Report on the zoological collections made in the Indo-Pacific Ocean ...

SPONGIIDA. 591bodies are constantly present, travex'sing the main mass of theskeleton ; these fibres are, however, much less abundant than inthe original specimen of Lamarck, and the wall of the sponge isthinner. Abundant.Hah. Providence and Cerf Islands, Mascarenes, and Amirantogroup ; beach to 24 fms.Distribution. " Mediterranean " (^Lamarck) ; Zanzibar (Hi/att).3. Hippospongia sinuosa.Spongia sinuosa, Pallas, Elench. Zooph. p. 394 ;Lamarck, Ann. Mus.Hist. Nat. XX. p. 371.p Spongia feuestrata, Lamarck, torn, cit, p. 374.Spongia lapidescens, subspecies mauritiana, Hyatt, Mem. Bost. Soc.ii. p. 528,Lamarck's and Pallas's S. sinuosa seem, by their descriptions, tobe referable to a Hipposijongia of which I describe two formsbelow. S. fenestrata, Lamarck, is probably a more sessile and incrustingform of the same species. The question of identity is besetwith great difficulties, owing to the want of authentic specimens ofthe different species for reference. A S2)ecimen long contained in theNational collection, and labelled S. ma'andriformis or mceandriniformis,differs from the form described below as var. mauritianamainlj' in its somewhat more slender fibre (•016-'045 millim. inthickness) ; but its history is unknown.AYith regard to Pallas's description, I would remark (1) that thedry skeleton of our specimens is not tender ("tenera"), but hardand almost incompressible ; (2) it attains a vertical thickness of35 millim. ; (3) the cavities meander and anastomose, and are notmerely " oblongte vel cotyloidese "; (4) the colour is a fine amberyellow; (5) in var. mauritiana the fibres are only approximatelyparallel and perpendicular, except at the very surface.The term " surface nivellee " used by Lamarck in his descriptionof IS. fenestrata well expresses the appearance which the spongehas of having been 'pared smooth, as in the sj)ccies i/. dcrasa. (seePart I., p. 382, of this Keport).It is easy to distinguish among the specimens two varieties, ofwhich one apparently corresponds to the more typical form of Hyatt'ssubspecies, and may therefore stand under that name, viz.Hippospongia sinuosa, var. mauritiana.The general form of the sponge is that of a low, horizontally extendedmass, apparently originally attached by one or more smallpoints ; it is about 35 millim. high, and throws out short subcylindrical,terminally-rounded lobes 25-35 millim. in diameter. Colour inmacerated state bright amber-yellow. Diameter of the meanderingcanals of the skeleton 2-5 to 5 millim.The skeleton consists of a strong horizontal system of long secondaryfibres lying parallel to the surface, and of sliort stout, primary