LINDSEY—ON GYPSINA PLANA CARTER, AND THE RELATIONS OF THE GENUS 49 
numbers of sponge spicules embedded in it and penetrating it in all directions in exactly 
the same manner as in Polytrema. 
That these are foreign bodies incorporated in some way by the foraminifer and are 
not part of its structure seems reasonably certain, as both the foraminifer and the spicules 
are so typical of their kind. But it is nevertheless singular that these tetraxonid spicules 
seem about the only kind of foreign matter picked up by the foraminifer, and they may 
therefore be of some importance to the animal in the living condition; for it seems probable 
that the spicules were picked up during growth, as they are too large and firmly imbedded 
to have penetrated later by the foraminifer being overwhelmed by the sponge. 
As to the affinities of this foraminifer, there are four genera all among the Rotaliidae 
to which by its general appearance it might belong; these are Planorbulina, Cymbalopora, 
Tinoporus and Gypsina. Planorbulina consists typically of a single layer of chambers, 
spiral in the early stages but more irregular later, the chambers of successive whorls 
alternating with one another and each having an opening at each end close to the line of 
union with the previous whorl. In certain forms there are a number of small chambers 
not arranged in any particular order which cover the surface, but as in the form under 
discussion there are no specialised openings of any kind or any additional chambers on the 
surface, its inclusion in this genus is not possible. 
In Cymbalopora the successive chambers are not closely contiguous and are separated 
by intervals which appear on the under surface as fissures, and each chamber opens 
directly into a central cavity on this underside. Here again the presence of these 
specialised openings renders it impossible to connect the two. 
The original Tinoporus of Carpenter was characterised by the acervuline massing 
of the chambers and by the absence of any specialised mouth or general aperture; in 
some forms there was a supplemental skeleton of spines, &c., in others this was absent. 
It was these latter which Carter in 1877 split off as his new genus Gypsina on 
account of their greater simplicity of form, and it is to this genus that the foraminifer 
under discussion really belongs, as shown by its general appearance, the relative size 
of the foramina and cell walls, together with the absence of any supplemental 
skeleton. 
But it must be confessed that the original description of this genus was rather an 
unsatisfactory one; it was, however, amended by Brady in the Challenger Reports, and 
now reads as follows: 
“Test free or attached, spheroidal or spreading, structure acervuline radiating or 
laminated, chambers rounded or polyhedral; coarsely perforated. No supplemental 
skeleton, no canal system and no general aperture.” 
In the same paper in which this new genus was instituted, Carter points out that a 
foraminifer previously described by him in a paper in 1876 as Polytrema planwm must 
now be included in this new genus under the new name of Gypsina melobesiodes, as it 
was merely a small specimen of a foraminifer with a melobesia-like growth; and the fact 
that this specimen of Carter’s comes from Mauritius and was found coating old coral 
detritus, &c., “like the white saccharine icing on bridecake,” to a very considerable extent 
renders it probable that the material collected by Prof. J. Stanley Gardiner is really 
SECOND SERIES—ZOOLOGY, VOL. XVI. 7 
