19. Trochospongilla phillottiana*, _Annandale_.
_Trochospongilla phillottiana_, Annandale, J. Asiat. Soc. Bengal, 1907, p. 22, fig. 6.
_Trochospongilla phillottiana_, _id._, Rec. Ind. Mus. i, p. 269 (1907).
_Trochospongilla phillottiana_, _id._, _ibid._ ii, p. 157 (1908).
_Sponge_ hard but friable, forming sheets or patches often of great extent but never more than about 5 mm. thick; the surface minutely hispid, flat; colour pale yellow, the golden-yellow gemmules shining through the sponge in a very conspicuous manner; oscula inconspicuous; external membrane adherent; no basal chitinous membrane.
_Skeleton_ dense but by no means strong; the reticulation close but produced mainly by single spicules, which form triangular meshes; radiating fibres never very distinct, only persisting for a short distance in a vertical direction; each gemmule enclosed in an open, irregular cage of skeleton-spicules.
_Spicules._ Skeleton-spicules short, slender, blunt, more or less regularly and strongly spiny, straight or feebly curved. No flesh-spicules. Gemmule-spicules with the rotulæ circular, very wide as compared with the shaft, concave on the surface, with the shaft projecting as an umbo on the surface; the lower rotula often a little larger than the upper.
_Gemmules_ numerous, situated at the base of the sponge in irregular, one-layered patches, small (0.32 × 0.264 mm.), of a brilliant golden colour, distinctly wider than high, with a single aperture situated on an eminence on the apex, each clothed (when mature) with a pneumatic coat that contains relatively large but irregular air-spaces among which the spicules stand with the rotulæ overlapping alternately, a funnel-shaped pit in the coat descending from the surface to the upper rotula of each of them; the surface of the gemmule covered with irregular projections.
Diameter of gemmule 0.32 × 0.264 mm. Length of skeleton-spicule 0.177 " Length of gemmule-spicule 0.015 " Diameter of rotule 0.022 "
This species appears to be related to _T. pennsylvanica_, from which it differs mainly in the form of its gemmule-spicules and the structure of its gemmule. My original description was based on specimens in which the gemmule-spicules were not quite mature.