6P0NGIIDA. 415 



primary fibres run vertically to surface, mostly into the surface- 

 points ; these are connected below by long secondary fibres, approxi- 

 mately at right angles to them ; internal skeleton consisting chiefly of 

 long more or less curved spiculo- fibres and membranous expansions, 

 containing non-aggregated spicules, surrounding rounded spaces. 

 Dermal skeleton formed by the projection of the ends of the primary 

 main-skeleton lines ; the spaces between these are occupied by 

 numerous spicules irregularly scattered over the membrane which 

 covers the surface, occasionally aggregated into irregular loose pauci- 

 spicular tracts. Sarcode of interior reddish brown (darkest around 

 the fibres), rather granular, of conuli very dark opaque red-brown 

 Spicules smooth acerate, very slightly curved, tapering to sharp 

 points from about three diameters from ends; size *14 by "0063 

 millim. 



Ilab. Albany Island, Xorthern Australia, 3-4 fms. ; bottom 

 mud. 



A specimen and a fragment, both in spirit, the former 45 millim. 

 (1-i inch) high by 40 millim. across ; a Serpula is imbedded in the 

 lower part, which forms (from anastomosis) almost one continuous 

 mass, and small specimens of Serialaria are growing on it. The 

 tenacity of the internal fibres and membranes shows the presence of 

 a stronger element than ordinary sarcode ; but horny outlines are 

 not to be distinguished on the fibres, although the sarcode is darker 

 here. 



It is nearly allied to Hijmeniacidon bretti and thomasi, Bowerbank 

 (British seas) ; but the spicules of these species are far longer than 

 those here, and the surface-roughness does not extend to the pro- 

 duction of the characteristic hair-like points found here, which 

 resemble those of Eusjwngia. Dr. Gray (P. Z. S. 1867, p. 518) 

 retains these species in Reniera, with most of the acerate-spiculed 

 species of Hymeniacidon described by Bowerbank ; Schmidt (Atl. 

 Geb. p. 76) assigns them to Amorphina. Protoschmidtia fora- 

 minosa, Czerniavsky (Bull. Soc. Mosc. 1879, p. 98), Black Sea, agrees 

 in the proportions and forms of its spicules, in colour, &c, differing 

 mainly in its much less rough surface and distinct vents ; so I place 

 this species in the same genus in preference to Amorphina, which, 

 if Halichondria panicea is to be regarded as typical of its struc- 

 ture, should include forms with a distinctly reticulate dermal 

 skeleton and absence of tough and deeply coloured sarcode from the 

 fibres. 



51. Schmidtia variabilis. (Plate XXXIX. fig. X ; 

 Plate XLI. fig. t.) 



Decumbent ; consisting of elongated horizontal (sometimes ver- 

 tically flattened-out) lobes of very irregular, more or less angular 

 outline, sometimes branching and anastomosing ; the upper margin 

 rises at intervals into low elevations, which consist of thick-walled, 

 wide, rounded tubes, 3 to 7 millim. in diameter at the mouth, 

 within which the true vents unite at about 6 millim. below mouth ; 



