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THE VOYAGE OF H.M.S. CHALLENGER. 
This species, which was briefly described in the Report on the Foraminifera of the 
“ Knight Errant ” Expedition, is very variable in external appearance. The test is always 
arenaceous and often loosely built ; it is oblong and rounded inform, and consists of only 
a small number of segments. In the North Atlantic it is found in company with other 
arenaceous Foraminifera at moderate depths, and is often parasitic upon the tests of larger 
forms such as Rhabdammina (fig. 9). In deep water it exhibits a tendency to become 
triserial. The North Atlantic specimens are generally of rich brown colour, whilst those 
from elsewhere, especially such as have their home amongst coral-sand, are more frequently 
of white or light-grey hue ; sometimes both brown and white specimens occur in the same 
dredging. 
Textularia aspera has been obtained at five Stations in the North Atlantic, ranging 
in depth from 390 to 530 fathoms ; at three in the South Atlantic, 350 to 1435 fathoms ; 
and at two in the South Pacific, 175 and 210 fathoms respectively. 
Bigenerina, d’Orbigny.. 
Nautilus, pars, Batsch [1791]. 
Orthoceratia, pars, Soldani [1791]. 
Bigenerina, d’Orbigny [1826], Romer, Reuss, Costa, Parker and Jones, Karrer, Brady, Schwager, 
M. Sars, Vanden Broeck, Winther, Terrigi, &c.. 
Gemmulina, d’Orbigny [1826]. 
Vulvulina, pars, d’Orbigny [1826], Reuss. 
Clavulina, pars, d’Orbigny [1839], Karrer. 
Grammostomum, Reuss [1845], Parker and Jones, Brady. 
Polymorphina, pars, Ehrenberg [1854], 
Schizophora, Reuss [1861], Hantken, Karrer, Seguenza, Scblumbergcr. 
Venilina, Gtimbel [1868]. 
Climacammina, Brady [1876], Schwager. 
1 Stylolina, Karrer [1877], 
Cribrostomum, pars, Moller [1879]. 
The genus Bigenerina is represented morphologically by a Textularian shell with the 
addition of one or several uniserial segments, and d’Orbigny ’s original description 
of the type is based simply on the dimorphous condition of /the test. The relative 
development of the biserial and uniserial portions varies a good deal ; in some cases the 
Textularian segments are comparatively inconspicuous, and do not occupy collectively 
more than one-fourth of the entire length, whilst in others they form the principal part 
of the test. The Nodosarian segments vary in number from one to eight or nine. 
Of all the Textularian genera, Bigenerina has the nearest affinity to Textularia 
proper ; its range of variation in minor characters is in many respects similar to that of 
the typical group and almost equally extensive. Thus, amongst the Textularice there are 
conical, subcylindrical, compressed, and carinate forms ; so in Bigenerina may be found 
cylindrical, compressed, carinate, and other isomorphous varieties : in Textularia the aper- 
