REPORT ON THE EORAMINIEERA. 
435 
surface of the early segments also beset with stout spines or tubercles. Aperture large, 
curved ; placed obliquely in a depression on the inflated distal end of the terminal seg- 
ment, which is ornamented externally with radiating lines. Length, J^rd inch (077 mm.). 
Ehrenbergina hystrix differs from its congeners in the spinous condition of the lateral 
faces of the test, and in its large inflated final segment. 
It is a rare deep-water species, and has only been found hitherto at four points 
in mid-ocean in the South Pacific, namely: — Station 179, depth, 2325 fathoms; Station 
271, depth, 2425 fathoms; Station 280, depth, 1940 fathoms; and Station 283, depth, 
2075 fathoms. 
Family VI. CHILOSTOMELLID^J. 
The Family Chilostomellida embraces the three genera Chilostomella, Allomorphina, 
and Ellipsoidina, and is equivalent therefore to Reuss’s Family Cryptostegia, with the 
addition of the genus Ellipsoidina. It is represented for the most part by organisms of 
very rare occurrence, either in the recent or fossil condition, and until comparatively 
recently was supposed to comprise only a few fossil species of Cretaceous and 
Tertiary age. 
The shelly skeleton of the Chilostomellida: is invariably calcareous and perforate, 
and usually thin and transparent. The structural and morphological relations of the 
group are best understood by reference to the typical genus Chilostomella. This genus 
presents a uniaxial test, the chambers of which are put on alternately at the two ends, each 
segment almost completely enclosing the previous one, their point of attachment to each 
other being at one side of the shell. The aperture is at the margin of the last segment 
on its ventral side. In Allomorphina the segments alternate in ternary instead, of binary 
series. As these two genera have still-living representatives, their characters will 
presently be noticed in greater detail. 
In Ellipsoidina the arrangement is somewhat different. The chambers are elliptical 
and each larger than its predecessor, as in Chilostomella ; but their point of attachment 
instead of being at one side, is at the base, and they are all projected symmetrically in 
one direction, instead of being directed alternately towards the two ends. The aperture 
is always at the distal extremity, and takes the form of an arcuate or nearly circular slit, 
either entire, or more commonly divided by shelly bridges. From the centre of the 
superior end of each segment, that is to say, either from the space enclosed by the curved 
aperture or its immediate neighbourhood, rises a shelly column of sufficient length to 
reach to the top of the succeeding chamber. This column is an anomalous feature, to 
which there is nothing precisely analogous amongst other Foraminifera. It was originally 
supposed to be a tubular neck serving for the aperture, and the genus was on that account 
