No. IV.—ON GYPSINA PLANA, CARTER, AND THE RELATIONS OF 
THE GENUS. 
By Marsorie Linpsey, B.Sc., The University, Manchester. 
(Text-figures 1—6.) 
(CommuntcateD BY Pror. J. Stanrey Garpiner, M.A., F.RS., F.LS.) 
Read Ist May, 1913. 
In the collections made by Prof. J. Stanley Gardiner in the Indian Ocean in 1905 
specimens of a Foraminifer were obtained from Mauritius* (> 100 fathoms), Amirante 
(25 fathoms) and Providence (50—78 fathoms) which have acquired a fixed mode of 
existence to an extraordinary degree. 
They form irregular spreading masses over any object on which they happen to grow, 
generally old coral detritus, Polytrema, sponges and polyzoa—in short, on pretty nearly 
any kind of decayed calcareous matter. 
The most striking feature of this foraminifer, in addition to its encrusting habit, is 
its extraordinary size, not only of the mass as a whole, but to a certain extent also of the 
individual chambers. The specimens reach in some cases (e.g. those from Mauritius) three 
or four inches diameter in their widest parts and they may spread until they completely 
surround the decayed matter on which they are growing. 
This incrustation is not simply a uniformly thin layer, but grows out into projections 
forming an irregular series of knobs all over the surface. 
The spirit material is of a pink colour, but it goes white on drying. 
When magnified the surface+ is seen to consist of numbers of chambers arranged 
more or less regularly with well defined walls separating them, giving it the appearance of 
being divided into areolse, each roughly circular in shape and each perforated by a few 
large foramina. These areole vary in size in the specimens from different localities, but 
are largest in those from Mauritius, and these specimens, on account also of the larger 
size to which the mass as a whole grows, have been mainly used for working on. Here 
the areole vary from 90—233 », but an average chamber is somewhere about 120 in 
diameter. 
The areole are separated by grooves about 5» wide, which represent the walls. 
The perforations are not very numerous and are from 10—20 in each areolz, each 
being 5—7 p in diameter. 
* See “Description of the Expedition,” Trans. Linn. Soc. Ser. 2, Zool., xii. (1907), p. 122. 
tT For a figure of a similar surface see Challenger Report, ix. plate 102. 
