REPORT OK THE EORAMINIFERA. 
269 
"Walls comparatively thin, composed of angular sand-grains, fir m ly cemented ; interior 
smooth. Length sometimes 1 inch (25 mm.) or more. 
The long arenaceous tubes of Rhabdammina discreta closely resemble the arms of the 
typical Rhabdammina abyssorum; they are of about the same diameter, and the minute 
structure of the test in the two species is indistinguishable. But, whilst the individual 
rays of the latter species are of nearly even diameter throughout, the tube of 
Rhabdammina discreta, in addition to its indefinite length, is marked by external 
constrictions, which give to it a more or less nodose character. Sometimes an example 
is met with like that represented in fig. 8, in which one joint is swollen till it resembles 
the central chamber of Rhabdammina linearis, suggesting the idea that the imperfect 
segmentation of the tube in some way takes the place of the radiate division of the test 
in the typical form. Specimens with this peculiarity are readily distinguished from 
Rhabdammina linearis, in which it is a constant feature, by their comparatively large size, 
darker colour, and firmer texture, as well as by the transverse constrictions already described. 
Rhabdammina discreta occurs in company with Rhabdammina abyssorum, though not 
invariably present even where the latter species is plentiful. Its occurrence has been 
recorded at seven Stations in the North Atlantic, varying in depth from 410 fathoms to 
1750 fathoms; at two in the South Atlantic, 350 fathoms and 1900 fathoms respec- 
tively ; at one in the western area of the North Pacific, 2475 fathoms ; and at four in the 
South Pacific, 1075 fathoms to 2160 fathoms. The bathymetric range of these fourteen 
localities lies between 350 and 2475 fathoms, indicating clearly that the home of the 
species is in deep water. Nevertheless in the far north, off the coast of Greenland, it 
occurs at a depth not greater than 20 fathoms, and in the far south, off Kerguelen 
Island, at 120 fathoms, so that probably the distribution is more or less affected by the 
temperature of the sea-bottom. 
Rhabdammina linearis, H. B. Brady (PI. XXII. figs. 1-6). 
Rhabdammina linearis, Brady, 1879, Quart. Journ. Micr. Sci., vol. xix. K. S., p. 37 pi. iii. figs. 
10 , 11 . 
Test free, linear, straight or bent ; consisting of an oval central chamber, with two 
long tubular arms, one at each end, projected in the same line ; tubular portion often 
irregular in width ; wall of the central chamber thinner than that of the arms ; aperture 
formed by the free ends of the tubes. Length, ^th inch (6 or 7 mm.). 
Since the provisional description of this species was written ( loc . cit.), a number of 
additional specimens have been found, and some amendments have become needful in the 
characters accorded to it. 
The test is altogether of smaller dimensions than those of average examples of the 
(ZOOL. CHALL. EXP. PART XXII. — 1883.) Y 35 
