SPONSIIBA, 591 



bodies are constantly present, traversing the main mass of the 

 skeleton; these fibres are, however, niuch less abundant than in 

 the original specimen of Lamarck, and the wall of the sponge is 

 thinner. Abundant. 



-ffd^. Providence and Cerf Islands, Mascarenes, and Amirante 

 group ; beach ,to 24= fms. 



Distribution. " Mediterranean " (Lamarck) ; Zanzibar (Hyatt). 



3. Hippospongia siuuosa. 



Spongia sinuosa, Pallas, Elenoh. Zooph. p. 394 ; Lamarck, Ann. Mus. 



Hist. Nat. XX. p. 371. 

 ? Spongia fenestrata, iLamarck, torn. cit. p. 374. 

 Spongia lapidescens, subspecies mauritiana, ffyatt, Mem. Bost. Soc. 



ii. p. 628. 



Lamarck's and Pallas's S. sinuosa seem, by their descriptions, to 

 be referable to a Hippospongia of which I describe two forms 

 below. S. fenestrata, Lamarck, is probably a more sessile and in- 

 crusting form of the same species. The question of identity is beset 

 with great difficulties, owing to the want of authentic specimens of 

 the diflferent species for reference. A specimen long contained in the 

 National collection, and labelled S. mcBandriformis or mmandrini- 

 formis, differs from the form described below as var. mauritiana 

 mainly in its somewhat more slender fibre (■016-'045 millim. in 

 thickness) ; but its history is unknown. 



With regard to Pallas's description, I would remark (1) that the 

 dry skeleton of our specimens is not tender (" tenera "), but hard 

 and almost incompressible; (2) it attains a vertical thickness of 

 35 millim. ; (3) the cavities meander and anastomose, and are not 

 merely " oblongae vel cotyloidese "; (4) the colour is a fine amber- 

 yellow; (5) in var. mauritiana the fibres are only approximately 

 parallel and perpendicular, except at th^ very surface. 



The term " surface nivellee " used by Lamarck in his description 

 of S. fenestrata well expresses the appearance which the sponge 

 has of having been pared smooth, as in the species H. derasa (see 

 Part I., p. 382, of this Report). 



It is easy to distinguish among the specimens two varieties, of 

 which one apparently corresponds to the more typical form of Hyatt's 

 subspecies, and may therefore stand under that name, viz. 



Hippospongia Biniiosa, var. maoritiaua. 



The general form of the sponge is that of a low, horizontally ex- 

 tended mass, apparently originally attached by one or more small 

 points ; it is about 35 millim. high, and throws out short suboylindri- 

 cal, terminally-rounded lobes 26-35 millim. in diameter. Colour in 

 macerated state bright amber-yellow. Diameter of the meandering 

 canals of the skeleton 2'0 to 5 millim. 



The skeleton consists of a strong horizontal system of long secon- 

 dary fibres lying parallel to the surface,' and of short stout, primary 



