Kennett & Srinivasan (1983):
The height of the spire in B. digitata shows considerable variation with growth of the individual. There is a tendency toward streptospiral coiling in adult test, suggesting
an affinity with Hastigerinella.
B. digitata developed from B. praedigitata, from which it differs in having the radially elongate chambers.
Bolli & Saunders (1985):
Banner 2-4; Blow (1960b) described Beella as a subgenus of Globorotalia. Blow (1965) treated it as a subgenus of Globigerina; here it is given full generic rank. Characteristic of the species is the highly trochospiral arrangement, in particular of the chambers forming the early whorls, and the gradually more pronounced elongation of the chambers in the last whorl, with the last chamber becoming quite distinctly pointed. Fully grown specimens with strongly elongate chambers in the last whorl are comparatively rare. More frequent are smaller specimens consisting of the highly trochospiral earlier portion and with the last chambers becoming only slightly elongate. Such forms were included by Parker (1967) in her Globigerina praedigitata. In digitata cf. digitata Blow (1969) placed specimens 'which show the distinct radial elongation of the last two chambers, but which do not have the distinct pointed conical termination' (as in the neotype specimen of digitata).
According to Banner 2-4; Blow the position of the aperture is'interiomarginal, umbilical extraumbilical, ventral throughout ontogeny'. In most specimens examined by us the position of the aperture appears virtually umbilical, with only occasionally a trend towards a more peripheral, extraumbilical position. In rare cases, such as in Brady (1884, pt. 8, fig. 8) the aperture even extends beyond the periphery onto the spiral side. Parker (1967) observed praedigitata, first in Zone N 17 (Late Miocene, Globorotalia humerosa Zone), with the position of its real first appearance left uncertain. Blow (1969) quotes its range from either latest N 16 or earliest N 17 to within N 21 (Middle Late Pliocene), and for his cf. digitata from within middle part of N 21 (Late Pliocene) to within N 22 (within Early Pleistocene), whereas he quotes the subspecies digitata originally described from the Holocene - as ranging from N 22 to N 23, i.e. throughout the Pleistocene to Holocene.
Observations on DSDP material from Caribbean sites indicate that praedigitata and cf. digitata types continue to be present as immature growth stages of digitata throughout the Pleistocene and Holocene.
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Banner,F.T. and Blow,W.H. (1960): The taxonomy, morphology and affinities of the genera included in the subfamily Hastigerininae . Micropaleontology Vol. 6 p. 19-31
Kennett,J. and Srinivasan,M.S. (1983): Neogene Planktonic Foraminifera - A Phylogenetic Atlas.
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Chaisson,W.P. and d'Hondt,S.L. (2000): Neogene planktonic foraminifer biostratigraphy at Site 999, Western Caribbean Sea. In: Proceedings of the Ocean Drilling Program, Scientific Results Vol. 165 Eds: Leckie, R.M.Sigurdsson, H.Acton, G.D.Draper, G. p. 19-56
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