_Spongilla glomerata_, Noll, Zool. Anz., Jahr. ix, p. 682 (1886).
_Spongilla fragilis_, Vejdovsky, P. Ac. Philad. 1887, p. 176.
_Spongilla fragilis_, Potts, _ibid._ p. 197, pl. v, fig. 2; pl. viii, figs. 1-4.
_Spongilla fragilis_, Weltner, Arch. Naturg. lix (1), p. 266, pl. ix, figs. 18-20 (1893).
_Spongilla fragilis_, _id._, Arch. Naturg. lxi (i), p. 117 (1895).
_Spongilla fragilis_, _id._, in Semon's Zool. Forsch. in Austral. u. d. Malay. Arch. v, part v, p. 523.
_Spongilla fragilis_, Annandale, P. U.S. Mus. xxxvii, p. 402 (1909).
_Spongilla fragilis_, _id._, Annot. Zool. Japon. vii, part ii, p. 106, pl. ii, fig. 1 (1909).
_Sponge_ flat, lichenoid, never of great thickness, devoid of branches, dense in texture but very friable; colour brown, green, or whitish; oscula numerous, small, flat, distinctly star-shaped.
_Skeleton_ with well defined radiating and transverse fibres, which are never strong but form a fairly dense network with a small amount of spongin.
_Spicules._ Skeleton-spicules smooth, sharply pointed, moderately stout, as a rule nearly straight. No flesh-spicules. Gemmule-spicules cylindrical, blunt or abruptly pointed, nearly straight, covered with relatively stout, straight, irregular spines, which are equally distributed all over the spicule.
_Gemmules_ bound together in free groups of varying numbers and forming a flat layer at the base of the sponge; each gemmule small in size, surrounded by a thick cellular coat of several layers; with a relatively long and stout foraminal tubule, which projects outwards through the cellular coat at the sides of the group or at the top of the basal layer of gemmules, is usually curved, and is not thickened at the tip; more than one foraminal tubule sometimes present on a single gemmule; gemmule-spicules arranged horizontally or at the base of the cellular coat.
The species as a species is easily distinguished from all others, its nearest ally being the N. American _S. ingloriformis_ with sparsely spined skeleton-spicules which are very few in number, and gemmule groups in which the foraminal tubules all open downwards.
Several varieties of _S. fragilis_ have been described in Europe and America.
TYPE.--Potts refers to the type as being in the Academy of Natural Sciences at Philadelphia.