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Show 224 MR. R. KIRKrATRICK ON THE POR1FERA [Mar. 6, " the specimen covered the submerged surface of a large stone to the extent of over a square foot in area ; the crust was closely adherent and very thin." The thickness of the crust is 2 m m . There are no oscules on the fragments of the specimen. The surface is level and provided with tufts of spicules '16 m m . in height, formed by the ends of the main fibres. The skeleton is formed of main longitudinal fibres about 6 spicules thick; at varying levels these fibres give off transverse secondary fibres 2-3 spicules thick, which meet the extremities of those from other main fibres ; in parts where the main fibres are closer together the secondary bundles reach across from one main fibre to another, and the secondary bundles are thicker. There are traces of a basal spongin-lamella in the form of broken scale like fragments; but the spongin-fibres are reduced to mere cushions, into which the ends of the basal oxeas are immersed. Spicules.-The megascleres are smooth curved oxeas 214 x 18*5^, with subtornote ends; frequently with a central knob. Micro-strongyles, scattered about in the tissues, are identical with those of the gemmules, and in all probability have belonged to those bodies. The gemmules are spherical, 380-425 JJ in diameter, with one, two, or three pore-tubes, each rising about 18 p beyond the surface. The position of the pore-tubes varies, and when there are several they may be scattered over the circumference or close together. In one instance a pore-tube is thick-walled, closed at the end, and bent over. The gemmule-spicules are micro-strongyles, arranged tangentially in one or two layers on the chitinous capsule. When there is only one layer, a tessellated or parquet-like pattern is discernible, each tessella being made up of a parallel row of 4-6 micro-strongyles, and fitting in with neighbouring tessella^ at varying angles. W h e n the layer is double it is difficult to make out any pattern; here and there the spined ends of the spicules project above the general level. The strongyles are of two kinds: in one, 70 x 12 u, the spicule is slightly curved, of nearly uniform diameter, spined all over with short blunt vertical spines, but less so in the centre; in the other, which is 65 x 16 p, the centre is nearly smooth, swollen, and barrel-shaped, and tapering to the spined ends. Affinities.-The gemmule-spicules somewhat resemble those of Spongilla sumatrana Weber, of which species Weltner describes two African varieties; in all these there are short spined micro-strongyles, but there are no flesh-spicules in the new species, and the megascleres are smooth, whereas in S. sumatrana and its varieties there are flesh-spicules and the megascleres are spined. Spongilla permixta Weltner from German East Africa, of which species only the gemmules are known, has spined microstrongyles for its gemmule-spicules, but these are much more slender, being only 3 p in diameter, and with recurved spines. In S. biseriata Weltner the oxeas of the skeletal framework are |