Surface even, uniformly consisting of moderately large triradiates fixed in position by cribriform sarcode.

Vents of the individuals respectively terminal, circular, and each provided with a peristome, leading into a general cloacal cavity, which is narrow and cylindrical at first, but afterwards becomes wider than the wall of this cavity as it spreads itself out into the cloacal dilatations of the rest of the individuals in the mass ; lioles of the cloaca large generally, but still variable in size and distance apart, corresponding with the variable width of the skeletal structure of the surface of the cloaca.

H. patulosculifera, that is, consisting of horizontal intervals defined by the long shafts of sagittal triradiates which, coming from opposite sides of the wall, overlap each other, while the intervals, which are chiefly composed of sarcode, intercommunicate with each other by large holes in addition to the usual pores.

1, respectively, in its thin form confined to the peristome, in its minute one to the surface, where, in combination with the cribriform dermal sarcode, it fixes in the triradiates of this part: and the stouter form chiefly to the region of the mouth, where its much curved and thickened portion, which is outside, is directed towards this aperture, and its attenuated one sunk deeply into the wall of the specimen.

In this species that peculiar form of the sagittal triradiate is well developed wherein the shaft, which is, as usual, straight and cylindrical, is accompanied by a vertically flattened state of the two arms ; so that in situ, that is on the lower and inner part of the peristome, where this form of the triradiate is particularly evident, the shaft is seen to be in a line with the spicules or palisading of the peristome, while the flat arms are spread out sagittally across them — thus acting, like the cross bar of a paling, in keeping flat and in position the lower ends of the palisading.