274 
THE VOYAGE OE H.M.S. CHALLENGER. 
Aschemonella ramuliformis occurs in the two localities at which the typical species is 
most abundant, namely, Station 244, in the deep area of the North Pacific, 2900 
fathoms, and Station 323, in the South Atlantic, east of Buenos Ayres, 1900 fathoms ; and 
fragments have also been found in the material dredged at Station 272, in the South 
Pacific, a little south of the equator, 2600 fathoms. 
Rhizammina, H. B. Brady. 
Rhizammina , Brady [1879], 
Test free, tubular, simple or branching, flexible ; texture chitino-arenaceous, more or 
less rough externally. 
The characteristic feature of the genus Rhizammina is its chitinous or chitino- 
arenaceous investment ; or, in other words, the large excess of organic over inorganic 
constituents in the composition of the test. The flexibility of the long tubular body 
distinguishes it from the more strictly arenaceous types such as Hyperammina, in which 
the walls are composed almost exclusively of inorganic materials so firmly cemented that 
the slenderest specimens are rigid and non-elastic. 
The minuter characters of the investment have been worked out, chiefly in connection 
with Rhizammina algceformis, owing to the plentiful supply of that particular form 
obtained at one of the Challenger Stations ; but so far as the structure and composition 
of the test are concerned, the description of the branched variety applies equally to the 
unbranched forms, and is to this extent an epitome of generic characters. 
Rhizammina algceformis, H. B. Brady (PI. XXVIII. figs. 1-11). 
Rhizammina algceformis , Brady, 1879, Quart. Journ. Micr. Sci., vol. xix. N. 3., p. 39, pi. iv. figs. 
16, 17. 
Test free, tubular, branching dichotomously, flexible, forming tangled weed-like 
tufts of indefinite size. Texture chitino-arenaceous, rough externally ; colour of the tube 
when free from incrustation, brown. 
Amongst the doubtful microscopic organisms which have from time to time been dredged 
in deep water in various parts of the world, minute, branching, flexible tubes, with some- 
what rough exterior owing to partially embedded sand-grains, have not been the least 
frequent. These have hitherto occurred in comparatively small numbers, and though 
they have been supposed t'o belong to the Rhizopoda, their precise nature has been but 
little studied. A number of specimens were' obtained by Dr. Carpenter in 1869, in the 
deepest portion of the North Atlantic explored during the “ Porcupine ” Expedition of 
