354 
THE VOYAGE OF H.M.S. CH ALLEN GE R . 
Cyclammina pusilla is a dwarf modification of the typical form. It only attains 
about one-fourth the diameter of fully grown specimens of Cyclammina cancellata, yet 
the test consists of as many convolutions, and the number of chambers in each whorl is 
as large, or sometimes even larger. The thickness of the cancellated walls varies a good 
deal ; sometimes, as in the figured specimen, they are very thin and uniform, and the 
labyrinthic structure amounts to little more than a roughening or reticulation of the 
interior surface. In this condition Cyclammina pusilla furnishes a connecting link with 
the genus Trochammina, one species of which ( Trochammina trullissata ) exhibits a 
similar internal reticulation of the lateral walls, though the septa retain their normal 
compact texture. 
Cyclammina pusilla occurs in company with Cyclammina orbicularis at Station 
323, South Atlantic, east of Buenos Ayres, 1900 fathoms; and Station 153, Antarctic 
Ice-barrier, 1675 fathoms. 
Family Y. TEXTULARIDiE. 
The Textulaeidje constitute a large and very varied group of Foraminifera, but one 
in which the inter-relationship of the constituent types is easily traced. 
The test in its typical condition is represented by an elongated spire, with only a small 
number of segments, usually two or three, in each convolution ; and the numerous and 
diverse modifications which the series includes, are all referable, in one way or other, to 
this primitive structure. 
A tendency to produce dimorphous varieties is manifested in every section of the 
group ; and when this takes place the change in the mode of growth is invariably from a 
more complex to a simpler arrangement of the parts. For example, a dimorphous test of 
which the earlier portion is arranged on the triserial plan finishes with a biserial or 
uniserial line of segments ; one with biserial commencement has the later segments in a 
single row, and so on. 
In the Sub-family Text ul arina; the convolutions are, as a rule, either binary or ternary, 
that is to say, the chambers are arranged in either two or three opposed and alternating 
rows ; and the division into genera is based upon the external conformation of the test 
and the nature of the general aperture. The true Textularice are distinctly biserial, and 
the normal orifice is an arched slit at the inferior umbilical margin of the final segment, 
the latter feature being open to some variation. The genus Cuneolina has likewise a 
biserial test, but it is flattened in the opposite direction, morphologically speaking, to that 
usual amongst the Textularice, the plane of compression being parallel to the plane of 
union between the two series of chambers. The genera Verneuilina, Tritaxia, 
Chrysalidina, and Valvulina are all normally triquetrous, and the first three are 
distinguished by their respective apertures, that of Verneuilina being Textularian in shape 
