The genus Aulonia is the simplest form of the subfamily Aulonida, or of those Aulosphærida in which the lattice-work of the shell is composed not of triangular but of polygonal meshes; all these Aulonida are much rarer and much less differentiated than the Aularida or the common Aulosphærida with triangular meshes. Aulonia has the same simple, smooth, spherical lattice-shell as Aularia, and differs from it only in the polygonal form of the meshes, which, however, is very constant.
1. Aulonia tetragonia, n. sp.
Meshes regular or subregular, square, sometimes intermingled with a variable number of irregular, triangular, and pentagonal meshes. Bars cylindrical, of equal breadth.
Dimensions.—Diameter of the spherical shell 2.0 to 3.2, of the meshes 0.12 to 0.18; breadth of the bars 0.008.
Habitat.—Antarctic Ocean, Station 154, depth 1800 fathoms.
2. Aulonia pentagonia, n. sp.
Meshes subregular, pentagonal, intermingled with a smaller number of quadrangular and triangular irregular meshes. Bars cylindrical, of equal breadth.
Dimensions.—Diameter of the spherical shell 2.8 to 3.2, of the meshes 0.15 to 0.2; breadth of the bars 0.01.
Habitat.—South Pacific, Stations 293 to 302, depth 1375 to 2270 fathoms.
3. Aulonia hexagonia, n. sp. (Pl. [111], fig. 1).