119. _The Lattice-Spheres of the Phæodaria._--The lattice-spheres or Sphæroid skeletons of the PHÆODARIA, which are generally developed quite regularly, though occasionally in a modified form, fall in the order #Phæosphæria# into two groups of very different structure, each of which includes two families. The first group (_Phæosphæria inarticulata_) contains the families Orosphærida (Pls. 106, 107) and Sagosphærida (Pl. 108); the lattice-work of the former consists of irregular polygonal meshes and very coarse, partially hollow trabeculæ; in the latter, on the other hand, it consists of triangular meshes and very slender filiform trabeculæ; in both families the whole sphæroid skeleton forms a single unsegmented piece as in most #Sphæroidea#. In the second group of {lxxx}#Phæosphæria# (_Phæosphæria articulata_), on the other hand, the lattice-sphere is segmented in quite a peculiar manner, and composed of hollow cylindrical tangential tubes, which are separated by astral septa at the nodal points of the network; this remarkable structure characterises the two families, Aulosphærida (Pls. 109-111) and Cannosphærida (Pl. 112); the segmented lattice-sphere of the former is simple and hollow; while that of the latter is connected by centripetal radial tubes with a simple concentric inner shell, which is sometimes solid, sometimes latticed, and provided with a main-opening corresponding to the astropyle of the enclosed central capsule. Since in the Aulosphærida also, hollow centripetal radial tubes project from the segmented lattice-sphere, it is possible that they have been derived from the Cannosphærida by the loss of the primitive internal shell. A special peculiarity of many #Phæosphæria# (_Oroscena_, _Sagoscena_, _Auloscena_, &c.) consists in the fact that the whole surface of the lattice-sphere is regularly covered with pyramidal or tent-shaped prominences (Pl. 106, fig. 4; Pl. 108, fig. 1; Pl. 110, fig. 1). A simple lattice-sphere quite similar to that of most Monosphærida also constitutes the skeleton of the Castanellida (Pl. 113), but since it possesses a special main-opening, it must be referred promorphologically to the Cyrtoid shells of the #Phæogromia#.