LITUOLIDAE gi 



and diatomaceous), we found to our surprise that there was none. Immersions in strong 

 nitric acid under the microscope produced no effervescence, nor did 24 hours' immersion 

 in acid affect the constitution or solidity of the test. It became evident, therefore, that we 

 were not dealing with a Miliolina at all, but with an entirely new organism, for which we 

 proposed the generic name Miliammina (= sandy or siliceous " Milioliform " isomorph). 



Miliammina is evidently closely related to a fossil organism recently described by 

 Cushman and Church (CC. 1929, CFC, p. 502, pi. xxxvi, figs. 10-12) from the Upper 

 Cretaceous of California, under the generic name Silicosigmoilhw . The wall is described 

 as finely arenaceous, with siliceous cement on which the strongest acid makes no im- 

 pression. The chambers are on a sigmoiline plan, and it is apparently isomorphous with 

 Sigmoilina in the porcellanous group, except for its simple aperture which lacks the 

 tooth found in the calcareous genus. It is referred to the Silicinidae, a family established 

 by Cushman in 1928 {tit supra) for the reception of the fossil genera Silicina, Borne- 

 mann, 1874, Rzehakina, Cushman, 1927, Iiwohtina, Terquem, 1862, and Problematina, 

 Bornemann, 1874. In the definition of the family it is stated that the wall is arenaceous, 

 " usually siliceous, sometimes partly calcareous ". Of the four genera, Rzehakina seems 

 to have little in common with the others, but its structural plan is certainly near that of 

 Silicosigmoilina, and its wall is siliceous. To what extent the other genera would with- 

 stand testing with acid we cannot say, but Involutina at least has always been regarded as 

 largely calcareous, and is included by Brady in his sub-family Endothyrinae. 



Miliammina is evidently one of the Lituolidae in Brady's system of classification, but 

 is not easily placed in that family. The sub-family Trochammininae includes many 

 genera, which have little obvious relationship to each other, though all characterized by 

 neatly agglutinate tests. Many of them are isomorphous with other genera of porcel- 

 lanous and hyaline Foraminifera. In this connection it is noteworthy that no true 

 isomorph of that large and important porcellanous sub-family, the Miliolininae, has 

 been known until recently. Miliammina, Silicosigmoilina, and Rzehakina will now to 

 some extent fill this gap, and as they agree in the siliceous constitution of their cement as 

 contrasted with the highly ferruginous cement characteristic of the Trochammininae, 

 we propose to establish a new sub-family of the Lituolidae, " Sihcininae", for the re- 

 ception of these three genera. The Silicininae may be defined as having thin agglutinate 

 tests consisting of numerous chambers, non-labyrinthic, arranged on a milioline plan, 

 and furnished with a terminal aperture, with or without a tooth, the wall composed of 

 minute minerals and Diatoms embedded in an excess of siliceous cement, with smooth 

 or polished exterior, and smooth interior, surfaces. 



Genus Miliammina, ^ Heron-Allen and Earland, 1930 

 Test free, chambers arranged on a triloculine or quinqueloculine plan ; wall imper- 

 forate, composed of very minute mineral fragments embedded in an excess of siliceous 

 cement, smooth or polished, rarely rough. Aperture terminal, furnished with a tooth, 

 perhaps sometimes cribrate. 



1 See note B, Appendix, p. 132. 



