Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum . mkwelanense (Crick, 1907). SAS-Z975. Atypicalbody chamber fragment lacking well-defined umbilical tubercles, x 0,6. by Schluter (1876, pi. 6 (fig. la-b)) as Ammonites texanus belongs to P. (1948: 72) has, however, rather convincingly demonstrated that doubtexists as to the conspecificity of the two specimens. This thus leaves us with asingle specimen on which to interpret P. zeilleri. P. zeilleri seems to differ mainlyin having a slightly wider umbilicus (c. 47% according to De Grossouvresfigure) an
Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum . mkwelanense (Crick, 1907). SAS-Z975. Atypicalbody chamber fragment lacking well-defined umbilical tubercles, x 0,6. by Schluter (1876, pi. 6 (fig. la-b)) as Ammonites texanus belongs to P. (1948: 72) has, however, rather convincingly demonstrated that doubtexists as to the conspecificity of the two specimens. This thus leaves us with asingle specimen on which to interpret P. zeilleri. P. zeilleri seems to differ mainlyin having a slightly wider umbilicus (c. 47% according to De Grossouvresfigure) and lacking the prominent development of the umbilical tubercle. CRETACEOUS FAUNAS FROM SOUTH AFRICA 43 Without having been able to examine De Grossouvres original specimen, theauthors are hesitant in referring the Zululand material to P. zeilleri, and preferto refer it to P. umkwelanense. The specimen referred to as Mortoniceras aff. umkwelanense by Spath(1921: 234, text-fig. D2) is definitely not a Paratexanites, but a good example ofPlesiotexanites to be described Fig. 30. Paratexanites umkwelanense (Crick, 1907). NMB-D1060. Bodychamber fragment, x 0,6. 44 ANNALS OF THE SOUTH AFRICAN MUSEUM P. umkwelanense is possibly derived from Paratexanites australis sp. or via P. orientalis (Yabe), through becoming quadrituberculate at anearlier stage and in acquiring a more inflated whorl section. Similarities betweenP. australis and P. umkwelanense are striking, as far as the strong developmentof ornament in the relatively early stages of growth, the undulating keel, andfaint reticulate pattern on the venter are concerned. P. orientalis differs from P. umkwelanense mainly in having a more depressedwhorl section in early stages of growth and less strongly developed adult whorl section of P. orientalis (see Matsumoto 1970: 254, fig. ll(85)b),however, is very similar to that of P. umkwelanense, suggesting possible geneticrelationships. In the latter respec
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