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Show 94 DU. J. S. BOWERBANK ON SILICEO-FIBROUS SPONGES. [Jan. 28, the idea that it occurs in but very small quantities in the siliceo-fibrous sponges. In truth, if we compare the abundance of its presence in this species, as well as in D. McAndrewii and other such sponges which have been preserved in their natural condition, we cannot come to any other conclusion than that this vital substance is as abundant in the siliceo-fibrous sponges as it is in the Hali-chondroid species, and even in the true Spongiee. DACTYLOCALYX BOWERBANKII, Johnson. Sponge sinuously aud expansively cup-shaped, sessile. Surface even ; margin flat and angulated. Oscula simple, dispersed, numerous. Pores inconspicuous, dispersed. Expansile dermal system -dermal membrane abundantly spiculous ; connecting spicula furcated patento-ternate, and rarely dichotomo-patento-ternate, large and long; tension-spicula fusiformi-acerate, small and short, few in number; retentive spicula elongo-cylindro-stellate, with very short radii, minute, exceedingly numerous; and elongo-attenuato stellate few in number. Skeleton-areas round or oval, irregular ; fibre cylindrical, smooth, but irregularly nodulous at intervals ; nodules cylindrical, short, terminating hemispherically. Interstitial membrane- interstitial spicula fusiformi-acerate, long, slender, and flexuous, and same form rather short and stout; retentive spicula elongo-cylindro-stellate, and elongo-attenuato-stellate, the same as those of the dermal membrane, few in number. Colour, alive, white (J. Y. Johnson, Esq.), in the dried state light brown. Hab. Deep water off Madeira (/. Y. Johnson, Esq.). Examined in the dried state. The only specimen of this species known was obtained from " deep water off the coast of Madeira," by James Yate Johnson, Esq., and was described and named by him in P. Z. S. 1863, p. 259. The general description he has there given is very correct as far as it goes; but he has not given a definite specific description of its characters. The specimen is now in tbe British Museum. Dr. Gray, in his "Notes ou the Arrangement of Sponges" (P. Z. S. 1867, p. 507), notices the specimen as a synonym of his genus and species MacAndrewia azorica, in the following terms:- " The specimen which Mr. J. Yate Johnson has described under the name of D. Bowerbankii is larger, more orbicular and expanded than I described years before as MacAndrewia azorica ; but I cannot see any other difference." But as the learned author has nowhere, that I can find, given any particulars of the structural peculiarities of the specimen as compared with those of his species MacAndrewia azorica, his hasty assignment of it to that species is in reality devoid of any authority. Half an hour's microscopical investigation of the two specimens which are in his possession would have completely satisfied him that they were very distinct species of animals, as the reader may readily satisfy himself by comparing the figures illustrating the species under consideration in Plate V. figs. 2, 3, 4, & 5, from D. |
