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Show 276 DR. J. S. BOWERBANK ON [Apr. 6, specimen. The confluent rotulate form of skeleton-structure is not confined to the siliceo-fibrous sponges; it also occurs in the dermis of a rare British sponge, Desmacidon rotalis. In this case it does not occur in the internal skeleton of the sponge, but in the reticulated dermis only. I have figured this beautiful dermal tissue in vol. iii. pl. xc. fig. 9, 'Monograph of the British Spongiadse.' The specimen of Deanea virgultosa figured was presented to me by my late friend Mr. H. Deane, along with those of Farrea gassioti and pocillum; and I presume it is from the same locality as those species. FARREA FISTULATA, Bowerbank. Sponge fistulous, orifices both terminal and lateral, very large, parietes thin. Surfaces, exterior and interior, even, but rough to the touch, each abundantly armed with a single series of harrow-like teeth, based on the angles of the skeleton-tissues, and projected outwardly from their respective surfaces. Oscula and pores unknown. Dermal membrane thin, abundantly spiculous; tension-spicula acerate, variable in size, rather numerous; retentive spicula simple and contort, bihamate, numerous, dispersed. Skeleton-fibre cylindrical, smooth and even; canals large and very distinct; rete symmetrically quadrangular, areas usually square. Internal defensive spicula attenuato-acuate, basally spined, based on the skeleton- fibres, projected at about right angles into the areas of the rete. Sarcode dark amber-colour, thinly coating the skeleton-structures. Colour, dried state, dark amber-brown. Hab..West-Indian seas? Examined in the dried state. This remarkable sponge consists of a single thin stratum of skeleton- tissue in the form of a compound pipe about four lines in diameter. It has all the appearance of being only a portion of a more perfect specimen. It is but an inch in length, but in that short space it has six open terminations of what has apparently been as many ramifications of its fistulous structure; and none of these orifices have a natural or an even margin. The general surface of the specimen is even, and no indications are apparent of either oscula or pores. The dermal membrane is in an excellent state of preservation on the surface of the sponge ; and from its present condition it was evidently in a living state when taken. It is a thin translucent structure, abundantly spiculous. The tension-spicula are slender and acerate, not very numerous ; they are variable in size and irregularly disposed on the surface of the membrane. The bihamate retentive spicula are rather numerously dispersed on the membrane; they are slender and very equable in size. The skeleton is a remarkably beautiful structure. The fibre is perfectly smooth, very equable in its diameter, and it is arranged as nearly as possible in a regular quadrangular network. The central canals are moderately large and very distinct, and are as equable in their diameter and mode of distribution as the rete of the skeleton is. The thin stratum of |