SPONGES. 193 



commonly about 0'4G millim. by 0'0285 millim., but very variable in diameter; ofteu 

 much more slender than the measurement given, and occasionally a good deal stouter ; 

 sometimes rather longer. 

 RN. 256 (Ceylon seas). 



Acanthella, SCHMIDT. 



Axinellidce of usually flabellate form and more or less cartilaginous consistence. With 

 more or less strongly aculeate or conulose surface. With no microscleres. 



Acanthella carteri, DENDY. Plate VIII. , fig. 6. 



There are several specimens of this sponge in the collection, and as the external 

 form has not yet been figured, Professor HEUDMAN has kindly had one of them 

 photographed for this report (Plate VIII. , fig. 6). There is a strong development of 

 very pale-coloured spongin fibre associated with the spicules, which I omitted to 

 mention in my original description, DENDY, 3 (1889). 



KELLER'S Acanthella aurantiaca (61), from the Red Sea, comes very near to this 

 species, if it be not identical with it. 



RN. 11,36, 49 (all from Gulf of Manaar, Stats. II., IV., V.) ; ? 301 (perhaps young) ; 

 ? 336 (perhaps young). 



Acanthella flabelliformis, KELLER. 



The single specimen is thinly flabellate ; ? stipitate (the stalk may have been broken 

 off, the specimen being somewhat damaged and worn) ; both surfaces beset with 

 rather sharp longitudinal ridges, showing a tendency to break up into conuli ; with 

 deep, semi-cylindrical, longitudinal grooves between the ridges. The floor of the 

 grooves is formed by a rather thick, translucent dermal membrane, containing no 

 spicules and easily stripping off; in this membrane are scattered numerous small 

 vents. Colour (in spirit) dark greyish-brown. Texture tough, compressible, resilient. 

 Height of the single lamella of which the specimen consists 37 millims. ; breadth 

 51 millims. ; thickness (including ridges) about 5 millims. 



The skeleton is a reticulation of stout spicular fibre, containing much spongin and 

 comparatively few, though still very numerous, spicules. The main fibres curve 

 upwards and outwards to the surface, and are united by irregular cross-fibres. The 

 arrangement of the spicules, both in the fibres arid between them, is very irregular 

 and confused. The main fibres are often somewhat plumose. 



Spicules. Oxea ; straight or curved, slender, gradually and sharply pointed at 

 each end ; size fairly uniform, up to about 0'3 millim. by 0'0065 millim. ; occasionally 

 stylote. 



The soft tissues are densely charged with small, round, granular brown cells, 

 probably pigment cells. 



This species is chiefly characterised by its oxeote spicules and by the distinctly reticu- 



2 C 



