Bolli (1957):
Sphaeroidinella grimsdalei is rather variable in size and in number of chambers comprising the final whorl. Stratigraphically early specimens are usually small with 3 chambers in the last whorl. During the course of evolution, the tests tend to become larger and the last whorl may consist of 3 and 4, occasionally even 5 or 6, chambers. Sphaeroidinella rutschi Cushman and Renz probably branched off from Sphaeroidinella grimsdalei. An apparently transitional form is shown on plate 26, figures 13a, b (USNM P5646). |
Cushman,J.A. and Stainforth,R.M. (1945): The foraminifers of the Cipero Marl Formation of Trinidad, British West Indies . Journal of Foraminiferal Research Vol. 14 p. 1-75
Keijzer,F.G. (1945): Outline of the geology of the eastern part of the province of Oriente, Cuba (E. of 76° W.L.), with notes on the geology of other parts of the island.. , Geographische en Geologische Mededelingen, Physiographisch-Geoloogische Reeks Ser II Vol. 6 p. 1-239
Bermudez,P.J. (1949): Tertiary smaller foraminifers of the Dominican Republic . Spec. Publ.Cushman Lab. Foraminiferal Res., Vol. 25 p. 1-322
Bolli,H.M. (1957): Planktonic foraminifera from the Oligocene-Miocene Cipero and Lengua formations of Trinidad, B.W.I.. In: Studies in Foraminifery, Bulletin of the U.S. National Museum Vol. 215 Eds: Loeblich, A.R.Tappan, H.Beckmann, J.P.Bolli, H.M.Gallitelli, E.M.Troelsen, J.C. p. 97-123
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