1863.] DR. J. S. BOWERBANK ON THE SPONGILLID/E. 457 



translucent, and is supported on a network of spicula ; this network 

 of the dermal surface is thick and abounding with spicula ; but that 

 of the internal skeleton seldom exceeds two or three spicula in sub- 

 stance, and the size of the interstices are usually determined by the 

 length of the spicula, which vary considerably in size. A fully de- 

 veloped one measured, length -^4^ inch, greatest diameter yJ^ir inch. 



In the dried condition the ovaries are nearly hemispherical, but 

 when expanded in water they become globose ; in this state, when 

 viewed with a power of one hundred linear by the aid of a Lieber- 

 kuhn, they are cream-coloured, and present an irregular and deeply 

 pitted surface ; and from these indents or pits the multiradiate- 

 birotulate spicula of the outer surface of the ovary are projected at 

 right angles to the surface, very often for nearly the whole of their 

 length. If the ovaries be acted on by boiling nitric acid so as to 

 render it transparent without entirely disintegrating it, we then see 

 the delicate and beautiful boletiform spicula, the large rotulse of 

 which are placed at the inner surface of the ovarium; while the 

 slender shaft with its small lentiform distal termination is projected, 

 at right angles to the inner surface, through the substance of the wall 

 of the ovary to very nearly its outer surface. This spiculum cer- 

 tainly presents one of the most graceful and elegant forms I have 

 ever seen among sponge-spicula. 



The external surfaces of the rotulse of the birotulate spicula are 

 smooth, very convex, and in many cases almost hemispherical ; so 

 that the points of the curved spines are in the direction of planes 

 parallel to the shaft of the spiculum, and the rotula is cleft almost 

 to the point of union with the shaft. The number of spines vary : 

 in one rotula there were as many as ten ; but the usual number is 

 about five or six. 



The contrast between the two sorts of spicula in the ovary is very 

 great ; one is all lightness and delicacy of structure, the other the 

 type of strength and solidity. The latter, the multiradiate-birotnlate 

 form, is yuVb' ^"^^^ i" length, the diameter of the rotulae ykT)1)' inch, 

 and the diameter of the shaft xsVfl i"ch. The former or boletiform 

 spicula have the following dimensions : — length ^^l-y inch, diameter of 

 large discal end jxhr iiich, and diameter of the middle of the shaft of 

 the spiculum ■joo'oo inch. Lentiform termination -g-^^y^ in diameter. 



Spongilla Brownii, Bowerhank. 



Sponge massive, sessile ; surface spiniferous ; superficial inter- 

 spaces open. Oscula, pores, and dermal membrane obsolete. Ske- 

 leton-spicula fusiformi-acerate, very stout. Ovaries spherical, spi- 

 culous, encased in a globose, irregularly but closely reticulate enve- 

 lope of spicula ; surface of envelope even ; spicula of envelope ace- 

 rate, short, and stout, slightly curved. Ovary-surface tuberculate ; 

 tubercles long and narrow ; spicula of the ovary umbonato-scutulate, 

 minute. 



Colour, dried state, pallid green. 



Hab. River Amazon, on branches of trees pendent in the water 

 (Mr, R. Brown). 



