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Show 1869.] DR. J. S. BOWERBANK ON SILICEO-FIBROUS SPONGES. 323 6. A Monograph of the Siliceo-fibrous Sponges. B y J. S. B O W E R B A N K , LL.D., F.R.S., F.Z.S., & c - P a r t II * (Plates XXI.-XXV.) IPHITEON, Valenciennes. Iphiteon panicea, of the Museum, Jardin des Plantes, is distinctly a symmetrical structure. The skeleton is reticulated in a very remarkable manner. The whole consists of a series of regular areas, with pentagonal or hexagonal margins, from each angle of which a fibre passes in a direct line to the centre of the area, where they unite, forming a central, slightly protuberant mass. From each of these centres one or two fibres are given off at about right angles to the plane of the area, in opposite directions to each other, by which the adjoining areas above and below are connected. These connecting fibres always terminate at junctional angles of the nearest adjoining area, and the fibres thus projected never seem to unite with any other portions of the reticulating skeleton. The appearance resulting from this mode of structure is very remarkable when we view a microscopical plane of this beautiful tissue. The effect is that all the areas present a singularly confluent appearance, each perfect in itself, and each forming, as it were, a part of a neighbouring area. Occasionally square spaces may be found ; but these are only intervals of the reticulations. In treating of the gemmules in m y paper " O n the Anatomy and Physiology of the Spongiadee," I have figured a small portion of the skeleton of the specimen in the French Museum, said to be from Porto Rico (plate 34. fig. 17, Phil. Trans, for 1862), and I have there designated it as identical with Stutchbury's genus Dactylocalyx ; but a more critical examination, with a view to the determination of its specific characters, has convinced m e that I was in error in doing so. Neither Dactylocalyx nor Iphiteon appear in Lamarck's ' Animaux sans Vertebres,' second edition, published in 1836, nor in Agassiz's ' Nomenclator Zoologicus,' published in 1848. Nor is there any notice of the subject in the list of the works of Prof. Valenciennes published in the ' Bibliographia Zoologiae et Geologiae,' by the Ray Society, 1854; we may therefore reasonably conclude that although named by Prof. Valenciennes in the Museum of the Jardin des Plantes, he never published any descriptive characters of the genus. The symmetrical arrangement of the skeleton-structures distinctly separates Iphiteon from Dactylocalyx, with which it has hitherto been confounded by other English naturalists as well as by me. I therefore propose the following characters for the genus IPHITEON, Valenciennes. Skeleton siliceo-fibrous. Fibre solid, cylindrical. Reticulations symmetrical. Areas rotulate, confluent. Type Iphiteon panicea from Porto Rico, Museum of the Jardin des Plantes, Paris. * For Part I. see antea, pp. 00-100. |