OCR Text |
Show 1877.] FIVE N E W SPECIES OF SPONGES. 459 packed specimens, very uniform in their colour and degree of semi-transparency. These organs varied in diameter from j ^ to y-gVu inch. Some of these groups of gemmules consisted almost entirely of the larger forms, while in others they were nearly all of the smaller description. They require a linear power of about 300 to render them distinctly to the eye. I have never before seen a similar congregating of the gemmules in any sponge that I have examined. The general structure of the skeleton is very irregular, the rete in some parts being composed of many more spicula than in others. The spicula of which it is constructed are of the same form and size as those of the dermis. The gemmules were also dispersed singly around the rete to which they were attached ; and in size and general character they were in perfect accordance with those grouped on the inner surface of the dermal membrane. This sponge is the only specimen I have seen of the species ; and although its structural characters are exceedingly simple, its external ones are so remarkable, that it cannot well be confounded with any other known species of Isodictya. POLYFIBROSPONGIA, genus novum. Skeleton kerato-fibrous. Fibres solid, cylindrical, aspiculous. Rete symmetrical. Skeleton-lines polyfibrous ; primary lines of the skeleton radiating from the base of the sponge to the distal margin; secondary lines disposed at nearly right angles to the primary ones. Although nearly allied in many respects to the genus Spongio-nella, there is an important difference in the structural arrangement of the skeleton-fibres of this sponge as compared with those of the type forms of Spongionella pulchella, which distinctly separates them. In the latter genus the skeleton-structures, both primary and secondary, are composed of single fibres; the primary ones radiating from the base of the sponge, and the secondary fibres being disposed at right angles to the primary ones. This mode of skeleton-structure prevails also in the sponge from the Philippine Islands ; but instead of single fibres thus disposed, we find continuous fasciculi, each composed of numerous slender fibres in both the primary and secondary portions of the skeleton-structures. Thus, although the individual fibres of the sponge are very nearly the same as in Spongionella, the congregation of the fibres in large diffuse fasciculi constitute an important generic difference; and I therefore propose to make this peculiar mode of skeleton-structure the type of a distinct genus, to be designated as above. 3. POLYFIBROSPONGIA FLABELLIFERA, sp, nov. Sponge fan-shaped, pedicel very short, parietes very thin, surface smooth and even. Oscula and pores inconspicuous. Dermal membrane aspiculous, but abundantly supplied with adherent extraneous matters. Skeleton : Primary lines composed of a loosely constructed polyfibrous cord of slender anastomosing keratose fibres; secondary lines constructed the same as those of the primary series |