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THE VOYAGE OF H.M.S. CHALLENGER. 
where sponges are plentiful, their spicules, broken or entire, are often used in place of 
sand, as in fig. 14; and amongst the coral-reefs of the tropics the rough calcareous 
debris is employed in the same way, figs. 15, 16. The minute structure of a test of 
the latter description, constructed of very large grains, chiefly calcareous, is exemplified 
in the sectional drawing, fig. 17. 
It is obvious that an organism so dependent on external conditions must assume a 
great diversity of external characters. Two of the more regular varieties, which in 
addition to their symmetrical contour and neater build, present some peculiarities of 
distribution, have been described separately as Reopliax pilulifera and Reophax 
dentaliniformis respectively. 
A very interesting modification of the type, somewhat allied to these regular forms, 
has been described elsewhere under the name Reophax arctica. 1 The test in this case is 
straight, regularly built and somewhat tapering ; but instead of being cylindrical in section, 
is compressed and bilateral, like Lingulina. It is an exceedingly minute species, and has 
only been found hitherto on the shores of Novaya Zemlya and Franz-Josef Land. 
Reophax scorpiurus is one of the commonest of cosmopolitan species. It is abun- 
dant in the Arctic Ocean to almost the extreme limits of our geographical knowledge, 
and occurs plentifully in all the great ocean-basins, its area of distribution extending at 
least as far south as Heard Island, about lat. 53° S. The bathymetrical range of the 
species is on a corresponding scale. In the tropics it is found at depths commencing 
with 3 or 4 fathoms, and in colder areas on bottoms as shallow as 30 or 40 fathoms; and 
from depths such as these down to 3950 fathoms, it is met with at every stage. 
There can be no doubt that the specimens figured by Terquem from the Oolite of 
Fontoy, Moselle (Nodosaria agglutinans) , and those described by Haeusler from the 
Jurassic formations of Switzerland ( Reophax helvetica) belong to the present species ; it 
is also one of the forms enumerated by Messrs. Crosskey and Robertson in their list of 
Foraminifera from the Post-tertiary beds of Norway. I find no other satisfactory record 
of its occurrence in the fossil state. 
Reophax pilulij era, n. sp. (PL XXX. figs. 18-20). 
Test straight or curved; composed of few (3 to 5) segments. Segments spherical, 
each much larger than its predecessor. Walls composed of coarse sand-grains, but 
compactly built and presenting a nearly smooth exterior. Aperture simple, central, often 
situated in amammillate protuberance. Length, x \,th inch (2*5 mm.). 
This is little more than a local variety of Reophax scorpiurus, characterised by its 
spherical segments and comparatively regular contour. 
1 Denkschr. d. k Akad. Wiss. Wien, 1881, vol. xliii. p. 99, pi. ii. fig. 2, a.b. 
