Figure 28: Reproduction of the original illustrations of Helicostegina gyralis from Barker & Grimsdale (1936). 1 (Pl. 34, fig. 2), equatorial section. 2 (Pl. 34, fig. 3) section cut on ventral side of the equatorial plane showing ventral sheet of chamberlets. 3 (Pl. 34, fig. 6), equatorial section. 4 (Pl. 32, fig. 4) axial section. 5 (Pl. 32, fig. 5) axial section. Note that in 4 the ventral chamberlets extend into the periphery of the test, whereas in 5 they do not. Guayabal Formation, Jenny Section No. 1573, 11 km southeast of Sabaneta, state of Veracruz, Mexico. Scale bar = 1 mm.