Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum . Fig. 221. Menabites {Australiella) australis (Besairie, 1930). 1. Changes in whorl section during ontogeny. (See also Figs 222-229.) CRETACEOUS FAUNAS FROM SOUTH AFRICA 295 Coiling is relatively loose with an umbilical width of the order of 35 to40 per cent of the diameter. The whorl section and details of ornament changecontinually through the ontogeny (Figs 221-229). Unfortunately, none of the specimens has the very innermost whorlspreserved, but at a diameter of c. 80 mm, the whorl section is already d
Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum . Fig. 221. Menabites {Australiella) australis (Besairie, 1930). 1. Changes in whorl section during ontogeny. (See also Figs 222-229.) CRETACEOUS FAUNAS FROM SOUTH AFRICA 295 Coiling is relatively loose with an umbilical width of the order of 35 to40 per cent of the diameter. The whorl section and details of ornament changecontinually through the ontogeny (Figs 221-229). Unfortunately, none of the specimens has the very innermost whorlspreserved, but at a diameter of c. 80 mm, the whorl section is already distinctlyrectangular, much wider than high, with a very shallow dorsal zone of impres-sion, little inflated, virtually parallel flanks and a slightly rounded venter(Fig. 227). Ornament at this stage consists of small, conical umbilical tubercles,connected in most cases by low, thick ribs to enormous bullate to spatulateventrolateral nodes, which in turn are connected by very indistinct riblets totwo or three rounded or obliquely elongated external tubercles. Some of theum
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Keywords: ., bookcentury1800, bookdecade1890, booki, booksubjectnaturalhistory
