Figure 10. Whole rock thin section from yellow limestone showing a number of sections of Grzybowskia jasoni roughly parallel to the axis of coiling. The completely involute nature of the tests is visible. The resemblance of the juvenile part of the test to Palaeonummulites can be seen, lasting until the increasing height of the whorls forms a flange with slightly concave sides. In the central specimen the gerontic stage is distinguishable by its great whorl height, flat and thinner lateral walls and multiple subdivisions. Thin section FFC 3A. The maximum dimension of the largest (central) test is 4.71 mm. Flying Fish Cove, Christmas Island.