Globigerinidae with two or more apertures found in lower to middle Miocene samples from Oamaru and Clifden (New Zealand) are described in terms of rate of expansion of chambers, relation between observed and theoretical diameters for the penultimate chamber, and angle of attachment of the final chamber. In the samples examined the experimental class includes forms usually assigned toGlobigerinoides trilobus(Reuss),G. bisphericusTodd,G. glomerosusBlow,Orbulina suturalisBronnimann, andO. universad'Orbigny.