50 PERCY SLADEN TRUST EXPEDITION 
the same thing. But neither under its old name of Polytrema plana nor its new one of 
Gypsina melobesiodes is the description really clear. 
As no figures were given in the later paper and those in the former were of specimens 
41-inch in diameter, no real idea of the structure is obtaimable, and further, as the series of 
canals shown in the original figure and described in the original description as the 
distinguishing feature of the foraminifera were in the later paper shown to be non- 
existent, the name G'ypsina plana (or melobesiodes) seems to be nothing more definite 
than a name, and hence it is proposed to apply it to the specimens under discussion as 
being in all probability the correct identification of at any rate the Mauritius specimens. 
Of the two specific names, however, “plana” must take precedence over the more 
suitable ‘“melobesiodes.” Except that the difference in size of the chambers in the 
Amirante and Providence specimens makes them look more heavily built than the ones 
from Mauritius, and that in the material under observation these latter incrustations were 
much larger in size, there is no real difference in structure. Further, as both the size 
of the chambers and the size of the mass vary considerably in the material from the same 
districts, there seems no reason for making three species of them, and hence all must now 
be known as Gypsina plana. 
It also seems probable that an unidentified specimen from the West Indies in the 
Halkyard Collection of Foraminifera in the Manchester Museum belongs to this species ; 
the size of the chambers is rather smaller, being only 70—80 p, but it grows to the extent 
of an inch or more over the surface of a shell of Strombus gigas, and is therefore 
considerably larger than any other known Gypsina. If this specimen does really belong 
to this species, it would seem to have a fairly wide distribution both in space and depth. 
As reference has been made several times to the relatively large size of Gypsina 
plana, it is perhaps advisable to have a few measurements of other forms of Gypsina 
to compare with it. Carter gives no measurements at all of his type Gypsina 
vesicularis, and only outside measurements (2°3 inches) of G. plana, nor are any to be 
found elsewhere (except indirectly, as when the “Challenger” figures are said to be 
magnified 30—40 times), but all are of small size, not bemg more than a millimeter 
or so in outside diameter. No measurements of the areolz are to be found, but in the 
specimens in the Halkyard Collection which were measured, the following seem to be 
about the average sizes. (For convenience in comparison the measurements of the present 
material are given also) : 
G. plana, Mauritius as as ... 90—230 p 
Re Providence aS: bee ... 80—150p 
re Amirante site re .. 49—115 p 
ie W. Indies Ae ae ... 70— 80p 
G. unherens, Guernsey... a3 .. 70— 90p 
G. vesicularis, Naples an a ... 380— 48p 
G. globulus ... aye : 20— 28 p 
So that, though the difference in size of the anoolae between G. globulus and 
G. plana Mauritius is great, G. inherens leads up to it through the Amirante and 
Providence specimens, the whole forming a gradual series. 
