Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum . Fig. 52. Plesiotexanites stangeri (Baily, 1855). A. Whorl section of holotype BMNH-C73333,after Matsumoto (1970, text-fig. 23(97)A). B. Whorl section of var. sparsicosta, BMNH-C73333, after Matsumoto (1970, text-fig. 23(97)B). C. Partial suture of BMNH-C19444, after Spath (1921, fig. D-la). which is already developed at a diameter of 7,5 mm. These tubercles are joinedto the bases of the large ventrolateral nodes by low, broad connections. Theyare not aligned with the ventrolateral (3+4) and umbilical (1) tubercles, bu
Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum . Fig. 52. Plesiotexanites stangeri (Baily, 1855). A. Whorl section of holotype BMNH-C73333,after Matsumoto (1970, text-fig. 23(97)A). B. Whorl section of var. sparsicosta, BMNH-C73333, after Matsumoto (1970, text-fig. 23(97)B). C. Partial suture of BMNH-C19444, after Spath (1921, fig. D-la). which is already developed at a diameter of 7,5 mm. These tubercles are joinedto the bases of the large ventrolateral nodes by low, broad connections. Theyare not aligned with the ventrolateral (3+4) and umbilical (1) tubercles, but aredisplaced somewhat forward. The external tubercles are very variable, sometimesbeing elongated spirally to such an extent as to form discontinuous lateral keels(Fig. 54E-F). In the second stage, the ventrolateral tubercles begin to separate into two 72 ANNALS OF THE SOUTH AFRICAN MUSEUM A. Fig. 53. Plesiotexanites stangeri (Baily, 1855). A. SAS-Z1971. One of the two specimens of the species thus far found in the False Bay region of Zululand. B-C. SAM-K5889. Juvenile specimen showing pseudotricarinate inner whorls, x 1. different rows through the spUtting off on the ventral side of a new row, thoughstill connected by a common base (Fig. 54A-C). This is the Parabevahites increasing diameter the inner of these two rows migrates dorsad from thespiral suture to complete the separation of the two rows. This is the Para-texanites stage. In the third stage of development, faint indications of the lateral (2) tuberclestart appearing near the dorsal third of the flanks. The moment of appearanceand the strength of these lateral tubercles are very variable. On the later part of the phragmocone, and on the body chamber, whichconsists of one whorl on the holotype (Figs 50-51), bifurcations cease andribbing becomes single. The whorl section becomes progressively inflatedand
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Keywords: ., bookcentury1800, bookdecade1890, booki, booksubjectnaturalhistory
