PLATE LXXII. 193 



bi- or tri-spinulate. Skeleton of basal mass. Fasci- 

 culi polyspiculous, irregularly disposed ; spicula same 

 as those of the cloacal fistula?. Primary external de- 

 fensive system. Spicula as large and as long, and of 

 the same form as those of the skeleton ; projected 

 beyond the dermal surface for the greater portion of 

 their length ; very numerous ; secondary defensive 

 system the same as that of the surface of the cloaca?. 

 Interstitial membranes. Tension spicula, minute fusi- 

 formi-spinulate. 



Colour. In spirit, light fawn-yellow. 



Habitat. Shetland ; forty to fifty fathoms ; Rev. 

 A. M. Norman. 



Examined. In the wet state from spirit. 



The specimen under consideration is fifteen lines in 

 length, five lines in breadth, and rather exceeding two 

 lines in thickness, but I do not believe this to be its 

 natural dimensions but rather that it is a portion of a 

 larger specimen, as what there remains of it has all the 

 characters of a fully-developed sponge, and there are 

 no indications of basal membrane to lead us to a cor- 

 rect knowledge of its thickness. It is furnished with 

 two, large, well-developed, cloacal fistula?, of nearly 

 equal size ; the largest of them is five lines in height 

 and four lines in breadth at the junction with the 

 basal mass ; each of them is compressed so that their 

 thickness from back to front at the base does not 

 exceed two lines. 



The strikingly hirsute character of the basal mass 

 contrasted with the smooth and even surfaces of the 

 cloacal fistula? readily leads to the discrimination of 

 this sponge ; the spicula are very numerous, and many 

 of them exceed the sixteenth of an inch in length, so 

 that the strikingly smooth mammiform fistula? even to 

 the unassisted eye appear to spring as it were out of a 

 basal bed of large long spines. When a section of the 

 sponge at right angles to its surface is examined in 

 Canada balsam with a power of one hundred linear the 

 secondary system of external defensive spicula are 



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