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Show 1873.] DR. J. S. BOWERBANK ON THE SPONGIADcE. 21 From this case, and fiom other similar experiences, it appears that, if we wish to find the living representatives of the beautiful series of the chalk sponges, we must search for them among the multitudinous singular forms of the recent animals that abound in Australian seas, CIOCALYPTA TYLERI. (Plate IV.) Sponge massive, sessile, composed of numerous, closely packed, attenuating, penicillate branches rising perpendicularly from a common base ; branches gradually attenuating, apices rather acutely terminated, entirely closed, deeply furrowed or corrugated. Oscula simple, dispersed over all parts of the sponge. Pores inconspicuous, dispersed. Dermal membrane smooth, abundantly spiculous; spicula acerate, small and slender, dispersed, closely felted together over the whole surface of the membrane, with a few skeleton- or larger spicula intermixed. Skeleton-spicula acerate, rather variable in size. Colour in the dried state cream-white. Hab. Port Elizabeth (Capt. Charles Tyler). Examined in the dried state. I received two specimens of this interesting species from m y friend Capt. Charles Tyler, who obtained them from Port Elizabeth. The one figured is the smallest of the two ; but it is the most characteristic in its growth and general external appearance, which, in both specimens, so closely resemble those of the British species in its early stage of growth, that it would be impossible to separate the two species if it were not for the differences that exist in their organization. The structure of the skeleton of C. Tyleri is in principle exactly that of C. penicillus. There is the same central column in each of the penicillate organs, with numerous short pedicels of closely compacted spicula radiating from it at right angles to the axis, their distal ends diverging at various angles over the inner surface of the dermis ; but their mode of disposition is not nearly so regularly elegant as in the British type species. Although so closely resem bling each other in external form, there is no difficulty in discriminating the two species by their anatomical characters, the forms of their respective skeleton-spicula at once affording an unerring means of separation, those of C. penicillus being fusiformi-acuate, while those of C. Tyleri are acerate. The dermal membrane also of the former species has its spicula fasciculated in the form of a regular and beautiful reticulation, while the spicula in the latter species are irregularly dispersed and closely felted together on the surface of the membrane. The inhalant and exhalant systems are the same in each species. This species is especially interesting, not only from the singularity and beauty of its anatomical structure, but from its exceedingly close resemblance to our British species, although so widely separated from it as regards locality. The British type specimen of the genus, as figured in vol. iii. pl. xiii. fig. 2, 'Monograph of British |