182 Mr. W. S. Kent on a new Vitreous Sponge.Fig. 10. The same, two of the sigmoid spicules, greatly magnified, as seen with a quarter-of-an-inch compound power, showing the spines on their shafts and extremities respectively: a, sigmoid form; b, circular form. Size about 1-400th of an inch long, and about 1-12000th of an inch thick. N.B. These spicules have a double sigmoid or spiral curve, consisting of about two turns of the spire altogether, but so different individually that it is only here and there that a true sigmoid forin is seen, the rest presenting a curvilinear one like a fragment of a circle (b); yet they are ail contort, and could not be made to lieflat on a plane surface.Fq. 11. Trachya pernucleata, n. gen. et sp., dried state, half the specimen, natural size, upper surface: a, oscule.Fig. 12. The saine, portion of upper surface, greatly magnified, to show:-a, the depressions in which the pores are situated; b, the ridges between them formed by the projecting points of the large and small spicules, which have been broken off, as indicated by the black circular dots.Fig. 13. The same, diagram to show the relation of the large to the small spicules, and their vertical arrangement so as to form a hard crust on the upper surface: a a, large spicules; b b, small spi-cules.Fig. 14. The same, horizontal view of vertical section of corresponding half of fig. 11, natural size, showing internal structure composed of :-a a, nuclear or radiating groups of spicules; b, cavities of canal-system; c, group of oscules in a depression in the lower surface. This section also shows the dark-grey colour of the upper portion passing into the lighter one of the under surface.Fig. 15. The sanie, whorl or radiating group of large spicules, much mag-nified, to show their superficial arrangement on the under sur-face of this sponge, and the comparative absence of the small spicule.Fig. 16. The same, the large and small spicules, relatively magnified: a, large spicule, stout, straight, smooth, fusiform, acerate; b, real length, about 1-18th of an inch, greatest thickness about 3-1800ths of an inch; c, largest size of small spicule, straight, smooth, fusiform, acuate (tlat is, needle-shaped or pointed at one end and obtuse at the other). Size about 1-60th of an inch long by about 1-1800th of an inch in its greatest transverse diameter. XVI.-Notice of a new Vitreous Sponge, Pheronema (Hol-tenia) Grayi. By W. SAVILLE KENT, F.Z.S., F.R.M.S., of the Geological Department, British Museum. THE recent dredging-expedition of the yacht 'Norna,' owner and commander Mr. Marshall Hall, F.G.S., in which I had the pleasure of being associated with Mr. Edw. Field-ing, resulted in our obtaining, off Setubal, in addition to many other most interesting organisms, a vitreous sporige closely allied to IIoltenia Carpenter, Wyv. Thomson. At the time of taking it I strongly suspected it to be identical with
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