• Globorotalia sp. 4 Jenkins and Orr, 1972, p. 1096, Pl. 18: Figs. 712. 
• Tenuitella sp. Pearson, 1995, p. 53, Pl. 1, Figs. 23-24.
• Tenuitella sp. Norris, 1998, p. 455, Pl. 3, Figs. 7, 11-13, 19-20.

• The specimen illustrated on Plate 2, Figs 2a-c has 5 1⁄2 chambers in the final whorl and a much lower rate of chamber expansion than the holotype. The chamber shape is also noticeably different, with chambers appearing a little more radially compressed on the spiral side, but radially extended on the umbilical side, tapering toward the umbilicus. 
• The specimen illustrated on Plate 2, Figs 3a-c is similar to the holotype in its overall shape. However, the tooth-plate is less well developed and has only a single point, directed toward the antepenultimate suture, and the aperture is higher and more arched. 
• The specimen on Plate 2, Figs 4a-c has a lower trochospiral than the holotype. The chambers of the final whorl are dorsally inflated, such that the proloculus is situated in a dorsal ‘‘umbilicus’’ rather than near the apex of the test as in the holotype. The aperture extends past the periphery and slightly onto the spiral side. The tooth-plate is correspondingly elongate and irregular. 
• The specimens on Plate 2, Figs. 5 and 6 have been deliberately broken to reveal the morphology of the earlier chambers. Each has four chambers in the early whorl and an extraumbilical foramen with a pronounced flaring lip. The chamber shape and arrangement are similar to the supposed ancestor, Globigerinita glutinata (see below), but the aperture is more extraumbilical than is typical for that taxon. 
• The specimen on Plate 2, Fig. 7 shows a very pronounced triangular tooth bordered by a thin lip and an irregular penultimate chamber. Those on Plate 2, Fig. 8 and Plate 3, figs. 1-4 illustrate a feature that is commonly encountered in this species, namely a composite toothplate. This is a complex structure, having been formed by the superimposition of the tooth of the final chamber onto the tooth of the penultimate chamber. The final tooth-plate is not in contact with the preceding tooth-plate along its entire length, but arches on to it, leaving an aperture on the posterior side, which connects directly with the primary aperture. The structure thus formed is similar to that seen in some species of the unrelated Cretaceous genera Ticinella and Rotalipora. 
• The specimens on Plate 3, Figs 1-4 also further illustrate the variation in test shape and apertural modification in the species. Some of them have small circular pits of unknown origin on the test surface. The specimen on Plate 3, Fig 4a-c shows a series of beaded calcite deposits on the sutures, which probably cover small supplementary apertures similar to the bullae sometimes seen in Globigerinatella insueta (see, for example, Pearson, 1995, Plate 2, Fig. 8). This specimen also has a curious long slit-like supplementary aperture on the spiral side beneath the final chamber, with an irregular tooth-plate like covering. This structure is clearly allied to the primary aperture and toothplate, but does not visibly connect on the outside of the test. The double-aperture is similar to the structure seen occasionally in various planispiral planktonic foraminifera, such as Eocene Pseudohastigerina, and has been observed on a number of specimens of Mutabella. A further spiral aperture which has a more rounded shape occurs beneath the penultimate chamber. 
• Many of the specimens discussed above have a tendency towards a more planispiral coiling mode, at least with respect to the final whorl. Some specimens are almost axially symmetric and biumbilicate in appearance, such as that shown on Plate 3, Fig. 5. In specimens such as this, the tooth-plate tends to be much reduced, constituting a more regular apertural lip. Note also the supplementary sutural apertures of this specimen. 
• The specimen on Plate 3, Fig. 6 shows an enlargement of the apertures on another, peeled specimen showing that when well-formed, they tend to be circular and bordered by a regular lip, as seen in Globigerinatella insueta. 
• Further specimens are shown on Plate 4, Figs. 1-4. The specimen on Plate 4, Fig. 3 shows an areal aperture with a pronounced lip on the final chamber. This is a rare but not unique feature of M. mirabilis. Other specimens on the plate show an approach in morphology to Globigerinita glutinata (specimens of which are shown in Plate 4, Figs 8-10) in the early part of the stratigraphical range of M. mirabilis.

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