PLATE LXXIV. 215 



seated portions of the sponge there appears numerous 

 long fasciculi of spicula closely resembling those of the 

 primary ones of the dermal system, and the skeleton 

 reticulations are modified accordingly, assuming a 

 degree of regularity in the deeply- seated parts that is 

 not observable in those immediately beneath the 

 dermal tissues ; but the areas of the skeleton do not 

 present the same square or rhomboidal forms that are 

 so strikingly characteristic of the dermal membrane. 



The characters which I have thus described are the 

 essential specific ones of the sponge. The spicula are 

 of the same form in all parts of the sponge, and are 

 very similar to those of H. glabra, caduca, inconspicua, 

 incerta, and coalita. Compared with those of the first- 

 named species they are exactly similar in size and 

 form. In caduca and coalita the forms are the same 

 as in H. ambigua, but the length of the latter is as 

 6 to 4 in the other two. In H. inconspicua and incerta 

 they are of the same form, but only half the length of 

 those of H. ambigua. 



Since the above description was written I have 

 received two other specimens of the species for exami- 

 nation. They were obtained by the Rev. A. M. Norman 

 at Portaferry, Strangford Lough. They vary very 

 much in form from the type-specimen. The largest 

 one covers and closely embraces the stems of a slender 

 fucus, which it binds together for the length of rather 

 more than four inches in the shape of a compressed 

 columnar mass rather exceeding three fourths of an 

 inch at its greatest breadth, and following out the 

 branches of the Fucus in several places in the form of 

 small branches two or three lines in diameter, so that 

 its external characters are widely different to those of 

 the type- specimen. The second specimen is very 

 similar in character to the larger one, but it does not 

 exceed an inch in height. The structural characters 

 agree in every respect with those of the type-specimen. 

 The colour in the dried specimens is dirty white or 

 cream colour. 



