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THE VOYAGE OF H.M.S. CHALLENGER. 
angular and sharp ; oral end rounded or obtuse, opposite extremity more or less pointed. 
Segments comparatively few, septation very obscure externally. Texture subarenaceous, 
compact ; surface smooth ; colour dirty- white. Aperture a neat, round, terminal orifice. 
Length, about ^th inch (1‘6 mm.). 
In the provisional description of this species ( loc . cit.), it was erroneously referred to 
the genus Clavulina. It is a near ally of Tritaxia tricarinata, from which it differs 
somewhat in size, contour, and other minor particulars, but chiefly in the substance and 
texture of the test. The walls are thick and calcareous, and though not quite homo- 
geneous, are nearly smooth externally, and have but little appearance of arenaceous 
structure. 
The specimens were dredged at Station 174, off Kandavu, Fiji Islands, 210 
fathoms. 
Tritaxia caperata, EL B. Brady (PI. XLIX. figs. 1-7). 
Clavulina caperata , Brady, 1881, Quart. Journ. Micr. Sci., vol. xxi., N. S., p. 54. 
Test dimorphous, the earlier or broader portion triserial (Yerneuiline), the later 
segments of adult specimens more or less uniserial : subcylindrical or elongate-ovate in 
contour ; oral end narrow, either rounded or truncate ; aboral end tapering to a point, 
or slightly rounded. Segments very numerous, short, irregular in form, cavities sub- 
divided by secondary septa ; sutures marked by limbate lines, which give the exterior 
of the test a transversely wrinkled appearance. Aperture simple ; in adult specimens 
central and terminal, often partially closed by an irregular projecting border. Length, 
j^th inch (2 '5 mm.). 
This species was originally assigned to the genus Clavulina, under the impression that 
the contracted apertural border, noticed in adult specimens, was some modification of the 
“ valvular tongue,” which is a distinctive feature of that type. But in the earlier or 
triserial stage of growth (fig. 3, a.b.), the orifice is distinctly Textularian, not Yalvuline ; 
and this fact, together with the subdivided chambers, leaves little doubt that the species 
is in reality a modification of Verneuilina, and may therefore, from its central aperture, be 
treated as a dimorphous form of Tritaxia. 
The walls of the test are thick and finely arenaceous, and in some places are traversed 
by long pore-canals, as shown in fig. 7. The labyrinthic condition of the interior is 
illustrated by the sectional figures, 4, 5, 6. 
The best examples of Tritaxia caperata have been procured from sands dredged off 
Kandavu, Fiji Islands, 250 fathoms ; but the species also occurs off the Philippine Islands, 
95 fathoms, and sparingly off Sombrero Island, West Indies, 450 fathoms. 
