. Bulletin of the British Museum (Natural History), Geology. 138 BANNER, SIMMONS&WHITTAKER. Figs 73-74 Pseudomarssonella bipartita Redmond, from Saudi Arabia, Aramco Well T 61, 80-90 ft depth, Middle Dhruma Formation, mid or late Bathonian. Figs 73a-b, holotype AMNH FT-1265; a, axial view (length 440 urn), x 140; b, terminal view, x 140. Figs 74a-c, paratype AMNH FT-1266; a, axial view (length 560 urn), x 110; b, terminal view, x 140; c, apertural area, x 325. Remarks. The difference in tapering angles between the holotype (Fig. 73a) and paratype (Fig. 74a) cannot be ascribed to structural
. Bulletin of the British Museum (Natural History), Geology. 138 BANNER, SIMMONS&WHITTAKER. Figs 73-74 Pseudomarssonella bipartita Redmond, from Saudi Arabia, Aramco Well T 61, 80-90 ft depth, Middle Dhruma Formation, mid or late Bathonian. Figs 73a-b, holotype AMNH FT-1265; a, axial view (length 440 urn), x 140; b, terminal view, x 140. Figs 74a-c, paratype AMNH FT-1266; a, axial view (length 560 urn), x 110; b, terminal view, x 140; c, apertural area, x 325. Remarks. The difference in tapering angles between the holotype (Fig. 73a) and paratype (Fig. 74a) cannot be ascribed to structural differences between the megalospheric and microspheric generations because the tapering angles of the initial parts of the tests are the same. In each case, also, the number of chambers per adult whorl is the same. There- fore, the difference must be due to an increased rate of growth (in the case of specimens like the holotype) during ephebic ontogeny, while in others (like the figured para- type) the chamber-enlargement rate remained constant or even diminished. This could have resulted from palaeoeco- logical differences and, therefore, would not have been inherited. The specimen figured as P. bipartita by Delance & Ruget (1989) is referred by us to Redmondoides medius (Redmond) (p. 120). Figs 75-77 Pseudomarssonella plicata Redmond. Figs 75-76, primary types; from Saudi Arabia, Aramco Well T 60A, 10-20 ft depth, basal Upper Dhruma Formation ( 'Atash Member), late Bathonian or early Callovian. Figs 75a-b, holotype AMNH FT-1275; a, axial view (length 410 urn), x 160; b, initial view, x 270. Figs 76a-c, paratype AMNH FT-1276; a, axial view (length 350 urn), x 200; b, terminal view, x 290; c, lateral view of apertural area, x 450. Figs 77a-b, holotype AMNH FT-1279 of the synonymous P. reflexa Redmond, from Saudi Arabia, Aramco well 4A, 4875 ft depth. Middle Dhruma Formation, early Bathonian; a, terminal view, x 150; b, axial view (length 560 um), x Please note that t
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