S88 
THE VOYAGE OE H.M.S. CHALLENGER. 
regularly superimposed, and with an aperture consisting of a large number of pores 
scattered over the convex distal end of the test. Gen eric ally it is only distinguished 
from Verneuilina by the porous aperture. There appears to be no record of the occur- 
rence of this species, beyond that supplied in the original notice. 
Chrysalidina dimorpha, H. B. Brady (PI. XLYI. figs. 20, 21). 
Chrysalidina dimorpha, Brady, 1881, Quart. Journ. Micr. Sci., vol. xxi.,'N. S., p. 54. 
Test elongate, triangular, tapering ; the three sides nearly equal, the angles 
subcarinate ; inferior extremity pointed, distal end broad and slightly convex. Segments 
numerous, arranged triserially at the commencement, subsequently in single series. 
Aperture consisting of a number of minute perforations on the distal face of the terminal 
chamber. Texture hyaline. Length, g^-tli inch (0‘5 mm.). 
This species differs from the type ( Chrysalidina gradcita ) in two particulars, — the test 
is triangular instead of nearly round in transverse section, and the arrangement of the 
segments is dimorphous instead of being triserial throughout. The early segments 
however are distinctly Yerneuiline, and the aperture is conspicuously porous. 
Chrysalidina dimorpha is a rare Foraminifer, inhabiting comparatively shallow water 
in the tropics. It has been found on the coral-reefs of Honolulu, 40 fathoms ; in Hong 
Kong harbour, 7 fathoms; in dredged sand from Torres Strait, off" Baine Island, 155 
fathoms ; and in shore-sands from the east coast of Madagascar. A long, somewhat 
attenuated variety occurs in the last-named locality, and also in shallow water on the coast 
of Ceylon. 
Tritaxia, Beuss. 
Uvigerina, pars, d’Orbigny [1840].. 
Textularia, pars, Beuss [1845]. 
Verneuilina, pars, Beuss [1850], Parker and Jones. 
Tritaxia, Beuss [1860], Wright, Marsson, Brady, Terquem. 
Clavulina, pars, Brady [1881].. 
The genus Tritaxia includes those triserial modifications of Textularia which differ 
from Verneuilina in having a central aperture. The aperture generally speaking takes 
the form of a simple rounded perforation. Such varieties betray the same tendency as 
Chrysalidina to produce dimorphous varieties. 
In the living condition Tritaxia is extremely rare, and its distribution limited to a 
few localities. It is best known by the Cretaceous species, described under various 
generic names by d’Orbigny, Beuss, and others. 
