118 PHTLLOSrONGIA. 



specimens grow to a height of 280 millim. and a breadth of 320 millim., and 

 are 4-6 millim. thick. 



A more complicated form is that of a pedunculate fan-shaped lamella, 

 which is folded radially ; the folds are irregular and not very deep. These 

 specimens are much smaller, possibly young stages of the foregoing. In others 

 the lamella is curved like a watch-glass, and from its concave side secondary 

 lameUfe or i-idges grow out, which for the most part extend radially. Forms 

 of this kind lead to the more regularly calyciform specimens, which are much 

 more frequent. The usiial form is that of a slender, conical cup, slightly 

 inflated at its lower end. These cups attain a height of 200 millim. and more. 

 Most of the specimens, however, do not exceed 150 millim. in height. The 

 margin of the cup is generally a very regular circle, which lies in a horizontal 

 plane ; its diameter is slightly smaller than the height of the sp®nge. The 

 margin is very thin and sharp. Just below it the wall of the cup does not 

 exceed 2-5 millim. in thickness; further down it becomes stouter, and near 

 the peduncle attains a thickness of 4 millim. Longitudinal ridges, in some 

 specimens, project from the outer surface of the cup. 



However much the shape of the sponge may vary, the surface always pos- 

 sesses the same character. In dry specimens it is cut up by deep furrows 

 into small square fields, and shows in the fresh state and in spirit-specimens 

 irregular groups of very blunt, slightly projecting conuli, divided from each 

 other by concave, perfectly smooth membranes, which correspond to the 

 grooves of dry specimens. The groups of conuli are, on an average, 2 

 millim. broad and 3 millim. long, whilst the depressed membranes between 

 them have a width of 1*5 millim. or less. There is no difference in the 

 structure of the two sides of the lamella or cup-wall in this respect. The 

 oscula are small : on an average, in the living sponge, O-o millim. wide, and 

 always situated in the membranes which cover the grooves : they are confined 

 to one side of the lamella ; in the case of the caliculate forms they are always 

 found on the inner surface. 



The colour of the living sponge is bright red or flesh-colour ; in spirit the 

 colour darkens. Dry specimens are brilliantly white, in consequence of the 

 sand-cortex forming a white skin over the sponge. Dry washed-out skeletons 

 are of a dull light-brown colour. The sponge is soft and flexible in spirit 

 and also when dry ; washed-out specimens can be compressed between the 

 fingers to two thirds. 



From the inhalant pores, which are situated in small groups on the pro- 

 jecting conulous portions of the surface, the water passes into the narrow 

 inhalant canals. The ciliated chambers are spherical, and measure 0-033 millim. 

 in diameter. From each chamber a canal 0-014 millim. wide and 0*01- 

 0-07 millim. long, arises, which opens into one of the wide and irregular 



