. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum . ghtly toward the relatively broad, flattened venter. Costally the whorl section ispolygonal slightly higher than wide, with a weakly concave venter; intercostally it isbroadly ovate and compressed (H/W = ) (Fig. 20A, E), becoming more inflatedwith growth. Part of the poorly preserved suture is illustrated as Figure 30. Ornament, especially the strength of tuberculation and ribbing, is variable. There areabout 13 umbilical bullae per whorl on the best preserved specimen, but their strengthvaries and not all
. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum . ghtly toward the relatively broad, flattened venter. Costally the whorl section ispolygonal slightly higher than wide, with a weakly concave venter; intercostally it isbroadly ovate and compressed (H/W = ) (Fig. 20A, E), becoming more inflatedwith growth. Part of the poorly preserved suture is illustrated as Figure 30. Ornament, especially the strength of tuberculation and ribbing, is variable. There areabout 13 umbilical bullae per whorl on the best preserved specimen, but their strengthvaries and not all ribs develop bullae. Not uncommonly there is a weak arcuate bullabetween main bullae, unconnected to a rib. The main umbilical bullae give rise to fairlythick low ribs. These are adorally convex across the flank, weak at midflank, andseparated by up to three intercalatories. Main ribs are ornamented with inner and outerventrolateral tubercles, although the latter tend to be irregular in strength and UPPER CRETACEOUS (TUROXIAX-COXIACIAX) AMMOMTESEROMSAO SICOLAU, AXGOLA 125 ?. Figure 20 Whorl sections, x 1. A. E. Morrowites mocamedensis (Howarth). A. SAM-PCA1885: E. SAM-PCA1888. B-C. Placenticeras kajfrarium Etheridge. B. SAM-5106; C. SAM-6523. D. Prionocycloceras carvalhoi (Howarth). SAM-PCA1896. development. From the inner ventrolateral tubercles the ribs project forwards to connectwith outer ventrolateral tubercles close to the siphonal line and are weakly joined acrossthe venter. There is a multiplicity of outer ventrolateral tubercles, unconnected to ribs, sothat on SAM-PCA1892 15 outer ventrolateral tubercles correspond with only sevenlower ventrolateral tubercles (Fig. 21). Occasionally an inner ventrolateral tubercle lacksan accompanying upper ventrolateral. That the inner ventrolateral tubercles represent theseptate bases of hollow spines is evident from SAM-PCA1892; this specimen preserves13 short, stubby, backwardly directed spines per half whorl impressed in the umbil
Size: 1615px × 1547px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, booki, booksubjectnaturalhistory
