Published:August 01, 1980
Fabric and mineralogical studies of the test of a modem benthic foraminiferal species, recovered from several widely spearated locations in the Pacific and off Antarctica, have shown it to be constructed of opal precipitated by the foraminifer. Although microarchitecture and gross morphology of the siliceous test is similar to that in miliolid foraminifera, its mineralogy and structural details preclude assignment to any of the available taxa within the Order Foraminiferida. A new suite of taxa of suborder and lesser rank is proposed to accommodate this new form, which has been designated Silicoloculina profunda, n. gen, n. sp.
The genus Hemisphaerammina is a senior synonym of Daitrona. A detailed scanning electron microscopic and transmission electron microscopic study was conducted on the test, the cytoplasm (ectoplasm and endoplasm), and the nucleus of the species H. bradyi.
The arenaceous test has a calcareous cement. Both sides of the test show a very different composition. The differentiation between the outer side, with coarse particles and little cement, and the attached side, with fine particles and abundant cement, results from the selective choice of agglutinated particles. This selection probably occurs at the ectoplasm level.
In contrast to the simple and rather primitive organization of the test, the endoplasm and nucleus show a complex ultrastructure, which is as complex as that of advanced calcareous foraminifera.