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THE VOYAGE OF H.M.S. CHALLENGER. 
to xtroth of an inch (0T2 to 0'25 mm.) in breadth, and are manifestly only 
portions of an organism that might be developed almost indefinitely. There can be 
no doubt of their close relationship with Marsipella elongata, which was abundant in 
the same locality. Similar fragments had previously been found during the examination 
of the “ Porcupine ” dredgings, and less characteristic specimens at two or three of the 
Challenger Stations. 
The species has been observed in the following localities Faroe Channel, 530 fathoms 
and 542 fathoms (“Porcupine” and “Knight Errant”); South Atlantic off Buenos 
Ayres, 1900 fathoms; South Pacific off Kandavu, Fiji Islands, 210 fathoms; and off 
Juan Fernandez, 1375 fathoms. 
Rhabdammina, M. Sars. 
Rliabdammina, M. Sars [1868], Carpenter, G. O. Sars, Norman, Brady, Biitschli, Haeusler. 
Rliabdopleura, G. M. Dawson [1870], Norman. 
Test free, tubular; radiate, irregularly branched or rectilinear; with or without 
a central chamber ; the open ends of the tube or its branches forming the apertures ; 
walls firmly cemented, exterior rough. 
The genus Rhabdammina embraces a very natural and well-defined group of 
deep-sea arenaceous Rhizopods, of which the best-known variety possesses a radiate test 
formed of three, four, or five tubes, of about the same diameter, diverging at nearly equal 
angles from a small central chamber. In addition to the typical stellate form, there are 
certain straight varieties, which may be regarded as two-rayed modifications of the type, 
either possessing a central chamber, or in its absence exhibiting a sort of spurious 
segmentation of the tube ; and others with asymmetrically branching tests, which differ 
from the radiate in the ramification taking place from various parts of the surface, 
instead of from a single central point. The test is almost invariably built of coarse 
siliceous sand firmly incorporated, and presents a rough, hard exterior. 
Rhabdammina is essentially a deep-water genus. Setting aside two or three 
exceptional cases in a long list of localities, its bathymetrical range extends from 350 
fathoms to 2400 fathoms. 
Rhabdammina abyssorum, M. Sars (PL XXI. figs. 1-13). 
Rhabdammina abyssorum, M. Sars, 1868, Vidensk.-Selsk. Forhandl., 1868, p. 248. 
„ ,, Carpenter, 1868, Proc. Roy. Soc., vol. xvii. p. 172. 
„ ,, G. O. Sars, 1871, Vidensk.-Selsk. Forhandl., 1871, p. 251. 
Test free, radiate ; consisting typically of a small central chamber, with tubular arms 
of nearly even diameter diverging at equal angles on the same plane, the free open ends 
