1872.] DR. J. S. BOWERBANK ON BPONGIAD^E. 19/ 



the natural base was as extended as the present mutilated one, as 

 the basal fasciculi of the skeleton run uninterruptedly from the centre 

 to the circumference of the present base. Unfortunately the whole 

 of the long surface-spicula were rubbed off during its carriage from 

 Liverpool ; but as I carefully preserved all the spicula that I found 

 in the paper in which it was packed, I fully satisfied myself of their 

 structure, and that they were truly from the sponge in question. 

 Beside the large fusiformi-spiculated porrecto-ternate spicula, there 

 are numerous small fusiformi-acerate ones, which connect; the dermal 

 membrane with the stratum of ovaries beneath it ; but they appear, 

 even in the dried specimen, scarcely to project their apices through 

 the membrane, excepting in the neighbourhood of the pores, around 

 which they project in small radiating fasciculi for a fourth or a third 

 of their length, apparently as organs of defence to those orifices, 

 which are congregated in little pits or depressions, and which give a 

 striking character to the surface of the dried specimen. 



The pores vary in form from round to oval, and in diameter from 

 j^j inch to Yax inch ; and beneath each group of pores there was an 

 iutermarginal cavity, the diameter of the diaphragm at the base of 

 which varied from yJpj-inch to y 1 ^ inch. 



The structure of the large fusiform-spiculated porrecto-ternate 

 spicula is new and interesting ; the shaft of the spiculum is conti- 

 nued in a straight line, and terminates acutely and at about the length 

 of one of the radii ; beneath its apex three radii are given off at 

 equal distances from each other, slightly curving towards the distal 

 points in the direction of about an angle of 45 degrees. The fur- 

 cated porrecto-ternate spicula are larger and stronger than the por- 

 recto-ternate ones ; and the angle at which they curve upwards from 

 the shaft is from about 50 to 60 degrees. The oscula are extremely 

 numerous ; although they occupy an area of about 5 inches in dia- 

 meter they are rarely as much as the eighth of an inch apart : the 

 orifice is level with the surface-plane, and is surrounded by a thin 

 marginal membrane ; and the entrance for about the length of its 

 own diameter is cylindrical and perfectly open, but at that point 

 there is situated a stout veil or diaphragm. In some cases this was 

 more or less open ; but in the greater number it was firmly and com- 

 pletely closed, the membrane exhibiting numerous concentric rugae, 

 at the middle of which there was a strong pursing of the tissue. 

 This opaque spot was not always in the centre of the membrane ; 

 but it always formed the centre of the concentric lines of rugse. 

 The lining membrane of the entrance to the osculum was smooth 

 and tense, and exhibited a series of lines at right angles to the long 

 axis of the osculum, indicating the presence of fibrous tissue. On 

 examining the veils or diaphragms at the inner surface they appeared 

 at least twice the diameter of the inner orifice of the osculum, which 

 bevelled slightly inward, like a very shallow funnel, to the outer 

 margin of which the extreme edge of the diaphragm was firmly 

 attached, thus readily allowing of an opening of the membrane tc 

 the full extent at least of the diameter of the cylindrical outer tube 

 of the osculum. The interstitial membranes were singularly crowded 



