Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum . Fig. 21. Paratexanites umkwelanense (Crick, 1907). A. Partial suture of Whorl sections of SAS-36/3239 and SAS-Z967. All x 1. CRETACEOUS FAUNAS FROM SOUTH AFRICA 35 jwy%^. Fig. 22. Paratexanites umkwelanense (Crick, 1907). SAS-36/3238. Showing inner whorls to illustrate early ontogeny. diameter of c. 30 mm. After this, ornament becomes very robust, with strong,single ribs connecting radially elongated umbilical tubercles, displaced some-what up the flanks, to strong, spinose ventrolateral spines leaning a
Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum . Fig. 21. Paratexanites umkwelanense (Crick, 1907). A. Partial suture of Whorl sections of SAS-36/3239 and SAS-Z967. All x 1. CRETACEOUS FAUNAS FROM SOUTH AFRICA 35 jwy%^. Fig. 22. Paratexanites umkwelanense (Crick, 1907). SAS-36/3238. Showing inner whorls to illustrate early ontogeny. diameter of c. 30 mm. After this, ornament becomes very robust, with strong,single ribs connecting radially elongated umbilical tubercles, displaced some-what up the flanks, to strong, spinose ventrolateral spines leaning against theumbilical wall or, in poorer preservation, prominent rounded nodes. Separationof the ventrolateral tubercle occurs in SAM-PCZ5694 (Fig. 23) at a diameterof 55 to 65 mm. At diameters of c. 100 mm the submarginal, marginal, andexternal rows of tubercles are equidistant. The keel is undulating in all thespecimens. In some specimens the undulations are so prominent as to create theappearance of a central row of tubercles. In addition, low swellings may connectthe external tubercles spirally and across the venter, producing a reticulate effecton the venter as in SAS-Z967 (Figs 24-26) and SAS-H199/8 (Fig. 27). Ornament remains basically the same thr
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Keywords: ., bookcentury1800, bookdecade1890, booki, booksubjectnaturalhistory
