are rather abruptly rounded, and the venter somewhat flattened. The shell surface is ornamented by very fine lirae which arise at the umbilical seam, pass straight up the umbilical wall, are markedly prorsiradiate and weakly convex across the flank, flexing gently backwards across the ventrolateral shoulder to cross the venter with a shallow broad peak. There are up to six broad, low, rounded collar-like ribs per who
. Bulletin of the British Museum (Natural History), Geology. SOUTH AFRICAN GAUDRYCERATDDAE 151 umbilical wall, merging with rounded, convergent flanks. The ventrolateral shoulders are rather abruptly rounded, and the venter somewhat flattened. The shell surface is ornamented by very fine lirae which arise at the umbilical seam, pass straight up the umbilical wall, are markedly prorsiradiate and weakly convex across the flank, flexing gently backwards across the ventrolateral shoulder to cross the venter with a shallow broad peak. There are up to six broad, low, rounded collar-like ribs per whorl, running parallel to the lirae, and in front of each is a shallow constriction. Both collar and constriction are covered in lirae. Internal moulds are smooth, save for low swellings, corresponding to the site of collars, and shallow constrictions, rather more prominent than those on the shell surface. Middle growth stages, 30-50 mm. As size increases, the whorl section tends to become as high as wide, and as a result the umbilicus becomes proportionately smaller. The test is ornamented by fine lirae and periodic collars and constrictions as in the early growth stages, but the latter become progressively more closely spaced and distinctly External suture of Anagaudryceras buddha (Forbes). BM(NH) C78721, x 3£ approx. These changes take place at different rates and at different diameters in different specimens, and spacing of constrictions is irregular; there is thus wide intraspecific variability. Mature ornament, 50 mm onwards. Outer whorls and body chamber are ornamented by low, broad, straight, prorsiradiate to gently flexed band-like ribs separated by narrow furrows which are clearly derived from the constrictions present on early and middle growth stages. On the shell, the ribs are typically flattened, with a flattened apertural face so that they appear distinctly scale- like, whilst the whole shell surface bears fine lirae (PI. 10, fig. 1). On the internal mo
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